Anisotropic turbulence in weakly stratified rotating magnetoconvection
Giesecke, A
2010-01-01
Numerical simulations of the 3D MHD-equations that describe rotating magnetoconvection in a Cartesian box have been performed using the code NIRVANA. The characteristics of averaged quantities like the turbulence intensity and the turbulent heat flux that are caused by the combined action of the small-scale fluctuations are computed. The correlation length of the turbulence significantly depends on the strength and orientation of the magnetic field and the anisotropic behavior of the turbulence intensity induced by Coriolis and Lorentz force is considerably more pronounced for faster rotation. The development of isotropic behavior on the small scales -- as it is observed in pure rotating convection -- vanishes even for a weak magnetic field which results in a turbulent flow that is dominated by the vertical component. In the presence of a horizontal magnetic field the vertical turbulent heat flux slightly increases with increasing field strength, so that cooling of the rotating system is facilitated. Horizont...
Topological Structures in Rotating Stratified Flows
Redondo, J. M.; Carrillo, A.; Perez, E.
2003-04-01
Detailled 2D Particle traking and PIV visualizations performed on a series of large scale laboratory experiments at the Coriolis Platform of the SINTEF in Trondheim have revealed several resonances which scale on the Strouhal, the Rossby and the Richardson numbers. More than 100 experiments spanned a wide range of Rossby Deformation Radii and the topological structures (Parabolic /Eliptic /Hyperbolic) of the quasi-balanced stratified-rotating flows were studied when stirring (akin to coastal mixing) occured at a side of the tank. The strong asymetry favored by the total vorticity produces a wealth of mixing patterns.
Weakly nonlinear simulation of planar stratified flows
Energy Technology Data Exchange (ETDEWEB)
King, Michael R. [Department of Chemical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); McCready, Mark J. [Department of Chemical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States)
2000-01-01
The interfacial behavior of two-fluid, planar flows is studied by numerical integration of weakly-nonlinear amplitude equations derived via eigenfunction expansion of the governing equations. This study extends the range of classic Stuart-Landau theories by the inclusion of a spectrum of modes allowing all possible quadratic and cubic interactions. Results are obtained for four cases where linear and Stuart-Landau theories do not give a complete description; gas-liquid and oil-water pressure driven flow, matched-density liquid-liquid Couette flow, and the region of gas-liquid flow near resonance that switches from supercritical to subcritical. It is found that integration of amplitude equations gives better qualitative and quantitative agreement with experiments than Stuart-Landau theory. Further, the distinctively different behaviors of these systems can be understood in terms of the spectrum of nonlinear coefficients. In gas-liquid channel flow a low wave number wave is destabilized through quadratic interaction with the mean flow mode. For liquid-liquid Poiseuille flow, a low wave number wave is destabilized through cubic interactions with higher modes. For depth and viscosity ratios where liquid-liquid Couette flow is unstable to long waves and for which the growth rates are not too large, simulation results predict that the waves grow to a statistically steady state where there is no preferred wave number. Stabilization is provided by an apparently self-similar cascade of energy to higher modes that are linearly stable, explaining why no visible waves occur in experiments done in this region. While Stuart-Landau theory provides no prediction of wave amplitude above criticality for subcritical cases, simulations show that wave saturation at small amplitude is possible and suggests that subcritical predictions may not mean that steady waves do not exist. (c) 2000 American Institute of Physics.
Effects of rotation on turbulent buoyant plumes in stratified environments
National Research Council Canada - National Science Library
Fabregat Tomàs, Alexandre; Poje, Andrew C; Özgökmen, Tamay M; Dewar, William K
2016-01-01
We numerically investigate the effects of rotation on the turbulent dynamics of thermally driven buoyant plumes in stratified environments at the large Rossby numbers characteristic of deep oceanic releases...
Magnetorotational instability in stratified, weakly ionised accretion discs
Salmeron, Roberto Aureliano; Salmeron, Raquel; Wardle, Mark
2003-01-01
We present a linear analysis of the vertical structure and growth of the magnetorotational instability in stratified, weakly ionised accretion discs, such as protostellar and quiescent dwarf novae systems. The method includes the effects of the magnetic coupling, the conductivity regime of the fluid and the strength of the magnetic field, which is initially vertical. The conductivity is treated as a tensor and assumed constant with height. We obtained solutions for the structure and growth rate of global unstable modes for different conductivity regimes, strengths of the initial magnetic field and coupling between ionised and neutral components of the fluid. The envelopes of short-wavelenght perturbations are determined by the action of competing local growth rates at different heights, driven by the vertical stratification of the disc. Ambipolar diffusion perturbations peak consistently higher above the midplane than modes including Hall conductivity. For weak coupling, perturbations including the Hall effec...
The Universal Aspect Ratio of Vortices in Rotating Stratifi?ed Flows: Experiments and Observations
Aubert, Oriane; Gal, Patrice Le; Marcus, Philip S
2012-01-01
We validate a new law for the aspect ratio $\\alpha = H/L$ of vortices in a rotating, stratified flow, where $H$ and $L$ are the vertical half-height and horizontal length scale of the vortices. The aspect ratio depends not only on the Coriolis parameter f and buoyancy (or Brunt-Vaisala) frequency $\\bar{N}$ of the background flow, but also on the buoyancy frequency $N_c$ within the vortex and on the Rossby number $Ro$ of the vortex such that $\\alpha = f \\sqrt{[Ro (1 + Ro)/(N_c^2- \\bar{N}^2)]}$. This law for $\\alpha$ is obeyed precisely by the exact equilibrium solution of the inviscid Boussinesq equations that we show to be a useful model of our laboratory vortices. The law is valid for both cyclones and anticyclones. Our anticyclones are generated by injecting fluid into a rotating tank filled with linearly-stratified salt water. The vortices are far from the top and bottom boundaries of the tank, so there is no Ekman circulation. In one set of experiments, the vortices viscously decay, but as they do, they c...
Destabilization of free convection by weak rotation
Gelfgat, Alexander
2011-01-01
This study offers an explanation of a recently observed effect of destabilization of free convective flows by weak rotation. After studying several models where flows are driven by a simultaneous action of convection and rotation, it is concluded that the destabilization is observed in the cases where centrifugal force acts against main convective circulation. At relatively low Prandtl numbers this counter action can split the main vortex into two counter rotating vortices, where the interaction leads to instability. At larger Prandtl numbers, the counter action of the centrifugal force steepens an unstable thermal stratification, which triggers Rayleigh-B\\'enard instability mechanism. Both cases can be enhanced by advection of azimuthal velocity disturbances towards the axis, where they grow and excite perturbations of the radial velocity. The effect was studied considering a combined convective/rotating flow in a cylinder with a rotating lid and a parabolic temperature profile at the sidewall. Next, explana...
The dynamics of small inertial particles in weakly stratified turbulence
van Aartrijk, M.; Clercx, H.J.H.
We present an overview of a numerical study on the small-scale dynamics and the large-scale dispersion of small inertial particles in stably stratified turbulence. Three types of particles are examined: fluid particles, light inertial particles (with particle-to-fluid density ratio 1Ͽp/Ͽf25) and
Numerical Simulation of Wakes in a Weakly Stratified Fluid
Rottman, James W; Innis, George E; O'Shea, Thomas T; Novikov, Evgeny
2014-01-01
This paper describes some preliminary numerical studies using large eddy simulation of full-scale submarine wakes. Submarine wakes are a combination of the wake generated by a smooth slender body and a number of superimposed vortex pairs generated by various control surfaces and other body appendages. For this preliminary study, we attempt to gain some insight into the behavior of full-scale submarine wakes by computing separately the evolution the self-propelled wake of a slender body and the motion of a single vortex pair in both a non-stratified and a stratified environment. An important aspect of the simulations is the use of an iterative procedure to relax the initial turbulence field so that turbulent production and dissipation are in balance.
Magnetorotational instability in weakly ionised, stratified accretion discs
Salmeron, Roberto Aureliano; Salmeron, Raquel; Wardle, Mark
2003-01-01
The magnetorotational instability (MRI) (Balbus and Hawley 1991, Hawley and Balbus 1991) transports angular momentum radially outwards in accretion discs through the distortion of the magnetic field lines that connect fluid elements. In protostellar discs, low conductivity is important, especially in the inner regions (Gammie 1996, Wardle 1997). As a result, low k modes are relevant and vertical stratification is a key factor of the analysis. However, most models of the MRI in these environments have adopted either the ambipolar diffusion or resistive approximations and have not simultaneously treated stratification and Hall conductivity. We present here a linear analysis of the MRI, including the Hall effect, in a stratified disc.
Stability characteristics of jets in linearly-stratified, rotating fluids
Chen, Rui-Rong; Boyer, Don L.; Tao, Lijun
A series of laboratory experiments are conducted concerning an azimuthal jet of a linearly stratified rotating fluid in a cylindrical geometry. The jet is characterized by vertical and horizontal shear and the question of the stability of the flow is considered experimentally. The jet is driven by a source-sink method characterized by a volume flow rate of strength Q. BecauseQ has no direct geophysical significance a combined external set of dimensionless parameters is introduced. These include the Rossby, Richardson and Ekman numbers, the jet aspect ratio and two geometrical parameters. A RossbyRo against RichardsonRi number flow regime diagram is presented which shows that the wave mode of the instability generally decreases with increasingRo andRi, for fixedRi andRo, respectively. In accordance with Killworth's (1980) linear stability analysis, the wave mode for smallRi (Ri ⪉ 15) depends principally onRi with the instability being largely a baroclinic one. For largerRi(Ri ⪉ 100), again as predicted by Killworth's theory, the wave mode depends primarily onRo, the instability being a barotropic one. The regime diagram can be used to estimate the wave-length of jet instabilities in the atmosphere and oceans. These estimates suggest that the wave-lengths decrease with increasing jet velocity, decreasing jet width (equivalent to increasing horizontal shear) and increasing vertical shear, other parameters being fixed. An azimuthal topography aligned along the jet has the tendency to stabilize the jet in the sense that the amplitude of the instability is shown to be dramatically smaller in the presence of the topography, other parameters being fixed. The topography also tends to increase the wave-length of the instability. A scaling analysis is advanced, and supporting experimental data presented, relating the external and internal parameters utilized.
Hassanzadeh, Pedram
Large coherent vortices are abundant in geophysical and astrophysical flows. They play significant roles in the Earth's oceans and atmosphere, the atmosphere of gas giants, such as Jupiter, and the protoplanetary disks around forming stars. These vortices are essentially three-dimensional (3D) and baroclinic, and their dynamics are strongly influenced by the rotation and density stratification of their environments. This work focuses on improving our understanding of the physics of 3D baroclinic vortices in rotating and continuously stratified flows using 3D spectral simulations of the Boussinesq equations, as well as simplified mathematical models. The first chapter discusses the big picture and summarizes the results of this work. In Chapter 2, we derive a relationship for the aspect ratio (i.e., vertical half-thickness over horizontal length scale) of steady and slowly-evolving baroclinic vortices in rotating stratified fluids. We show that the aspect ratio is a function of the Brunt-Vaisala frequencies within the vortex and outside the vortex, the Coriolis parameter, and the Rossby number of the vortex. This equation is basically the gradient-wind equation integrated over the vortex, and is significantly different from the previously proposed scaling laws that find the aspect ratio to be only a function of the properties of the background flow, and independent of the dynamics of the vortex. Our relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and non-uniform background density gradient. The relation for the aspect ratio has many consequences for quasi-equilibrium vortices in rotating stratified flows. For example, cyclones must have interiors more stratified than the background flow (i.e., super-stratified), and weak anticyclones must have interiors less stratified than the background (i.e., sub-stratified). In addition, this equation is useful to
The Universal Aspect Ratio of Vortices in Rotating Stratified Flows: Theory and Simulation
Hassanzadeh, Pedram; Gal, Patrice Le
2012-01-01
We derive a relationship for the vortex aspect ratio $\\alpha$ (vertical half-thickness over horizontal length scale) for steady and slowly evolving vortices in rotating stratified fluids, as a function of the Brunt-Vaisala frequencies within the vortex $N_c$ and in the background fluid outside the vortex $\\bar{N}$, the Coriolis parameter $f$, and the Rossby number $Ro$ of the vortex: $\\alpha^2 = Ro(1+Ro) f^2/(N_c^2-\\bar{N}^2)$. This relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and the background density gradient need not be uniform. Our relation for $\\alpha$ has many consequences for equilibrium vortices in rotating stratified flows. For example, cyclones must have $N_c^2 > \\bar{N}^2$; weak anticyclones (with $|Ro| \\bar{N}^2$. We verify our relation for $\\alpha$ with numerical simulations of the three-dimensional Boussinesq equations for a wide variety of vortices, including: vortices that are i...
Renormalization Group Analysis of Weakly Rotating Turbulent Flows
Institute of Scientific and Technical Information of China (English)
王晓宏; 周全
2011-01-01
Dynamic renormalization group (RNG) analysis is applied to the investigation of the behavior of the infrared limits of weakly rotating turbulence. For turbulent How subject to weak rotation, the anisotropic part in the renormalized propagation is considered to be a perturbation of the isotropic part. Then, with a low-order approximation, the coarsening procedure of RNG transformation is performed. After implementing the coarsening and rescaling procedures, the RNG analysis suggests that the spherically averaged energy spectrum has the scaling behavior E(k) ∝ k11/5 for weakly rotating turbulence. It is also shown that the Coriolis force will disturb the stability of the Kolmogorov -5/3 energy spectrum and will change the scaling behavior even in the case of weak rotation.%Dynamic renormalization group(RNG)analysis is applied to the investigation of the behavior of the infrared limits of weakly rotating turbulence.For turbulent flow subject to weak rotation,the anisotropic part in the renormalized propagation is considered to be a perturbation of the isotropic part.Then,with a low-order approximation,the coarsening procedure of RNG transformation is performed.After implementing the coarsening and rescaling procedures,the RNG analysis suggests that the spherically averaged energy spectrum has the scaling behavior E(k)∝ k-11/5 for weakly rotating turbulence.It is also shown that the Coriolis force will disturb the stability of the Kolmogorov-5/3 energy spectrum and will change the scaling behavior even in the case of weak rotation.
Helicity, geostrophic balance and mixing in rotating stratified turbulence: a multi-scale problem
Pouquet, A.; Marino, R.; Mininni, P.; Rorai, C.; Rosenberg, D. L.
2012-12-01
Helicity, geostrophic balance and mixing in rotating stratified turbulence: a multi-scale problem A. Pouquet, R. Marino, P. D. Mininni, C. Rorai & D. Rosenberg, NCAR Interactions between winds and waves have important roles in planetary and oceanic boundary layers, affecting momentum, heat and CO2 transport. Within the Abyssal Southern Ocean at Mid latitude, this may result in a mixed layer which is too shallow in climate models thereby affecting the overall evolution because of poor handling of wave breaking as in Kelvin-Helmoltz instabilities: gravity waves couple nonlinearly on slow time scales and undergo steepening through resonant interactions, or due to the presence of shear. In the oceans, sub-mesoscale frontogenesis and significant departure from quasi-geostrophy can be seen as turbulence intensifies. The ensuing anomalous vertical dispersion may not be simply modeled by a random walk, due to intermittent structures, wave propagation and to their interactions. Conversely, the energy and seeds required for such intermittent events to occur, say in the stable planetary boundary layer, may come from the wave field that is perturbed, or from winds and the effect of topography. Under the assumption of stationarity, weak nonlinearities, dissipation and forcing, one obtains large-scale geostrophic balance linking pressure gradient, gravity and Coriolis force. The role of helicity (velocity-vorticity correlations) has not received as much attention, outside the realm of astrophysics when considering the growth of large-scale magnetic fields. However, it is measured routinely in the atmosphere in order to gauge the likelihood of supercell convective storms to strengthen, and it may be a factor to consider in the formation of hurricanes. In this context, we examine the transition from a wave-dominated regime to an isotropic small-scale turbulent one in rotating flows with helical forcing. Using a direct numerical simulation (DNS) on a 3072^3 grid with Rossby and
Investigations of non-hydrostatic, stably stratified and rapidly rotating flows
Nieves, David; Juilen, Keith; Weiss, Jeffrey B
2016-01-01
We present an investigation of rapidly rotating (small Rossby number $Ro\\ll 1$) and stratified turbulence where the stratification strength is varied from weak (large Froude number $Fr\\gg1$) to strong ($Fr\\ll1$). The investigation is set in the context of a reduced model derived from the Boussinesq equations that efficiently retains anisotropic inertia-gravity waves with order-one frequencies and highlights a regime of wave-eddy interactions. Numerical simulations of the reduced model are performed where energy is injected by a stochastic forcing of vertical velocity, which forces wave modes only. The simulations reveal two regimes characterized by the presence of well-formed, persistent and thin turbulent layers of locally-weakened stratification at small Froude numbers, and by the absence of layers at large Froude numbers. Both regimes are characterized by a large-scale barotropic dipole enclosed by small-scale turbulence. When the Reynolds number is not too large a direct cascade of barotropic kinetic ener...
Ultrasmall polarization rotation measurements via weak value amplification
Energy Technology Data Exchange (ETDEWEB)
Lima Bernardo, Bertúlio de, E-mail: bertulio@fisica.ufpb.br; Azevedo, Sérgio; Rosas, Alexandre
2014-06-13
Highlights: • We present a class of weak measurements where the measurer is an angular variable of the system. • Photon-energy qubits are required, which seems to be the first application of this kind of light. • Both weak optical activity and reflection-induced polarization rotation can be amplified. • This protocol can amplify the optical activity signal in nanostructures and biological tissues. - Abstract: We propose a framework to analyze weak measurements based on an angular version of the von Neumann measurement scheme, where the coupling between the system and the meter causes rotation of the measuring variable. We also discuss an experimental application of this theory in which measurements of weak optical activity and reflection-induced polarization rotation could be amplified in nearly two orders of magnitude. It can shed a new light on a great variety of physical chemistry, molecular biology and nanotechnology studies.
Investigations of Reduced Equations for Rotating, Stratified and Non-hydrostatic Flows
Nieves, David J.
boundary conditions. These results imply that any horizontal thermal variation along the boundaries that varies on the scale of the convection has no leading order influence on the interior convection, thus providing insight into geophysical and astrophysical flows where stress-free mechanical boundary conditions are often assumed. The final study presented here contrasts the previous investigations. It presents an investigation of rapidly rotating and stably stratified turbulence where the stratification strength is varied from weak (large Froude number) to strong (small Froude number). The investigation is set in the context of the asymptotically reduced model which efficiently retains anisotropic inertia-gravity waves with order-one frequencies and highlights a regime of wave-eddy interactions. Numerical simulations of the reduced model are performed where energy is injected by a stochastic forcing of vertical velocity. The simulations reveal two regimes: one characterized by the presence of well-formed, persistent and thin turbulent layers of locally-weakened stratification: the other characterized by the absence of layers at large Froude numbers. Both regimes are characterized by a large-scale barotropic dipole in a sea of small-scale turbulence. When the Reynolds number is not too large a direct cascade of barotropic kinetic energy is observed and leads to an equilibration of total energy. We examine net energy exchanges that occur through vortex stretching and vertical buoyancy flux and diagnose the horizontal scales active in these exchanges. We find that baroclinic motions inject energy directly to the largest scales of the barotropic mode governed by the two-dimensional vorticity equation, and implies that the large-scale barotropic dipole is not the end result of an inverse cascade within the two-dimensional barotropic mode. An additional yet brief look into the linear vortical and wave modes is considered.
Deformation and failure of stratified weak roof strata of longwall roadway
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A comprehensive underground monitoring was conducted in a coal mine. The purpose of this research was to clarify the deformation and failure behavior of stratified weak roof strata of longwall roadway in adverse ground conditions. The field investigation incorporating a range of geotechnical instrumentation was conducted over a period of time ever since the formation of opening the site was buried into the goaf of a retreating longwall panel. The roof layer deformation and failure characteristics associated with the three stages of heading development, after development and before extraction, as well as after longwall extraction were identified on the basis of field investigation and analyticai study, the results clearly demonstrated that how the roof deformation and failure progress were strongly related to these three stages of the mining activities mentioned.
Laboratory Studies of the Stratified Rotating Flow Passing over an Isolated Obstacle
Institute of Scientific and Technical Information of China (English)
高守亭; 平凡
2003-01-01
We study the flow of a density-stratified fluid passing over an isolated obstacle, using towing-tank experiments.Our special concern is the response of the flow with different Froude numbers passing over a three-dimensional obstacle. A series of experiments of the stratified rotating flow passing over an isolated obstacle was carried out with the towering-tank controlled by the similarity laws and dynamic non-dimension parameters. These experiments show that the Froude number is a very important parameter, and the lee wave and the eddy structure appear simultaneously under an appropriate conditions. The effect of rotation on the lee wave is mainly to change wave amplitude, particularly to restrain the development of the lee wave and to promote the formation of an eddy.
On the Asymptotic Regimes and the Strongly Stratified Limit of Rotating Boussinesq Equations
Babin, A.; Mahalov, A.; Nicolaenko, B.; Zhou, Y.
1997-01-01
Asymptotic regimes of geophysical dynamics are described for different Burger number limits. Rotating Boussinesq equations are analyzed in the asymptotic limit, of strong stratification in the Burger number of order one situation as well as in the asymptotic regime of strong stratification and weak rotation. It is shown that in both regimes horizontally averaged buoyancy variable is an adiabatic invariant for the full Boussinesq system. Spectral phase shift corrections to the buoyancy time scale associated with vertical shearing of this invariant are deduced. Statistical dephasing effects induced by turbulent processes on inertial-gravity waves are evidenced. The 'split' of the energy transfer of the vortical and the wave components is established in the Craya-Herring cyclic basis. As the Burger number increases from zero to infinity, we demonstrate gradual unfreezing of energy cascades for ageostrophic dynamics. The energy spectrum and the anisotropic spectral eddy viscosity are deduced with an explicit dependence on the anisotropic rotation/stratification time scale which depends on the vertical aspect ratio parameter. Intermediate asymptotic regime corresponding to strong stratification and weak rotation is analyzed where the effects of weak rotation are accounted for by an asymptotic expansion with full control (saturation) of vertical shearing. The regularizing effect of weak rotation differs from regularizations based on vertical viscosity. Two scalar prognostic equations for ageostrophic components (divergent velocity potential and geostrophic departure ) are obtained.
van Haren, H.
2015-01-01
The character of turbulent overturns in a weakly stratified deep-sea is investigated in some detail using 144 high-resolution temperature sensors at 0.7 m intervals, starting 5 m above the bottom. A 9-day, 1 Hz sampled record from the 912 m depth flat-bottom (<0.5% bottom-slope) mooring site in the
van Haren, H.
2015-01-01
The character of turbulent overturns in a weakly stratified deep-sea is investigated in some detail using 144 high-resolution temperature sensors at 0.7 m intervals, starting 5 m above the bottom. A 9-day, 1 Hz sampled record from the 912 m depth flat-bottom (<0.5% bottom-slope) mooring site in the
Rotating Gaussian wave packets in weak external potentials
Goussev, Arseni
2017-07-01
We address the time evolution of two- and three-dimensional nonrelativistic Gaussian wave packets in the presence of a weak external potential of arbitrary functional form. The focus of our study is the phenomenon of rotation of a Gaussian wave packet around its center of mass, as quantified by mean angular momentum computed relative to the wave-packet center. Using a semiclassical approximation of the eikonal type, we derive an explicit formula for a time-dependent change of mean angular momentum of a wave packet induced by its interaction with a weak external potential. As an example, we apply our analytical approach to the scenario of a two-dimensional quantum particle crossing a tilted ridge potential barrier. In particular, we demonstrate that the initial orientation of the particle wave packet determines the sense of its rotation, and report a good agreement between analytical and numerical results.
Quantifying shoulder rotation weakness in patients with shoulder impingement.
Tyler, Timothy F; Nahow, Rachael C; Nicholas, Stephen J; McHugh, Malachy P
2005-01-01
The purpose of this study was to determine whether strength deficits could be detected in individuals with and without shoulder impingement, all of whom had normal shoulder strength bilaterally according to grading of manual muscle testing. Strength of the internal rotators and external rotators was tested isokinetically at 60 degrees /s and 180 degrees /s, as well as manually with a handheld dynamometer (HHD) in 17 patients and 22 control subjects. Testing was performed with the shoulder positioned in the scapular plane and in 90 degrees of shoulder abduction with 90 degrees of elbow flexion (90-90). The peak torque was determined for each movement. The strength deficit between the involved and uninvolved arms (patients) and the dominant and nondominant arms (control subjects) was calculated for each subject. Comparisons were made for the scapular-plane and 90-90 positions between isokinetic and HHD testing. Despite a normal muscle grade, patients had marked weakness (28% deficit, P weakness was not evident with isokinetic testing at the 90-90 position (60 degrees /s and 180 degrees /s, 0% deficit, P = .99). In control subjects, greater internal rotator strength in the dominant compared with the nondominant arm was evident with the HHD at the 90-90 position (11%, P muscle testing can quantify shoulder strength deficits that may not be apparent with isokinetic testing. By using an HHD during shoulder testing, clinicians can identify weakness that may have been presumed normal.
On the lifetime of a pancake anticyclone in a rotating stratified flow
Facchini, Giulio; Le Bars, Michael
2016-11-01
We present an experimental study of the time evolution of an isolated anticyclonic pancake vortex in a laboratory rotating stratified flow. Motivations come from the variety of compact anticyclones observed to form and persist for a strikingly long lifetime in geophysical and astrophysical settings combining rotation and stratification. We generate anticyclones by injecting a small amount of isodense fluid at the center of a rotating tank filled with salty water linearly stratified in density. Our two control parameters are the Coriolis parameter f and the Brunt-Väisälä frequency N. We observe that anticyclones always slowly decay by viscous diffusion, spreading mainly in the horizontal direction irrespective of the initial aspect ratio. This behavior is correctly explained by a linear analytical model in the limit of small Rossby and Ekman numbers, where density and velocity equations reduce to a single equation for the pressure. Direct numerical simulations further confirm the theoretical predictions. Notably, they show that the azimuthal shear stress generates secondary circulations, which advect the density anomaly: this mechanism is responsible for the slow time evolution, rather than the classical viscous dissipation of the azimuthal kinetic energy.
Weak turbulence theory for rotating magnetohydrodynamics and planetary dynamos
Galtier, Sebastien
2014-01-01
A weak turbulence theory is derived for magnetohydrodynamics under rapid rotation and in the presence of a large-scale magnetic field. The angular velocity $\\Omega_0$ is assumed to be uniform and parallel to the constant Alfv\\'en speed ${\\bf b_0}$. Such a system exhibits left and right circularly polarized waves which can be obtained by introducing the magneto-inertial length $d \\equiv b_0/\\Omega_0$. In the large-scale limit ($kd \\to 0$; $k$ being the wave number), the left- and right-handed waves tend respectively to the inertial and magnetostrophic waves whereas in the small-scale limit ($kd \\to + \\infty$) pure Alfv\\'en waves are recovered. By using a complex helicity decomposition, the asymptotic weak turbulence equations are derived which describe the long-time behavior of weakly dispersive interacting waves {\\it via} three-wave interaction processes. It is shown that the nonlinear dynamics is mainly anisotropic with a stronger transfer perpendicular ($\\perp$) than parallel ($\\parallel$) to the rotating a...
Waves and vortices in the inverse cascade regime of stratified turbulence with or without rotation
Herbert, Corentin; Rosenberg, Duane; Pouquet, Annick
2015-01-01
We study the partition of energy between waves and vortices in stratified turbulence, with or without rotation, for a variety of parameters, focusing on the behavior of the waves and vortices in the inverse cascade of energy towards the large scales. To this end, we use direct numerical simulations in a cubic box at a Reynolds number Re=1000, with the ratio between the Brunt-V\\"ais\\"al\\"a frequency N and the inertial frequency f varying from 1/4 to 20, together with a purely stratified run. The Froude number, measuring the strength of the stratification, varies within the range 0.02 < Fr < 0.32. We find that the inverse cascade is dominated by the slow quasi-geostrophic modes. Their energy spectra and fluxes exhibit characteristics of an inverse cascade, even though their energy is not conserved. Surprisingly, the slow vortices still dominate when the ratio N/f increases, also in the stratified case, although less and less so. However, when N/f increases, the inverse cascade of the slow modes becomes we...
Are vortices in rotating superfluids breaking the Weak Equivalence Principle?
de Matos, Clovis Jacinto
2009-01-01
Due to the breaking of gauge symmetry in rotating superfluid Helium, the inertial mass of a vortex diverges with the vortex size. The vortex inertial mass is thus much higher than the classical inertial mass of the vortex core. An equal increase of the vortex gravitational mass is questioned. The possibility that the vortices in a rotating superfluid could break the weak equivalence principle in relation with a variable speed of light in the superfluid vacuum is debated. Experiments to test this possibility are investigated on the bases that superfluid Helium vortices would not fall, under the single influence of a uniform gravitational field, at the same rate as the rest of the superfluid Helium mass.
Geostrophic balance and the emergence of helicity in rotating stratified turbulence
Marino, Raffaele; Rosenberg, Duane; Pouquet, Annick
2012-01-01
We perform numerical simulations of decaying rotating stratified turbulence and show, in the Boussinesq framework, that helicity (velocity-vorticity correlation), as observed in super-cell storms and hurricanes, is spontaneously created due to geostrophic balance common to large-scale atmospheric and oceanic flows. Helicity emerges from the joint action of eddies and of inertial and gravity waves of respective frequencies $f$ and $N$, and it occurs when the waves are sufficiently strong. For $N/f < 3$ the amount of helicity produced is correctly predicted by a linear balance equation. Outside this regime, and up to the highest Reynolds number obtained in this study, namely $Re\\approx 10000$, helicity production is found to be persistent for $N/f$ as large as $\\approx 17$ and for $ReFr^2$ and $ReRo^2 $ as large as $\\approx 100, \\approx 24000 $.
Wang, Junfeng; Miesch, Mark S
2015-01-01
We present a novel and powerful Compressible High-ORder Unstructured Spectral-difference (CHORUS) code for simulating thermal convection and related fluid dynamics in the interiors of stars and planets. The computational geometries are treated as rotating spherical shells filled with stratified gas. The hydrodynamic equations are discretized by a robust and efficient high-order Spectral Difference Method (SDM) on unstructured meshes. The computational stencil of the spectral difference method is compact and advantageous for parallel processing. CHORUS demonstrates excellent parallel performance for all test cases reported in this paper, scaling up to 12,000 cores on the Yellowstone High-Performance Computing cluster at NCAR. The code is verified by defining two benchmark cases for global convection in Jupiter and the Sun. CHORUS results are compared with results from the ASH code and good agreement is found. The CHORUS code creates new opportunities for simulating such varied phenomena as multi-scale solar co...
Stability of 3D Gaussian vortices in rotating stratified Boussinesq flows: Linear analysis
Mahdinia, Mani; Jiang, Chung-Hsiang
2016-01-01
The linear stability of three-dimensional (3D) vortices in rotating, stratified flows has been studied by analyzing the non-hydrostatic inviscid Boussinesq equations. We have focused on a widely-used model of geophysical and astrophysical vortices, which assumes an axisymmetric Gaussian structure for pressure anomalies in the horizontal and vertical directions. For a range of Rossby number ($-0.5 < Ro < 0.5$) and Burger number ($0.02 < Bu < 2.3$) relevant to observed long-lived vortices, the growth rate and spatial structure of the most unstable eigenmodes have been numerically calculated and presented as a function of $Ro-Bu$. We have found neutrally-stable vortices only over a small region of the $Ro-Bu$ parameter space: cyclones with $Ro \\sim 0.02-0.05$ and $Bu \\sim 0.85-0.95$. However, we have also found that anticyclones in general have slower growth rates compared to cyclones. In particular, growth rate of the most unstable eigenmode for anticyclones in a large region of the parameter space ...
Wang, Dayang; Adams, E. Eric
2016-06-01
We present an experimental study of particle plumes in ambient stratification and a mild current. In an inverted framework, the results describe the fate of oil droplets released from a deep ocean blowout. A continuous stream of dense glass beads was released from a carriage towed in a salt-stratified tank. Nondimensional particle slip velocity UN ranged from 0.1 to 1.9, and particles with UN ≤ 0.5 were observed to enter the intrusion layer. The spatial distributions of beads, collected on a bottom sled towed with the source, present a Gaussian distribution in the transverse direction and a skewed distribution in the along-current direction. Dimensions of the distributions increase with decreasing UN. The spreading relations can be used as input to far-field models describing subsequent transport of particles or, in an inverted framework, oil droplets. The average particle settling velocity, Uave, was found to exceed the individual particle slip velocity, Us, which is attributed to the initial plume velocity near the point of release. Additionally, smaller particles exhibit a "group" or "secondary plume" effect as they exit the intrusion as a swarm. The secondary effect becomes more prominent as UN decreases, and might help explain observations from the 2000 Deep Spill field experiment where oil was found to surface more rapidly than predicted based on Us. An analytical model predicting the particle deposition patterns was validated against experimental measurements, and used to estimate near-field oil transport under the Deepwater Horizon spill conditions, with/without chemical dispersants.
Vincze, Miklos; Harlander, Uwe; Gal, Patrice Le
2016-01-01
A water-filled differentially heated rotating annulus with initially prepared stable vertical salinity profiles is studied in the laboratory. Based on two-dimensional horizontal particle image velocimetry (PIV) data, and infrared camera visualizations, we describe the appearance and the characteristics of the baroclinic instability in this original configuration. First, we show that when the salinity profile is linear and confined between two non stratified layers at top and bottom, only two separate shallow fluid layers can be destabilized. These unstable layers appear nearby the top and the bottom of the tank with a stratified motionless zone between them. This laboratory arrangement is thus particularly interesting to model geophysical or astrophysical situations where stratified regions are often juxtaposed to convective ones. Then, for more general but stable initial density profiles, statistical measures are introduced to quantify the extent of the baroclinic instability at given depths and to analyze t...
Rotation of galaxies as a signature of cosmic strings in weak lensing surveys
Thomas, Daniel B.; Contaldi, Carlo R.; Magueijo, Joao
2009-01-01
Vector perturbations sourced by topological defects can generate rotations in the lensing of background galaxies. This is a potential smoking gun for the existence of defects since rotation generates a curl-like component in the weak lensing signal which is not generated by standard density perturbations at linear order. This rotation signal is calculated as generated by cosmic strings. Future large scale weak lensing surveys should be able to detect this signal even for string tensions an or...
Energy Technology Data Exchange (ETDEWEB)
Sosenko, P.; Pierre, Th. [Universite Marseille, Lab. PIIM - UMR6633 CNRS, Centre Saint Jerome, 13 - Marseille (France); Zagorodny, A. [Nancy-1 Univ. Henri Poincare, Lab. de Physique des Milieux Ionises (LPMIA, UPRES-A), Nancy 54 (France); International Centre of Physics, Kyiv (Ukraine)
2004-07-01
The linear and non-linear properties of global low-frequency oscillations in cylindrical weakly ionized magnetized plasmas are investigated analytically for the conditions of equilibrium plasma rotation. The theoretical results are compared with the experimental observations of rotating plasmas in laboratory devices, such as Mistral and Mirabelle in France, and KIWI in Germany. (authors)
Effects of background rotation on a towed-sphere wake in a stably stratified fluid
Energy Technology Data Exchange (ETDEWEB)
Spedding, G.R. [Southern California Univ., Los Angeles (United States). Dept. of Aerospace and Mechanical Engineering; Fincham, A.M. [Laboratoire Coriolis, Grenoble (France). Inst. de Mechanique
1999-12-01
The wake of a towed sphere in a stable background density gradient can be considered a convenient model problem for studying the emergence and longevity of the coherent patches of alternate-signed vertical vorticity that comprise the late wake. Wake anticyclones, with sense of rotation opposite to the background rotation, were spread out over a large area, and were less strongly peaked than their cyclonic counterparts, with the magnitude of the asymmetry depending on f/N. The observed asymmetries are consistent with existing data on homogenous wake flows with rotation.
Rotation of galaxies as a signature of cosmic strings in weak lensing surveys
Thomas, Daniel B; Magueijo, Joao
2009-01-01
Vector perturbations sourced by topological defects can generate rotations in the lensing of background galaxies. This is a potential smoking gun for the existence of defects since rotation generates a curl-like component in the weak lensing signal which is not generated by standard density perturbations at linear order. This rotation signal is calculated as generated by cosmic strings. Future large scale weak lensing surveys should be able to detect this signal even for string tensions an order of magnitude lower than current constraints.
Vincze, Miklos; Borcia, Ion; Harlander, Uwe; Le Gal, Patrice
2016-12-01
A water-filled differentially heated rotating annulus with initially prepared stable vertical salinity profiles is studied in the laboratory. Based on two-dimensional horizontal particle image velocimetry data and infrared camera visualizations, we describe the appearance and the characteristics of the baroclinic instability in this original configuration. First, we show that when the salinity profile is linear and confined between two non-stratified layers at top and bottom, only two separate shallow fluid layers can be destabilized. These unstable layers appear nearby the top and the bottom of the tank with a stratified motionless zone between them. This laboratory arrangement is thus particularly interesting to model geophysical or astrophysical situations where stratified regions are often juxtaposed to convective ones. Then, for more general but stable initial density profiles, statistical measures are introduced to quantify the extent of the baroclinic instability at given depths and to analyze the connections between this depth-dependence and the vertical salinity profiles. We find that, although the presence of stable stratification generally hinders full-depth overturning, double-diffusive convection can lead to development of multicellular sideways convection in shallow layers and subsequently to a multilayered baroclinic instability. Therefore we conclude that by decreasing the characteristic vertical scale of the flow, stratification may even enhance the formation of cyclonic and anticyclonic eddies (and thus, mixing) in a local sense.
Dikpati, Mausumi
2013-01-01
Meridional circulation in stellar convection zones is not generally well observed, but may be critical for MHD dynamos. Coriolis forces from differential rotation (DR) play a large role in determining what the meridional circulation is. Here we consider whether a stellar DR that is constant on cylinders concentric with the rotation axis can drive a meridional circulation.Conventional wisdom says that it can not. Using two related forms of governing equations that respectively estimate the longitudinal components of the curl of meridional mass flux and the vorticity, we show that such DR will drive a meridional flow. This is because to satisfy anelastic mass conservation, non-spherically symmetric pressure contours must be present for all DRs, not just ones that depart from constancy on cylinders concentric with the rotation axis. Therefore the fluid is always baroclinic if DR is present, because, in anelastic systems, the perturbation pressure must satisfy a Poisson type equation, as well as an equation of st...
Directory of Open Access Journals (Sweden)
Tasawar Hayat
Full Text Available This paper investigates the unsteady MHD flow of viscous fluid between two parallel rotating disks. Fluid fills the porous space. Energy equation has been constructed by taking Joule heating, thermal stratification and radiation effects into consideration. We convert system of partial differential equations into system of highly nonlinear ordinary differential equations after employing the suitable transformations. Convergent series solutions are obtained. Behavior of different involved parameters on velocity and temperature profiles is examined graphically. Numerical values of skin friction coefficient and Nusselt number are computed and inspected. It is found that tangential velocity profile is increasing function of rotational parameter. Fluid temperature reduces for increasing values of thermal stratification parameter. At upper disk heat transfer rate enhances for larger values of Eckert and Prandtl numbers.
Hayat, Tasawar; Qayyum, Sumaira; Imtiaz, Maria; Alsaedi, Ahmed
2016-01-01
This paper investigates the unsteady MHD flow of viscous fluid between two parallel rotating disks. Fluid fills the porous space. Energy equation has been constructed by taking Joule heating, thermal stratification and radiation effects into consideration. We convert system of partial differential equations into system of highly nonlinear ordinary differential equations after employing the suitable transformations. Convergent series solutions are obtained. Behavior of different involved parameters on velocity and temperature profiles is examined graphically. Numerical values of skin friction coefficient and Nusselt number are computed and inspected. It is found that tangential velocity profile is increasing function of rotational parameter. Fluid temperature reduces for increasing values of thermal stratification parameter. At upper disk heat transfer rate enhances for larger values of Eckert and Prandtl numbers.
Marino, Raffaele; Herbert, Corentin; Pouquet, Annick
2015-01-01
The interplay between waves and eddies in stably stratified rotating flows is investigated by means of world-class direct numerical simulations using up to $3072^3$ grid points. Strikingly, we find that the shift from vortex to wave dominated dynamics occurs at a wavenumber $k_R$ which does not depend on Reynolds number, suggesting that partition of energy between wave and vortical modes is not sensitive to the development of turbulence at the smaller scales. We also show that $k_R$ is comparable to the wavenumber at which exchanges between kinetic and potential modes stabilize at close to equipartition, emphasizing the role of potential energy, as conjectured in the atmosphere and the oceans. Moreover, $k_R$ varies as the inverse of the Froude number as explained by the scaling prediction proposed, consistent with recent observations and modeling of the Mesosphere-Lower Thermosphere and of the ocean.
Restricted Equilibrium and the Energy Cascade in Rotating and Stratified Flows
Herbert, Corentin; Marino, Raffaele
2014-01-01
Most of the turbulent flows appearing in nature (e.g. geophysical and astrophysical flows) are subjected to strong rotation and stratification. These effects break the symmetries of classical, homogenous isotropic turbulence. In doing so, they introduce a natural decomposition of phase space in terms of wave modes and potential vorticity modes. The appearance of a new time scale associated to the propagation of waves, in addition to the eddy turnover time, increases the complexity of the energy transfers between the various scales; nonlinearly interacting waves may dominate at some scales while balanced motion may prevail at others. In the end, it is difficult to predict \\emph{a priori} if the energy cascades downscale as in homogeneous isotropic turbulence, upscale as expected from balanced dynamics, or follows yet another phenomenology. In this paper, we suggest a theoretical approach based on equilibrium statistical mechanics for the ideal system, inspired from the restricted partition function formalism i...
Linear Instabilities Driven by Differential Rotation in Very Weakly Magnetized Plasmas
Quataert, Eliot; Spitkovsky, Anatoly
2014-01-01
We study the linear stability of weakly magnetized differentially rotating plasmas in both collisionless kinetic theory and Braginskii's theory of collisional, magnetized plasmas. We focus on the very weakly magnetized limit that is important for understanding how astrophysical magnetic fields originate and are amplified at high redshift. We show that the single instability of fluid theory - the magnetorotational instability mediated by magnetic tension - is replaced by two distinct instabilities, one associated with ions and one with electrons. Each of these has a different way of tapping into the free energy of differential rotation. The ion instability is driven by viscous transport of momentum across magnetic field lines due to a finite ion cyclotron frequency (gyroviscosity); the fastest growing modes have wavelengths significantly longer than MHD and Hall MHD predictions. The electron instability is a whistler mode driven unstable by the temperature anisotropy generated by differential rotation; the gro...
Energy Technology Data Exchange (ETDEWEB)
Spurr, Robert [RT Solutions Inc., 9 Channing Street, Cambridge, MA 02138 (United States)], E-mail: rtsolutions@verizon.net; Haan, Johan de; Oss, Roeland van [KNMI, de Bilt (Netherlands); Vasilkov, Alexander [SSAI, Lanham, MD (United States)
2008-02-15
Rotational Raman scattering (RRS) by air molecules in the Earth's atmosphere is predominantly responsible for the Ring effect: Fraunhofer and absorption-feature filling-in observed in UV/visible backscatter spectra. Accurate determination of RRS effects requires detailed radiative transfer (RT) treatment. In this paper, we demonstrate that the discrete-ordinate RT equations may be solved analytically in a multi-layer multiple scattering atmosphere in the presence of RRS treated as a first-order perturbation. Based on this solution, we develop a generic pseudo-spherical RT model LIDORT-RRS for the determination of backscatter radiances with RRS included; the model will generate output at arbitrary viewing geometry and optical thickness. Model comparisons with measured RRS filling-in effects from OMI observations show very good agreement. We examine telluric RRS filling-in effects for satellite-view backscatter radiances in a spectral range covering the ozone Huggins absorption bands. The model is also used to investigate calcium H and K Fraunhofer filling-in through cloud layers in the atmosphere.
Galmiche, M.; Sommeria, J.; Verron, J.; Thivolle-Cazat, E.
Due to the difficulty in measuring the ocean properties with accuracy and high reso- lution in space and time, the validation of the data assimilation schemes developped for the use of operational oceanography is not straightforward. We present here an experimental alternative to test the accuracy of data assimilation schemes at the labo- ratory scale. The same method is used as in real-scale operational oceanography, but the oceanic reality is replaced by the velocity field measured in laboratory experiments of simple, oceanic-like flows. Laboratory experiments of vortex instability in a rotating, two-layer fluid are per- formed in the large Coriolis turntable (LEGI, France). The velocity field of the flow is measured using the PIV (Particle Image Velocimetry) technique. The numerical sim- ulation of these flows is performed using the MICOM (Miami Isopycnic Coordinate Model, Bleck and Boudra 1986) numerical code, the experimental data being assimi- lated using the SEEK (Singular Evolutive Extended Kalman Filter, Pham et al. 1998) version of the Kalman Filter. Order reduction is operated thanks to an EOF (Empirical Orthogonal Functions) analysis. We can then analyze how data assimilation drives the numerical simulation closer to the reality, as a function of a certain number of param- eters (assimilation frequency, space resolution, choice of EOF basis, parameterization of model errors,...) References Bleck, R. and Boudra, D. 1986. Wind driven spin-up in eddy-resolving ocean models formulated in isopycnic ans isobaric coordinates. JGR 91, 7611-7621. Pham, D., Verron, J. and Roubaud, M. 1998. A Singular Evolutive Extended Kalman Filter for data assimilation in oceanography. JMS 16 (3-4), 323-340.
Rosenberg, D; Marino, R; Mininni, P D
2014-01-01
We report results on rotating stratified turbulence in the absence of forcing, with large-scale isotropic initial conditions, using direct numerical simulations computed on grids of up to 4096^3 points. The Reynolds and Froude numbers are respectively equal to Re=5.4 x 10^4 and Fr=0.0242. The ratio of the Brunt-V\\"ais\\"al\\"a to the inertial wave frequency, N/f, is taken to be equal to 4.95, a choice appropriate to model the dynamics of the southern abyssal ocean at mid latitudes. This gives a global buoyancy Reynolds number R_B=ReFr^2=32, a value sufficient for some isotropy to be recovered in the small scales beyond the Ozmidov scale, but still moderate enough that the intermediate scales where waves are prevalent are well resolved. We concentrate on the large-scale dynamics, for which we find a spectrum compatible with the Bolgiano-Obukhov scaling, and confirm that the Froude number based on a typical vertical length scale is of order unity, with strong gradients in the vertical. Two characteristic scales e...
Directory of Open Access Journals (Sweden)
Cha'o-Kuang Chen
2009-01-01
Full Text Available The main object of this paper is to study the weakly nonlinear hydrodynamic stability of the thin Newtonian fluid flowing on a rotating circular disk. A long-wave perturbation method is used to derive the nonlinear evolution equation for the film flow. The linear behaviors of the spreading wave are investigated by normal mode approach, and its weakly nonlinear behaviors are explored by the method of multiple scales. The Ginzburg-Landau equation is determined to discuss the necessary condition for the existence of such flow pattern. The results indicate that the superctitical instability region increases, and the subcritical stability region decreases with the increase of the rotation number or the radius of circular disk. It is found that the rotation number and the radius of circular disk not only play the significant roles in destabilizing the flow in the linear stability analysis but also shrink the area of supercritical stability region at high Reynolds number in the weakly nonlinear stability analysis.
Four-Hair Relations for Differentially Rotating Neutron Stars in the Weak-Field Limit
Bretz, Joseph; Yunes, Nicolas
2015-01-01
The opportunity to study physics at supra-nuclear densities through X-ray observations of neutron stars has led to in-depth investigations of certain approximately universal relations that can remove degeneracies in pulse profile models. One such set of relations determines all of the multipole moments of a neutron star just from the first three (the mass monopole, the current dipole and the mass quadrupole moment) approximately independently of the equation of state. These three-hair relations were found to hold in neutron stars that rotate rigidly, as is the case in old pulsars, but neutron stars can also rotate differentially, as is the case for proto-neutron stars and hypermassive transient remnants of binary mergers. We here extend the three-hair relations to differentially rotating stars for the first time with a generic rotation law using two approximations: a weak-field scheme (an expansion in powers of the neutron star compactness) and a perturbative differential rotation scheme (an expansion about r...
Simvastatin reduces fibrosis and protects against muscle weakness after massive rotator cuff tear.
Davis, Max E; Korn, Michael A; Gumucio, Jonathan P; Harning, Julie A; Saripalli, Anjali L; Bedi, Asheesh; Mendias, Christopher L
2015-02-01
Chronic rotator cuff tears are a common source of shoulder pain and disability, and patients with chronic cuff tears often have substantial weakness, fibrosis, inflammation, and fat accumulation. Identifying therapies to prevent the development of these pathologic processes will likely have a positive impact on clinical outcomes. Simvastatin is a drug with demonstrated anti-inflammatory and antifibrotic effects in many tissues but had not previously been studied in the context of rotator cuff tears. We hypothesized that after the induction of a massive supraspinatus tear, simvastatin would protect muscles from a loss of force production and fibrosis. We measured changes in muscle fiber contractility, histology, and biochemical markers of fibrosis and fatty infiltration in rats that received a full-thickness supraspinatus tear and were treated with either carrier alone or simvastatin. Compared with vehicle-treated controls, simvastatin did not have an appreciable effect on muscle fiber size, but treatment did increase muscle fiber specific force by 20%. Simvastatin also reduced collagen accumulation by 50% but did not affect triglyceride content of muscles. Several favorable changes in the expression of genes and other markers of inflammation, fibrosis, and regeneration were also observed. Simvastatin partially protected muscles from the weakness that occurs as a result of chronic rotator cuff tear. Fibrosis was also markedly reduced in simvastatin-treated animals. Whereas further studies are necessary, statin medication could potentially help improve outcomes for patients with rotator cuff tears. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.
Feng, Gang; Evangelisti, Luca; Caminati, Walther; Cacelli, Ivo; Carbonaro, Laura; Prampolini, Giacomo
2013-06-01
Following the investigation of the rotational spectra of three conformers (so-called ``book'', ``prism'' and ``cage'') of the water hexamer, and of some other water oligomers, we report here the rotational spectrum of the tetramer of a freon molecule. The pulse jet Fourier transform microwave (pj-FTMW) spectrum of an isomer of the difluoromethane tetramer has been assigned. This molecular system is made of units of a relatively heavy asymmetric rotor, held together by a network of weak hydrogen bonds. The search of the rotational spectrum has been based on a high-level reference method, the CCSD(T)/CBS protocol. It is interesting to outline that the rotational spectrum of the water tetramer was not observed, probably because the minimum energy structures of this oligomer is effectively nonpolar in its ground states, or because of high energy tunnelling splittings. The rotational spectra of the monomer, dimer, trimer and tetramer of difluoromethane have been assigned in 1952, 1999, 2007, and 2013 (present work), with a decreasing time spacing between the various steps, looking then promising for a continuous and rapid extension of the size limits of molecular systems accessible to MW spectroscopy. C. Pérez, M. T. Muckle, D. P. Zaleski, N. A. Seifert, B. Temelso, G. C. Shields, Z. Kisiel, B. H. Pate, Science {336} (2012) 897. D. R. Lide, Jr., J. Am. Chem. Soc. {74} (1952) 3548. W. Caminati, S. Melandri, P. Moreschini, P. G. Favero, Angew. Chem. Int. Ed. {38} (1999) 2924. S. Blanco, S. Melandri, P. Ottaviani, W. Caminati, J. Am. Chem. Soc. {129} (2007) 2700.
Steiber, Nadia
2016-01-01
Handgrip strength is an important biomarker of healthy ageing and a powerful predictor of future morbidity and mortality both in younger and older populations. Therefore, the measurement of handgrip strength is increasingly used as a simple but efficient screening tool for health vulnerability. This study presents normative reference values for handgrip strength in Germany for use in research and clinical practice. It is the first study to provide normative data across the life course that is stratified by sex, age, and body height. The study used a nationally representative sample of test participants ages 17-90. It was based on pooled data from five waves of the German Socio-Economic Panel (2006-2014) and involved a total of 11,790 persons living in Germany (providing 25,285 observations). Handgrip strength was measured with a Smedley dynamometer. Results showed that peak mean values of handgrip strength are reached in men's and women's 30s and 40s after which handgrip strength declines in linear fashion with age. Following published recommendations, the study used a cut-off at 2 SD below the sex-specific peak mean value across the life course to define a 'weak grip'. Less than 10% of women and men aged 65-69 were classified as weak according to this definition, shares increasing to about half of the population aged 80-90. Based on survival analysis that linked handgrip strength to a relevant outcome, however, a 'critically weak grip' that warrants further examination was estimated to commence already at 1 SD below the group-specific mean value.
