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Sample records for rayleigh number ra

  1. Penetrative convection at high Rayleigh numbers

    Science.gov (United States)

    Toppaladoddi, Srikanth; Wettlaufer, John S.

    2018-04-01

    We study penetrative convection of a fluid confined between two horizontal plates, the temperatures of which are such that a temperature of maximum density lies between them. The range of Rayleigh numbers studied is Ra=[0.01 ,4 ]106,108 and the Prandtl numbers are Pr=1 and 11.6. An evolution equation for the growth of the convecting region is obtained through an integral energy balance. We identify a new nondimensional parameter, Λ , which is the ratio of temperature difference between the stable and unstable regions of the flow; larger values of Λ denote increased stability of the upper stable layer. We study the effects of Λ on the flow field using well-resolved lattice Boltzmann simulations and show that the characteristics of the flow depend sensitively upon it. For the range Λ = , we find that for a fixed Ra the Nusselt number, Nu, increases with decreasing Λ . We also investigate the effects of Λ on the vertical variation of convective heat flux and the Brunt-Väisälä frequency. Our results clearly indicate that in the limit Λ →0 the problem reduces to that of the classical Rayleigh-Bénard convection.

  2. Rotating Rayleigh-Bénard convection at low Prandtl number

    Science.gov (United States)

    Aguirre Guzman, Andres; Ostilla-Monico, Rodolfo; Clercx, Herman; Kunnen, Rudie

    2017-11-01

    Most geo- and astrophysical convective flows are too remote or too complex for direct measurements of the physical quantities involved, and thus a reduced framework with the main physical constituents is beneficial. This approach is given by the problem of rotating Rayleigh-Bénard convection (RRBC). For large-scale systems, the governing parameters of RRBC take extreme values, leading to the geostrophic turbulent regime. We perform Direct Numerical Simulations to investigate the transition to this regime at low Prandtl number (Pr). In low- Pr fluids, thermal diffusivity dominates over momentum diffusivity; we use Pr = 0.1 , relevant to liquid metals. In particular, we study the convective heat transfer (Nusselt number Nu) as a function of rotation (assessed by the Ekman number Ek). The strength of the buoyant forcing (Rayleigh number Ra) is Ra = 1 ×1010 to ensure turbulent convection. Varying Ek , we observe a change of the power-law scaling Nu Ekβ that suggests a transition to geostrophic turbulence, which is likely to occur at Ek = 9 ×10-7 . The thermal boundary layer thickness, however, may suggest a transition at lower Ekman numbers, indicating that perhaps not all statistical quantities show a transitional behaviour at the same Ek .

  3. Turbulent boundary layer in high Rayleigh number convection in air.

    Science.gov (United States)

    du Puits, Ronald; Li, Ling; Resagk, Christian; Thess, André; Willert, Christian

    2014-03-28

    Flow visualizations and particle image velocimetry measurements in the boundary layer of a Rayleigh-Bénard experiment are presented for the Rayleigh number Ra=1.4×1010. Our visualizations indicate that the appearance of the flow structures is similar to ordinary (isothermal) turbulent boundary layers. Our particle image velocimetry measurements show that vorticity with both positive and negative sign is generated and that the smallest flow structures are 1 order of magnitude smaller than the boundary layer thickness. Additional local measurements using laser Doppler velocimetry yield turbulence intensities up to I=0.4 as in turbulent atmospheric boundary layers. From our observations, we conclude that the convective boundary layer becomes turbulent locally and temporarily although its Reynolds number Re≈200 is considerably smaller than the value 420 underlying existing phenomenological theories. We think that, in turbulent Rayleigh-Bénard convection, the transition of the boundary layer towards turbulence depends on subtle details of the flow field and is therefore not universal.

  4. Ultimate regime of high Rayleigh number convection in a porous medium.

    Science.gov (United States)

    Hewitt, Duncan R; Neufeld, Jerome A; Lister, John R

    2012-06-01

    Well-resolved direct numerical simulations of 2D Rayleigh-Bénard convection in a porous medium are presented for Rayleigh numbers Ra≤4×10(4) which reveal that, contrary to previous indications, the linear classical scaling for the Nusselt number, Nu~Ra, is attained asymptotically. The flow dynamics are analyzed, and the interior of the vigorously convecting system is shown to be increasingly well described as Ra→∞ by a simple columnar "heat-exchanger" model with a single horizontal wave number k and a linear background temperature field. The numerical results are approximately fitted by k~Ra(0.4).

  5. Rotating thermal convection at very large Rayleigh numbers

    Science.gov (United States)

    Weiss, Stephan; van Gils, Dennis; Ahlers, Guenter; Bodenschatz, Eberhard

    2016-11-01

    The large scale thermal convection systems in geo- and astrophysics are usually influenced by Coriolis forces caused by the rotation of their celestial bodies. To better understand the influence of rotation on the convective flow field and the heat transport at these conditions, we study Rayleigh-Bénard convection, using pressurized sulfur hexaflouride (SF6) at up to 19 bars in a cylinder of diameter D=1.12 m and a height of L=2.24 m. The gas is heated from below and cooled from above and the convection cell sits on a rotating table inside a large pressure vessel (the "Uboot of Göttingen"). With this setup Rayleigh numbers of up to Ra =1015 can be reached, while Ekman numbers as low as Ek =10-8 are possible. The Prandtl number in these experiment is kept constant at Pr = 0 . 8 . We report on heat flux measurements (expressed by the Nusselt number Nu) as well as measurements from more than 150 temperature probes inside the flow. We thank the Deutsche Forschungsgemeinschaft (DFG) for financial support through SFB963: "Astrophysical Flow Instabilities and Turbulence". The work of GA was supported in part by the US National Science Foundation through Grant DMR11-58514.

  6. Turbulent convection experiment at high Rayleigh number to support CAP1400 IVR strategy

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Li, E-mail: mali@snptrd.com [State Nuclear Hua Qing(Beijing) Nuclear Power Technology R& D Centre Co., Ltd, Building A, State Nuclear Power Research Institute, Future Science & Technology Park, Changping Dist., Beijing 102209 (China); Li, Jing, E-mail: lijing@snptrd.com [State Nuclear Hua Qing(Beijing) Nuclear Power Technology R& D Centre Co., Ltd, Building A, State Nuclear Power Research Institute, Future Science & Technology Park, Changping Dist., Beijing 102209 (China); Ji, Shui, E-mail: jishui@snptrd.com [State Nuclear Hua Qing(Beijing) Nuclear Power Technology R& D Centre Co., Ltd, Building A, State Nuclear Power Research Institute, Future Science & Technology Park, Changping Dist., Beijing 102209 (China); Chang, Huajian, E-mail: changhuajian@snptrd.com [State Nuclear Hua Qing(Beijing) Nuclear Power Technology R& D Centre Co., Ltd, Building A, State Nuclear Power Research Institute, Future Science & Technology Park, Changping Dist., Beijing 102209 (China); Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China)

    2015-10-15

    Highlights: • The facility reached high Ra number at 10{sup 12} of CAP1400 working condition. • The fitting formula Nu = 0.085 × Ra{sup 0.315} was established to calculate the heat flux in the metal layer at high Ra for the CAP1400. • The coupling method can accurately and safely predict the heat flow distribution of metal layer in high Ra number conditions. • The experiment results will predict the relationship between axial and radial heat transfer well. - Abstract: The characteristics of the heat transfer and the calculation of heat flux in metal layer are both the critical problems for in-vessel retention (IVR) strategy. Turbulent convection occurs in the metal layer when the Rayleigh number (Ra) becomes sufficient high. The Globe–Dropkin (G–D) correlation (Globe and Dropkin, 1959) and Chu–Churchill (C–C) correlation (Churchill and Chu, 1975) have been widely used to calculate the heat flux in the metal layer, where the valid range of the Ra is from 1.5 × 10{sup 5} to 6.8 × 10{sup 8} in G–D correlation and less than 10{sup 12} in C–C correlation. However, with the increase of reactor power, both the Rayleigh number and the rate of heat transfer below the bottom of metal layer of the molten pool will increase, and in this case the Rayleigh number even can reach 10{sup 11} for the China Advanced Passive Plant CAP1400. Accordingly, the G–D correlation is not suitable for the CAP1400. Therefore, our experiment purposes are to establish the appropriate correlation at high Ra for the CAP1400 and predict the axial and radial distribution of the heat transfer in the metal layer with the heat transfer behavior of metal layer experiment (HELM) facility. The experiments are divided into two parts. Each part concerns 39 runs and 47 experimental conditions. Its corresponding results are obtained at middle Prandtl number (Pr = 7 for water) and the Nusselt number is found to be proportional to Ra{sup 0.315} in the range 3.93 × 10{sup 8} < Ra < 3.57

  7. Turbulent convection experiment at high Rayleigh number to support CAP1400 IVR strategy

    International Nuclear Information System (INIS)

    Ma, Li; Li, Jing; Ji, Shui; Chang, Huajian

    2015-01-01

    Highlights: • The facility reached high Ra number at 10 12 of CAP1400 working condition. • The fitting formula Nu = 0.085 × Ra 0.315 was established to calculate the heat flux in the metal layer at high Ra for the CAP1400. • The coupling method can accurately and safely predict the heat flow distribution of metal layer in high Ra number conditions. • The experiment results will predict the relationship between axial and radial heat transfer well. - Abstract: The characteristics of the heat transfer and the calculation of heat flux in metal layer are both the critical problems for in-vessel retention (IVR) strategy. Turbulent convection occurs in the metal layer when the Rayleigh number (Ra) becomes sufficient high. The Globe–Dropkin (G–D) correlation (Globe and Dropkin, 1959) and Chu–Churchill (C–C) correlation (Churchill and Chu, 1975) have been widely used to calculate the heat flux in the metal layer, where the valid range of the Ra is from 1.5 × 10 5 to 6.8 × 10 8 in G–D correlation and less than 10 12 in C–C correlation. However, with the increase of reactor power, both the Rayleigh number and the rate of heat transfer below the bottom of metal layer of the molten pool will increase, and in this case the Rayleigh number even can reach 10 11 for the China Advanced Passive Plant CAP1400. Accordingly, the G–D correlation is not suitable for the CAP1400. Therefore, our experiment purposes are to establish the appropriate correlation at high Ra for the CAP1400 and predict the axial and radial distribution of the heat transfer in the metal layer with the heat transfer behavior of metal layer experiment (HELM) facility. The experiments are divided into two parts. Each part concerns 39 runs and 47 experimental conditions. Its corresponding results are obtained at middle Prandtl number (Pr = 7 for water) and the Nusselt number is found to be proportional to Ra 0.315 in the range 3.93 × 10 8 < Ra < 3.57 × 10 12 . Furthermore, the experiment

  8. Nusselt number and bulk temperature in turbulent Rayleigh-Bénard convection

    Science.gov (United States)

    Bodenschatz, Eberhard; Weiss, Stephan; Shishkina, Olga; International CollaborationTurbulence Research Collaboration

    2017-11-01

    We present an algorithm to calculate the Nusselt number (Nu) in measurements of the heat transport in turbulent Rayleigh-Bénard convection under general non-Oberbeck-Boussinesq (NOB) conditions. We further critically analyze the different ways to evaluate the dependences of Nu over the Rayleigh number (Ra) and show the sensitivity of these dependences to the reference temperatures in the bulk, top and bottom boundary layers (BLs). Finally we propose a method to predict the bulk temperature and a way to calculate the reference temperatures of the top and bottom BLs and validate them against the Göttingen measurements. The work is supported by the Max Planck Society and the Deutsche Forschungsgemeinschaft (DFG) under the Grant Sh 405/4 - Heisenberg fellowship.

  9. Solute redistribution and Rayleigh number in the mushy zone during directional solidifi cation of Inconel 718

    Directory of Open Access Journals (Sweden)

    Wang Ling

    2009-08-01

    Full Text Available The interdendritic segregation along the mushy zone of directionally solidifi ed superalloy Inconel 718 has been measured by scanning electron microscope (SEM and energy dispersion analysis spectrometry (EDAXtechniques and the corresponding liquid composition profile was presented. The liquid density and Rayleigh number (Ra profi les along the mushy zone were calculated as well. It was found that the liquid density difference increased from top to bottom in the mushy zone and there was no density inversion due to the segregation of Nb and Mo. However carbide formation in the freezing range and the preferred angle of the orientated dendrite array could prompt the fl uid fl ow in the mushy zone although there was no liquid density inversion. The largest relative Rayleigh number appeared at 1,326 篊 for Inconel 718 where the fl uid fl ow most easily occurred.

  10. Plume structure in high-Rayleigh-number convection

    Science.gov (United States)

    Puthenveettil, Baburaj A.; Arakeri, Jaywant H.

    2005-10-01

    Near-wall structures in turbulent natural convection at Rayleigh numbers of 10^{10} to 10^{11} at A Schmidt number of 602 are visualized by a new method of driving the convection across a fine membrane using concentration differences of sodium chloride. The visualizations show the near-wall flow to consist of sheet plumes. A wide variety of large-scale flow cells, scaling with the cross-section dimension, are observed. Multiple large-scale flow cells are seen at aspect ratio (AR)= 0.65, while only a single circulation cell is detected at AR= 0.435. The cells (or the mean wind) are driven by plumes coming together to form columns of rising lighter fluid. The wind in turn aligns the sheet plumes along the direction of shear. the mean wind direction is seen to change with time. The near-wall dynamics show plumes initiated at points, which elongate to form sheets and then merge. Increase in rayleigh number results in a larger number of closely and regularly spaced plumes. The plume spacings show a common log normal probability distribution function, independent of the rayleigh number and the aspect ratio. We propose that the near-wall structure is made of laminar natural-convection boundary layers, which become unstable to give rise to sheet plumes, and show that the predictions of a model constructed on this hypothesis match the experiments. Based on these findings, we conclude that in the presence of a mean wind, the local near-wall boundary layers associated with each sheet plume in high-rayleigh-number turbulent natural convection are likely to be laminar mixed convection type.

  11. Rayleigh-Benard Natural Convection Cell Formation and Nusselt number

    International Nuclear Information System (INIS)

    Moon, Je Young; Chung, Bum Jin

    2013-01-01

    The experimental results lie within the predictions of the existing heat transfer correlations for the Rayleigh-Benard natural convections even though the material properties were different. For shorter separation distances, the heat transfers enhance due to the active interaction between heated and cooled plumes. For a step temperature difference, the time dependent Nusselt number variations were investigated. Both experimental and numerical results showed that with time the Nusselt number decreases monotonically to a minimum point presenting the onset of convection. As the hot and cold plumes increase and convey the heat to the other plates, the Nusselt number increases to the local maximum point, presenting the vertical movements of the plumes. Then, the Nusselt number fluctuates with the formation of square cells and larger vortices. This also predicted by the mass transfer experiment. The experiments and calculations show similar trend but the timings were different. These discrepancies are caused by the disturbances inherent in both systems. The molten pool is formed in a hypothetical severe accident condition at the lower head of reactor vessel and is stratified into two layers by the density difference: an upper metallic layer and a lower oxide pool. Rayleigh-Benard natural convection occurs in the metallic layer of relocated molten pool. This study aimed at the investigation of the time-dependent cell formation and Nusselt number variation in Rayleigh-Benard natural convection. Time dependent variation of Nusselt number was also measured experimentally and analyzed numerically to investigate the relationship between the cell formation and Nusselt number. Based on the analogy, heat transfer experiments were replaced by mass transfer experiments using a sulfuric acid-copper sulfate (H 2 SO 4 -CuSO 4 ) electroplating system. Numerical analysis using the commercial CFD program FLUENT 6.3 were carried out with the same material properties and heating conditions

  12. Transitional boundary layer in low-Prandtl-number convection at high Rayleigh number

    Science.gov (United States)

    Schumacher, Joerg; Bandaru, Vinodh; Pandey, Ambrish; Scheel, Janet

    2016-11-01

    The boundary layer structure of the velocity and temperature fields in turbulent Rayleigh-Bénard flows in closed cylindrical cells of unit aspect ratio is revisited from a transitional and turbulent viscous boundary layer perspective. When the Rayleigh number is large enough the boundary layer dynamics at the bottom and top plates can be separated into an impact region of downwelling plumes, an ejection region of upwelling plumes and an interior region (away from side walls) that is dominated by a shear flow of varying orientation. This interior plate region is compared here to classical wall-bounded shear flows. The working fluid is liquid mercury or liquid gallium at a Prandtl number of Pr = 0 . 021 for a range of Rayleigh numbers of 3 ×105 Deutsche Forschungsgemeinschaft.

  13. Convection in an ideal gas at high Rayleigh numbers.

    Science.gov (United States)

    Tilgner, A

    2011-08-01

    Numerical simulations of convection in a layer filled with ideal gas are presented. The control parameters are chosen such that there is a significant variation of density of the gas in going from the bottom to the top of the layer. The relations between the Rayleigh, Peclet, and Nusselt numbers depend on the density stratification. It is proposed to use a data reduction which accounts for the variable density by introducing into the scaling laws an effective density. The relevant density is the geometric mean of the maximum and minimum densities in the layer. A good fit to the data is then obtained with power laws with the same exponent as for fluids in the Boussinesq limit. Two relations connect the top and bottom boundary layers: The kinetic energy densities computed from free fall velocities are equal at the top and bottom, and the products of free fall velocities and maximum horizontal velocities are equal for both boundaries.

  14. Turbulent thermal convection at high Rayleigh numbers for a Boussinesq fluid of constant Prandtl number

    International Nuclear Information System (INIS)

    Amati, G.; Koal, K.; Massaioli, F.; Sreenivasan, K.R.; Verzicco, R.

    2006-12-01

    The results from direct numerical simulations of turbulent Boussinesq convection are briefly presented. The flow is computed for a cylindrical cell of aspect ratio 1/2 in order to compare with the results from recent experiments. The results span eight decades of Ra from 2x10 6 to 2x10 14 and form the baseline data for a strictly Boussinesq fluid of constant Prandtl number (Pr=0.7). A conclusion is that the Nusselt number varies nearly as the 1/3 power of Ra for about four decades towards the upper end of the Ra range covered. (author)

  15. A study of the required Rayleigh number to sustain dynamo with various inner core radius

    Science.gov (United States)

    Nishida, Y.; Katoh, Y.; Matsui, H.; Kumamoto, A.

    2017-12-01

    It is widely accepted that the geomagnetic field is sustained by thermal and compositional driven convections of a liquid iron alloy in the outer core. The generation process of the geomagnetic field has been studied by a number of MHD dynamo simulations. Recent studies of the ratio of the Earth's core evolution suggest that the inner solid core radius ri to the outer liquid core radius ro changed from ri/ro = 0 to 0.35 during the last one billion years. There are some studies of dynamo in the early Earth with smaller inner core than the present. Heimpel et al. (2005) revealed the Rayleigh number Ra of the onset of dynamo process as a function of ri/ro from simulation, while paleomagnetic observation shows that the geomagnetic field has been sustained for 3.5 billion years. While Heimpel and Evans (2013) studied dynamo processes taking into account the thermal history of the Earth's interior, there were few cases corresponding to the early Earth. Driscoll (2016) performed a series of dynamo based on a thermal evolution model. Despite a number of dynamo simulations, dynamo process occurring in the interior of the early Earth has not been fully understood because the magnetic Prandtl numbers in these simulations are much larger than that for the actual outer core.In the present study, we performed thermally driven dynamo simulations with different aspect ratio ri/ro = 0.15, 0.25 and 0.35 to evaluate the critical Ra for the thermal convection and required Ra to maintain the dynamo. For this purpose, we performed simulations with various Ra and fixed the other control parameters such as the Ekman, Prandtl, and magnetic Prandtl numbers. For the initial condition and boundary conditions, we followed the dynamo benchmark case 1 by Christensen et al. (2001). The results show that the critical Ra increases with the smaller aspect ratio ri/ro. It is confirmed that larger amplitude of buoyancy is required in the smaller inner core to maintain dynamo.

  16. Thermal convection at low Rayleigh number from concentrated sources in porous media

    International Nuclear Information System (INIS)

    Hickox, C.E.