Large-scale weakly nonlinear perturbations of convective magnetic dynamos in a rotating layer
Chertovskih, Roman
2015-01-01
We present a new mechanism for generation of large-scale magnetic field by thermal convection which does not involve the alpha-effect. We consider weakly nonlinear perturbations of space-periodic steady convective magnetic dynamos in a rotating layer that were identified in our previous work. The perturbations have a spatial scale in the horizontal direction that is much larger than the period of the perturbed convective magnetohydrodynamic state. Following the formalism of the multiscale stability theory, we have derived the system of amplitude equations governing the evolution of the leading terms in expansion of the perturbations in power series in the scale ratio. This asymptotic analysis is more involved than in the cases considered earlier, because the kernel of the operator of linearisation has zero-mean neutral modes whose origin lies in the spatial invariance of the perturbed regime, the operator reduced on the generalised kernel has two Jordan normal form blocks of size two, and simplifying symmetri...
Hossain, Delowar; Samad, Abdus; Alam, Mahmud
2017-06-01
The ion-slip effects on unsteady MHD free convection flow past an infinite vertical porous plate with the effect of temperature stratified porous medium in a rotating system with viscous dissipation and Joule heating has been studied numerically. Introducing a time dependent suction to the plate, a similarity procedure has been adopted by taking a time dependent similarity parameter. The governing differential equations are transformed by introducing usual similarity variables. The resultant equations are solved numerically using Runge-Kutta method along with shooting technique. Resulting non-dimensional velocity and temperature profiles are then presented graphically for different values of the parameters entering into the problem.
Indian Academy of Sciences (India)
Joginder S. Dhiman; Rekha Dadwal
2012-12-01
The problem of self-gravitational instability of an infinite, homogeneous stratified gaseous medium with finite thermal conductivity and infinite electrical conductivity, in the presence of non-uniform rotation and magnetic field in the Chandrasekhar’s frame of reference, is studied. It is found that the magnetic field, whether uniform or non-uniform, has no effect on the Jeans’ criterion for gravitational instability and remains essentially unaffected. However, the thermal conductivity has the usual stabilizing effect on the criterion that the adiabatic sound velocity occurring in the Jeans criterion is replaced by the isothermal sound velocity. Thus, the present analysis extends the results of Chandrasekhar for the case of heat conducting medium and for non-uniform rotation and magnetic field.
Hamiltonian dynamics with a weak noise and the echo effect for the rotator model
Energy Technology Data Exchange (ETDEWEB)
Turchetti, Giorgio [Department of Physics, University of Bologna, INFN Sezione di Bologna (Italy); Bassi, Gabriele [Department of Mathematics and Statistics, University of New Mexico, Albuquerque, NM (United States); Bazzani, Armando [Department of Physics, University of Bologna, INFN Sezione di Bologna (Italy); Giorgini, Bruno [Department of Physics, University of Bologna, INFN Sezione di Bologna (Italy); Mais, Helmut [DESY Hamburg (Germany)
2006-09-15
We analyse the effect of a weak noise on the Hamiltonian transport from the analytical and numerical viewpoint. A solvable model, the noisy rotator, is proposed to illustrate the basic phenomena. In the absence of noise, the phase space evolution is a shear flow, whose angular correlations decay following a power law, which depends on the smoothness of the initial action distribution. If the action has a fluctuating component, given by a Wiener process, then the angular correlations decay exponentially according to e{sup -{epsilon}{sup 2}}{sup t{sup 3/6}} or faster, where {epsilon} is the noise amplitude. The echo effect is well suited to investigate the competition between the decorrelation due to filamentation and noise. The noisy rotator model allows an exhaustive analytical investigation of the process for a wide class of initial conditions and a generic disturbance. The echo time is proportional to the delay {tau} of the disturbance and its amplitude is proportional to {lambda}{tau}, where {lambda} is the amplitude of the disturbance. The noise reduces the echo amplitude by e{sup -c{epsilon}{sup 2}}{sup t{sup 3}}, where c depends on the Fourier components of the initial angular distribution, and of the disturbance applied at time {tau}. The analytical results, derived in the limit {lambda} {yields} 0, {tau} {yields} {infinity}, with {lambda}{tau} finite and sufficiently small to justify a first-order expansion, are checked numerically. For more realistic models the analytical procedure would provide qualitative results and scaling laws. Quantitative results are obtained by solving the Fokker-Planck equation with a numerical scheme based on splitting: back propagation and biquadratic interpolation for the integrable part, implicit finite difference scheme for the noise component. The application to a noisy pendulum describing the longitudinal dynamics in a particle accelerator is considered, and we determine the value of the noise amplitude {epsilon}, below
Turn: Weak Interactions and Rotational Barriers in Molecules-Insights from Substituted Butynes.
Omorodion, Oluwarotimi; Bober, Matthew; Donald, Kelling J
2016-11-10
The nature of the bonding and a definite preference for an eclipsed geometry in several substituted but-2-ynes, including certain novel derivatives are uncovered and examined. In particular, we consider the molecular species R3C-C≡C-CR3 (where R= H, F, Cl, Br, I, and CN), their R3C-B≡N-CR3 analogues, and a few novel exo-bridge systems with intramolecular hydrogen bonds running parallel to the C-C≡C-C chain. In some cases, the potential energy surfaces are remarkably flat-so flat, in fact, that free rotation is predicted for those molecules at very low temperatures. A systematic investigation of the bonding in the halogenated butynes demonstrates that the eclipsed conformation actually becomes more stable relative to the staggered form as R becomes larger and less electron-withdrawing. The rotational barriers (the differences in energy between the eclipsed and staggered geometries) are magnified significantly, however, in a special case where selected R groups at the ends of the R3C-C≡C-CR'3 molecule form hydrogen bonds parallel to the C-C≡C-C core. In those systems, the hydrogen bonds serve as a weak locking mechanism that favors the eclipsed conformation. A comparison of HF and uncorrected DFT methods versus the MP2(full), CCSD(T), and other dispersion-corrected methods confirms that correlation accounts to a significant extent for barriers in substituted butyne compounds. In the hydrogen-bonded systems, the barriers are comparable to and larger in some cases than the barriers observed for the more extensively studied ethane molecule.
Velandia, Nelson
2016-01-01
This paper formulates, via the Mathisson - Papapetrou - Dixon equations, the system of equations for a test particle with spin when it is orbiting a weak Kerr metric. We shall restrict ourselves to the case of circular orbits with the purpose of comparing our results with the results of the literature. In particular, we solve the set of equations of motion for the case of circular trajectories both spinless and spinning test particles around rotating bodies in equatorial plane. The results obtained are an important guideline for the study of the effects of the particles with spin in rotating gravitational fields such as Gravitomagnetics Effects or gravitational waves.
Directory of Open Access Journals (Sweden)
R. Mantovani
2002-01-01
Full Text Available This paper presents the analysis of symmetric circulations of a rotating baroclinic flow, forced by a steady thermal wind and dissipated by Laplacian friction. The analysis is performed with numerical time-integration. Symmetric flows, vertically bound by horizontal walls and subject to either periodic or vertical wall lateral boundary conditions, are investigated in the region of parameter-space where unstable small amplitude modes evolve into stable stationary nonlinear solutions. The distribution of solutions in parameter-space is analysed up to the threshold of chaotic behaviour and the physical nature of the nonlinear interaction operating on the finite amplitude unstable modes is investigated. In particular, analysis of time-dependent energy-conversions allows understanding of the physical mechanisms operating from the initial phase of linear instability to the finite amplitude stable state. Vertical shear of the basic flow is shown to play a direct role in injecting energy into symmetric flow since the stage of linear growth. Dissipation proves essential not only in limiting the energy of linearly unstable modes, but also in selecting their dominant space-scales in the finite amplitude stage.
The drift force on an object in an inviscid weakly-varying rotational flow
Energy Technology Data Exchange (ETDEWEB)
Wallis, G.B. [Dartmouth College, Hanover, NH (United States)
1995-12-31
The force on any stationary object in an inviscid incompressible extensive steady flow is derived in terms of the added mass tensor and gradient of velocity of the undisturbed fluid. Taylor`s theorem is extended to flows with weak vorticity. There are possible applications to constitutive equations for two-phase flow.
The strength of the rotating Presidency is that it keeps the Presidency weak
DEFF Research Database (Denmark)
Beach, Derek
that while the powers possessed by the Presidency are relatively weak, it is the very weakness of the Presidency that makes it an effective leader. Drawing upon recent advances in the study of informal norms in the Council and leadership theories, this paper first discusses what types of leadership...... are demanded in the Council. It is argued that given the consensual and long-term iterated game nature of EU decision-making, consensual forms of leadership are the most effective at achieving maximum possible gains from cooperation. In this type of leadership, the leader manages the agenda in an acceptable...... fashion to all, and finds, formulates and brokers acceptable compromises. Acceptable is not the same as being neutral, and an instrumental leader can exploit its position for private gains, but it cannot be too blatant as it is in more hegemonic forms of leadership....
Directory of Open Access Journals (Sweden)
P. D. Williams
2004-01-01
Full Text Available We report on a numerical study of the impact of short, fast inertia-gravity waves on the large-scale, slowly-evolving flow with which they co-exist. A nonlinear quasi-geostrophic numerical model of a stratified shear flow is used to simulate, at reasonably high resolution, the evolution of a large-scale mode which grows due to baroclinic instability and equilibrates at finite amplitude. Ageostrophic inertia-gravity modes are filtered out of the model by construction, but their effects on the balanced flow are incorporated using a simple stochastic parameterization of the potential vorticity anomalies which they induce. The model simulates a rotating, two-layer annulus laboratory experiment, in which we recently observed systematic inertia-gravity wave generation by an evolving, large-scale flow. We find that the impact of the small-amplitude stochastic contribution to the potential vorticity tendency, on the model balanced flow, is generally small, as expected. In certain circumstances, however, the parameterized fast waves can exert a dominant influence. In a flow which is baroclinically-unstable to a range of zonal wavenumbers, and in which there is a close match between the growth rates of the multiple modes, the stochastic waves can strongly affect wavenumber selection. This is illustrated by a flow in which the parameterized fast modes dramatically re-partition the probability-density function for equilibrated large-scale zonal wavenumber. In a second case study, the stochastic perturbations are shown to force spontaneous wavenumber transitions in the large-scale flow, which do not occur in their absence. These phenomena are due to a stochastic resonance effect. They add to the evidence that deterministic parameterizations in general circulation models, of subgrid-scale processes such as gravity wave drag, cannot always adequately capture the full details of the nonlinear interaction.
GRBs from Weakly-Magnetized, Slowly-Rotating Stars in Binaries
Méndez, Enrique Moreno
2014-01-01
The spin of a number of black holes (BHs) in X-ray binaries (XBs) has been predicted (and, in at least three cases, confirmed by observations) by using a binary stellar evolution model with Case-C mass transfer . The rotational energy of such BHs is sufficient to power up (long) gamma-ray bursts and hypernovae (GRBs/HNe) and still leave a Kerr BH behind. However, strong magnetic fields (B fields) and/or dynamo effects in the interior of a BH-progenitor star may be capable of rapidly depleting the angular momentum from the stellar core, hence, preventing the formation of a collapsar. Thus, even if binaries can produce Kerr BHs, most of their rotation is acquired from accreting the stellar mantle, with a long delay between the formation of the BH and its spin up. Hence, not being good sources of GRBs. We study the necessary conditions to produce GRBs by the progenitors of such BHs. Tidal-synchronization and Alfv\\'en timescales are compared for B fields of different intensities threading trough He stars. We sear...
Takahashi, Koh; Umeda, Hideyuki; Yoshida, Takashi
2015-01-01
The three most iron-poor stars known until now are also known to have peculiar enhancements of intermediate mass elements. Under the assumption that these iron-deficient stars reveal the nucleosynthesis result of Pop III stars, we show that a weak supernova model successfully reproduces the observed abundance patterns. Moreover, we show that the initial parameters of the progenitor, such as the initial masses and the rotational property, can be constrained by the model, since the stellar yields result from the nucleosynthesis in the outer region of the star, which is significantly affected by the initial parameters. The initial parameter of Pop III stars is of prime importance for the theoretical study of the early universe. Future observation will increase the number of such carbon enhanced iron-deficient stars, and the same analysis on the stars may give valuable information for the Pop III stars that existed in our universe.
Takahashi, Koh; Yoshida, Takashi
2014-01-01
We perform stellar evolution simulation of first stars and calculate stellar yields from the first supernovae. The initial masses are taken from 12 to 140 Msun to cover the whole range of core-collapse supernova progenitors, and stellar rotation is included, which results in efficient internal mixing. A weak explosion is assumed in supernova yield calculations, thus only outer distributed matter, which is not affected by the explosive nucleosynthesis, is ejected in the models. We show that the initial mass and the rotation affect the explosion yield. All the weak explosion models have abundances of [C/O] larger than unity. Stellar yields from massive progenitors of > 40-60 Msun show enhancement of Mg and Si. Rotating models yield abundant Na and Al. And Ca is synthesized in non-rotating heavy massive models of > 80 Msun. We fit the stellar yields to the three most iron-deficient stars, and constrain the initial parameters of the mother progenitor stars. The abundance pattern in SMSS 0313-6708 is well explaine...
Briquet, M.; Neiner, C.; Petit, P.; Leroy, B.; de Batz, B.
2016-03-01
Aims: The main-sequence B-type star ζ Cassiopeiae is known as a N-rich star with a magnetic field discovered with the Musicos spectropolarimeter. We model the magnetic field of the star by means of 82 new spectropolarimetric observations of higher precision to investigate the field strength, topology, and effect. Methods: We gathered data with the Narval spectropolarimeter installed at Télescope Bernard Lyot (TBL; Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from ζ Cas. We used a dipole oblique rotator model to determine the field configuration by fitting the longitudinal field measurements and by synthesizing the measured Stokes V profiles. We also made use of the Zeeman-Doppler imaging technique to map the stellar surface and to deduce the difference in rotation rate between the pole and equator. Results: ζ Cas exhibits a polar field strength Bpol of 100-150 G, which is the weakest polar field observed so far in a massive main-sequence star. Surface differential rotation is ruled out by our observations and the field of ζ Cas is strong enough to enforce rigid internal rotation in the radiative zone according to theory. Thus, the star rotates as a solid body in the envelope. Conclusions: We therefore exclude rotationally induced mixing as the cause of the surface N-enrichment. We discuss that the transport of chemicals from the core to the surface by internal gravity waves is the most plausible explanation for the nitrogen overabundance at the surface of ζ Cas. Based on observations obtained at the Télescope Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées, Université de Toulouse (Paul Sabatier), Centre National de la Recherche Scientifique (CNRS) of France.
Zhao, Ming; Jia, Xiaodong
2017-09-01
Singular value decomposition (SVD), as an effective signal denoising tool, has been attracting considerable attention in recent years. The basic idea behind SVD denoising is to preserve the singular components (SCs) with significant singular values. However, it is shown that the singular values mainly reflect the energy of decomposed SCs, therefore traditional SVD denoising approaches are essentially energy-based, which tend to highlight the high-energy regular components in the measured signal, while ignoring the weak feature caused by early fault. To overcome this issue, a reweighted singular value decomposition (RSVD) strategy is proposed for signal denoising and weak feature enhancement. In this work, a novel information index called periodic modulation intensity is introduced to quantify the diagnostic information in a mechanical signal. With this index, the decomposed SCs can be evaluated and sorted according to their information levels, rather than energy. Based on that, a truncated linear weighting function is proposed to control the contribution of each SC in the reconstruction of the denoised signal. In this way, some weak but informative SCs could be highlighted effectively. The advantages of RSVD over traditional approaches are demonstrated by both simulated signals and real vibration/acoustic data from a two-stage gearbox as well as train bearings. The results demonstrate that the proposed method can successfully extract the weak fault feature even in the presence of heavy noise and ambient interferences.
Briquet, M; Petit, P; Leroy, B; de Batz, B
2016-01-01
Aims. The main-sequence B-type star $\\zeta$ Cassiopeiae is known as a N-rich star with a magnetic field discovered with the Musicos spectropolarimeter. We model the magnetic field of the star by means of 82 new spectropolarimetric observations of higher precision to investigate the field strength, topology, and effect. Methods. We gathered data with the Narval spectropolarimeter installed at T\\'elescope Bernard Lyot (TBL, Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from $\\zeta$ Cas. We used a dipole oblique rotator model to determine the field configuration by fitting the longitudinal field measurements and by synthesizing the measured Stokes V profiles. We also made use of the Zeeman-Doppler Imaging technique to map the stellar surface and to deduce the difference in rotation rate between the pole and equator. Results. $\\zeta$ Cas exhibits a polar field strength $B_{\\rm pol}$ of 100-150 G, which is the weakest polar fiel...
Tursunov, Arman; Kološ, Martin
2016-01-01
We study motion of charged particles in the field of a rotating black hole immersed into an external asymptotically uniform magnetic field, focusing on the epicyclic quasi-circular orbits near the equatorial plane. Separating the circular orbits into four qualitatively different classes according to the sign of the canonical angular momentum of the motion and the orientation of the Lorentz force, we analyse the circular orbits using the so called force formalism. We find the analytical solutions for the radial profiles of velocity, specific angular momentum and specific energy of the circular orbits in dependence on the black hole dimensionless spin and the magnetic field strength. The innermost stable circular orbits are determined for all four classes of the circular orbits. The stable circular orbits with outward oriented Lorentz force can extend to radii lower than the radius of the corresponding photon circular geodesic. We calculate the frequencies of the harmonic oscillatory motion of the charged parti...
The Effect of Rotation on Oscillatory Double-diffusive Convection (Semiconvection)
Moll, Ryan; Garaud, Pascale
2017-01-01
Oscillatory double-diffusive convection (ODDC, more traditionally called semiconvection) is a form of linear double-diffusive instability that occurs in fluids that are unstably stratified in temperature (Schwarzschild unstable), but stably stratified in chemical composition (Ledoux stable). This scenario is thought to be quite common in the interiors of stars and giant planets, and understanding the transport of heat and chemical species by ODDC is of great importance to stellar and planetary evolution models. Fluids unstable to ODDC have a tendency to form convective thermocompositional layers that significantly enhance the fluxes of temperature and chemical composition compared with microscopic diffusion. Although a number of recent studies have focused on studying properties of both layered and nonlayered ODDC, few have addressed how additional physical processes such as global rotation affect its dynamics. In this work, we study first how rotation affects the linear stability properties of rotating ODDC. Using direct numerical simulations, we then analyze the effect of rotation on properties of layered and nonlayered ODDC, and we study how the angle of the rotation axis with respect to the direction of gravity affects layering. We find that rotating systems can be broadly grouped into two categories based on the strength of rotation. The qualitative behavior in the more weakly rotating group is similar to nonrotating ODDC, but strongly rotating systems become dominated by vortices that are invariant in the direction of the rotation vector and strongly influence transport. We find that whenever layers form, rotation always acts to reduce thermal and compositional transport.
Fluttering in Stratified Flows
Lam, Try; Vincent, Lionel; Kanso, Eva
2016-11-01
The descent motion of heavy objects under the influence of gravitational and aerodynamic forces is relevant to many branches of engineering and science. Examples range from estimating the behavior of re-entry space vehicles to studying the settlement of marine larvae and its influence on underwater ecology. The behavior of regularly shaped objects freely falling in homogeneous fluids is relatively well understood. For example, the complex interaction of a rigid coin with the surrounding fluid will cause it to either fall steadily, flutter, tumble, or be chaotic. Less is known about the effect of density stratification on the descent behavior. Here, we experimentally investigate the descent of discs in both pure water and in a linearly salt-stratified fluids where the density is varied from 1.0 to 1.14 of that of water where the Brunt-Vaisala frequency is 1.7 rad/sec and the Froude number Fr robots for space exploration and underwater missions.
Directory of Open Access Journals (Sweden)
Jenny Kathinka Krüger
2016-03-01
Full Text Available Aviation security screeners analyze a large number of X-ray images per day and seem to be experts in mentally rotating diverse kinds of visual objects. A robust gender-effect that men outperform women in the Vandenberg & Kuse mental rotation task has been well documented over the last years. In addition it has been shown that training can positively influence the overall task-performance. Considering this, the aim of the present study was to investigate whether security screeners show better performance in the Mental Rotation Test (MRT independently of gender. Forty-seven security screeners of both sexes from two German airports were examined with a computer based MRT. Their performance was compared to a large sample of control subjects. The well-known gender-effect favoring men on mental rotation was significant within the control group. However, the security screeners did not show any sex differences suggesting an effect of training and professional performance. Surprisingly this specialized group showed a lower level of overall MRT performance than the control participants. Possible aviation related influences such as secondary effects of work-shift or expertise which can cumulatively cause this result are discussed.
Krüger, Jenny K; Suchan, Boris
2016-01-01
Aviation security screeners analyze a large number of X-ray images per day and seem to be experts in mentally rotating diverse kinds of visual objects. A robust gender-effect that men outperform women in the Vandenberg & Kuse mental rotation task has been well documented over the last years. In addition it has been shown that training can positively influence the overall task-performance. Considering this, the aim of the present study was to investigate whether security screeners show better performance in the Mental Rotation Test (MRT) independently of gender. Forty-seven security screeners of both sexes from two German airports were examined with a computer based MRT. Their performance was compared to a large sample of control subjects. The well-known gender-effect favoring men on mental rotation was significant within the control group. However, the security screeners did not show any sex differences suggesting an effect of training and professional performance. Surprisingly this specialized group showed a lower level of overall MRT performance than the control participants. Possible aviation related influences such as secondary effects of work-shift or expertise which can cumulatively cause this result are discussed.
Clustering of floating particles in stratified turbulence
Boffetta, Guido; de Lillo, Filippo; Musacchio, Stefano; Sozza, Alessandro
2016-11-01
We study the dynamics of small floating particles transported by stratified turbulence in presence of a mean linear density profile as a simple model for the confinement and the accumulation of plankton in the ocean. By means of extensive direct numerical simulations we investigate the statistical distribution of floaters as a function of the two dimensionless parameters of the problem. We find that vertical confinement of particles is mainly ruled by the degree of stratification, with a weak dependency on the particle properties. Conversely, small scale fractal clustering, typical of non-neutral particles in turbulence, depends on the particle relaxation time and is only weakly dependent on the flow stratification. The implications of our findings for the formation of thin phytoplankton layers are discussed.
The fully nonlinear stratified geostrophic adjustment problem
Coutino, Aaron; Stastna, Marek
2017-01-01
The study of the adjustment to equilibrium by a stratified fluid in a rotating reference frame is a classical problem in geophysical fluid dynamics. We consider the fully nonlinear, stratified adjustment problem from a numerical point of view. We present results of smoothed dam break simulations based on experiments in the published literature, with a focus on both the wave trains that propagate away from the nascent geostrophic state and the geostrophic state itself. We demonstrate that for Rossby numbers in excess of roughly 2 the wave train cannot be interpreted in terms of linear theory. This wave train consists of a leading solitary-like packet and a trailing tail of dispersive waves. However, it is found that the leading wave packet never completely separates from the trailing tail. Somewhat surprisingly, the inertial oscillations associated with the geostrophic state exhibit evidence of nonlinearity even when the Rossby number falls below 1. We vary the width of the initial disturbance and the rotation rate so as to keep the Rossby number fixed, and find that while the qualitative response remains consistent, the Froude number varies, and these variations are manifested in the form of the emanating wave train. For wider initial disturbances we find clear evidence of a wave train that initially propagates toward the near wall, reflects, and propagates away from the geostrophic state behind the leading wave train. We compare kinetic energy inside and outside of the geostrophic state, finding that for long times a Rossby number of around one-quarter yields an equal split between the two, with lower (higher) Rossby numbers yielding more energy in the geostrophic state (wave train). Finally we compare the energetics of the geostrophic state as the Rossby number varies, finding long-lived inertial oscillations in the majority of the cases and a general agreement with the past literature that employed either hydrostatic, shallow-water equation-based theory or
Okuma, Ryutaro; Yajima, Takeshi; Nishio-Hamane, Daisuke; Okubo, Tsuyoshi; Hiroi, Zenji
2017-03-01
Novel magnetic phases are expected to occur in highly frustrated spin systems. Here, we study the structurally perfect kagome antiferromagnet CdC u3(OH) 6(NO3)2.H2O by magnetization, magnetic torque, and heat capacity measurements using single crystals. An antiferromagnetic order accompanied by a small spontaneous magnetization that surprisingly is confined in the kagome plane sets in at TN˜4 K , well below the nearest-neighbor exchange interaction J /kB=45 K . This suggests that a unique "q =0 " type 120∘ spin structure with "negative" (downward) vector chirality, which breaks the underlying threefold rotational symmetry of the kagome lattice and thus allows a spin canting within the plane, is exceptionally realized in this compound rather than a common one with "positive" (upward) vector chirality. The origin is discussed in terms of the Dzyaloshinskii-Moriya interaction.
Directory of Open Access Journals (Sweden)
Jasmeet Kaur
2017-02-01
Full Text Available The g-factor and the static quadrupole moment of a magnetic rotational band head 212− at 2121 keV in 131La have been determined by means of the time-differential perturbed angular distribution technique. The measured value of the g-factor, +1.060(4, is in agreement with the theoretical value for a three quasi-proton, π3{112−[505]⊗52+[422]⊗52+[413]} Nilsson configuration assignment. The observed spectroscopic quadrupole moment ratio, Qs(212−,131LaQs(192−,137La=0.457(4, supports the collective oblate shape (γ∼−60° with quadrupole deformation β2<0.07. The half-life of the 212− state, 37.2(1 ns, is re-measured with better accuracy.
Kaur, Jasmeet; Bansal, Neeraj; Bhati, A. K.; Kumar, R.; Sharma, Vijay R.; Kapoor, K.; Kumar, V.; Kaur, Navneet
2017-02-01
The g-factor and the static quadrupole moment of a magnetic rotational band head 21/2- at 2121 keV in 131La have been determined by means of the time-differential perturbed angular distribution technique. The measured value of the g-factor, + 1.060 (4), is in agreement with the theoretical value for a three quasi-proton, π3 {11/2- [ 505 ] ⊗5/2+ [ 422 ] ⊗5/2+ [ 413 ] } Nilsson configuration assignment. The observed spectroscopic quadrupole moment ratio, Qs (21/2- ,131 La)/Qs (19/2- ,137 La) = 0.457 (4), supports the collective oblate shape (γ ∼ - 60 °) with quadrupole deformation β2 < 0.07. The half-life of the 21/2- state, 37.2(1) ns, is re-measured with better accuracy.
Weak Convergence and Weak Convergence
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Narita Keiko
2015-09-01
Full Text Available In this article, we deal with weak convergence on sequences in real normed spaces, and weak* convergence on sequences in dual spaces of real normed spaces. In the first section, we proved some topological properties of dual spaces of real normed spaces. We used these theorems for proofs of Section 3. In Section 2, we defined weak convergence and weak* convergence, and proved some properties. By RNS_Real Mizar functor, real normed spaces as real number spaces already defined in the article [18], we regarded sequences of real numbers as sequences of RNS_Real. So we proved the last theorem in this section using the theorem (8 from [25]. In Section 3, we defined weak sequential compactness of real normed spaces. We showed some lemmas for the proof and proved the theorem of weak sequential compactness of reflexive real Banach spaces. We referred to [36], [23], [24] and [3] in the formalization.
Nobili, A. M.; Bramanti, D.; Polacco, E.; Catastini, G.; Anselmi, A.; Portigliotti, S.; Lenti, A.; di Giamberardino, P.; Monaco, S.; Ronchini, R.
1999-04-01
Test masses coupled by weak mechanical suspensions are sensitive to differential forces such as the force due to a possible violation of the equivalence principle (EP). If in addition they are put in rapid rotation, the differential signal is modulated at high frequency, which is beneficial for noise reduction. Galileo Galilei (GG) is a proposed space experiment for testing the equivalence principle to 1 part in 0264-9381/16/4/032/img8 based on these concepts. A recent paper by Jafry and Weinberger (1998 Class. Quantum Grav. 15 481-500) claims that GG can only reach 0264-9381/16/4/032/img9. We show that the analysis of this paper is flawed (by several orders of magnitude) because of two misconceptions: one on the physical nature of mechanical damping and the other on active control methods for the stabilization of spinning bodies.
Caleo, Andrea
2016-01-01
Barotropic rotation and radiative equilibrium are mutually incompatible in stars. The issue is often addressed by allowing for a meridional circulation, but this is not devoid of theoretical complications. Models of rotation in the Sun which maintain strict radiative equilibrium, making use of the observation that the Sun is not in a state of barotropic rotation, have recently been suggested. To investigate the dynamical behaviour of these solutions, we study the local stability of stratified, weakly magnetized, differentially rotating fluids to non-axisymmetric perturbations. Finite heat conductivity, kinematic viscosity, and resistivity are present. The evolution of local embedded perturbations is governed by a set of coupled, ordinary differential equations with time-dependent coefficients. Two baroclinic models of rotation for the upper radiative zone and tachocline are studied: (i) an interpolation based on helioseismology data, (ii) a theoretical solution directly compatible with radiative equilibrium. ...
Inertial modes of non-stratified superfluid neutron stars
Prix, R; Andersson, N
2004-01-01
We present results concerning adiabatic inertial-mode oscillations of non-stratified superfluid neutron stars in Newtonian gravity, using the anelastic and slow-rotation approximations. We consider a simple two-fluid model of a superfluid neutron star, where one fluid consists of the superfluid neutrons and the second fluid contains all the comoving constituents (protons, electrons). The two fluids are assumed to be ``free'' in the sense that vortex-mediated forces like mutual friction or pinning are absent, but they can be coupled by the equation of state, in particular by entrainment. The stationary background consists of the two fluids rotating uniformly around the same axis with potentially different rotation rates. We study the special cases of co-rotating backgrounds, vanishing entrainment, and the purely toroidal r-modes, analytically. We calculate numerically the eigenfunctions and frequencies of inertial modes in the general case of non co-rotating backgrounds, and study their dependence on the relat...
On turbulence in a stratified environment
Sarkar, Sutanu
2015-11-01
John Lumley, motivated by atmospheric observations, made seminal contributions to the statistical theory (Lumley and Panofsky 1964, Lumley 1964) and second-order modeling (Zeman and Lumley 1976) of turbulence in the environment. Turbulent processes in the ocean share many features with the atmosphere, e.g., shear, stratification, rotation and rough topography. Results from direct and large eddy simulations of two model problems will be used to illustrate some of the features of turbulence in a stratified environment. The first problem concerns a shear layer in nonuniform stratification, a situation typical of both the atmosphere and the ocean. The second problem, considered to be responsible for much of the turbulent mixing that occurs in the ocean interior, concerns topographically generated internal gravity waves. Connections will be made to data taken during observational campaigns in the ocean.
Electromagnetic waves in stratified media
Wait, James R; Fock, V A; Wait, J R
2013-01-01
International Series of Monographs in Electromagnetic Waves, Volume 3: Electromagnetic Waves in Stratified Media provides information pertinent to the electromagnetic waves in media whose properties differ in one particular direction. This book discusses the important feature of the waves that enables communications at global distances. Organized into 13 chapters, this volume begins with an overview of the general analysis for the electromagnetic response of a plane stratified medium comprising of any number of parallel homogeneous layers. This text then explains the reflection of electromagne
Stratified medicine and reimbursement issues
Fugel, Hans-Joerg; Nuijten, Mark; Postma, Maarten
2012-01-01
Stratified Medicine (SM) has the potential to target patient populations who will most benefit from a therapy while reducing unnecessary health interventions associated with side effects. The link between clinical biomarkers/diagnostics and therapies provides new opportunities for value creation to
Without the weak force, the sun wouldn't shine. The weak force causes beta decay, a form of radioactivity that triggers nuclear fusion in the heart of the sun. The weak force is unlike other forces: it is characterised by disintegration. In beta decay, a down quark transforms into an up quark and an electron is emitted. Some materials are more radioactive than others because the delicate balance between the strong force and the weak force varies depending on the number of particles in the atomic nucleus. We live in the midst of a natural radioactive background that varies from region to region. For example, in Cornwall where there is a lot of granite, levels of background radiation are much higher than in the Geneva region. Text for the interactive: Move the Geiger counter to find out which samples are radioactive - you may be surprised. It is the weak force that is responsible for the Beta radioactivity here. The electrons emitted do not cross the plastic cover. Why do you think there is some detected radioa...
Study of MRI in Stratified Viscous Plasma Configuration
Carlevaro, Nakia; Renzi, Fabrizio
2016-01-01
We analyze the morphology of the Magneto-rotational Instability (MRI) for a stratified viscous plasma disk configuration in differential rotation, taking into account the so-called corotation theorem for the background profile. In order to select the intrinsic Alfv\\'enic nature of MRI, we deal with an incompressible plasma and we adopt a formulation of the perturbation analysis based on the use of the magnetic flux function as a dynamical variable. Our study outlines, as consequence of the corotation condition, a marked asymmetry of the MRI with respect to the equatorial plane, particularly evident in a complete damping of the instability over a positive critical height on the equatorial plane. We also emphasize how such a feature is already present (although less pronounced) even in the ideal case, restoring a dependence of the MRI on the stratified morphology of the gravitational field.
Turbulence in Rotating (and/or) Stratified Fluids Task 1
1988-09-30
dimensional disturbance in the form of a travelling wave given by uv (xt) = (4)e lix=-t) a is the complex wave number. a = ar +/a. and w is a real ...Layers on the Presence of Solid Boundaries." J. de Mecanique Theorique et appliquee. Numero Special. P. 121. Kim. John and Mon. Parvlz. 1986. "lie
Selleri, Franco
2015-01-01
Weak Relativity is an equivalent theory to Special Relativity according to Reichenbach’s definition, where the parameter epsilon equals to 0. It formulates a Neo-Lorentzian approach by replacing the Lorentz transformations with a new set named “Inertial Transformations”, thus explaining the Sagnac effect, the twin paradox and the trip from the future to the past in an easy and elegant way. The cosmic microwave background is suggested as a possible privileged reference system. Most importantly, being a theory based on experimental proofs, rather than mutual consensus, it offers a physical description of reality independent of the human observation.
Stratified Medicine and Reimbursement Issues
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Hans-Joerg eFugel
2012-10-01
Full Text Available Stratified Medicine (SM has the potential to target patient populations who will most benefit from a therapy while reducing unnecessary health interventions associated with side effects. The link between clinical biomarkers/diagnostics and therapies provides new opportunities for value creation to strengthen the value proposition to pricing and reimbursement (P&R authorities. However, the introduction of SM challenges current reimbursement schemes in many EU countries and the US as different P&R policies have been adopted for drugs and diagnostics. Also, there is a lack of a consistent process for value assessment of more complex diagnostics in these markets. New, innovative approaches and more flexible P&R systems are needed to reflect the added value of diagnostic tests and to stimulate investments in new technologies. Yet, the framework for access of diagnostic–based therapies still requires further development while setting the right incentives and appropriate align stakeholders interests when realizing long- term patient benefits. This article addresses the reimbursement challenges of SM approaches in several EU countries and the US outlining some options to overcome existing reimbursement barriers for stratified medicine.
Suppression of stratified explosive interactions
Energy Technology Data Exchange (ETDEWEB)
Meeks, M.K.; Shamoun, B.I.; Bonazza, R.; Corradini, M.L. [Wisconsin Univ., Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics
1998-01-01
Stratified Fuel-Coolant Interaction (FCI) experiments with Refrigerant-134a and water were performed in a large-scale system. Air was uniformly injected into the coolant pool to establish a pre-existing void which could suppress the explosion. Two competing effects due to the variation of the air flow rate seem to influence the intensity of the explosion in this geometrical configuration. At low flow rates, although the injected air increases the void fraction, the concurrent agitation and mixing increases the intensity of the interaction. At higher flow rates, the increase in void fraction tends to attenuate the propagated pressure wave generated by the explosion. Experimental results show a complete suppression of the vapor explosion at high rates of air injection, corresponding to an average void fraction of larger than 30%. (author)
Al Kaissi, Ali; Ryabykh, Sergey; Ochirova, Polina; Kenis, Vladimir; Hofstätter, Jochen G.; Grill, Franz; Ganger, Rudolf; Kircher, Susanne Gerit
2017-01-01
Marked ligamentous hyperlaxity and muscle weakness/wasting associated with awkward gait are the main deficits confused with the diagnosis of myopathy. Seven children (6 boys and 1 girl with an average age of 8 years) were referred to our department because of diverse forms of skeletal abnormalities. No definitive diagnosis was made, and all underwent a series of sophisticated investigations in other institutes in favor of myopathy. We applied our methodology through the clinical and radiographic phenotypes followed by targeted genotypic confirmation. Three children (2 boys and 1 girl) were compatible with the diagnosis of progressive pseudorheumatoid chondrodysplasia. The genetic mutation was correlated with the WISP 3 gene actively expressed by articular chondrocytes and located on chromosome 6. Klinefelter syndrome was the diagnosis in 2 boys. Karyotyping confirmed 47,XXY (aneuploidy of Klinefelter syndrome). And 2 boys were finally diagnosed with Morquio syndrome (MPS type IV A) as both showed missense mutations in the N-acetylgalactosamine-sulfate sulfatase gene. Misdiagnosis can lead to the initiation of a long list of sophisticated investigations. PMID:28210640
Stratified wake of an accelerating hydrofoil
Ben-Gida, Hadar; Gurka, Roi
2015-01-01
Wakes of towed and self-propelled bodies in stratified fluids are significantly different from non-stratified wakes. Long time effects of stratification on the development of the wakes of bluff bodies moving at constant speed are well known. In this experimental study we demonstrate how buoyancy affects the initial growth of vortices developing in the wake of a hydrofoil accelerating from rest. Particle image velocimetry measurements were applied to characterize the wake evolution behind a NACA 0015 hydrofoil accelerating in water and for low Reynolds number and relatively strong and stably stratified fluid (Re=5,000, Fr~O(1)). The analysis of velocity and vorticity fields, following vortex identification and an estimate of the circulation, reveal that the vortices in the stratified fluid case are stretched along the streamwise direction in the near wake. The momentum thickness profiles show lower momentum thickness values for the stratified late wake compared to the non-stratified wake, implying that the dra...
Stratified spin-up in a sliced, square cylinder
Energy Technology Data Exchange (ETDEWEB)
Munro, R. J. [Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Foster, M. R. [Department of Mathematical Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)
2014-02-15
We previously reported experimental and theoretical results on the linear spin-up of a linearly stratified, rotating fluid in a uniform-depth square cylinder [M. R. Foster and R. J. Munro, “The linear spin-up of a stratified, rotating fluid in a square cylinder,” J. Fluid Mech. 712, 7–40 (2012)]. Here we extend that analysis to a “sliced” square cylinder, which has a base-plane inclined at a shallow angle α. Asymptotic results are derived that show the spin-up phase is achieved by a combination of the Ekman-layer eruptions (from the perimeter region of the cylinder's lid and base) and cross-slope-propagating stratified Rossby waves. The final, steady state limit for this spin-up phase is identical to that found previously for the uniform depth cylinder, but is reached somewhat more rapidly on a time scale of order E{sup −1/2}Ω{sup −1}/log (α/E{sup 1/2}) (compared to E{sup −1/2}Ω{sup −1} for the uniform-depth cylinder), where Ω is the rotation rate and E the Ekman number. Experiments were performed for Burger numbers, S, between 0.4 and 16, and showed that for S≳O(1), the Rossby modes are severely damped, and it is only at small S, and during the early stages, that the presence of these wave modes was evident. These observations are supported by the theory, which shows the damping factors increase with S and are numerically large for S≳O(1)
How stratified is mantle convection?
Puster, Peter; Jordan, Thomas H.
1997-04-01
We quantify the flow stratification in the Earth's mid-mantle (600-1500 km) in terms of a stratification index for the vertical mass flux, Sƒ (z) = 1 - ƒ(z) / ƒref (z), in which the reference value ƒref(z) approximates the local flux at depth z expected for unstratified convection (Sƒ=0). Although this flux stratification index cannot be directly constrained by observations, we show from a series of two-dimensional convection simulations that its value can be related to a thermal stratification index ST(Z) defined in terms of the radial correlation length of the temperature-perturbation field δT(z, Ω). ST is a good proxy for Sƒ at low stratifications (SƒUniformitarian Principle. The bound obtained here from global tomography is consistent with local seismological evidence for slab flux into the lower mantle; however, the total material flux has to be significantly greater (by a factor of 2-3) than that due to slabs alone. A stratification index, Sƒ≲0.2, is sufficient to exclude many stratified convection models still under active consideration, including most forms of chemical layering between the upper and lower mantle, as well as the more extreme versions of avalanching convection governed by a strong endothermic phase change.
Core science: Stratified by a sunken impactor
Nakajima, Miki
2016-10-01
There is potential evidence for a stratified layer at the top of the Earth's core, but its origin is not well understood. Laboratory experiments suggest that the stratified layer could be a sunken remnant of the giant impact that formed the Moon.
A Fixpoint Semantics for Stratified Databases
Institute of Scientific and Technical Information of China (English)
沈一栋
1993-01-01
Przmusinski extended the notion of stratified logic programs,developed by Apt,Blair and Walker,and by van Gelder,to stratified databases that allow both negative premises and disjunctive consequents.However,he did not provide a fixpoint theory for such class of databases.On the other hand,although a fixpoint semantics has been developed by Minker and Rajasekar for non-Horn logic programs,it is tantamount to traditional minimal model semantics which is not sufficient to capture the intended meaning of negation in the premises of clauses in stratified databases.In this paper,a fixpoint approach to stratified databases is developed,which corresponds with the perfect model semantics.Moreover,algorithms are proposed for computing the set of perfect models of a stratified database.
Weak Galois and Weak Cocleft Coextensions
Institute of Scientific and Technical Information of China (English)
J.N. Alonso (A)lvarez; J.M. Fernández Vilaboa; R. González Rodríguez; A.B. Rodríguez Raposo
2007-01-01
For a weak entwining structure (A, C,ψ) living in a braided monoidal category with equalizers and coequalizers, we formulate the notion of weak A-Galois coextension with normal basis and we show that these Galois coextensions are equivalent to the weak A-cocleft coextensions introduced by the authors.
Theory of inertial waves in rotating fluids
Gelash, Andrey; L'vov, Victor; Zakharov, Vladimir
2017-04-01
The inertial waves emerge in the geophysical and astrophysical flows as a result of Earth rotation [1]. The linear theory of inertial waves is known well [2] while the influence of nonlinear effects of wave interactions are subject of many recent theoretical and experimental studies. The three-wave interactions which are allowed by inertial waves dispersion law (frequency is proportional to cosine of the angle between wave direction and axes of rotation) play an exceptional role. The recent studies on similar type of waves - internal waves, have demonstrated the possibility of formation of natural wave attractors in the ocean (see [3] and references herein). This wave focusing leads to the emergence of strong three-wave interactions and subsequent flows mixing. We believe that similar phenomena can take place for inertial waves in rotating flows. In this work we present theoretical study of three-wave and four-wave interactions for inertial waves. As the main theoretical tool we suggest the complete Hamiltonian formalism for inertial waves in rotating incompressible fluids [4]. We study three-wave decay instability and then present statistical description of inertial waves in the frame of Hamiltonian formalism. We obtain kinetic equation, anisotropic wave turbulence spectra and study the problem of parametric wave turbulence. These spectra were previously found in [5] by helicity decomposition method. Taking this into account we discuss the advantages of suggested Hamiltonian formalism and its future applications. Andrey Gelash thanks support of the RFBR (Grant No.16-31-60086 mol_a_dk) and Dr. E. Ermanyuk, Dr. I. Sibgatullin for the fruitful discussions. [1] Le Gal, P. Waves and instabilities in rotating and stratified flows, Fluid Dynamics in Physics, Engineering and Environmental Applications. Springer Berlin Heidelberg, 25-40, 2013. [2] Greenspan, H. P. The theory of rotating fluids. CUP Archive, 1968. [3] Brouzet, C., Sibgatullin, I. N., Scolan, H., Ermanyuk, E
On the nature of local instabilities in rotating galactic coronae and cool cores of galaxy clusters
Nipoti, Carlo
2014-01-01
A long-standing question is whether radiative cooling can lead to local condensations of cold gas in the hot atmospheres of galaxies and galaxy clusters. We address this problem by studying the nature of local instabilities in rotating, stratified, weakly magnetized, optically thin plasmas in the presence of radiative cooling and anisotropic thermal conduction. For both axisymmetric and non-axisymmetric linear perturbations we provide the general equations that can be applied locally to specific systems to establish whether they are unstable and, in case of instability, to determine the kind of evolution (monotonically growing or over-stable) and the growth rates of unstable modes. We present results for models of rotating plasmas representative of Milky Way-like galaxy coronae and cool-cores of galaxy clusters. It is shown that the unstable modes arise from a combination of thermal, magnetothermal, magnetorotational and heat-flux-driven buoyancy instabilities. Local condensation of cold clouds tends to be ha...
Stably stratified magnetized stars in general relativity
Yoshida, Shijun; Shibata, Masaru
2012-01-01
We construct magnetized stars composed of a fluid stably stratified by entropy gradients in the framework of general relativity, assuming ideal magnetohydrodynamics and employing a barotropic equation of state. We first revisit basic equations for describing stably-stratified stationary axisymmetric stars containing both poloidal and toroidal magnetic fields. As sample models, the magnetized stars considered by Ioka and Sasaki (2004), inside which the magnetic fields are confined, are modified to the ones stably stratified. The magnetized stars newly constructed in this study are believed to be more stable than the existing relativistic models because they have both poloidal and toroidal magnetic fields with comparable strength, and magnetic buoyancy instabilities near the surface of the star, which can be stabilized by the stratification, are suppressed.
Turbulent reconnection of magnetic bipoles in stratified turbulence
Jabbari, Sarah; Mitra, Dhrubaditya; Kleeorin, Nathan; Rogachevskii, Igor
2016-01-01
We consider strongly stratified forced turbulence in a plane-parallel layer with helicity and corresponding large-scale dynamo action in the lower part and nonhelical turbulence in the upper. The magnetic field is found to develop strongly concentrated bipolar structures near the surface. They form elongated bands with a sharp interface between opposite polarities. Unlike earlier experiments with imposed magnetic field, the inclusion of rotation does not strongly suppress the formation of these structures. We perform a systematic numerical study of this phenomenon by varying magnetic Reynolds number, scale separation ratio, and Coriolis number. We also focus on the formation of the current sheet between bipolar regions where reconnection of oppositely oriented field lines occurs. We determine the reconnection rate by measuring either the inflow velocity in the vicinity of the current sheet or by measuring the electric field in the reconnection region. We demonstrate that for small Lundquist number, S1000, the...
Thermals in stratified regions of the ISM
Rodriguez-Gonzalez, Ary
2013-01-01
We present a model of a "thermal" (i.e., a hot bubble) rising within an exponentially stratified region of the ISM. This model includes terms representing the ram pressure braking and the entrainment of environmental gas into the thermal. We then calibrate the free parameters associated with these two terms through a comparison with 3D numerical simulations of a rising bubble. Finally, we apply our "thermal" model to the case of a hot bubble produced by a SN within the stratified ISM of the Galactic disk.
On Stratified Vortex Motions under Gravity.
2014-09-26
AD-A156 930 ON STRATIFIED VORTEX MOTIONS UNDER GRAVITY (U) NAVAL i/i RESEARCH LAB WASHINGTON DC Y T FUNG 20 JUN 85 NRL-MIR-5564 UNCLASSIFIED F/G 20/4...Under Gravity LCn * Y. T. Fung Fluid Dynamics Branch - Marine Technologyv Division June 20, 1985 SO Cyk. NAVAL RESEARCH LABORATORY Washington, D.C...DN880-019 TITLE (Include Security Classification) On Stratified Vortex Motions Under Gravity 12 PERSONAL AUTHOR(S) Funa, Y.T. 13a. TYPE OF REPORT 13b
Mixing by microorganisms in stratified fluids
Wagner, Gregory L; Lauga, Eric
2014-01-01
We examine the vertical mixing induced by the swimming of microorganisms at low Reynolds and P\\'eclet numbers in a stably stratified ocean, and show that the global contribution of oceanic microswimmers to vertical mixing is negligible. We propose two approaches to estimating the mixing efficiency, $\\eta$, or the ratio of the rate of potential energy creation to the total rate-of-working on the ocean by microswimmers. The first is based on scaling arguments and estimates $\\eta$ in terms of the ratio between the typical organism size, $a$, and an intrinsic length scale for the stratified flow, $\\ell = \\left ( \
THERMALS IN STRATIFIED REGIONS OF THE ISM
Directory of Open Access Journals (Sweden)
A. Rodríguez-González
2013-01-01
Full Text Available We present a model of a “thermal” (i.e., a hot bubble rising within an exponentially stratified region of the ISM. This model includes terms representing the ram pressure braking and the entrainment of environmental gas into the thermal. We then calibrate the free parameters associated with these two terms through a comparison with 3D numerical simulations of a rising bubble. Finally, we apply our “thermal” model to the case of a hot bubble produced by a SN within the stratified ISM of the Galactic disk.
Institute of Scientific and Technical Information of China (English)
Yong Hua LI; Hai Bin KAN; Bing Jun YU
2004-01-01
In this paper, a special kind of partial algebras called projective partial groupoids is defined.It is proved that the inverse image of all projections of a fundamental weak regular *-semigroup under the homomorphism induced by the maximum idempotent-separating congruence of a weak regular *-semigroup has a projective partial groupoid structure. Moreover, a weak regular *-product which connects a fundamental weak regular *-semigroup with corresponding projective partial groupoid is defined and characterized. It is finally proved that every weak regular *-product is in fact a weak regular *-semigroup and any weak regular *-semigroup is constructed in this way.
Turbulent Mixing in Stably Stratified Flows
2008-03-01
Liege Colloquium on Ocean Hydrodynamics, volume 46, page 19889898. Elsevier, 1987. R. M. Kerr. Higher-order derivative correlations and the alignment of...19th International Liege Colloquium on Ocean Hydrodynamics, volume 46, pages 3-9. Elsevier, 1988. P. Meunier and G. Spedding. Stratified propelled
Nitrogen transformations in stratified aquatic microbial ecosystems
DEFF Research Database (Denmark)
Revsbech, Niels Peter; Risgaard-Petersen, N.; Schramm, Andreas
2006-01-01
Abstract New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about n...
A NONHYDROSTATIC NUMERICAL MODEL FOR DENSITY STRATIFIED FLOW AND ITS APPLICATIONS
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
A modular numerical model was developed for simulating density-stratified flow in domains with irregular bottom topography. The model was designed for examining interactions between stratified flow and topography, e.g., tidally driven flow over two-dimensional sills or internal solitary waves propagating over a shoaling bed. The model was based on the non-hydrostatic vorticity-stream function equations for a continuously stratified fluid in a rotating frame. A self-adaptive grid was adopted in the vertical coordinate, the Alternative Direction Implicit (ADI) scheme was used for the time marching equations while the Poisson equation for stream-function was solved based on the Successive Over Relaxation (SOR) iteration with the Chebyshev acceleration. The numerical techniques were described and three applications of the model were presented.
Zilitinkevich, S. S.; Elperin, T.; Kleeorin, N.; Rogachevskii, I.; Esau, I.
2013-03-01
Here we advance the physical background of the energy- and flux-budget turbulence closures based on the budget equations for the turbulent kinetic and potential energies and turbulent fluxes of momentum and buoyancy, and a new relaxation equation for the turbulent dissipation time scale. The closure is designed for stratified geophysical flows from neutral to very stable and accounts for the Earth's rotation. In accordance with modern experimental evidence, the closure implies the maintaining of turbulence by the velocity shear at any gradient Richardson number Ri, and distinguishes between the two principally different regimes: "strong turbulence" at {Ri ≪ 1} typical of boundary-layer flows and characterized by the practically constant turbulent Prandtl number Pr T; and "weak turbulence" at Ri > 1 typical of the free atmosphere or deep ocean, where Pr T asymptotically linearly increases with increasing Ri (which implies very strong suppression of the heat transfer compared to the momentum transfer). For use in different applications, the closure is formulated at different levels of complexity, from the local algebraic model relevant to the steady-state regime of turbulence to a hierarchy of non-local closures including simpler down-gradient models, presented in terms of the eddy viscosity and eddy conductivity, and a general non-gradient model based on prognostic equations for all the basic parameters of turbulence including turbulent fluxes.
Cofinitely weak supplemented modules
Alizade, Rafail; Büyükaşık, Engin
2003-01-01
We prove that a module M is cofinitely weak supplemented or briefly cws (i.e., every submodule N of M with M/N finitely generated, has a weak supplement) if and only if every maximal submodule has a weak supplement. If M is a cws-module then every M-generated module is a cws-module. Every module is cws if and only if the ring is semilocal. We study also modules, whose finitely generated submodules have weak supplements.
Turbulence energetics in stably stratified geophysical flows: strong and weak mixing regimes
Zilitinkevich, S S; Kleeorin, N; Rogachevskii, I; Esau, I; Mauritsen, T; Miles, M W
2008-01-01
Traditionally, turbulence energetics is characterized by turbulent kinetic energy (TKE) and modelled using solely the TKE budget equation. In stable stratification, TKE is generated by the velocity shear and expended through viscous dissipation and work against buoyancy forces. The effect of stratification is characterized by the ratio of the buoyancy gradient to squared shear, called Richardson number, Ri. It is widely believed that at Ri exceeding a critical value, Ric, local shear cannot maintain turbulence, and the flow becomes laminar. We revise this concept by extending the energy analysis to turbulent potential and total energies (TPE and TTE = TKE + TPE), consider their budget equations, and conclude that TTE is a conservative parameter maintained by shear in any stratification. Hence there is no "energetics Ric", in contrast to the hydrodynamic-instability threshold, Ric-instability, whose typical values vary from 0.25 to 1. We demonstrate that this interval, 0.25>1, clarify principal difference betw...
Institute of Scientific and Technical Information of China (English)
丁夏畦; 罗佩珠
2004-01-01
In this paper the authors introduce some new ideas on generalized numbers and generalized weak functions. They prove that the product of any two weak functions is a generalized weak function. So in particular they solve the problem of the multiplication of two generalized functions.
Drainage in a model stratified porous medium
Datta, Sujit S; 10.1209/0295-5075/101/14002
2013-01-01
We show that when a non-wetting fluid drains a stratified porous medium at sufficiently small capillary numbers Ca, it flows only through the coarsest stratum of the medium; by contrast, above a threshold Ca, the non-wetting fluid is also forced laterally, into part of the adjacent, finer strata. The spatial extent of this partial invasion increases with Ca. We quantitatively understand this behavior by balancing the stratum-scale viscous pressure driving the flow with the capillary pressure required to invade individual pores. Because geological formations are frequently stratified, we anticipate that our results will be relevant to a number of important applications, including understanding oil migration, preventing groundwater contamination, and sub-surface CO$_{2}$ storage.
Stably Stratified Flow in a Shallow Valley
Mahrt, L.
2017-01-01
Stratified nocturnal flow above and within a small valley of approximately 12-m depth and a few hundred metres width is examined as a case study, based on a network of 20 sonic anemometers and a central 20-m tower with eight levels of sonic anemometers. Several regimes of stratified flow over gentle topography are conceptually defined for organizing the data analysis and comparing with the existing literature. In our case study, a marginal cold pool forms within the shallow valley in the early evening but yields to larger ambient wind speeds after a few hours, corresponding to stratified terrain-following flow where the flow outside the valley descends to the valley floor. The terrain-following flow lasts about 10 h and then undergoes transition to an intermittent marginal cold pool towards the end of the night when the larger-scale flow collapses. During this 10-h period, the stratified terrain-following flow is characterized by a three-layer structure, consisting of a thin surface boundary layer of a few metres depth on the valley floor, a deeper boundary layer corresponding to the larger-scale flow, and an intermediate transition layer with significant wind-directional shear and possible advection of lee turbulence that is generated even for the gentle topography of our study. The flow in the valley is often modulated by oscillations with a typical period of 10 min. Cold events with smaller turbulent intensity and duration of tens of minutes move through the observational domain throughout the terrain-following period. One of these events is examined in detail.
Multi Dimensional CTL and Stratified Datalog
Directory of Open Access Journals (Sweden)
Theodore Andronikos
2010-02-01
Full Text Available In this work we define Multi Dimensional CTL (MD-CTL in short by extending CTL which is thedominant temporal specification language in practice. The need for Multi Dimensional CTL is mainlydue to the advent of semi-structured data. The common path nature of CTL and XPath which provides asuitable model for semi-structured data, has caused the emergence of work on specifying a relation amongthem aiming at exploiting the nice properties of CTL. Although the advantages of such an approach havealready been noticed [36, 26, 5], no formal definition of MD-CTL has been given. The goal of this workis twofold; a we define MD-CTL and prove that the “nice” properties of CTL (linear model checking andbounded model property transfer also to MD-CTL, b we establish new results on stratified Datalog. Inparticular, we define a fragment of stratified Datalog called Multi Branching Temporal (MBT in shortprograms that has the same expressive power as MD-CTL. We prove that by devising a linear translationbetween MBT and MD-CTL. We actually give the exact translation rules for both directions. We furtherbuild on this relation to prove that query evaluation is linear and checking satisfiability, containment andequivalence are EXPTIME–complete for MBT programs. The class MBT is the largest fragment of stratifiedDatalog for which such results exist in the literature.
Thermal mixing in a stratified environment
Kraemer, Damian; Cotel, Aline
1999-11-01
Laboratory experiments of a thermal impinging on a stratified interface have been performed. The thermal was released from a cylindrical reservoir located at the bottom of a Lucite tank. The stratified interface was created by filling the tank with two different saline solutions. The density of the lower layer is greater than that of the upper layer and the thermal fluid, thereby creating a stable stratification. A pH indicator, phenolphthalein, is used to visualize and quantify the amount of mixing produced by the impingement of the thermal at the interface. The upper layer contains a mixture of water, salt and sodium hydroxide. The thermal fluid is composed of water, sulfuric acid and phenolphthalein. When the thermal entrains and mixes fluid from the upper layer, a chemical reaction takes place, and the resulting mixed fluid is now visible. The ratio of base to acid, called the equivalence ratio, was varied throughout the experiments, as well as the Richardson number. The Richardson number is the ratio of potential to kinetic energy, and is based on the thermal quantities at the interface. Results indicate that the amount of mixing produced is proportional to the Richardson number raised to the -3/2 power. Previous experiments (Zhang and Cotel 1999) revealed that the entrainment rate of a thermal in a stratified environment follows the same power law.
Are Superfluid Vortices in Pulsars Violating the Weak Equivalence Principle?
de Matos, Clovis Jacinto
2010-01-01
In the present paper we argue that timing irregularities in pulsars, like glitches and timing noise, could be associated with the violation of the weak equivalence principle for vortices in the superfluid core of rotating neutron stars.
Nonlinear gravity-wave interactions in stratified turbulence
Remmel, Mark; Sukhatme, Jai; Smith, Leslie M.
2014-04-01
To investigate the dynamics of gravity waves in stratified Boussinesq flows, a model is derived that consists of all three-gravity-wave-mode interactions (the GGG model), excluding interactions involving the vortical mode. The GGG model is a natural extension of weak turbulence theory that accounts for exact three-gravity-wave resonances. The model is examined numerically by means of random, large-scale, high-frequency forcing. An immediate observation is a robust growth of the so-called vertically sheared horizontal flow (VSHF). In addition, there is a forward transfer of energy and equilibration of the nonzero-frequency (sometimes called "fast") gravity-wave modes. These results show that gravity-wave-mode interactions by themselves are capable of systematic interscale energy transfer in a stratified fluid. Comparing numerical simulations of the GGG model and the full Boussinesq system, for the range of Froude numbers ( Fr) considered (0.05 ≤ Fr ≤ 1), in both systems the VSHF is hardest to resolve. When adequately resolved, VSHF growth is more vigorous in the GGG model. Furthermore, a VSHF is observed to form in milder stratification scenarios in the GGG model than the full Boussinesq system. Finally, fully three-dimensional nonzero-frequency gravity-wave modes equilibrate in both systems and their scaling with vertical wavenumber follows similar power-laws. The slopes of the power-laws obtained depend on Fr and approach -2 (from above) at Fr = 0.05, which is the strongest stratification that can be properly resolved with our computational resources.
Rotationally symmetric viscous gas flows
Weigant, W.; Plotnikov, P. I.
2017-03-01
The Dirichlet boundary value problem for the Navier-Stokes equations of a barotropic viscous compressible fluid is considered. The flow region and the data of the problem are assumed to be invariant under rotations about a fixed axis. The existence of rotationally symmetric weak solutions for all adiabatic exponents from the interval (γ*,∞) with a critical exponent γ* < 4/3 is proved.
Childs, Peter R N
2010-01-01
Rotating flow is critically important across a wide range of scientific, engineering and product applications, providing design and modeling capability for diverse products such as jet engines, pumps and vacuum cleaners, as well as geophysical flows. Developed over the course of 20 years' research into rotating fluids and associated heat transfer at the University of Sussex Thermo-Fluid Mechanics Research Centre (TFMRC), Rotating Flow is an indispensable reference and resource for all those working within the gas turbine and rotating machinery industries. Traditional fluid and flow dynamics
On Weakly Semicommutative Rings*
Institute of Scientific and Technical Information of China (English)
CHEN WEI-XING; CUI SHU-YING
2011-01-01
A ring R is said to be weakly scmicommutative if for any a, b ∈ R,ab = 0 implies aRb C_ Nil(R), where Nil(R) is the set of all nilpotcnt elements in R.In this note, we clarify the relationship between weakly semicommutative rings and NI-rings by proving that the notion of a weakly semicommutative ring is a proper generalization of NI-rings. We say that a ring R is weakly 2-primal if the set of nilpotent elements in R coincides with its Levitzki radical, and prove that if R is a weakly 2-primal ring which satisfies oα-condition for an endomorphism α of R (that is, ab = 0 （←→） aα(b) ＝ 0 where a, b ∈ R) then the skew polynomial ring R[π; αα]is a weakly 2-primal ring, and that if R is a ring and I is an ideal of R such that I and R/I are both weakly semicommutative then R is weakly semicommutative.Those extend the main results of Liang et al. 2007 (Taiwanese J. Math., 11(5)(2007),1359-1368) considerably. Moreover, several new results about weakly semicommutative rings and NI-rings are included.
Inverse scattering of dispersive stratified structures
Skaar, Johannes
2012-01-01
We consider the inverse scattering problem of retrieving the structural parameters of a stratified medium consisting of dispersive materials, given knowledge of the complex reflection coefficient in a finite frequency range. It is shown that the inverse scattering problem does not have a unique solution in general. When the dispersion is sufficiently small, such that the time-domain Fresnel reflections have durations less than the round-trip time in the layers, the solution is unique and can be found by layer peeling. Numerical examples with dispersive and lossy media are given, demonstrating the usefulness of the method for e.g. THz technology.
Schulz, E.; Schuttelaars, H.M.; Grawe, U.; Burchard, H.
2015-01-01
The dependency of the estuarine circulation on the depth-to-width ratio of a periodically, weakly stratified tidal estuary is systematically investigated here for the first time. Currents, salinity, and other properties are simulated by means of the General Estuarine Transport Model (GETM) in cross-
Rotational effects on the negative magnetic pressure instability
Losada, Illa R; Kleeorin, N; Mitra, Dhrubaditya; Rogachevskii, I
2012-01-01
The surface layers of the Sun are strongly stratified. In the presence of turbulence with a weak mean magnetic field, a large-scale instability resulting in the formation of non-uniform magnetic structures, can be excited over the scale of many turbulent eddies or convection cells. This instability is caused by a negative contribution of turbulence to the effective (mean-field) magnetic pressure and has previously been discussed in connection with the formation of active regions and perhaps sunspots. We want to understand the effects of rotation on this instability in both two and three dimensions. We use mean-field magnetohydrodynamics in a parameter regime in which the properties of the negative effective magnetic pressure instability have previously been found to be in agreement with those of direct numerical simulations. We find that the instability is suppressed already for relatively slow rotation with Coriolis numbers (i.e. inverse Rossby numbers) around 0.2. The suppression is strongest at the equator...
Lekner, John
2008-01-01
Any free-particle wavepacket solution of Schrodinger's equation can be converted by differentiations to wavepackets rotating about the original direction of motion. The angular momentum component along the motion associated with this rotation is an integral multiple of [h-bar]. It is an "intrinsic" angular momentum: independent of origin and…
On regular rotating black holes
Torres, R.; Fayos, F.
2017-01-01
Different proposals for regular rotating black hole spacetimes have appeared recently in the literature. However, a rigorous analysis and proof of the regularity of this kind of spacetimes is still lacking. In this note we analyze rotating Kerr-like black hole spacetimes and find the necessary and sufficient conditions for the regularity of all their second order scalar invariants polynomial in the Riemann tensor. We also show that the regularity is linked to a violation of the weak energy conditions around the core of the rotating black hole.
On regular rotating black holes
Torres, Ramon
2016-01-01
Different proposals for regular rotating black hole spacetimes have appeared recently in the literature. However, a rigorous analysis and proof of the regularity of this kind of spacetimes is still lacking. In this note we analyze rotating Kerr-like black hole spacetimes and find the necessary and sufficient conditions for the regularity of all their second order scalar invariants polynomial in the Riemann tensor. We also show that the regularity is linked to a violation of the weak energy conditions around the core of the rotating black hole.
Idiopathic isolated orbicularis weakness
MacVie, O P; Majid, M A; Husssin, H M; Ung, T; Manners, R M; Ormerod, I; Pawade, J; Harrad, R A
2012-01-01
Purpose Orbicularis weakness is commonly associated with seventh nerve palsy or neuromuscular and myopathic conditions such as myotonic dystrophy and myasethenia gravis. We report four cases of idiopathic isolated orbicularis weakness. Methods All four cases were female and the presenting symptoms of ocular irritation and epiphora had been present for over 7 years in three patients. All patients had lagophthalmos and three had ectropion. Three patients underwent full investigations which excluded known causes of orbicularis weakness. Two patients underwent oribularis oculi muscle biopsy and histological confirmation of orbicularis atrophy. Results All patients underwent surgery to specifically address the orbicularis weakness with satisfactory outcomes and alleviation of symptoms in all cases. Isolated orbicularis weakness may be a relatively common entity that is frequently overlooked. Conclusion Early recognition of this condition may lead to better management and prevent patients undergoing unnecessary surgical procedures. PMID:22322997
Rotational Baroclinic Adjustment
DEFF Research Database (Denmark)
Holtegård Nielsen, Steen Morten
In stratified waters like those around Denmark there is a close correlation between the biology of the water masses and their structure and currents; this is known as dynamic biologicaloceanography. The currents are particularly strong near the fronts, which can be seen in several places throughout...... the reciprocal of the socalled Coriolis parameter, and the length scale, which is known as the Rossby radius. Also, because of their limited width currents influenced by rotation are quite persistent. The flow which results from the introduction of a surface level discontinuity across a wide channel is discussed...... of the numerical model a mechanism for the generation of along-frontal instabilities and eddies is suggested. Also, the effect of an irregular bathymetry is studied.Together with observations of wind and water levels some of the oceanographical observations from the old lightvessels are used to study...
Weak Lie symmetry and extended Lie algebra
Energy Technology Data Exchange (ETDEWEB)
Goenner, Hubert [Institute for Theoretical Physics, Friedrich-Hund-Platz 1, University of Goettingen, D-37077 Gottingen (Germany)
2013-04-15
The concept of weak Lie motion (weak Lie symmetry) is introduced. Applications given exhibit a reduction of the usual symmetry, e.g., in the case of the rotation group. In this context, a particular generalization of Lie algebras is found ('extended Lie algebras') which turns out to be an involutive distribution or a simple example for a tangent Lie algebroid. Riemannian and Lorentz metrics can be introduced on such an algebroid through an extended Cartan-Killing form. Transformation groups from non-relativistic mechanics and quantum mechanics lead to such tangent Lie algebroids and to Lorentz geometries constructed on them (1-dimensional gravitational fields).
Vassiliev, Dmitri
2017-04-01
We consider an infinite three-dimensional elastic continuum whose material points experience no displacements, only rotations. This framework is a special case of the Cosserat theory of elasticity. Rotations of material points are described mathematically by attaching to each geometric point an orthonormal basis that gives a field of orthonormal bases called the coframe. As the dynamical variables (unknowns) of our theory, we choose the coframe and a density. We write down the general dynamic variational functional for our rotational theory of elasticity, assuming our material to be physically linear but the kinematic model geometrically nonlinear. Allowing geometric nonlinearity is natural when dealing with rotations because rotations in dimension three are inherently nonlinear (rotations about different axes do not commute) and because there is no reason to exclude from our study large rotations such as full turns. The main result of the talk is an explicit construction of a class of time-dependent solutions that we call plane wave solutions; these are travelling waves of rotations. The existence of such explicit closed-form solutions is a non-trivial fact given that our system of Euler-Lagrange equations is highly nonlinear. We also consider a special case of our rotational theory of elasticity which in the stationary setting (harmonic time dependence and arbitrary dependence on spatial coordinates) turns out to be equivalent to a pair of massless Dirac equations. The talk is based on the paper [1]. [1] C.G.Boehmer, R.J.Downes and D.Vassiliev, Rotational elasticity, Quarterly Journal of Mechanics and Applied Mathematics, 2011, vol. 64, p. 415-439. The paper is a heavily revised version of preprint https://arxiv.org/abs/1008.3833
Energy Technology Data Exchange (ETDEWEB)
Bambi, Cosimo, E-mail: bambi@fudan.edu.cn; Modesto, Leonardo, E-mail: lmodesto@fudan.edu.cn
2013-04-25
The formation of spacetime singularities is a quite common phenomenon in General Relativity and it is regulated by specific theorems. It is widely believed that spacetime singularities do not exist in Nature, but that they represent a limitation of the classical theory. While we do not yet have any solid theory of quantum gravity, toy models of black hole solutions without singularities have been proposed. So far, there are only non-rotating regular black holes in the literature. These metrics can be hardly tested by astrophysical observations, as the black hole spin plays a fundamental role in any astrophysical process. In this Letter, we apply the Newman–Janis algorithm to the Hayward and to the Bardeen black hole metrics. In both cases, we obtain a family of rotating solutions. Every solution corresponds to a different matter configuration. Each family has one solution with special properties, which can be written in Kerr-like form in Boyer–Lindquist coordinates. These special solutions are of Petrov type D, they are singularity free, but they violate the weak energy condition for a non-vanishing spin and their curvature invariants have different values at r=0 depending on the way one approaches the origin. We propose a natural prescription to have rotating solutions with a minimal violation of the weak energy condition and without the questionable property of the curvature invariants at the origin.
Weak decays. [Lectures, phenomenology
Energy Technology Data Exchange (ETDEWEB)
Wojcicki, S.
1978-11-01
Lectures are given on weak decays from a phenomenological point of view, emphasizing new results and ideas and the relation of recent results to the new standard theoretical model. The general framework within which the weak decay is viewed and relevant fundamental questions, weak decays of noncharmed hadrons, decays of muons and the tau, and the decays of charmed particles are covered. Limitation is made to the discussion of those topics that either have received recent experimental attention or are relevant to the new physics. (JFP) 178 references
Weakly asymptotically hyperbolic manifolds
Allen, Paul T; Lee, John M; Allen, Iva Stavrov
2015-01-01
We introduce a class of "weakly asymptotically hyperbolic" geometries whose sectional curvatures tend to $-1$ and are $C^0$, but are not necessarily $C^1$, conformally compact. We subsequently investigate the rate at which curvature invariants decay at infinity, identifying a conformally invariant tensor which serves as an obstruction to "higher order decay" of the Riemann curvature operator. Finally, we establish Fredholm results for geometric elliptic operators, extending the work of Rafe Mazzeo and John M. Lee to this setting. As an application, we show that any weakly asymptotically hyperbolic metric is conformally related to a weakly asymptotically hyperbolic metric of constant negative curvature.
Stratified growth in Pseudomonas aeruginosa biofilms
DEFF Research Database (Denmark)
Werner, E.; Roe, F.; Bugnicourt, A.;
2004-01-01
In this study, stratified patterns of protein synthesis and growth were demonstrated in Pseudomonas aeruginosa biofilms. Spatial patterns of protein synthetic activity inside biofilms were characterized by the use of two green fluorescent protein (GFP) reporter gene constructs. One construct...... carried an isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible gfpmut2 gene encoding a stable GFP. The second construct carried a GFP derivative, gfp-AGA, encoding an unstable GFP under the control of the growth-rate-dependent rrnBp(1) promoter. Both GFP reporters indicated that active protein...... of oxygen limitation in the biofilm. Oxygen microelectrode measurements showed that oxygen only penetrated approximately 50 mum into the biofilm. P. aeruginosa was incapable of anaerobic growth in the medium used for this investigation. These results show that while mature P. aeruginosa biofilms contain...
Bayesian Stratified Sampling to Assess Corpus Utility
Hochberg, J; Thomas, T; Hall, S; Hochberg, Judith; Scovel, Clint; Thomas, Timothy; Hall, Sam
1998-01-01
This paper describes a method for asking statistical questions about a large text corpus. We exemplify the method by addressing the question, "What percentage of Federal Register documents are real documents, of possible interest to a text researcher or analyst?" We estimate an answer to this question by evaluating 200 documents selected from a corpus of 45,820 Federal Register documents. Stratified sampling is used to reduce the sampling uncertainty of the estimate from over 3100 documents to fewer than 1000. The stratification is based on observed characteristics of real documents, while the sampling procedure incorporates a Bayesian version of Neyman allocation. A possible application of the method is to establish baseline statistics used to estimate recall rates for information retrieval systems.
Masada, Youhei
2016-01-01
We report the first successful simulation of spontaneous formation of surface magnetic structures from a large-scale dynamo by strongly-stratified thermal convection in Cartesian geometry. The large-scale dynamo observed in our strongly-stratified model has physical properties similar to those in earlier weakly-stratified convective dynamo simulations, indicating that the $\\alpha^2$-type mechanism is responsible for it. Additionally to the large-scale dynamo, we find that large-scale structures of the vertical magnetic field are spontaneously formed in the convection zone surface only for the case of strongly-stratified atmosphere. The organization of the vertical magnetic field proceeds in the upper convection zone within tens of convective turn-over time and band-like bipolar structures are recurrently-appeared in the dynamo-saturated stage. We examine possibilities of several candidates as the origin of the surface magnetic structure formation, and then suggest the existence of an as-yet-unknown mechanism ...
Stratified scaffold design for engineering composite tissues.
Mosher, Christopher Z; Spalazzi, Jeffrey P; Lu, Helen H
2015-08-01
A significant challenge to orthopaedic soft tissue repair is the biological fixation of autologous or allogeneic grafts with bone, whereby the lack of functional integration between such grafts and host bone has limited the clinical success of anterior cruciate ligament (ACL) and other common soft tissue-based reconstructive grafts. The inability of current surgical reconstruction to restore the native fibrocartilaginous insertion between the ACL and the femur or tibia, which minimizes stress concentration and facilitates load transfer between the soft and hard tissues, compromises the long-term clinical functionality of these grafts. To enable integration, a stratified scaffold design that mimics the multiple tissue regions of the ACL interface (ligament-fibrocartilage-bone) represents a promising strategy for composite tissue formation. Moreover, distinct cellular organization and phase-specific matrix heterogeneity achieved through co- or tri-culture within the scaffold system can promote biomimetic multi-tissue regeneration. Here, we describe the methods for fabricating a tri-phasic scaffold intended for ligament-bone integration, as well as the tri-culture of fibroblasts, chondrocytes, and osteoblasts on the stratified scaffold for the formation of structurally contiguous and compositionally distinct regions of ligament, fibrocartilage and bone. The primary advantage of the tri-phasic scaffold is the recapitulation of the multi-tissue organization across the native interface through the layered design. Moreover, in addition to ease of fabrication, each scaffold phase is similar in polymer composition and therefore can be joined together by sintering, enabling the seamless integration of each region and avoiding delamination between scaffold layers.
Stratified sampling design based on data mining.
Kim, Yeonkook J; Oh, Yoonhwan; Park, Sunghoon; Cho, Sungzoon; Park, Hayoung
2013-09-01
To explore classification rules based on data mining methodologies which are to be used in defining strata in stratified sampling of healthcare providers with improved sampling efficiency. We performed k-means clustering to group providers with similar characteristics, then, constructed decision trees on cluster labels to generate stratification rules. We assessed the variance explained by the stratification proposed in this study and by conventional stratification to evaluate the performance of the sampling design. We constructed a study database from health insurance claims data and providers' profile data made available to this study by the Health Insurance Review and Assessment Service of South Korea, and population data from Statistics Korea. From our database, we used the data for single specialty clinics or hospitals in two specialties, general surgery and ophthalmology, for the year 2011 in this study. Data mining resulted in five strata in general surgery with two stratification variables, the number of inpatients per specialist and population density of provider location, and five strata in ophthalmology with two stratification variables, the number of inpatients per specialist and number of beds. The percentages of variance in annual changes in the productivity of specialists explained by the stratification in general surgery and ophthalmology were 22% and 8%, respectively, whereas conventional stratification by the type of provider location and number of beds explained 2% and 0.2% of variance, respectively. This study demonstrated that data mining methods can be used in designing efficient stratified sampling with variables readily available to the insurer and government; it offers an alternative to the existing stratification method that is widely used in healthcare provider surveys in South Korea.
Information content of household-stratified epidemics
Directory of Open Access Journals (Sweden)
T.M. Kinyanjui
2016-09-01
Full Text Available Household structure is a key driver of many infectious diseases, as well as a natural target for interventions such as vaccination programs. Many theoretical and conceptual advances on household-stratified epidemic models are relatively recent, but have successfully managed to increase the applicability of such models to practical problems. To be of maximum realism and hence benefit, they require parameterisation from epidemiological data, and while household-stratified final size data has been the traditional source, increasingly time-series infection data from households are becoming available. This paper is concerned with the design of studies aimed at collecting time-series epidemic data in order to maximize the amount of information available to calibrate household models. A design decision involves a trade-off between the number of households to enrol and the sampling frequency. Two commonly used epidemiological study designs are considered: cross-sectional, where different households are sampled at every time point, and cohort, where the same households are followed over the course of the study period. The search for an optimal design uses Bayesian computationally intensive methods to explore the joint parameter-design space combined with the Shannon entropy of the posteriors to estimate the amount of information in each design. For the cross-sectional design, the amount of information increases with the sampling intensity, i.e., the designs with the highest number of time points have the most information. On the other hand, the cohort design often exhibits a trade-off between the number of households sampled and the intensity of follow-up. Our results broadly support the choices made in existing epidemiological data collection studies. Prospective problem-specific use of our computational methods can bring significant benefits in guiding future study designs.
Hosoya, Akio
2010-01-01
We develop a formal theory of the weak values with emphasis on the consistency conditions and a probabilistic interpretation in the counter-factual processes. We present the condition for the choice of the post-selected state to give a negative weak value of a given projection operator and strange values of an observable in general. The general framework is applied to Hardy's paradox and the spin $1/2$ system to explicitly address the issues of counter-factuality and strange weak values. The counter-factual arguments which characterize the paradox specifies the pre-selected state and a complete set of the post-selected states clarifies how the strange weak values emerge.
On strongly interacting internal waves in a rotating ocean and coupled Ostrovsky equations.
Alias, A; Grimshaw, R H J; Khusnutdinova, K R
2013-06-01
In the weakly nonlinear limit, oceanic internal solitary waves for a single linear long wave mode are described by the KdV equation, extended to the Ostrovsky equation in the presence of background rotation. In this paper we consider the scenario when two different linear long wave modes have nearly coincident phase speeds and show that the appropriate model is a system of two coupled Ostrovsky equations. These are systematically derived for a density-stratified ocean. Some preliminary numerical simulations are reported which show that, in the generic case, initial solitary-like waves are destroyed and replaced by two coupled nonlinear wave packets, being the counterpart of the same phenomenon in the single Ostrovsky equation.
A 3D Spectral Anelastic Hydrodynamic Code for Shearing, Stratified Flows
Barranco, J A; Barranco, Joseph A.; Marcus, Philip S.
2005-01-01
We have developed a three-dimensional (3D) spectral hydrodynamic code to study vortex dynamics in rotating, shearing, stratified systems (e.g. the atmosphere of gas giant planets, protoplanetary disks around newly forming protostars). The time-independent background state is stably stratified in the vertical direction and has a unidirectional linear shear flow aligned with one horizontal axis. Superposed on this background state is an unsteady, subsonic flow that is evolved with the Euler equations subject to the anelastic approximation to filter acoustic phenomena. A Fourier-Fourier basis in a set of quasi-Lagrangian coordinates that advect with the background shear is used for spectral expansions in the two horizontal directions. For the vertical direction, two different sets of basis functions have been implemented: (1) Chebyshev polynomials on a truncated, finite domain, and (2) rational Chebyshev functions on an infinite domain. Use of this latter set is equivalent to transforming the infinite domain to ...
Institute of Scientific and Technical Information of China (English)
黄茂松; 王浩然; 刘怡林
2012-01-01
Weak interlayer and rainfall have great effects on slope stability. The weak interlayer may change the failure mechanism and reduce the slope stability. The rainfall will make the slope more instable and may even induce weak interlayer formed in the slope. However, simple and rational evaluation methods for such a slope stability problem have not been proposed so far. In this paper, based on the upper bound limit analysis method, a new failure mechanism consisting of rigid blocks undergoing impending rotational or translational movements is proposed to study the slope stability under rainfall condition. Rainfall-induced change of pore water pressure in slopes is analyzed by means of the transient seepage finite element analysis. The saturation line and the soil strength after rainfall are then considered and incorporated into the limit analysis. The proposed rotation-translation combined mechanism is finally verified by comparisons with the elasto-plasticity finite element method. The comparisons show that the proposed mechanism improves the efficiency of the previously-developed rigid block mechanism to account for the presence of weak interlayer in the slopes and can be used as a simple evaluation method for the engineering design.%软弱夹层、降雨等因素对边坡的整体稳定性有着很大的影响。软弱夹层会使得边坡的破坏形式发生改变，从而降低其稳定性；而降雨不但会使得边坡的稳定性变差，甚至有可能使边坡内形成更加软弱的夹层。但是目前尚未有一个简单合理的方法来分析这种类型边坡的稳定性。基于转动一平动组合破坏机构，提出了一种用于含软弱夹层边坡降雨入渗稳定性极限分析上限法。采用非饱和非稳定渗流分析计算得到的浸润线位置结合降雨后的土体强度及组合破坏机构分析含软弱夹层边坡降雨入渗的稳定性，通过与弹塑性有限元数值模拟结果进行对比，验证
Caleo, Andrea; Balbus, Steven A.
2016-04-01
Barotropic rotation and radiative equilibrium are mutually incompatible in stars. The issue is often addressed by allowing for a meridional circulation, but this is not devoid of theoretical complications. Models of rotation in the Sun which maintain strict radiative equilibrium, making use of the observation that the Sun is not in a state of barotropic rotation, have recently been suggested. To investigate the dynamical behaviour of these solutions, we study the local stability of stratified, weakly magnetized, differentially rotating fluids to non-axisymmetric perturbations. Finite heat conductivity, kinematic viscosity, and resistivity are present. The evolution of local embedded perturbations is governed by a set of coupled, ordinary differential equations with time-dependent coefficients. Two baroclinic models of rotation for the upper radiative zone and tachocline are studied: (i) an interpolation based on helioseismology data, (ii) a theoretical solution directly compatible with radiative equilibrium. The growth of the local Goldreich-Schubert-Fricke instability appears to be suppressed, largely because of the viscosity. An extensive exploration of wavenumber space is carried out, with and without a magnetic field. Although we easily find classical local instabilities when they ought formally to be present, for the Sun the analysis reveals neither unstable solutions, nor even solutions featuring a large transient growth. We have not ruled out larger scale or non-linear instabilities, nor have we rigorously proven local stability. But rotational configurations in close agreement with observations, generally thought to be vulnerable to the classic local Goldreich-Schubert-Fricke instability, do appear to be locally stable under rather general circumstances.
Fishing and the oceanography of a stratified shelf sea
Sharples, Jonathan; Ellis, Jim R.; Nolan, Glenn; Scott, Beth E.
2013-10-01
Fishing vessel position data from the Vessel Monitoring System (VMS) were used to investigate fishing activity in the Celtic Sea, a seasonally-stratifying, temperate region on the shelf of northwest Europe. The spatial pattern of fishing showed that three main areas are targeted: (1) the Celtic Deep (an area of deeper water with fine sediments), (2) the shelf edge, and (3) an area covering several large seabed banks in the central Celtic Sea. Data from each of these regions were analysed to examine the contrasting seasonality of fishing activity, and to highlight where the spring-neap tidal cycle appears to be important to fishing. The oceanographic characteristics of the Celtic Sea were considered alongside the distribution and timing of fishing, illustrating likely contrasts in the underlying environmental drivers of the different fished regions. In the central Celtic Sea, fishing mainly occurred during the stratified period between April and August. Based on evidence provided in other papers of this Special Issue, we suggest that the fishing in this area is supported by (1) a broad increase in primary production caused by lee-waves generated by seabed banks around spring tides driving large supplies of nutrients into the photic zone, and (2) greater concentrations of zooplankton within the region influenced by the seabed banks and elevated primary production. In contrast, while the shelf edge is a site of elevated surface chlorophyll, previous work has suggested that the periodic mixing generated by an internal tide at the shelf edge alters the size-structure of the phytoplankton community which fish larvae from the spawning stocks along the shelf edge are able to exploit. The fishery for Nephrops norvegicus in the Celtic Deep was the only one to show a significant spring-neap cycle, possibly linked to Nephrops foraging outside their burrows less during spring tides. More tentatively, the fishery for Nephrops correlated most strongly with a localised shift in
Double criticality and the two-way Boussinesq equation in stratified shallow water hydrodynamics
Bridges, Thomas J.; Ratliff, Daniel J.
2016-06-01
Double criticality and its nonlinear implications are considered for stratified N-layer shallow water flows with N = 1, 2, 3. Double criticality arises when the linearization of the steady problem about a uniform flow has a double zero eigenvalue. We find that there are two types of double criticality: non-semisimple (one eigenvector and one generalized eigenvector) and semi-simple (two independent eigenvectors). Using a multiple scales argument, dictated by the type of singularity, it is shown that the weakly nonlinear problem near double criticality is governed by a two-way Boussinesq equation (non-semisimple case) and a coupled Korteweg-de Vries equation (semisimple case). Parameter values and reduced equations are constructed for the examples of two-layer and three-layer stratified shallow water hydrodynamics.
Hotta, H.; Rempel, M.; Yokoyama, T.
2015-01-01
We present a high-resolution, highly stratified numerical simulation of rotating thermal convection in a spherical shell. Our aim is to study in detail the processes that can maintain a near surface shear layer (NSSL) as inferred from helioseismology. Using the reduced speed of sound technique, we can extend our global convection simulation to 0.99 R ⊙ and include, near the top of our domain, small-scale convection with short timescales that is only weakly influenced by rotation. We find the formation of an NSSL preferentially in high latitudes in the depth range of r = 0.95-0.975 R ⊙. The maintenance mechanisms are summarized as follows. Convection under the weak influence of rotation leads to Reynolds stresses that transport angular momentum radially inward in all latitudes. This leads to the formation of a strong poleward-directed meridional flow and an NSSL, which is balanced in the meridional plane by forces resulting from the correlation of turbulent velocities. The origin of the required correlations depends to some degree on latitude. In high latitudes, a positive correlation is induced in the NSSL by the poleward meridional flow whose amplitude increases with the radius, while a negative correlation is generated by the Coriolis force in bulk of the convection zone. In low latitudes, a positive correlation results from rotationally aligned convection cells ("banana cells"). The force caused by these Reynolds stresses is in balance with the Coriolis force in the NSSL.
Joyal, André
2009-01-01
We define weak units in a semi-monoidal 2-category $\\CC$ as cancellable pseudo-idempotents: they are pairs $(I,\\alpha)$ where $I$ is an object such that tensoring with $I$ from either side constitutes a biequivalence of $\\CC$, and $\\alpha: I \\tensor I \\to I$ is an equivalence in $\\CC$. We show that this notion of weak unit has coherence built in: Theorem A: $\\alpha$ has a canonical associator 2-cell, which automatically satisfies the pentagon equation. Theorem B: every morphism of weak units is automatically compatible with those associators. Theorem C: the 2-category of weak units is contractible if non-empty. Finally we show (Theorem E) that the notion of weak unit is equivalent to the notion obtained from the definition of tricategory: $\\alpha$ alone induces the whole family of left and right maps (indexed by the objects), as well as the whole family of Kelly 2-cells (one for each pair of objects), satisfying the relevant coherence axioms.
Continuity in weak topology: higher order linear systems of ODE
Institute of Scientific and Technical Information of China (English)
ZHANG MeiRong
2008-01-01
We will introduce a type of Fredholm operators which are shown to have a certain continuity in weak topologies. From this, we will prove that the fundamental matrix solutions of k-th,k≥ 2, order linear systems of ordinary differential equations are continuous in coefficient matrixes with weak topologies. Consequently, Floquet multipliers and Lyapunov exponents for periodic systems are continuous in weak topologies. Moreover, for the scalar Hill's equations, Sturm-Liouville eigenvalues,periodic and anti-periodic eigenvalues, and rotation numbers are all continuous in potentials with weak topologies. These results will lead to many interesting variational problems.
Magnetic flux concentrations from turbulent stratified convection
Käpylä, P J; Kleeorin, N; Käpylä, M J; Rogachevskii, I
2015-01-01
(abridged) Context: The mechanisms that cause the formation of sunspots are still unclear. Aims: We study the self-organisation of initially uniform sub-equipartition magnetic fields by highly stratified turbulent convection. Methods: We perform simulations of magnetoconvection in Cartesian domains that are $8.5$-$24$ Mm deep and $34$-$96$ Mm wide. We impose either a vertical or a horizontal uniform magnetic field in a convection-driven turbulent flow. Results: We find that super-equipartition magnetic flux concentrations are formed near the surface with domain depths of $12.5$ and $24$ Mm. The size of the concentrations increases as the box size increases and the largest structures ($20$ Mm horizontally) are obtained in the 24 Mm deep models. The field strength in the concentrations is in the range of $3$-$5$ kG. The concentrations grow approximately linearly in time. The effective magnetic pressure measured in the simulations is positive near the surface and negative in the bulk of the convection zone. Its ...
Steady internal waves in an exponentially stratified two-layer fluid
Makarenko, Nikolay; Maltseva, Janna; Ivanova, Kseniya
2016-04-01
The problem on internal waves in a weakly stratified two-layered fluid is studied analytically. We suppose that the fluid possess exponential stratification in both the layers, and the fluid density has discontinuity jump at the interface. By that, we take into account the influence of weak continuous stratification outside of sharp pycnocline. The model equation of strongly nonlinear interfacial waves propagating along the pycnocline is considered. This equation extends approximate models [1-3] suggested for a two-layer fluid with one homogeneous layer. The derivation method uses asymptotic analysis of fully nonlinear Euler equations. The perturbation scheme involves the long wave procedure with a pair of the Boussinesq parameters. First of these parameters characterizes small density slope outside of pycnocline and the second one defines small density jump at the interface. Parametric range of solitary wave solutions is characterized, including extreme regimes such as plateau-shape solitary waves. This work was supported by RFBR (grant No 15-01-03942). References [1] N. Makarenko, J. Maltseva. Asymptotic models of internal stationary waves, J. Appl. Mech. Techn. Phys, 2008, 49(4), 646-654. [2] N. Makarenko, J. Maltseva. Phase velocity spectrum of internal waves in a weakly-stratified two-layer fluid, Fluid Dynamics, 2009, 44(2), 278-294. [3] N. Makarenko, J. Maltseva. An analytical model of large amplitude internal solitary waves, Extreme Ocean Waves, 2nd ed. Springer 2015, E.Pelinovsky and C.Kharif (Eds), 191-201.
Internal and vorticity waves in decaying stratified flows
Matulka, A.; Cano, D.
2009-04-01
Most predictive models fail when forcing at the Rossby deformation Radius is important and a large range of scales have to be taken into account. When mixing of reactants or pollutants has to be accounted, the range of scales spans from hundreds of Kilometers to the Bachelor or Kolmogorov sub milimiter scales. We present some theoretical arguments to describe the flow in terms of the three dimensional vorticity equations, using a lengthscale related to the vorticity (or enstrophy ) transport. Effect of intermittent eddies and non-homogeneity of diffusion are also key issues in the environment because both stratification and rotation body forces are important and cause anisotropy/non-homogeneity. These problems need further theoretical, numerical and observational work and one approach is to try to maximize the relevant geometrical information in order to understand and therefore predict these complex environmental dispersive flows. The importance of the study of turbulence structure and its relevance in diffusion of contaminants in environmental flows is clear when we see the effect of environmental disasters such as the Prestige oil spill or the Chernobil radioactive cloud spread in the atmosphere. A series of Experiments have been performed on a strongly stratified two layer fluid consisting of Brine in the bottom and freshwater above in a 1 square meter tank. The evolution of the vortices after the passage of a grid is video recorded and Particle tracking is applied on small pliolite particles floating at the interface. The combination of internal waves and vertical vorticity produces two separate time scales that may produce resonances. The vorticity is seen to oscilate in a complex way, where the frecuency decreases with time.
WEAK CONVERGENCE OF SOME SERIES
Institute of Scientific and Technical Information of China (English)
2000-01-01
This paper continues the study of [1] on weak functions.The weak convergence theory is investigated in complex analysis,Fourier transform and Mellin transform.A Mobius inverse formula of weak functions is obtained.
Non-uniqueness of Admissible Weak Solutions to Compressible Euler Systems with Source Terms
Luo, Tianwen; Xie, Chunjing; Xin, Zhouping
2015-01-01
We consider admissible weak solutions to the compressible Euler system with source terms, which include rotating shallow water system and the Euler system with damping as special examples. In the case of anti-symmetric sources such as rotations, for general piecewise Lipschitz initial densities and some suitably constructed initial momentum, we obtain infinitely many global admissible weak solutions. Furthermore, we construct a class of finite-states admissible weak solutions to the Euler sys...
DEFF Research Database (Denmark)
Kohlenbach, Ulrich Wilhelm
2002-01-01
We show that the so-called weak Markov's principle (WMP) which states that every pseudo-positive real number is positive is underivable in E-HA + AC. Since allows one to formalize (atl eastl arge parts of) Bishop's constructive mathematics, this makes it unlikely that WMP can be proved within the...
On closed weak supplemented modules
Institute of Scientific and Technical Information of China (English)
ZENG Qing-yi; SHI Mei-hua
2006-01-01
A module M is called closed weak supplemented if for any closed submodule N of M, there is a submodule K of M such that M=K+N and K(c)N＜＜M. Any direct summand of closed weak supplemented module is also closed weak supplemented.Any nonsingular image of closed weak supplemented module is closed weak supplemented. Nonsingular V-rings in which all nonsingular modules are closed weak supplemented are characterized in Section 4.
The nonlinear evolution of modes on unstable stratified shear layers
Blackaby, Nicholas; Dando, Andrew; Hall, Philip
1993-06-01
The nonlinear development of disturbances in stratified shear flows (having a local Richardson number of value less than one quarter) is considered. Such modes are initially fast growing but, like related studies, we assume that the viscous, non-parallel spreading of the shear layer results in them evolving in a linear fashion until they reach a position where their amplitudes are large enough and their growth rates have diminished sufficiently so that amplitude equations can be derived using weakly nonlinear and non-equilibrium critical-layer theories. Four different basic integro-differential amplitude equations are possible, including one due to a novel mechanism; the relevant choice of amplitude equation, at a particular instance, being dependent on the relative sizes of the disturbance amplitude, the growth rate of the disturbance, its wavenumber, and the viscosity of the fluid. This richness of choice of possible nonlinearities arises mathematically from the indicial Frobenius roots of the governing linear inviscid equation (the Taylor-Goldstein equation) not, in general, differing by an integer. The initial nonlinear evolution of a mode will be governed by an integro-differential amplitude equations with a cubic nonlinearity but the resulting significant increase in the size of the disturbance's amplitude leads on to the next stage of the evolution process where the evolution of the mode is governed by an integro-differential amplitude equations with a quintic nonlinearity. Continued growth of the disturbance amplitude is expected during this stage, resulting in the effects of nonlinearity spreading to outside the critical level, by which time the flow has become fully nonlinear.
Stratified spaces constitute a Fra\\"iss\\'e category
Mijares, José Gregorio
2010-01-01
We prove that stratified spaces and stratified pseudomanifolds satisfy categorical Fra\\"{\\i}ss\\'e properties. This result was presented for the First Meeting of Logic and Algebra in Bogot\\'a, on Sept. 2010. This article has been submitted to the Revista Colombiana de Matem\\'aticas.
Quasi-geostrophic modes in the Earth's fluid core with an outer stably stratified layer
Vidal, Jérémie
2015-01-01
Seismic waves sensitive to the outermost part of the Earth's liquid core seem to be affected by a stably stratified layer at the core-mantle boundary. Such a layer could have an observable signature in both long-term and short-term variations of the magnetic field of the Earth, which are used to probe the flow at the top of the core. Indeed, with the recent SWARM mission, it seems reasonable to be able to identify waves propagating in the core with period of several months, which may play an important role in the large-scale dynamics. In this paper, we characterize the influence of a stratified layer at the top of the core on deep quasi-geostrophic (Rossby) waves. We compute numerically the quasi-geostrophic eigenmodes of a rapidly rotating spherical shell, with a stably stratified layer near the outer boundary. Two simple models of stratification are taken into account, which are scaled with commonly accepted values of the Brunt-V{\\"a}is{\\"a}l{\\"a} frequency in the Earth's core. In the absence of magnetic fi...
Dobrovolskis, Anthony R.; Cuzzi, Jeffrey N. (Technical Monitor)
1995-01-01
The shape and spin of Neptune's outermost satellite Nereid are still unknown. Ground-based photometry indicates large brightness variations, but different observers report very different lightcurve amplitudes and periods. On the contrary, Voyager 2 images spanning 12 days show no evidence of variations greater than 0.1 mag. The latter suggest either that Nereid is nearly spherical, or that it is rotating slowly. We propose that tides have already despun Nereid's rotation to a period of a few weeks, during the time before the capture of Triton when Nereid was closer to Neptune. Since Nereid reached its present orbit, tides have further despun Nereid to a period on the order of a month. For Nereid's orbital eccentricity of 0.75, tidal evolution ceases when the spin period is still approximately 1/8 of the orbital period. Furthermore, the synchronous resonance becomes quite weak for such high eccentricities, along with other low-order spin orbit commensurabilities. In contrast, high-order resonances become very strong particularly the 6:1, 6.5:1, 7:1, 7.5:1, and 8:1 spin states. If Nereid departs by more than approximately 1% from a sphere, however, these resonances overlap, generating chaos. Our simulations show that Nereid is likely to be in chaotic rotation for any spin period longer than about 2 weeks.
Weak gravitational lensing with the Square Kilometre Array
Brown, M L; Camera, S; Harrison, I; Joachimi, B; Metcalf, R B; Pourtsidou, A; Takahashi, K; Zuntz, J A; Abdalla, F B; Bridle, S; Jarvis, M; Kitching, T D; Miller, L; Patel, P
2015-01-01
We investigate the capabilities of various stages of the SKA to perform world-leading weak gravitational lensing surveys. We outline a way forward to develop the tools needed for pursuing weak lensing in the radio band. We identify the key analysis challenges and the key pathfinder experiments that will allow us to address them in the run up to the SKA. We identify and summarize the unique and potentially very powerful aspects of radio weak lensing surveys, facilitated by the SKA, that can solve major challenges in the field of weak lensing. These include the use of polarization and rotational velocity information to control intrinsic alignments, and the new area of weak lensing using intensity mapping experiments. We show how the SKA lensing surveys will both complement and enhance corresponding efforts in the optical wavebands through cross-correlation techniques and by way of extending the reach of weak lensing to high redshift.
The rotational spectrum of tyrosine.
Pérez, Cristóbal; Mata, Santiago; Cabezas, Carlos; López, Juan C; Alonso, José L
2015-04-23
In this work neutral tyrosine has been generated in the gas phase by laser ablation of solid samples, and its most abundant conformers characterized through their rotational spectra. Their identification has been made by comparison between the experimental and ab initio values of the rotational and quadrupole coupling constants. Both conformers are stabilized by an O-H•••N hydrogen bond established within the amino acid skeleton chain and an additional weak N-H•••π hydrogen bond. The observed conformers differ in the orientation of the phenolic -OH group.
Gas slug ascent through rheologically stratified conduits
Capponi, Antonio; James, Mike R.; Lane, Steve J.
2016-04-01
Textural and petrological evidence has indicated the presence of viscous, degassed magma layers at the top of the conduit at Stromboli. This layer acts as a plug through which gas slugs burst and it is thought to have a role in controlling the eruptive dynamics. Here, we present the results of laboratory experiments which detail the range of slug flow configurations that can develop in a rheologically stratified conduit. A gas slug can burst (1) after being fully accommodated within the plug volume, (2) whilst its base is still in the underlying low-viscosity liquid or (3) within a low-viscosity layer dynamically emplaced above the plug during the slug ascent. We illustrate the relevance of the same flow configurations at volcanic-scale through a new experimentally-validated 1D model and 3D computational fluid dynamic simulations. Applied to Stromboli, our results show that gas volume, plug thickness, plug viscosity and conduit radius control the transition between each configuration; in contrast, the configuration distribution seems insensitive to the viscosity of magma beneath the plug, which acts mainly to deliver the slug into the plug. Each identified flow configuration encompasses a variety of processes including dynamic narrowing and widening of the conduit, generation of instabilities along the falling liquid film, transient blockages of the slug path and slug break-up. All these complexities, in turn, lead to variations in the slug overpressure, mirrored by changes in infrasonic signatures which are also associated to different eruptive styles. Acoustic amplitudes are strongly dependent on the flow configuration in which the slugs burst, with both acoustic peak amplitudes and waveform shapes reflecting different burst dynamics. When compared to infrasonic signals from Stromboli, the similarity between real signals and laboratory waveforms suggests that the burst of a slug through a plug may represent a viable first-order mechanism for the generation of
Methane metabolism in a stratified boreal lake
Nykänen, Hannu; Peura, Sari; Kankaala, Paula; Jones, Roger
2013-04-01
Stratified lakes, typical of the boreal zone, are naturally anoxic from their bottoms. In these lakes methanogenesis can account for up to half of organic matter degradation. However, a major part of the methane (CH4) is oxidized in the water column before reaching the atmosphere. Since methanotrophs use CH4 as their sole carbon and energy source, much CH4-derived carbon is incorporated into their biomass. Microbially produced CH4 has strongly negative δ13C compared to other carbon forms in ecosystems, making it possible to follow its route in food webs. However, only a few studies have estimated the amount of this microbial biomass or its carbon stable isotopic composition due to difficulties in separating it from other biomass or from other carbon forms in the water column. We estimated methanotrophic biomass from measured CH4 oxidation, and δ13C of the biomass from measured δ13C values of CH4, DIC, POM and DOC. An estimate of the fraction of methanotrophs in total microbial biomass is derived from bacterial community composition measurements. The study was made in, Alinen Mustajärvi, a small (area 0.75 ha, maximum depth 6.5 m, mean depth 4.2 m,), oligotrophic, mesohumic headwater lake located in boreal coniferous forest in southern Finland. CH4 and DIC concentrations and their δ13C were measured over the deepest point of the lake at 1 m intervals. 13C of DOM and POM were analyzed from composite samples from epi-, meta-, and hypolimnion. Evasion of CH4 and carbon dioxide from the lake surface to the atmosphere was estimated with boundary layer diffusion equations. CH4oxidation was estimated by comparing differences between observed concentrations and CH4potentially transported by turbulent diffusion between different vertical layers in the lake and also by actual methanotrophy measurements and from vertical differences in δ13C-CH4. The estimate of CH4 production was based on the sum of oxidized and released CH4. Molecular microbiology methods were used to
Weak Polarized Electron Scattering
Erler, Jens; Mantry, Sonny; Souder, Paul A
2014-01-01
Scattering polarized electrons provides an important probe of the weak interactions. Precisely measuring the parity-violating left-right cross section asymmetry is the goal of a number of experiments recently completed or in progress. The experiments are challenging, since A_{LR} is small, typically between 10^(-4) and 10^(-8). By carefully choosing appropriate targets and kinematics, various pieces of the weak Lagrangian can be isolated, providing a search for physics beyond the Standard Model. For other choices, unique features of the strong interaction are studied, including the radius of the neutron density in heavy nuclei, charge symmetry violation, and higher twist terms. This article reviews the theory behind the experiments, as well as the general techniques used in the experimental program.
Energy Technology Data Exchange (ETDEWEB)
Suzuki, M.
1988-04-01
Dynamical mechanism of composite W and Z is studied in a 1/N field theory model with four-fermion interactions in which global weak SU(2) symmetry is broken explicitly by electromagnetic interaction. Issues involved in such a model are discussed in detail. Deviation from gauge coupling due to compositeness and higher order loop corrections are examined to show that this class of models are consistent not only theoretically but also experimentally.
DEFF Research Database (Denmark)
Haagerup, Uffe; Knudby, Søren
2015-01-01
The weak Haagerup property for locally compact groups and the weak Haagerup constant were recently introduced by the second author [27]. The weak Haagerup property is weaker than both weak amenability introduced by Cowling and the first author [9] and the Haagerup property introduced by Connes [6......] and Choda [5]. In this paper, it is shown that a connected simple Lie group G has the weak Haagerup property if and only if the real rank of G is zero or one. Hence for connected simple Lie groups the weak Haagerup property coincides with weak amenability. Moreover, it turns out that for connected simple...... Lie groups the weak Haagerup constant coincides with the weak amenability constant, although this is not true for locally compact groups in general. It is also shown that the semidirect product R2 × SL(2,R) does not have the weak Haagerup property....