    1980-01-01

    A simple mathematical theory is proposed for the analysis of natural convective motion, at low Rayleigh number, from a concentrated source of heat in a fluid-saturated porous medium. The theory consists of retaining only the leading terms of series expansions of the dependent variables in terms of the Rayleigh number, is thus linear, and is valid only in the limit of small Rayleigh number. Based on fundamental results for a variety of isolated sources, superposition is used to provide solutions for situations of practical interest. Special emphasis is given to the analysis of sub-seabed disposal of nuclear waste. 8 figures

  17. Efficient testing of the homogeneity, scale parameters and number of components in the Rayleigh mixture

    International Nuclear Information System (INIS)

    Stehlik, M.; Ososkov, G.A.

    2003-01-01

    The statistical problem to expand the experimental distribution of transverse momenta into Rayleigh distribution is considered. A high-efficient testing procedure for testing the hypothesis of the homogeneity of the observed measurements which is optimal in the sense of Bahadur is constructed. The exact likelihood ratio (LR) test of the scale parameter of the Rayleigh distribution is proposed for cases when the hypothesis of homogeneity holds. Otherwise the efficient procedure for testing the number of components in the mixture is also proposed

  18. DNS of buoyancy-driven flows and Lagrangian particle tracking in a square cavity at high Rayleigh numbers

    International Nuclear Information System (INIS)

    Puragliesi, R.; Dehbi, A.; Leriche, E.; Soldati, A.; Deville, M.O.

    2011-01-01

    Highlights: → 2D study of micro-size particle depletion driven by chaotic natural convective flows in square domains. → Description of velocity and temperature first and second moments with changing in the Rayleigh number. → Strong decoupling between the turbulent kinetic energy and the dissipation rate. → Particle recirculation sustained by the vertical hot boundary layer. → Deposition mostly induced by gravity, thermophoretic and lift forces are negligible. - Abstract: In this work we investigate numerically particle deposition in the buoyancy driven flow of the differentially heated cavity (DHC). We consider two values of the Rayleigh number (Ra = 10 9 , 10 10 ) and three values of the particle diameter (d p = 15, 25, 35 [μm]). We consider the cavity filled with air and particles with the same density of water ρ w = 1000 [kg/m 3 ] (aerosol). We use direct numerical simulations (DNS) for the continuous phase, and we solve transient Navier-Stokes and energy transport equations written in an Eulerian framework, under the Boussinesq approximation, for the viscous incompressible Newtonian fluid with constant Prandtl number (Pr = 0.71). First- and second-order statistics are presented for the continuous phase as well as important quantities like turbulent kinetic energy (TKE) and temperature variance with the associated production and dissipation fields. The TKE production shows different behaviour at the two Rayleigh numbers. The Lagrangian approach has been chosen for the dispersed phase description. The forces taken into account are drag, gravity, buoyancy, lift and thermophoresis. A first incursion in the sedimentation mechanisms is presented. Current results indicate that the largest contribution to particle deposition is caused by gravitational settling, but a strong recirculating zone, which liftoffs and segregates particles, contributes to decrease settling. Deposition takes place mostly at the bottom wall. The influence of lift and thermophoretic

  19. DNS of buoyancy-driven flows and Lagrangian particle tracking in a square cavity at high Rayleigh numbers

    Energy Technology Data Exchange (ETDEWEB)

    Puragliesi, R., E-mail: riccardo.puragliesi@psi.ch [Nuclear Energy and Safety Research Department, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Laboratoire d' Ingenierie Numerique, Ecole Polytechnique Federale de Lausanne, Station 9, CH-1015 Lausanne (Switzerland); Dehbi, A., E-mail: abdel.dehbi@psi.ch [Nuclear Energy and Safety Research Department, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Leriche, E., E-mail: emmanuel.leriche@univ-st-etienne.fr [Universite de Lyon, F-42023 Saint-Etienne, LMFA-UJM St-Etienne, CNRS UMR 5509 Universite de St-Etienne, 23 rue Docteur Paul Michelon, F-42023 Saint-Etienne (France); Soldati, A., E-mail: soldati@uniud.it [Dipartimento di Energetica e Macchine, Universita di Udine, Via delle Scienze 208, IT-33100 Udine (Italy); Deville, M.O., E-mail: michel.deville@epfl.ch [Laboratoire d' Ingenierie Numerique, Ecole Polytechnique Federale de Lausanne, Station 9, CH-1015 Lausanne (Switzerland)

    2011-10-15

    Highlights: > 2D study of micro-size particle depletion driven by chaotic natural convective flows in square domains. > Description of velocity and temperature first and second moments with changing in the Rayleigh number. > Strong decoupling between the turbulent kinetic energy and the dissipation rate. > Particle recirculation sustained by the vertical hot boundary layer. > Deposition mostly induced by gravity, thermophoretic and lift forces are negligible. - Abstract: In this work we investigate numerically particle deposition in the buoyancy driven flow of the differentially heated cavity (DHC). We consider two values of the Rayleigh number (Ra = 10{sup 9}, 10{sup 10}) and three values of the particle diameter (d{sub p} = 15, 25, 35 [{mu}m]). We consider the cavity filled with air and particles with the same density of water {rho}{sub w} = 1000 [kg/m{sup 3}] (aerosol). We use direct numerical simulations (DNS) for the continuous phase, and we solve transient Navier-Stokes and energy transport equations written in an Eulerian framework, under the Boussinesq approximation, for the viscous incompressible Newtonian fluid with constant Prandtl number (Pr = 0.71). First- and second-order statistics are presented for the continuous phase as well as important quantities like turbulent kinetic energy (TKE) and temperature variance with the associated production and dissipation fields. The TKE production shows different behaviour at the two Rayleigh numbers. The Lagrangian approach has been chosen for the dispersed phase description. The forces taken into account are drag, gravity, buoyancy, lift and thermophoresis. A first incursion in the sedimentation mechanisms is presented. Current results indicate that the largest contribution to particle deposition is caused by gravitational settling, but a strong recirculating zone, which liftoffs and segregates particles, contributes to decrease settling. Deposition takes place mostly at the bottom wall. The influence of lift

  20. Rayleigh Number Criterion for Formation of A-Segregates in Steel Castings and Ingots

    DEFF Research Database (Denmark)

    Rad, M. Torabi; Kotas, Petr; Beckermann, C.

    2013-01-01

    A Rayleigh number-based criterion is developed for predicting the formation of A-segregates in steel castings and ingots. The criterion is calibrated using available experimental data for ingots involving 27 different steel compositions. The critical Rayleigh number above which A-segregates can b......, the primary reason for this over-prediction is persumed to be the presence of a central zone of equiaxed grains in the casting sections. A-segregates do not form when the grain structure is equiaxed. © The Minerals, Metals & Materials Society and ASM International 2013...

  1. Prandtl-number Effects in High-Rayleigh-number Spherical Convection

    Science.gov (United States)

    Orvedahl, Ryan J.; Calkins, Michael A.; Featherstone, Nicholas A.; Hindman, Bradley W.

    2018-03-01

    Convection is the predominant mechanism by which energy and angular momentum are transported in the outer portion of the Sun. The resulting overturning motions are also the primary energy source for the solar magnetic field. An accurate solar dynamo model therefore requires a complete description of the convective motions, but these motions remain poorly understood. Studying stellar convection numerically remains challenging; it occurs within a parameter regime that is extreme by computational standards. The fluid properties of the convection zone are characterized in part by the Prandtl number \\Pr = ν/κ, where ν is the kinematic viscosity and κ is the thermal diffusion; in stars, \\Pr is extremely low, \\Pr ≈ 10‑7. The influence of \\Pr on the convective motions at the heart of the dynamo is not well understood since most numerical studies are limited to using \\Pr ≈ 1. We systematically vary \\Pr and the degree of thermal forcing, characterized through a Rayleigh number, to explore its influence on the convective dynamics. For sufficiently large thermal driving, the simulations reach a so-called convective free-fall state where diffusion no longer plays an important role in the interior dynamics. Simulations with a lower \\Pr generate faster convective flows and broader ranges of scales for equivalent levels of thermal forcing. Characteristics of the spectral distribution of the velocity remain largely insensitive to changes in \\Pr . Importantly, we find that \\Pr plays a key role in determining when the free-fall regime is reached by controlling the thickness of the thermal boundary layer.

  2. The multifractal nature of plume structure in high-Rayleigh-number convection

    Science.gov (United States)

    Puthenveettil, Baburaj A.; Ananthakrishna, G.; Arakeri, Jaywant H.

    2005-03-01

    The geometrically different planforms of near-wall plume structure in turbulent natural convection, visualized by driving the convection using concentration differences across a membrane, are shown to have a common multifractal spectrum of singularities for Rayleigh numbers in the range 1010-1011 at Schmidt number of 602. The scaling is seen for a length scale range of 25 and is independent of the Rayleigh number, the flux, the strength and nature of the large-scale flow, and the aspect ratio. Similar scaling is observed for the plume structures obtained in the presence of a weak flow across the membrane. This common non-trivial spatial scaling is proposed to be due to the same underlying generating process for the near-wall plume structures.

  3. Role of Shape and Numbers of Ridges and Valleys in the Insulating Effects of Topography on the Rayleigh Wave Characteristics

    Science.gov (United States)

    Narayan, J. P.; Kumar, Neeraj; Chauhan, Ranu

    2018-03-01

    This research work is inspired by the recently accepted concept that high frequency Rayleigh waves are generated in the epicentral zone of shallow earthquakes. Such high frequency Rayleigh waves with large amplitude may develop much of spatial variability in ground motion which in turn may cause unexpected damage to long-span structures like bridges, underground pipelines, dams, etc., in the hilly regions. Further, it has been reported that topography acts as an insulator for the Rayleigh waves (Ma et al. BSSA 97:2066-2079, 2007). The above mentioned scientific developments stimulated to quantify the role of shape and number of ridges and valleys falling in the path of Rayleigh wave in the insulating effect of topography on the Rayleigh waves. The simulated results reveals very large amplification of the horizontal component of Rayleigh wave near the top of a triangular ridge which may cause intensive landslides under favorable condition. The computed snapshots of the wave-field of Rayleigh wave reveals that the interaction of Rayleigh wave with the topography causes reflection, splitting, and diffraction of Rayleigh wave in the form of body waves which in turn provides the insulating capacity to the topography. Insulating effects of single valley is more than that of single ridge. Further this effect was more in case of elliptical ridge/valley than triangular ridge/valley. The insulating effect of topography was proportional to the frequency of Rayleigh wave and the number of ridges and valleys in the string. The obtained level of insulation effects of topography on the Rayleigh wave (energy of Rayleigh wave reduced to less than 4% after crossing a topography of span 4.5 km) calls for the consideration of role of hills and valleys in seismic hazard prediction, particularly in case of shallow earthquakes.

  4. Turbulent Superstructures in Rayleigh-Bénard convection at different Prandtl number

    Science.gov (United States)

    Schumacher, Jörg; Pandey, Ambrish; Ender, Martin; Westermann, Rüdiger; Scheel, Janet D.

    2017-11-01

    Large-scale patterns of the temperature and velocity field in horizontally extended cells can be considered as turbulent superstructures in Rayleigh-Bénard convection (RBC). These structures are obtained once the turbulent fluctuations are removed by a finite-time average. Their existence has been reported for example in Bailon-Cuba et al.. This large-scale order obeys a strong similarity with the well-studied patterns from the weakly nonlinear regime at lower Rayleigh number in RBC. In the present work we analyze the superstructures of RBC at different Prandtl number for Prandtl values between Pr = 0.005 for liquid sodium and 7 for water. The characteristic evolution time scales, the typical spatial extension of the rolls and the properties of the defects of the resulting superstructure patterns are analyzed. Data are obtained from well-resolved spectral element direct numerical simulations. The work is supported by the Priority Programme SPP 1881 of the Deutsche Forschungsgemeinschaft.

  5. Influence of the Ringwoodite-Perovskite transition on mantle convection in spherical geometry as a function of Clapeyron slope and Rayleigh number

    Directory of Open Access Journals (Sweden)

    M. Wolstencroft

    2011-12-01

    Full Text Available We investigate the influence on mantle convection of the negative Clapeyron slope ringwoodite to perovskite and ferro-periclase mantle phase transition, which is correlated with the seismic discontinuity at 660 km depth. In particular, we focus on understanding the influence of the magnitude of the Clapeyron slope (as measured by the Phase Buoyancy parameter, P and the vigour of convection (as measured by the Rayleigh number, Ra on mantle convection. We have undertaken 76 simulations of isoviscous mantle convection in spherical geometry, varying Ra and P. Three domains of behaviour were found: layered convection for high Ra and more negative P, whole mantle convection for low Ra and less negative P, and transitional behaviour in an intervening domain. The boundary between the layered and transitional domain was fit by a curve P = α Raβ where α = −1.05, and β = −0.1, and the fit for the boundary between the transitional and whole mantle convection domain was α = −4.8, and β = −0.25. These two curves converge at Ra ≈ 2.5 × 104 (well below Earth mantle vigour and P ≈ −0.38. Extrapolating to high Ra, which is likely earlier in Earth history, this work suggests a large transitional domain. It is therefore likely that convection in the Archean would have been influenced by this phase change, with Earth being at least in the transitional domain, if not the layered domain.

  6. Role of Rayleigh numbers on characteristics of double diffusive salt fingers

    Science.gov (United States)

    Rehman, F.; Singh, O. P.

    2018-05-01

    Double diffusion convection, driven by two constituents of the fluid with different molecular diffusivity, is widely applied in oceanography and large number of other fields like astrophysics, geology, chemistry and metallurgy. In case of ocean, heat (T) and salinity (S) are the two components with varying diffusivity, where heat diffuses hundred times faster than salt. Component (T) stabilizes the system whereas components (S) destabilizes the system with overall density remains stable and forms the rising and sinking fingers known as salt fingers. Recent observations suggest that salt finger characteristics such as growth rates, wavenumber, and fluxes are strongly depending on the Rayleigh numbers as major driving force. In this paper, we corroborate this observation with the help of experiments, numerical simulations and linear theory. An eigenvalue expression for growth rate is derived from the linearized governing equations with explicit dependence on Rayleigh numbers, density stability ratio, Prandtl number and diffusivity ratio. Expressions for fastest growing fingers are also derived as a function various non-dimensional parameter. The predicted results corroborate well with the data reported from the field measurements, experiments and numerical simulations.

  7. Self-similarity in high Atwood number Rayleigh-Taylor experiments

    Science.gov (United States)

    Mikhaeil, Mark; Suchandra, Prasoon; Pathikonda, Gokul; Ranjan, Devesh

    2017-11-01

    Self-similarity is a critical concept in turbulent and mixing flows. In the Rayleigh-Taylor instability, theory and simulations have shown that the flow exhibits properties of self-similarity as the mixing Reynolds number exceeds 20000 and the flow enters the turbulent regime. Here, we present results from the first large Atwood number (0.7) Rayleigh-Taylor experimental campaign for mixing Reynolds number beyond 20000 in an effort to characterize the self-similar nature of the instability. Experiments are performed in a statistically steady gas tunnel facility, allowing for the evaluation of turbulence statistics. A visualization diagnostic is used to study the evolution of the mixing width as the instability grows. This allows for computation of the instability growth rate. For the first time in such a facility, stereoscopic particle image velocimetry is used to resolve three-component velocity information in a plane. Velocity means, fluctuations, and correlations are considered as well as their appropriate scaling. Probability density functions of velocity fields, energy spectra, and higher-order statistics are also presented. The energy budget of the flow is described, including the ratio of the kinetic energy to the released potential energy. This work was supported by the DOE-NNSA SSAA Grant DE-NA0002922.

  8. Heat transfer and large scale dynamics in turbulent Rayleigh-Bénard convection

    NARCIS (Netherlands)

    Ahlers, Günter; Grossmann, Siegfried; Lohse, Detlef

    2009-01-01

    The progress in our understanding of several aspects of turbulent Rayleigh-Bénard convection is reviewed. The focus is on the question of how the Nusselt number and the Reynolds number depend on the Rayleigh number Ra and the Prandtl number Pr, and on how the thicknesses of the thermal and the

  9. Kinetic energy and scalar spectra in high Rayleigh number axially homogeneous buoyancy driven turbulence

    Science.gov (United States)

    Pawar, Shashikant S.; Arakeri, Jaywant H.

    2016-06-01

    Kinetic energy and scalar spectra from the measurements in high Rayleigh number axially homogeneous buoyancy driven turbulent flow are presented. Kinetic energy and concentration (scalar) spectra are obtained from the experiments wherein density difference is created using brine and fresh water and temperature spectra are obtained from the experiments in which heat is used. Scaling of the frequency spectra of lateral and longitudinal velocity near the tube axis is closer to the Kolmogorov-Obukhov scaling, while the scalar spectra show some evidence of dual scaling, Bolgiano-Obukhov scaling followed by Obukhov-Corrsin scaling. These scalings are also observed in the corresponding second order spatial structure functions of velocity and concentration fluctuations.

  10. Stabilization of ablative Rayleigh-Taylor instability due to change of the Atwood number

    International Nuclear Information System (INIS)

    Ye Wenhua; He, X.T.; Zhang Weiyan

    2002-01-01

    Recent experiment [S.G. Glendinning et al., Phys. Rev. Lett. 78, 3318 (1997)] showed that the measured growth rate of laser ablative Rayleigh-Taylor (RT) instability with preheating is about 50% of the classic value and is reduced by about 18% compared with the simulated value obtained with the computer code LASNEX. By changing the temperature variation of the electron thermal conductivity at low temperatures, the density profile from the Bhatnagar-Gross-Krook approximation is recovered in the simulation, and the simulated RT growth rate is in good agreement with the experimental value from Glendinning et al. The preheated density profile on ablative RT stablization is studied numerically. A change of the Atwood number in the preheating case also leads to RT stabilization. The RT growth formula γ=√(Akg/(1+AkL))-2kV a agrees well with experiment and simulation, and is appropriate for the preheating case

  11. Ground Boundary Conditions for Thermal Convection Over Horizontal Surfaces at High Rayleigh Numbers

    Science.gov (United States)

    Hanjalić, K.; Hrebtov, M.

    2016-07-01

    We present "wall functions" for treating the ground boundary conditions in the computation of thermal convection over horizontal surfaces at high Rayleigh numbers using coarse numerical grids. The functions are formulated for an algebraic-flux model closed by transport equations for the turbulence kinetic energy, its dissipation rate and scalar variance, but could also be applied to other turbulence models. The three-equation algebraic-flux model, solved in a T-RANS mode ("Transient" Reynolds-averaged Navier-Stokes, based on triple decomposition), was shown earlier to reproduce well a number of generic buoyancy-driven flows over heated surfaces, albeit by integrating equations up to the wall. Here we show that by using a set of wall functions satisfactory results are found for the ensemble-averaged properties even on a very coarse computational grid. This is illustrated by the computations of the time evolution of a penetrative mixed layer and Rayleigh-Bénard (open-ended, 4:4:1 domain) convection, using 10 × 10 × 100 and 10 × 10 × 20 grids, compared also with finer grids (e.g. 60 × 60 × 100), as well as with one-dimensional treatment using 1 × 1 × 100 and 1 × 1 × 20 nodes. The approach is deemed functional for simulations of a convective boundary layer and mesoscale atmospheric flows, and pollutant transport over realistic complex hilly terrain with heat islands, urban and natural canopies, for diurnal cycles, or subjected to other time and space variations in ground conditions and stratification.

  12. GPU Implementation of High Rayleigh Number Three-Dimensional Mantle Convection

    Science.gov (United States)

    Sanchez, D. A.; Yuen, D. A.; Wright, G. B.; Barnett, G. A.