Weak martingale Hardy spaces and weak atomic decompositions
Institute of Scientific and Technical Information of China (English)
HOU; Youliang; REN; Yanbo
2006-01-01
In this paper we define some weak martingale Hardy spaces and three kinds of weak atoms. They are the counterparts of martingale Hardy spaces and atoms in the classical martingale Hp-theory. And then three atomic decomposition theorems for martingales in weak martingale Hardy spaces are proved. With the help of the weak atomic decompositions of martingale, a sufficient condition for a sublinear operator defined on the weak martingale Hardy spaces to be bounded is given. Using the sufficient condition, we obtain a series of martingale inequalities with respect to the weak Lp-norm, the inequalities of weak (p ,p)-type and some continuous imbedding relationships between various weak martingale Hardy spaces. These inequalities are the weak versions of the basic inequalities in the classical martingale Hp-theory.
Time-dependent rotating stratified shear flow: exact solution and stability analysis.
Salhi, A; Cambon, C
2007-01-01
A solution of the Euler equations with Boussinesq approximation is derived by considering unbounded flows subjected to spatially uniform density stratification and shear rate that are time dependent [S(t)= partial differentialU3/partial differentialx2]. In addition to vertical stratification with constant strength N(v)2, this base flow includes an additional, horizontal, density gradient characterized by N(h)2(t). The stability of this flow is then analyzed: When the vertical stratification is stabilizing, there is a simple harmonic motion of the horizontal stratification N(h)2(t) and of the shear rate S(t), but this flow is unstable to certain disturbances, which are amplified by a Floquet mechanism. This analysis may involve an additional Coriolis effect with Coriolis parameter f, so that governing dimensionless parameters are a modified Richardson number, R=[S(0)2+N(h)4(0)/N(v)2]1/2, and f(v)=f/N(v), as well as the initial phase of the periodic shear rate. Parametric resonance between the inertia-gravity waves and the oscillating shear is demonstrated from the dispersion relation in the limit R-->0. The parametric instability has connection with both baroclinic and elliptical flow instabilities, but can develop from a very different base flow.
Testing Lorentz invariance in weak decays
Energy Technology Data Exchange (ETDEWEB)
Sytema, Auke; Dijck, Elwin; Hoekstra, Steven; Jungmann, Klaus; Mueller, Stefan; Noordmans, Jacob; Onderwater, Gerco; Pijpker, Coen; Timmermans, Rob; Vos, Keri; Willmann, Lorenz; Wilschut, Hans [Van Swinderen Institute, University of Groningen (Netherlands)
2015-07-01
Lorentz invariance is the invariance of physical laws under orientations and boosts. It is a key assumption in Special Relativity and the Standard Model of Particle Physics. Several theories unifying General Relativity and Quantum Mechanics allow breaking of Lorentz invariance. At the Van Swinderen Institute in Groningen a theoretical and experimental research program was started to study Lorentz invariance violation (LIV) in weak interactions. The theoretical work allowed a systematic approach to LIV in weak decays. Limits could be set on parameters that quantify LIV. A novel beta decay experiment was designed which tests rotational invariance with respect to the orientation of nuclear spin. In particular, using the isotope {sup 20}Na, the decay rate dependence on the nuclear polarization direction was measured. Searching for sidereal variations, systematic errors can be suppressed. The result of the experiment is presented.
Inversion assuming weak scattering
DEFF Research Database (Denmark)
Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus
2013-01-01
The study of weak scattering from inhomogeneous media or interface roughness has long been of interest in sonar applications. In an acoustic backscattering model of a stationary field of volume inhomogeneities, a stochastic description of the field is more useful than a deterministic description...... due to the complex nature of the field. A method based on linear inversion is employed to infer information about the statistical properties of the scattering field from the obtained cross-spectral matrix. A synthetic example based on an active high-frequency sonar demonstrates that the proposed...
Erler, Jens
2013-01-01
This is a review of electroweak precision physics with particular emphasis on low-energy precision measurements in the neutral current sector of the electroweak theory and includes future experimental prospects and the theoretical challenges one faces to interpret these observables. Within the minimal Standard Model they serve as determinations of the weak mixing angle which are competitive with and complementary to those obtained near the Z-resonance. In the context of new physics beyond the Standard Model these measurements are crucial to discriminate between models and to reduce the allowed parameter space within a given model. We illustrate this for the minimal supersymmetric Standard Model with or without R-parity.
Measurement of weak radioactivity
Theodorsson , P
1996-01-01
This book is intended for scientists engaged in the measurement of weak alpha, beta, and gamma active samples; in health physics, environmental control, nuclear geophysics, tracer work, radiocarbon dating etc. It describes the underlying principles of radiation measurement and the detectors used. It also covers the sources of background, analyzes their effect on the detector and discusses economic ways to reduce the background. The most important types of low-level counting systems and the measurement of some of the more important radioisotopes are described here. In cases where more than one type can be used, the selection of the most suitable system is shown.
Weakly broken galileon symmetry
Energy Technology Data Exchange (ETDEWEB)
Pirtskhalava, David [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Santoni, Luca; Trincherini, Enrico [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); INFN, Sezione di Pisa, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Vernizzi, Filippo [Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS, Gif-sur-Yvette cédex, F-91191 (France)
2015-09-01
Effective theories of a scalar ϕ invariant under the internal galileon symmetryϕ→ϕ+b{sub μ}x{sup μ} have been extensively studied due to their special theoretical and phenomenological properties. In this paper, we introduce the notion of weakly broken galileon invariance, which characterizes the unique class of couplings of such theories to gravity that maximally retain their defining symmetry. The curved-space remnant of the galileon’s quantum properties allows to construct (quasi) de Sitter backgrounds largely insensitive to loop corrections. We exploit this fact to build novel cosmological models with interesting phenomenology, relevant for both inflation and late-time acceleration of the universe.
Hotta, H; Yokoyama, T
2014-01-01
We present a high-resolution, highly stratified numerical simulation of rotating thermal convection in a spherical shell. Our aim is to study in detail the processes that can maintain a near surface shear layer (NSSL) as inferred from helioseismology. Using the reduced speed of sound technique we can extend our global convection simulation to $0.99\\,R_{\\odot}$ and include near the top of our domain small-scale convection with short time scales that is only weakly influenced by rotation. We find the formation of a NSSL preferentially in high latitudes in the depth range $r=0.95-0.975R_\\odot$. The maintenance mechanisms are summarized as follows. Convection under weak influence of rotation leads to Reynolds stresses that transport angular momentum radially inward in all latitudes. This leads to the formation of a strong poleward directed meridional flow and a NSSL, which is balanced in the meridional plane by forces resulting from the $\\langle v'_r v'_\\theta\\rangle$ correlation of turbulent velocities. The orig...
Observations of the stratorotational instability in rotating concentric cylinders
Ibanez, Ruy; Rodenborn, Bruce
2016-01-01
We study the stability of density stratified flow between co-rotating vertical cylinders with rotation rates $\\Omega_o r_i/r_o$, but we find that this stability criterion is violated for $N$ sufficiently large; however, the destabilizing effect of the density stratification diminishes as the Reynolds number increases. At large Reynolds number the primary instability leads not to the SRI but to a previously unreported nonperiodic state that mixes the fluid.
Alberico, W M
2004-01-01
The focus of these Lectures is on the weak decay modes of hypernuclei, with special attention to Lambda-hypernuclei. The subject involves many fields of modern theoretical and experimental physics, from nuclear structure to the fundamental constituents of matter and their interactions. The various weak decay modes of Lambda-hypernuclei are described: the mesonic mode and the non-mesonic ones. The latter are the dominant decay channels of medium--heavy hypernuclei, where, on the contrary, the mesonic decay is disfavoured by Pauli blocking effect on the outgoing nucleon. In particular, one can distinguish between one-body and two-body induced decays. Theoretical models employed to evaluate the (partial and total) decay widths of hypernuclei are illustrated, and their results compared with existing experimental data. Open problems and recent achievements are extensively discussed, in particular the determination of the ratio Gamma_n/Gamma_p, possible tests of the Delta I=1/2 rule in non-mesonic decays and the pu...
Jolley, Sarah E; Bunnell, Aaron E; Hough, Catherine L
2016-11-01
Survivorship after critical illness is an increasingly important health-care concern as ICU use continues to increase while ICU mortality is decreasing. Survivors of critical illness experience marked disability and impairments in physical and cognitive function that persist for years after their initial ICU stay. Newfound impairment is associated with increased health-care costs and use, reductions in health-related quality of life, and prolonged unemployment. Weakness, critical illness neuropathy and/or myopathy, and muscle atrophy are common in patients who are critically ill, with up to 80% of patients admitted to the ICU developing some form of neuromuscular dysfunction. ICU-acquired weakness (ICUAW) is associated with longer durations of mechanical ventilation and hospitalization, along with greater functional impairment for survivors. Although there is increasing recognition of ICUAW as a clinical entity, significant knowledge gaps exist concerning identifying patients at high risk for its development and understanding its role in long-term outcomes after critical illness. This review addresses the epidemiologic and pathophysiologic aspects of ICUAW; highlights the diagnostic challenges associated with its diagnosis in patients who are critically ill; and proposes, to our knowledge, a novel strategy for identifying ICUAW. Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.
Wormhole shadows in rotating dust
Ohgami, Takayuki; Sakai, Nobuyuki
2016-09-01
As an extension of our previous work, which investigated the shadows of the Ellis wormhole surrounded by nonrotating dust, in this paper we study wormhole shadows in a rotating dust flow. First, we derive steady-state solutions of slowly rotating dust surrounding the wormhole by solving relativistic Euler equations. Solving null geodesic equations and radiation transfer equations, we investigate the images of the wormhole surrounded by dust for the above steady-state solutions. Because the Ellis wormhole spacetime possesses unstable circular orbits of photons, a bright ring appears in the image, just as in Schwarzschild spacetime. The bright ring looks distorted due to rotation. Aside from the bright ring, there appear weakly luminous complex patterns by the emission from the other side of the throat. These structure could be detected by high-resolution very-long-baseline-interferometry observations in the near future.
Tangling clustering instability for small particles in temperature stratified turbulence
Elperin, Tov; Liberman, Michael; Rogachevskii, Igor
2013-01-01
We study particle clustering in a temperature stratified turbulence with small finite correlation time. It is shown that the temperature stratified turbulence strongly increases the degree of compressibility of particle velocity field. This results in the strong decrease of the threshold for the excitation of the tangling clustering instability even for small particles. The tangling clustering instability in the temperature stratified turbulence is essentially different from the inertial clustering instability that occurs in non-stratified isotropic and homogeneous turbulence. While the inertial clustering instability is caused by the centrifugal effect of the turbulent eddies, the mechanism of the tangling clustering instability is related to the temperature fluctuations generated by the tangling of the mean temperature gradient by the velocity fluctuations. Temperature fluctuations produce pressure fluctuations and cause particle clustering in regions with increased pressure fluctuations. It is shown that t...
Numerical Study on Saltwater Instrusion in a Heterogeneous Stratified Aquifer
2000-01-01
In a costal aquifer, saltwater intrusion is frequently observed due to an excess exploitation. There are many researches focused on the saltwater intrusion. However, there are few researches, which take into consideration the mixing processes in a stratified heterogeneous aquifer. In the present study, a laboratory experiment and numerical simulation are made in order to understand the phenomena in a stratified heterogeneous aquifer. The result of the numerical analysis agrees well with the m...
Kaplan, L
1998-01-01
We examine the consequences of classical ergodicity for the localization properties of individual quantum eigenstates in the classical limit. We note that the well known Schnirelman result is a weaker form of quantum ergodicity than the one implied by random matrix theory. This suggests the possibility of systems with non-gaussian random eigenstates which are nonetheless ergodic in the sense of Schnirelman and lead to ergodic transport in the classical limit. These we call "weakly quantum ergodic.'' Indeed for a class of "slow ergodic" classical systems, it is found that each eigenstate becomes localized to an ever decreasing fraction of the available state space, in the semiclassical limit. Nevertheless, each eigenstate in this limit covers phase space evenly on any classical scale, and long-time transport properties betwen individual quantum states remain ergodic due to the diffractive effects which dominate quantum phase space exploration.
Do weak global stresses synchronize earthquakes?
Bendick, R.; Bilham, R.
2017-08-01
Insofar as slip in an earthquake is related to the strain accumulated near a fault since a previous earthquake, and this process repeats many times, the earthquake cycle approximates an autonomous oscillator. Its asymmetric slow accumulation of strain and rapid release is quite unlike the harmonic motion of a pendulum and need not be time predictable, but still resembles a class of repeating systems known as integrate-and-fire oscillators, whose behavior has been shown to demonstrate a remarkable ability to synchronize to either external or self-organized forcing. Given sufficient time and even very weak physical coupling, the phases of sets of such oscillators, with similar though not necessarily identical period, approach each other. Topological and time series analyses presented here demonstrate that earthquakes worldwide show evidence of such synchronization. Though numerous studies demonstrate that the composite temporal distribution of major earthquakes in the instrumental record is indistinguishable from random, the additional consideration of event renewal interval serves to identify earthquake groupings suggestive of synchronization that are absent in synthetic catalogs. We envisage the weak forces responsible for clustering originate from lithospheric strain induced by seismicity itself, by finite strains over teleseismic distances, or by other sources of lithospheric loading such as Earth's variable rotation. For example, quasi-periodic maxima in rotational deceleration are accompanied by increased global seismicity at multidecadal intervals.
Elliptical instabilities of stratified, hydromagnetic waves and the Earth's outer core
Energy Technology Data Exchange (ETDEWEB)
Kerswell, R.R.
1992-01-01
The streamlines of the basic rotating flow within the Earth's outer core are thought to be slightly elliptical due to tidal and precessional effects. Such a 2-dimensional elliptical flow is inertially unstable to 3-dimensional disturbances. This thesis assesses the relevance of this elliptical instability for the Earth's outer core and discusses possible implications for the geodynamo. Elliptical instability arises through a triad-type resonance of two linear waves with the underlying distorted state. When the fluid is stratified and carries a magnetic field, three different sets of waves, categorized by their dominant restoring mechanism, can exist and may potentially excite each other through the elliptical distortion. Simple cylindrical models are constructed to examine these various couplings using Earth-like parameters. It is estimated that resonances between fast (frequency comparable to the basic rotation) hydromagnetic waves can produce growth with an e-folding time of 100,000 years in the outer core, comparing favorably with typical geomagnetic inter-reversal times of O(10[sup 5]/10[sup 6]) years. Extension is made to the more geophysically-relevant, elliptically-distorted spheroidal container, in which an upper bound of 9/16 [beta] is deduced for the exponential growth rate ([beta] is the ratio of strain to rotation rate for the elliptical flow). The breakdown of a slightly distorted, rotating spheroid through an elliptical instability in commonplace. The effect of an orbiting moon is discussed and connection made between the well known middle-moment-of-inertia instability of rotating, rigid bodies and the elliptical instability. To assess the effect of ohmic and viscous dissipations upon these instabilities, a boundary layer analysis is undertaken to calculate hydromagnetic decay rates for the relevant fast waves in the outer core. The elliptical excitation of these fast hydromagnetic waves is just insufficient to overcome dissipative processes.
An experimental study on the formation and survival of stratified subsurface eddies
Bormans, Myriam
1992-12-01
We report the results of laboratory experiments on the formation and survival of internally stratified subsurface eddies in a rotating fluid. The eddies were created by injecting a dense turbulent plume at the surface of a linearly stratified environment. The relative vorticity of the lenses was always negative but larger than that of homogeneous lenses created by laminar injection. During the first 100 revolutions, the eddies shed fluid in two symmetric arms. The shedding which is believed to result from shear instabilities always resulted in a stationary axisymmetric eddy. After the eddy had spun down, the remnant fluid persisted for thousands of rotations as a circular feature with internal stratification identical to that of the environment. We created eddies with and without double diffusive convective instabilities and compared the volume of dyed fluid and the evolution of their aspect ratios. Sugar and salt were used as laboratory analogues of salt and heat, respectively. The Burger number of the lenses decreased rapidly within the first 200 revolutions and then much more slowly to reach a value between 0.2 and 0.4, These latter values are larger than those predicted by Gill (1981) for a homogeneous lens due to the internal stratification of the lenses. Radial spreading of the lens due to double diffusive intrusions was found to be larger, but of the same order of magnitude, as that induced by the vertical exchange of momentum in the absence of double diffusive convection. We formed eddies internally stratified in the diffusive sense (stable sugar gradient and unstable salt gradient) or doubly stable (stable sugar and salt gradients) by changing the ratio of the volume flux at the source to the volume flux at the spreading level as described by Bormans and Turner (1990). When the stratification in the eddies was doubly stable, three distinctive regions were observed: a region of convective layers and diffusive density interfaces at the top, a central region
Anomalously Weak Solar Convection
Hanasoge, Shravan M.; Duvall, Thomas L.; Sreenivasan, Katepalli R.
2012-01-01
Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical- harmonic degree l..Within the wavenumber band l convective velocities are 20-100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers l convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.
Spread of Matter over a Neutron-Star Surface During Disk Accretion: Deceleration of Rapid Rotation
Sunyaev, R A
2011-01-01
The problem of disk accretion onto the surface of a neutron star with a weak magnetic field at a luminosity exceeding several percent of Eddington is reduced to the problem of the braking of a hypersonic flow with a velocity that is 0.4-0.5 of the speed of light above the base of the spreading layer -- a dense atmosphere made up of previously fallen matter. We show that turbulent braking in the Prandtl-Karman model with universally accepted coefficients for terrestrial conditions and laboratory experiments and a ladder of interacting gravity waves in a stratified quasi-exponential atmosphere at standard Richardson numbers lead to a spin-up of the massive zone that extends to the ocean made up of a plasma with degenerate electrons. Turbulent braking in the ocean at the boundary with the outer solid crust reduces the rotation velocity to the solid-body rotation velocity of the star. This situation should lead to strong heating of deep atmospheric layers and to the switch-off of the explosive helium burning mech...
Transitions in turbulent rotating convection
Rajaei, Hadi; Alards, Kim; Kunnen, Rudie; Toschi, Federico; Clercx, Herman; Fluid Dynamics Lab Team
2015-11-01
This study aims to explore the flow transition from one state to the other in rotating Rayleigh-Bènard convection using Lagrangian acceleration statistics. 3D particle tracking velocimetry (3D-PTV) is employed in a water-filled cylindrical tank of equal height and diameter. The measurements are performed at the center and close to the top plate at a Rayleigh number Ra = 1.28e9 and Prandtl number Pr = 6.7 for different rotation rates. In parallel, direct numerical simulation (DNS) has been performed to provide detailed information on the boundary layers. We report the acceleration pdfs for different rotation rates and show how the transition from weakly to strongly rotating Rayleigh-Bènard affects the acceleration pdfs in the bulk and boundary layers. We observe that the shapes of the acceleration PDFs as well as the isotropy in the cell center are largely unaffected while crossing the transition point. However, acceleration pdfs at the top show a clear change at the transition point. Using acceleration pdfs and DNS data, we show that the transition between turbulent states is actually a boundary layer transition between Prandtl-Blasius type (typical of non-rotating convection) and Ekman type.
Earth rotation prevents exact solid body rotation of fluids in the laboratory
Boisson, J; Moisy, F; Cortet, P -P
2012-01-01
We report direct evidence of a secondary flow excited by the Earth rotation in a water-filled spherical container spinning at constant rotation rate. This so-called {\\it tilt-over flow} essentially consists in a rotation around an axis which is slightly tilted with respect to the rotation axis of the sphere. In the astrophysical context, it corresponds to the flow in the liquid cores of planets forced by precession of the planet rotation axis, and it has been proposed to contribute to the generation of planetary magnetic fields. We detect this weak secondary flow using a particle image velocimetry system mounted in the rotating frame. This secondary flow consists in a weak rotation, thousand times smaller than the sphere rotation, around a horizontal axis which is stationary in the laboratory frame. Its amplitude and orientation are in quantitative agreement with the theory of the tilt-over flow excited by precession. These results show that setting a fluid in a perfect solid body rotation in a laboratory exp...
Dosen, K
2010-01-01
An operad (this paper deals with non-symmetric operads) may be conceived as a partial algebra with a family of insertion operations, Gerstenhaber's circle-i products, which satisfy two kinds of associativity, one of them involving commutativity. A Cat-operad is an operad enriched over the category Cat of small categories, as a 2-category with small hom-categories is a category enriched over Cat. The notion of weak Cat-operad is to the notion of Cat-operad what the notion of bicategory is to the notion of 2-category. The equations of operads like associativity of insertions are replaced by isomorphisms in a category. The goal of this paper is to formulate conditions concerning these isomorphisms that ensure coherence, in the sense that all diagrams of canonical arrows commute. This is the sense in which the notions of monoidal category and bicategory are coherent. The coherence proof in the paper is much simplified by indexing the insertion operations in a context-independent way, and not in the usual manner. ...
Energy Transfer in Rotating Turbulence
Cambon, Claude; Mansour, Nagi N.; Godeferd, Fabien S.; Rai, Man Mohan (Technical Monitor)
1995-01-01
The influence or rotation on the spectral energy transfer of homogeneous turbulence is investigated in this paper. Given the fact that linear dynamics, e.g. the inertial waves regime tackled in an RDT (Rapid Distortion Theory) fashion, cannot Affect st homogeneous isotropic turbulent flow, the study of nonlinear dynamics is of prime importance in the case of rotating flows. Previous theoretical (including both weakly nonlinear and EDQNM theories), experimental and DNS (Direct Numerical Simulation) results are gathered here and compared in order to give a self-consistent picture of the nonlinear effects of rotation on tile turbulence. The inhibition of the energy cascade, which is linked to a reduction of the dissipation rate, is shown to be related to a damping due to rotation of the energy transfer. A model for this effect is quantified by a model equation for the derivative-skewness factor, which only involves a micro-Rossby number Ro(sup omega) = omega'/(2(OMEGA))-ratio of rms vorticity and background vorticity as the relevant rotation parameter, in accordance with DNS and EDQNM results fit addition, anisotropy is shown also to develop through nonlinear interactions modified by rotation, in an intermediate range of Rossby numbers (Ro(omega) = (omega)' and Ro(omega)w greater than 1), which is characterized by a marco-Rossby number Ro(sup L) less than 1 and Ro(omega) greater than 1 which is characterized by a macro-Rossby number based on an integral lengthscale L and the micro-Rossby number previously defined. This anisotropy is mainly an angular drain of spectral energy which tends to concentrate energy in tile wave-plane normal to the rotation axis, which is exactly both the slow and the two-dimensional manifold. In Addition, a polarization of the energy distribution in this slow 2D manifold enhances horizontal (normal to the rotation axis) velocity components, and underlies the anisotropic structure of the integral lengthscales. Finally is demonstrated the
Controlling Spiral Dynamics in Excitable Media by a Weakly Localized Pacing
Institute of Scientific and Technical Information of China (English)
LI Bing-Wei; SUN Li-Li; CHEN Bin; YING He-Ping
2007-01-01
@@ Spiral dynamics controlled by a weakly localized pacing around the spiral tip is investigated. Numerical simulations show two distinct characteristics when the pacing is applied with the weak amplitude for suitable frequencies:for a rigidly rotating spiral, a transition from rigid rotation to meandering motion is observed, and for unstable spiral waves, spiral breakup can be prevented. Successfully preventing spiral breakup is relevant to the modulation of the tip trajectory induced by a localized pacing.
Stability of stratified two-phase flows in horizontal channels
Barmak, Ilya; Ullmann, Amos; Brauner, Neima; Vitoshkin, Helen
2016-01-01
Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems the stratified flow with smooth interface is stable only in confined zone of relatively lo...
Background Oriented Schlieren in a Density Stratified Fluid
Verso, Lilly
2015-01-01
Non-intrusive quantitative fluid density measurements methods are essential in stratified flow experiments. Digital imaging leads to synthetic Schlieren methods in which the variations of the index of refraction are reconstructed computationally. In this study, an important extension to one of these methods, called Background Oriented Schlieren (BOS), is proposed. The extension enables an accurate reconstruction of the density field in stratified liquid experiments. Typically, the experiments are performed by the light source, background pattern, and the camera positioned on the opposite sides of a transparent vessel. The multi-media imaging through air-glass-water-glass-air leads to an additional aberration that destroys the reconstruction. A two-step calibration and image remapping transform are the key components that correct the images through the stratified media and provide non-intrusive full-field density measurements of transparent liquids.
Background oriented schlieren in a density stratified fluid
Verso, Lilly; Liberzon, Alex
2015-10-01
Non-intrusive quantitative fluid density measurement methods are essential in the stratified flow experiments. Digital imaging leads to synthetic schlieren methods in which the variations of the index of refraction are reconstructed computationally. In this study, an extension to one of these methods, called background oriented schlieren, is proposed. The extension enables an accurate reconstruction of the density field in stratified liquid experiments. Typically, the experiments are performed by the light source, background pattern, and the camera positioned on the opposite sides of a transparent vessel. The multimedia imaging through air-glass-water-glass-air leads to an additional aberration that destroys the reconstruction. A two-step calibration and image remapping transform are the key components that correct the images through the stratified media and provide a non-intrusive full-field density measurements of transparent liquids.
SINDA/FLUINT Stratified Tank Modeling for Cryrogenic Propellant Tanks
Sakowski, Barbara
2014-01-01
A general purpose SINDA/FLUINT (S/F) stratified tank model was created to simulate self-pressurization and axial jet TVS; Stratified layers in the vapor and liquid are modeled using S/F lumps.; The stratified tank model was constructed to permit incorporating the following additional features:, Multiple or singular lumps in the liquid and vapor regions of the tank, Real gases (also mixtures) and compressible liquids, Venting, pressurizing, and draining, Condensation and evaporation/boiling, Wall heat transfer, Elliptical, cylindrical, and spherical tank geometries; Extensive user logic is used to allow detailed tailoring - Don't have to rebuilt everything from scratch!!; Most code input for a specific case is done through the Registers Data Block:, Lump volumes are determined through user input:; Geometric tank dimensions (height, width, etc); Liquid level could be input as either a volume percentage of fill level or actual liquid level height
Fuel Burning Rate Model for Stratified Charge Engine
Institute of Scientific and Technical Information of China (English)
SONG Jin'ou; JIANG Zejun; YAO Chunde; WANG Hongfu
2006-01-01
A zero-dimensional single-zone double-curve model is presented to predict fuel burning rate in stratified charge engines, and it is integrated with GT-Power to predict the overall performance of the stratified charge engines.The model consists of two exponential functions for calculating the fuel burning rate in different charge zones.The model factors are determined by a non-linear curve fitting technique, based on the experimental data obtained from 30 cases in middle and low loads.The results show good agreement between the measured and calculated cylinder pressures,and the deviation between calculated and measured cylinder pressures is less than 5%.The zerodimensional single-zone double-curve model is successful in the combustion modeling for stratified charge engines.
Numerical Simulation on Stratified Flow over an Isolated Mountain Ridge
Institute of Scientific and Technical Information of China (English)
LI Ling; Shigeo Kimura
2007-01-01
The characteristics of stratified flow over an isolated mountain ridge have been investigated numerically. The two-dimensional model equations, based on the time-dependent Reynolds averaged NavierStokes equations, are solved numerically using an implicit time integration in a fitted body grid arrangement to simulate stratified flow over an isolated ideally bell-shaped mountain. The simulation results are in good agreement with the existing corresponding analytical and approximate solutions. It is shown that for atmospheric conditions where non-hydrostatic effects become dominant, the model is able to reproduce typical flow features. The dispersion characteristics of gaseous pollutants in the stratified flow have also been studied. The dispersion patterns for two typical atmospheric conditions are compared. The results show that the presence of a gravity wave causes vertical stratification of the pollutant concentration and affects the diffusive characteristics of the pollutants.
Stability of stratified two-phase flows in inclined channels
Barmak, Ilya; Ullmann, Amos; Brauner, Neima
2016-01-01
Linear stability of stratified gas-liquid and liquid-liquid plane-parallel flows in inclined channels is studied with respect to all wavenumber perturbations. The main objective is to predict parameter regions in which stable stratified configuration in inclined channels exists. Up to three distinct base states with different holdups exist in inclined flows, so that the stability analysis has to be carried out for each branch separately. Special attention is paid to the multiple solution regions to reveal the feasibility of non-unique stable stratified configurations in inclined channels. The stability boundaries of each branch of steady state solutions are presented on the flow pattern map and are accompanied by critical wavenumbers and spatial profiles of the most unstable perturbations. Instabilities of different nature are visualized by streamlines of the neutrally stable perturbed flows, consisting of the critical perturbation superimposed on the base flow. The present analysis confirms the existence of ...
Weak Total Resolvability In Graphs
Directory of Open Access Journals (Sweden)
Casel Katrin
2016-02-01
Full Text Available A vertex v ∈ V (G is said to distinguish two vertices x, y ∈ V (G of a graph G if the distance from v to x is di erent from the distance from v to y. A set W ⊆ V (G is a total resolving set for a graph G if for every pair of vertices x, y ∈ V (G, there exists some vertex w ∈ W − {x, y} which distinguishes x and y, while W is a weak total resolving set if for every x ∈ V (G−W and y ∈ W, there exists some w ∈ W −{y} which distinguishes x and y. A weak total resolving set of minimum cardinality is called a weak total metric basis of G and its cardinality the weak total metric dimension of G. Our main contributions are the following ones: (a Graphs with small and large weak total metric bases are characterised. (b We explore the (tight relation to independent 2-domination. (c We introduce a new graph parameter, called weak total adjacency dimension and present results that are analogous to those presented for weak total dimension. (d For trees, we derive a characterisation of the weak total (adjacency metric dimension. Also, exact figures for our parameters are presented for (generalised fans and wheels. (e We show that for Cartesian product graphs, the weak total (adjacency metric dimension is usually pretty small. (f The weak total (adjacency dimension is studied for lexicographic products of graphs.
Nonlinear waves in stratified Taylor--Couette flow. Part 1. Layer formation
Leclercq, Colin; Augier, Pierre; Caulfield, Colm-Cille P; Dalziel, Stuart B; Linden, Paul F
2016-01-01
This paper is the first part of a two-fold study of mixing, i.e. the formation of layers and upwelling of buoyancy, in axially stratified Taylor--Couette flow, with fixed outer cylinder. Using linear analysis and direct numerical simulation, we show the critical role played by non-axisymmetric instability modes, despite the fact that the flow is centrifugally unstable in the sense of Rayleigh's criterion. Interactions between helical modes of opposite handedness leads to the formation of nonlinear coherent structures: (mixed)-ribbons and (mixed)-cross-spirals. These give birth to complex density interface patterns, seemingly appearing and disappearing periodically as the coherent structure slowly rotates around the annulus. These coherent structures seem to be responsible for the formation of layers reported in a recent experiment by Oglethorpe et al. (2013). We distinguish `dynamic layering', instantaneous, localized and caused by the vortical motions, from `static layering' corresponding to the formation of...
Testing of RANS Turbulence Models for Stratified Flows Based on DNS Data
Venayagamoorthy, S. K.; Koseff, J. R.; Ferziger, J. H.; Shih, L. H.
2003-01-01
In most geophysical flows, turbulence occurs at the smallest scales and one of the two most important additional physical phenomena to account for is strati cation (the other being rotation). In this paper, the main objective is to investigate proposed changes to RANS turbulence models which include the effects of stratifi- cation more explicitly. These proposed changes were developed using a DNS database on strati ed and sheared homogenous turbulence developed by Shih et al. (2000) and are described more fully in Ferziger et al. (2003). The data generated by Shih, et al. (2000) (hereinafter referred to as SKFR) are used to study the parameters in the k- model as a function of the turbulent Froude number, Frk. A modified version of the standard k- model based on the local turbulent Froude number is proposed. The proposed model is applied to a stratified open channel flow, a test case that differs significantly from the flows from which the modified parameters were derived. The turbulence modeling and results are discussed in the next two sections followed by suggestions for future work.
Linear Inviscid Damping for Couette Flow in Stratified Fluid
Yang, Jincheng
2016-01-01
We study the inviscid damping of Coutte flow with an exponentially stratified density. The optimal decay rates of the velocity field and density are obtained for general perturbations with minimal regularity. For Boussinesq approximation model, the decay rates we get are consistent with the previous results in the literature. We also study the decay rates for the full equations of stratified fluids, which were not studied before. For both models, the decay rates depend on the Richardson number in a very similar way. Besides, we also study the inviscid damping of perturbations due to the exponential stratification when there is no shear.
Bases of Schur algebras associated to cellularly stratified diagram algebras
Bowman, C
2011-01-01
We examine homomorphisms between induced modules for a certain class of cellularly stratified diagram algebras, including the BMW algebra, Temperley-Lieb algebra, Brauer algebra, and (quantum) walled Brauer algebra. We define the `permutation' modules for these algebras, these are one-sided ideals which allow us to study the diagrammatic Schur algebras of Hartmann, Henke, Koenig and Paget. We construct bases of these Schur algebras in terms of modified tableaux. On the way we prove that the (quantum) walled Brauer algebra and the Temperley-Lieb algebra are both cellularly stratified and therefore have well-defined Specht filtrations.
... this page: //medlineplus.gov/ency/patientinstructions/000357.htm Rotator cuff exercises To use the sharing features on this ... gov/pubmed/25560729 . Read More Frozen shoulder Rotator cuff problems Rotator cuff repair Shoulder arthroscopy Shoulder CT scan Shoulder ...
Sainath, Kamalesh; Teixeira, Fernando L; Donderici, Burkay
2014-01-01
We develop a general-purpose formulation, based on two-dimensional spectral integrals, for computing electromagnetic fields produced by arbitrarily oriented dipoles in planar-stratified environments, where each layer may exhibit arbitrary and independent anisotropy in both its (complex) permittivity and permeability tensors. Among the salient features of our formulation are (i) computation of eigenmodes (characteristic plane waves) supported in arbitrarily anisotropic media in a numerically robust fashion, (ii) implementation of an hp-adaptive refinement for the numerical integration to evaluate the radiation and weakly evanescent spectra contributions, and (iii) development of an adaptive extension of an integral convergence acceleration technique to compute the strongly evanescent spectrum contribution. While other semianalytic techniques exist to solve this problem, none have full applicability to media exhibiting arbitrary double anisotropies in each layer, where one must account for the whole range of possible phenomena (e.g., mode coupling at interfaces and nonreciprocal mode propagation). Brute-force numerical methods can tackle this problem but only at a much higher computational cost. The present formulation provides an efficient and robust technique for field computation in arbitrary planar-stratified environments. We demonstrate the formulation for a number of problems related to geophysical exploration.
Phenomenology of two-dimensional stably stratified turbulence under large-scale forcing
Kumar, Abhishek; Sukhatmae, Jai
2016-01-01
In this paper we characterize the scaling of energy spectra, and the interscale transfer of energy and enstrophy, for strongly, moderately and weakly stably stratified two-dimensional (2D) turbulence under large-scale random forcing. In the strongly stratified case, a large-scale vertically sheared horizontal flow (VSHF) co-exists with small scale turbulence. The VSHF consists of internal gravity waves and the turbulent flow has a kinetic energy (KE) spectrum that follows an approximate $k^{-3}$ scaling with zero KE flux and a robust positive enstrophy flux. The spectrum of the turbulent potential energy (PE) also approximately follows a $k^{-3}$ power-law and its flux is directed to small scales. For moderate stratification, there is no VSHF and the KE of the turbulent flow exhibits Bolgiano-Obukhov scaling that transitions from a shallow $k^{-11/5}$ form at large scales, to a steeper approximate $k^{-3}$ scaling at small scales. The entire range of scales shows a strong forward enstrophy flux, and interesti...
Seismic diagnosis from gravity modes strongly affected by rotation
Prat, Vincent; Lignières, François; Ballot, Jérôme; Culpin, Pierre-Marie
2016-01-01
Most of the information we have about the internal rotation of stars comes from modes that are weakly affected by rotation, for example by using rotational splittings. In contrast, we present here a method, based on the asymptotic theory of Prat et al. (2016), which allows us to analyse the signature of rotation where its effect is the most important, that is in low-frequency gravity modes that are strongly affected by rotation. For such modes, we predict two spectral patterns that could be confronted to observed spectra and those computed using fully two-dimensional oscillation codes.
Weak compactness of biharmonic maps
Directory of Open Access Journals (Sweden)
Shenzhou Zheng
2012-10-01
Full Text Available This article shows that if a sequence of weak solutions of a perturbed biharmonic map satisfies $Phi_ko 0$ in $(W^{2,2}^*$ and $u_kightharpoonup u$ weakly in $W^{2,2}$, then $u$ is a biharmonic map. In particular, we show that the space of biharmonic maps is sequentially compact under the weak-$W^{2,2}$ topology.
Redshift and the Rotating Gravitational Field
Christensen, Walter James
2010-01-01
Previously it was shown that if a weak gravitational field is modeled as a background of oscillating gravitons described by normal coordinates, then the field naturally exhibits rotational kinetic energy. The conformal metric associated with this oscillatory motion is given by g{\\mu}{\
Large-scale confinement and small-scale clustering of floating particles in stratified turbulence
Sozza, A; Musacchio, S; Boffetta, G
2015-01-01
We study the motion of small inertial particles in stratified turbulence. We derive a simplified model, valid within the Boussinesq approximation, for the dynamics of small particles in presence of a mean linear density profile. By means of extensive direct numerical simulations, we investigate the statistical distribution of particles as a function of the two dimensionless parameters of the problem. We find that vertical confinement of particles is mainly ruled by the degree of stratification, with a weak dependency on the particle properties. Conversely, small scale fractal clustering, typical of inertial particles in turbulence, depends on the particle relaxation time and is almost independent on the flow stratification. The implications of our findings for the formation of thin phytoplankton layers are discussed.
Sainath, K; Donderici, B
2013-01-01
We develop a general-purpose formulation, based on two-dimensional spectral integrals, for computing electromagnetic fields produced by arbitrarily-oriented dipoles in planar-stratified environments, where each layer may exhibit arbitrary and independent anisotropy in both the (complex) permittivity and permeability. Among the salient features of our formulation are (1) computation of eigenmodes (characteristic plane waves) supported in arbitrarily anisotropic media in a numerically robust fashion, (2) implementation of an hp-adaptive refinement for the numerical integration to evaluate the radiation and weakly-evanescent spectra contributions, and (3) development of an adaptive extension of an integral convergence acceleration technique to compute the strongly-evanescent spectrum contribution. While other semianalytic techniques exist to solve this problem, none have full applicability to media exhibiting arbitrary double anisotropies in each layer, where one must account for the whole range of possible phen...
Space group constraints on weak indices in topological insulators
Varjas, Dániel; de Juan, Fernando; Lu, Yuan-Ming
2017-07-01
Lattice translation symmetry gives rise to a large class of "weak" topological insulators (TIs), characterized by translation-protected gapless surface states and dislocation bound states. In this work we show that space group symmetries lead to constraints on the weak topological indices that define these phases. In particular, we show that screw rotation symmetry enforces the Hall conductivity in planes perpendicular to the screw axis to be quantized in multiples of the screw rank, which generally applies to interacting systems. We further show that certain 3D weak indices associated with quantum spin Hall effects (class AII) are forbidden by the Bravais lattice and by glide or even-fold screw symmetries. These results put strong constraints on weak TI candidates in the experimental and numerical search for topological materials, based on the crystal structure alone.
The Stability of Weakly Collisional Plasmas with Thermal and Composition Gradients
Pessah, Martin E; 10.1088/0004-637X/764/1/13
2013-01-01
Over the last decade, substantial efforts have been devoted to understanding the stability properties, transport phenomena, and long-term evolution of weakly-collisional, magnetized plasmas which are stratified in temperature. These studies have improved our understanding of the physics governing the intra-cluster medium (ICM), but assumed that ICM is a homogeneous. This, however, might not be a good approximation if heavy elements sediment in the inner region of the galaxy cluster. In this paper, we analyze the stability of a weakly-collisional, magnetized plane-parallel atmosphere which is stratified in both temperature and composition. This allows us to discuss for the first time the dynamics of weakly-collisional environments where heat conduction, momentum transport, and ion-diffusion are anisotropic with respect to the direction of the magnetic field. We show that, depending on the relative signs and magnitudes of the gradients in the temperature and the mean molecular weight, the plasma can be subject ...
Rotating Cavitation Supression Project
National Aeronautics and Space Administration — FTT proposes development of a rotating cavitation (RC) suppressor for liquid rocket engine turbopump inducers. Cavitation instabilities, such as rotating...
Phenomenology of two-dimensional stably stratified turbulence under large-scale forcing
Kumar, Abhishek
2017-01-11
In this paper, we characterise the scaling of energy spectra, and the interscale transfer of energy and enstrophy, for strongly, moderately and weakly stably stratified two-dimensional (2D) turbulence, restricted in a vertical plane, under large-scale random forcing. In the strongly stratified case, a large-scale vertically sheared horizontal flow (VSHF) coexists with small scale turbulence. The VSHF consists of internal gravity waves and the turbulent flow has a kinetic energy (KE) spectrum that follows an approximate k−3 scaling with zero KE flux and a robust positive enstrophy flux. The spectrum of the turbulent potential energy (PE) also approximately follows a k−3 power-law and its flux is directed to small scales. For moderate stratification, there is no VSHF and the KE of the turbulent flow exhibits Bolgiano–Obukhov scaling that transitions from a shallow k−11/5 form at large scales, to a steeper approximate k−3 scaling at small scales. The entire range of scales shows a strong forward enstrophy flux, and interestingly, large (small) scales show an inverse (forward) KE flux. The PE flux in this regime is directed to small scales, and the PE spectrum is characterised by an approximate k−1.64 scaling. Finally, for weak stratification, KE is transferred upscale and its spectrum closely follows a k−2.5 scaling, while PE exhibits a forward transfer and its spectrum shows an approximate k−1.6 power-law. For all stratification strengths, the total energy always flows from large to small scales and almost all the spectral indicies are well explained by accounting for the scale-dependent nature of the corresponding flux.
Analysis of photonic band-gap structures in stratified medium
DEFF Research Database (Denmark)
Tong, Ming-Sze; Yinchao, Chen; Lu, Yilong;
2005-01-01
Purpose - To demonstrate the flexibility and advantages of a non-uniform pseudo-spectral time domain (nu-PSTD) method through studies of the wave propagation characteristics on photonic band-gap (PBG) structures in stratified medium Design/methodology/approach - A nu-PSTD method is proposed...
Plane Stratified Flow in a Room Ventilated by Displacement Ventilation
DEFF Research Database (Denmark)
Nielsen, Peter Vilhelm; Nickel, J.; Baron, D. J. G.
2004-01-01
The air movement in the occupied zone of a room ventilated by displacement ventilation exists as a stratified flow along the floor. This flow can be radial or plane according to the number of wall-mounted diffusers and the room geometry. The paper addresses the situations where plane flow...
Bacterial production, protozoan grazing and mineralization in stratified lake Vechten.
Bloem, J.
1989-01-01
The role of heterotrophic nanoflagellates (HNAN, size 2-20 μm) in grazing on bacteria and mineralization of organic matter in stratified Lake Vechten was studied.Quantitative effects of manipulation and fixation on HNAN were checked. Considerable losses were caused by centrifugation, even at low spe
Population dynamics of sinking phytoplankton in stratified waters
Huisman, J.; Sommeijer, B.P.
2002-01-01
We analyze the predictions of a reaction-advection-diffusion model to pinpoint the necessary conditions for bloom development of sinking phytoplanktonspecies in stratified waters. This reveals that there are two parameter windows that can sustain sinking phytoplankton, a turbulence window and atherm
Gravity-induced stresses in stratified rock masses
Amadei, B.; Swolfs, H.S.; Savage, W.Z.
1988-01-01
This paper presents closed-form solutions for the stress field induced by gravity in anisotropic and stratified rock masses. These rocks are assumed to be laterally restrained. The rock mass consists of finite mechanical units, each unit being modeled as a homogeneous, transversely isotropic or isotropic linearly elastic material. The following results are found. The nature of the gravity induced stress field in a stratified rock mass depends on the elastic properties of each rock unit and how these properties vary with depth. It is thermodynamically admissible for the induced horizontal stress component in a given stratified rock mass to exceed the vertical stress component in certain units and to be smaller in other units; this is not possible for the classical unstratified isotropic solution. Examples are presented to explore the nature of the gravity induced stress field in stratified rock masses. It is found that a decrease in rock mass anisotropy and a stiffening of rock masses with depth can generate stress distributions comparable to empirical hyperbolic distributions previously proposed in the literature. ?? 1988 Springer-Verlag.
Dispersion of (light) inertial particles in stratified turbulence
van Aartrijk, M.; Clercx, H.J.H.; Armenio, Vincenzo; Geurts, Bernardus J.; Fröhlich, Jochen
2010-01-01
We present a brief overview of a numerical study of the dispersion of particles in stably stratified turbulence. Three types of particles arc examined: fluid particles, light inertial particles ($\\rho_p/\\rho_f = \\mathcal{O}(1)$) and heavy inertial particles ($\\rho_p/\\rho_f \\gg 1$). Stratification
Characterization of Inlet Diffuser Performance for Stratified Thermal Storage
Cimbala, John M.; Bahnfleth, William; Song, Jing
1999-11-01
Storage of sensible heating or cooling capacity in stratified vessels has important applications in central heating and cooling plants, power production, and solar energy utilization, among others. In stratified thermal storage systems, diffusers at the top and bottom of a stratified tank introduce and withdraw fluid while maintaining a stable density gradient and causing as little mixing as possible. In chilled water storage applications, mixing during the formation of the thermocline near an inlet diffuser is the single greatest source of thermal losses. Most stratified chilled water storage tanks are cylindrical vessels with diffusers that are either circular disks that distribute flow radially outward or octagonal rings of perforated pipe that distribute flow both inward and outward radially. Both types produce gravity currents that are strongly influenced by the inlet Richardson number, but the significance of other parameters is not clear. The present investigation considers the dependence of the thermal performance of a perforated pipe diffuser on design parameters including inlet velocity, ambient and inlet fluid temperatures, and tank dimensions for a range of conditions representative of typical chilled water applications. Dimensional analysis is combined with a parametric study using results from computational fluid dynamics to obtain quantitative relationships between design parameters and expected thermal performance.
Global and Partial Errors in Stratified and Clustering Sampling
Giovanna Nicolini; Anna Lo Presti
2005-01-01
In this paper we split up the sampling error occurred in stratified and clustering sampling, called global error and measured by the variance of estimator, in many partial errors each one referred to a single stratum or cluster. In particular, we study, for clustering sampling, the empirical distribution of the homogeneity coefficient that is very important for settlement of partial errors.
Neutrino oscillations in the field of a rotating deformed mass
Geralico, Andrea
2012-01-01
The neutrino oscillations in the field of a rotating deformed mass is investigated. The phase shift is evaluated in the case of weak field limit, slow rotation and small deformation. To this aim the Hartle-Thorne metric is used, which is an approximate solution of the vacuum Einstein equations accurate to second order in the rotation parameter $a/M$ and to first order in the mass quadrupole moment $q$. Implications on atmospheric, solar and astrophysical neutrinos are discussed.
[Systemic lupus erythematosus and weakness].
Vinagre, Filipe; Santos, Maria José; da Silva, José Canas
2006-01-01
We report a case of a 13-year old young girl, with Juvenile Systemic Lupus Erythematosus and recent onset of muscle weakness. Investigations lead to the diagnosis of Myasthenia Gravis. The most important causes of muscle weakness in lupus patients are discussed.
Chiral perturbation theory approach to hadronic weak amplitudes
Energy Technology Data Exchange (ETDEWEB)
Rafael, E. de (Centre National de la Recherche Scientifique, 13 - Marseille (France). Centre de Physique Theorique 2)
1989-07-01
We are concerned with applications to the non-leptonic weak interactions in the sector of light quark flavors: u, d and s. Both strangeness changing {Delta}S=1 and {Delta}S=2 non-leptonic transitions can be described as weak perturbations to the strong effective chiral Lagrangian; the chiral structure of the weak effective Lagrangian being dictated by the transformation properties of the weak non-leptonic Hamiltonian of the Standard Model under global SU(3){sub Left}xSU(3){sub Right} rotations of the quark-fields. These lectures are organized as follows. Section 2 gives a review of the basic properties of chiral symmetry. Section 3 explains the effective chiral realization of the non-leptonic weak Hamiltonian of the Standard Model to lowest order in derivatives and masses. Section 4 deals with non-leptonic weak transitions in the presence of electromagnetism. Some recent applications to radiative kaon decays are reviewed and the effect of the so called electromagnetic penguin like diagrams is also discussed. Section 5 explains the basic ideas of the QCD-hadronic duality approach to the evaluation of coupling constants of the non-leptonic chiral weak Lagrangian. (orig./HSI).
Zhong, Jin-Qiang; Wang, Xue-ying
2016-01-01
We present measurements of the azimuthal orientation {\\theta}(t) and thermal amplitude {\\delta}(t) of the large-scale circulation (LSC) of turbulent rotating convection within an unprecedented large Rossby number range 170. We identify the mechanism through which the mean retrograde rotation speed can be enhanced by stochastic cessations in the presence of weak Coriolis force, and show that a low-dimensional, stochastic model provides predictions of the observed large-scale flow dynamics and interprets its retrograde rotation.
When a negative weak value -1 plays the counterpart of a probability 1
Yokota, Kazuhiro; Imoto, Nobuyuki
2016-12-01
When the weak value of a projector is 1, a quantum system behaves as in that eigenstate with probability 1. By definition, however, the weak value may take an anomalous value lying outside the range of probability like -1. From the viewpoint of a physical effect, we show that such a negative weak value of -1 can be regarded as the counterpart of the ordinary value of 1. Using photons, we experimentally verify it as the symmetrical shift in polarization depending on the weak value given by pre-postselection of the path state. Unlike observation of a weak value as an ensemble average via weak measurements, the effect of a weak value is definitely confirmed in Hong-Ou-Mandel effect: the symmetrical shift corresponding to the weak value can be directly observed as the rotation angle of a half wave plate.
Energy Technology Data Exchange (ETDEWEB)
Hotta, H.; Rempel, M. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO (United States); Yokoyama, T., E-mail: hotta@ucar.edu [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
2015-01-01
We present a high-resolution, highly stratified numerical simulation of rotating thermal convection in a spherical shell. Our aim is to study in detail the processes that can maintain a near surface shear layer (NSSL) as inferred from helioseismology. Using the reduced speed of sound technique, we can extend our global convection simulation to 0.99 R {sub ☉} and include, near the top of our domain, small-scale convection with short timescales that is only weakly influenced by rotation. We find the formation of an NSSL preferentially in high latitudes in the depth range of r = 0.95-0.975 R {sub ☉}. The maintenance mechanisms are summarized as follows. Convection under the weak influence of rotation leads to Reynolds stresses that transport angular momentum radially inward in all latitudes. This leads to the formation of a strong poleward-directed meridional flow and an NSSL, which is balanced in the meridional plane by forces resulting from the 〈v{sub r}{sup ′}v{sub θ}{sup ′}〉 correlation of turbulent velocities. The origin of the required correlations depends to some degree on latitude. In high latitudes, a positive correlation 〈v{sub r}{sup ′}v{sub θ}{sup ′}〉 is induced in the NSSL by the poleward meridional flow whose amplitude increases with the radius, while a negative correlation is generated by the Coriolis force in bulk of the convection zone. In low latitudes, a positive correlation 〈v{sub r}{sup ′}v{sub θ}{sup ′}〉 results from rotationally aligned convection cells ({sup b}anana cells{sup )}. The force caused by these Reynolds stresses is in balance with the Coriolis force in the NSSL.
Droplet breakup dynamics of weakly viscoelastic fluids
Marshall, Kristin; Walker, Travis
2016-11-01
The addition of macromolecules to solvent, even in dilute quantities, can alter a fluid's response in an extensional flow. For low-viscosity fluids, the presence of elasticity may not be apparent when measured using a standard rotational rheometer, yet it may still alter the response of a fluid when undergoing an extensional deformation, especially at small length scales where elastic effects are enhanced. Applications such as microfluidics necessitate investigating the dynamics of fluids with elastic properties that are not pronounced at large length scales. In the present work, a microfluidic cross-slot configuration is used to study the effects of elasticity on droplet breakup. Droplet breakup and the subsequent iterated-stretching - where beads form along a filament connecting two primary droplets - were observed for a variety of material and flow conditions. We present a relationship on the modes of bead formation and how and when these modes will form based on key parameters such as the properties of the outer continuous-phase fluid. The results are vital not only for simulating the droplet breakup of weakly viscoelastic fluids but also for understanding how the droplet breakup event can be used for characterizing the extensional properties of weakly-viscoelastic fluids.
Two-fluid-sourced rotating wormholes
Azreg-Aïnou, Mustapha
2016-01-01
We briefly discuss some of the known and new properties of rotating geometries that are relevant to this work. We generalize the analytical method of superposition of fields, known for generating nonrotating solutions, and apply it to construct massless and massive rotating physical wormholes sourced by a source-free electromagnetic field and an exotic fluid both anisotropic. Their stress-energy tensors are presented in compact and general forms. For the massive rotating wormholes there exists a mass-charge constraint yielding almost no more dragging effects than ordinary stars. There are conical spirals through the throat along which the null and weak energy conditions are not violated for these rotating wormholes. This conclusion extends to nonrotating massive type I wormholes derived previously by the author that seem to be the first kind of nonrotating wormholes with this property.
On obliquely magnetized and differentially rotating stars
Wei, Xing
2015-01-01
We investigate the interaction of differential rotation and a misaligned magnetic field. The incompressible magnetohydrodynamic equations are solved numerically for a free-decay problem. In the kinematic limit, differential rotation annihilates the non-axisymmetric field on a timescale proportional to the cube root of magnetic Reynolds number ($Rm$), as predicted by R\\"adler. Nonlinearly, the outcome depends upon the initial energy in the non-axisymmetric part of the field. Sufficiently weak fields approach axisymmetry as in the kinematic limit; some differential rotation survives across magnetic surfaces, at least on intermediate timescales. Stronger fields enforce uniform rotation and remain non-axisymmetric. The initial field strength that divides these two regimes does not follow the scaling $Rm^{-1/3}$ predicted by quasi-kinematic arguments, perhaps because our $Rm$ is never sufficiently large or because of reconnection. We discuss the possible relevance of these results to tidal synchronization and tida...
Rodgers-Lee, Donna; Downes, Turlough P
2016-01-01
The redistribution of angular momentum is a long standing problem in our understanding of protoplanetary disk (PPD) evolution. The magnetorotational instability (MRI) is considered a likely mechanism. We present the results of a study involving multifluid global simulations including Ohmic dissipation, ambipolar diffusion and the Hall effect in a dynamic, self-consistent way. We focus on the turbulence resulting from the non-linear development of the MRI in radially stratified PPDs and compare with ideal MHD simulations. In the multifluid simulations the disk is initially set up to transition from a weak Hall dominated regime, where the Hall effect is the dominant non-ideal effect but approximately the same as or weaker than the inductive term, to a strong Hall dominated regime, where the Hall effect dominates the inductive term. As the simulations progress a substantial portion of the disk develops into a weak Hall dominated disk. We find a transition from turbulent to laminar flow in the inner regions of th...
FC-normal and extended stratified logic program
Institute of Scientific and Technical Information of China (English)
许道云; 丁德成
2002-01-01
This paper investigates the consistency property of FC-normal logic program and presentsan equivalent deciding condition whether a logic program P is an FC-normal program. The decidingcondition describes the characterizations of FC-normal program. By the Petri-net presentation ofa logic program, the characterizations of stratification of FC-normal program are investigated. Thestratification of FC-normal program motivates us to introduce a new kind of stratification, extendedstratification, over logic program. It is shown that an extended (locally) stratified logic program isan FC-normal program. Thus, an extended (locally) stratified logic program has at least one stablemodel. Finally, we have presented algorithms about computation of consistency property and a fewequivalent deciding methods of the finite FC-normal program.
Turbulent thermal diffusion in strongly stratified turbulence: theory and experiments
Amir, G; Eidelman, A; Elperin, T; Kleeorin, N; Rogachevskii, I
2016-01-01
Turbulent thermal diffusion is a combined effect of the temperature stratified turbulence and inertia of small particles. It causes the appearance of a non-diffusive turbulent flux of particles in the direction of the turbulent heat flux. This non-diffusive turbulent flux of particles is proportional to the product of the mean particle number density and the effective velocity of inertial particles. The theory of this effect has been previously developed only for small temperature gradients and small Stokes numbers (Phys. Rev. Lett. {\\bf 76}, 224, 1996). In this study a generalized theory of turbulent thermal diffusion for arbitrary temperature gradients and Stokes numbers has been developed. The laboratory experiments in the oscillating grid turbulence and in the multi-fan produced turbulence have been performed to validate the theory of turbulent thermal diffusion in strongly stratified turbulent flows. It has been shown that the ratio of the effective velocity of inertial particles to the characteristic ve...
Helicity dynamics in stratified turbulence in the absence of forcing
Rorai, C; Pouquet, A; Mininni, P D
2012-01-01
A numerical study of decaying stably-stratified flows is performed. Relatively high stratification and moderate Reynolds numbers are considered, and a particular emphasis is placed on the role of helicity (velocity-vorticity correlations). The problem is tackled by integrating the Boussinesq equations in a periodic cubical domain using different initial conditions: a non-helical Taylor-Green (TG) flow, a fully helical Beltrami (ABC) flow, and random flows with a tunable helicity. We show that for stratified ABC flows helicity undergoes a substantially slower decay than for unstratified ABC flows. This fact is likely associated to the combined effect of stratification and large scale coherent structures. Indeed, when the latter are missing, as in random flows, helicity is rapidly destroyed by the onset of gravitational waves. A type of large-scale dissipative "cyclostrophic" balance can be invoked to explain this behavior. When helicity survives in the system it strongly affects the temporal energy decay and t...
Axisymmetric modes in vertically stratified self-gravitating discs
Mamatsashvili, George
2010-01-01
We perform linear analysis of axisymmetric vertical normal modes in stratified compressible self-gravitating polytropic discs in the shearing box approximation. We study specific dynamics for subadiabatic, adiabatic and superadiabatic vertical stratifications. In the absence of self-gravity, four well-known principal modes can be identified in a stratified disc: acoustic p-, surface gravity f-, buoyancy g- and inertial r-modes. After characterizing modes in the non-self-gravitating case, we include self-gravity and investigate how it modifies the properties of these modes. We find that self-gravity, to a certain degree, reduces their frequencies and changes the structure of the dispersion curves and eigenfunctions at radial wavelengths comparable to the disc height. Its influence on the basic branch of the r-mode, in the case of subadiabatic and adiabatic stratifications, and on the basic branch of the g-mode, in the case of superadiabatic stratification (which in addition exhibits convective instability), do...
Elementary stratified flows with stability at low Richardson number
Energy Technology Data Exchange (ETDEWEB)
Barros, Ricardo [Mathematics Applications Consortium for Science and Industry (MACSI), Department of Mathematics and Statistics, University of Limerick, Limerick (Ireland); Choi, Wooyoung [Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102-1982 (United States)
2014-12-15
We revisit the stability analysis for three classical configurations of multiple fluid layers proposed by Goldstein [“On the stability of superposed streams of fluids of different densities,” Proc. R. Soc. A. 132, 524 (1931)], Taylor [“Effect of variation in density on the stability of superposed streams of fluid,” Proc. R. Soc. A 132, 499 (1931)], and Holmboe [“On the behaviour of symmetric waves in stratified shear layers,” Geophys. Publ. 24, 67 (1962)] as simple prototypes to understand stability characteristics of stratified shear flows with sharp density transitions. When such flows are confined in a finite domain, it is shown that a large shear across the layers that is often considered a source of instability plays a stabilizing role. Presented are simple analytical criteria for stability of these low Richardson number flows.
Experiments on the dryout behavior of stratified debris beds
Energy Technology Data Exchange (ETDEWEB)
Leininger, Simon; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)
2015-10-15
In case of a severe accident with loss of coolant and core meltdown a particle bed (debris) can be formed. The removal of decay heat from the debris bed is of prime importance for the bed's long-term coolability to guarantee the integrity of the RPV. In contrast to previous experiments, the focus is on stratified beds. The experiments have pointed out that the bed's coolability is significantly affected.
Computation of mixing in large stably stratified enclosures
Zhao, Haihua
This dissertation presents a set of new numerical models for the mixing and heat transfer problems in large stably stratified enclosures. Basing on these models, a new computer code, BMIX++ (Berkeley mechanistic MIXing code in C++), was developed by Christensen (2001) and the author. Traditional lumped control volume methods and zone models cannot model the detailed information about the distributions of temperature, density, and pressure in enclosures and therefore can have significant errors. 2-D and 3-D CFD methods require very fine grid resolution to resolve thin substructures such as jets, wall boundaries, yet such fine grid resolution is difficult or impossible to provide due to computational expense. Peterson's scaling (1994) showed that stratified mixing processes in large stably stratified enclosures can be described using one-dimensional differential equations, with the vertical transport by free and wall jets modeled using standard integral techniques. This allows very large reductions in computational effort compared to three-dimensional numerical modeling of turbulent mixing in large enclosures. The BMIX++ code was developed to implement the above ideas. The code uses a Lagrangian approach to solve 1-D transient governing equations for the ambient fluid and uses analytical models or 1-D integral models to compute substructures. 1-D transient conduction model for the solid boundaries, pressure computation and opening models are also included to make the code more versatile. The BMIX++ code was implemented in C++ and the Object-Oriented-Programming (OOP) technique was intensively used. The BMIX++ code was successfully applied to different types of mixing problems such as stratification in a water tank due to a heater inside, water tank exchange flow experiment simulation, early stage building fire analysis, stratification produced by multiple plumes, and simulations for the UCB large enclosure experiments. Most of these simulations gave satisfying
A statistical mechanics approach to mixing in stratified fluids
Venaille, A.; Gostiaux, L.; Sommeria, J.
2017-01-01
Predicting how much mixing occurs when a given amount of energy is injected into a Boussinesq fluid is a longstanding problem in stratified turbulence. The huge number of degrees of freedom involved in those processes renders extremely difficult a deterministic approach to the problem. Here we present a statistical mechanics approach yielding prediction for a cumulative, global mixing efficiency as a function of a global Richardson number and the background buoyancy profile.
Corticosteroids and pediatric septic shock outcomes: a risk stratified analysis.
Directory of Open Access Journals (Sweden)
Sarah J Atkinson
Full Text Available The potential benefits of corticosteroids for septic shock may depend on initial mortality risk.We determined associations between corticosteroids and outcomes in children with septic shock who were stratified by initial mortality risk.We conducted a retrospective analysis of an ongoing, multi-center pediatric septic shock clinical and biological database. Using a validated biomarker-based stratification tool (PERSEVERE, 496 subjects were stratified into three initial mortality risk strata (low, intermediate, and high. Subjects receiving corticosteroids during the initial 7 days of admission (n = 252 were compared to subjects who did not receive corticosteroids (n = 244. Logistic regression was used to model the effects of corticosteroids on 28-day mortality and complicated course, defined as death within 28 days or persistence of two or more organ failures at 7 days.Subjects who received corticosteroids had greater organ failure burden, higher illness severity, higher mortality, and a greater requirement for vasoactive medications, compared to subjects who did not receive corticosteroids. PERSEVERE-based mortality risk did not differ between the two groups. For the entire cohort, corticosteroids were associated with increased risk of mortality (OR 2.3, 95% CI 1.3-4.0, p = 0.004 and a complicated course (OR 1.7, 95% CI 1.1-2.5, p = 0.012. Within each PERSEVERE-based stratum, corticosteroid administration was not associated with improved outcomes. Similarly, corticosteroid administration was not associated with improved outcomes among patients with no comorbidities, nor in groups of patients stratified by PRISM.Risk stratified analysis failed to demonstrate any benefit from corticosteroids in this pediatric septic shock cohort.
On the Impact of Bootstrap in Stratified Random Sampling
Institute of Scientific and Technical Information of China (English)
LIU Cheng; ZHAO Lian-wen
2009-01-01
In general the accuracy of mean estimator can be improved by stratified random sampling. In this paper, we provide an idea different from empirical methods that the accuracy can be more improved through bootstrap resampling method under some conditions. The determination of sample size by bootstrap method is also discussed, and a simulation is made to verify the accuracy of the proposed method. The simulation results show that the sample size based on bootstrapping is smaller than that based on central limit theorem.
Dust particle charge distribution in a stratified glow discharge
Energy Technology Data Exchange (ETDEWEB)
Sukhinin, Gennady I [Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Lavrentyev Ave., 1, Novosibirsk 630090 (Russian Federation); Fedoseev, Alexander V [Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Lavrentyev Ave., 1, Novosibirsk 630090 (Russian Federation); Ramazanov, Tlekkabul S [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan); Dzhumagulova, Karlygash N [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan); Amangaliyeva, Rauan Zh [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan)
2007-12-21
The influence of a highly pronounced non-equilibrium characteristic of the electron energy distribution function in a stratified dc glow discharge on the process of dust particle charging in a complex plasma is taken into account for the first time. The calculated particle charge spatial distribution is essentially non-homogeneous and it can explain the vortex motion of particles at the periphery of a dusty cloud obtained in experiments.
Stability of stratified two-phase flows in inclined channels
Barmak, I.; Gelfgat, A. Yu.; Ullmann, A.; Brauner, N.
2016-08-01
Linear stability of the stratified gas-liquid and liquid-liquid plane-parallel flows in the inclined channels is studied with respect to all wavenumber perturbations. The main objective is to predict the parameter regions in which the stable stratified configuration in inclined channels exists. Up to three distinct base states with different holdups exist in the inclined flows, so that the stability analysis has to be carried out for each branch separately. Special attention is paid to the multiple solution regions to reveal the feasibility of the non-unique stable stratified configurations in inclined channels. The stability boundaries of each branch of the steady state solutions are presented on the flow pattern map and are accompanied by the critical wavenumbers and the spatial profiles of the most unstable perturbations. Instabilities of different nature are visualized by the streamlines of the neutrally stable perturbed flows, consisting of the critical perturbation superimposed on the base flow. The present analysis confirms the existence of two stable stratified flow configurations in a region of low flow rates in the countercurrent liquid-liquid flows. These configurations become unstable with respect to the shear mode of instability. It was revealed that in slightly upward inclined flows the lower and middle solutions for the holdup are stable in the part of the triple solution region, while the upper solution is always unstable. In the case of downward flows, in the triple solution region, none of the solutions are stable with respect to the short-wave perturbations. These flows are stable only in the single solution region at low flow rates of the heavy phase, and the long-wave perturbations are the most unstable ones.
Thermal stratification built up in hot water tank with different inlet stratifiers
DEFF Research Database (Denmark)
Dragsted, Janne; Furbo, Simon; Dannemand, Mark
2017-01-01
H is a rigid plastic pipe with holes for each 30 cm. The holes are designed with flaps preventing counter flow into the pipe. The inlet stratifier from EyeCular Technologies ApS is made of a flexible polymer with openings all along the side and in the full length of the stratifier. The flexibility...... in order to elucidate how well thermal stratification is established in the tank with differently designed inlet stratifiers under different controlled laboratory conditions. The investigated inlet stratifiers are from Solvis GmbH & Co KG and EyeCular Technologies ApS. The inlet stratifier from Solvis Gmb...... of the stratifier prevents counterflow. The tests have shown that both types of inlet stratifiers had an ability to create stratification in the test tank under the different test conditions. The stratifier from EyeCular Technologies ApS had a better performance at low flows of 1-2 l/min and the stratifier...
Stratified source-sampling techniques for Monte Carlo eigenvalue analysis.
Energy Technology Data Exchange (ETDEWEB)
Mohamed, A.
1998-07-10
In 1995, at a conference on criticality safety, a special session was devoted to the Monte Carlo ''Eigenvalue of the World'' problem. Argonne presented a paper, at that session, in which the anomalies originally observed in that problem were reproduced in a much simplified model-problem configuration, and removed by a version of stratified source-sampling. In this paper, stratified source-sampling techniques are generalized and applied to three different Eigenvalue of the World configurations which take into account real-world statistical noise sources not included in the model problem, but which differ in the amount of neutronic coupling among the constituents of each configuration. It is concluded that, in Monte Carlo eigenvalue analysis of loosely-coupled arrays, the use of stratified source-sampling reduces the probability of encountering an anomalous result over that if conventional source-sampling methods are used. However, this gain in reliability is substantially less than that observed in the model-problem results.
Stability of stratified two-phase flows in horizontal channels
Barmak, I.; Gelfgat, A.; Vitoshkin, H.; Ullmann, A.; Brauner, N.
2016-04-01
Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems, the stratified flow with a smooth interface is stable only in confined zone of relatively low flow rates, which is in agreement with experiments, but is not predicted by long-wave analysis. Depending on the flow conditions, the critical perturbations can originate mainly at the interface (so-called "interfacial modes of instability") or in the bulk of one of the phases (i.e., "shear modes"). The present analysis revealed that there is no definite correlation between the type of instability and the perturbation wavelength.
Continuous Dependence on the Density for Stratified Steady Water Waves
Chen, Robin Ming; Walsh, Samuel
2016-02-01
There are two distinct regimes commonly used to model traveling waves in stratified water: continuous stratification, where the density is smooth throughout the fluid, and layer-wise continuous stratification, where the fluid consists of multiple immiscible strata. The former is the more physically accurate description, but the latter is frequently more amenable to analysis and computation. By the conservation of mass, the density is constant along the streamlines of the flow; the stratification can therefore be specified by prescribing the value of the density on each streamline. We call this the streamline density function. Our main result states that, for every smoothly stratified periodic traveling wave in a certain small-amplitude regime, there is an L ∞ neighborhood of its streamline density function such that, for any piecewise smooth streamline density function in that neighborhood, there is a corresponding traveling wave solution. Moreover, the mapping from streamline density function to wave is Lipschitz continuous in a certain function space framework. As this neighborhood includes piecewise smooth densities with arbitrarily many jump discontinues, this theorem provides a rigorous justification for the ubiquitous practice of approximating a smoothly stratified wave by a layered one. We also discuss some applications of this result to the study of the qualitative features of such waves.
Survival analysis of cervical cancer using stratified Cox regression
Purnami, S. W.; Inayati, K. D.; Sari, N. W. Wulan; Chosuvivatwong, V.; Sriplung, H.
2016-04-01
Cervical cancer is one of the mostly widely cancer cause of the women death in the world including Indonesia. Most cervical cancer patients come to the hospital already in an advanced stadium. As a result, the treatment of cervical cancer becomes more difficult and even can increase the death's risk. One of parameter that can be used to assess successfully of treatment is the probability of survival. This study raises the issue of cervical cancer survival patients at Dr. Soetomo Hospital using stratified Cox regression based on six factors such as age, stadium, treatment initiation, companion disease, complication, and anemia. Stratified Cox model is used because there is one independent variable that does not satisfy the proportional hazards assumption that is stadium. The results of the stratified Cox model show that the complication variable is significant factor which influent survival probability of cervical cancer patient. The obtained hazard ratio is 7.35. It means that cervical cancer patient who has complication is at risk of dying 7.35 times greater than patient who did not has complication. While the adjusted survival curves showed that stadium IV had the lowest probability of survival.
Differential rotation of the unstable nonlinear r -modes
Friedman, John L.; Lindblom, Lee; Lockitch, Keith H.
2016-01-01
At second order in perturbation theory, the r -modes of uniformly rotating stars include an axisymmetric part that can be identified with differential rotation of the background star. If one does not include radiation reaction, the differential rotation is constant in time and has been computed by Sá. It has a gauge dependence associated with the family of time-independent perturbations that add differential rotation to the unperturbed equilibrium star: For stars with a barotropic equation of state, one can add to the time-independent second-order solution arbitrary differential rotation that is stratified on cylinders (that is a function of distance ϖ to the axis of rotation). We show here that the gravitational radiation-reaction force that drives the r -mode instability removes this gauge freedom; the exponentially growing differential rotation of the unstable second-order r -mode is unique. We derive a general expression for this rotation law for Newtonian models and evaluate it explicitly for slowly rotating models with polytropic equations of state.
Coherent spin-rotational dynamics of oxygen super rotors
Milner, Alexander A; Milner, Valery
2014-01-01
We use state- and time-resolved coherent Raman spectroscopy to study the rotational dynamics of oxygen molecules in ultra-high rotational states. While it is possible to reach rotational quantum numbers up to $N \\approx 50$ by increasing the gas temperature to 1500 K, low population levels and gas densities result in correspondingly weak optical response. By spinning O$_2$ molecules with an optical centrifuge, we efficiently excite extreme rotational states with $N\\leqslant 109$ in high-density room temperature ensembles. Fast molecular rotation results in the enhanced robustness of the created rotational wave packets against collisions, enabling us to observe the effects of weak spin-rotation coupling in the coherent rotational dynamics of oxygen. The decay rate of spin-rotation coherence due to collisions is measured as a function of the molecular angular momentum and explained in terms of the general scaling law. We find that at high values of $N$, the rotational decoherence of oxygen is much faster than t...
Precision Metrology Using Weak Measurements
Zhang, Lijian; Datta, Animesh; Walmsley, Ian A.
2015-05-01
Weak values and measurements have been proposed as a means to achieve dramatic enhancements in metrology based on the greatly increased range of possible measurement outcomes. Unfortunately, the very large values of measurement outcomes occur with highly suppressed probabilities. This raises three vital questions in weak-measurement-based metrology. Namely, (Q1) Does postselection enhance the measurement precision? (Q2) Does weak measurement offer better precision than strong measurement? (Q3) Is it possible to beat the standard quantum limit or to achieve the Heisenberg limit with weak measurement using only classical resources? We analyze these questions for two prototypical, and generic, measurement protocols and show that while the answers to the first two questions are negative for both protocols, the answer to the last is affirmative for measurements with phase-space interactions, and negative for configuration space interactions. Our results, particularly the ability of weak measurements to perform at par with strong measurements in some cases, are instructive for the design of weak-measurement-based protocols for quantum metrology.
Precision metrology using weak measurements.
Zhang, Lijian; Datta, Animesh; Walmsley, Ian A
2015-05-29
Weak values and measurements have been proposed as a means to achieve dramatic enhancements in metrology based on the greatly increased range of possible measurement outcomes. Unfortunately, the very large values of measurement outcomes occur with highly suppressed probabilities. This raises three vital questions in weak-measurement-based metrology. Namely, (Q1) Does postselection enhance the measurement precision? (Q2) Does weak measurement offer better precision than strong measurement? (Q3) Is it possible to beat the standard quantum limit or to achieve the Heisenberg limit with weak measurement using only classical resources? We analyze these questions for two prototypical, and generic, measurement protocols and show that while the answers to the first two questions are negative for both protocols, the answer to the last is affirmative for measurements with phase-space interactions, and negative for configuration space interactions. Our results, particularly the ability of weak measurements to perform at par with strong measurements in some cases, are instructive for the design of weak-measurement-based protocols for quantum metrology.
Acute muscular weakness in children
Directory of Open Access Journals (Sweden)
Ricardo Pablo Javier Erazo Torricelli
Full Text Available ABSTRACT Acute muscle weakness in children is a pediatric emergency. During the diagnostic approach, it is crucial to obtain a detailed case history, including: onset of weakness, history of associated febrile states, ingestion of toxic substances/toxins, immunizations, and family history. Neurological examination must be meticulous as well. In this review, we describe the most common diseases related to acute muscle weakness, grouped into the site of origin (from the upper motor neuron to the motor unit. Early detection of hyperCKemia may lead to a myositis diagnosis, and hypokalemia points to the diagnosis of periodic paralysis. Ophthalmoparesis, ptosis and bulbar signs are suggestive of myasthenia gravis or botulism. Distal weakness and hyporeflexia are clinical features of Guillain-Barré syndrome, the most frequent cause of acute muscle weakness. If all studies are normal, a psychogenic cause should be considered. Finding the etiology of acute muscle weakness is essential to execute treatment in a timely manner, improving the prognosis of affected children.
The role of Stewartson and Ekman layers in turbulent rotating Rayleigh-Bénard convection
Kunnen, Rudie P.J.; Stevens, Richard Johannes Antonius Maria; Overkamp, Jim; Sun, Chao; van Heijst, GertJan F.; Clercx, H.J.H.
2011-01-01
When the classical Rayleigh–Bénard (RB) system is rotated about its vertical axis roughly three regimes can be identified. In regime I (weak rotation) the largescale circulation (LSC) is the dominant feature of the flow. In regime II (moderate rotation) the LSC is replaced by vertically aligned
Neutrino oscillations in the field of a rotating deformed mass
Energy Technology Data Exchange (ETDEWEB)
Geralico, A., E-mail: geralico@icra.it [Physics Department and ICRA, University of Rome “La Sapienza”, I-00185 Rome (Italy); Luongo, O., E-mail: orlando.luongo@roma1.infn.it [Physics Department and ICRA, University of Rome “La Sapienza”, I-00185 Rome (Italy); Institute of Nuclear Science, University of Mexico (Mexico)
2012-03-12
The neutrino oscillations in the field of a rotating deformed mass is investigated. The phase shift is evaluated in the case of weak field limit, slow rotation and small deformation. To this aim the Hartle–Thorne metric is used, which is an approximate solution of the vacuum Einstein equations accurate to second order in the rotation parameter a/M and to first order in the mass quadrupole moment q. Implications on atmospheric, solar and astrophysical neutrinos are discussed. -- Highlights: ► We consider neutrino oscillations in the field of a rotating deformed mass. ► We evaluate the phase shift in the case of weak field limit, slow rotation and small deformation. ► Observational implications are discussed.
From solar-like to anti-solar differential rotation in cool stars
Gastine, T; Morin, J; Reiners, A; Wicht, J
2013-01-01
Stellar differential rotation can be separated into two main regimes: solar-like when the equator rotates faster than the poles and anti-solar when the polar regions rotate faster than the equator. We investigate the transition between these two regimes with 3-D numerical simulations of rotating spherical shells. We conduct a systematic parameter study which also includes models from different research groups. We find that the direction of the differential rotation is governed by the contribution of the Coriolis force in the force balance, independently of the model setup (presence of a magnetic field, thickness of the convective layer, density stratification). Rapidly-rotating cases with a small Rossby number yield solar-like differential rotation, while weakly-rotating models sustain anti-solar differential rotation. Close to the transition, the two kinds of differential rotation are two possible bistable states. This study provides theoretical support for the existence of anti-solar differential rotation i...
Axial dependence of optical weak measurements in the critical region
Araujo, Manoel P; Maia, Gabriel G
2015-01-01
The interference between optical beams of different polarizations plays a fundamental role in reproducing the optical analog of the electron spin weak measurement. The extraordinary point in optical weak measurements is represented by the possibility to estimate with great accuracy the Goos-Haenchen (GH) shift by measuring the distance between the peak of the outgoing beams for two opposite rotation angles of the polarizers located before and after the dielectric block. Starting from the numerical calculation of the GH shift, which clearly shows a frequency crossover for incidence near to the critical angle, we present a detailed study of the interference between s and p polarized waves in the critical region. This allows to determine in which conditions it is possible to avoid axial deformations and reproduce the GH curves. In view of a possible experimental implementation, we give the expected weak measurement curves for Gaussian lasers of different beam waist sizes propagating through borosilicate (BK7) an...
... stroke After injury to a nerve During a flare-up of multiple sclerosis (MS) You may feel ... Duchenne) Myotonic dystrophy POISONING Botulism Poisoning ( insecticides , nerve gas) Shellfish poisoning OTHER Not enough healthy red blood ...
Rotational Alignment Altered by Source Position Correlations
Jacobs, Chris S.; Heflin, M. B.; Lanyi, G. E.; Sovers, O. J.; Steppe, J. A.
2010-01-01
In the construction of modern Celestial Reference Frames (CRFs) the overall rotational alignment is only weakly constrained by the data. Therefore, common practice has been to apply a 3-dimensional No-Net-Rotation (NNR) constraint in order to align an under-construction frame to the ICRF. We present evidence that correlations amongst source position parameters must be accounted for in order to properly align a CRF at the 5-10 (mu)as level of uncertainty found in current work. Failure to do so creates errors at the 10-40 (mu)as level.
Peripheral facial weakness (Bell's palsy).
Basić-Kes, Vanja; Dobrota, Vesna Dermanović; Cesarik, Marijan; Matovina, Lucija Zadro; Madzar, Zrinko; Zavoreo, Iris; Demarin, Vida
2013-06-01
Peripheral facial weakness is a facial nerve damage that results in muscle weakness on one side of the face. It may be idiopathic (Bell's palsy) or may have a detectable cause. Almost 80% of peripheral facial weakness cases are primary and the rest of them are secondary. The most frequent causes of secondary peripheral facial weakness are systemic viral infections, trauma, surgery, diabetes, local infections, tumor, immune disorders, drugs, degenerative diseases of the central nervous system, etc. The diagnosis relies upon the presence of typical signs and symptoms, blood chemistry tests, cerebrospinal fluid investigations, nerve conduction studies and neuroimaging methods (cerebral MRI, x-ray of the skull and mastoid). Treatment of secondary peripheral facial weakness is based on therapy for the underlying disorder, unlike the treatment of Bell's palsy that is controversial due to the lack of large, randomized, controlled, prospective studies. There are some indications that steroids or antiviral agents are beneficial but there are also studies that show no beneficial effect. Additional treatments include eye protection, physiotherapy, acupuncture, botulinum toxin, or surgery. Bell's palsy has a benign prognosis with complete recovery in about 80% of patients, 15% experience some mode of permanent nerve damage and severe consequences remain in 5% of patients.
Rotator cuff repair - slideshow
... this page: //medlineplus.gov/ency/presentations/100229.htm Rotator cuff repair - series—Normal anatomy To use the sharing ... to slide 4 out of 4 Overview The rotator cuff is a group of muscles and tendons that ...
Continuity in weak topology:higher order linear systems of ODE
Institute of Scientific and Technical Information of China (English)
2008-01-01
We will introduce a type of Fredholm operators which are shown to have a certain con- tinuity in weak topologies.From this,we will prove that the fundamental matrix solutions of k-th, k≥2,order linear systems of ordinary differential equations are continuous in coefficient matrixes with weak topologies.Consequently,Floquet multipliers and Lyapunov exponents for periodic systems are continuous in weak topologies.Moreover,for the scalar Hill’s equations,Sturm-Liouville eigenvalues, periodic and anti-periodic eigenvalues,and rotation numbers are all continuous in potentials with weak topologies.These results will lead to many interesting variational problems.
The stability of weakly collisional plasmas with thermal and composition gradients
DEFF Research Database (Denmark)
Pessah, M.E.; Chakraborty, S.
2013-01-01
Over the last decade, substantial efforts have been devoted to understanding the stability properties, transport phenomena, and long-term evolution of weakly collisional, magnetized plasmas which are stratified in temperature. The insights gained via these studies have led to a significant...... approximation if heavy elements are able to sediment in the inner region of the galaxy cluster. Motivated by the need to obtain a more complete picture of the dynamical properties of the ICM, we analyze the stability of a weakly collisional, magnetized plane-parallel atmosphere which is stratified in both...... in homogeneous media. We also find that there are new modes which are driven by heat conduction and particle diffusion. We discuss the astrophysical implications of our findings for a representative galaxy cluster where helium has sedimented. Our findings suggest that the core insulation that results from...
DEFF Research Database (Denmark)
Gramkow, Claus
1999-01-01
In this article two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very offten the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...... approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion...
Warping the Weak Gravity Conjecture
Directory of Open Access Journals (Sweden)
Karta Kooner
2016-08-01
Full Text Available The Weak Gravity Conjecture, if valid, rules out simple models of Natural Inflation by restricting their axion decay constant to be sub-Planckian. We revisit stringy attempts to realise Natural Inflation, with a single open string axionic inflaton from a probe D-brane in a warped throat. We show that warped geometries can allow the requisite super-Planckian axion decay constant to be achieved, within the supergravity approximation and consistently with the Weak Gravity Conjecture. Preliminary estimates of the brane backreaction suggest that the probe approximation may be under control. However, there is a tension between large axion decay constant and high string scale, where the requisite high string scale is difficult to achieve in all attempts to realise large field inflation using perturbative string theory. We comment on the Generalized Weak Gravity Conjecture in the light of our results.
Interpolation for weak Orlicz spaces with condition
Institute of Scientific and Technical Information of China (English)
JIAO Yong; PENG LiHua; LIU PeiDe
2008-01-01
An interpolation theorem for weak Orlicz spaces generalized by N-functions satisfying M△ condition is given.It is proved to be true for weak Orlicz martingale spaces by weak atomic decomposition of weak Hardy martingale spaces.And applying the interpolation theorem,we obtain some embedding relationships among weak Orlicz martingale spaces.
Magnetic Field in the Gravitationally Stratified Coronal Loops
Indian Academy of Sciences (India)
B. N. Dwivedi; A. K. Srivastava
2015-03-01
We study the effect of gravitational stratification on the estimation of magnetic fields in the coronal loops. By using the method of MHD seismology of kink waves for the estimation of magnetic field of coronal loops, we derive a new formula for the magnetic field considering the effect of gravitational stratification. The fast-kink wave is a potential diagnostic tool for the estimation of magnetic field in fluxtubes. We consider the eleven kink oscillation cases observed by TRACE between July 1998 and June 2001. We calculate magnetic field in the stratified loops (str) and compare them with the previously calculated absolute magnetic field (abs). The gravitational stratification efficiently affects the magnetic field estimation in the coronal loops as it affects also the properties of kink waves. We find ≈22% increment in the magnetic field for the smallest ( = 72 Mm) while ≈42% increment in the absolute magnetic field for the longest ( = 406 Mm) coronal loops. The magnetic fields str and abs also increase with the number density, if the loop length does not vary much. The increment in the magnetic field due to gravitational stratification is small at the lower number densities, however, it is large at the higher number densities. We find that damping time of kink waves due to phase-mixing is less in the case of gravitationally stratified loops compared to nonstratified ones. This indicates the more rapid damping of kink waves in the stratified loops. In conclusion, we find that the gravitational stratification efficiently affects the estimation of magnetic field and damping time estimation especially in the longer coronal loops.
Experimental Study of Fluorine Transport Rules in Unsaturated Stratified Soil
Institute of Scientific and Technical Information of China (English)
ZHANG Hong-mei; SU Bao-yu; LIU Peng-hua; ZHANG Wei
2007-01-01
With the aid of soil column test models, the transport rules of fluorine contaminants in unsaturated stratified soils are discussed. Curves of F- concentrations at different times and sites in the unsaturated stratified soil were obtained under conditions of continuous injection of fluoride contaminants and water. Based on the analysis of the actual observation data, the values between computed results and observed data were compared. It is shown that the chemical properties of fluorine ions are active. The migration process of fluorine ions in soils is complex. Because of the effect of adsorption and desorption, the curve of the fluorine ion breakthrough curve is not symmetric. Its concentration peak value at each measuring point gradually decays. The tail of the breakthrough curve is long and the process of leaching and purifying using water requires considerable time. Along with the release of OHˉ in the process of fluorine absorption, the pH value of the soil solution changed from neutral to alkalinity during the test process. The first part of the breakthrough curve fitted better than the second part. The main reason is that fluorine does not always exist in the form of fluorinions in groundwater. Given the long test time, fluorinions possibly react with other ions in the soil solution to form complex water-soluble fluorine compounds. Only the retardation factor and source-sink term have been considered in our numerical model, which may leads to errors of computed values. But as a whole the migration rules of fluorine ions are basically correct, which indicates that the established numerical model can be used to simulate the transport rules of fluorine contaminants in unsaturated stratified soils.
Rotations with Rodrigues' Vector
Pina, E.
2011-01-01
The rotational dynamics was studied from the point of view of Rodrigues' vector. This vector is defined here by its connection with other forms of parametrization of the rotation matrix. The rotation matrix was expressed in terms of this vector. The angular velocity was computed using the components of Rodrigues' vector as coordinates. It appears…
DEFF Research Database (Denmark)
Gramkow, Claus
2001-01-01
In this paper two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very often the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...
Rotation-induced nonlinear wavepackets in internal waves
Energy Technology Data Exchange (ETDEWEB)
Whitfield, A. J., E-mail: ashley.whitfield.12@ucl.ac.uk; Johnson, E. R., E-mail: e.johnson@ucl.ac.uk [Department of Mathematics, University College London, London WC1E 6BT (United Kingdom)
2014-05-15
The long time effect of weak rotation on an internal solitary wave is the decay into inertia-gravity waves and the eventual formation of a localised wavepacket. Here this initial value problem is considered within the context of the Ostrovsky, or the rotation-modified Korteweg-de Vries (KdV), equation and a numerical method for obtaining accurate wavepacket solutions is presented. The flow evolutions are described in the regimes of relatively-strong and relatively-weak rotational effects. When rotational effects are relatively strong a second-order soliton solution of the nonlinear Schrödinger equation accurately predicts the shape, and phase and group velocities of the numerically determined wavepackets. It is suggested that these solitons may form from a local Benjamin-Feir instability in the inertia-gravity wave-train radiated when a KdV solitary wave rapidly adjusts to the presence of strong rotation. When rotational effects are relatively weak the initial KdV solitary wave remains coherent longer, decaying only slowly due to weak radiation and modulational instability is no longer relevant. Wavepacket solutions in this regime appear to consist of a modulated KdV soliton wavetrain propagating on a slowly varying background of finite extent.
Rotation-induced nonlinear wavepackets in internal waves
Whitfield, A. J.; Johnson, E. R.
2014-05-01
The long time effect of weak rotation on an internal solitary wave is the decay into inertia-gravity waves and the eventual formation of a localised wavepacket. Here this initial value problem is considered within the context of the Ostrovsky, or the rotation-modified Korteweg-de Vries (KdV), equation and a numerical method for obtaining accurate wavepacket solutions is presented. The flow evolutions are described in the regimes of relatively-strong and relatively-weak rotational effects. When rotational effects are relatively strong a second-order soliton solution of the nonlinear Schrödinger equation accurately predicts the shape, and phase and group velocities of the numerically determined wavepackets. It is suggested that these solitons may form from a local Benjamin-Feir instability in the inertia-gravity wave-train radiated when a KdV solitary wave rapidly adjusts to the presence of strong rotation. When rotational effects are relatively weak the initial KdV solitary wave remains coherent longer, decaying only slowly due to weak radiation and modulational instability is no longer relevant. Wavepacket solutions in this regime appear to consist of a modulated KdV soliton wavetrain propagating on a slowly varying background of finite extent.
2013-01-01
Background Antibiograms created by aggregating hospital-wide susceptibility data from diverse patients can be misleading. To demonstrate the utility of age- and location-stratified antibiograms, we compared stratified antibiograms for three common bacterial pathogens, E. coli, S. aureus, and S. pneumoniae. We created stratified antibiograms based on patient age (/=65 years), and inpatient or outpatient location using all 2009 E. coli and S. aureus, and all 2008–2009 S. pneumoniae isolates sub...
Electromagnetism in nonleptonic weak interactions
Energy Technology Data Exchange (ETDEWEB)
Ecker, G. E-mail: ecker@doppler.thp.univie.ac.at; Isidori, G.; Mueller, G.; Neufeld, H.; Pich, A
2000-12-18
We construct a low-energy effective field theory that permits the complete treatment of isospin-breaking effects in nonleptonic weak interactions to next-to-leading order. To this end, we enlarge the chiral Lagrangian describing strong and {delta}S=1 weak interactions by including electromagnetic terms with the photon as additional dynamical degree of freedom. The complete and minimal list of local terms at next-to-leading order is given. We perform the one-loop renormalization at the level of the generating functional and specialize to K{yields}{pi}{pi} decays.
Cosmology and the weak interaction
Energy Technology Data Exchange (ETDEWEB)
Schramm, D.N. (Fermi National Accelerator Lab., Batavia, IL (USA)):(Chicago Univ., IL (USA))
1989-12-01
The weak interaction plays a critical role in modern Big Bang cosmology. This review will emphasize two of its most publicized cosmological connections: Big Bang nucleosynthesis and Dark Matter. The first of these is connected to the cosmological prediction of Neutrino Flavours, N{sub {nu}} {approximately} 3 which is now being confirmed at SLC and LEP. The second is interrelated to the whole problem of galaxy and structure formation in the universe. This review will demonstrate the role of the weak interaction both for dark matter candidates and for the problem of generating seeds to form structure. 87 refs., 3 figs., 5 tabs.
Weak disorder in Fibonacci sequences
Energy Technology Data Exchange (ETDEWEB)
Ben-Naim, E [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Krapivsky, P L [Department of Physics and Center for Molecular Cybernetics, Boston University, Boston, MA 02215 (United States)
2006-05-19
We study how weak disorder affects the growth of the Fibonacci series. We introduce a family of stochastic sequences that grow by the normal Fibonacci recursion with probability 1 - {epsilon}, but follow a different recursion rule with a small probability {epsilon}. We focus on the weak disorder limit and obtain the Lyapunov exponent that characterizes the typical growth of the sequence elements, using perturbation theory. The limiting distribution for the ratio of consecutive sequence elements is obtained as well. A number of variations to the basic Fibonacci recursion including shift, doubling and copying are considered. (letter to the editor)
Electromagnetic fields due to dipole antennas over stratified anisotropic media.
Kong, J. A.
1972-01-01
Solutions to the problem of radiation of dipole antennas in the presence of a stratified anisotropic media are facilitated by decomposing a general wave field into transverse magnetic (TM) and transverse electric (TE) modes. Employing the propagation matrices, wave amplitudes in any region are related to those in any other regions. The reflection coefficients, which embed all the information about the geometrical configuration and the physical constituents of the medium, are obtained in closed form. In view of the general formulation, various special cases are discussed.
Instabilities developed in stratified flows over pronounced obstacles
Varela, J.; Araújo, M.; Bove, I.; Cabeza, C.; Usera, G.; Martí, Arturo C.; Montagne, R.; Sarasúa, L. G.
2007-12-01
In the present work we study numerical and experimentally the flow of a two-layer stratified fluid over a topographic obstacle. The problem reflects a wide number of oceanographic and meteorological situations, where the stratification plays an important role. We identify the different instabilities developed by studying the pycnocline deformation due to a pronounced obstacle. The numerical simulations were made using the model caffa3D.MB which works with a numerical model of Navier-Stokes equations with finite volume elements in curvilinear meshes. The experimental results are contrasted with numerical simulations. Linear stability analysis predictions are checked with particle image velocimetry (PIV) measurements.
Stratified waveguide grating coupler for normal fiber incidence.
Wang, Bin; Jiang, Jianhua; Chambers, Diana M; Cai, Jingbo; Nordin, Gregory P
2005-04-15
We propose a new stratified waveguide grating coupler (SWGC) to couple light from a fiber at normal incidence into a planar waveguide. SWGCs are designed to operate in the strong coupling regime without intermediate optics between the fiber and the waveguide. Two-dimensional finite-difference time-domain simulation in conjunction with microgenetic algorithm optimization shows that approximately 72% coupling efficiency is possible for fiber (core size of 8.3 microm and delta=0.36%) to slab waveguide (1.2-microm core and delta=3.1%) coupling. We show that the phase-matching and Bragg conditions are simultaneously satisfied through the fundamental leaky mode.
Enhanced charge transport kinetics in anisotropic, stratified photoanodes.
Yazdani, Nuri; Bozyigit, Deniz; Utke, Ivo; Buchheim, Jakob; Youn, Seul Ki; Patscheider, Jörg; Wood, Vanessa; Park, Hyung Gyu
2014-02-12
The kinetics of charge transport in mesoporous photoanodes strongly constrains the design and power conversion efficiencies of dye sensitized solar cells (DSSCs). Here, we report a stratified photoanode design with enhanced kinetics achieved through the incorporation of a fast charge transport intermediary between the titania and charge collector. Proof of concept photoanodes demonstrate that the inclusion of the intermediary not only enhances effective diffusion coefficients but also significantly suppresses charge recombination, leading to diffusion lengths two orders of magnitude greater than in standard mesoporous titania photoanodes. The intermediary concept holds promise for higher-efficiency DSSCs.
Differential rotation of the unstable nonlinear r-modes
Friedman, John L; Lockitch, Keith H
2016-01-01
At second order in perturbation theory, the $r$-modes of uniformly rotating stars include an axisymmetric part that can be identified with differential rotation of the background star. If one does not include radiation-reaction, the differential rotation is constant in time and has been computed by S\\'a. It has a gauge dependence associated with the family of time-independent perturbations that add differential rotation to the unperturbed equilibrium star: For stars with a barotropic equation of state, one can add to the time-independent second-order solution arbitrary differential rotation that is stratified on cylinders (that is a function of distance $\\varpi$ to the axis of rotation). We show here that the gravitational radiation-reaction force that drives the $r$-mode instability removes this gauge freedom: The expontially growing differential rotation of the unstable second-order $r$-mode is unique. We derive a general expression for this rotation law for Newtonian models and evaluate it explicitly for s...
Vortex bursting and tracer transport of a counter-rotating vortex pair
Misaka, T.; Holzäpfel, F.; Hennemann, I.; Gerz, T.; Manhart, M.; Schwertfirm, F.
2012-02-01
Large-eddy simulations of a coherent counter-rotating vortex pair in different environments are performed. The environmental background is characterized by varying turbulence intensities and stable temperature stratifications. Turbulent exchange processes between the vortices, the vortex oval, and the environment, as well as the material redistribution processes along the vortex tubes are investigated employing passive tracers that are superimposed to the initial vortex flow field. It is revealed that the vortex bursting phenomenon, known from photos of aircraft contrails or smoke visualization, is caused by collisions of secondary vortical structures traveling along the vortex tube which expel material from the vortex but do not result in a sudden decay of circulation or an abrupt change of vortex core structure. In neutrally stratified and weakly turbulent conditions, vortex reconnection triggers traveling helical vorticity structures which is followed by their collision. A long-lived vortex ring links once again establishing stable double rings. Key phenomena observed in the simulations are supported by photographs of contrails. The vertical and lateral extents of the detrained passive tracer strongly depend on environmental conditions where the sensitivity of detrainment rates on initial tracer distributions appears to be low.
A-Stratified Computerized Adaptive Testing with Unequal Item Exposure across Strata.
Deng, Hui; Chang, Hua-Hua
The purpose of this study was to compare a proposed revised a-stratified, or alpha-stratified, USTR method of test item selection with the original alpha-stratified multistage computerized adaptive testing approach (STR) and the use of maximum Fisher information (FSH) with respect to test efficiency and item pool usage using simulated computerized…
The cohomology group of weak entwining structure
Institute of Scientific and Technical Information of China (English)
2007-01-01
In this paper, we reveal that a weak entwining structure admits a rich cohomology theory. As an application we compute the cohomology of a weak entwining structure associated to a weak coalgebra-Galois extension.
Second threshold in weak interactions
Veltman, M.J.G.
1977-01-01
The point of view that weak interactions must have a second threshold below 300 – 600 GeV is developed. Above this threshold new physics must come in. This new physics may be the Higgs system, or some other nonperturbative system possibly having some similarities to the Higgs system. The limit of la
Beam splitting on weak illumination.
Snyder, A W; Buryak, A V; Mitchell, D J
1998-01-01
We demonstrate, in both two and three dimensions, how a self-guided beam in a non-Kerr medium is split into two beams on weak illumination. We also provide an elegant physical explanation that predicts the universal character of the observed phenomenon. Possible applications of our findings to guiding light with light are also discussed.
Weak measurements and supraluminal communication
Belinsky, A V
2016-01-01
There is suggested a version of the experiment with a correlated pair of particles in the entangled state. The experiment demonstrates that, in the case of weak and/or non-demolition measurements of one of the particles, it is possible to transmit information with a speed not limited by velocity of light.
Thomys, Janus; Zhang, Xiaohong
2013-01-01
We describe weak-BCC-algebras (also called BZ-algebras) in which the condition (x∗y)∗z = (x∗z)∗y is satisfied only in the case when elements x, y belong to the same branch. We also characterize ideals, nilradicals, and nilpotent elements of such algebras. PMID:24311983
Eldercare at Home: Bone Weakness
... socialize. This can make exercising fun. If you don't exercise, your bones and muscles will become weak and your chances of falling will increase. Let’s exercise together. I will pick you up and we will go to the mall and walk for a little ...
Submanifolds Weakly Associated with Graphs
Indian Academy of Sciences (India)
A Carriazo; L M Fernández; A Rodríguez-Hidalgo
2009-06-01
We establish an interesting link between differential geometry and graph theory by defining submanifolds weakly associated with graphs. We prove that, in a local sense, every submanifold satisfies such an association, and other general results. Finally, we study submanifolds associated with graphs either in low dimensions or belonging to some special families.
The Fastest Rotating Pulsar: a Strange Star?
Institute of Scientific and Technical Information of China (English)
徐仁新; 徐轩彬; 吴鑫基
2001-01-01
According to the observational limits on the radius and mass, the fastest rotating pulsar (PSR 1937+21) is probably a strange star, or at least some neutron star equations of state should be ruled out, if we suggest that a dipole magnetic field is relevant to its radio emission. We presume that the millisecond pulsar is a strange star with much low mass, small radius and weak magnetic moment.
Stochl, Jan; Croudace, Tim
2013-01-01
Why some humans prefer to rotate clockwise rather than anticlockwise is not well understood. This study aims to identify the predictors of the preferred rotation direction in humans. The variables hypothesised to influence rotation preference include handedness, footedness, sex, brain hemisphere lateralisation, and the Coriolis effect (which results from geospatial location on the Earth). An online questionnaire allowed us to analyse data from 1526 respondents in 97 countries. Factor analysis showed that the direction of rotation should be studied separately for local and global movements. Handedness, footedness, and the item hypothesised to measure brain hemisphere lateralisation are predictors of rotation direction for both global and local movements. Sex is a predictor of the direction of global rotation movements but not local ones, and both sexes tend to rotate clockwise. Geospatial location does not predict the preferred direction of rotation. Our study confirms previous findings concerning the influence of handedness, footedness, and sex on human rotation; our study also provides new insight into the underlying structure of human rotation movements and excludes the Coriolis effect as a predictor of rotation.
Sequential stratified sampling belief propagation for multiple targets tracking
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Rather than the difficulties of highly non-linear and non-Gaussian observation process and the state distribution in single target tracking, the presence of a large, varying number of targets and their interactions place more challenge on visual tracking. To overcome these difficulties, we formulate multiple targets tracking problem in a dynamic Markov network which consists of three coupled Markov random fields that model the following: a field for joint state of multi-target, one binary process for existence of individual target, and another binary process for occlusion of dual adjacent targets. By introducing two robust functions, we eliminate the two binary processes, and then apply a novel version of belief propagation called sequential stratified sampling belief propagation algorithm to obtain the maximum a posteriori (MAP) estimation in the dynamic Markov network. By using stratified sampler, we incorporate bottom-up information provided by a learned detector (e.g. SVM classifier) and belief information for the messages updating. Other low-level visual cues (e.g. color and shape) can be easily incorporated in our multi-target tracking model to obtain better tracking results. Experimental results suggest that our method is comparable to the state-of-the-art multiple targets tracking methods in several test cases.
Penetrative convection in stratified fluids: velocity and temperature measurements
Directory of Open Access Journals (Sweden)
M. Moroni
2006-01-01
Full Text Available The flux through the interface between a mixing layer and a stable layer plays a fundamental role in characterizing and forecasting the quality of water in stratified lakes and in the oceans, and the quality of air in the atmosphere. The evolution of the mixing layer in a stably stratified fluid body is simulated in the laboratory when "Penetrative Convection" occurs. The laboratory model consists of a tank filled with water and subjected to heating from below. The methods employed to detect the mixing layer growth were thermocouples for temperature data and two image analysis techniques, namely Laser Induced Fluorescence (LIF and Feature Tracking (FT. LIF allows the mixing layer evolution to be visualized. Feature Tracking is used to detect tracer particle trajectories moving within the measurement volume. Pollutant dispersion phenomena are naturally described in the Lagrangian approach as the pollutant acts as a tag of the fluid particles. The transilient matrix represents one of the possible tools available for quantifying particle dispersion during the evolution of the phenomenon.
STRESS DISTRIBUTION IN THE STRATIFIED MASS CONTAINING VERTICAL ALVEOLE
Directory of Open Access Journals (Sweden)
Bobileva Tatiana Nikolaevna
2017-08-01
Full Text Available Almost all subsurface rocks used as foundations for various types of structures are stratified. Such heterogeneity may cause specific behaviour of the materials under strain. Differential equations describing the behaviour of such materials contain rapidly fluctuating coefficients, in view of this, solution of such equations is more time-consuming when using today’s computers. The method of asymptotic averaging leads to getting homogeneous medium under study to averaged equations with fixed factors. The present article is concerned with stratified soil mass consisting of pair-wise alternative isotropic elastic layers. In the results of elastic modules averaging, the present soil mass with horizontal rock stratification is simulated by homogeneous transversal-isotropic half-space with isotropy plane perpendicular to the standing axis. Half-space is loosened by a vertical alveole of circular cross-section, and virgin ground is under its own weight. For horizontal parting planes of layers, the following two types of surface conditions are set: ideal contact and backlash without cleavage. For homogeneous transversal-isotropic half-space received with a vertical alveole, the analytical solution of S.G. Lekhnitsky, well known in scientific papers, is used. The author gives expressions for stress components and displacements in soil mass for different marginal conditions on the alveole surface. Such research problems arise when constructing and maintaining buildings and when composite materials are used.