    2010-12-01

    Although we have entered the age of petascale computing, many factors are still prohibiting high-performance computing (HPC) from infiltrating all suitable scientific disciplines. For this reason and others, application of GPU to HPC is gaining traction in the scientific world. With its low price point, high performance potential, and competitive scalability, GPU has been an option well worth considering for the last few years. Moreover with the advent of NVIDIA's Fermi architecture, which brings ECC memory, better double-precision performance, and more RAM to GPU, there is a strong message of corporate support for GPU in HPC. However many doubts linger concerning the practicality of using GPU for scientific computing. In particular, GPU has a reputation for being difficult to program and suitable for only a small subset of problems. Although inroads have been made in addressing these concerns, for many scientists GPU still has hurdles to clear before becoming an acceptable choice. We explore the applicability of GPU to geophysics by implementing a three-dimensional, second-order finite-difference model of Rayleigh-Benard thermal convection on an NVIDIA GPU using C for CUDA. Our code reaches sufficient resolution, on the order of 500x500x250 evenly-spaced finite-difference gridpoints, on a single GPU. We make extensive use of highly optimized CUBLAS routines, allowing us to achieve performance on the order of O( 0.1 ) µs per timestep*gridpoint at this resolution. This performance has allowed us to study high Rayleigh number simulations, on the order of 2x10^7, on a single GPU.

  13. The Role of Viscosity Contrast on the Plume Structure and Dynamics in High Rayleigh Number Convection

    Science.gov (United States)

    Kr, Sreenivas; Prakash, Vivek N.; Arakeri, Jaywant H.

    2010-11-01

    We study the plume structure in high Rayleigh number convection in the limit of large Prandtl numbers. This regime is relevant in Mantle convection, where the plume dynamics is not well understood due to complex rheology and chemical composition. We use analogue laboratory experiments to mimic mantle convection. Our focus in this paper is to understand the role of viscosity ratio, U, between the plume fluid and the ambient fluid on the structure and dynamics of the plumes. The PLIF technique has been used to visualize the structures of plumes rising from a planar source of compositional buoyancy at different regimes of U (1/300 to 2500). In the near-wall planform when U is one, a well-known dendritic line plume structure is observed. As U increases (U > 1; mantle hot spots), there is a morphological transition from line plumes to discrete spherical blobs, accompanied by an increase in the plume spacing and thickness. In vertical sections, as U increases (U > 1), the plume head shape changes from a mushroom-like structure to a "spherical-blob." When the U is decreased below one, (U<1; subduction regime), the formation of cellular patterns is favoured with sheet plumes. Both velocity and mixing efficiency are maximum when U is one, and decreases for extreme values of U. We quantify the morphological changes, dynamics and mixing variations of the plumes from experiments at different regimes.

  14. Detailed Measurements of Rayleigh-Taylor Mixing at Large and Small Atwood Numbers

    International Nuclear Information System (INIS)

    Malcolm, J.; Andrews, Ph.D.

    2004-01-01

    This project has two major tasks: Task 1. The construction of a new air/helium facility to collect detailed measurements of Rayleigh-Taylor (RT) mixing at high Atwood number, and the distribution of these data to LLNL, LANL, and Alliance members for code validation and design purposes. Task 2. The collection of initial condition data from the new Air/Helium facility, for use with validation of RT simulation codes at LLNL and LANL. Also, studies of multi-layer mixing with the existing water channel facility. Over the last twelve (12) months there has been excellent progress, detailed in this report, with both tasks. As of December 10, 2004, the air/helium facility is now complete and extensive testing and validation of diagnostics has been performed. Currently experiments with air/helium up to Atwood numbers of 0.25 (the maximum is 0.75, but the highest Reynolds numbers are at 0.25) are being performed. The progress matches the project plan, as does the budget, and we expect this to continue for 2005. With interest expressed from LLNL we have continued with initial condition studies using the water channel. This work has also progressed well, with one of the graduate Research Assistants (Mr. Nick Mueschke) visiting LLNL the past two summers to work with Dr. O. Schilling. Several journal papers are in preparation that describe the work. Two MSc.'s have been completed (Mr. Nick Mueschke, and Mr. Wayne Kraft, 12/1/03). Nick and Wayne are both pursuing Ph.D.s' funded by this DOE Alliances project. Presently three (3) Ph.D. graduate Research Assistants are supported on the project, and two (2) undergraduate Research Assistants. During the year two (2) journal papers and two (2) conference papers have been published, ten (10) presentations made at conferences, and three (3) invited presentations

  15. Lattice Boltzmann analysis of effect of heating location and Rayleigh number on natural convection in partially heated open ended cavity

    Energy Technology Data Exchange (ETDEWEB)

    Gangawane, Krunal Madhukar; Bharti, Ram Prakash; Kumar, Surendra [Indian Institute of Technology Roorkee, Uttarakhand (India)

    2015-08-15

    Natural convection characteristics of a partially heated open ended square cavity have been investigated numerically by using an in-house computational flow solver based on the passive scalar thermal lattice Boltzmann method (PS-TLBM) with D2Q9 (two-dimensional and nine-velocity link) lattice model. The partial part of left wall of the cavity is heated isothermally at either of the three different (bottom, middle and top) locations for the fixed heating length as half of characteristic length (H/2) while the right wall is open to the ambient conditions. The other parts of the cavity are thermally isolated. In particular, the influences of partial heating locations and Rayleigh number (103≤ Ra≤106) in the laminar zone on the local and global natural convection characteristics (such as streamline, vorticity and isotherm contours; centerline variations of velocity and temperature; and local and average Nusselt numbers) have been presented and discussed for the fixed value of the Prandtl number (Pr=0.71). The streamline patterns show qualitatively similar nature for all the three heating cases and Rayleigh numbers, except the change in the recirculation zone which is found to be largest for middle heating case. Isotherm patterns are shifted towards a partially heated wall on increasing Rayleigh number and/or shifting of heating location from bottom to top. Both the local and average Nusselt numbers, as anticipated, shown proportional increase with Rayleigh number. The cavity with middle heating location shown higher heat transfer rate than that for the top and bottom heating cases. Finally, the functional dependence of the average Nusselt number on flow governing parameters is also presented as a closure relationship for the best possible utilization in engineering practices and design.

  16. Non-Oberbeck-Boussinesq effects in two-dimensional Rayleigh-Bénard convection in glycerol

    NARCIS (Netherlands)

    Sugiyama, K.; Calzavarini, E.; Grossmann, S.; Lohse, Detlef

    2007-01-01

    We numerically analyze Non-Oberbeck-Boussinesq (NOB) effects in two-dimensional Rayleigh-Benard flow in glycerol, which shows a dramatic change in the viscosity with temperature. The results are presented both as functions of the Rayleigh number Ra up to 108 (for fixed temperature difference �

  17. Numerical simulations of thermal convection in a rotating spherical fluid shell at high Taylor and Rayleigh numbers

    International Nuclear Information System (INIS)

    Sun, Z.; Schubert, G.

    1995-01-01

    In this study, we carry out numerical simulations of thermal convection in a rapidly rotating spherical fluid shell at high Taylor number Ta and Rayleigh number R with a nonlinear, three-dimensional, time-dependent, spectral-transform code. The parameters used in the simulations are chosen to be in a range which allows us to study two different types of convection, i.e., single column and multi-layered types, and the transition between them. Numerical solutions feature highly time-dependent north--south open columnar convective cells. The cells occur irregularly in longitude, are quasi-layered in cylindrical radius, and maintain alternating bands of mean zonal flow. The complex convective structure and the banded mean zonal flow are results of the high Taylor and Rayleigh numbers. The transition between the two types of convection appears to occur gradually with increasing Rayleigh and Taylor numbers. At a Taylor number of 10 7 the differential rotation pattern consists of an inner cylindrical region of subrotation and an outer cylindrical shell of superrotation manifest at the outer boundary as an equatorial superrotation and a high latitude subrotation. The differential rotation pattern is similar at Ta=10 8 and low Rayleigh number. Cylindrical shells of alternately directed mean zonal flow begin to develop at Ta=10 8 and R=50R c and at Ta=10 9 and R=25R c . This pattern is seen on the outer surface as a latitudinally-banded zonal flow consisting of an equatorial superrotation, a middle and high latitude subrotation, and a polar superrotation. At Ta=10 9 and R=50R c the differential rotation appears at the surface as a broad eastward flow in the equatorial region with alternating bands of westward and eastward flow at high latitudes. copyright 1995 American Institute of Physics

  18. Experimental study of Rayleigh scattering with a ruby laser beam: relative variation of scattered light with the number of scattering center and the gases nature

    International Nuclear Information System (INIS)

    Bayer, Charles

    1973-06-01

    The experimental variation of the scattered light with the number of scattering centers and with the refraction index of gases is in agreement with the theoretical Rayleigh scattering. A direct calibration System gives the absolute value of the Rayleigh ratio. The experimental value appears to be half of the theoretical one. (author) [fr

  19. Thermal convection for large Prandtl numbers

    NARCIS (Netherlands)

    Grossmann, Siegfried; Lohse, Detlef

    2001-01-01

    The Rayleigh-Bénard theory by Grossmann and Lohse [J. Fluid Mech. 407, 27 (2000)] is extended towards very large Prandtl numbers Pr. The Nusselt number Nu is found here to be independent of Pr. However, for fixed Rayleigh numbers Ra a maximum in the Nu(Pr) dependence is predicted. We moreover offer

  20. Thermal convection of a viscoplastic liquid with high Rayleigh and Bingham numbers

    Science.gov (United States)

    Vikhansky, A.

    2009-10-01

    We consider the effect of yield stress on the Rayleigh-Bénard convection of a viscoplastic material. First we consider the model problem of convection in a differentially heated loop, which is described by the (modified) Lorenz equations. The presence of the yield stress significantly alters the dynamics of the system. In particular, the chaotic motion can stop suddenly (sometimes, after a period of chaotic oscillations). Guided by the model equations we performed direct numerical simulations of convection of the Bingham liquid in a square cavity heated from bellow. Our interest has been concentrated on the situation when both buoyancy and plastic forces are large. The obtained results are in a reasonable agreement with the predictions by the Lorenz equations.

  1. Experimental characterization of initial conditions and spatio-temporal evolution of a small Atwood number Rayleigh-Taylor mixing layer

    Energy Technology Data Exchange (ETDEWEB)

    Mueschke, N J; Andrews, M J; Schilling, O

    2005-09-26

    The initial multi-mode interfacial velocity and density perturbations present at the onset of a small Atwood number, incompressible, miscible, Rayleigh-Taylor instability-driven mixing layer have been quantified using a combination of experimental techniques. The streamwise interfacial and spanwise interfacial perturbations were measured using high-resolution thermocouples and planar laser-induced fluorescence (PLIF), respectively. The initial multi-mode streamwise velocity perturbations at the two-fluid density interface were measured using particle-image velocimetry (PIV). It was found that the measured initial conditions describe an initially anisotropic state, in which the perturbations in the streamwise and spanwise directions are independent of one another. The evolution of various fluctuating velocity and density statistics, together with velocity and density variance spectra, were measured using PIV and high-resolution thermocouple data. The evolution of the velocity and density statistics is used to investigate the early-time evolution and the onset of strongly-nonlinear, transitional dynamics within the mixing layer. The early-time evolution of the density and vertical velocity variance spectra indicate that velocity fluctuations are the dominant mechanism driving the instability development. The implications of the present experimental measurements on the initialization of Reynolds-averaged turbulent transport and mixing models and of direct and large-eddy simulations of Rayleigh-Taylor instability-induced turbulence are discussed.

  2. Study of the relationship between peaks scattering Rayleigh to Compton ratio and effective atomic number in biological samples

    International Nuclear Information System (INIS)

    Pereira, Marcelo O.; Conti, Claudio de Carvalho; Anjos, Marcelino J.; Lopes, Ricardo T.

    2011-01-01

    The aim of this work was to develop a new method to correct the absorbed radiation (the mass attenuation coefficient curve) in low energy (E B O 3 , Na 2 CO 3 , CaCO 3 , Al 2 O 3 , K 2 SO 4 and MgO) of radiation produced by a gamma-ray source of Am-241(59.54 keV) also applied to certified biological samples of milk powder, hay powder and bovine liver (NIST 155 7B). In addition, six methods of effective atomic number determination were used as described in literature to determinate the Rayleigh to Compton scattering ratio (R/C) , in order to calculate the mass attenuation coefficient. The results obtained by the proposed method were compared with those obtained using the transmission method. The experimental results were in good agreement with transmission values suggesting that the method to correct radiation absorption presented in this paper is adequate for biological samples. (author)

  3. Effects of initial radius of the interface and Atwood number on nonlinear saturation amplitudes in cylindrical Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Liu, Wanhai; Yu, Changping; Li, Xinliang

    2014-01-01

    Nonlinear saturation amplitudes (NSAs) of the first two harmonics in classical Rayleigh-Taylor instability (RTI) in cylindrical geometry for arbitrary Atwood numbers have been analytically investigated considering nonlinear corrections up to the fourth-order. The NSA of the fundamental mode is defined as the linear (purely exponential) growth amplitude of the fundamental mode at the saturation time when the growth of the fundamental mode (first harmonic) is reduced by 10% in comparison to its corresponding linear growth, and the NSA of the second harmonic can be obtained in the same way. The analytic results indicate that the effects of the initial radius of the interface (r 0 ) and the Atwood number (A) play an important role in the NSAs of the first two harmonics in cylindrical RTI. On the one hand, the NSA of the fundamental mode first increases slightly and then decreases quickly with increasing A. For given A, the smaller the r 0 /λ (with λ perturbation wavelength) is, the larger the NSA of the fundamental mode is. When r 0 /λ is large enough (r 0 ≫λ), the NSA of the fundamental mode is reduced to the prediction of previous literatures within the framework of third-order perturbation theory [J. W. Jacobs and I. Catton, J. Fluid Mech. 187, 329 (1988); S. W. Haan, Phys. Fluids B 3, 2349 (1991)]. On the other hand, the NSA of the second harmonic first decreases quickly with increasing A, reaching a minimum, and then increases slowly. Furthermore, the r 0 can reduce the NSA of the second harmonic for arbitrary A at r 0 ≲2λ while increase it for A ≲ 0.6 at r 0 ≳2λ. Thus, it should be included in applications where the NSA has a role, such as inertial confinement fusion ignition target design

  4. Turbulent thermal superstructures in Rayleigh-Bénard convection

    Science.gov (United States)

    Stevens, Richard J. A. M.; Blass, Alexander; Zhu, Xiaojue; Verzicco, Roberto; Lohse, Detlef

    2018-04-01

    We report the observation of superstructures, i.e., very large-scale and long living coherent structures in highly turbulent Rayleigh-Bénard convection up to Rayleigh Ra=109 . We perform direct numerical simulations in horizontally periodic domains with aspect ratios up to Γ =128 . In the considered Ra number regime the thermal superstructures have a horizontal extend of six to seven times the height of the domain and their size is independent of Ra. Many laboratory experiments and numerical simulations have focused on small aspect ratio cells in order to achieve the highest possible Ra. However, here we show that for very high Ra integral quantities such as the Nusselt number and volume averaged Reynolds number only converge to the large aspect ratio limit around Γ ≈4 , while horizontally averaged statistics such as standard deviation and kurtosis converge around Γ ≈8 , the integral scale converges around Γ ≈32 , and the peak position of the temperature variance and turbulent kinetic energy spectra only converge around Γ ≈64 .

  5. Effects of intra-VMN mianserin and IL-1ra on meal number in anorectic tumor-bearing rats.

    Science.gov (United States)

    Laviano, A; Gleason, J R; Meguid, M M; Yang, Z J; Cangiano, C; Rossi Fanelli, F

    2000-01-01

    Tumor growth in animals and humans is associated with the onset of anorexia and reduced food intake. We previously demonstrated that the ventromedial nucleus of hypothalamus (VMN) plays a contributory role in mediating cancer anorexia. Because serotonin and interleukin-1 (IL-1) are putative mediators of cancer anorexia, we hypothesized that their influence on food intake during tumor growth might occur via their action within the VMN. To test this hypothesis, 12 Fischer rats injected subcutaneously with 10(6) viable MCA sarcoma cells (TB rats) and their nontumor-bearing controls (NTB, n = 13) were studied. When anorexia developed, TB and NTB rats received bilateral intra-VMN microinjections of the serotonin antagonist mianserin (200 nmol) or the IL-1 receptor antagonist (IL-1ra, 25 ng). Food intake and its determinants of meal number and size were continuously recorded via a computerized device. In NTB rats, intra-VMN mianserin did not affect food intake, whereas after IL-1ra or vehicle a momentary decrease in food intake due to a predominant reduction of meal size occurred. In TB rats, intra-VMN mianserin or IL-1ra selectively increased meal number, leading to improved food intake. Data suggest that intra-VMN serotonin and IL-1 are involved in influencing cancer related anorexia.

  6. Direct simulation of turbulent Rayleigh-Benard convection in liquid sodium

    International Nuclear Information System (INIS)

    Woerner, M.

    1994-11-01

    The numerical results are analysed to investigate both the structures and mechanisms of convection and the statistical features of turbulence in natural convection of liquid metals. The simulations are performed with the finite volume code TURBIT which is extended by a semi-implicit time integration scheme for the energy equation. Due to the implicit treatment of thermal diffusion the computational time for simulation of natural convection in liquid metals is reduced by about one order of magnitude, as compared to the original fully explicit code version. Results for Rayleigh-Benard convection in liquid sodium with Prandtl number Pr=0.006 are given for four different Rayleigh numbers: Ra=3 000, Ra=6 000, Ra=12 000, and Ra=24 000. At the Rayleigh number Ra=3 000 the inertial convection is identified. It is characterized by large two-dimensional vortices, which rotate like a solid body. These vortices are also observed in the simulations for Ra=6 000, Ra=12 000 and Ra=24 000, but, they only exist in certain regions and for short time intervals. The appearance of these two-dimensional structures in three-dimensional, time-dependent and turbulent convection is explained by the relative importance of the non-linear terms in the momentum and energy equation, which is totally different in both equations, and by the coupling of these equations by the buoyancy and the convective term. In order to improve and validate statistical turbulence model for application to natural convection in liquid metals, budgets of turbulence kinetic energy, turbulent heat flux and temperature variance are calculated from the numerical results. For several unknown correlations closure assumptions used in standard turbulence models are analyzed and model coefficients are determined. (orig./HP) [de

  7. RA Reactor; Reaktor RA

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1989-07-01

    This chapter includes the following: General description of the RA reactor, organization of work, responsibilities of leadership and operators team, regulations concerning operation and behaviour in the reactor building, regulations for performing experiments, regulations and instructions for inserting samples into experimental channels. [Serbo-Croat] Ovo (prvo) poglavlje sadrzi sledece: Opis reaktora RA; semu organizacije rada i rukovodjenja; prava i duznosti direktora i rukovodioca pogona reaktora, propise o rezimu rada i kretanja u zgradi reaktora, propise o izvodjenju eksperimenata, propise o unosenju uzoraka u eksperimentalne kanale reaktora.

  8. RA Reactor; Reaktor RA

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1978-02-15

    In addition to basic characteristics of the RA reactor, organizational scheme and financial incentives, this document covers describes the state of the reactor components after 18 years of operation, problems concerned with obtaining the licence for operation with 80% fuel, problems of spent fuel storage in the storage pool of the reactor building and the need for renewal of reactor equipment, first of all instrumentation. [Serbo-Croat] Pored osnovnih karakeristika reaktora RA, organizacije rada i finansijskih pokazatelja, razmatra se stanje opreme reaktora nakon 18 godina rada, pitanja dozvole za rad sa 80% obogacenim gorivom, problem skladistenja isluzenog goriva u bazenu zgrade reaktora i potreba za obnavljanjem komponenti opreme, pre svega elektronske.

  9. Numerical simulation of nonstationary dissipative structures in 3D double-diffusive convection at large Rayleigh numbers

    Science.gov (United States)

    Kozitskiy, Sergey

    2018-05-01

    Numerical simulation of nonstationary dissipative structures in 3D double-diffusive convection has been performed by using the previously derived system of complex Ginzburg-Landau type amplitude equations, valid in a neighborhood of Hopf bifurcation points. Simulation has shown that the state of spatiotemporal chaos develops in the system. It has the form of nonstationary structures that depend on the parameters of the system. The shape of structures does not depend on the initial conditions, and a limited number of spectral components participate in their formation.