Stability of steam-water countercurrent stratified flow
Energy Technology Data Exchange (ETDEWEB)
Lee, S C
1985-10-01
Two flow instabilities which limit the normal condensation processes in countercurrent stratified steam-water flow have been identified experimentally: flooding and condensation-induced waterhammer. In order to initiate condensation-induced waterhammer in nearly horizontal or moderately-inclined steam/subcooled-water flow, two conditions, the appearance of a wavy interface and complete condensation of the incoming steam, are necessary. Analyses of these conditions are performed on a basis of flow stability and heat transfer considerations. Flooding data for several inclinations and channel heights are collected. Effects of condensation, inclination angle and channel height on the flooding characteristics are discussed. An envelope theory for the onset of flooding in inclined stratified flow is developed, which agrees well with the experimental data. Some empirical information on basic flow parameters, such as mean film thickness and interfacial friction factor required for this theory are measured. The previous viewpoints on flooding appear not to conflict with the present experimental data in nearly horizontal flow but the flooding phenomena in nearly vertical flow appear to be more complicated than those described by these viewpoints because of liquid droplet entrainment.
DEFF Research Database (Denmark)
Rasmusson, Allan; Hahn, Ute; Larsen, Jytte Overgaard
2013-01-01
to identify the specific tissue region under study. In order to use the spatial rotator in practice, however, it is necessary to be able to identify intersection points between cell boundaries and test rays in a series of parallel focal planes, also at the peripheral parts of the cell boundaries. In cases......This paper presents a new local volume estimator, the spatial rotator, which is based on measurements on a virtual 3D probe, using computer assisted microscopy. The basic design of the probe builds upon the rotator principle which requires only a few manual intersection markings, thus making...... the spatial rotator fast to use. Since a 3D probe is involved, it is expected that the spatial rotator will be more efficient than the the nucleator and the planar rotator, which are based on measurements in a single plane. An extensive simulation study shows that the spatial rotator may be more efficient...
Strongly Stratified Turbulence Wakes and Mixing Produced by Fractal Wakes
Dimitrieva, Natalia; Redondo, Jose Manuel; Chashechkin, Yuli; Fraunie, Philippe; Velascos, David
2017-04-01
This paper describes Shliering and Shadowgraph experiments of the wake induced mixing produced by tranversing a vertical or horizontal fractal grid through the interfase between two miscible fluids at low Atwood and Reynolds numbers. This is a configuration design to models the mixing across isopycnals in stably-stratified flows in many environmental relevant situations (either in the atmosphere or in the ocean. The initial unstable stratification is characterized by a reduced gravity: g' = gΔρ ρ where g is gravity, Δρ being the initial density step and ρ the reference density. Here the Atwood number is A = g' _ 2 g . The topology of the fractal wake within the strong stratification, and the internal wave field produces both a turbulent cascade and a wave cascade, with frecuen parametric resonances, the envelope of the mixing front is found to follow a complex non steady 3rd order polinomial function with a maximum at about 4-5 Brunt-Vaisalla non-dimensional time scales: t/N δ = c1(t/N) + c2g Δρ ρ (t/N)2 -c3(t/N)3. Conductivity probes and Shliering and Shadowgraph visual techniques, including CIV with (Laser induced fluorescence and digitization of the light attenuation across the tank) are used in order to investigate the density gradients and the three-dimensionality of the expanding and contracting wake. Fractal analysis is also used in order to estimate the fastest and slowest growing wavelengths. The large scale structures are observed to increase in wave-length as the mixing progresses, and the processes involved in this increase in scale are also examined.Measurements of the pointwise and horizontally averaged concentrations confirm the picture obtained from past flow visualization studies. They show that the fluid passes through the mixing region with relatively small amounts of molecular mixing,and the molecular effects only dominate on longer time scales when the small scales have penetrated through the large scale structures. The Non
On the weak project construction cost management
Institute of Scientific and Technical Information of China (English)
高守刚; 姜婧; 李玲
2013-01-01
the weak cost management is the most talked about topics in the weak industry, but also the basis of the weak construction business management and focus. With the increasingly fierce market competition, weak construction enterprises, the competition among enterprises wil gradual y transition from product quality competition to price competition. To strengthen the management of the weak construction enterprises cost, cut public spending ef iciency, improve market competitiveness, wil be the main way most weak construction corporate earnings and long-term business strategy. Based on the to weak project construction cost management based on analysis of the type of project construction costs, and further proposed the weak project construction cost management measures.
Algebraic disturbances and their consequences in rotating channel flow transition
Jose, Sharath; Pier, Benoît; Govindarajan, Rama
2016-01-01
It is now established that subcritical mechanisms play a crucial role in the transition to turbulence of non-rotating plane shear flows. The role of these mechanisms in rotating channel flow is examined here in the linear and nonlinear stages. Distinct patterns of behaviour are found: the transient growth leading to nonlinearity at low rotation rates $Ro$, a highly chaotic intermediate $Ro$ regime, a localised weak chaos at higher $Ro$, and complete stabilization of transient disturbances at very high $Ro$. At very low $Ro$, the transient growth amplitudes are close to those for non-rotating flow, but Coriolis forces already assert themselves by producing distinct asymmetry about the channel centreline. Nonlinear processes are then triggered, in a streak-breakdown mode of transition. The high $Ro$ regimes do not show these signatures, here the leading eigenmode emerges as dominant in the early stages. Elongated structures plastered close to one wall are seen at higher rotation rates. Rotation is shown to redu...
Turbulent drag in a rotating frame
Campagne, Antoine; Gallet, Basile; Cortet, Pierre-Philippe; Moisy, Frédéric
2016-01-01
What is the turbulent drag force experienced by an object moving in a rotating fluid? This open and fundamental question can be addressed by measuring the torque needed to drive an impeller at constant angular velocity $\\omega$ in a water tank mounted on a platform rotating at a rate $\\Omega$. We report a dramatic reduction in drag as $\\Omega$ increases, down to values as low as $12$\\% of the non-rotating drag. At small Rossby number $Ro = \\omega/\\Omega$, the decrease in drag coefficient $K$ follows the approximate scaling law $K \\sim Ro$, which is predicted in the framework of nonlinear inertial wave interactions and weak-turbulence theory. However, stereoscopic particle image velocimetry measurements indicate that this drag reduction rather originates from a weakening of the turbulence intensity in line with the two-dimensionalization of the large-scale flow.
[Rotator cuff tear of the hip].
Jeanneret, Luc; Kurmann, Patric T; van Linthoudt, Daniel
2008-05-14
We report the observations of two women with a recurrent periarthritis of the hip complicated by a spontaneous rupture of the tendons of the gluteus medius and minimus. These patients usually complain from an acute lateral hip pain and show a Trendelenburg gait. When the rupture is complete, clinical evaluation reveals a drop of the pelvis on the non-stance side and resisted rotation starting from the extreme external rotation position is weak. MRI plays a key role in the diagnosis and the evaluation of a possible surgical repair. Hip rotator-cuff rupture is probably insufficiently diagnosed by ignorance. Nonetheless, optimized handling could relieve the pain of most these patients and improve the disability of some of them.
Magnetic rotation and chiral symmetry breaking
Indian Academy of Sciences (India)
Ashok Kumar Jain; Amita
2001-08-01
The deformed mean ﬁeld of nuclei exhibits various geometrical and dynamical symmetries which manifest themselves as various types of rotational and decay patterns. Most of the symmetry operations considered so far have been deﬁned for a situation wherein the angular momentum coincides with one of the principal axes and the principal axis cranking may be invoked. New possibilities arise with the observation of rotational features in weakly deformed nuclei and now interpreted as magnetic rotational bands. More than 120 MR bands have now been identiﬁed by ﬁltering the existing data. We present a brief overview of these bands. The total angular momentum vector in such bands is tilted away from the principal axes. Such a situation gives rise to several new possibilities including breaking of chiral symmetry as discussed recently by Frauendorf. We present the outcome of such symmetries and their possible experimental veriﬁcation. Some possible examples of chiral bands are presented.
Manolopoulou, Maria
2016-01-01
We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their...
Constraining stochastic gravitational wave background from weak lensing of CMB B-modes
Shaikh, Shabbir; Rotti, Aditya; Souradeep, Tarun
2016-01-01
A stochastic gravitational wave background (SGWB) will affect the CMB anisotropies via weak lensing. Unlike weak lensing due to large scale structure which only deflects photon trajectories, a SGWB has an additional effect of rotating the polarization vector along the trajectory. We study the relative importance of these two effects, deflection \\& rotation, specifically in the context of E-mode to B-mode power transfer caused by weak lensing due to SGWB. Using weak lensing distortion of the CMB as a probe, we derive constraints on the spectral energy density ($\\Omega_{GW}$) of the SGWB, sourced at different redshifts, without assuming any particular model for its origin. We present these bounds on $\\Omega_{GW}$ for different power-law models characterizing the SGWB, indicating the threshold above which observable imprints of SGWB must be present in CMB.
Constraining stochastic gravitational wave background from weak lensing of CMB B-modes
Shaikh, Shabbir; Mukherjee, Suvodip; Rotti, Aditya; Souradeep, Tarun
2016-09-01
A stochastic gravitational wave background (SGWB) will affect the CMB anisotropies via weak lensing. Unlike weak lensing due to large scale structure which only deflects photon trajectories, a SGWB has an additional effect of rotating the polarization vector along the trajectory. We study the relative importance of these two effects, deflection & rotation, specifically in the context of E-mode to B-mode power transfer caused by weak lensing due to SGWB. Using weak lensing distortion of the CMB as a probe, we derive constraints on the spectral energy density (ΩGW) of the SGWB, sourced at different redshifts, without assuming any particular model for its origin. We present these bounds on ΩGW for different power-law models characterizing the SGWB, indicating the threshold above which observable imprints of SGWB must be present in CMB.
Hall, Lawrence J; Ruderman, Joshua T
2014-01-01
The measured values of the weak scale, $v$, and the first generation masses, $m_{u,d,e}$, are simultaneously explained in the multiverse, with all these parameters scanning independently. At the same time, several remarkable coincidences are understood. Small variations in these parameters away from their measured values lead to the instability of hydrogen, the instability of heavy nuclei, and either a hydrogen or a helium dominated universe from Big Bang Nucleosynthesis. In the 4d parameter space of $(m_u,m_d,m_e,v)$, catastrophic boundaries are reached by separately increasing each parameter above its measured value by a factor of $(1.4,1.3,2.5,\\sim5)$, respectively. The fine-tuning problem of the weak scale in the Standard Model is solved: as $v$ is increased beyond the observed value, it is impossible to maintain a significant cosmological hydrogen abundance for any values of $m_{u,d,e}$ that yield both hydrogen and heavy nuclei stability. For very large values of $v$ a new regime is entered where weak in...
Long ring waves in a stratified fluid over a shear flow
Khusnutdinova, K R
2014-01-01
Oceanic waves registered by satellite observations often have curvilinear fronts and propagate over various currents. In this paper, we study long linear and weakly-nonlinear ring waves in a stratified fluid in the presence of a depth-dependent horizontal shear flow. It is shown that despite the clashing geometries of the waves and the shear flow, there exists a linear modal decomposition (different from the known decomposition in Cartesian geometry), which can be used to describe distortion of the wavefronts of surface and internal waves, and systematically derive a 2+1 - dimensional cylindrical Korteweg - de Vries - type equation for the amplitudes of the waves. The general theory is applied to the case of the waves in a two-layer fluid with a piecewise - constant shear flow, with an emphasis on the effect of the shear flow on the geometry of the wavefronts. The distortion of the wavefronts is described by the singular solution (envelope of the general solution) of the nonlinear first-order differential equ...
Sheared stably stratified turbulence and large-scale waves in a lid driven cavity
Cohen, N; Elperin, T; Kleeorin, N; Rogachevskii, I
2014-01-01
We investigated experimentally stably stratified turbulent flows in a lid driven cavity with a non-zero vertical mean temperature gradient in order to identify the parameters governing the mean and turbulent flows and to understand their effects on the momentum and heat transfer. We found that the mean velocity patterns (e.g., the form and the sizes of the large-scale circulations) depend strongly on the degree of the temperature stratification. In the case of strong stable stratification, the strong turbulence region is located in the vicinity of the main large-scale circulation. We detected the large-scale nonlinear oscillations in the case of strong stable stratification which can be interpreted as nonlinear internal gravity waves. The ratio of the main energy-containing frequencies of these waves in velocity and temperature fields in the nonlinear stage is about 2. The amplitude of the waves increases in the region of weak turbulence (near the bottom wall of the cavity), whereby the vertical mean temperat...
Swimming for survival: A role of phytoplankton motility in a stratified turbulent environment
Ross, Oliver N.; Sharples, Jonathan
We investigate a role for vertical migration in stratified coastal water, where the swimming speed is generally significantly less than the typical turbulent fluctuations in a tidally-mixed bottom layer. In our modelling approach we use a k- ɛ turbulence model to describe the physical forcing, a Lagrangian random walk model to describe the vertical displacement of individual cells in response to turbulence and due to cell motility, and a phytoplankton growth model to direct the swimming behaviour of the phytoplankton according to their light and nutrient requirements. The model results show how the cells form a stable subsurface chlorophyll maximum (SCM) at the base of the thermocline where episodic tidal turbulence causes erosion of part of the SCM biomass into the bottom mixed layer (BML). We then focus on the question of whether an ability to swim (weakly, compared to typical bottom layer turbulent intensities) provides any advantage by allowing return to the SCM. Our results show that tidal turbulence in the BML helps both motile and neutrally-buoyant cells by periodically pushing them into the base of the thermocline. Motile cells then have the advantage that they can swim further into the thermocline towards higher light which also reduces the likelihood of being re-mixed back into the BML.
Institute of Scientific and Technical Information of China (English)
WEI Gang
2004-01-01
This dissertation deals with the internal waves generated by a submerged moving body in stratified fluids by combining theoretical and experimental methods. Our purpose is to provide some scientific evidences for non-acoustic detection of underwater moving bodies based on the principles of dynamics of the internal waves. An approach to velocity potentials obtained by superposing Green's functions of sources and sinks was proposed for Kelvin waves at the free surface or interface in a two-layer fluid. The effects of interacting surface- and internal-wave modes induced by a dipole on the surface divergence field were investigated. A new theoretical model formulating the interaction of a two-dimensional submerged moving body with the conjugate flow in a three-layer fluid was established. An exact solution satisfying the two-dimensional Benjamin-Ono equation was obtained and the vertically propagating properties of the weakly nonlinear long waves were studied by means of the ray theory and WKB method. The above theoretical results are qualitatively consistent with those obtained in the experiments conducted by the author.
The turbulent decay of trailing vortex pairs in stably stratified environments
Energy Technology Data Exchange (ETDEWEB)
Holzaepfel, F.; Gerz, T.; Baumann, R.
2000-03-01
The decay of trailing vortex pairs in thermally stably stratified environments is investigated by means of large eddy simulations. Results of in-situ measurements in the wakes of different aircraft are used to find appropriate intitializations for the simulation of wake turbulence in the quiescent atmosphere. Furthermore, cases with weak atmospheric turbulence are investigated. It is shown that the early development of the vortices is not affected by turbulence and develops almost identically as in 2D simulations. In a quiescent atmosphere the subsequent vortex decay is controlled by the interaction of short-wave disturbances, owing to the aircraft induced turbulence, and baroclinic vorticity, owing to stable stratification. As a consequence, vertical vorticity streaks between the vortices are induced which are substantially intensified by vortex stretching and finally lead to rapid turbulent wake-vortex decay. When in addition also atmospheric turbulence is present, the long-wave instability is dominantly promoted. For very strong stratification (Fr < 1) it is observed that wake vortices may rebound but lose most of their strength before reaching the flight level. Finally, the simulation results are compared to the predictive capabilities of Greene's approximate model. (orig.)
Hydrodynamics of stratified epithelium: steady state and linearized dynamics
Yeh, Wei-Ting
2015-01-01
A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue is assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description for tissue dynamics at long-wavelength, long-time limit is developed, and the analysis reveals important insight for the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface could enhance small perturbations. This destabilizing mechanism is general for continuous self-renewal multi-layered tissues, it could be related to the origin of certain tissue morphology and developing pattern.
Hydrodynamics of stratified epithelium: Steady state and linearized dynamics
Yeh, Wei-Ting; Chen, Hsuan-Yi
2016-05-01
A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.
Local Radiation MHD Instabilities in Magnetically Stratified Media
Tao, Ted
2011-01-01
We study local radiation magnetohydrodynamic instabilities in static, optically thick, vertically stratified media with constant flux mean opacity. We include the effects of vertical gradients in a horizontal background magnetic field. Assuming rapid radiative diffusion, we use the zero gas pressure limit as an entry point for investigating the coupling between the photon bubble instability and the Parker instability. Apart from factors that depend on wavenumber orientation, the Parker instability exists for wavelengths longer than a characteristic wavelength lambda_{tran}, while photon bubbles exist for wavelengths shorter than lambda_{tran}. The growth rate in the Parker regime is independent of the orientation of the horizontal component of the wavenumber when radiative diffusion is rapid, but the range of Parker-like wavenumbers is extended if there exists strong horizontal shear between field lines (i.e. horizontal wavenumber perpendicular to the magnetic field). Finite gas pressure introduces an additio...
The Risk-Stratified Osteoporosis Strategy Evaluation study (ROSE)
DEFF Research Database (Denmark)
Rubin, Katrine Hass; Holmberg, Teresa; Rothmann, Mette Juel
2015-01-01
The risk-stratified osteoporosis strategy evaluation study (ROSE) is a randomized prospective population-based study investigating the effectiveness of a two-step screening program for osteoporosis in women. This paper reports the study design and baseline characteristics of the study population....... 35,000 women aged 65-80 years were selected at random from the population in the Region of Southern Denmark and-before inclusion-randomized to either a screening group or a control group. As first step, a self-administered questionnaire regarding risk factors for osteoporosis based on FRAX......(®) was issued to both groups. As second step, subjects in the screening group with a 10-year probability of major osteoporotic fractures ≥15 % were offered a DXA scan. Patients diagnosed with osteoporosis from the DXA scan were advised to see their GP and discuss pharmaceutical treatment according to Danish...
Short-wave vortex instability in stratified flow
Bovard, Luke
2014-01-01
In this paper we investigate a new instability of the Lamb-Chaplygin dipole in a stratified fluid. Through numerical linear stability analysis, a secondary peak in the growth rate emerges at vertical scales about an order of magnitude smaller than the buoyancy scale $L_{b}=U/N$ where $U$ is the characteristic velocity and $N$ is the Brunt-V\\"{a}is\\"{a}l\\"{a} frequency. This new instability exhibits a growth rate that is similar to, and even exceeds, that of the zigzag instability, which has the characteristic length of the buoyancy scale. This instability is investigated for a wide range of Reynolds $Re=2000-20000$ and horizontal Froude numbers $F_{h}=0.05-0.2$, where $F_{h}=U/NR$, $Re=UR/\
Internal combustion engine using premixed combustion of stratified charges
Marriott, Craig D.; Reitz, Rolf D. (Madison, WI
2003-12-30
During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.
A study of stratified gas-liquid pipe flow
Energy Technology Data Exchange (ETDEWEB)
Johnson, George W.
2005-07-01
This work includes both theoretical modelling and experimental observations which are relevant to the design of gas condensate transport lines. Multicomponent hydrocarbon gas mixtures are transported in pipes over long distances and at various inclinations. Under certain circumstances, the heavier hydrocarbon components and/or water vapour condense to form one or more liquid phases. Near the desired capacity, the liquid condensate and water is efficiently transported in the form of a stratified flow with a droplet field. During operating conditions however, the flow rate may be reduced allowing liquid accumulation which can create serious operational problems due to large amounts of excess liquid being expelled into the receiving facilities during production ramp-up or even in steady production in severe cases. In particular, liquid tends to accumulate in upward inclined sections due to insufficient drag on the liquid from the gas. To optimize the transport of gas condensates, a pipe diameters should be carefully chosen to account for varying flow rates and pressure levels which are determined through the knowledge of the multiphase flow present. It is desirable to have a reliable numerical simulation tool to predict liquid accumulation for various flow rates, pipe diameters and pressure levels which is not presently accounted for by industrial flow codes. A critical feature of the simulation code would include the ability to predict the transition from small liquid accumulation at high flow rates to large liquid accumulation at low flow rates. A semi-intermittent flow regime of roll waves alternating with a partly backward flowing liquid film has been observed experimentally to occur for a range of gas flow rates. Most of the liquid is transported in the roll waves. The roll wave regime is not well understood and requires fundamental modelling and experimental research. The lack of reliable models for this regime leads to inaccurate prediction of the onset of
Direct simulation of the stably stratified turbulent Ekman layer
Coleman, G. N.; Ferziger, J. H.; Spalart, P. R.
1992-01-01
The Navier-Stokes equations and the Boussinesq approximation were used to compute a 3D time-dependent turbulent flow in the stably stratified Ekman layer over a smooth surface. The simulation data are found to be in very good agreement with atmospheric measurements when nondimensionalized according to Nieuwstadt's local scaling scheme. Results suggest that, when Reynolds number effects are taken into account, the 'constant Froud number' stable layer model (Brost and Wyngaard, 1978) and the 'shearing length' stable layer model (Hunt, 1985) for the dissipitation rate of turbulent kinetic energy are both valid. It is concluded that there is good agreement between the direct numerical simulation results and large-eddy simulation results obtained by Mason and Derbyshire (1990).
Second order closure for stratified convection: bulk region and overshooting
Biferale, L; Sbragaglia, M; Scagliarini, A; Toschi, F; Tripiccione, R
2011-01-01
The parameterization of small-scale turbulent fluctuations in convective systems and in the presence of strong stratification is a key issue for many applied problems in oceanography, atmospheric science and planetology. In the presence of stratification, one needs to cope with bulk turbulent fluctuations and with inversion regions, where temperature, density -or both- develop highly non-linear mean profiles due to the interactions between the turbulent boundary layer and the unmixed -stable- flow above/below it. We present a second order closure able to cope simultaneously with both bulk and boundary layer regions, and we test it against high-resolution state-of-the-art 2D numerical simulations in a convective and stratified belt for values of the Rayleigh number, up to Ra = 10^9. Data are taken from a Rayleigh-Taylor system confined by the existence of an adiabatic gradient.
Oxygenation of Stratified Reservoir Using Air Bubble Plume
Schladow, S. G.
2006-12-01
Excess nutrients loading from urban area and watershed into lakes and reservoirs increases the content of organic matter, which, through decomposition, needs increased dissolve oxygen (DO). Many eutrophic reservoirs and lakes cannot meet the DO requirement during stratified season and suffers from the hypolimnetic anoxia. As a result, benthic sediment produces anoxic products such as methane, hydrogen sulphide, ammonia, iron, manganese, and phosphorus. In order to address the hypolimnetic anoxia, oxygen is artificially supplied into reservoir using an aeration system (i.e., bubbler). The most common result of lake/reservoir aeration is to destratify the reservoir so that the water body may completely mix under natural phenomena and remain well oxygenated throughout. Other advantages of destratification are: (1) allows warm- water fish to inhabit the entire reservoir, (2) suppress the nutrient release from sediment, and (3) decreases the algal growth by sending them to the darker zone. A one-dimensional reservoir-bubbler model is developed and applied to examine the effects of an aeration system on mixing and dissolved oxygen dynamics in the Upper Peirce Reservoir, Singapore. After introduction of the aeration system in the reservoir, it was found that the hypolimnetic DO increased significantly, and the concentration of algae, soluble manganese and iron substantially reduced. It is found that the reservoir-bubbler model predicts the mixing (temperature as mixing parameter) and dissolved oxygen concentration in the reservoir with acceptable accuracy. It is shown in terms of bubbler mechanical efficiency (i.e., operating cost) and total DO contribution from the aeration system into the reservoir that the selections of airflow rate per diffuser, air bubble radius, and total number of diffusers are important design criteria of a bubbler system. However, the overall bubbler design also depends on the reservoir size and stratified area of interest, ambient climate, and
Visualization periodic flows in a continuously stratified fluid.
Bardakov, R.; Vasiliev, A.
2012-04-01
To visualize the flow pattern of viscous continuously stratified fluid both experimental and computational methods were developed. Computational procedures were based on exact solutions of set of the fundamental equations. Solutions of the problems of flows producing by periodically oscillating disk (linear and torsion oscillations) were visualized with a high resolutions to distinguish small-scale the singular components on the background of strong internal waves. Numerical algorithm of visualization allows to represent both the scalar and vector fields, such as velocity, density, pressure, vorticity, stream function. The size of the source, buoyancy and oscillation frequency, kinematic viscosity of the medium effects were traced in 2D an 3D posing problems. Precision schlieren instrument was used to visualize the flow pattern produced by linear and torsion oscillations of strip and disk in a continuously stratified fluid. Uniform stratification was created by the continuous displacement method. The buoyancy period ranged from 7.5 to 14 s. In the experiments disks with diameters from 9 to 30 cm and a thickness of 1 mm to 10 mm were used. Different schlieren methods that are conventional vertical slit - Foucault knife, vertical slit - filament (Maksoutov's method) and horizontal slit - horizontal grating (natural "rainbow" schlieren method) help to produce supplementing flow patterns. Both internal wave beams and fine flow components were visualized in vicinity and far from the source. Intensity of high gradient envelopes increased proportionally the amplitude of the source. In domains of envelopes convergence isolated small scale vortices and extended mushroom like jets were formed. Experiments have shown that in the case of torsion oscillations pattern of currents is more complicated than in case of forced linear oscillations. Comparison with known theoretical model shows that nonlinear interactions between the regular and singular flow components must be taken
Flat rotation curves using scalar-tensor theories
Cervantes-Cota, Jorge L.; Rodriguez-Meza, M. A.; Nunez, Dario
2007-01-01
We computed flat rotation curves from scalar-tensor theories in their weak field limit. Our model, by construction, fits a flat rotation profile for velocities of stars. As a result, the form of the scalar field potential and DM distribution in a galaxy are determined. By taking into account the constraints for the fundamental parameters of the theory $(\\lambda, \\alpha)$, it is possible to obtain analytical results for the density profiles. For positive and negative values of $\\alpha$, the DM...
Self-organisation in protoplanetary disks: global, non-stratified Hall-MHD simulations
Béthune, William; Ferreira, Jonathan
2016-01-01
Recent observations revealed organised structures in protoplanetary disks, such as axisymmetric rings or horseshoe concen- trations evocative of large-scale vortices. These structures are often interpreted as the result of planet-disc interactions. However, these disks are also known to be unstable to the magneto-rotational instability (MRI) which is believed to be one of the dominant angular momentum transport mechanism in these objects. It is therefore natural to ask if the MRI itself could produce these structures without invoking planets. The nonlinear evolution of the MRI is strongly affected by the low ionisation fraction in protoplanetary disks. The Hall effect in particular, which is dominant in dense and weakly ionised parts of these objects, has been shown to spontaneously drive self- organising flows in shearing box simulations. Here, we investigate the behaviour of global MRI-unstable disc models dominated by the Hall effect and characterise their dynamics. We perform 3D unstratified Hall-MHD simu...
Relativistic Rotating Vector Model
Lyutikov, Maxim
2016-01-01
The direction of polarization produced by a moving source rotates with the respect to the rest frame. We show that this effect, induced by pulsar rotation, leads to an important correction to polarization swings within the framework of rotating vector model (RVM); this effect has been missed by previous works. We construct relativistic RVM taking into account finite heights of the emission region that lead to aberration, time-of-travel effects and relativistic rotation of polarization. Polarizations swings at different frequencies can be used, within the assumption of the radius-to-frequency mapping, to infer emission radii and geometry of pulsars.
Differential rotation in K, G, F and A stars
Balona, Luis A
2016-01-01
Rotational light modulation in Kepler photometry of K - A stars is used to estimate the absolute rotational shear. The rotation frequency spread in 2562 carefully selected stars with known rotation periods is measured using time-frequency diagrams. The variation of rotational shear as a function of effective temperature in restricted ranges of rotation period is determined. The shear increases to a maximum in F stars, but decreases somewhat in the A stars. Theoretical models reproduce the temperature variation quite well. The dependence of rotation shear on rotation rate in restricted temperature ranges is also determined. The dependence of the shear on the rotation rate is weak in K and G stars, increases rapidly for F stars and is strongest in A stars. For stars earlier than type K, a discrepancy exists between the predicted and observed variation of shear with rotation rate. There is a strong increase in the fraction of stars with zero frequency spread with increasing effective temperature. The time-freque...
Zilitinkevich, S S; Kleeorin, N; Rogachevskii, I; Esau, I
2011-01-01
In this paper we advance physical background of the EFB turbulence closure and present its comprehensive description. It is based on four budget equations for the second moments: turbulent kinetic and potential energies (TKE and TPE) and vertical turbulent fluxes of momentum and buoyancy; a new relaxation equation for the turbulent dissipation time-scale; and advanced concept of the inter-component exchange of TKE. The EFB closure is designed for stratified, rotating geophysical flows from neutral to very stable. In accordance to modern experimental evidence, it grants maintaining turbulence by the velocity shear at any gradient Richardson number Ri, and distinguishes between the two principally different regimes: "strong turbulence" at Ri 1 typical of the free atmosphere or deep ocean, where Pr_T asymptotically linearly increases with increasing Ri that implies strong suppressing of the heat transfer compared to momentum transfer. For use in different applications, the EFB turbulence closure is formulated a...
Katsnelson, Boris; Lunkov, Andrey; Ostrovsky, Ilia
2016-02-01
Internal Kelvin waves (IKWs) initiated by rotation of the Earth are one of the main hydrodynamic phenomena in large stratified lakes where baroclinic Rossby radius of deformation is smaller than the horizontal scale of the lake. IKWs can be identified using the spectra of internal waves, where in the presence of IKWs, the inertial frequency is at maximum. IKWs play a rather important role in the lake's dynamics for different processes, both in the water layer and sediment, especially at the periphery of lake. Due to influence of internal waves on the sound propagation, acoustical methods can be used for estimation of behaviour of IKWs. In this paper, the spatiotemporal variability of the mid-frequency (∼1 kHz) sound field in the presence of IKWs in a deep stratified Lake Kinneret is studied using numerical simulations based on normal-mode theory. Due to the specific character of perturbation of the water layer, IKWs can cause specific variations of interference pattern, in particular, a significant shift of the sound interference pattern both in spatial and frequency domain. These shifts can be easily measured and used for reconstruction of IKW parameters.
Inflationary Weak Anisotropic Model with General Dissipation Coefficient
Sharif, M
2015-01-01
This paper explores the dynamics of warm intermediate and logamediate inflationary models during weak dissipative regime with a general form of dissipative coefficient. We analyze these models within the framework of locally rotationally symmetric Bianchi type I universe. In both cases, we evaluate solution of inflaton, effective scalar potential, dissipative coefficient, slow-roll parameters, scalar and tensor power spectra, scalar spectral index and tensor to scalar ratio under slow-roll approximation. We constrain the model parameters using recent data and conclude that anisotropic inflationary universe model with generalized dissipation coefficient remains compatible with WMAP9, Planck and BICEP2 data.
Directory of Open Access Journals (Sweden)
Joonmo Cho
2015-09-01
Full Text Available The gender gap in working conditions has barely improved in South Korea where various measures for gender equality have been in place for a relatively long time. Furthermore, the female employment rate is also the lowest in OECD (Organization for Economic Cooperation and Development countries. This study will evaluate the stratified structure of the labor market to identify the causes and will analyze changes in the gender employment distribution and mobility. This study conducted an empirical analysis of gender distribution and labor mobility in the South Korean labor market, utilizing long-term data (2005–2014 from the supplementary survey by employment type on the Economically Active Population of the Korea National Statistical Office. From the analysis, women showed a relatively smaller increase than men in the primary labor market, classified as the large and standard employment market, in 2014 compared with 2005, but showed a relatively greater increase than men in the secondary labor market, comprising the small–medium and non-standard employment market. Thus, gender skewness in employment distribution was greater in the stratified labor market. On the other hand, the non-economically active population more than doubled for women compared to men. From the analysis of labor mobility by gender, a higher proportion of women were employed in the peripheral labor market than in the core labor market and women were also more likely to be employed in the relatively weak peripheral labor market. These results imply that dichotomous gender equality policies for resolving the gender gap have a certain limitation in the stratified labor market. Thus, what is needed is a holistic approach that takes into account the labor market structure.
Strengths, weaknesses, opportunities and threats
DEFF Research Database (Denmark)
Bull, J. W.; Jobstvogt, N.; Böhnke-Henrichs, A.;
2016-01-01
environmental awareness. Threats include resistance to change, and difficulty with interdisciplinary collaboration. Consideration of SWOT themes suggested five strategic areas for developing and implementing ES.The ES concept could improve decision-making related to natural resource use, and interpretation...... facilitate interdisciplinary research, ensuring decision-making that supports sustainable development........ Such an assessment could form the basis for improving ES thinking, further embedding it into environmental decisions and management.The Young Ecosystem Services Specialists (YESS) completed a Strengths-Weaknesses-Opportunities-Threats (SWOT) analysis of ES through YESS member surveys. Strengths include the approach...
Weak Precedence Story Parsing Grammar
Institute of Scientific and Technical Information of China (English)
张松懋
1995-01-01
Story understanding is one of the important branches of natural language understanding research in AI techniques.The story understanding approach based on Story Parsing Grammar (SPG) involves that SPG is used to represent different abstracting processes of stories with different levels in story understanding and that the story understanding process is converted to the recognition process of stories using the syntactic parser of SPG.This kind of story understanding is called story parsing.In this paper,firstly a subclass of SPG,called Weak Precedence SPG(WPSPG),is defined.Afterwards the syntactic parsing algorithm of WPSPG is studied.An example of story parsing is also given.
Weakly distributive domains(Ⅱ)
Institute of Scientific and Technical Information of China (English)
JIANG Ying; ZHANG Guo-Qiang
2007-01-01
In our previous work(Inform.and Comput.,2005,202:87-103),we have shown that for any ω-algebraic meet-cpo D,if all higher-order stable function spaces built from D are ω-algebraic,then D is finitary.This accomplishes the first of a possible,two-step process in solving the problem raised(LNCS,1991,530:16-33;Domainsand lambda-calculi,Cambridge Univ.Press,1998)whetherthe category of stable bifinite domains of Amadio-Droste-G(o)bel(LNCS,1991,530:16-33;Theor.Comput.Sci.,1993,111:89-101)is the largest cartesian closed full subcategory within the category of ω-algebraic meet-cpos with stable functions.This paper presents the results of the second step,which is to show that for any ω-algebraic meet-cpo D satisfying axioms M and I to be contained in a cartesian closed full sub-category using ω-algebraic meet-cpos with stable functions,it must not violate M I∞.We introduce a new class of domains called weakly distributive domains and show that for these domains to be in a cartesian closed category using ω-algebraic meet-cpos,property M I must not be violated.Further,we demonstrate that principally distributive domains(those for which each principle ideal is distributive)form a proper subclass of weakly distributive domains,and Birkhoff's M3 and N5(Introduction to Lattices and order,Cambridge Univ.Press,2002)are weakly distributive(but non-distributive).Then,we establish characterization results for weakly distributive domains.We also introduce the notion of meet-generators in constructing stable functions and show that if an ω-algebraic meet-cpo D contains an infinite number of meet-generators,then[D→D]fails I.However,the original problem of Amadio and Curien remains open.
Competition of rotation and stratification in flux concentrations
Losada, I R; Kleeorin, N; Rogachevskii, I
2013-01-01
In a strongly stratified turbulent layer, a uniform horizontal magnetic field can become unstable to spontaneously form local flux concentrations due to a negative contribution of turbulence to the large-scale (mean-field) magnetic pressure. This mechanism, called the negative effective magnetic pressure instability (NEMPI), is of interest in connection with dynamo scenarios where most of the magnetic field resides in the bulk of the convection zone, and not at the bottom. Recent work using the mean-field hydromagnetic equations has shown that NEMPI becomes suppressed at rather low rotation rates with Coriolis numbers as low as 0.1.}{Here we extend these earlier investigations by studying the effects of rotation both on the development of NEMPI and on the effective magnetic pressure. We also quantify the kinetic helicity from direct numerical simulations (DNS) and compare with earlier work.}{To calculate the rotational effect on the effective magnetic pressure we consider both DNS and analytical studies using...
Krieg, Brian J; Taghavi, Seyed Mohammad; Amidon, Gordon L; Amidon, Gregory E
2015-09-01
Bicarbonate is the main buffer in the small intestine and it is well known that buffer properties such as pKa can affect the dissolution rate of ionizable drugs. However, bicarbonate buffer is complicated to work with experimentally. Finding a suitable substitute for bicarbonate buffer may provide a way to perform more physiologically relevant dissolution tests. The dissolution of weak acid and weak base drugs was conducted in bicarbonate and phosphate buffer using rotating disk dissolution methodology. Experimental results were compared with the predicted results using the film model approach of (Mooney K, Mintun M, Himmelstein K, Stella V. 1981. J Pharm Sci 70(1):22-32) based on equilibrium assumptions as well as a model accounting for the slow hydration reaction, CO2 + H2 O → H2 CO3 . Assuming carbonic acid is irreversible in the dehydration direction: CO2 + H2 O ← H2 CO3 , the transport analysis can accurately predict rotating disk dissolution of weak acid and weak base drugs in bicarbonate buffer. The predictions show that matching the dissolution of weak acid and weak base drugs in phosphate and bicarbonate buffer is possible. The phosphate buffer concentration necessary to match physiologically relevant bicarbonate buffer [e.g., 10.5 mM (HCO3 (-) ), pH = 6.5] is typically in the range of 1-25 mM and is very dependent upon drug solubility and pKa .
Deconstructing Mental Rotation
DEFF Research Database (Denmark)
Larsen, Axel
2014-01-01
A random walk model of the classical mental rotation task is explored in two experiments. By assuming that a mental rotation is repeated until sufficient evidence for a match/mismatch is obtained, the model accounts for the approximately linearly increasing reaction times (RTs) on positive trials...... alignment take place during fixations at very high speed....
Philip E. Pope; Jeffery O. Dawson
1989-01-01
Short-rotation plantations offer several advantages over longer, more traditional rotations. They enhance the natural productivity of better sites and of tree species with rapid juvenile growth. Returns on investment are realized in a shorter period and the risk of loss is reduced compared with long term investments. Production of wood and fiber can be maximized by...
Faraday rotation measure synthesis
Brentjens, MA; de Bruyn, AG
2005-01-01
We extend the rotation measure work of Burn ( 1966, MNRAS, 133, 67) to the cases of limited sampling of lambda(2) space and non-constant emission spectra. We introduce the rotation measure transfer function (RMTF), which is an excellent predictor of n pi ambiguity problems with the lambda(2) coverag
Le Vine, David
2016-01-01
Faraday rotation is a change in the polarization as signal propagates through the ionosphere. At L-band it is necessary to correct for this change and measurements are made on the spacecraft of the rotation angle. These figures show that there is good agreement between the SMAP measurements (blue) and predictions based on models (red).
Studying rotational dynamics with a smartphone—accelerometer versus gyroscope
Braskén, Mats; Pörn, Ray
2017-07-01
The wide-spread availability of smartphones makes them a valuable addition to the measurement equipment of both the physics classroom and the instructional physics laboratory, encouraging an active interaction between measurements and modeling activities. Two useful sensors, available in most modern smartphones and tablets, are the 3-axis acceleration sensor and the 3-axis gyroscope. We explore the strengths and weaknesses of each type of sensor and use them to study the rotational dynamics of objects rotating about a fixed axis. Care has to be taken when interpreting acceleration sensor data, and in some cases the gyroscope will allow for rotational measurements not easily replicated using the acceleration sensor.
De Lorenci, V A
1996-01-01
We investigate which mapping we have to use to compare measurements made in a rotating frame to those made in an inertial frame. Using a "Lorentz-like" coordinate transformation we obtain that creation-anihilation operators of a massless scalar field in the rotating frame are not the same as those of an inertial observer. This leads to a new vacuum state (a rotating vacuum) which is a superposition of positive and negative frequency Minkowski particles. After this, introducing an apparatus device coupled linearly with the field we obtain that there is a strong correlation between number of rotating particles (in a given state) obtained via canonical quantization and via response function of the rotating detector. Finally, we analyse polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view.
Uniformly rotating neutron stars
Boshkayev, Kuantay
2016-01-01
In this chapter we review the recent results on the equilibrium configurations of static and uniformly rotating neutron stars within the Hartle formalism. We start from the Einstein-Maxwell-Thomas-Fermi equations formulated and extended by Belvedere et al. (2012, 2014). We demonstrate how to conduct numerical integration of these equations for different central densities ${\\it \\rho}_c$ and angular velocities $\\Omega$ and compute the static $M^{stat}$ and rotating $M^{rot}$ masses, polar $R_p$ and equatorial $R_{\\rm eq}$ radii, eccentricity $\\epsilon$, moment of inertia $I$, angular momentum $J$, as well as the quadrupole moment $Q$ of the rotating configurations. In order to fulfill the stability criteria of rotating neutron stars we take into considerations the Keplerian mass-shedding limit and the axisymmetric secular instability. Furthermore, we construct the novel mass-radius relations, calculate the maximum mass and minimum rotation periods (maximum frequencies) of neutron stars. Eventually, we compare a...
Stratified flows with variable density: mathematical modelling and numerical challenges.
Murillo, Javier; Navas-Montilla, Adrian
2017-04-01
Stratified flows appear in a wide variety of fundamental problems in hydrological and geophysical sciences. They may involve from hyperconcentrated floods carrying sediment causing collapse, landslides and debris flows, to suspended material in turbidity currents where turbulence is a key process. Also, in stratified flows variable horizontal density is present. Depending on the case, density varies according to the volumetric concentration of different components or species that can represent transported or suspended materials or soluble substances. Multilayer approaches based on the shallow water equations provide suitable models but are not free from difficulties when moving to the numerical resolution of the governing equations. Considering the variety of temporal and spatial scales, transfer of mass and energy among layers may strongly differ from one case to another. As a consequence, in order to provide accurate solutions, very high order methods of proved quality are demanded. Under these complex scenarios it is necessary to observe that the numerical solution provides the expected order of accuracy but also converges to the physically based solution, which is not an easy task. To this purpose, this work will focus in the use of Energy balanced augmented solvers, in particular, the Augmented Roe Flux ADER scheme. References: J. Murillo , P. García-Navarro, Wave Riemann description of friction terms in unsteady shallow flows: Application to water and mud/debris floods. J. Comput. Phys. 231 (2012) 1963-2001. J. Murillo B. Latorre, P. García-Navarro. A Riemann solver for unsteady computation of 2D shallow flows with variable density. J. Comput. Phys.231 (2012) 4775-4807. A. Navas-Montilla, J. Murillo, Energy balanced numerical schemes with very high order. The Augmented Roe Flux ADER scheme. Application to the shallow water equations, J. Comput. Phys. 290 (2015) 188-218. A. Navas-Montilla, J. Murillo, Asymptotically and exactly energy balanced augmented flux
Deep silicon maxima in the stratified oligotrophic Mediterranean Sea
Directory of Open Access Journals (Sweden)
Y. Crombet
2011-02-01
Full Text Available The silicon biogeochemical cycle has been studied in the Mediterranean Sea during late summer/early autumn 1999 and summer 2008. The distribution of nutrients, particulate carbon and silicon, fucoxanthin (Fuco, and total chlorophyll-a (TChl-a were investigated along an eastward gradient of oligotrophy during two cruises (PROSOPE and BOUM encompassing the entire Mediterranean Sea during the stratified period. At both seasons, surface waters were depleted in nutrients and the nutriclines gradually deepened towards the East, the phosphacline being the deepest in the easternmost Levantine basin. Following the nutriclines, parallel deep maxima of biogenic silica (DSM, fucoxanthin (DFM and TChl-a (DCM were evidenced during both seasons with maximal concentrations of 0.45 μmol L^{−1} for BSi, 0.26 μg L^{−1} for Fuco, and 1.70 μg L^{−1} for TChl-a, all measured during summer. Contrary to the DCM which was a persistent feature in the Mediterranean Sea, the DSM and DFMs were observed in discrete areas of the Alboran Sea, the Algero-Provencal basin, the Ionian sea and the Levantine basin, indicating that diatoms were able to grow at depth and dominate the DCM under specific conditions. Diatom assemblages were dominated by Chaetoceros spp., Leptocylindrus spp., Pseudonitzschia spp. and the association between large centric diatoms (Hemiaulus hauckii and Rhizosolenia styliformis and the cyanobacterium Richelia intracellularis was observed at nearly all sites. The diatom's ability to grow at depth is commonly observed in other oligotrophic regions and could play a major role in ecosystem productivity and carbon export to depth. Contrary to the common view that Si and siliceous phytoplankton are not major components of the Mediterranean biogeochemistry, we suggest here that diatoms, by persisting at depth during the stratified period, could contribute to a
Weakly circadian cells improve resynchrony.
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Alexis B Webb
Full Text Available The mammalian suprachiasmatic nuclei (SCN contain thousands of neurons capable of generating near 24-h rhythms. When isolated from their network, SCN neurons exhibit a range of oscillatory phenotypes: sustained or damping oscillations, or arrhythmic patterns. The implications of this variability are unknown. Experimentally, we found that cells within SCN explants recover from pharmacologically-induced desynchrony by re-establishing rhythmicity and synchrony in waves, independent of their intrinsic circadian period We therefore hypothesized that a cell's location within the network may also critically determine its resynchronization. To test this, we employed a deterministic, mechanistic model of circadian oscillators where we could independently control cell-intrinsic and network-connectivity parameters. We found that small changes in key parameters produced the full range of oscillatory phenotypes seen in biological cells, including similar distributions of period, amplitude and ability to cycle. The model also predicted that weaker oscillators could adjust their phase more readily than stronger oscillators. Using these model cells we explored potential biological consequences of their number and placement within the network. We found that the population synchronized to a higher degree when weak oscillators were at highly connected nodes within the network. A mathematically independent phase-amplitude model reproduced these findings. Thus, small differences in cell-intrinsic parameters contribute to large changes in the oscillatory ability of a cell, but the location of weak oscillators within the network also critically shapes the degree of synchronization for the population.
Optimal Weak Lensing Skewness Measurements
Zhang, T J; Zhang, P; Dubinski, J; Zhang, Tong-Jie; Pen, Ue-Li; Zhang, Pengjie; Dubinski, John
2003-01-01
Weak lensing measurements are entering a precision era to statistically map the distribution of matter in the universe. The most common measurement has been of the variance of the projected surface density of matter, which corresponds to the induced correlation in alignments of background galaxies. This measurement of the fluctuations is insensitive to the total mass content, like using waves on the ocean to measure its depths. But when the depth is shallow as happens near a beach, waves become skewed. Similarly, a measurement of skewness in the projected matter distribution directly measures the total matter content of the universe. While skewness has already been convincingly detected, its constraint on cosmology is still weak. We address optimal analyses for the CFHT Legacy Survey in the presence of noise. We show that a compensated Gaussian filter with a width of 2.5 arc minutes optimizes the cosmological constraint, yielding $\\Delta \\Omega_m/\\Omega_m\\sim 10%$. This is significantly better than other filt...
Hall, Lawrence J.; Pinner, David; Ruderman, Joshua T.
2014-12-01
The measured values of the weak scale, v, and the first generation masses, m u, d, e , are simultaneously explained in the multiverse, with all these parameters scanning independently. At the same time, several remarkable coincidences are understood. Small variations in these parameters away from their measured values lead to the instability of hydrogen, the instability of heavy nuclei, and either a hydrogen or a helium dominated universe from Big Bang Nucleosynthesis. In the 4d parameter space of ( m u , m d , m e , v), catastrophic boundaries are reached by separately increasing each parameter above its measured value by a factor of (1.4, 1.3, 2.5, ˜ 5), respectively. The fine-tuning problem of the weak scale in the Standard Model is solved: as v is increased beyond the observed value, it is impossible to maintain a significant cosmological hydrogen abundance for any values of m u, d, e that yield both hydrogen and heavy nuclei stability.
Weak Quasielastic Production of Hyperons
Athar, M Sajjad; Alam, M Rafi; Chauhan, S; Singh, S K
2016-01-01
We present the results for antineutrino induced quasielastic hyperon production from nucleon and nuclear targets \\cite{Alam:2014bya,Singh:2006xp}. The inputs are the nucleon-hyperon(N--Y) transition form factors determined from the analysis of neutrino-nucleon scattering and semileptonic decays of neutron and hyperons using SU(3) symmetry. The calculations for the nuclear targets are done in local density approximation. The nuclear medium effects(NME) like Fermi motion, Pauli blocking and final state interaction(FSI) effects due to hyperon-nucleon scattering have been taken into account. The hyperons giving rise to pions through weak decays also contribute to the weak pion production in addition to the $\\Delta$ excitation mechanism which dominates in the energy region of $<$ 0.7 GeV. We also present the results of longitudinal and perpendicular components of polarization of final hyperon \\cite{Akbar:2016awk}. These measurements in the future accelerator experiments with antineutrinos may give some informat...
Weak lensing and cosmological investigation
Acquaviva, V
2005-01-01
In the last few years the scientific community has been dealing with the challenging issue of identifying the dark energy component. We regard weak gravitational lensing as a brand new, and extremely important, tool for cosmological investigation in this field. In fact, the features imprinted on the cosmic microwave background radiation by the lensing from the intervening distribution of matter represent a pretty unbiased estimator, and can thus be used for putting constraints on different dark energy models. This is true in particular for the magnetic-type B-modes of CMB polarization, whose unlensed spectrum at large multipoles (l approximately=1000) is very small even in presence of an amount of gravitational waves as large as currently allowed by the experiments: therefore, on these scales the lensing phenomenon is the only responsible for the observed power, and this signal turns out to be a faithful tracer of the dark energy dynamics. We first recall the formal apparatus of the weak lensing in extended t...
Political corruption and weak state
Directory of Open Access Journals (Sweden)
Stojiljković Zoran
2013-01-01
Full Text Available The author starts from the hypothesis that it is essential for the countries of the region to critically assess the synergy established between systemic, political corruption and a selectively weak, “devious” nature of the state. Moreover, the key dilemma is whether the expanded practice of political rent seeking supports the conclusion that the root of all corruption is in the very existence of the state - particularly in excessive, selective and deforming state interventions and benefits that create a fertile ground for corruption? The author argues that the destructive combination of weak government and rampant political corruption is based on scattered state intervention, while also rule the parties cartel in the executive branch subordinate to parliament, the judiciary and the police. Corrupt exchange takes place with the absence of strong institutional framework and the precise rules of the political and electoral games, control of public finances and effective political and anti-monopoly legislation and practice included. Exit from the current situation can be seen in the realization of effective anticorruption strategy that integrates preventive and repressive measures and activities and lead to the establishment of principles of good governance. [Projekat Ministarstva nauke Republike Srbije, br. 179076: Politički identitet Srbije u regionalnom i globalnom kontekstu
Directory of Open Access Journals (Sweden)
Eliana Henriques de Brito
1990-01-01
Full Text Available In continuing from previous papers, where we studied the existence and uniqueness of the global solution and its asymptotic behavior as time t goes to infinity, we now search for a time-periodic weak solution u(t for the equation whose weak formulation in a Hilbert space H isddt(u′,v+δ(u′,v+αb(u,v+βa(u,v+(G(u,v=(h,vwhere: ′=d/dt; (′ is the inner product in H; b(u,v, a(u,v are given forms on subspaces U⊂W, respectively, of H; δ>0, α≥0, β≥0 are constants and α+β>0; G is the Gateaux derivative of a convex functional J:V⊂H→[0,∞ for V=U, when α>0 and V=W when α=0, hence β>0; v is a test function in V; h is a given function of t with values in H.
Sadhukhan, Shubhadeep; Chakraborty, Sagar
2016-01-01
We have performed systemmatic local linear stability analysis on a radially stratified infinite self-gravitating cylinder of rotating plasma under the influence of magnetic field. In order to render the system analytically tractable, we have focussed solely on the axisymmetric modes of perturbations. Using cylindrical coordinate system, we have derived the critical linear mass density of a non-rotating filament required for gravitational collapse to ensue in the presence of azimuthal magnetic field. Moreover, for such filaments threaded by axial magnetic field, we show that the growth rates of the modes having non-zero radial wavenumber are reduced more strongly by the magnetic field than that of the modes having zero radial wavenumber. More importantly, our study contributes to the understanding of the stability property of rotating astrophysical filaments that are more often than not influenced by magnetic fields. In addition to complementing many relevant numerical studies reported the literature, our resu...
Free Oscillations of a Rotating Ideal Stratified Liquisds%旋转层状液的自由震动
Institute of Scientific and Technical Information of China (English)
Yu.N.Kononov; 陈孟诗
2001-01-01
考虑两种互不混合的理想不可压缩液体部分或全部充满刚体中在惯性力场中转动时的自由震动,在系统不受扰动时,其运动就象一个刚体,将其考虑成部分或完全充盈的刚体在惯性力场中的转动.确定层状液震动频谱就可归结为求解边界的特征值问题,这可以用解析的方法或数值的方法来求解.导出了在柱状空腔中快速旋转的两种互不混合的层状液边值问题的解析解.给出的不同半径处分层在不同充盈深度震动频率计算结果表明:液体质量一定时分层液自震频率高于均质液;分层对某一平均半径内表面固有频率有决定性影响,其它地方可以忽略不计.