  10. Transition to the Ultimate Regime in Two-Dimensional Rayleigh-Bénard Convection

    Science.gov (United States)

    Zhu, Xiaojue; Mathai, Varghese; Stevens, Richard J. A. M.; Verzicco, Roberto; Lohse, Detlef

    2018-04-01

    The possible transition to the so-called ultimate regime, wherein both the bulk and the boundary layers are turbulent, has been an outstanding issue in thermal convection, since the seminal work by Kraichnan [Phys. Fluids 5, 1374 (1962), 10.1063/1.1706533]. Yet, when this transition takes place and how the local flow induces it is not fully understood. Here, by performing two-dimensional simulations of Rayleigh-Bénard turbulence covering six decades in Rayleigh number Ra up to 1 014 for Prandtl number Pr =1 , for the first time in numerical simulations we find the transition to the ultimate regime, namely, at Ra*=1013 . We reveal how the emission of thermal plumes enhances the global heat transport, leading to a steeper increase of the Nusselt number than the classical Malkus scaling Nu ˜Ra1 /3 [Proc. R. Soc. A 225, 196 (1954), 10.1098/rspa.1954.0197]. Beyond the transition, the mean velocity profiles are logarithmic throughout, indicating turbulent boundary layers. In contrast, the temperature profiles are only locally logarithmic, namely, within the regions where plumes are emitted, and where the local Nusselt number has an effective scaling Nu ˜Ra0.38 , corresponding to the effective scaling in the ultimate regime.

  11. [Computer modeling the dependences of the membrane potential for polymeric membrane separated non-homogeneous electrolyte solutions on concentration Rayleigh number].

    Science.gov (United States)

    Slezak, Izabella H; Jasik-Slezak, Jolanta; Bilewicz-Wyrozumska, Teresa; Slezak, Andrzej

    2006-01-01

    On the basis of model equation describing the membrane potential delta psi(s) on concentration Rayleigh number (R(C)), mechanical pressure difference (deltaP), concentration polarization coefficient (zeta s) and ratio concentration of solutions separated by membrane (Ch/Cl), the characteristics delta psi(s) = f(Rc)(delta P, zeta s, Ch/Cl) for steady values of zeta s, R(C) and Ch/Cl in single-membrane system were calculated. In this system neutral and isotropic polymeric membrane oriented in horizontal plane, the non-homogeneous binary electrolytic solutions of various concentrations were separated. Nonhomogeneity of solutions is results from creations of the concentration boundary layers on both sides of the membrane. Calculations were made for the case where on a one side of the membrane aqueous solution of NaCl at steady concentration 10(-3) mol x l(-1) (Cl) was placed and on the other aqueous solutions of NaCl at concentrations from 10(-3) mol x l(-1) to 2 x 10(-2) mol x l(-1) (Ch). Their densities were greater than NaCl solution's at 10(-3) mol x l(-1). It was shown that membrane potential depends on hydrodynamic state of a complex concentration boundary layer-membrane-concentration boundary layer, what is controlled by deltaP, Ch/Cl, Rc and Zeta(s).

  12. Advection diffusion model for particles deposition in Rayleigh-Benard turbulent flows

    International Nuclear Information System (INIS)

    Oresta, P.; Lippolis, A.; Verzicco, R.; Soldati, A.

    2005-01-01

    In this paper, Direct Numerical Simulation (DNS) and Lagrangian Particle Tracking are used to precisely investigate the turbulent thermally driven flow and particles dispersion in a closed, slender cylindrical domain. The numerical simulations are carried out for Rayleigh (Ra) and Prandtl numbers (Pr) equal to Ra = 2X10 8 and Pr = 0.7, considering three sets of particles with Stokes numbers, based on Kolmogorov scale, equal to St k 1.3, St k 0.65 and St k = 0.13. This data are used to calculate a priori the drift velocity and the turbulent diffusion coefficient for the Advection Diffusion model. These quantities are function of the Stokes, Froude, Rayleigh and Prandtl numbers only. One dimensional, time dependent, Advection- Diffusion Equation (ADE) is presented to predict particles deposition in Rayleigh-Benard flow in the cylindrical domain. This archetype configuration models flow and aerosol dynamics, produced in case of accident in the passive containment cooling system (PCCS) of a nuclear reactor. ADE results show a good agreement with DNS data for all the sets of particles investigated. (author)

  13. Time-stepping approach for solving upper-bound problems: Application to two-dimensional Rayleigh-Bénard convection

    Science.gov (United States)

    Wen, Baole; Chini, Gregory P.; Kerswell, Rich R.; Doering, Charles R.

    2015-10-01

    An alternative computational procedure for numerically solving a class of variational problems arising from rigorous upper-bound analysis of forced-dissipative infinite-dimensional nonlinear dynamical systems, including the Navier-Stokes and Oberbeck-Boussinesq equations, is analyzed and applied to Rayleigh-Bénard convection. A proof that the only steady state to which this numerical algorithm can converge is the required global optimal of the relevant variational problem is given for three canonical flow configurations. In contrast with most other numerical schemes for computing the optimal bounds on transported quantities (e.g., heat or momentum) within the "background field" variational framework, which employ variants of Newton's method and hence require very accurate initial iterates, the new computational method is easy to implement and, crucially, does not require numerical continuation. The algorithm is used to determine the optimal background-method bound on the heat transport enhancement factor, i.e., the Nusselt number (Nu), as a function of the Rayleigh number (Ra), Prandtl number (Pr), and domain aspect ratio L in two-dimensional Rayleigh-Bénard convection between stress-free isothermal boundaries (Rayleigh's original 1916 model of convection). The result of the computation is significant because analyses, laboratory experiments, and numerical simulations have suggested a range of exponents α and β in the presumed Nu˜PrαRaβ scaling relation. The computations clearly show that for Ra≤1010 at fixed L =2 √{2 },Nu≤0.106 Pr0Ra5/12 , which indicates that molecular transport cannot generally be neglected in the "ultimate" high-Ra regime.

  14. RA Reactor

    International Nuclear Information System (INIS)

    1989-01-01

    This chapter includes the following: General description of the RA reactor, organization of work, responsibilities of leadership and operators team, regulations concerning operation and behaviour in the reactor building, regulations for performing experiments, regulations and instructions for inserting samples into experimental channels [sr

  15. RA Reactor

    International Nuclear Information System (INIS)

    1978-02-01

    In addition to basic characteristics of the RA reactor, organizational scheme and financial incentives, this document covers describes the state of the reactor components after 18 years of operation, problems concerned with obtaining the licence for operation with 80% fuel, problems of spent fuel storage in the storage pool of the reactor building and the need for renewal of reactor equipment, first of all instrumentation [sr

  16. Lateral movements in Rayleigh-Taylor instabilities due to frontiers. Experimental study

    Science.gov (United States)

    Binda, L.; Fernández, D.; El Hasi, C.; Zalts, A.; D'Onofrio, A.

    2018-01-01

    Lateral movements of the fingers in Rayleigh-Taylor hydrodynamic instabilities at the interface between two fluids are studied. We show that transverse movements appear when a physical boundary is present; these phenomena have not been explained until now. The boundary prevents one of the fluids from crossing it. Such frontiers can be buoyancy driven as, for example, the frontier to the passage of a less dense solution through a denser solution or when different aggregation states coexist (liquid and gaseous phases). An experimental study of the lateral movement velocity of the fingers was performed for different Rayleigh numbers (Ra), and when oscillations were detected, their amplitudes were studied. Liquid-liquid (L-L) and gas-liquid (G-L) systems were analysed. Aqueous HCl and Bromocresol Green (sodium salt, NaBCG) solutions were used in L-L experiments, and CO2 (gas) and aqueous NaOH, NaHCO3, and CaCl2 solutions were employed for the G-L studies. We observed that the lateral movement of the fingers and finger collapses near the interface are more notorious when Ra increases. The consequences of this, for each experience, are a decrease in the number of fingers and an increase in the velocity of the lateral finger movement close to the interface as time evolves. We found that the amplitude of the oscillations did not vary significantly within the considered Ra range. These results have an important implication when determining the wave number of instabilities in an evolving system. The wave number could be strongly diminished if there is a boundary.

  17. Large-scale patterns in Rayleigh-Benard convection

    International Nuclear Information System (INIS)

    Hardenberg, J. von; Parodi, A.; Passoni, G.; Provenzale, A.; Spiegel, E.A.

    2008-01-01

    Rayleigh-Benard convection at large Rayleigh number is characterized by the presence of intense, vertically moving plumes. Both laboratory and numerical experiments reveal that the rising and descending plumes aggregate into separate clusters so as to produce large-scale updrafts and downdrafts. The horizontal scales of the aggregates reported so far have been comparable to the horizontal extent of the containers, but it has not been clear whether that represents a limitation imposed by domain size. In this work, we present numerical simulations of convection at sufficiently large aspect ratio to ascertain whether there is an intrinsic saturation scale for the clustering process when that ratio is large enough. From a series of simulations of Rayleigh-Benard convection with Rayleigh numbers between 10 5 and 10 8 and with aspect ratios up to 12π, we conclude that the clustering process has a finite horizontal saturation scale with at most a weak dependence on Rayleigh number in the range studied

  18. Rayleigh reciprocity relations: Applications

    International Nuclear Information System (INIS)

    Lin Ju; Li Xiao-Lei; Wang Ning

    2016-01-01

    Classical reciprocity relations have wide applications in acoustics, from field representation to generalized optical theorem. In this paper we introduce our recent results on the applications and generalization of classical Rayleigh reciprocity relation: higher derivative reciprocity relations as a generalization of the classical one and a theoretical proof on the Green’s function retrieval from volume noises. (special topic)

  19. Rayleigh- and Prandtl-number dependence of the large-scale flow-structure in weakly-rotating turbulent thermal convection

    Science.gov (United States)

    Weiss, Stephan; Wei, Ping; Ahlers, Guenter

    2015-11-01

    Turbulent thermal convection under rotation shows a remarkable variety of different flow states. The Nusselt number (Nu) at slow rotation rates (expressed as the dimensionless inverse Rossby number 1/Ro), for example, is not a monotonic function of 1/Ro. Different 1/Ro-ranges can be observed with different slopes ∂Nu / ∂ (1 / Ro) . Some of these ranges are connected by sharp transitions where ∂Nu / ∂ (1 / Ro) changes discontinuously. We investigate different regimes in cylindrical samples of aspect ratio Γ = 1 by measuring temperatures at the sidewall of the sample for various Prandtl numbers in the range 3 Deutsche Forschungsgemeinschaft.

  20. Rayleigh imaging in spectral mammography

    Science.gov (United States)

    Berggren, Karl; Danielsson, Mats; Fredenberg, Erik

    2016-03-01

    Spectral imaging is the acquisition of multiple images of an object at different energy spectra. In mammography, dual-energy imaging (spectral imaging with two energy levels) has been investigated for several applications, in particular material decomposition, which allows for quantitative analysis of breast composition and quantitative contrast-enhanced imaging. Material decomposition with dual-energy imaging is based on the assumption that there are two dominant photon interaction effects that determine linear attenuation: the photoelectric effect and Compton scattering. This assumption limits the number of basis materials, i.e. the number of materials that are possible to differentiate between, to two. However, Rayleigh scattering may account for more than 10% of the linear attenuation in the mammography energy range. In this work, we show that a modified version of a scanning multi-slit spectral photon-counting mammography system is able to acquire three images at different spectra and can be used for triple-energy imaging. We further show that triple-energy imaging in combination with the efficient scatter rejection of the system enables measurement of Rayleigh scattering, which adds an additional energy dependency to the linear attenuation and enables material decomposition with three basis materials. Three available basis materials have the potential to improve virtually all applications of spectral imaging.

  1. 3rd year final contractor report for: U.S. Department of Energy Stewardship Science Academic Alliances Program Project Title: Detailed Measurements of Rayleigh-Taylor Mixing at Large and Small Atwood Numbers

    International Nuclear Information System (INIS)

    Malcolm J. Andrews

    2006-01-01

    This project had two major tasks: Task 1. The construction of a new air/helium facility to collect detailed measurements of Rayleigh-Taylor (RT) mixing at high Atwood number, and the distribution of these data to LLNL, LANL, and Alliance members for code validation and design purposes. Task 2. The collection of initial condition data from the new Air/Helium facility, for use with validation of RT simulation codes at LLNL and LANL. This report describes work done in the last twelve (12) months of the project, and also contains a summary of the complete work done over the three (3) life of the project. As of April 1, 2006, the air/helium facility (Task 1) is now complete and extensive testing and validation of diagnostics has been performed. Initial condition studies (Task 2) is also complete. Detailed experiments with air/helium with Atwood numbers up to 0.1 have been completed, and Atwood numbers of 0.25. Within the last three (3) months we have been able to successfully run the facility at Atwood numbers of 0.5. The progress matches the project plan, as does the budget. We have finished the initial condition studies using the water channel, and this work has been accepted for publication on the Journal of Fluid Mechanics (the top fluid mechanics journal). Mr. Nick Mueschke and Mr. Wayne Kraft are continuing with their studies to obtain PhDs in the same field, and will also continue their collaboration visits to LANL and LLNL. Over its three (3) year life the project has supported two(2) Ph.D.'s and three (3) MS's, and produced nine (9) international journal publications, twenty four (24) conference publications, and numerous other reports. The highlight of the project has been our close collaboration with LLNL (Dr. Oleg Schilling) and LANL (Drs. Dimonte, Ristorcelli, Gore, and Harlow)

  2. Effect of velocity boundary conditions on the heat transfer and flow topology in two-dimensional Rayleigh-Bénard convection.

    Science.gov (United States)

    van der Poel, Erwin P; Ostilla-Mónico, Rodolfo; Verzicco, Roberto; Lohse, Detlef

    2014-07-01

    The effect of various velocity boundary condition is studied in two-dimensional Rayleigh-Bénard convection. Combinations of no-slip, stress-free, and periodic boundary conditions are used on both the sidewalls and the horizontal plates. For the studied Rayleigh numbers Ra between 10(8) and 10(11) the heat transport is lower for Γ=0.33 than for Γ=1 in case of no-slip sidewalls. This is, surprisingly, the opposite for stress-free sidewalls, where the heat transport increases for a lower aspect ratio. In wider cells the aspect-ratio dependence is observed to disappear for Ra ≥ 10(10). Two distinct flow types with very different dynamics can be seen, mostly dependent on the plate velocity boundary condition, namely roll-like flow and zonal flow, which have a substantial effect on the dynamics and heat transport in the system. The predominantly horizontal zonal flow suppresses heat flux and is observed for stress-free and asymmetric plates. Low aspect-ratio periodic sidewall simulations with a no-slip boundary condition on the plates also exhibit zonal flow. In all the other cases, the flow is roll like. In two-dimensional Rayleigh-Bénard convection, the velocity boundary conditions thus have large implications on both roll-like and zonal flow that have to be taken into consideration before the boundary conditions are imposed.

  3. Association of adiponectin, interleukin (IL)-1ra, inducible protein 10, IL-6 and number of islet autoantibodies with progression patterns of type 1 diabetes the first year after diagnosis

    DEFF Research Database (Denmark)

    Kaas, A; Pfleger, Claudia Christina; Hansen, Lene

    2010-01-01

    The progression of type 1 diabetes after diagnosis is poorly understood. Our aim was to assess the relation of disease progression of juvenile-onset type 1 diabetes, determined by preserved beta cell function the first year after diagnosis, with systemic cytokine concentrations and number...... patients (P = 0·03 and P = 0·006). IL-1ra, IP-10 and IL-6 did not differ between the groups at any time-point. The number of autoantibodies differed significantly between the groups at 1 month (P = 0·04), where rapid progressers had the largest number. There was no difference between the groups in human...

  4. Rayleigh Pareto Distribution

    Directory of Open Access Journals (Sweden)

    Kareema ‎ Abed Al-Kadim

    2017-12-01

    Full Text Available In this paper Rayleigh Pareto distribution have  introduced denote by( R_PD. We stated some  useful functions. Therefor  we  give some of its properties like the entropy function, mean, mode, median , variance , the r-th moment about the mean, the rth moment about the origin, reliability, hazard functions, coefficients of variation, of sekeness and of kurtosis. Finally, we estimate the parameters  so the aim of this search  is to introduce a new distribution

  5. Extended Rayleigh Damping Model

    Directory of Open Access Journals (Sweden)

    Naohiro Nakamura

    2016-07-01

    Full Text Available In dynamic analysis, frequency domain analysis can be used if the entire structure is linear. However, time history analysis is generally used if nonlinear elements are present. Rayleigh damping has been widely used in time history response analysis. Many articles have reported the problems associated with this damping and suggested remedies. A basic problem is that the frequency area across which the damping ratio is almost constant is too narrow. If the area could be expanded while incurring only a small increase in computational cost, this would provide an appropriate remedy for this problem. In this study, a novel damping model capable of expanding the constant frequency area by more than five times was proposed based on the study of a causal damping model. This model was constructed by adding two terms to the Rayleigh damping model and can be applied to the linear elements in the time history analysis of a nonlinear structure. The accuracy and efficiency of the model were confirmed using example analyses.

  6. Effects of shock waves on Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Zhang Yongtao; Shu Chiwang; Zhou Ye

    2006-01-01

    A numerical simulation of two-dimensional compressible Navier-Stokes equations using a high-order weighted essentially nonoscillatory finite difference shock capturing scheme is carried out in this paper, to study the effect of shock waves on the development of Rayleigh-Taylor instability. Shocks with different Mach numbers are introduced ahead or behind the Rayleigh-Taylor interface, and their effect on the transition to instability is demonstrated and compared. It is observed that shock waves can speed up the transition to instability for the Rayleigh-Taylor interface significantly. Stronger shocks are more effective in this speed-up process

  7. Recent results in Rayleigh scattering

    International Nuclear Information System (INIS)

    Kahane, S.; Shahal, O.; Moreh, R.; Ben-Gurion Univ. of the Negev, Beer-Sheva

    1997-01-01

    New measurements of Rayleigh scattering, employing neutron capture γ rays are presented. Experimental conditions are achieved such that the Rayleigh contribution is dominant and much larger than other competing coherent process. A detailed comparison with the modified relativistic form factor approximation (MRFF) is made. It is found that MRFF overestimates the true cross sections by 3-4%. (author)

  8. MUTANTES DE LARANJA - 'PÊRA' COM NÚMERO REDUZIDO DE SEMENTES, OBTIDOS ATRAVÉS DE MUTAÇÕES INDUZIDAS SWEET ORANGE 'PÊRA' MUTANTS WITH LOW NUMBER OF SEEDS OBTAINED THROUGH MUTATION INDUCTION

    Directory of Open Access Journals (Sweden)

    RODRIGO ROCHA LATADO

    2001-08-01

    Full Text Available A obtenção de cultivares de citros com pequeno número de sementes é importante quando o objetivo é a produção de frutas para o consumo in natura. O objetivo deste trabalho foi o de avaliar, por três anos (1997, 1998 e 1999, o número médio de sementes e 15 outras características agronômicas, de 127 mutantes putativos de laranja-'Pêra', selecionados após irradiação de borbulhas com raios-gama e 8 plantas selecionadas do controle não irradiado. Os mutantes foram divididos em 16 grupos baseados nos tipos de mutações observados e em cada grupo, como controle comum, foram incluídas plantas de laranja-'Pêra' comercial. Observou-se que 46 mutantes putativos e uma planta do controle não irradiado (PSC apresentaram redução significativa no número de sementes por fruto, nos três anos consecutivos, sendo que 15 mutantes apresentaram frutos com média entre uma e duas sementes e 9 mutantes, frutos com média inferior a uma semente. Dentre estes 9 mutantes, os de número 27, 28 e 58, que apresentaram também alterações significativas no diâmetro de copa ou na altura de planta, além do 59 e 101, que não apresentaram alterações nas outras 15 características avaliadas, possuem um maior potencial para serem lançados como novos mutantes de laranja-'Pêra' com pequeno número de sementes.Citrus varieties with low number of seeds are important for in natura fruit market. The objective of the present work was to evaluate, for three years (1997, 1998 and 1999, the average number of seeds per fruit and 15 other agronomic characteristics of 127 putative mutated clones of sweet orange 'Pêra', selected after gamma-irradiation of budwood and 8 non irradiated control clones. Mutants were divided in 16 groups based on the type of mutation observed 'Pêra' commercial control plants (PCC were included. It was observed that 46 putative mutants and one non-irradiated plant (PSC showed significant reduction in seed number per fruit. Fifteen

  9. Association of adiponectin, interleukin (IL)-1ra, inducible protein 10, IL-6 and number of islet autoantibodies with progression patterns of type 1 diabetes the first year after diagnosis

    DEFF Research Database (Denmark)

    Kaas, A; Pfleger, Claudia Christina; Hansen, Lene

    2010-01-01

    progressers and remitters. Serum concentrations of adiponectin, interleukin (IL)-1ra, inducible protein 10 (IP-10), IL-6 and glutamic acid decarboxylase (GAD), IA-2A and islet-cell antibodies (ICA) were measured at 1, 6 and 12 months. We found that adiponectin concentrations at 1 month predicted disease......The progression of type 1 diabetes after diagnosis is poorly understood. Our aim was to assess the relation of disease progression of juvenile-onset type 1 diabetes, determined by preserved beta cell function the first year after diagnosis, with systemic cytokine concentrations and number...

  10. 226 Ra in food

    International Nuclear Information System (INIS)

    Toader, M.

    1993-01-01

    Between 1986 and 1992 the author has evaluated natural levels of 226 Ra in some foods representing the major components of the diet in Bucharest population. The estimated daily intake by an adult was 72.5 mBq 226 Ra/day or 65.9 mBq 226 Ra/g.Ca. (Author)

  11. A simple analytic approximation to the Rayleigh-Bénard stability threshold

    NARCIS (Netherlands)

    Prosperetti, Andrea

    2011-01-01

    The Rayleigh-Bénard linear stability problem is solved by means of a Fourier series expansion. It is found that truncating the series to just the first term gives an excellent explicit approximation to the marginal stability relation between the Rayleigh number and the wave number of the

  12. Logarithmic spatial variations and universal f-1 power spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection.

    Science.gov (United States)

    He, Xiaozhou; van Gils, Dennis P M; Bodenschatz, Eberhard; Ahlers, Guenter

    2014-05-02

    We report measurements of the temperature variance σ(2)(z,r) and frequency power spectrum P(f,z,r) (z is the distance from the sample bottom and r the radial coordinate) in turbulent Rayleigh-Bénard convection (RBC) for Rayleigh numbers Ra = 1.6 × 10(13) and 1.1 × 10(15) and for a Prandtl number Pr ≃ 0.8 for a sample with a height L = 224 cm and aspect ratio D/L=0.50 (D is the diameter). For z/L ≲ 0.1 σ(2)(z,r) was consistent with a logarithmic dependence on z, and there was a universal (independent of Ra, r, and z) normalized spectrum which, for 0.02 ≲ fτ(0) ≲ 0.2, had the form P(fτ(0)) = P(0)(fτ(0))(-1) with P(0) = 0.208 ± 0.008 a universal constant. Here τ(0) = sqrt[2R] where R is the radius of curvature of the temperature autocorrelation function C(τ) at τ = 0. For z/L ≃ 0.5 the measurements yielded P(fτ(0))∼(fτ(0))(-α) with α in the range from 3/2 to 5/3. All the results are similar to those for velocity fluctuations in shear flows at sufficiently large Reynolds numbers, suggesting the possibility of an analogy between the flows that is yet to be determined in detail.

  13. Nonlinear saturation of the Rayleigh Taylor instability

    International Nuclear Information System (INIS)

    Das, A.; Mahajan, S.; Kaw, P.; Sen, A.; Benkadda, S.; Verga, A.

    1997-01-01

    The problem of the nonlinear saturation of the 2 dimensional Rayleigh Taylor instability is re-examined to put various earlier results in a proper perspective. The existence of a variety of final states can be attributed to the differences in the choice of boundary conditions and initial conditions in earlier numerical modeling studies. Our own numerical simulations indicate that the RT instability saturates by the self consistent generation of shear flow even in situations (with periodic boundaries) where, in principle, an infinite amount of gravitational energy can be tapped. Such final states can be achieved for suitable values of the Prandtl number. (author)

  14. Nusselt-Rayleigh correlations for design of industrial elements: Experimental and numerical investigation of natural convection in tilted square air filled enclosures

    International Nuclear Information System (INIS)

    Bairi, A.

    2008-01-01

    Natural convection in air filled 2D tilted square cavities is experimentally and numerically studied. The hot and cold walls of the cavity are maintained isothermal at temperatures T h and T c , respectively, and the channel of the cavity is adiabatic. Measurements and simulations are performed for various geometrical and thermal configurations. Different values of the Rayleigh number Ra and the tilt angle α of the cavity are considered. The range of Ra covered in our work extends from 10 to 10 10 while α varies from 0 to 360 deg. This permits the analysis of several significant situations corresponding to vertical active walls (α 0 deg.), hot wall at the bottom (α = 90 deg.; Rayleigh-Benard convection) and hot wall at the top, pure conductive mode (α = 270 deg.). A computational 2D model based on the finite volume method is used for solving the mass, momentum and energy transfer governing equations. The simulation provides thermal and dynamic maps of the fluid for all configurations treated. The influence of Ra and α on the flow pattern and on the convective heat transfer are analysed and discussed. The thermal boundary distribution and the convective heat transfer calculated are, for most treated cases, close to those obtained experimentally by means of a simple bench specifically designed for this purpose. The maximum discrepancy between the simulations and measurements is relatively small, corresponding to the expected uncertainty of the model and measurements. The convective heat transfer is determined while calculating the radiative and conductive contributions to the global exchange. Radiation is determined by the radiosity method associated with the measured field of temperatures as well as to the global IR emissivities of all the internal elements of the cavity. The average Nusselt number Nu-bar is used to quantify the calculated convective contribution of the heat exchange within the cavity, and is compared with the measured value Nu-bar m . We

  15. Universality in quasiperiodic Rayleigh-Benard convection

    International Nuclear Information System (INIS)

    Ecke, R.E.; Mainieri, R.; Sullivan, T.S.

    1991-01-01

    We study universal scaling properties of quasiperiodic Rayleigh-Benard convection in a 3 He--superfluid- 4 He mixture. The critical line is located in a parameter space of Rayleigh and Prandtl numbers using a transient-Poincare-section technique to identify transitions from nodal periodic points to spiral periodic points within resonance horns. We measure the radial and angular contraction rates and extract the linear-stability eigenvalues (Flouquet multipliers) of the periodic point. At the crossings of the critical line with the lines of fixed golden-mean-tail winding number we determine the universality class of our experimental dynamics using f(α) and trajectory-scaling-function analyses. A technique is used to obtain a robust five-scale approximation to the universal trajectory scaling function. Different methods of multifractal analysis are employed and an understanding of statistical and systematic errors in these procedures is developed. The power law of the inflection point of the map, determined for three golden-mean-tail winding numbers, is 2.9±0.3, corresponding to the universality class of the sine map

  16. Kinetic thermal structure in turbulent Rayleigh-Bénard convection

    Science.gov (United States)

    Chen, Jun; Yin, Ze-Xia; She, Zhen-Su; Bao, Yun

    2017-11-01

    Plumes are believed to be the most important heat carrier in turbulent Rayleigh-Bénard convection (RBC). However, a physically sound and clear definition of plume is still absent. We report here the investigation of a definition of plume called kinetic thermal structure (KTS), based on the analysis of vertical velocity gradient (Λ = ∂w / ∂z), using direct numerical simulation (DNS) data of the three-dimensional RBC in a rectangular cell for Pr = 0.7 and Ra = 1 ×108 5 ×109 . It is shown that the conditional average of temperature on Λ exhibits such a behavior that when Λ is larger than a threshold, the volume carries a constant temperature of fluid, hence defines an unambiguous thermal structure, KTS. The DNS show that the KTS behaves in a sheet-like shape near the conducting plate, and becomes slender and smaller with increasing Ra . The heat flux carried by KTS displays a scaling law, with an exponent larger than the global- Nu - Ra scaling, indicating stronger heat transport than the turbulent background. An advantage of the KTS is its connection to the balance equation allowing, for the first time, a prediction of the Ra -dependence of its vertical velocity and the characteristic Λ threshold, validated by DNS. Supported by NSFC (11172006, 11221062, 11452002), and by MOST (China) 973 project (2009CB724100).

  17. Effect of Darcy, fluid Rayleigh and heat generation parameters on natural convection in a porous square enclosure: A Brinkman-extended Darcy model

    International Nuclear Information System (INIS)

    Das, S.; Sahoo, R.K.

    1999-01-01

    Analysis of flow and convective heat transfer in volumetrically heated porous layer has become a separate topic for research in the last twenty five years in view of its importance in various engineering applications, such as heat removal from nuclear fuel debris, heat transfer associated with storage of nuclear waste, exothermic reaction in packed-bed reactors, heat recovery from geothermal systems and particularly in the field of large storage systems of agricultural products. Here, a pressure-velocity solution for natural convection for fluid saturated heat generating porous medium in a square enclosure is analyzed by finite element method. The numerical solutions obtained for wide range of fluid Rayleigh number, Ra f , Darcy number, Da, and heat generating number, Q d . The justification for taking these non-dimensional parameters independently is to establish the effect of individual parameters on flow patterns. It has been observed that peak temperature occurs at the top central part and weaker velocity prevails near the vertical walls of the enclosure due to the heat generation parameter alone. On comparison, the modified Rayleigh number used by the earlier investigators, can not explain explicitly the effect of heat generation parameter on natural convection within an enclosure having differentially heated vertical walls. At higher Darcy number, the peak temperature and peak velocity are comparatively more, resulting in better enhancement of heat transfer rate

  18. 226Ra, 228Ra and 228Ra/226Ra in surface marine sediment of Malaysia

    International Nuclear Information System (INIS)

    Mei-Wo Yii; Zal Uyun Wan-Mahmood

    2013-01-01

    Surface sediment samples were collected at the West (east coast and west coast of Peninsular Malaysia) and East (Sabah and Sarawak) Malaysia in several expeditions within August 2003 until June 2008 for determining the level of natural radium isotopes. Activity concentrations of 226 Ra and 228 Ra in surface marine sediment at 176 sampling stations were measured. The activity concentrations of both radionuclides in Malaysia (East and West Malaysia) display varied with the range from 9 to 158 Bq/kg dry wt. and 13 to 104 Bq/kg dry wt., respectively. Meanwhile, the ratio distributions of 228 Ra/ 226 Ra were ranged from 0.62 to 3.75. This indicated that the ratios were slightly high at west coast of Peninsular Malaysia compared to other regions (east coast of Peninsular Malaysia, Sabah and Sarawak). The variation of activity concentrations of 226 Ra and 228 Ra and its ratios were also supported by the statistical analyses of one-way ANOVA and t test at 95 % confidence level, whereby there were proved that the measured values were different between the regions. These different were strictly related to their half-life, potential input sources (included their parents, 238 U and 232 Th), parent's characteristic, the geological setting/formation of the study area, environment origin and behavior. (author)

  19. Computational study of the Rayleigh light scattering properties of atmospheric pre-nucleation clusters

    DEFF Research Database (Denmark)

    Elm, Jonas; Norman, Patrick; Bilde, Merete

    2014-01-01

    The Rayleigh and hyper Rayleigh scattering properties of the binary (H 2SO4)(H2O)n and ternary (H 2SO4)(NH3)(H2O)n clusters are investigated using a quantum mechanical response theory approach. The molecular Rayleigh scattering intensities are expressed using the dipole polarizability α...... and hyperpolarizability β tensors. Using density functional theory, we elucidate the effect of cluster morphology on the scattering properties using a combinatorial sampling approach. We find that the Rayleigh scattering intensity depends quadratically on the number of water molecules in the cluster and that a single...... ammonia molecule is able to induce a high anisotropy, which further increases the scattering intensity. The hyper Rayleigh scattering activities are found to be extremely low. This study presents the first attempt to map the scattering of atmospheric molecular clusters using a bottom-up approach...

  20. Measuring the radium quartet (228Ra, 226Ra, 224Ra, 223Ra) in seawater samples using gamma spectrometry

    International Nuclear Information System (INIS)

    Beek, P. van; Souhaut, M.; Reyss, J.-L.

    2010-01-01

    Radium isotopes are widely used in marine studies (eg. to trace water masses, to quantify mixing processes or to study submarine groundwater discharge). While 228 Ra and 226 Ra are usually measured using gamma spectrometry, short-lived Ra isotopes ( 224 Ra and 223 Ra) are usually measured using a Radium Delayed Coincidence Counter (RaDeCC). Here we show that the four radium isotopes can be analyzed using gamma spectrometry. We report 226 Ra, 228 Ra, 224 Ra, 223 Ra activities measured using low-background gamma spectrometry in standard samples, in water samples collected in the vicinity of our laboratory (La Palme and Vaccares lagoons, France) but also in seawater samples collected in the plume of the Amazon river, off French Guyana (AMANDES project). The 223 Ra and 224 Ra activities determined in these samples using gamma spectrometry were compared to the activities determined using RaDeCC. Activities determined using the two techniques are in good agreement. Uncertainties associated with the 224 Ra activities are similar for the two techniques. RaDeCC is more sensitive for the detection of low 223 Ra activities. Gamma spectrometry thus constitutes an alternate method for the determination of short-lived Ra isotopes.

  1. Importance sampling the Rayleigh phase function

    DEFF Research Database (Denmark)

    Frisvad, Jeppe Revall

    2011-01-01

    Rayleigh scattering is used frequently in Monte Carlo simulation of multiple scattering. The Rayleigh phase function is quite simple, and one might expect that it should be simple to importance sample it efficiently. However, there seems to be no one good way of sampling it in the literature....... This paper provides the details of several different techniques for importance sampling the Rayleigh phase function, and it includes a comparison of their performance as well as hints toward efficient implementation....

  2. Effects of modulation on Rayleigh-Benard convection. Part I

    Directory of Open Access Journals (Sweden)

    B. S. Bhadauria

    2004-01-01

    Full Text Available The linear stability of a horizontal layer of fluid heated from below and above is considered. In addition to a steady temperature difference between the walls of the fluid layer, a time-dependent periodic perturbation is applied to the wall temperatures. Only infinitesimal disturbances are considered. Numerical results for the critical Rayleigh number are obtained at various Prandtl numbers and for various values of the frequency. Some comparisons have been made with the known results.

  3. Determination of 226Ra and 228Ra in gypsum

    International Nuclear Information System (INIS)

    Godoy, J.M.

    1989-01-01

    The content of 226 Ra and 228 Ra in different samples of phosphogypsum and three samples of gypsite were determined by gamma spectroscopy. For 226 Ra the 295, 352 and 609 KeV lines and for 228 Ra the 911 and 969 KeV lines were used. The specific activities values ranged from 0.36 to 22.8 pCi/g for 226 Ra and 0.90 to 10.3 pCi/g for 228 Ra. The contribution of a sypsum roof-covering to the 222 Rn concentration in a room was estimated, based on the highest value reported. (author) [pt

  4. Probability density function of the number of embryos collected from superovulated Nelore breed donors Função de densidade de probabilidade do número de embriões produzidos por doadoras da raça Nelore

    Directory of Open Access Journals (Sweden)

    Renato Travassos Beltrame

    2009-08-01

    Full Text Available Several models have been developed to evaluate reproductive status of cows through concentration of progesterone in milk, the effect of sex selection in the commercial production of herds and bioeconomic performance of the multiple ovulation and embryo transfer system in select herds. However, models describing the production of embryos in superovulated females have yet to be developed. A probability density function of the number of embryos collected by donors of the Nelore breed was determined. Records of 61,928 embryo collections from 26,767 donors from 1991 to 2005 were analyzed. Data were provided by the Brazilian Association of Creators of Zebu and Controlmax Consultoria e Sistemas Ltda. The probability density function of the number of viable embryos was modeled using exponential and gamma distributions. Parameter fitting was carried out for maximum likelihood using a non-linear gradient method. Both distributions presented similar level of precision: root mean square error (RMSE = 0.0072 and 0.0071 for the exponential and gamma distributions, respectively; both distributions are thus deemed suitable for representing the probability density function of embryo production by Nelore females.Diversos modelos têm sido desenvolvidos para avaliar o estado reprodutivo de vacas por meio da concentração de progesterona no leite, o efeito da seleção do sexo na produção comercial de rebanhos e o desempenho bioeconômico da ovulação múltipla e transferência de embriões em rebanhos selecionados. No entanto, modelos que descrevem a produção de embriões em fêmeas superovulados ainda têm de ser desenvolvidos. Uma função de densidade probabilidade para o número de embriões viáveis recuperados de doadoras da raça Nelore foi determinada. Dados de 61.928 coletas de 26.767 doadoras entre 1991 e 2005 foram analisados. Os resultados foram fornecidos pela Associação Brasileira de Criadores de Zebu (ABCZ e pela empresa Controlmax

  5. RAYLEIGH SCATTERING MODELS WITH CORRELATION INTEGRAL

    Directory of Open Access Journals (Sweden)

    S. F. Kolomiets

    2014-01-01

    Full Text Available This article offers one of possible approaches to the use of the classical correlation concept in Rayleigh scattering models. Classical correlation in contrast to three types of correlations corresponding to stochastic point flows opens the door to the efficient explanation of the interaction between periodical structure of incident radiation and discreet stochastic structure of distributed scatters typical for Rayleigh problems.

  6. Horizontal structures of velocity and temperature boundary layers in two-dimensional numerical turbulent Rayleigh-Bénard convection

    NARCIS (Netherlands)

    Zhou, Quan; Sugiyama, K.; Stevens, Richard Johannes Antonius Maria; Grossmann, Siegfried; Lohse, Detlef; Xia, K.

    2011-01-01

    We investigate the structures of the near-plate velocity and temperature profiles at different horizontal positions along the conducting bottom (and top) plate of a Rayleigh-Bénard convection cell, using two-dimensional (2D) numerical data obtained at the Rayleigh number Ra = 108 and the Prandtl

  7. New phenomena in variable-density Rayleigh-Taylor turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Livescu, D; Ristorcelli, J R; Petersen, M R; Gore, R A, E-mail: livescu@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2010-12-15

    This paper presents several issues related to mixing and turbulence structure in buoyancy-driven turbulence at low to moderate Atwood numbers, A, found from direct numerical simulations in two configurations: classical Rayleigh-Taylor instability and an idealized triply periodic Rayleigh-Taylor flow. Simulations at A up to 0.5 are used to examine the turbulence characteristics and contrast them with those obtained close to the Boussinesq approximation. The data sets used represent the largest simulations to date in each configuration. One of the more remarkable issues explored, first reported in (Livescu and Ristorcelli 2008 J. Fluid Mech. 605 145-80), is the marked difference in mixing between different density fluids as opposed to the mixing that occurs between fluids of commensurate densities, corresponding to the Boussinesq approximation. Thus, in the triply periodic configuration and the non-Boussinesq case, an initially symmetric density probability density function becomes skewed, showing that the mixing is asymmetric, with pure heavy fluid mixing more slowly than pure light fluid. A mechanism producing the mixing asymmetry is proposed and the consequences for the classical Rayleigh-Taylor configuration are discussed. In addition, it is shown that anomalous small-scale anisotropy found in the homogeneous configuration (Livescu and Ristorcelli 2008 J. Fluid Mech. 605 145-80) and Rayleigh-Taylor turbulence at A=0.5 (Livescu et al 2008 J. Turbul. 10 1-32) also occurs near the Boussinesq limit. Results pertaining to the moment closure modelling of Rayleigh-Taylor turbulence are also presented. Although the Rayleigh-Taylor mixing layer width reaches self-similar growth relatively fast, the lower-order terms in the self-similar expressions for turbulence moments have long-lasting effects and derived quantities, such as the turbulent Reynolds number, are slow to follow the self-similar predictions. Since eddy diffusivity in the popular gradient transport hypothesis

  8. RADIATIVE RAYLEIGH-TAYLOR INSTABILITIES

    International Nuclear Information System (INIS)

    Jacquet, Emmanuel; Krumholz, Mark R.