Rotations of small, inertialess triaxial ellipsoids in isotropic turbulence
Pujara, Nimish
2016-01-01
The statistics of rotational motion of small, inertialess triaxial ellipsoids are computed along Lagrangian trajectories extracted from direct numerical simulations of homogeneous isotropic turbulence. The particle angular velocity and its components along the three principal axes of the particle are considered, expanding on the results presented by \\citet{ChevillardMeneveau13}. The variance of the particle angular velocity, referred to as the particle enstrophy, is found to increase for particles with elongated shapes. This trend is explained by considering the contributions of vorticity and strain-rate to particle rotation. It is found that the majority of particle enstrophy is due to fluid vorticity. Strain-rate-induced rotations, which are sensitive to shape, are mostly cancelled by strain-vorticity interactions. The remainder of the strain-rate-induced rotations are responsible for weak variations in particle enstrophy. For particles of all shapes, the majority of the enstrophy is in rotations about the ...
Synchronization of magnetic dipole rotation in an ac magnetic field
Energy Technology Data Exchange (ETDEWEB)
Belovs, M; Cebers, A, E-mail: aceb@tesla.sal.lv [University of Latvia, Zellu-8, Riga, LV-1002 (Latvia)
2011-07-22
The synchronization of the rotation of magnetic dipoles due to weak dipolar interactions is studied. The set of equations is analyzed by the time averaging technique. It is found that dipoles synchronously oscillate at low applied fields and rotate synchronously at large applied fields. The mean angular velocity of synchronous rotation increases with the field strength and reaches a constant value equal to the angular frequency of the field above the critical value of the field strength. The critical value of the field strength above which the synchronous rotation takes place can be calculated from dimensionless parameters using a model derived from first principles by others. The values thus obtained are in good agreement with the values we obtain from a numerical simulation. Thus, we may conclude that the liquid flow observed in these systems may be caused by synchronized rotations of the dipoles.
Searching for Faraday rotation in cosmic microwave background polarization
Ruiz-Granados, B.; Battaner, E.; Florido, E.
2016-08-01
We use the Wilkinson Microwave Anisotropy Probe (WMAP) 9th-year foreground reduced data at 33, 41 and 61 GHz to derive a Faraday rotation at map and at angular power spectrum levels taking into account their observational errors. A processing mask provided by WMAP is used to avoid contamination from the disc of our Galaxy and local spurs. We have found a Faraday rotation component at both, map and power spectrum levels. The lack of correlation of the Faraday rotation with Galactic Faraday rotation, synchrotron and dust polarization from our Galaxy or with cosmic microwave background anisotropies or lensing suggests that it could be originated at reionization (ℓ ≲ 12). Even if the detected Faraday rotation signal is weak, the present study could contribute to establish magnetic fields strengths of B0 ˜ 10-8 G at reionization.
Turbulence comes in bursts in stably stratified flows
Rorai, C; Pouquet, A
2013-01-01
There is a clear distinction between simple laminar and complex turbulent fluids. But in some cases, as for the nocturnal planetary boundary layer, a stable and well-ordered flow can develop intense and sporadic bursts of turbulent activity which disappear slowly in time. This phenomenon is ill-understood and poorly modeled; and yet, it is central to our understanding of weather and climate dynamics. We present here a simple model which shows that in stably stratified turbulence, the stronger bursts can occur when the flow is expected to be more stable. The bursts are generated by a rapid non-linear amplification of energy stored in waves, and are associated with energetic interchanges between vertical velocity and temperature (or density) fluctuations. Direct numerical simulations on grids of 2048^3 points confirm this somewhat paradoxical result of measurably stronger events for more stable flows, displayed not only in the temperature and vertical velocity derivatives, but also in the amplitude of the field...
DNS of stratified spatially-developing turbulent thermal boundary layers
Araya, Guillermo; Castillo, Luciano; Jansen, Kenneth
2012-11-01
Direct numerical simulations (DNS) of spatially-developing turbulent thermal boundary layers under stratification are performed. It is well known that the transport phenomena of the flow is significantly affected by buoyancy, particularly in urban environments where stable and unstable atmospheric boundary layers are encountered. In the present investigation, the Dynamic Multi-scale approach by Araya et al. (JFM, 670, 2011) for turbulent inflow generation is extended to thermally stratified boundary layers. Furthermore, the proposed Dynamic Multi-scale approach is based on the original rescaling-recycling method by Lund et al. (1998). The two major improvements are: (i) the utilization of two different scaling laws in the inner and outer parts of the boundary layer to better absorb external conditions such as inlet Reynolds numbers, streamwise pressure gradients, buoyancy effects, etc., (ii) the implementation of a Dynamic approach to compute scaling parameters from the flow solution without the need of empirical correlations as in Lund et al. (1998). Numerical results are shown for ZPG flows at high momentum thickness Reynolds numbers (~ 3,000) and a comparison with experimental data is also carried out.
Stratified patterns of divorce: Earnings, education, and gender
Directory of Open Access Journals (Sweden)
Amit Kaplan
2015-05-01
Full Text Available Background: Despite evidence that divorce has become more prevalent among weaker socioeconomic groups, knowledge about the stratification aspects of divorce in Israel is lacking. Moreover, although scholarly debate recognizes the importance of stratificational positions with respect to divorce, less attention has been given to the interactions between them. Objective: Our aim is to examine the relationship between social inequality and divorce, focusing on how household income, education, employment stability, relative earnings, and the intersection between them affect the risk of divorce in Israel. Methods: The data is derived from combined census files for 1995-2008, annual administrative employment records from the National Insurance Institute and the Tax Authority, and data from the Civil Registry of Divorce. We used a series of discrete-time event-history analysis models for marital dissolution. Results: Couples in lower socioeconomic positions had a higher risk of divorce in Israel. Higher education in general, and homogamy in terms of higher education (both spouses have degrees in particular, decreased the risk of divorce. The wife's relative earnings had a differential effect on the likelihood of divorce, depending on household income: a wife who outearned her husband increased the log odds of divorce more in the upper tertiles than in the lower tertile. Conclusions: Our study shows that divorce indeed has a stratified pattern and that weaker socioeconomic groups experience the highest levels of divorce. Gender inequality within couples intersects with the household's economic and educational resources.
Self-Knowledge and Risk in Stratified Medicine.
Hordern, Joshua
2017-04-01
This article considers why and how self-knowledge is important to communication about risk and behaviour change by arguing for four claims. First, it is doubtful that genetic knowledge should properly be called 'self-knowledge' when its ordinary effects on self-motivation and behaviour change seem so slight. Second, temptations towards a reductionist, fatalist, construal of persons' futures through a 'molecular optic' should be resisted. Third, any plausible effort to change people's behaviour must engage with cultural self-knowledge, values and beliefs, catalysed by the communication of genetic risk. For example, while a Judaeo-Christian notion of self-knowledge is distinctively theological, people's self-knowledge is plural in its insight and sources. Fourth, self-knowledge is found in compassionate, if tense, communion which yields freedom from determinism even amidst suffering. Stratified medicine thus offers a newly precise kind of humanising health care through societal solidarity with the riskiest. However, stratification may also mean that molecularly unstratified, 'B' patients' experience involves accentuated suffering and disappointment, a concern requiring further research.
[Phylogenetic diversity of bacteria in soda lake stratified sediments].
Tourova, T P; Grechnikova, M A; Kuznetsov, V V; Sorokin, D Yu
2014-01-01
Various previously developed techniques for DNA extraction from the samples with complex physicochemical structure (soils, silts, and sediments) and modifications of these techniques developed in the present work were tested. Their usability for DNA extraction from the sediments of the Kulunda Steppe hypersaline soda lakes was assessed, and the most efficient procedure for indirect (two-stage) DNA extraction was proposed. Almost complete separation of the cell fraction was shown, as well as the inefficiency of nested PCR for analysis of the clone libraries obtained from washed sediments by amplification of the 16S rRNA gene fragments. Analysis of the clone library obtained from the cell fractions of stratified sediments (upper, medium, and lower layers) revealed that in the sediments of Lake Gorchina-3 most eubacterial phylotypes belonged to the class Clostridia, phylum Firmicutes. They were probably specific for this habitatand formed a new, presently unknown high-rank taxon. The data obtained revealed no pronounced stratification of the spe- cies diversity of the eubacterial component of the microbial community inhabiting the sediments (0-20 cm) in the inshore zone of Lake Gorchina-3.
Stratified Flow Past a Hill: Dividing Streamline Concept Revisited
Leo, Laura S.; Thompson, Michael Y.; Di Sabatino, Silvana; Fernando, Harindra J. S.
2016-06-01
The Sheppard formula (Q J R Meteorol Soc 82:528-529, 1956) for the dividing streamline height H_s assumes a uniform velocity U_∞ and a constant buoyancy frequency N for the approach flow towards a mountain of height h, and takes the form H_s/h=( {1-F} ) , where F=U_{∞}/Nh. We extend this solution to a logarithmic approach-velocity profile with constant N. An analytical solution is obtained for H_s/h in terms of Lambert-W functions, which also suggests alternative scaling for H_s/h. A `modified' logarithmic velocity profile is proposed for stably stratified atmospheric boundary-layer flows. A field experiment designed to observe H_s is described, which utilized instrumentation from the spring field campaign of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program. Multiple releases of smoke at F≈ 0.3-0.4 support the new formulation, notwithstanding the limited success of experiments due to logistical constraints. No dividing streamline is discerned for F≈ 10, since, if present, it is too close to the foothill. Flow separation and vortex shedding is observed in this case. The proposed modified logarithmic profile is in reasonable agreement with experimental observations.
Large eddy simulation of unsteady lean stratified premixed combustion
Energy Technology Data Exchange (ETDEWEB)
Duwig, C. [Division of Fluid Mechanics, Department of Energy Sciences, Lund University, SE 221 00 Lund (Sweden); Fureby, C. [Division of Weapons and Protection, Warheads and Propulsion, The Swedish Defense Research Agency, FOI, SE 147 25 Tumba (Sweden)
2007-10-15
Premixed turbulent flame-based technologies are rapidly growing in importance, with applications to modern clean combustion devices for both power generation and aeropropulsion. However, the gain in decreasing harmful emissions might be canceled by rising combustion instabilities. Unwanted unsteady flame phenomena that might even destroy the whole device have been widely reported and are subject to intensive studies. In the present paper, we use unsteady numerical tools for simulating an unsteady and well-documented flame. Computations were performed for nonreacting, perfectly premixed and stratified premixed cases using two different numerical codes and different large-eddy-simulation-based flamelet models. Nonreacting simulations are shown to agree well with experimental data, with the LES results capturing the mean features (symmetry breaking) as well as the fluctuation level of the turbulent flow. For reacting cases, the uncertainty induced by the time-averaging technique limited the comparisons. Given an estimate of the uncertainty, the numerical results were found to reproduce well the experimental data in terms both of mean flow field and of fluctuation levels. In addition, it was found that despite relying on different assumptions/simplifications, both numerical tools lead to similar predictions, giving confidence in the results. Moreover, we studied the flame dynamics and particularly the response to a periodic pulsation. We found that above a certain excitation level, the flame dynamic changes and becomes rather insensitive to the excitation/instability amplitude. Conclusions regarding the self-growth of thermoacoustic waves were drawn. (author)
Economic evaluation in stratified medicine: methodological issues and challenges
Directory of Open Access Journals (Sweden)
Hans-Joerg eFugel
2016-05-01
Full Text Available Background: Stratified Medicine (SM is becoming a practical reality with the targeting of medicines by using a biomarker or genetic-based diagnostic to identify the eligible patient sub-population. Like any healthcare intervention, SM interventions have costs and consequences that must be considered by reimbursement authorities with limited resources. Methodological standards and guidelines exist for economic evaluations in clinical pharmacology and are an important component for health technology assessments (HTAs in many countries. However, these guidelines have initially been developed for traditional pharmaceuticals and not for complex interventions with multiple components. This raises the issue as to whether these guidelines are adequate to SM interventions or whether new specific guidance and methodology is needed to avoid inconsistencies and contradictory findings when assessing economic value in SM.Objective: This article describes specific methodological challenges when conducting health economic (HE evaluations for SM interventions and outlines potential modifications necessary to existing evaluation guidelines /principles that would promote consistent economic evaluations for SM.Results/Conclusions: Specific methodological aspects for SM comprise considerations on the choice of comparator, measuring effectiveness and outcomes, appropriate modelling structure and the scope of sensitivity analyses. Although current HE methodology can be applied for SM, greater complexity requires further methodology development and modifications in the guidelines.
BIPOLAR MAGNETIC SPOTS FROM DYNAMOS IN STRATIFIED SPHERICAL SHELL TURBULENCE
Energy Technology Data Exchange (ETDEWEB)
Jabbari, Sarah; Brandenburg, Axel; Kleeorin, Nathan; Mitra, Dhrubaditya; Rogachevskii, Igor, E-mail: sarahjab@kth.se [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)
2015-06-01
Recent work by Mitra et al. (2014) has shown that in strongly stratified forced two-layer turbulence with helicity and corresponding large-scale dynamo action in the lower layer, and nonhelical turbulence in the upper, a magnetic field occurs in the upper layer in the form of sharply bounded bipolar magnetic spots. Here we extend this model to spherical wedge geometry covering the northern hemisphere up to 75° latitude and an azimuthal extent of 180°. The kinetic helicity and therefore also the large-scale magnetic field are strongest at low latitudes. For moderately strong stratification, several bipolar spots form that eventually fill the full longitudinal extent. At early times, the polarity of spots reflects the orientation of the underlying azimuthal field, as expected from Parker’s Ω-shaped flux loops. At late times their tilt changes such that there is a radial field of opposite orientation at different latitudes separated by about 10°. Our model demonstrates the spontaneous formation of spots of sizes much larger than the pressure scale height. Their tendency to produce filling factors close to unity is argued to be reminiscent of highly active stars. We confirm that strong stratification and strong scale separation are essential ingredients behind magnetic spot formation, which appears to be associated with downflows at larger depths.
Local properties of countercurrent stratified steam-water flow
Energy Technology Data Exchange (ETDEWEB)
Kim, H J
1985-10-01
A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel/flat plate geometry over a wide range of inclination angles (4/sup 0/-87/sup 0/) at several aspect ratios. Variables were inlet water and steam flow rates, and inlet water temperature. Local condensation rates and pressure gradients were measured, and local condensation heat transfer coefficients and interfacial shear stress were calculated. Contact probe traverses of the surface waves were made, which allowed a statistical analysis of the wave properties. The local condensation Nusselt number was correlated in terms of local water and steam Reynolds or Froude numbers, as well as the liquid Prandtl number. A turbulence-centered model developed by Theofanous, et al. principally for gas absorption in several geometries, was modified. A correlation for the interfacial shear stress and the pressure gradient agreed with measured values. Mean water layer thicknesses were calculated. Interfacial wave parameters, such as the mean water layer thickness, liquid fraction probability distribution, wave amplitude and wave frequency, are analyzed.
Numerical Study of Stratified Charge Combustion in Wave Rotors
Nalim, M. Razi
1997-01-01
A wave rotor may be used as a pressure-gain combustor effecting non-steady flow, and intermittent, confined combustion to enhance gas turbine engine performance. It will be more compact and probably lighter than an equivalent pressure-exchange wave rotor, yet will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel/air ratio to sub-flammable values, premixed stratification techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperature well below autoignition conditions. One-dimensional, unsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a flammability limit temperature. For good combustion efficiency, a stratification strategy is developed which concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature profiles and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak local gas temperatures will result in excessive temperatures within the rotor housing unless additional cooling methods are used. The rotor itself will have acceptable temperatures, but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct-rotor interaction.
Stratifying the Risk of Venous Thromboembolism in Otolaryngology
Shuman, Andrew G.; Hu, Hsou Mei; Pannucci, Christopher J.; Jackson, Christopher R.; Bradford, Carol R.; Bahl, Vinita
2015-01-01
Objective The consequences of perioperative venous thromboembolism (VTE) are devastating; identifying patients at risk is an essential step in reducing morbidity and mortality. The utility of perioperative VTE risk assessment in otolaryngology is unknown. This study was designed to risk-stratify a diverse population of otolaryngology patients for VTE events. Study Design Retrospective cohort study. Setting Single-institution academic tertiary care medical center. Subjects and Methods Adult patients presenting for otolaryngologic surgery requiring hospital admission from 2003 to 2010 who did not receive VTE chemoprophylaxis were included. The Caprini risk assessment was retrospectively scored via a validated method of electronic chart abstraction. Primary study variables were Caprini risk scores and the incidence of perioperative venous thromboembolic outcomes. Results A total of 2016 patients were identified. The overall 30-day rate of VTE was 1.3%. The incidence of VTE in patients with a Caprini risk score of 6 or less was 0.5%. For patients with scores of 7 or 8, the incidence was 2.4%. Patients with a Caprini risk score greater than 8 had an 18.3% incidence of VTE and were significantly more likely to develop a VTE when compared to patients with a Caprini risk score less than 8 (P otolaryngology patients for 30-day VTE events and allows otolaryngologists to identify patient subgroups who have a higher risk of VTE in the absence of chemoprophylaxis. PMID:22261490
Mixing efficiency of turbulent patches in stably stratified flows
Garanaik, Amrapalli; Venayagamoorthy, Subhas Karan
2016-11-01
A key quantity that is essential for estimating the turbulent diapycnal (irreversible) mixing in stably stratified flow is the mixing efficiency Rf*, which is a measure of the amount of turbulent kinetic energy that is irreversibly converted into background potential energy. In particular, there is an ongoing debate in the oceanographic mixing community regarding the utility of the buoyancy Reynolds number (Reb) , particularly with regard to how mixing efficiency and diapycnal diffusivity vary with Reb . Specifically, is there a universal relationship between the intensity of turbulence and the strength of the stratification that supports an unambiguous description of mixing efficiency based on Reb ? The focus of the present study is to investigate the variability of Rf* by considering oceanic turbulence data obtained from microstructure profiles in conjunction with data from laboratory experiments and DNS. Field data analysis has done by identifying turbulent patches using Thorpe sorting method for potential density. The analysis clearly shows that high mixing efficiencies can persist at high buoyancy Reynolds numbers. This is contradiction to previous studies which predict that mixing efficiency should decrease universally for Reb greater than O (100) . Funded by NSF and ONR.
Simulation and study of stratified flows around finite bodies
Gushchin, V. A.; Matyushin, P. V.
2016-06-01
The flows past a sphere and a square cylinder of diameter d moving horizontally at the velocity U in a linearly density-stratified viscous incompressible fluid are studied. The flows are described by the Navier-Stokes equations in the Boussinesq approximation. Variations in the spatial vortex structure of the flows are analyzed in detail in a wide range of dimensionless parameters (such as the Reynolds number Re = Ud/ ν and the internal Froude number Fr = U/( Nd), where ν is the kinematic viscosity and N is the buoyancy frequency) by applying mathematical simulation (on supercomputers of Joint Supercomputer Center of the Russian Academy of Sciences) and three-dimensional flow visualization. At 0.005 < Fr < 100, the classification of flow regimes for the sphere (for 1 < Re < 500) and for the cylinder (for 1 < Re < 200) is improved. At Fr = 0 (i.e., at U = 0), the problem of diffusion-induced flow past a sphere leading to the formation of horizontal density layers near the sphere's upper and lower poles is considered. At Fr = 0.1 and Re = 50, the formation of a steady flow past a square cylinder with wavy hanging density layers in the wake is studied in detail.
Transfer matrix for treating stratified media including birefringent crystals.
Essinger-Hileman, Thomas
2013-01-10
Birefringent crystals are extensively used to manipulate polarized light. The generalized transfer matrix developed allows efficient calculation of the full polarization state of light transmitted through and reflected by a stack of arbitrarily many discrete layers of isotropic and birefringent materials at any frequency and angle of incidence. The matrix of a uniaxial birefringent crystal with arbitrary rotation is calculated, along with its reduction to the matrix of an isotropic medium. This method is of great practical importance where tight control of systematic effects is needed in optical systems employing birefringent crystals, one example being wave plates used by cosmic microwave background polarimetry with wide field-of-view telescopes.
Transfer matrix for treating stratified media including birefringent crystals
Essinger-Hileman, Thomas
2013-01-01
Birefringent crystals are extensively used to manipulate polarized light. The generalized transfer matrix developed allows efficient calculation of the full polarization state of light transmitted through and reflected by a stack of arbitrarily-many discrete layers of isotropic and birefringent materials at any frequency and angle of incidence. The matrix of a uniaxial birefringent crystal with arbitrary rotation is calculated, along with its reduction to the matrix of an isotropic medium. This method is of great practical importance where tight control of systematic effects is needed in optical systems employing birefringent crystals, one example being wave plates used by cosmic microwave background polarimetry with wide field-of-view telescopes.
The effect of rotation on oscillatory double-diffusive convection (semiconvection)
Moll, Ryan
2016-01-01
Oscillatory double-diffusive convection (ODDC, more traditionally called semiconvection) is a form of linear double-diffusive instability that occurs in fluids that are unstably stratified in temperature (Schwarzschild unstable), but stably stratified in chemical composition (Ledoux stable). This scenario is thought to be quite common in the interiors of stars and giant planets, and understanding the transport of heat and chemical species by ODDC is of great importance to stellar and planetary evolution models. Fluids unstable to ODDC have a tendency to form convective thermo-compositional layers which significantly enhance the fluxes of temperature and chemical composition compared with microscopic diffusion. Although a number of recent studies have focused on studying properties of both layered and non-layered ODDC, few have addressed how additional physical processes such as global rotation affect its dynamics. In this work we study first how rotation affects the linear stability properties of rotating ODD...
Local Weak Ferromagnetism in Single-Crystalline Ferroelectric BiFeO3
DEFF Research Database (Denmark)
Ramazanoglu, M.; Laver, Mark; Ratcliff, W.;
2011-01-01
Polarized small-angle neutron scattering studies of single-crystalline multiferroic BiFeO3 reveal a long-wavelength spin density wave generated by ∼1° spin canting of the spins out of the rotation plane of the antiferromagnetic cycloidal order. This signifies weak ferromagnetism within mesoscopic...
DISSOLUTION KINETICS OF KETANSERIN TARTRATE, THE SALT OF A WEAKLY BASIC DRUG
VANDERVEEN, J; BUITENDIJK, HH; LERK, CF
1992-01-01
The rotating disc method was used to study the dissolution kinetics of ketanserin tartrate, the salt of a weakly basic drug. Both solubility and dissolution rate decrease exponentially with increasing pH of the dissolution medium. A plot of the logarithm of the ratio of dissolution rate to solubilit
Casimir torque in weak coupling
Milton, Kimball A; Long, William
2013-01-01
In this paper, dedicated to Johan H{\\o}ye on the occasion of his 70th birthday, we examine manifestations of Casimir torque in the weak-coupling approximation, which allows exact calculations so that comparison with the universally applicable, but generally uncontrolled, proximity force approximation may be made. In particular, we examine Casimir energies between planar objects characterized by $\\delta$-function potentials, and consider the torque that arises when angles between the objects are changed. The results agree very well with the proximity force approximation when the separation distance between the objects is small compared with their sizes. In the opposite limit, where the size of one object is comparable to the separation distance, the shape dependence starts becoming irrelevant. These calculations are illustrative of what to expect for the torques between, for example, conducting planar objects, which eventually should be amenable to both improved theoretical calculation and experimental verific...
Institute of Scientific and Technical Information of China (English)
WANG Baocang; LIU Shuanggen; HU Yupu
2006-01-01
The security of the RSA system with the prime pairs of some special form is investigated. A new special-purpose algorithm for factoring RSA numbers is proposed. The basic idea of the method is to factor RSA numbers by factoring a well-chosen quadratic polynomial with integral coefficients. When viewed as a general-purpose algorithm, the new algorithm has a high computational complexity. It is shown that the RSA number n=pq can be easily factored if p and q have the special form of p=as+b, q=cs+d, where a, b, c, d are relatively small numbers. Such prime pairs (p, q) are the weak keys of RSA, so when we generate RSA modulus, we should avoid using such prime pairs (p, q).
Binzel, R. P.; Green, J. R.; Opal, C. B.
1986-01-01
Thomas et al. (1984) analyzed 14 Voyager 2 images of Saturn's satellite Hyperion and interpreted them to be consistent with a coherent (nonchaotic) rotation period of 13.1 days. This interpretation was criticized by Peale and Wisdom (1984), who argued that the low sampling frequency of Voyager data does not allow chaotic or nonchaotic rotation to be distinguished. New observations obtained with a higher sampling frequency are reported here which conclusively show that the 13.1 day period found by Thomas et al. was not due to coherent rotation.
Energy Technology Data Exchange (ETDEWEB)
Lorenci, V.A. de; Svaiter, N.F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)
1996-11-01
It was investigated which mapping has to be used to compare measurements made in a rotating frame to those made in an inertial frame. Using a non-Galilean coordinate transformation, the creation-annihilation operators of a massive scalar field in the rotating frame are not the same as those of an inertial observer. This leads to a new vacuum state(a rotating vacuum) which is a superposition of positive and negative frequency Minkowski particles. Polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view were analysed. 65 refs.
Directory of Open Access Journals (Sweden)
Jerzy Czerski
2014-02-01
Full Text Available The germination of whole seeds, the seeds without coat and isolated embryos of apple cv. "Antonówka Zwykła" after 90 days of cold-stratification was compared with the germination of embryos isolated from non-stratified seeds. They were germinated under 16hrs during a day at temperature 25°C and 20°C during the night. It has been found that after 2 weeks whole stratified seeds germinated in 5 per cent, seeds without coat in 25 per cent and isolated embryos in 98 per cent. Isolated embryos from nun-stratified seeds, after 2 weeks, germinated in the range from 75 to 88 per cent. The results indicate the similar germination ability of embryos isolated from nun-stratified seeds. The seedling populations obtained from embryo's stratified and non-stratified seeds were fully comparable and they evaluated: 1 a wide range of individual differences within population, 2 a similar number of seedlings in each class of shoot length, 3 a similar morphological habitus in each class of shoot length, 4 a similar fresh leaf weight and whole plant increment.
Evaluation and Revision of an Introduction to Experiential Rotations Course
Dy, Eliza A.; Nisly, Sarah A.
2014-01-01
The objectives of this study were to evaluate the perceived student value of topics taught in Butler University's Introduction to Experiential Rotations (RX500) course, implement course revisions to address any perceived weaknesses, and to reassess the course following implementation of those course revisions. Advanced Pharmacy Practice Experience…
Mahanta, J.; P. K. Das
2012-01-01
A new class of fuzzy closed sets, namely fuzzy weakly closed set in a fuzzy topological space is introduced and it is established that this class of fuzzy closed sets lies between fuzzy closed sets and fuzzy generalized closed sets. Alongwith the study of fundamental results of such closed sets, we define and characterize fuzzy weakly compact space and fuzzy weakly closed space.
Twisting theory for weak Hopf algebras
Institute of Scientific and Technical Information of China (English)
CHEN Ju-zhen; ZHANG Yan; WANG Shuan-hong
2008-01-01
The main aim of this paper is to study the twisting theory of weak Hopf algebras and give an equivalence between the (braided) monoidal categories of weak Hopf bimodules over the original and the twisted weak Hopf algebra to generalize the result from Oeckl (2000).
Reconstruction of weak quasi-Hopf algebras
Häring, Reto Andreas
1995-01-01
All rational semisimple braided tensor categories are representation categories of weak quasi Hopf algebras. To proof this result we construct for any given category of this kind a weak quasi tensor functor to the category of finite dimensional vector spaces. This allows to reconstruct a weak quasi Hopf algebra with the given category as its representation category.
ANALYTICAL CALCULATION OF STOKES PROFILES OF ROTATING STELLAR MAGNETIC DIPOLE
Energy Technology Data Exchange (ETDEWEB)
Martinez Gonzalez, M. J. [Instituto de Astrofisica de Canarias, Via Lactea s/n, 38200 La Laguna, Tenerife (Spain); Asensio Ramos, A. [Departamento de Astrofisica, Universidad de La Laguna, E-38205 La Laguna, Tenerife (Spain)
2012-08-20
The observation of the polarization emerging from a rotating star at different phases opens up the possibility to map the magnetic field in the stellar surface thanks to the well-known Zeeman-Doppler imaging. When the magnetic field is sufficiently weak, the circular and linear polarization profiles locally in each point of the star are proportional to the first and second derivatives of the unperturbed intensity profile, respectively. We show that the weak-field approximation (for weak lines in the case of linear polarization) can be generalized to the case of a rotating star including the Doppler effect and taking into account the integration on the stellar surface. The Stokes profiles are written as a linear combination of wavelength-dependent terms expressed as series expansions in terms of Hermite polynomials. These terms contain the surface-integrated magnetic field and velocity components. The direct numerical evaluation of these quantities is limited to rotation velocities not larger than eight times the Doppler width of the local absorption profiles. Additionally, we demonstrate that in a rotating star, the circular polarization flux depends on the derivative of the intensity flux with respect to the wavelength and also on the profile itself. Likewise, the linear polarization depends on the profile and on its first and second derivatives with respect to the wavelength. We particularize the general expressions to a rotating dipole.
STUDIES OF TWO-PHASE PLUMES IN STRATIFIED ENVIRONMENTS
Energy Technology Data Exchange (ETDEWEB)
Scott A. Socolofsky; Brian C. Crounse; E. Eric Adams
1998-11-18
Two-phase plumes play an important role in the more practical scenarios for ocean sequestration of CO{sub 2}--i.e. dispersing CO{sub 2} as a buoyant liquid from either a bottom-mounted or ship-towed pipeline. Despite much research on related applications, such as for reservoir destratification using bubble plumes, our understanding of these flows is incomplete, especially concerning the phenomenon of plume peeling in a stratified ambient. To address this deficiency, we have built a laboratory facility in which we can make fundamental measurements of plume behavior. Although we are using air, oil and sediments as our sources of buoyancy (rather than CO{sub 2}), by using models, our results can be directly applied to field scale CO{sub 2} releases to help us design better CO{sub 2} injection systems, as well as plan and interpret the results of our up-coming international field experiment. The experimental facility designed to study two-phase plume behavior similar to that of an ocean CO{sub 2} release includes the following components: 1.22 x 1.22 x 2.44 m tall glass walled tank; Tanks and piping for the two-tank stratification method for producing step- and linearly-stratified ambient conditions; Density profiling system using a conductivity and temperature probe mounted to an automated depth profiler; Lighting systems, including a virtual point source light for shadowgraphs and a 6 W argon-ion laser for laser induced fluorescence (LIF) imaging; Imaging system, including a digital, progressive scanning CCD camera, computerized framegrabber, and image acquisition and analysis software; Buoyancy source diffusers having four different air diffusers, two oil diffusers, and a planned sediment diffuser; Dye injection method using a Mariotte bottle and a collar diffuser; and Systems integration software using the Labview graphical programming language and Windows NT. In comparison with previously reported experiments, this system allows us to extend the parameter range of
... cuff are common. They include tendinitis, bursitis, and injuries such as tears. Rotator cuff tendons can become ... cuff depends on age, health, how severe the injury is, and how long you've had the ...
Fractal Aggregation Under Rotation
Institute of Scientific and Technical Information of China (English)
WU Feng-Min; WU Li-Li; LU Hang-Jun; LI Qiao-Wen; YE Gao-Xiang
2004-01-01
By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω the fractal dimension decreases with increasing ω, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.
Fractal Aggregation Under Rotation
Institute of Scientific and Technical Information of China (English)
WUFeng-Min; WULi-Li; LUHang-Jun; LIQiao-Wen; YEGao-Xiang
2004-01-01
By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω; thefractal dimension decreases with increasing ω;, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.
Solar rotation gravitational moments
Directory of Open Access Journals (Sweden)
A. Ajabshirizadeh
2005-09-01
Full Text Available Gravitational multipole moments of the Sun are still poorly known. Theoretically, the difficulty is mainly due to the differential rotation for which the velocity rate varies both on the surface and with the depth. From an observational point of view, the multipole moments cannot be directly measured. However, recent progresses have been made proving the existence of a strong radial differential rotation in a thin layer near the solar surface (the leptocline. Applying the theory of rotating stars, we will first compute values of J2 and J4 taking into account the radial gradient of rotation, then we will compare these values with the existing ones, giving a more complete review. We will explain some astrophysical outcomes, mainly on the relativistic Post Newtonian parameters. Finally we will conclude by indicating how space experiments (balloon SDS flights, Golf NG, Beppi-Colombo, Gaia... will be essential to unambiguously determine these parameters.
A model for evaluating the ballistic resistance of stratified packs
Pirvu, C.; Georgescu, C.; Badea, S.; Deleanu, L.
2016-08-01
Models for evaluating the ballistic performance of stratified packs are useful in reducing the time for laboratory tests, understanding the failure process and identifying key factors to improve the architecture of the packs. The authors present the results of simulating the bullet impact on a packs made of 24 layers, taking into consideration the friction between layers (μ = 0.4) and the friction between bullet and layers (μ = 0.3). The aim of this study is to obtain a number of layers that allows for the bullet arrest in the packs and to have several layers undamaged in order to offer a high level of safety for this kind of packs that could be included in individual armors. The model takes into account the yield and fracture limits of the two materials the bullet is made of and those for one layer, here considered as an orthotropic material, having maximum equivalent plastic strain of 0.06. All materials are considered to have bilinear isotropic hardening behavior. After documentation, the model was designed as isothermal because thermal influence of the impact is considered low for these impact velocities. The model was developed with the help of Ansys 14.5. Each layer has 200 mm × 200 × 0.35 mm. The bullet velocity just before impact was 400 m/s, a velocity characterizing the average values obtained in close range with a ballistic barrel and the bullet model is following the shape and dimensions of the 9 mm FMJ (full metal jacket). The model and the results concerning the number of broken layers were validated by experiments, as the number of broken layers for the actual pack (made of 24 layers of LFT SB1) were also seven...eight. The models for ballistic impact are useful when they are particularly formulated for resembling to the actual system projectile - target.
A new scoring system to stratify risk in unstable angina
Directory of Open Access Journals (Sweden)
Salzberg Simón
2003-08-01
Full Text Available Abstract Background We performed this study to develop a new scoring system to stratify different levels of risk in patients admitted to hospital with a diagnosis of unstable angina (UA, which is a complex syndrome that encompasses different outcomes. Many prognostic variables have been described but few efforts have been made to group them in order to enhance their individual predictive power. Methods In a first phase, 473 patients were prospectively analyzed to determine which factors were significantly associated with the in-hospital occurrence of refractory ischemia, acute myocardial infarction (AMI or death. A risk score ranging from 0 to 10 points was developed using a multivariate analysis. In a second phase, such score was validated in a new sample of 242 patients and it was finally applied to the entire population (n = 715. Results ST-segment deviation on the electrocardiogram, age ≥ 70 years, previous bypass surgery and troponin T ≥ 0.1 ng/mL were found as independent prognostic variables. A clear distinction was shown among categories of low, intermediate and high risk, defined according to the risk score. The incidence of the triple end-point was 6 %, 19.2 % and 44.7 % respectively, and the figures for AMI or death were 2 %, 11.4 % and 27.6 % respectively (p Conclusions This new scoring system is simple and easy to achieve. It allows a very good stratification of risk in patients having a clinical diagnosis of UA. They may be divided in three categories, which could be of help in the decision-making process.
Assessing iron dynamics in the release from a stratified reservoir
Ashby, S.L.; Faulkner, S.P.; Gambrell, R.P.; Smith, B.A.
2004-01-01
Field and laboratory studies were conducted to describe the fate of total, dissolved, and ferrous (Fe2.) iron in the release from a stratified reservoir with an anoxic hypolimnion. Concentrations of total iron in the tail water indicated a first order removal process during a low flow release (0.6 m3sec1), yet negligible loss was observed during a period of increased discharge (2.8 m 3 sec-1). Dissolved and ferrous iron concentrations in the tailwater were highly variable during both release regimes and did not follow responses based on theoretical predictions. Ferrous iron concentrations in unfiltered samples were consistently greater than concentrations observed in samples filtered separately through 0.4, 0.2, and 0.1 ??m filters. Total iron removal in laboratory studies followed first order kinetics, but was twice that rate (0.077 mg.L-1 .hr 1) observed during low flow discharge in the tailwater (0.036 mg. L1 .hr1). Dissolved and ferrous iron losses in laboratory studies were rapid (???75% in the first 15 minutes and 95% within 1 hour), followed theoretical predictions, and were much faster than observations in the tailwater (???30% within the first hour). The presence of particulate forms of ferrous iron in the field and differences in removal rates observed in field and laboratory studies indicate a need for improved field assessment techniques and consideration of complexation reactions when assessing the dynamics of iron in reservoir releases and downstream impacts as a result of operation regimes. ?? Copyright by the North American Lake Management Society 2004.
Interfacial instabilities in a stratified flow of two superposed fluids
Schaflinger, Uwe
1994-06-01
Here we shall present a linear stability analysis of a laminar, stratified flow of two superposed fluids which are a clear liquid and a suspension of solid particles. The investigation is based upon the assumption that the concentration remains constant within the suspension layer. Even for moderate flow-rates the base-state results for a shear induced resuspension flow justify the latter assumption. The numerical solutions display the existence of two different branches that contribute to convective instability: long and short waves which coexist in a certain range of parameters. Also, a range exists where the flow is absolutely unstable. That means a convectively unstable resuspension flow can be only observed for Reynolds numbers larger than a lower, critical Reynolds number but still smaller than a second critical Reynolds number. For flow rates which give rise to a Reynolds number larger than the second critical Reynolds number, the flow is absolutely unstable. In some cases, however, there exists a third bound beyond that the flow is convectively unstable again. Experiments show the same phenomena: for small flow-rates short waves were usually observed but occasionally also the coexistence of short and long waves. These findings are qualitatively in good agreement with the linear stability analysis. Larger flow-rates in the range of the second critical Reynolds number yield strong interfacial waves with wave breaking and detached particles. In this range, the measured flow-parameters, like the resuspension height and the pressure drop are far beyond the theoretical results. Evidently, a further increase of the Reynolds number indicates the transition to a less wavy interface. Finally, the linear stability analysis also predicts interfacial waves in the case of relatively small suspension heights. These results are in accordance with measurements for ripple-type instabilities as they occur under laminar and viscous conditions for a mono-layer of particles.
Magnetoacoustic Waves in Stratified Atmospheres with a Magnetic Null Point
Tarr, Lucas A.; Linton, Mark; Leake, James E.
2016-05-01
Magnetic fields strongly modify the propagation of MHD waves from the photosphere to the low corona, as can be shown exactly for the most simple case of a uniform magnetic field and isothermally stratrified atmosphere. For slightly more realistic scenarios, where both the atmospheric parameters and the magnetic field vary spatially, the linear MHD equations typically cannot be solved analytically. We use the Lagrangian Remap code--a nonlinear, shock-capturing MHD code--to study the propagation of initially acoustic wavepackets through a model 2D atmosphere that includes a gravitationally stratified chromosphere, transition region, and low corona. The magnetic field is formed by three photospheric concentrations and includes a single magnetic null point, resulting in an inhomogeneous system with a magnetic dome topology. A portion of an introduced wavepacket will refract toward the null due to the varying Alfven speed. Waves incident on the equipartition contour surrounding the null, where the sound and Alfven speeds coincide, partially transmit, reflect, and mode convert between branches of the local dispersion relation. Outward propagating slow modes generated during conversion become strongly concentrated along the set of field lines passing near the null. Acoustic energy is beamed back downwards towards each photospheric foot point, and upwards along one separatrix that exits the top of the numerical domain. Changes in the dominant restoring force for the wavepacket, between the Lorentz and pressure gradient forces, lead to a buildup of current density along topologically important features of the system (the null point and its four separatrices) and can drive reconnection at the null point itself. Ohmic dissipation of the currents locally heats the plasma. We find that the amount of current accumulation depends on where the centroid of a wavepacket initial crosses the photosphere, but does not simply coincide with regions of open versus closed magnetic field or
Electromagnetic rotational actuation.
Energy Technology Data Exchange (ETDEWEB)
Hogan, Alexander Lee
2010-08-01
There are many applications that need a meso-scale rotational actuator. These applications have been left by the wayside because of the lack of actuation at this scale. Sandia National Laboratories has many unique fabrication technologies that could be used to create an electromagnetic actuator at this scale. There are also many designs to be explored. In this internship exploration of the designs and fabrications technologies to find an inexpensive design that can be used for prototyping the electromagnetic rotational actuator.
Rotational spectrum of phenylglycinol
Simão, Alcides; Peña, Isabel; Cabezas, Carlos; Alonso, José L.
2014-11-01
Solid samples of phenylglycinol were vaporized by laser ablation and investigated through rotational spectroscopy in a supersonic expansion using two different techniques: chirped pulse Fourier transform microwave spectroscopy and narrow band molecular beam Fourier transform microwave spectroscopy. One conformer, bearing an O-H···N and an N-H···π intramolecular hydrogen bonds, could be successfully identified by comparison of the experimental rotational and 14N nuclear quadruple coupling constants with those predicted theoretically.
Earth rotation and geodynamics
Bogusz Janusz; Brzezinski Aleksander; Kosek Wieslaw; Nastula Jolanta
2015-01-01
This paper presents the summary of research activities carried out in Poland in 2011-2014 in the field of Earth rotation and geodynamics by several Polish research institutions. It contains a summary of works on Earth rotation, including evaluation and prediction of its parameters and analysis of the related excitation data as well as research on associated geodynamic phenomena such as geocentre motion, global sea level change and hydrological processes. The second part of the paper deals wit...
Directory of Open Access Journals (Sweden)
Mohamed A. E. S. Mahdy
2012-01-01
Conclusion: Safe and efficient phacoemulsification without nuclear rotation could be achieved in cases pseudoexfoliation in which zonular weakness is a concern by utilizing the versatility of Kelman style phaco tip to do lateral sweep sculpting and in situ cracking techniques. It prevents zonular stress by avoiding manipulation or rotation of the nucleus in cases.
Metric of a Slow Rotating Body with Quadrupole Moment from the Erez-Rosen Metric
Frutos-Alfaro, Francisco; Cordero-García, Iván; Ulloa-Esquivel, Oscar
2012-01-01
A metric representing a slow rotating object with quadrupole moment is obtained using the Newman-Janis formalism to include rotation into the weak limit of the Erez-Rosen metric. This metric is intended to tackle relativistic astrometry and gravitational lensing problems in which a quadrupole moment has to be taken into account.
Prat, Vincent; Lignières, François; Ballot, Jérôme; Culpin, Pierre-Marie
2016-01-01
Context. As of today, asteroseismology mainly allows us to probe internal rotation of stars when modes are only weakly affected by rotation using perturbative methods. Such methods cannot be applied to rapidly rotating stars, which exhibit complex oscillation spectra. In this context, the so-called traditional approximation, which neglects the terms associated with the latitudinal component of the rotation vector, describes modes that are strongly affected by rotation and is sometimes used for interpreting asteroseismic data. However, its domain of validity is not established yet. Aims. We aim at deriving analytical prescriptions for period spacings of low-frequency gravity modes strongly affected by rotation through the full Coriolis acceleration that can be used to probe stellar internal structure and rotation. Methods. The asymptotic theory of gravito-inertial waves in uniformly rotating stars using ray theory described by Prat et al. (2016, A&A, 587, A110) is approximated in the low-frequency regime, ...
Proposition of Unique Pumping System with Counter-Rotating Mechanism
Directory of Open Access Journals (Sweden)
Toshiaki Kanemoto
2004-01-01
Full Text Available Turbo-pumps have weak points, such as when the pumping operation becomes unstable in the rising portion of the head characteristics and/or the cavitation occurs under the intolerably low suction head. To overcome both weak points simultaneously, this article proposes a unique pumping system with counter-rotating mechanism, which consists of two stage impellers and a peculiar motor with double rotors. The front and the rear impellers are driven by the inner and the outer rotors of the motor, respectively, keeping the relative rotational speed constant and counter-balancing the rotational torque. Such driving conditions not only smartly improve the unstable performance at lower discharge, but also suppress the cavitation at higher discharge, in the optimum cooperation with the impeller works and the rotor outputs.
Weakly Distributive Modules. Applications to Supplement Submodules
Indian Academy of Sciences (India)
Engin Büyükaşik; Yilmaz M Demirci
2010-11-01
In this paper, we define and study weakly distributive modules as a proper generalization of distributive modules. We prove that, weakly distributive supplemented modules are amply supplemented. In a weakly distributive supplemented module every submodule has a unique coclosure. This generalizes a result of Ganesan and Vanaja. We prove that -projective duo modules, in particular commutative rings, are weakly distributive. Using this result we obtain that in a commutative ring supplements are unique. This generalizes a result of Camillo and Lima. We also prove that any weakly distributive $\\oplus$-supplemented module is quasi-discrete.
Weakly relativistic dispersion of Bernstein waves
Robinson, P. A.
1988-01-01
Weakly relativistic effects on the dispersion of Bernstein waves are investigated for waves propagating nearly perpendicular to a uniform magnetic field in a Maxwellian plasma. Attention is focused on those large-wave-vector branches that are either weakly damped or join continuously onto weakly damped branches since these are the modes of most interest in applications. The transition between dispersion at perpendicular and oblique propagation is examined and major weakly relativistic effects can dominate even in low-temperature plasmas. A number of simple analytic criteria are obtained which delimit the ranges of harmonic number and propagation angle within which various types of weakly damped Bernstein modes can exist.
Weakly relativistic dispersion of Bernstein waves
Robinson, P. A.
1988-01-01
Weakly relativistic effects on the dispersion of Bernstein waves are investigated for waves propagating nearly perpendicular to a uniform magnetic field in a Maxwellian plasma. Attention is focused on those large-wave-vector branches that are either weakly damped or join continuously onto weakly damped branches since these are the modes of most interest in applications. The transition between dispersion at perpendicular and oblique propagation is examined and major weakly relativistic effects can dominate even in low-temperature plasmas. A number of simple analytic criteria are obtained which delimit the ranges of harmonic number and propagation angle within which various types of weakly damped Bernstein modes can exist.
Magnetic field induced optical vortex beam rotation
Shi, Shuai; Zhou, Zhi-Yuan; Li, Yan; Zhang, Wei; Shi, Bao-Sen
2015-01-01
Light with orbital angular momentum (OAM) has drawn a great deal of attention for its important applications in the fields of precise optical measurements and high capacity optical communications. Here we adopt a method to study the rotation of a light beam, which is based on magnetic field induced circular birefringence in warm 87Rb atomic vapor. The dependence of the rotation angle to the intensity of the magnetic field makes it appropriate for weak magnetic field measurement. We derive a detail theoretical description that is in well agreement with the experimental observations. The experiment shows here provides a new method for precise measurement of magnetic field intensity and expands the application of OAM-carrying light.
Distribution of vaccine/antivirals and the 'least spread line' in a stratified population
Goldstein, E.; Apolloni, A.; Lewis, B.; Miller, J. C.; Macauley, M.; Eubank, S.; Lipsitch, M.; Wallinga, J.
2010-01-01
We describe a prioritization scheme for an allocation of a sizeable quantity of vaccine or antivirals in a stratified population. The scheme builds on an optimal strategy for reducing the epidemic's initial growth rate in a stratified mass-action model. The strategy is tested on the EpiSims network
Implementing content constraints in alpha-stratified adaptive using a shadow test approach
Linden, van der Wim J.; Chang, Hua-Hua
2003-01-01
The methods of alpha-stratified adaptive testing and constrained adaptive testing with shadow tests are combined. The advantages are twofold: First, application of the shadow test approach allows the implementation of any type of constraint on item selection in alpha-stratified adaptive testing. Sec
van der Linden, Wim J.; Chang, Hua-Hua
The methods of alpha-stratified adaptive testing and constrained adaptive testing with shadow tests are combined in this study. The advantages are twofold. First, application of the shadow test allows the researcher to implement any type of constraint on item selection in alpha-stratified adaptive testing. Second, the result yields a simple set of…
DEFF Research Database (Denmark)
Carmo, Carolina; Dumont, Olivier; Nielsen, Mads Pagh
2015-01-01
The use of stratified hot water tanks in solar energy systems - including ORC systems - as well as heat pump systems is paramount for a better performance of these systems. However, the availability of effective and reliable models to predict the annual performance of stratified hot water tanks c...
Lindsay, Colin R; Shaw, Emily; Walker, Ian; Johnson, Peter W M
2015-03-01
The implementation of stratified medicine in modern cancer care presents substantial opportunity to refine diagnosis and treatment but also numerous challenges. Through experience in a UK tumor profiling initiative, we have gained valuable insights into the complexities and possible solutions for routine delivery of stratified cancer medicine.
Optimal stratification of item pools in α-stratified computerized adaptive testing
Chang, Hua-Hua; Linden, van der Wim J.
2003-01-01
A method based on 0-1 linear programming (LP) is presented to stratify an item pool optimally for use in α-stratified adaptive testing. Because the 0-1 LP model belongs to the subclass of models with a network flow structure, efficient solutions are possible. The method is applied to a previous item
Rotational Rebound Attacks on Reduced Skein
DEFF Research Database (Denmark)
Khovratovich, Dmitry; Nikolic, Ivica; Rechberger, Christian
2010-01-01
In this paper we combine a recent rotational cryptanalysis with the rebound attack, which results in the best cryptanalysis of Skein, a candidate for the SHA-3 competition. The rebound attack approach was so far only applied to AES-like constructions. For the first time, we show that this approac...... inside-out computations and neutral bits in the inbound phase of the rebound attack, and give well-defined rotational distinguishers as certificates of weaknesses for the compression functions and block ciphers.......In this paper we combine a recent rotational cryptanalysis with the rebound attack, which results in the best cryptanalysis of Skein, a candidate for the SHA-3 competition. The rebound attack approach was so far only applied to AES-like constructions. For the first time, we show that this approach...... and the Threefish cipher. The new techniques include an analytical search for optimal input values in the rotational cryptanalysis, which allows to extend the outbound phase of the attack with a precomputation phase, an approach never used in any rebound-style attack before. Further we show how to combine multiple...
On Obliquely Magnetized and Differentially Rotating Stars
Wei, Xing; Goodman, Jeremy
2015-06-01
We investigate the interaction of differential rotation and a misaligned magnetic field. The incompressible magnetohydrodynamic equations are solved numerically for a free-decay problem. In the kinematic limit, differential rotation annihilates the non-axisymmetric field on a timescale proportional to the cube root of magnetic Reynolds number (Rm), as predicted by Rädler. Nonlinearly, the outcome depends upon the initial energy in the non-axisymmetric part of the field. Sufficiently weak fields approach axisymmetry as in the kinematic limit; some differential rotation survives across magnetic surfaces, at least on intermediate timescales. Stronger fields enforce uniform rotation and remain non-axisymmetric. The initial field strength that divides these two regimes does not follow the scaling R{{m}-1/3} predicted by quasi-kinematic arguments, perhaps because our Rm is never sufficiently large or because of reconnection. We discuss the possible relevance of these results to tidal synchronization and tidal heating of close binary stars, particularly double white dwarfs.
Scaling regimes in spherical shell rotating convection
Gastine, T; Aubert, J
2016-01-01
Rayleigh-B\\'enard convection in rotating spherical shells can be considered as a simplified analogue of many astrophysical and geophysical fluid flows. Here, we use three-dimensional direct numerical simulations to study this physical process. We construct a dataset of more than 200 numerical models that cover a broad parameter range with Ekman numbers spanning $3\\times 10^{-7} \\leq E \\leq 10^{-1}$, Rayleigh numbers within the range $10^3 < Ra < 2\\times 10^{10}$ and a Prandtl number unity. We investigate the scaling behaviours of both local (length scales, boundary layers) and global (Nusselt and Reynolds numbers) properties across various physical regimes from onset of rotating convection to weakly-rotating convection. Close to critical, the convective flow is dominated by a triple force balance between viscosity, Coriolis force and buoyancy. For larger supercriticalities, a subset of our numerical data approaches the asymptotic diffusivity-free scaling of rotating convection $Nu\\sim Ra^{3/2}E^{2}$ in ...
Claesson, E.M.; Erne, B.H.; Philipse, A.P.
2007-01-01
The weak permanent magnetic dipole moment of cobalt ferrite-doped colloidal silica spheres was increased by exposure to a saturating magnetic field. The resulting change of the rotational dynamics of the magnetic microspheres in a weak alternating field was measured from low to high volume fraction
A Universe without Weak Interactions
Energy Technology Data Exchange (ETDEWEB)
Harnik, Roni; Kribs, Graham D.; Perez, Gilad
2006-04-07
A universe without weak interactions is constructed that undergoes big-bang nucleosynthesis, matter domination, structure formation, and star formation. The stars in this universe are able to burn for billions of years, synthesize elements up to iron, and undergo supernova explosions, dispersing heavy elements into the interstellar medium. These definitive claims are supported by a detailed analysis where this hypothetical ''Weakless Universe'' is matched to our Universe by simultaneously adjusting Standard Model and cosmological parameters. For instance, chemistry and nuclear physics are essentially unchanged. The apparent habitability of the Weakless Universe suggests that the anthropic principle does not determine the scale of electroweak breaking, or even require that it be smaller than the Planck scale, so long as technically natural parameters may be suitably adjusted. Whether the multi-parameter adjustment is realized or probable is dependent on the ultraviolet completion, such as the string landscape. Considering a similar analysis for the cosmological constant, however, we argue that no adjustments of other parameters are able to allow the cosmological constant to raise up even remotely close to the Planck scale while obtaining macroscopic structure. The fine-tuning problems associated with the electroweak breaking scale and the cosmological constant therefore appear to be qualitatively different from the perspective of obtaining a habitable universe.