    2011-01-01

    We perform analytic linear stability analyses of an interface separating two stratified media threaded by a radiation flux, a configuration relevant in several astrophysical contexts. We develop a general framework for analyzing such systems and obtain exact stability conditions in several limiting cases. In the optically thin, isothermal regime, where the discontinuity is chemical in nature (e.g., at the boundary of a radiation pressure-driven H II region), radiation acts as part of an effective gravitational field, and instability arises if the effective gravity per unit volume toward the interface overcomes that away from it. In the optically thick a diabaticregime where the total (gas plus radiation) specific entropy of a Lagrangian fluid element is conserved, for example at the edge of radiation pressure-driven bubble around a young massive star, we show that radiation acts like a modified equation of state and derive a generalized version of the classical Rayleigh-Taylor stability condition.

  9. RA reactor building and installations; Zgrada 'RA' i instalacije

    Energy Technology Data Exchange (ETDEWEB)

    Badrljica, R; Sanovic, V; Skoric, M [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1985-08-15

    RA reactor building is made of reinforced concrete and bricks. It is closed facility with a limited number of controlled openings, doors and windows. The site of the building is 100 m above the sea level, 20 m above the mean Danube level and 8 m above the level of the neighbouring stream Mlaka. The building consists of three parts: central prismatic part, annex - surrounding the central part and the sanitary corridor. The biggest space is the reactor hall. In addition to the detailed description and drawings of the reactor building this documents includes design specifications of: electrical installation, water supply system, sewage system, ventilation and heating, gas and compressed air systems. A separate chapter is devoted to fire protection. Zgrada reaktora RA izgradjena je od armiranog betona i opeke, kao zatvoreni objekat ogranicenog broja kontolisanih otvora, sa ogranicenim brojem vrata i prozora. Plato na kojem je zgrada izgradjena nalazi se na 100 m nadmorske visine, na 20 m iznad srednjeg vodostaja Dunava i 8 m iznad nivoa obliznjeg potoka Mlaka. Zgrada se sastoji iz tri dela: sredisnjeg prizmaticnog dela, aneksa - prstenastog okvira sredisnog dela i sanitarnog propusnika. Pojedinacno najveci prostor zauzima reaktorska hala. Pored detaljnog opisa i plana zgrade, ovaj dokument sadrzi projekat elektricne instalacije, projekat vodovoda i kanalizacije, ventilacije i grejanja, instalacije gasa i komprimovanog vazduha. Posebno poglavlje posveceno je protivpozarnoj zastiti.

  10. Direct numerical simulation of the Rayleigh-Taylor instability with the spectral element method

    International Nuclear Information System (INIS)

    Zhang Xu; Tan Duowang

    2009-01-01

    A novel method is proposed to simulate Rayleigh-Taylor instabilities using a specially-developed unsteady three-dimensional high-order spectral element method code. The numerical model used consists of Navier-Stokes equations and a transport-diffusive equation. The code is first validated with the results of linear stability perturbation theory. Then several characteristics of the Rayleigh-Taylor instabilities are studied using this three-dimensional unsteady code, including instantaneous turbulent structures and statistical turbulent mixing heights under different initial wave numbers. These results indicate that turbulent structures of Rayleigh-Taylor instabilities are strongly dependent on the initial conditions. The results also suggest that a high-order numerical method should provide the capability of simulating small scale fluctuations of Rayleigh-Taylor instabilities of turbulent flows. (authors)

  11. Short Rayleigh Length Free Electron Lasers

    CERN Document Server

    Crooker, P P; Armstead, R L; Blau, J

    2004-01-01

    Conventional free electron laser (FEL) oscillators minimize the optical mode volume around the electron beam in the undulator by making the resonator Rayleigh length about one third of the undulator length. This maximizes gain and beam-mode coupling. In compact configurations of high-power infrared FELs or moderate power UV FELs, the resulting optical intensity can damage the resonator mirrors. To increase the spot size and thereby reduce the optical intensity at the mirrors below the damage threshold, a shorter Rayleigh length can be used, but the FEL interaction is significantly altered. A new FEL interaction is described and analyzed with a Rayleigh length that is only one tenth the undulator length, or less. The effect of mirror vibration and positioning are more critical in the short Rayleigh length design, but we find that they are still within normal design tolerances.

  12. Chemical Applications of Second Harmonic Rayleigh Scattering ...

    Indian Academy of Sciences (India)

    Chemical Applications of Second Harmonic Rayleigh Scattering Puspendu Kumar Das Department of Inorganic and Physical Chemistry Indian Institute of Science Bangalore 560012, India pkdas@ipc.iisc.ernet.in.

  13. Rayleigh-Taylor mixing in supernova experiments

    International Nuclear Information System (INIS)

    Swisher, N. C.; Abarzhi, S. I.; Kuranz, C. C.; Arnett, D.; Hurricane, O.; Remington, B. A.; Robey, H. F.

    2015-01-01

    We report a scrupulous analysis of data in supernova experiments that are conducted at high power laser facilities in order to study core-collapse supernova SN1987A. Parameters of the experimental system are properly scaled to investigate the interaction of a blast-wave with helium-hydrogen interface, and the induced Rayleigh-Taylor instability and Rayleigh-Taylor mixing of the denser and lighter fluids with time-dependent acceleration. We analyze all available experimental images of the Rayleigh-Taylor flow in supernova experiments and measure delicate features of the interfacial dynamics. A new scaling is identified for calibration of experimental data to enable their accurate analysis and comparisons. By properly accounting for the imprint of the experimental conditions, the data set size and statistics are substantially increased. New theoretical solutions are reported to describe asymptotic dynamics of Rayleigh-Taylor flow with time-dependent acceleration by applying theoretical analysis that considers symmetries and momentum transport. Good qualitative and quantitative agreement is achieved of the experimental data with the theory and simulations. Our study indicates that in supernova experiments Rayleigh-Taylor flow is in the mixing regime, the interface amplitude contributes substantially to the characteristic length scale for energy dissipation; Rayleigh-Taylor mixing keeps order

  14. Estuarine geochemistry of 224Ra, 226Ra, and 222Rn

    International Nuclear Information System (INIS)

    Elsinger, R.J.

    1982-01-01

    Desorption from river borne sediments is the most likely source of the excess 226 Ra. Laboratory mixing experiments on Pee Dee River sediments show an increase in 226 Ra desorption with increasing salinities with maximum desorption occurring at or above 20 0 /oo salinity. Desorption and diffusion are the sources for 226 Ra in the estuarine systems. In Winyah Bay the 228 Ra/ 226 Ra activity ratio does not change significantly with salinity, averaging around 1.4, indicating desorption as the major source of 228 Ra. In the Yangtze River the 228 Ra/ 226 Ra activity ratio is constant (approx.1.90) until increasing linearly above 16 0 /oo. A diffusive flux from regeneration by 232 Th decay in shelf sediments is the source of the increase. In Delaware Bay 228 Ra increases faster than 226 Ra in the less than or equal to22 0 /oo water, indicating a source in addition to desorption. The increase can be balanced by a 0.33 dpm/cm 2 -year flux over the upper part of the Bay where fine grained sediments predominate. 224 Ra behavior is controlled by its 3.64 day half-life. In Winyah Bay a flux of around 0.4 dpm/cm 2 -day is necessary to support the standing crop of non-desorbed 224 Ra in the water column. In Delaware Bay the nearly constant 224 Ra in concentration over the 2.5 0 /oo to 12 0 /oo salinity range are maintained by regeneration from 228 Th in the turbidity maximum zones and diffusion from bottom sediments. Water leaving on ebb tide from a salt marsh on Delaware Bay had increases in all three radium isotopes ( 224 Ra > 228 Ra > 226 Ra) compared to water coming in on the flood tide. Excess 222 Rn concentrations in a fresh water section of the Pee Dee River show a decreasing downstream gradient. Using these gradients to determine evasion rates, stagnant film thicknesses range from 21μ to 62μ

  15. Modeling of Rayleigh wave dispersion in Iberia

    Directory of Open Access Journals (Sweden)

    José Badal

    2011-01-01

    Full Text Available Phase and group velocities of 15–70 s Rayleigh waves propagating across the Iberian Peninsula have been transformed into local dispersion curves by linear inversion of travel times. The procedure permits that the waveform dispersion to be obtained as a continuous period-dependent velocity function at grid points belonging to the area probed by the waves, thus providing phase- and group-velocity contour maps for several periods within the interval of interest. The regionalization process rests on a homogeneous initial data set in which the number of observations remains almost constant for all periods of reference. Damped least-squares inversion of the local dispersion curves for shear-wave velocity structure is performed to obtain depth-dependent S-wave velocity profiles at the grid points covering the model region. The reliability of the results should improve significantly owing to the use of phase and group velocities simultaneously. On this basis, we have built horizontal depth sections that give an updated view of the seismic velocity structure of the peninsula at lithospheric and upper mantle depths (20–200 km. After averaging all the pure-path S-wave velocities previously determined at each grid point, the velocity-depth models so obtained for major tectonic units allow the comparison between the Hercynian basement and other areas of Mesozoic folding and Tertiary basins.

  16. Manipulating Rayleigh-Taylor Growth Using Adjoints

    Science.gov (United States)

    Kord, Ali; Capecelatro, Jesse

    2017-11-01

    It has been observed that initial interfacial perturbations affect the growth of Rayleigh-Taylor (RT) instabilities. However, it remains to be seen to what extent the perturbations alter the RT growth rate. Direct numerical simulations (DNS) provide a powerful means for studying the effects of initial conditions (IC) on the growth rate. However, a brute-force approach for identifying optimal initial perturbations is not practical via DNS. In addition, identifying sensitivity of the RT growth to the large number of parameters used in defining the IC is computationally expensive. A discrete adjoint is formulated to measure sensitivities of multi-mode RT growth to ICs in a high-order finite difference framework. The sensitivity is used as a search direction for adjusting the initial perturbations to both maximize and suppress the RT growth rate during its non-linear regime. The modes that contribute the greatest sensitivity are identified, and optimized perturbation energy spectrum are reported. PhD Student, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI.

  17. Feedback control and heat transfer measurements in a Rayleigh-Bénard convection cell

    Science.gov (United States)

    Vial, M.; Hernández, R. H.

    2017-07-01

    We report experimental results on the heat transfer and instability onset of a Rayleigh-Bénard convection cell of aspect ratios 6:3:1 filled with a high Prandtl aqueous solution of glycerol under feedback control. We investigate the transient and stationary response of both local temperature readings and heat transfer fluxes on the Rayleigh Bénard cell in both conductive and convective states when we perform two independent feedback control actions on both hot and cold walls. We evaluate the performance of both controllers to maintain a temperature gradient independently if the system is below or above the convection threshold. As the convection cell can be rotated at 180° about the shorter axis of the cell, it was possible to perform transitions between thermal conduction and convection regimes and vice versa under a constant temperature difference maintained by both independent controllers. The experimental setup provided an accurate measurement of the critical Rayleigh number and the evolution of the Nusselt number as a function of the Rayleigh number in the moderately supercritical regime (R a cellular convection pattern formed by 6 transverse rolls throughout the range of Rayleigh numbers.

  18. Effect of periodic bottom plate heating on large scale flow in turbulent Rayleigh-Bénard convection

    Czech Academy of Sciences Publication Activity Database

    Kuqali, M.; Babuin, Simone; Niemela, J.J.

    2015-01-01

    Roč. 8, č. 3 (2015), 483-489 ISSN 1735-3572 Institutional support: RVO:68378271 Keywords : Rayleigh-Bénard convection * Reynolds number Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.888, year: 2015

  19. A priori study of subgrid-scale features in turbulent Rayleigh-Bénard convection

    Science.gov (United States)

    Dabbagh, F.; Trias, F. X.; Gorobets, A.; Oliva, A.

    2017-10-01

    At the crossroad between flow topology analysis and turbulence modeling, a priori studies are a reliable tool to understand the underlying physics of the subgrid-scale (SGS) motions in turbulent flows. In this paper, properties of the SGS features in the framework of a large-eddy simulation are studied for a turbulent Rayleigh-Bénard convection (RBC). To do so, data from direct numerical simulation (DNS) of a turbulent air-filled RBC in a rectangular cavity of aspect ratio unity and π spanwise open-ended distance are used at two Rayleigh numbers R a ∈{1 08,1 010 } [Dabbagh et al., "On the evolution of flow topology in turbulent Rayleigh-Bénard convection," Phys. Fluids 28, 115105 (2016)]. First, DNS at Ra = 108 is used to assess the performance of eddy-viscosity models such as QR, Wall-Adapting Local Eddy-viscosity (WALE), and the recent S3PQR-models proposed by Trias et al. ["Building proper invariants for eddy-viscosity subgrid-scale models," Phys. Fluids 27, 065103 (2015)]. The outcomes imply that the eddy-viscosity modeling smoothes the coarse-grained viscous straining and retrieves fairly well the effect of the kinetic unfiltered scales in order to reproduce the coherent large scales. However, these models fail to approach the exact evolution of the SGS heat flux and are incapable to reproduce well the further dominant rotational enstrophy pertaining to the buoyant production. Afterwards, the key ingredients of eddy-viscosity, νt, and eddy-diffusivity, κt, are calculated a priori and revealed positive prevalent values to maintain a turbulent wind essentially driven by the mean buoyant force at the sidewalls. The topological analysis suggests that the effective turbulent diffusion paradigm and the hypothesis of a constant turbulent Prandtl number are only applicable in the large-scale strain-dominated areas in the bulk. It is shown that the bulk-dominated rotational structures of vortex-stretching (and its synchronous viscous dissipative structures) hold

  20. 226Ra, 228Ra, 223Ra, and 224Ra in coastal waters with application to coastal dynamics and groundwater input

    International Nuclear Information System (INIS)

    Moore, W.S.

    1997-01-01

    Four radium isotopes offer promise in unraveling the complex dynamics of coastal ocean circulation and groundwater input. Each isotope is produced by decay of a thorium parent bound to sediment. The activities of these thorium isotopes and the sediment-water distribution coefficient for radium provide an estimate of the source function of each Ra isotope to the water. In salt marshes that receive little surface water input, Ra activities which exceed coastal ocean values must originate within the marsh. In North Inlet, South Carolina, the activities of 226 Ra exported from the marsh far exceed the activities generated within the marsh. To supply the exported activities, substantial groundwater input is required. In the coastal region itself, 226 Ra activities exceed the amount that can be supplied from rivers. Here also, substantial groundwater input is required. Within the coastal ocean, 223 Ra and 224 Ra may be used to determine mixing rates with offshore waters. Shore-perpendicular profiles of 223 Ra and 224 Ra show consistent trends which may be modeled as eddy diffusion coefficients of 350-540 m 2 s -1 . These coefficients allow an assessment of cross-shelf transport and provide further insight on the importance of groundwater to coastal regions. (author)

  1. Determination of Love- and Rayleigh-Wave Magnitudes for Earthquakes and Explosions and Other Studies

    Science.gov (United States)

    2012-12-30

    09-C-0012 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62601F 6. AUTHOR(S) Jessie L. Bonner, Anastasia Stroujkova, Dale Anderson, Jonathan...AND RAYLEIGH-WAVE MAGNITUDES FOR EARTHQUAKES AND EXPLOSIONS Jessie L. Bonner, Anastasia Stroujkova, and Dale Anderson INTRODUCTION Since...MAXIMUM LIKELIHOOD ESTIMATION: APPLICATION TO MIDDLE EAST EARTHQUAKE DATA Anastasia Stroujkova and Jessie Bonner Weston Geophysical Corporation

  2. Rayleigh scattering from ions near threshold

    International Nuclear Information System (INIS)

    Roy, S.C.; Gupta, S.K.S.; Kissel, L.; Pratt, R.H.

    1988-01-01

    Theoretical studies of Rayleigh scattering of photons from neon atoms with different degrees of ionization, for energies both below and above the K-edges of the ions, are presented. Some unexpected structures both in Rayleigh scattering and in photoionization from neutral and weakly ionized atoms, very close to threshold, have been reported. It has recently been realized that some of the predicted structures may have a nonphysical origin and are due to the limitation of the independent-particle model and also to the use of a Coulombic Latter tail. Use of a K-shell vacancy potential - in which an electron is assumed to be removed from the K-shell - in calculating K-shell Rayleigh scattering amplitudes removes some of the structure effects near threshold. We present in this work a discussion of scattering angular distributions and total cross sections, obtained utilizing vacancy potentials, and compare these predictions with those previously obtained in other potential model. (author) [pt

  3. Chromo-Rayleigh interactions of dark matter

    International Nuclear Information System (INIS)

    Bai, Yang; Osborne, James

    2015-01-01

    For a wide range of models, dark matter can interact with QCD gluons via chromo-Rayleigh interactions. We point out that the Large Hadron Collider (LHC), as a gluon machine, provides a superb probe of such interactions. In this paper, we introduce simplified models to UV-complete two effective dark matter chromo-Rayleigh interactions and identify the corresponding collider signatures, including four jets or a pair of di-jet resonances plus missing transverse energy. After performing collider studies for both the 8 TeV and 14 TeV LHC, we find that the LHC can be more sensitive to dark matter chromo-Rayleigh interactions than direct detection experiments and thus provides the best opportunity for future discovery of this class of models.

  4. Bivariate Rayleigh Distribution and its Properties

    Directory of Open Access Journals (Sweden)

    Ahmad Saeed Akhter

    2007-01-01

    Full Text Available Rayleigh (1880 observed that the sea waves follow no law because of the complexities of the sea, but it has been seen that the probability distributions of wave heights, wave length, wave induce pitch, wave and heave motions of the ships follow the Rayleigh distribution. At present, several different quantities are in use for describing the state of the sea; for example, the mean height of the waves, the root mean square height, the height of the “significant waves” (the mean height of the highest one-third of all the waves the maximum height over a given interval of the time, and so on. At present, the ship building industry knows less than any other construction industry about the service conditions under which it must operate. Only small efforts have been made to establish the stresses and motions and to incorporate the result of such studies in to design. This is due to the complexity of the problem caused by the extensive variability of the sea and the corresponding response of the ships. Although the problem appears feasible, yet it is possible to predict service conditions for ships in an orderly and relatively simple manner Rayleigh (1980 derived it from the amplitude of sound resulting from many independent sources. This distribution is also connected with one or two dimensions and is sometimes referred to as “random walk” frequency distribution. The Rayleigh distribution can be derived from the bivariate normal distribution when the variate are independent and random with equal variances. We try to construct bivariate Rayleigh distribution with marginal Rayleigh distribution function and discuss its fundamental properties.

  5. Effect of polarization fatigue on the Rayleigh coefficients of ferroelectric lead zirconate titanate thin films: Experimental evidence and implications

    Science.gov (United States)

    Lou, X. J.; Zhang, H. J.; Luo, Z. D.; Zhang, F. P.; Liu, Y.; Liu, Q. D.; Fang, A. P.; Dkhil, B.; Zhang, M.; Ren, X. B.; He, H. L.

    2014-09-01

    The effect of polarization fatigue on the Rayleigh coefficients of ferroelectric lead zirconate titanate (PZT) thin film was systematically investigated. It was found that electrical fatigue strongly affects the Rayleigh behaviour of the PZT film. Both the reversible and irreversible Rayleigh coefficients decrease with increasing the number of switching cycles. This phenomenon is attributed to the growth of an interfacial degraded layer between the electrode and the film during electrical cycling. The methodology used in this work could serve as an alternative way for evaluating the fatigue endurance and degradation in dielectric properties of ferroelectric thin-film devices during applications.

  6. Attractors of the periodically forced Rayleigh system

    Directory of Open Access Journals (Sweden)

    Petre Bazavan

    2011-07-01

    Full Text Available The autonomous second order nonlinear ordinary differential equation(ODE introduced in 1883 by Lord Rayleigh, is the equation whichappears to be the closest to the ODE of the harmonic oscillator withdumping.In this paper we present a numerical study of the periodic andchaotic attractors in the dynamical system associated with the generalized Rayleigh equation. Transition between periodic and quasiperiodic motion is also studied. Numerical results describe the system dynamics changes (in particular bifurcations, when the forcing frequency is varied and thus, periodic, quasiperiodic or chaotic behaviour regions are predicted.

  7. Hydromagnetic Rayleigh-Taylor instability in cylindrical implosions

    International Nuclear Information System (INIS)

    Hwang, C.S.; Roderick, N.F.; Wu, M.W.

    1986-01-01

    Rayleigh-Taylor Instability in the (r,Θ) plane has been solved by the variational approach. Results are compared to the analytical solutions of two-region and three-region problems at the infinite radius. They show the magnetic stabilization effect. Growth rates in this plane are decreased by the effects of plasma shell thickness, plasma shell radius, magnetic tension, magnetic diffusion and finite density gradient of the plasma magnetic field interface. The most unstable mode number decreases when the radius of the plasma shell decreases

  8. RA reactor operation and maintenance; Pogon i odrzavanje reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    Zecevic, V [Institute of Nuclear Sciences Boris Kidric, Reaktor RA, Vinca, Beograd (Serbia and Montenegro)

    1963-02-15

    This volume includes the final report on RA reactor operation and utilization of the experimental facilities in 1962, detailed analysis of the system for heavy water distillation and calibration of the system for measuring the activity of the air.

  9. Effect of Rayleigh accelerations applied to an initially moving fluid. [in circular cylinders under low gravity associated with space flight

    Science.gov (United States)

    Dressler, R. F.; Robertson, S. J.; Spradley, L. W.

    1982-01-01

    The General Interpolant Method computer code was used to analyze two-dimensional unsteady thermal convection in circular cylinders under variable low-g conditions associated with space flight. When an acceleration vector was applied parallel to the thermal gradient, in the case of a fluid at rest, no convection resulted for the stable direction, and an instability led to Rayleigh convection for the opposite direction. However, when the acceleration had a component orthogonal to the gradient, convection resulted at any Rayleigh number. The effect on convection of both types of acceleration, applied concurrently or sequentially, was investigated, including the case when the resultant vector varied in direction with time. An analysis of experimental results shows that for space flight conditions, the Rayleigh accelerations induce significant, but not dominating, changes in the established convection even when the Rayleigh number is less than critical.

  10. Research nuclear reactor RA - Annual Report 1991

    International Nuclear Information System (INIS)

    Sotic, O.

    1992-01-01

    Activities related to revitalisation of the RA reactor stared in 1986, were continued in 1991. A number of interventions on the reactor components were finished that are supposed to enable continuous and reliable operation. The last, and at the same time largest action, related to exchange of complete reactor instrumentation is underway, but it is behind the schedule in 1991 because the delivery of components from USSR is late. Production of this instruments is financed by the IAEA according to the contract signed in December 1988 with Russian Atomenergoexport. According to this contract, it has been planned that the RA reactor instrumentation should be delivered to the Vinca Institute by the end of 1990. Only 56% of the instrumentation was delivered until September 1991. Since then any delivery of components to Yugoslavia was stopped because of the temporary embargo imposed by the IAEA. In 1991 most of the existing RA reactor instrumentation was dismantled, only the part needed for basic measurements when reactor is not operated, was maintained. Construction of some support elements is almost finished by the local staff. The Institute has undertaken this activity in order to speed up the ending of the project. If all the planned instrumentation would not arrive until the end of March 1992, it would not be possible to start the RA reactor testing operation in the first part of 1993, as previously planned. In 1991, 53 staff members took part in the activities during 1991, which is considered sufficient for maintenance and repair conditions. Research reactor RA Annual report for year 1991 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection [sr

  11. Research nuclear reactor RA - Annual Report 1994

    International Nuclear Information System (INIS)

    Sotic, O.

    1994-12-01

    Activities related to revitalisation of the RA reactor stared in 1986, were continued in 1991. A number of interventions on the reactor components were finished that are supposed to enable continuous and reliable operation. The last, and at the same time largest action, related to exchange of complete reactor instrumentation is underway, but it is behind the schedule in 1991 because the delivery of components from USSR is late. Production of this instruments is financed by the IAEA according to the contract signed in December 1988 with Russian Atomenergoexport. According to this contract, it has been planned that the RA reactor instrumentation should be delivered to the Vinca Institute by the end of 1990. Only 56% of the instrumentation was delivered until September 1991. Since then any delivery of components to Yugoslavia was stopped because of the temporary embargo imposed by the IAEA. In 1991 most of the existing RA reactor instrumentation was dismantled, only the part needed for basic measurements when reactor is not operated, was maintained. Activities related to improvement of Russian project were continued in 1994. Control and maintenance of the reactor components was done regularly and efficiently. Extensive repair of the secondary coolant loop is almost finished and will be completed in the first part of 1995 according to existing legal procedures and IAEA recommendations. Fuel inspection by the IAEA safeguards inspectors was done on a monthly basis. There have been on the average 47 employees at the RA reactor which is considered sufficient for maintenance and repair conditions. Research reactor RA Annual report for year 1991 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection [sr

  12. First measurement of the Rayleigh cross section

    NARCIS (Netherlands)

    Naus, H.; Ubachs, W.

    2000-01-01

    Rayleigh cross section for N2, Ar and SF6 was performed using the technique of cavity ring-down spectroscopy (CRDS). The experiment was based on the assumption that scattering cross section is equal to the extinction in the absence of absorption. The theory explains the molecular origin of

  13. Rayleigh scattering in coupled microcavities: theory.

    Science.gov (United States)

    Vörös, Zoltán; Weihs, Gregor

    2014-12-03

    In this paper we theoretically study how structural disorder in coupled semiconductor heterostructures influences single-particle scattering events that would otherwise be forbidden by symmetry. We extend the model of Savona (2007 J. Phys.: Condens. Matter 19 295208) to describe Rayleigh scattering in coupled planar microcavity structures, and find that effective filter theories can be ruled out.

  14. RA reactor operation and maintenance

    International Nuclear Information System (INIS)

    Zecevic, V.

    1963-02-01

    This volume includes the final report on RA reactor operation and utilization of the experimental facilities in 1962, detailed analysis of the system for heavy water distillation and calibration of the system for measuring the activity of the air

  15. Measurements at the RA Reactor related to the VISA-2 project - Part 1, Start-up of the RA reactor and measurement of new RA reactor core parameters

    International Nuclear Information System (INIS)

    Markovic, H.

    1962-07-01

    The objective of the measurements was determining the neutron flux in the RA reactor core. Since the number of fuel channels is increased from 56 to 68 within the VISA-2 project, it was necessary to attain criticality of the RA reactor and measure the neutron flux properties. The 'program of RA reactor start-up' has been prepared separately and it is included in this report. Measurements were divided in two phases. First phase was measuring of the neutron flux after the criticality was achieved but at zero power. During phase two measurements were repeated at several power levels, at equilibrium xenon poisoning. This report includes experimental data of flux distributions and absolute values of the thermal and fast neutron flux in the RA reactor experimental channels and values of cadmium ratio for determining the neutron epithermal flux. Data related to calibration of regulatory rods for cold un poisoned core are included [sr

  16. Measurement of the Rayleigh-Taylor instability in targets driven by optically smoothed laser beams

    International Nuclear Information System (INIS)

    Desselberger, M.; Willi, O.; Savage, M.; Lamb, M.J.

    1990-01-01

    Growth rates of the Rayleigh-Taylor instability were measured in targets with imposed sinusoidal modulations irradiated by optically smoothed 0.53-μm laser beams. A hybrid optical smoothing technique utilizing induced-spatial-incoherence and random-phase-plate technology was used for the first time. The wave-number dependence and the nonlinear behavior of Rayleigh-Taylor growth were investigated by using targets with a range of modulation periodicities and depths. The results are compared to 2D hydrodynamic-code simulations

  17. Size invariance of the granular Rayleigh-Taylor instability.

    Science.gov (United States)

    Vinningland, Jan Ludvig; Johnsen, Øistein; Flekkøy, Eirik G; Toussaint, Renaud; Måløy, Knut Jørgen

    2010-04-01

    The size scaling behavior of the granular Rayleigh-Taylor instability [J. L. Vinningland, Phys. Rev. Lett. 99, 048001 (2007)] is investigated experimentally, numerically, and theoretically. An upper layer of grains displaces a lower gap of air by organizing into dense fingers of falling grains separated by rising bubbles of air. The dependence of these structures on the system and grain sizes is investigated. A spatial measurement of the finger structures is obtained by the Fourier power spectrum of the wave number k. As the size of the grains increases the wave number decreases accordingly which leaves the dimensionless product of wave number and grain diameter, dk, invariant. A theoretical interpretation of the invariance, based on the scaling properties of the model equations, suggests a gradual breakdown of the invariance for grains smaller than approximately 70 microm or greater than approximately 570 microm in diameter.

  18. Safety shutdowns and failures of the RA reactor equipment; Sigurnosna zaustavljanja i kvarovi opreme na reaktoru RA

    Energy Technology Data Exchange (ETDEWEB)

    Mitrovic, S [Institut za nuklearne nauke ' Boris Kidric' , Vinca, Belgrade (Yugoslavia)

    1966-07-01

    This report is an attempt of statistical analysis of the failures occurred during RA reactor operation. A list of failures occurred on the RA equipment during 1965 is included. Failures were related to the following systems: dosimetry system (22%), safety and control system (7%), heavy water system (2%), technical water (4%), helium system (2%), measuring instruments (30%), transport, ventilation, power supply systems (32%). A review of safety shutdowns from 1962 to 1966 is included as well, as a comparison with three similar reactors. Although the number of events used for statistical analysis was not adequate, it has been concluded that RA reactor operation was stable and reliable.

  19. Automated measurement of 224Ra and 226Ra in water

    International Nuclear Information System (INIS)

    Dimova, N.; Burnett, W.C.; Horwitz, E.P.; Lane-Smith, D.

    2007-01-01

    We present a new simple approach for automated, non-destructive measurement of the alpha-emitting radium isotopes ( 223 Ra, 224 Ra, and 226 Ra) in water based on the emanation of their respective radon daughters ( 219 Rn, 220 Rn, and 222 Rn). The method combines the high adsorption uptake of MnO 2 Resin for radium (K d =2.4x10 4 ml/g) over a wide pH range with the simplicity of the activity registration using a commercial radon-in-air analyzer (RAD7, DURRIDGE Company, Inc). Radium is first adsorbed onto the MnO 2 Resin by passing a water sample through the resin packed in a gas-tight glass cartridge. The same cartridge is then connected to the radon analyzer via a simple tubing system to circulate air through the resin and a drying system. The efficiency of the proposed system is determined by running standards prepared in the same manner. Our results indicate that the efficiency for 226 Ra is >22% if both 218 Po and 214 Po counts are collected. This is comparable with typical efficiencies for alpha spectrometry but with much less sample preparation. We estimate that an MDA of 0.8 pCi/L for 226 Ra may be obtained with this new approach using a 1 L water sample and less than 4 h of counting

  20. Three-dimensional Rayleigh-Taylor convection of miscible fluids in a porous medium

    Science.gov (United States)

    Suekane, Tetsuya; Nakanishi, Yuji; Wang, Lei

    2017-11-01

    Natural convection of miscible fluids in a porous medium is relevant for fields, such as geoscience and geoengineering, and for the geological storage of CO2. In this study, we use X-ray computer tomography to visualize 3D fingering structures associated with the Rayleigh-Taylor instability between miscible fluids in a porous medium. In the early stages of the onset of the Rayleigh-Taylor instability, a fine crinkling pattern gradually appears at the interface. As the wavelength and amplitude increase, descending fingers form on the interface and extend vertically downward; moreover, ascending and highly symmetric fingers form. The adjacent fingers are cylindrical in shape and coalesce to form large fingers. Fingers appearing on the interface tend to become finer with increasing Rayleigh number, which is consistent with linear perturbation theory. If the Péclet number exceeds 10, the transverse dispersion increases the finger diameter and enhances finger coalescence, strongly impacting the decay in finger number density. When mechanical dispersion is negligible, the finger-extension velocity, the mass-transfer rate, and the onset time scale with Rayleigh number. Mechanical dispersion not only reduces the onset time but also enhances mass transport, which indicates that mechanical dispersion influences the long-term dissolution process of CO2 injected into aquifers.

  1. Effect of plumes on measuring the large scale circulation in turbulent Rayleigh-Bénard convection

    NARCIS (Netherlands)

    Stevens, Richard Johannes Antonius Maria; Clercx, H.J.H.; Lohse, Detlef

    2011-01-01

    We studied the properties of the large-scale circulation (LSC) in turbulent Rayleigh-Bénard (RB) convection by using results from direct numerical simulations in which we placed a large number of numerical probes close to the sidewall. The LSC orientation is determined by either a cosine or a

  2. Experimental determination of heat transfer in a Poiseuille-Rayleigh-Bénard flow

    Science.gov (United States)

    Taher, R.; Abid, C.

    2018-05-01

    This paper deals with an experimental study of heat transfer in a Poiseuille-Rayleigh-Bénard flow. This situation corresponds to a mixed convection phenomenon in a horizontal rectangular channel uniformly heated from below. Flow visualisation and temperature measurements were achieved in order to describe the flow regimes and heat transfer behaviour. The classical measurement techniques such employing thermocouples give local measurement on one hand and on other hand they often disturb the flow. As the flow is three-dimensional, these techniques are not efficient. In order to not disturb the flow, a non-intrusive method is used for thermal measurement. The Planar laser Induced Fluorescence (PLIF) was implemented to determine thermal fields in the fluid. Experiments conducted for various Reynolds and Rayleigh numbers allow to determine the heat transfer and thus to propose correlation for Nusselt number for a mixed convection flow in Poiseuille-Rayleigh-Bénard configuration. First a description of the use of this technique in water flow is presented and then the obtained results for various Reynolds and Rayleigh numbers allow to propose a correlation for the Nusselt number for such configuration of mixed convection. The comparison between the obtained heat transfer and the pure forced convection one confirms the well-known result that the convective heat transfer is greatly enhanced in mixed convection. Indeed, secondary flow induced by buoyant forces contributes to the refreshment of thermal boundary layers and so acts like mixers, which significantly enhances heat transfer.

  3. Measuring the radium quartet ({sup 228}Ra, {sup 226}Ra, {sup 224}Ra, {sup 223}Ra) in seawater samples using gamma spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Beek, P. van, E-mail: vanbeek@legos.obs-mip.f [LEGOS, Laboratoire d' Etudes en Geophysique et Oceanographie Spatiales (CNRS/CNES/IRD/UPS), Observatoire Midi Pyrenees, 14 Avenue Edouard Belin, 31400 Toulouse (France); Souhaut, M. [LEGOS, Laboratoire d' Etudes en Geophysique et Oceanographie Spatiales (CNRS/CNES/IRD/UPS), Observatoire Midi Pyrenees, 14 Avenue Edouard Belin, 31400 Toulouse (France); Reyss, J.-L. [LSCE, Laboratoire des Sciences du Climat et de l' Environnement (CNRS/CEA/UVSQ), Avenue de la Terrasse, 91198 Gif-sur-Yvette (France)

    2010-07-15

    Radium isotopes are widely used in marine studies (eg. to trace water masses, to quantify mixing processes or to study submarine groundwater discharge). While {sup 228}Ra and {sup 226}Ra are usually measured using gamma spectrometry, short-lived Ra isotopes ({sup 224}Ra and {sup 223}Ra) are usually measured using a Radium Delayed Coincidence Counter (RaDeCC). Here we show that the four radium isotopes can be analyzed using gamma spectrometry. We report {sup 226}Ra, {sup 228}Ra, {sup 224}Ra, {sup 223}Ra activities measured using low-background gamma spectrometry in standard samples, in water samples collected in the vicinity of our laboratory (La Palme and Vaccares lagoons, France) but also in seawater samples collected in the plume of the Amazon river, off French Guyana (AMANDES project). The {sup 223}Ra and {sup 224}Ra activities determined in these samples using gamma spectrometry were compared to the activities determined using RaDeCC. Activities determined using the two techniques are in good agreement. Uncertainties associated with the {sup 224}Ra activities are similar for the two techniques. RaDeCC is more sensitive for the detection of low {sup 223}Ra activities. Gamma spectrometry thus constitutes an alternate method for the determination of short-lived Ra isotopes.

  4. Communications programme for the RA nuclear reactor decommission

    International Nuclear Information System (INIS)

    Milanovic, S.; Antic, D.

    2002-01-01

    During the decommissioning of the RA research nuclear reactor at the VINCA Institute of Nuclear Sciences, an adequate number of radiation and contamination surveys should be conduced to assure radiological safety of the workers, the public and the environment. Public would like to know more about the nuclear and radiological safety. The communications programme defines the ways to informing the public, its representatives and the information media about the health and safety aspects of the activities during the RA nuclear reactor decommission. (author)

  5. From patients with arthralgia, pre-RA and recently diagnosed RA: What is the current status of understanding RA pathogenesis?

    NARCIS (Netherlands)

    M. Molendijk (Marlieke); J.M.W. Hazes (Mieke); E.W. Lubberts (Erik)

    2018-01-01

    textabstractIt is believed that therapy for rheumatoid arthritis (RA) is the most effective and beneficial within a short time frame around RA diagnosis. This insight has caused a shift from research in patients with established RA to patients at risk of developing RA and recently diagnosed

  6. Regulations for RA reactor operation; Propisi nuklearnog reaktora 'RA'

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1980-09-15

    Regulations for RA reactor operation are written in accordance with the legal regulations defined by the Law about radiation protection and related legal acts, as well as technical standards according to the IAEA recommendations. The contents of this book include: fundamental data about the reactor; legal regulations for reactor operation; organizational scheme for reactor operation; general and detailed instructions for operation, behaviour in the reactor building, performing experiments; operating rules for operation under steady state and accidental conditions. [Serbo-Croat] Propisi o radu nuklearnog reaktora RA pisani su tako da svi zakonski propisi definisani 'Zakonom o zastiti od jonizujuceg zracenja' i pratecim propisima (devet pravilnika) kao i tehnicke norme prema preporukama MAAE budu postovani u punoj meri pri radu reaktora. Sadrzaj ove knjige obuhvata: osnovne podatke o reaktoru; zakonske propise; organizaciju rada reaktora RA; opste propise o rezimu rada, kretanju u zgradi reaktora, izvodjenju eksperimenata; pogonske propise za rad u normalnom rezimu i u slucaju udesa.

  7. Design Aspects of the Rayleigh Convection Code

    Science.gov (United States)

    Featherstone, N. A.

    2017-12-01

    Understanding the long-term generation of planetary or stellar magnetic field requires complementary knowledge of the large-scale fluid dynamics pervading large fractions of the object's interior. Such large-scale motions are sensitive to the system's geometry which, in planets and stars, is spherical to a good approximation. As a result, computational models designed to study such systems often solve the MHD equations in spherical geometry, frequently employing a spectral approach involving spherical harmonics. We present computational and user-interface design aspects of one such modeling tool, the Rayleigh convection code, which is suitable for deployment on desktop and petascale-hpc architectures alike. In this poster, we will present an overview of this code's parallel design and its built-in diagnostics-output package. Rayleigh has been developed with NSF support through the Computational Infrastructure for Geodynamics and is expected to be released as open-source software in winter 2017/2018.

  8. Rayleigh-Taylor instability in multi-structured spherical targets

    International Nuclear Information System (INIS)

    Gupta, N.K.; Lawande, S.V.

    1986-01-01

    An eigenvalue equation for the exponential growth rate of the Rayleigh-Taylor instability is derived in spherical geometry. The free surface and jump boundary conditions are obtained from the eigenvalue equation. The eigenvalue equation is solved in the cases where the initial fluid density profile has a step function or exponential variation in space and analytical formulae for growth rate of the instability are obtained. The solutions for the step function are generalized for any number N of spherical zones forming an arbitrary fluid density profile. The results of the numerical calculations for N spherical zones are compared with the exact analytical results for exponential fluid density profile with N=10 and a good agreement is observed. The formalism is further used to study the effects of density gradients on Rayleigh-Taylor instability in spherical geometry. Also analytical formulae are presented for a particular case of N=3 and shell targets. The formalism developed here can be used to study the growth of the instability in present day multi-structured shell targets. (author)

  9. Chemical Applications of Second Harmonic Rayleigh Scattering ...

    Indian Academy of Sciences (India)

    Chemical Applications of Second Harmonic Rayleigh Scattering Puspendu Kumar Das Department of Inorganic and Physical Chemistry Indian Institute of Science Bangalore 560012, India pkdas@ipc.iisc.ernet.in · Slide 2 · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · Slide 12 · Slide 13.