A universe without weak interactions
Harnik, Roni; Kribs, Graham D.; Perez, Gilad
2006-08-01
A universe without weak interactions is constructed that undergoes big-bang nucleosynthesis, matter domination, structure formation, and star formation. The stars in this universe are able to burn for billions of years, synthesize elements up to iron, and undergo supernova explosions, dispersing heavy elements into the interstellar medium. These definitive claims are supported by a detailed analysis where this hypothetical “weakless universe” is matched to our Universe by simultaneously adjusting standard model and cosmological parameters. For instance, chemistry and nuclear physics are essentially unchanged. The apparent habitability of the weakless universe suggests that the anthropic principle does not determine the scale of electroweak breaking, or even require that it be smaller than the Planck scale, so long as technically natural parameters may be suitably adjusted. Whether the multiparameter adjustment is realized or probable is dependent on the ultraviolet completion, such as the string landscape. Considering a similar analysis for the cosmological constant, however, we argue that no adjustments of other parameters are able to allow the cosmological constant to raise up even remotely close to the Planck scale while obtaining macroscopic structure. The fine-tuning problems associated with the electroweak breaking scale and the cosmological constant therefore appear to be qualitatively different from the perspective of obtaining a habitable universe.
Weak homology of elliptical galaxies
Bertin, G; Principe, M D
2002-01-01
We start by studying a small set of objects characterized by photometric profiles that have been pointed out to deviate significantly from the standard R^{1/4} law. For these objects we confirm that a generic R^{1/n} law, with n a free parameter, can provide superior fits (the best-fit value of n can be lower than 2.5 or higher than 10), better than those that can be obtained by a pure R^{1/4} law, by an R^{1/4}+exponential model, and by other dynamically justified self--consistent models. Therefore, strictly speaking, elliptical galaxies should not be considered homologous dynamical systems. Still, a case for "weak homology", useful for the interpretation of the Fundamental Plane of elliptical galaxies, could be made if the best-fit parameter n, as often reported, correlates with galaxy luminosity L, provided the underlying dynamical structure also follows a systematic trend with luminosity. We demonstrate that this statement may be true even in the presence of significant scatter in the correlation n(L). Pr...
Testing the weak equivalence principle
Nobili, Anna M.; Comandi, Gian Luca; Pegna, Raffaello; Bramanti, Donato; Doravari, Suresh; Maccarone, Francesco; Lucchesi, David M.
2010-01-01
The discovery of Dark Energy and the fact that only about 5% of the mass of the universe can be explained on the basis of the current laws of physics have led to a serious impasse. Based on past history, physics might indeed be on the verge of major discoveries; but the challenge is enormous. The way to tackle it is twofold. On one side, scientists try to perform large scale direct observations and measurements - mostly from space. On the other, they multiply their efforts to put to the most stringent tests ever the physical theories underlying the current view of the physical world, from the very small to the very large. On the extremely small scale very exciting results are expected from one of the most impressive experiments in the history of mankind: the Large Hadron Collider. On the very large scale, the universe is dominated by gravity and the present impasse undoubtedly calls for more powerful tests of General Relativity - the best theory of gravity to date. Experiments testing the Weak Equivalence Principle, on which General Relativity ultimately lies, have the strongest probing power of them all; a breakthrough in sensitivity is possible with the “Galileo Galilei” (GG) satellite experiment to fly in low Earth orbit.
The Geometry And Significance Of Weak Energy
Parks, A D
2000-01-01
Summary: The theory of weak values for quantum mechanical observables has come to serve as a useful basis for contemporary discussions concerning such varied topics as the tunnelling-time controversy and quantum stochastic processes. An intrinsic complex-valued weak energy has recently been observed experimentally and reported in the literature. In this paper it is shown that: (a) the real and imaginary valued parts of this weak energy have geometric interpretations related to a phase acquired from parallel transport in Hilbert space and the variational dynamics occurring in the associated projective Hilbert space, respectively; (b) the weak energy defines functions which translate correlation amplitudes and probabilities in time; (c) correlation probabilities can be controlled by manipulating the weak energy and there exists a condition of weak stationarity that guarantees their time invariance; and (d) a time-weak energy uncertainty relation of the usual form prevails when a suitable set of dynamical constr...
Rotating superconductor magnet for producing rotating lobed magnetic field lines
Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.
1978-01-01
This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.
Takehiro, S.; Sasaki, Y.; Hayashi, Y.-Y.; Yamada, M.
2013-12-01
We investigate generation mechanisms of differential rotation and angular momentum transport caused by Boussinesq thermal convection in a rotating spherical shell based on weakly nonlinear numerical calculations for various values of the Prandtl and Ekman numbers under a setup similar to the solar convection layer. When the Prandtl number is of order unity or less and the rotation rate of the system is small (the Ekman number is larger than O(10-2)), the structure of thermal convection is not governed by the Taylor-Proudman theorem; banana-type convection cells emerge which follow the spherical shell boundaries rather than the rotation axis. Due to the Coriolis effect, the velocity field associated with those types of convection cells accompanies the Reynolds stress which transports angular momentum from high-latitudes to the equatorial region horizontally, and equatorial prograde flows are produced. The surface and internal distributions of differential rotation realized in this regime are quite similar to those observed in the Sun with helioseismology. These results may suggest that we should apply larger values of the eddy diffusivities than those believed so far when we use a low resolution numerical model for thermal convection in the solar interior.
Weak* convergence of operator means
Energy Technology Data Exchange (ETDEWEB)
Romanov, Alexandr V [Moscow State Institute of Electronics and Mathematics (Technical University), Moscow (Russian Federation)
2011-12-31
For a linear operator U with ||U'n||{<=}const on a Banach space X we discuss conditions for the convergence of ergodic operator nets T{sub {alpha}} corresponding to the adjoint operator U* of U in the W*O-topology of the space EndX*. The accumulation points of all possible nets of this kind form a compact convex set L in EndX*, which is the kernel of the operator, where {Gamma}{sub 0}={l_brace}U{sub n}*, n{>=}0{r_brace}. It is proved that all ergodic nets T{sub {alpha}} weakly* converge if and only if the kernel L consists of a single element. In the case of X=C({Omega}) and the shift operator U generated by a continuous transformation {phi} of a metrizable compactum {Omega} we trace the relationships among the ergodic properties of U, the structure of the operator semigroups L, G and {Gamma}={Gamma}-bar{sub 0}, and the dynamical characteristics of the semi-cascade ({phi},{Omega}). In particular, if cardL=1, then a) for any {omega} element of {Omega} the closure of the trajectory {l_brace}{phi}{sup n}{omega}, n{>=}0{r_brace} contains precisely one minimal set m, and b) the restriction ({phi},m) is strictly ergodic. Condition a) implies the W*O-convergence of any ergodic sequence of operators T{sub n} element of EndX* under the additional assumption that the kernel of the enveloping semigroup E({phi},{Omega}) contains elements obtained from the 'basis' family of transformations {l_brace}{phi}{sup n}, n{>=}0{r_brace} of the compact set {Omega} by using some transfinite sequence of sequential passages to the limit.
Gehan, Charlotte; Michel, Eric
2016-01-01
Stellar oscillations give seismic information on the internal properties of stars. Red giants are targets of interest since they present mixed modes, which behave as pressure modes in the convective envelope and as gravity modes in the radiative core. Mixed modes thus directly probe red giant cores, and allow in particular the study of their mean core rotation. The high-quality data obtained by CoRoT and Kepler satellites represent an unprecedented perspective to obtain thousands of measurements of red giant core rotation, in order to improve our understanding of stellar physics in deep stellar interiors. We developed an automated method to obtain such core rotation measurements and validated it for stars on the red giant branch. In this work, we particularly focus on the specific application of this method to red giants having a rapid core rotation. They show complex spectra where it is tricky to disentangle rotational splittings from mixed-mode period spacings. We demonstrate that the method based on the id...
Vibrations of rotating machinery
Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick
2017-01-01
This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...
Chiral Rotational Spectroscopy
Cameron, Robert P; Barnett, Stephen M
2015-01-01
We introduce chiral rotational spectroscopy: a new technique that enables the determination of the individual optical activity polarisability components $G_{XX}'$, $G_{YY}'$, $G_{ZZ}'$, $A_{X,YZ}$, $A_{Y,ZX}$ and $A_{Z,XY}$ of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample whilst yielding an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral by virtue of their isotopic constitution and molecules with multiple chiral centres. The principles that underpin chiral rotational spectroscopy can also be exploited in the search for molecular chirality in space, which, if found, may add weight to hypotheses that biological homochirality and indeed life itself are of cosmic origin.
Chiral rotational spectroscopy
Cameron, Robert P.; Götte, Jörg B.; Barnett, Stephen M.
2016-09-01
We introduce chiral rotational spectroscopy, a technique that enables the determination of the orientated optical activity pseudotensor components BX X, BY Y, and BZ Z of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample and provides an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral solely by virtue of their isotopic constitution and molecules with multiple chiral centers. A basic design for a chiral rotational spectrometer together with a model of its functionality is given. Our proposed technique offers the more familiar polarizability components αX X, αY Y, and αZ Z as by-products, which could see it find use even for achiral molecules.
Dorbolo, Stephane; Adami, Nicolas; Grasp Team
2014-11-01
The motion of ice discs released at the surface of a thermalized bath was investigated. As observed in some rare events in the Nature, the discs start spinning spontaneously. The motor of this motion is the cooling of the water close to the ice disc. As the density of water is maximum at 4°C, a downwards flow is generated from the surface of the ice block to the bottom. This flow generates the rotation of the disc. The speed of rotation depends on the mass of the ice disc and on the temperature of the bath. A model has been constructed to study the influence of the temperature of the bath. Finally, ice discs were put on a metallic plate. Again, a spontaneous rotation was observed. FNRS is thanked for financial support.
DEFF Research Database (Denmark)
Tandrup, T; Gundersen, Hans Jørgen Gottlieb; Jensen, Eva B. Vedel
1997-01-01
The optical rotator is an unbiased, local stereological principle for estimation of cell volume and cell surface area in thick, transparent slabs, The underlying principle was first described in 1993 by Kieu Jensen (T. Microsc. 170, 45-51) who also derived an estimator of length, In this study we...... further discuss the methods derived from this principle and present two new local volume estimators. The optical rotator benefits from information obtained in all three dimensions in thick sections but avoids over-/ underprojection problems at the extremes of the cell. Using computer-assisted microscopes...... the extra measurements demand minimal extra effort and make this estimator even more efficient when it comes to estimation of individual cell size than many of the previous local estimators, We demonstrate the principle of the optical rotator in an example (the cells in the dorsal root ganglion of the rat...
Rotation of cometary meteoroids
Capek, David
2014-01-01
The aim of this study is to estimate the rotational characteristics of meteoroids after their release from a comet during normal activity. The results can serve as initial conditions for further analyses of subsequent evolution of rotation in the interplanetary space. A sophisticated numerical model was applied to meteoroids ejected from 2P/Encke comet. The meteoroid shapes were approximated by polyhedrons with several thousands of surface elements, which have been determined by 3D laser scanning method of 36 terrestrial rock samples. These samples came from three distinct sets with different origin and shape characteristics. Two types of gas-meteoroid interactions (diffuse and specular reflection of gas molecules from the surface of meteoroid) and three gas ejection models (leading to very different ejection velocities) were assumed. The rotational characteristics of ejected meteoroid population were obtained by numerical integration of equations of motion with random initial conditions and random shape sele...
Rotation and plasma stability in the Fitzpatrick-Aydemir model
Pustovitov, V. D.
2007-08-01
The rotational stabilization of the resistive wall modes (RWMs) is analyzed within the single-mode cylindrical Fitzpatrick-Aydemir model [R. Fitzpatrick, Phys. Plasmas 9, 3459 (2002)]. Here, the consequences of the Fitzpatrick-Aydemir dispersion relation are derived in terms of the observable growth rate and toroidal rotation frequency of the mode, which allows easy interpretation of the results and comparison with experimental observations. It is shown that this model, developed for the plasma with weak dissipation, predicts the rotational destabilization of RWM in the typical range of the RWM rotation. The model predictions are compared with those obtained in a similar model, but with the Boozer boundary conditions at the plasma surface [A. H. Boozer, Phys. Plasmas 11, 110 (2004)]. Simple experimental tests of the model are proposed.
Modeling the Parker instability in a rotating plasma screw pinch
Khalzov, I V; Katz, N; Forest, C B; 10.1063/1.3684240
2012-01-01
We analytically and numerically study the analogue of the Parker (magnetic buoyancy) instability in a uniformly rotating plasma screw pinch confined in a cylinder. Uniform plasma rotation is imposed to create a centrifugal acceleration, which mimics the gravity required for the classical Parker instability. The goal of this study is to determine how the Parker instability could be unambiguously identified in a weakly magnetized, rapidly rotating screw pinch, in which the rotation provides an effective gravity and a radially varying azimuthal field is controlled to give conditions for which the plasma is magnetically buoyant to inward motion. We show that an axial magnetic field is also required to circumvent conventional current driven magnetohydrodynamic (MHD) instabilities such as the sausage and kink modes that would obscure the Parker instability. These conditions can be realized in the Madison Plasma Couette Experiment (MPCX). Simulations are performed using the extended MHD code NIMROD for an isothermal...
Indications for tonsillectomy stratified by the level of evidence
Windfuhr, Jochen P.
2016-01-01
Background: One of the most significant clinical trials, demonstrating the efficacy of tonsillectomy (TE) for recurrent throat infection in severely affected children, was published in 1984. This systematic review was undertaken to compile various indications for TE as suggested in the literature after 1984 and to stratify the papers according to the current concept of evidence-based medicine. Material and methods: A systematic Medline research was performed using the key word of “tonsillectomy“ in combination with different filters such as “systematic reviews“, “meta-analysis“, “English“, “German“, and “from 1984/01/01 to 2015/05/31“. Further research was performed in the Cochrane Database of Systematic Reviews, National Guideline Clearinghouse, Guidelines International Network and BMJ Clinical Evidence using the same key word. Finally, data from the “Trip Database” were researched for “tonsillectomy” and “indication“ and “from: 1984 to: 2015“ in combination with either “systematic review“ or “meta-analysis“ or “metaanalysis”. Results: A total of 237 papers were retrieved but only 57 matched our inclusion criteria covering the following topics: peritonsillar abscess (3), guidelines (5), otitis media with effusion (5), psoriasis (3), PFAPA syndrome (6), evidence-based indications (5), renal diseases (7), sleep-related breathing disorders (11), and tonsillitis/pharyngitis (12), respectively. Conclusions: 1) The literature suggests, that TE is not indicated to treat otitis media with effusion. 2) It has been shown, that the PFAPA syndrome is self-limiting and responds well to steroid administration, at least in a considerable amount of children. The indication for TE therefore appears to be imbalanced but further research is required to clarify the value of surgery. 3) Abscesstonsillectomy as a routine is not justified and indicated only for cases not responding to other measures of treatment, evident complications
Weakly and Strongly Regular Near-rings
Institute of Scientific and Technical Information of China (English)
N.Argac; N.J.Groenewald
2005-01-01
In this paper, we prove some basic properties of left weakly regular near-rings.We give an affirmative answer to the question whether a left weakly regular near-ring with left unity and satisfying the IFP is also right weakly regular. In the last section, we use among others left 0-prime and left completely prime ideals to characterize strongly regular near-rings.
WEAK CONVERGENCE OF HENSTOCK INTEGRABLE SEQUENCES
Institute of Scientific and Technical Information of China (English)
LuisaDiPiazza
1994-01-01
Some relationships between pointwise and weak convergence of a sequence of Henstock integrable functions are studied, In particular it is provided an example of a sequence of Henstock integrable functions whose pointwise limit is different from the weak one. By introducing an asymptotic version of the Henstock equiintegrability notion it is given a necessary and sufficient condition in order that a pointwisely convergent sequence of Henstock integrable functions is weakly convergent to its pointwise limit.
Transversality theorems for the weak topology
2011-01-01
In his 1979 paper Trotman proves, using the techniques of the Thom transversality theorem, that under some conditions on the dimensions of the manifolds under consideration, openness of the set of maps transverse to a stratification in the strong (Whitney) topology implies that the stratification is $(a)$-regular. Here we first discuss the Thom transversality theorem for the weak topology and then give a similiar kind of result for the weak topology, under very weak hypotheses. Recently sever...
Spin effects in the weak interaction
Energy Technology Data Exchange (ETDEWEB)
Freedman, S.J. (Argonne National Lab., IL (USA) Chicago Univ., IL (USA). Dept. of Physics Chicago Univ., IL (USA). Enrico Fermi Inst.)
1990-01-01
Modern experiments investigating the beta decay of the neutron and light nuclei are still providing important constraints on the theory of the weak interaction. Beta decay experiments are yielding more precise values for allowed and induced weak coupling constants and putting constraints on possible extensions to the standard electroweak model. Here we emphasize the implications of recent experiments to pin down the strengths of the weak vector and axial vector couplings of the nucleon.
Institute of Scientific and Technical Information of China (English)
Xiang Yue-ming; Ouyang Lun-qun; Wang Shu-gui
2015-01-01
We introduce, in this paper, the right weakly p.p. rings as the generaliza-tion of right p.p. rings. It is shown that many properties of the right p.p. rings can be extended onto the right weakly p.p. rings. Relative examples are constructed. As applications, we also characterize the regular rings and the semisimple rings in terms of the right weakly p.p. rings.
Weak measurements with a qubit meter
DEFF Research Database (Denmark)
Wu, Shengjun; Mølmer, Klaus
2009-01-01
We derive schemes to measure the so-called weak values of quantum system observables by coupling of the system to a qubit meter system. We highlight, in particular, the meaning of the imaginary part of the weak values, and show how it can be measured directly on equal footing with the real part...... of the weak value. We present compact expressions for the weak value of single qubit observables and of product observables on qubit pairs. Experimental studies of the results are suggested with cold trapped ions....
Transport Phenomena in Stratified Multi-Fluid Flow in the Presence and Absence of Gravity
Chigier, Norman; Humphrey, William
1996-01-01
Experiments are being conducted to study the effects of buoyancy on planar density-stratified shear flows. A wind tunnel generates planar flows separated by an insulating splitter plate, with either flow heated, which emerge from a two-dimensional nozzle. The objective is to isolate and define the effect of gravity and buoyancy on a stratified shear layer. To this end, both stably and unstably stratified layers will be investigated. This paper reports on the results of temperature and velocity measurements across the nozzle exit plane and downstream along the nozzle center plane.
Electromotive force due to magnetohydrodynamic fluctuations in sheared rotating turbulence.
Squire, J; Bhattacharjee, A
2015-11-01
This article presents a calculation of the mean electromotive force arising from general small-scale magnetohydrodynamical turbulence, within the framework of the second-order correlation approximation. With the goal of improving understanding of the accretion disk dynamo, effects arising through small-scale magnetic fluctuations, velocity gradients, density and turbulence stratification, and rotation, are included. The primary result, which supplements numerical findings, is that an off-diagonal turbulent resistivity due to magnetic fluctuations can produce large-scale dynamo action-the magnetic analog of the "shear-current" effect. In addition, consideration of α effects in the stratified regions of disks gives the puzzling result that there is no strong prediction for a sign of α, since the effects due to kinetic and magnetic fluctuations, as well as those due to shear and rotation, are each of opposing signs and tend to cancel each other.
Effect of rotation on a rotating hot-wire sensor
Hah, C.; Lakshminarayana, B.
1978-01-01
An investigation was conducted to discern the effects of centrifugal and Coriolis forces on a rotating hot-wire. The probe was calibrated in a wind tunnel as well as in a rotating mode. The effect of rotation was found to be negligibly small. A small change in cold resistance (1.5%) was observed in the rotating wire. The rotation seems to have a negligible effect on the fluid mechanics, heat transfer and material characteristics of the wire. This is a significant conclusion in view of the potential application of the hot-wire probe in a rotating passage (such as turbomachinery).
DEFF Research Database (Denmark)
Rasmusson, Allan
2009-01-01
The inherent demand for unbiasedness for some stereological estimators imposes a demand of not only positional uniform randomness but also isotropic randomness, i.e. directional uniform randomness. In order to comply with isotropy, one must perform a random rotation of the object of interest befo...
Connors, G. Patrick
Many baseball players suffer from shoulder injuries related to the rotator cuff muscles. These injuries may be classified as muscular strain, tendonitis or tenosynovitis, and impingement syndrome. Treatment varies from simple rest to surgery, so it is important to be seen by a physician as soon as possible. In order to prevent these injuries, the…
Connors, G. Patrick
Many baseball players suffer from shoulder injuries related to the rotator cuff muscles. These injuries may be classified as muscular strain, tendonitis or tenosynovitis, and impingement syndrome. Treatment varies from simple rest to surgery, so it is important to be seen by a physician as soon as possible. In order to prevent these injuries, the…
Compact rotating cup anemometer
Wellman, J. B.
1968-01-01
Compact, collapsible rotating cup anemometer is used in remote locations where portability and durability are factors in the choice of equipment. This lightweight instrument has a low wind-velocity threshold, is capable of withstanding large mechanical shocks while in its stowed configuration, and has fast response to wind fluctuations.
Davies, Paul Charles William; Manogue, C A; Davies, Paul C W; Dray, Tevian; Manogue, Corinne A
1996-01-01
We derive conditions for rotating particle detectors to respond in a variety of bounded spacetimes and compare the results with the folklore that particle detectors do not respond in the vacuum state appropriate to their motion. Applications involving possible violations of the second law of thermodynamics are briefly addressed.
Rotationally Actuated Prosthetic Hand
Norton, William E.; Belcher, Jewell G., Jr.; Carden, James R.; Vest, Thomas W.
1991-01-01
Prosthetic hand attached to end of remaining part of forearm and to upper arm just above elbow. Pincerlike fingers pushed apart to degree depending on rotation of forearm. Simpler in design, simpler to operate, weighs less, and takes up less space.
Strong Dependence of the Inner Edge of the Habitable Zone on Planetary Rotation Rate
Yang, Jun; Fabrycky, Daniel C; Abbot, Dorian S
2014-01-01
Planetary rotation rate is a key parameter in determining atmospheric circulation and hence the spatial pattern of clouds. Since clouds can exert a dominant control on planetary radiation balance, rotation rate could be critical for determining mean planetary climate. Here we investigate this idea using a three-dimensional general circulation model with a sophisticated cloud scheme. We find that slowly rotating planets (like Venus) can maintain an Earth-like climate at nearly twice the stellar flux as rapidly rotating planets (like Earth). This suggests that many exoplanets previously believed to be too hot may actually be habitable, depending on their rotation rate. The explanation for this behavior is that slowly rotating planets have a weak Coriolis force and long daytime illumination, which promotes strong convergence and convection in the substellar region. This produces a large area of optically thick clouds, which greatly increases the planetary albedo. In contrast, on rapidly rotating planets a much n...
Featherstone, Nicholas A
2016-01-01
We investigate how rotationally-constrained, deep convection might give rise to supergranulation, the largest distinct spatial scale of convection observed in the solar photosphere. While supergranulation is only weakly influenced by rotation, larger spatial scales of convection sample the deep convection zone and are presumably rotationally influenced. We present numerical results from a series of nonlinear, 3-D simulations of rotating convection and examine the velocity power distribution realized under a range of Rossby numbers. When rotation is present, the convective power distribution possesses a pronounced peak, at characteristic wavenumber $\\ell_\\mathrm{peak}$, whose value increases as the Rossby number is decreased. This distribution of power contrasts with that realized in non-rotating convection, where power increases monotonically from high to low wavenumbers. We find that spatial scales smaller than $\\ell_\\mathrm{peak}$ behave in analogy to non-rotating convection. Spatial scales larger than $\\el...
The fiber optic gyroscope - a portable rotational ground motion sensor
Wassermann, J. M.; Bernauer, F.; Guattari, F.; Igel, H.
2016-12-01
It was already shown that a portable broadband rotational ground motion sensor will have large impact on several fields of seismological research such as volcanology, marine geophysics, seismic tomography and planetary seismology. Here, we present results of tests and experiments with one of the first broadband rotational motion sensors available. BlueSeis-3A, is a fiber optic gyroscope (FOG) especially designed for the needs of seismology, developed by iXBlue, France, in close collaboration with researchers financed by the European Research council project ROMY (Rotational motions - a new observable for seismology). We first present the instrument characteristics which were estimated by different standard laboratory tests, e.g. self noise using operational range diagrams or Allan deviation. Next we present the results of a field experiment which was designed to demonstrate the value of a 6C measurement (3 components of translation and 3 components of rotation). This field test took place at Mt. Stromboli volcano, Italy, and is accompanied by seismic array installation to proof the FOG output against more commonly known array derived rotation. As already shown with synthetic data an additional direct measurement of three components of rotation can reduce the ambiguity in source mechanism estimation and can be taken to correct for dynamic tilt of the translational sensors (i.e. seismometers). We can therefore demonstrate that the deployment of a weak motion broadband rotational motion sensor is in fact producing superior results by a reduction of the number of deployed instruments.
Weak interaction: past answers, present questions
Energy Technology Data Exchange (ETDEWEB)
Ne' eman, Y.
1977-02-01
A historical sketch of the weak interaction is presented. From beta ray to pion decay, the V-A theory of Marshak and Sudarshan, CVC principle of equivalence, universality as an algebraic condition, PCAC, renormalized weak Hamiltonian in the rehabilitation of field theory, and some current issues are considered in this review. 47 references. (JFP)
On modeling weak sinks in MODPATH
Abrams, Daniel B.; Haitjema, Henk; Kauffman, Leon J.
2012-01-01
Regional groundwater flow systems often contain both strong sinks and weak sinks. A strong sink extracts water from the entire aquifer depth, while a weak sink lets some water pass underneath or over the actual sink. The numerical groundwater flow model MODFLOW may allow a sink cell to act as a strong or weak sink, hence extracting all water that enters the cell or allowing some of that water to pass. A physical strong sink can be modeled by either a strong sink cell or a weak sink cell, with the latter generally occurring in low resolution models. Likewise, a physical weak sink may also be represented by either type of sink cell. The representation of weak sinks in the particle tracing code MODPATH is more equivocal than in MODFLOW. With the appropriate parameterization of MODPATH, particle traces and their associated travel times to weak sink streams can be modeled with adequate accuracy, even in single layer models. Weak sink well cells, on the other hand, require special measures as proposed in the literature to generate correct particle traces and individual travel times and hence capture zones. We found that the transit time distributions for well water generally do not require special measures provided aquifer properties are locally homogeneous and the well draws water from the entire aquifer depth, an important observation for determining the response of a well to non-point contaminant inputs.
Spin Seebeck effect in a weak ferromagnet
Arboleda, Juan David; Arnache Olmos, Oscar; Aguirre, Myriam Haydee; Ramos, Rafael; Anadon, Alberto; Ibarra, Manuel Ricardo
2016-06-01
We report the observation of room temperature spin Seebeck effect (SSE) in a weak ferromagnetic normal spinel Zinc Ferrite (ZFO). Despite the weak ferromagnetic behavior, the measurements of the SSE in ZFO show a thermoelectric voltage response comparable with the reported values for other ferromagnetic materials. Our results suggest that SSE might possibly originate from the surface magnetization of the ZFO.
CP Violation, Neutral Currents, and Weak Equivalence
Fitch, V. L.
1972-03-23
Within the past few months two excellent summaries of the state of our knowledge of the weak interactions have been presented. Correspondingly, we will not attempt a comprehensive review but instead concentrate this discussion on the status of CP violation, the question of the neutral currents, and the weak equivalence principle.
Towards a classification of weak hand holds
Kimmelman, V.; Sáfár, A.; Crasborn, O.
2016-01-01
The two symmetrical manual articulators (the hands) in signed languages are a striking modalityspecific phonetic property. The weak hand can maintain the end position of an articulation while the other articulator continues to produce additional signs. This weak hand spreading (hold) has been
Revisiting Weak Simulation for Substochastic Markov Chains
DEFF Research Database (Denmark)
Jansen, David N.; Song, Lei; Zhang, Lijun
2013-01-01
The spectrum of branching-time relations for probabilistic systems has been investigated thoroughly by Baier, Hermanns, Katoen and Wolf (2003, 2005), including weak simulation for systems involving substochastic distributions. Weak simulation was proven to be sound w.r.t. the liveness fragment...
S-parameters for weakly excited slots
DEFF Research Database (Denmark)
Albertsen, Niels Christian
1999-01-01
A simple approach to account for parasitic effects in weakly excited slots cut in the broad wall of a rectangular waveguide is proposed......A simple approach to account for parasitic effects in weakly excited slots cut in the broad wall of a rectangular waveguide is proposed...
Weakly exact categories and the snake lemma
Jafari, Amir
2009-01-01
We generalize the notion of an exact category and introduce weakly exact categories. A proof of the snake lemma in this general setting is given. Some applications are given to illustrate how one can do homological algebra in a weakly exact category.
Strong Connections and Invertible Weak Entwining Structures
Institute of Scientific and Technical Information of China (English)
J.N.ALONSO (A)LVAREZ; J.M.FERN(A)NDEZ VILABOA; R.GONZ(A)LEZ RODR(I)GUEZ
2012-01-01
In this paper we obtain a criterion under which the bijectivity of the canonical morphism of a weak Galois extension associated to a weak invertible entwining structure is equivalent to the existence of a strong connection form.Also we obtain an explicit formula for a strong connection under equivariant projective conditions or under coseparability conditions.
Weakly tight functions and their decomposition
Directory of Open Access Journals (Sweden)
Mona Khare
2005-01-01
Full Text Available The present paper deals with the study of a weakly tight function and its relation to tight functions. We obtain a Jordan-decomposition-type theorem for a locally bounded weakly tight real-valued function defined on a sublattice of IX, followed by the notion of a total variation.
Cohomology of Weakly Reducible Maximal Triangular Algebras
Institute of Scientific and Technical Information of China (English)
董浙; 鲁世杰
2000-01-01
In this paper, we introduce the concept of weakly reducible maximal triangular algebras φwhich form a large class of maximal triangular algebras. Let B be a weakly closed algebra containing 5φ, we prove that the cohomology spaces Hn(φ, B) (n≥1) are trivial.
Blow-Up Criterion of Weak Solutions for the 3D Boussinesq Equations
Directory of Open Access Journals (Sweden)
Zhaohui Dai
2015-01-01
Full Text Available The Boussinesq equations describe the three-dimensional incompressible fluid moving under the gravity and the earth rotation which come from atmospheric or oceanographic turbulence where rotation and stratification play an important role. In this paper, we investigate the Cauchy problem of the three-dimensional incompressible Boussinesq equations. By commutator estimate, some interpolation inequality, and embedding theorem, we establish a blow-up criterion of weak solutions in terms of the pressure p in the homogeneous Besov space Ḃ∞,∞0.
Institute of Scientific and Technical Information of China (English)
QIU Xiang
2006-01-01
Turbulence structures and turbulent Counter-Gradient Transport(CGT) properties in the stratified flows with a sharp temperature interface are investigated by experimental measurements using LIF and PIV, by LES and by correlation analysis.
Development of a Curved, Stratified, In Vitro Model to Assess Ocular Biocompatibility: e96448
National Research Council Canada - National Science Library
Cameron K Postnikoff; Robert Pintwala; Sara Williams; Ann M Wright; Denise Hileeto; Maud B Gorbet
2014-01-01
.... Methods Immortalized human corneal epithelial cells were grown to confluency on curved cellulose filters for seven days, and were then differentiated and stratified using an air-liquid interface...
Banakh, Taras
2008-01-01
We introduce and study (metrically) quarter-stratifiable spaces and then apply them to generalize Rudin and Kuratowski-Montgomery theorems about the Baire and Borel complexity of separately continuous functions.
Stratified shear flow in an inclined duct: coherent structures and mixing
Lefauve, Adrien; Partridge, Jamie; Dalziel, Stuart; Linden, Paul
2016-11-01
We present laboratory experiments on the exchange flow in an inclined square duct connecting two reservoirs at different densities. This system generates and maintains a stratified shear flow, which can be laminar, wavy or turbulent depending on the density difference and inclination angle. It is believed that the mean dissipation is set by the angle, and that high buoyancy Reynolds numbers (i.e. turbulent intensity) can be maintained, making this system suited for the study of continuously forced stratified turbulence. The talk will focus on the analysis of time-resolved, near-instantaneous 3D velocity and density data obtained by stereo particle image velocimetry (PIV) and laser induced fluorescence (LIF). This data allow for the visualisation of 3D coherent structures as well as turbulent mixing properties, which are key in understanding the dynamics of stratified turbulence. Supported by EPSRC Programme Grant EP/K034529/1 entitled "Mathematical Underpinnings of Stratified Turbulence".
Energy Technology Data Exchange (ETDEWEB)
Shudo, Toshio [Applied Energy System Group, Division of Energy and Environmental Systems, Hokkaido University, N13 W8 Kita-Ward, Sapporo, Hokkaido 060-8628 (Japan); Oba, Shuji [Mazda Motor Corporation, Hiroshima 730-8670 (Japan)
2009-03-15
Reduction in cooling loss due to the heat transfer from burning gas to the combustion chamber wall is very important for improving the thermal efficiency in hydrogen engines. The previous research has shown that the direct injection stratified charge can be a technique to reduce the cooling loss and improve thermal efficiency in hydrogen combustion. For effective reductions in cooling loss by the stratified charge, it is very important to know the relation between the fuel injection conditions and mixture distribution. The current research employs the laser induced breakdown spectroscopy as a method to measure the hydrogen concentration distribution in the direct injection stratified charge. Measurement of instantaneous local equivalence ratio by the method clears the characteristics of mixture formation in hydrogen direct injection stratified charge. This research also tries to actively control the mixture distribution using a split fuel injection. (author)
Displacement of Pile-Reinforced Slopes with a Weak Layer Subjected to Seismic Loads
Directory of Open Access Journals (Sweden)
Haizuo Zhou
2016-01-01
Full Text Available The presence of a weak layer in a slope requires special attention because it has a negative impact on slope stability. However, limited insight into the seismic stability of slopes with a weak layer exists. In this study, the seismic stability of a pile-reinforced slope with a weak thin layer is investigated. Based on the limit analysis theory, a translational failure mechanism for an earth slope is developed. The rotational rigid blocks in the previous rotational-translational failure mechanism are replaced by continuous deformation regions, which consist of a sequence of n rigid triangles. The predicted static factor of safety and collapse mechanism in two typical examples of slopes with a weak layer compare well with the results obtained from the available literature and by using the Discontinuity Layout Optimization (DLO technique. The lateral forces provided by the stabilizing piles are evaluated using the theory of plastic deformation. An analytical solution for estimating the critical yield acceleration coefficient for the pile-reinforced slopes is derived. Based on the proposed translational failure mechanism and the corresponding critical yield acceleration coefficient, Newmark’s analytical procedure is employed to evaluate the cumulative displacement. Considering different real earthquake acceleration records as input motion, the effect of stabilizing piles and varying the spacing of piles on the cumulative displacement of slopes with a weak layer is investigated.
The Quasinormal Modes of Weakly Charged Kerr-Newman Spacetimes
Mark, Zachary; Zimmerman, Aaron; Chen, Yanbei
2014-01-01
The resonant mode spectrum of the Kerr-Newman spacetime is presently unknown. These modes, called the quasinormal modes, play a central role in determining the stability of Kerr-Newman black holes and their response to perturbations. We present a new formalism, generalized from time-independent perturbation theory in quantum mechanics, for calculating the quasinormal mode frequencies of weakly charged Kerr-Newman spacetimes of arbitrary spin. Our method makes use of an original technique for applying perturbation theory to zeroth-order solutions that are not square- integrable, and it can be applied to other problems in theoretical physics. The new formalism reveals no unstable modes, which together with previous results in the slow-rotation limit strongly indicates the modal stability of the Kerr-Newman spacetime. Our techniques and results are of interest in the areas of holographic duality, foundational problems in General Relativity, and possibly in astrophysical systems.
Muon motion in pure and weakly doped aluminium
Niinikoski, T O; Karlsson, E; Kehr, K W; Norlin, L O; Richter, D; Welter, J M
1981-01-01
The authors have studied the diffusion and localization of positive muons in pure and weakly doped aluminium, in the temperature range 30 mK-100K, by measuring the damping parameter of the muon spin rotation ( mu SR) signal. In this paper they discuss some of their recent results and draw the following conclusions: i) in pure Al, positive muons are delocalized in band states (coherent motion); ii) in Al doped with 5-70 ppm Mn, the temperature, concentration and field dependences of the damping parameter suggest diffusion or capture limited trapping to octahedral interstitial sites in the aluminium lattice below 1K; iii) above 2K a two-state diffusion-trapping model explains well the peak in the damping parameter, which appears at 15-50K for the dopants Mn, Mg, Li and Ag so far studied. (11 refs).
Strange attractors in weakly turbulent Couette-Taylor flow
Brandstater, A.; Swinney, Harry L.
1987-01-01
An experiment is conducted on the transition from quasi-periodic to weakly turbulent flow of a fluid contained between concentric cylinders with the inner cylinder rotating and the outer cylinder at rest. Power spectra, phase-space portraits, and circle maps obtained from velocity time-series data indicate that the nonperiodic behavior observed is deterministic, that is, it is described by strange attractors. Various problems that arise in computing the dimension of strange attractors constructed from experimental data are discussed and it is shown that these problems impose severe requirements on the quantity and accuracy of data necessary for determining dimensions greater than about 5. In the present experiment the attractor dimension increases from 2 at the onset of turbulence to about 4 at a Reynolds number 50-percent above the onset of turbulence.
Fugel, Hans-Joerg; Nuijten, Mark; Postma, Maarten
2016-01-01
RATIONALE: Stratified Medicine (SM) is becoming a natural result of advances in biomedical science and a promising path for the innovation-based biopharmaceutical industry to create new investment opportunities. While the use of biomarkers to improve R&D efficiency and productivity is very much
Models of ash-laden intrusions in a stratified atmosphere
Hogg, Andrew; Johnson, Chris; Sparks, Steve; Huppert, Herbert; Woodhouse, Mark; Phillips, Jeremy
2013-04-01
Recent volcanic eruptions and the associated dispersion of ash through the atmosphere have led to widespread closures of airspace, for example the 2010 eruption of Eyjafjallajokull and 2011 eruption of Puyehue-Cordón Caulle. These episodes bring into sharp focus the need to predict quantitatively the transport and deposition of fine ash and in particular, its interaction with atmospheric wind. Many models of this process are based upon capturing the physics of advection with the wind, turbulence-induced diffusion and gravitational settling. Buoyancy-induced processes, associated with the density of the ash cloud and the background stratification of the atmosphere, are neglected and it is this issue that we address in this contribution. In particular, we suggest that the buoyancy-induced motion may account for the relatively thin distal ash layers that have been observed in the atmosphere and their relatively weak cross-wind spreading. We formulate a new model for buoyancy-driven spreading in the atmosphere in which we treat the evolving ash layer as relatively shallow so that its motion is predominantly horizontal and the pressure locally hydrostatic. The motion is driven by horizontal pressure gradients along with interfacial drag between the flowing ash layer and the surrounding atmosphere. Ash-laden fluid is delivered to this intrusion from a plume source and has risen through the atmosphere to its height of neutral buoyancy. The ash particles are then transported horizontally by the intrusion and progressively settle out of it to sediment through the atmosphere and form the deposit on the ground. This model is integrated numerically and analysed asymptotically in various regimes, including scenarios in which the atmosphere is quiescent and in which there is a sustained wind. The results yield predictions for the variation of the thickness of the intrusion with distance from the source and for how the concentration of ash is reduced due to settling. They
Fixed points of occasionally weakly biased mappings
Directory of Open Access Journals (Sweden)
Y. Mahendra Singh, M. R. Singh
2012-09-01
Full Text Available Common fixed point results due to Pant et al. [Pant et al., Weak reciprocal continuity and fixed point theorems, Ann Univ Ferrara, 57(1, 181-190 (2011] are extended to a class of non commuting operators called occasionally weakly biased pair[ N. Hussain, M. A. Khamsi A. Latif, Commonfixed points for JH-operators and occasionally weakly biased pairs under relaxed conditions, Nonlinear Analysis, 74, 2133-2140 (2011]. We also provideillustrative examples to justify the improvements. Abstract. Common fixed point results due to Pant et al. [Pant et al., Weakreciprocal continuity and fixed point theorems, Ann Univ Ferrara, 57(1, 181-190 (2011] are extended to a class of non commuting operators called occasionally weakly biased pair[ N. Hussain, M. A. Khamsi A. Latif, Common fixed points for JH-operators and occasionally weakly biased pairs under relaxed conditions, Nonlinear Analysis, 74, 2133-2140 (2011]. We also provide illustrative examples to justify the improvements.
Institute of Scientific and Technical Information of China (English)
Munir AHMED; Fang LI
2008-01-01
In this paper, we define the notion of self-dual graded weak Hopf algebra and self-dual semilattice graded weak Hopf algebra. We give characterization of finite-dimensional such algebras when they are in structually simple forms in the sense of E. L. Green and E. N. Morcos. We also give the definition of self-dual weak Hopf quiver and apply these types of quivers to classify the finite-dimensional self-dual semilattice graded weak Hopf algebras. Finally, we prove partially the conjecture given by N. Andruskiewitsch and H.-J. Schneider in the case of finite-dimensional pointed semilattice graded weak Hopf algebra H when grH is self-dual.
Atomic homodyne detection of weak atomic transitions.
Gunawardena, Mevan; Elliott, D S
2007-01-26
We have developed a two-color, two-pathway coherent control technique to detect and measure weak optical transitions in atoms by coherently beating the transition amplitude for the weak transition with that of a much stronger transition. We demonstrate the technique in atomic cesium, exciting the 6s(2)S(1/2) --> 8s(2)S(1/2) transition via a strong two-photon transition and a weak controllable Stark-induced transition. We discuss the enhancement in the signal-to-noise ratio for this measurement technique over that of direct detection of the weak transition rate, and project future refinements that may further improve its sensitivity and application to the measurement of other weak atomic interactions.
Wave-driven Rotation in Supersonically Rotating Mirrors
Energy Technology Data Exchange (ETDEWEB)
A. Fetterman and N.J. Fisch
2010-02-15
Supersonic rotation in mirrors may be produced by radio frequency waves. The waves produce coupled diffusion in ion kinetic and potential energy. A population inversion along the diffusion path then produces rotation. Waves may be designed to exploit a natural kinetic energy source or may provide the rotation energy on their own. Centrifugal traps for fusion and isotope separation may benefit from this wave-driven rotation.
Hydromagnetic quasi-geostrophic modes in rapidly rotating planetary cores
DEFF Research Database (Denmark)
Canet, E.; Finlay, Chris; Fournier, A.
2014-01-01
The core of a terrestrial-type planet consists of a spherical shell of rapidly rotating, electrically conducting, fluid. Such a body supports two distinct classes of quasi-geostrophic (QG) eigenmodes: fast, primarily hydrodynamic, inertial modes with period related to the rotation time scale......, or shorter than, their oscillation time scale.Based on our analysis, we expect Mercury to be in a regime where the slow magnetic modes are of quasi-free decay type. Earth and possibly Ganymede, with their larger Elsasser numbers, may possess slow modes that are in the transition regime of weak diffusion...
Flat rotation curves using scalar-tensor theories
Energy Technology Data Exchange (ETDEWEB)
Cervantes-Cota, Jorge L [Depto de Fisica, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 D.F. (Mexico); RodrIguez-Meza, M A [Depto de Fisica, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 D.F. (Mexico); Nunez, Dario [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, A.P. 70-543, 04510 D.F. (Mexico)
2007-11-15
We computed flat rotation curves from scalar-tensor theories in their weak field limit. Our model, by construction, fits a flat rotation profile for velocities of stars. As a result, the form of the scalar field potential and DM distribution in a galaxy are determined. By taking into account the constraints for the fundamental parameters of the theory ({lambda}, {alpha}), it is possible to obtain analytical results for the density profiles. For positive and negative values of {alpha}, the DM matter profile is as cuspy as NFW's.
Observations of the stratorotational instability in rotating concentric cylinders
Ibanez, Ruy; Swinney, Harry L.; Rodenborn, Bruce
2016-09-01
We study the stability of density stratified flow between corotating vertical cylinders with rotation rates ΩoTaylor vortex flow but to a nonaxisymmetric stratorotational instability (SRI). The present work extends the range of Reynolds numbers and buoyancy frequencies [N =√{(-g /ρ )(∂ ρ /∂ z ) }] examined in previous experiments. We present the first experimental results for the axial wavelength λ of the instability as a function of the internal Froude number, Fr=Ωi/N ; λ increases by nearly an order of magnitude over the range of Fr examined. For small outer cylinder Reynolds number, the SRI occurs for inner inner Reynolds number larger than for the axisymmetric Taylor vortex flow (i.e., the SRI is more stable). For somewhat larger outer Reynolds numbers the SRI occurs for smaller inner Reynolds numbers than Taylor vortex flow and even below the Rayleigh stability line for an inviscid fluid. Shalybkov and Rüdiger [Astron. Astrophys. 438, 411 (2005), 10.1051/0004-6361:20042492] proposed that the laminar state of a stably stratified rotating shear flow should be stable for Ωo/Ωi>ri/ro , but we find that this stability criterion is violated for N sufficiently large. At large Reynolds number the primary instability is not the SRI but a previously unreported nonperiodic state that mixes the fluid.
DEFF Research Database (Denmark)
Andersen, Brian Møller; Graser, S.; Hirschfeld, P. J.
2012-01-01
Recent experimental and theoretical studies have highlighted the possible role of an electronic nematic liquid in underdoped cuprate superconductors. We calculate, within a model of d-wave superconductor with Hubbard correlations, the spin susceptibility in the case of a small explicitly broken...
Detection of taste aversion induced by weak unconditioned stimluli such as rotation
Directory of Open Access Journals (Sweden)
A. Maldonado
2001-01-01
Full Text Available El objetivo principal de este estudio fue el desarrollo de un procedimiento conductual suficientemente potente para detectar aversiones inducidas en un único ensayo por estímulos aversivos débiles, concretamente rotación corporal y dosis bajas de LiCl, en ratas wistar. Dicho procedimiento implica el uso de una prueba de elección entre estímulos con diferentes preferencias previas. El experimento 1a demostró que utilizando una solución de café descafeinado y otra de vinagre de sidra, la aversión adquirida a la solución preferida (café mediante rotación corporal sólo aparece en una prueba de elección posterior entre ambos estímulos, cuando se anula la neofobia al estímulo menos preferido (vinagre. Una única preexposición antes de la prueba de elección, es suficiente para anular el efecto de neofobia a dicho sabor (experimento 1b. En el experimento 2 el mismo procedimiento permitió detectar consistentemente aversiones inducidas por inyecciones intraperitoneales (i.p. de cloruro de litio (LiCl cuando se aplican dosis reducidas (0.2%p.c., peso corporal, 0.15Molar. La importancia de este procedimiento reside en que permite un mejor estudio de los procesos psicobiológicos implicados en el aprendizaje aversivo gustativo y por ello se propone como una herramienta comportamental especialmente sensible para la detección de aversiones inducidas por estímulos incondicionados débiles de distinta naturaleza.
Rotator Cuff Injuries - Multiple Languages
... Are Here: Home → Multiple Languages → All Health Topics → Rotator Cuff Injuries URL of this page: https://medlineplus.gov/ ... V W XYZ List of All Topics All Rotator Cuff Injuries - Multiple Languages To use the sharing features ...
Feireisl, Eduard; Novotny, Antonin
2011-01-01
We introduce the notion of relative entropy for the weak solutions of the compressible Navier-Stokes system. We show that any finite energy weak solution satisfies a relative entropy inequality for any pair of sufficiently smooth test functions. As a corollary we establish weak-strong uniqueness principle for the compressible Navier-Stokes system.
Directory of Open Access Journals (Sweden)
S. Wittig
1998-01-01
Full Text Available Cooling of high speed rotating components is a typical situation found in turbomachinery as well as in automobile engines. Accurate knowledge of discharge coefficients and heat transfer of related components is essential for the high performance of the whole engine. This can be achieved by minimized cooling air flows and avoidance of hot spots. In high speed rotating clutches for example aerodynamic investigations improving heat transfer have not been considered in the past. Advanced concepts of modern plate design try to reduce thermal loads by convective cooling methods. Therefore, secondary cooling air flows have to be enhanced by an appropriate design of the rotor stator system with orifices. CFD modelling is used to improve the basic understanding of the flow field in typical geometries used in these systems.
DEFF Research Database (Denmark)
Rasmusson, Allan
2009-01-01
is obeyed by randomizing the orientation of the virtual probe itself within the thick section. Overall, the benefit is that positional information is kept for any block and section of the specimen. As the Spatial Rotator is a 3D probe, data must be gathered from sections thicker than 25 micro meters to form......The inherent demand for unbiasedness for some stereological estimators imposes a demand of not only positional uniform randomness but also isotropic randomness, i.e. directional uniform randomness. In order to comply with isotropy, one must perform a random rotation of the object of interest before...... it is embedded and sectioned. This has the unfortunate side effect that all information about positioning within the object is lost for blocks and sections. For complex tissue, like the mammalian brain, this information is of utmost importance to ensure measurements are performed in the correct region...
Earth rotation and geodynamics
Bogusz, Janusz; Brzezinski, Aleksander; Kosek, Wieslaw; Nastula, Jolanta
2015-12-01
This paper presents the summary of research activities carried out in Poland in 2011-2014 in the field of Earth rotation and geodynamics by several Polish research institutions. It contains a summary of works on Earth rotation, including evaluation and prediction of its parameters and analysis of the related excitation data as well as research on associated geodynamic phenomena such as geocentre motion, global sea level change and hydrological processes. The second part of the paper deals with monitoring of geodynamic phenomena. It contains analysis of geodynamic networks of local, and regional scale using space (GNSS and SLR) techniques, Earth tides monitoring with gravimeters and water-tube hydrostatic clinometer, and the determination of secular variation of the Earth' magnetic field.
Rotational spectrum of tryptophan
Energy Technology Data Exchange (ETDEWEB)
Sanz, M. Eugenia, E-mail: maria.sanz@kcl.ac.uk; Cabezas, Carlos, E-mail: ccabezas@qf.uva.es; Mata, Santiago, E-mail: santiago.mata@uva.es; Alonso, Josè L., E-mail: jlalonso@qf.uva.es [Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia, Unidad Asociada CSIC, Parque Científico Uva, Universidad de Valladolid, 47011 Valladolid (Spain)
2014-05-28
The rotational spectrum of the natural amino acid tryptophan has been observed for the first time using a combination of laser ablation, molecular beams, and Fourier transform microwave spectroscopy. Independent analysis of the rotational spectra of individual conformers has conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The analysis of the {sup 14}N nuclear quadrupole coupling constants is of particular significance since it allows discrimination between structures, thus providing structural information on the orientation of the amino group. Both observed conformers are stabilized by an O–H···N hydrogen bond in the side chain and a N–H···π interaction forming a chain that reinforce the strength of hydrogen bonds through cooperative effects.
Rotational Spectrum of Tryptophan
Sanz, M. Eugenia; Cabezas, Carlos; Mata, Santiago; Alonso, José L.
2014-06-01
The rotational spectrum of the natural amino acid tryptophan has been observed using a recently constructed LA-MB-FTMW spectrometer, specifically designed to optimize the detection of heavier molecules at a lower frequency range. Independent analyses of the rotational spectra of individual conformers have conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The experimental values of the 14N nuclear quadrupole coupling constants have been found capital in the discrimination of the conformers. Both observed conformers are stabilized by a O-H\\cdotsN hydrogen bond in the side chain and a N-H\\cdotsπ interaction forming a chain that reinforces the strength of hydrogen bonds through cooperative effects.
A Translational Polarization Rotator
Chuss, David T; Pisano, Giampaolo; Ackiss, Sheridan; U-Yen, Kongpop; Ng, Ming wah
2012-01-01
We explore a free-space polarization modulator in which a variable phase introduction between right- and left-handed circular polarization components is used to rotate the linear polarization of the outgoing beam relative to that of the incoming beam. In this device, the polarization states are separated by a circular polarizer that consists of a quarter-wave plate in combination with a wire grid. A movable mirror is positioned behind and parallel to the circular polarizer. As the polarizer-mirror distance is separated, an incident linear polarization will be rotated through an angle that is proportional to the introduced phase delay. We demonstrate a prototype device that modulates Stokes Q and U over a 20% bandwidth.