  10. High-frequency Rayleigh-wave method

    Science.gov (United States)

    Xia, J.; Miller, R.D.; Xu, Y.; Luo, Y.; Chen, C.; Liu, J.; Ivanov, J.; Zeng, C.

    2009-01-01

    High-frequency (???2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  11. Pulmonary cryptococcosis in rheumatoid arthritis (RA) patients: Comparison of imaging characteristics among RA, acquired immunodeficiency syndrome, and immunocompetent patients

    International Nuclear Information System (INIS)

    Yanagawa, Noriyo; Sakai, Fumikazu; Takemura, Tamiko; Ishikawa, Satoru; Takaki, Yasunobu; Hishima, Tsunekazu; Kamata, Noriko

    2013-01-01

    Purpose: The imaging characteristics of cryptococcosis in rheumatoid arthritis (RA) patients were analyzed by comparing them with those of acquired immunodeficiency syndrome (AIDS) and immunocompetent patients, and the imaging findings were correlated with pathological findings. Methods: Two radiologists retrospectively compared the computed tomographic (CT) findings of 35 episodes of pulmonary cryptococcosis in 31 patients with 3 kinds of underlying states (10 RA, 12 AIDS, 13 immunocompetent), focusing on the nature, number, and distribution of lesions. The pathological findings of 18 patients (8 RA, 2 AIDS, 8 immunocompetent) were analyzed by two pathologists, and then correlated with imaging findings. Results: The frequencies of consolidation and ground glass attenuation (GGA) were significantly higher, and the frequency of peripheral distribution was significantly lower in the RA group than in the immunocompetent group. Peripheral distribution was less common and generalized distribution was more frequent in the RA group than in the AIDS group. The pathological findings of the AIDS and immunocompetent groups reflected their immune status: There was lack of a granuloma reaction in the AIDS group, and a complete granuloma reaction in the immunocompetent group, while the findings of the RA group varied, including a complete granuloma reaction, a loose granuloma reaction and a hyper-immune reaction. Cases with the last two pathologic findings were symptomatic and showed generalized or central distribution on CT. Conclusion: Cryptococcosis in the RA group showed characteristic radiological and pathological findings compared with the other 2 groups

  12. Pulmonary cryptococcosis in rheumatoid arthritis (RA) patients: Comparison of imaging characteristics among RA, acquired immunodeficiency syndrome, and immunocompetent patients

    Energy Technology Data Exchange (ETDEWEB)

    Yanagawa, Noriyo, E-mail: noriyo_yana@ybb.ne.jp [Departments of Radiology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, 3-8-22, Honkomagome, Bunkyo-ku, Tokyo 113-8677 (Japan); Sakai, Fumikazu [Department of Diagnostic Radiology, Saitama Medical University International Medical Center, 1397-1 Yamane, Hidaka-shi, Saitama 350-1298 (Japan); Takemura, Tamiko [Department of Pathology, Japanese Red Cross Medical Center, 4-1-22 Hiroo, Shibuya-ku, Tokyo 150-8935 (Japan); Ishikawa, Satoru [Department of Respiratory Medicine, National Hospital Organization Chiba-East-Hospital, 673 Nitona-cho, Chuo-ku, Chiba-shi, Chiba 260-8712 (Japan); Takaki, Yasunobu [Departments of Radiology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, 3-8-22, Honkomagome, Bunkyo-ku, Tokyo 113-8677 (Japan); Hishima, Tsunekazu [Department of Pathology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, 3-8-22, Honkomagome, Bunkyo-ku, Tokyo 113-8677 (Japan); Kamata, Noriko [Departments of Radiology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, 3-8-22, Honkomagome, Bunkyo-ku, Tokyo 113-8677 (Japan)

    2013-11-01

    Purpose: The imaging characteristics of cryptococcosis in rheumatoid arthritis (RA) patients were analyzed by comparing them with those of acquired immunodeficiency syndrome (AIDS) and immunocompetent patients, and the imaging findings were correlated with pathological findings. Methods: Two radiologists retrospectively compared the computed tomographic (CT) findings of 35 episodes of pulmonary cryptococcosis in 31 patients with 3 kinds of underlying states (10 RA, 12 AIDS, 13 immunocompetent), focusing on the nature, number, and distribution of lesions. The pathological findings of 18 patients (8 RA, 2 AIDS, 8 immunocompetent) were analyzed by two pathologists, and then correlated with imaging findings. Results: The frequencies of consolidation and ground glass attenuation (GGA) were significantly higher, and the frequency of peripheral distribution was significantly lower in the RA group than in the immunocompetent group. Peripheral distribution was less common and generalized distribution was more frequent in the RA group than in the AIDS group. The pathological findings of the AIDS and immunocompetent groups reflected their immune status: There was lack of a granuloma reaction in the AIDS group, and a complete granuloma reaction in the immunocompetent group, while the findings of the RA group varied, including a complete granuloma reaction, a loose granuloma reaction and a hyper-immune reaction. Cases with the last two pathologic findings were symptomatic and showed generalized or central distribution on CT. Conclusion: Cryptococcosis in the RA group showed characteristic radiological and pathological findings compared with the other 2 groups.

  13. Centrifugally Driven Rayleigh-Taylor Instability

    Science.gov (United States)

    Scase, Matthew; Hill, Richard

    2017-11-01

    The instability that develops at the interface between two fluids of differing density due to the rapid rotation of the system may be considered as a limit of high-rotation rate Rayleigh-Taylor instability. Previously the authors have considered the effect of rotation on a gravitationally dominated Rayleigh-Taylor instability and have shown that some growth modes of instability may be suppressed completely by the stabilizing effect of rotation (Phys. Rev. Fluids 2:024801, Sci. Rep. 5:11706). Here we consider the case of very high rotation rates and a negligible gravitational field. The initial condition is of a dense inner cylinder of fluid surrounded by a lighter layer of fluid. As the system is rotated about the generating axis of the cylinder, the dense inner fluid moves away from the axis and the familiar bubbles and spikes of Rayleigh-Taylor instability develop at the interface. The system may be thought of as a ``fluid-fluid centrifuge''. By developing a model based on an Orr-Sommerfeld equation, we consider the effects of viscosity, surface tension and interface diffusion on the growth rate and modes of instability. We show that under particular circumstances some modes may be stabilized. School of Mathematical Sciences.

  14. Mode coupling in nonlinear Rayleigh--Taylor instability

    International Nuclear Information System (INIS)

    Ofer, D.; Shvarts, D.; Zinamon, Z.; Orszag, S.A.

    1992-01-01

    This paper studies the interaction of a small number of modes in the two-fluid Rayleigh--Taylor instability at relatively late stages of development, i.e., the nonlinear regime, using a two-dimensional hydrodynamic code incorporating a front-tracking scheme. It is found that the interaction of modes can greatly affect the amount of mixing and may even reduce the width of the mixing region. This interaction is both relatively long range in wave-number space and also acts in both directions, i.e., short wavelengths affect long wavelengths and vice versa. Three distinct stages of interaction have been identified, including substantial interaction among modes some of which may still be in their classical (single mode) ''linear'' phase

  15. Simulation of Rayleigh--Taylor flows using vortex blobs

    International Nuclear Information System (INIS)

    Kerr, R.M.

    1988-01-01

    An inviscid boundary-integral method is modified in order to study the single-scale Rayleigh--Taylor instability for arbitrary Atwood number. The primary modification uses vortex blobs to smooth the Green's function and suppress a finite time singularity in the curvature. Additional modifications to earlier codes such as using second-order central differences along the interface to accommodate spikes in the vorticity and spreading the nodes evenly along the interface to suppress clustering of nodes are designed to maintain resolution and accuracy. To achieve second-order accuracy in time when the nodes are spread, an extra predictor step is needed that shifts the nodes before the variables are advanced. The method successfully follows the development of a single mode to states with asymptotic velocities for the bubble and spike that depend on the Atwood number and are independent of the blob size. Incipient droplet formation is observed. copyright 1988 Academic Press, Inc

  16. Throughput and Delay Analysis of HARQ with Code Combining over Double Rayleigh Fading Channels

    KAUST Repository

    Chelli, Ali

    2018-01-15

    This paper proposes the use of hybrid automatic repeat request (HARQ) with code combining (HARQ-CC) to offer reliable communications over double Rayleigh channels. The double Rayleigh fading channel is of particular interest to vehicle-to-vehicle communication systems as well as amplify-and-forward relaying and keyhole channels. This work studies the performance of HARQ-CC over double Rayleigh channels from an information theoretic perspective. Analytical approximations are derived for the $\\\\epsilon$-outage capacity, the average number of transmissions, and the throughput of HARQ-CC. Moreover, we evaluate the delay experienced by Poisson arriving packets for HARQ-CC. We provide analytical expressions for the average waiting time, the packets sojourn time, the average consumed power, and the energy efficiency. In our investigation, we take into account the impact of imperfect feedback on different performance metrics. Additionally, we explore the tradeoff between energy efficiency and the throughput. The proposed scheme is shown to maintain the outage probability below a specified threshold $\\\\epsilon$ which ensures the link reliability. Meanwhile, HARQ-CC adapts implicitly the transmission rate to the channel conditions such that the throughput is maximized. Our results demonstrate that HARQ-CC allows improving the achievable communication rate compared to fixed time diversity schemes. To maximize the throughput of HARQ-CC, the rate per HARQ round should be less than the rate required to meet the outage constraint. Our investigation of the performance of HARQ-CC over Rayleigh and double Rayleigh channels shows that double Rayleigh channels have a higher severity of fading and result in a larger degradation of the throughput. Our analysis reveals that HARQ with incremental redundancy (HARQ-IR) achieves a larger throughput compared to HARQ-CC, while HARQ-CC is simpler to implement, has a lower decoding

  17. Research nuclear reactor RA - Annual Report 1991; Istrazivacki nuklearni reaktor RA - Izvestaj za 1991. godinu

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1992-01-01

    Activities related to revitalisation of the RA reactor stared in 1986, were continued in 1991. A number of interventions on the reactor components were finished that are supposed to enable continuous and reliable operation. The last, and at the same time largest action, related to exchange of complete reactor instrumentation is underway, but it is behind the schedule in 1991 because the delivery of components from USSR is late. Production of this instruments is financed by the IAEA according to the contract signed in December 1988 with Russian Atomenergoexport. According to this contract, it has been planned that the RA reactor instrumentation should be delivered to the Vinca Institute by the end of 1990. Only 56% of the instrumentation was delivered until September 1991. Since then any delivery of components to Yugoslavia was stopped because of the temporary embargo imposed by the IAEA. In 1991 most of the existing RA reactor instrumentation was dismantled, only the part needed for basic measurements when reactor is not operated, was maintained. Construction of some support elements is almost finished by the local staff. The Institute has undertaken this activity in order to speed up the ending of the project. If all the planned instrumentation would not arrive until the end of March 1992, it would not be possible to start the RA reactor testing operation in the first part of 1993, as previously planned. In 1991, 53 staff members took part in the activities during 1991, which is considered sufficient for maintenance and repair conditions. Research reactor RA Annual report for year 1991 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection. [Serbo-Croat] U 1991. godini nastavljeni su poslovi na revitalizaciji reaktora RA, zapocetoj 1986. godine. Okoncan je niz zahvata na opremi postrojenja kojima ce se u narednom periodu omoguciti kontinualan i pouzdan rad ovog reaktora. Poslednji, i ujedno najveci

  18. Development of RaRaII solar car. Solar car RaRaII no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, M [Toyota Motor Corp., Aichi (Japan)

    1991-05-31

    A solar car was developed to be able to travel, by utilizing solar energy, as a guiding car for the marathon race in the public road. That car is 210kg in weight, 1 in number of riding persons and 4.8m in smallest rotating radius. Its traveling performance is 44km h in highest speed, 10{degree} in hill-climbing ability and 0.6m s{sup 2} in acceleration. Those principal particulars satisfied the required condition of guiding car for the marathon race. That car was equipped with a polycrystalline silicon type solar cell, 6m{sup 2} in area to generate 870Wp power. A silver oxide-zinc battery, used as a secondary battery to secure traveling in case of rain, is of a performance to travel twice the marathon race road through. To satisfy the public road traveling in safety standard, that car was equipped with head lamps, wiper, direction winkers, rear-view mirrors, etc. As material of the body, aramid fiber and carbon fiber were adopted for securing the rigidity to cover the lightening in weight. That car, as used at an opportunity of intercollegiate marathon relay race, traveled a distance of about 30km which was its entire public road portion of course. 2 figs., 2 tabs.

  19. Surfactants and the Rayleigh-Taylor instability of Couette type flows

    Science.gov (United States)

    Frenkel, A. L.; Halpern, D.; Schweiger, A. S.

    2011-11-01

    We study the Rayleigh-Taylor instability of slow Couette- type flows in the presence of insoluble surfactants. It is known that with zero gravity, the surfactant makes the flow unstable to longwave disturbances in certain regions of the parameter space; while in other parametric regions, it reinforces the flow stability (Frenkel and Halpern 2002). Here, we show that in the latter parametric sectors, and when the (gravity) Bond number Bo is below a certain threshold value, the Rayleigh-Taylor instability is completely stabilized for a finite interval of Ma, the (surfactant) Marangoni number: MaL Ma2. For Ma Ma2, and also for MaL Ma2 as functions of the Bond number. We note that (for an interval of the Bond number) there are two distinct criticalities with nonzero (and distinct) critical wavenumbers.

  20. Angular plasmon response of gold nanoparticles arrays: approaching the Rayleigh limit

    Directory of Open Access Journals (Sweden)

    Marae-Djouda Joseph

    2016-07-01

    Full Text Available The regular arrangement of metal nanoparticles influences their plasmonic behavior. It has been previously demonstrated that the coupling between diffracted waves and plasmon modes can give rise to extremely narrow plasmon resonances. This is the case when the single-particle localized surface plasmon resonance (λLSP is very close in value to the Rayleigh anomaly wavelength (λRA of the nanoparticles array. In this paper, we performed angle-resolved extinction measurements on a 2D array of gold nano-cylinders designed to fulfil the condition λRA<λLSP. Varying the angle of excitation offers a unique possibility to finely modify the value of λRA, thus gradually approaching the condition of coupling between diffracted waves and plasmon modes. The experimental observation of a collective dipolar resonance has been interpreted by exploiting a simplified model based on the coupling of evanescent diffracted waves with plasmon modes. Among other plasmon modes, the measurement technique has also evidenced and allowed the study of a vertical plasmon mode, only visible in TM polarization at off-normal excitation incidence. The results of numerical simulations, based on the periodic Green’s tensor formalism, match well with the experimental transmission spectra and show fine details that could go unnoticed by considering only experimental data.

  1. Reynolds analogy for the Rayleigh problem at various flow modes.

    Science.gov (United States)

    Abramov, A A; Butkovskii, A V

    2016-07-01

    The Reynolds analogy and the extended Reynolds analogy for the Rayleigh problem are considered. For a viscous incompressible fluid we derive the Reynolds analogy as a function of the Prandtl number and the Eckert number. We show that for any positive Eckert number, the Reynolds analogy as a function of the Prandtl number has a maximum. For a monatomic gas in the transitional flow regime, using the direct simulation Monte Carlo method, we investigate the extended Reynolds analogy, i.e., the relation between the shear stress and the energy flux transferred to the boundary surface, at different velocities and temperatures. We find that the extended Reynolds analogy for a rarefied monatomic gas flow with the temperature of the undisturbed gas equal to the surface temperature depends weakly on time and is close to 0.5. We show that at any fixed dimensionless time the extended Reynolds analogy depends on the plate velocity and temperature and undisturbed gas temperature mainly via the Eckert number. For Eckert numbers of the order of unity or less we generalize an extended Reynolds analogy. The generalized Reynolds analogy depends mainly only on dimensionless time for all considered Eckert numbers of the order of unity or less.

  2. Rayleigh wave effects in an elastic half-space.

    Science.gov (United States)

    Aggarwal, H. R.

    1972-01-01

    Consideration of Rayleigh wave effects in a homogeneous isotropic linearly elastic half-space subject to an impulsive uniform disk pressure loading. An approximate formula is obtained for the Rayleigh wave effects. It is shown that the Rayleigh waves near the center of loading arise from the portion of the dilatational and shear waves moving toward the axis, after they originate at the edge of the load disk. A study is made of the vertical displacement due to Rayleigh waves at points on the axis near the surface of the elastic half-space.

  3. Rayleigh-Taylor analysis in a laser-induced plasma

    International Nuclear Information System (INIS)

    Marin, R A; Gonzales, C A; Riascos, H

    2012-01-01

    We report the conditions (plasma parameters) under which the Rayleigh-Taylor Instability (RTI) develops in an Al plasma produced by a Nd:Yag pulsed laser with a fluence range of 1 to 4 J/cm 2 , wavelength of 1064nm and 10Hz repetition rate. The used data correspond to different pressure values of the ambient N atmosphere. From previous works, we took the RTI growth rate form. From the perturbation theory the instability amplitude is proportional to e -ηt . Using the drag model, we calculated the plume dynamics equations integrating the instability term and plotted the instability growth profile with the delay time values to get critical numbers for it, in order to show under which conditions the RTI appears.

  4. Three caveats for linear stability theory: Rayleigh-Benard convection

    International Nuclear Information System (INIS)

    Greenside, H.S.

    1984-06-01

    Recent theories and experiments challenge the applicability of linear stability theory near the onset of buoyancy-driven (Rayleigh-Benard) convection. This stability theory, based on small perturbations of infinite parallel rolls, is found to miss several important features of the convective flow. The reason is that the lateral boundaries have a profound influence on the possible wave numbers and flow patterns even for the largest cells studied. Also, the nonlinear growth of incoherent unstable modes distorts the rolls, leading to a spatially disordered and sometimes temporally nonperiodic flow. Finally, the relation of the skewed varicose instability to the onset of turbulence (nonperiodic time dependence) is examined. Linear stability theory may not suffice to predict the onset of time dependence in large cells close to threshold

  5. Chemical dosimetry at the RA reactor; Hemijska dozimetrija reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    Gal, O [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    This report presents the results of measurements of absorbed doses axial and radial distribution in the vertical experimental channels of the RA reactor. Measurements were done in channels VK-5, VK-7, VK-9 and GF-36. Results were compared to the results of calorimetry measurements and measured neutron flux values performed by other laboratories. Fricke and oxalate dosemeters were used in addition to the cobalt indicators.

  6. Predictability of Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Viecelli, J.A.

    1986-01-01

    Numerical experiments modeling the Rayleigh Taylor instability are carried out using a two-dimensional incompressible Eulerian hydrodynamic code VFTS. The method of integrating the Navier-Stokes equations including the viscous terms is similar to that described in Kim and Moin, except that Lagrange particles have been added and provision for body forces is given. The Eulerian method is 2nd order accurate in both space and time, and the Poisson equation for the effective pressure field is solved exactly at each time step using a cyclic reduction method. 3 refs., 3 figs

  7. A simple proposal for Rayleigh's scaterring experiment

    Directory of Open Access Journals (Sweden)

    Adriano José Ortiz

    2010-03-01

    Full Text Available This work presents an alternative proposal for Rayleigh's scattering experiment presented and discussed in Krapas and Santos (2002 in this journal. Besides being simple and low-cost, the proposal suggested here is also proposing to demonstrate experimentally other physical phenomena such as polarization of light from the sky, the rainbow and reflection on non-conductive surfaces, as well as determine the direction of these biases. The polarization will be observed with the aid of Polaroid obtained from liquid crystal displays taken from damaged electronic devices and the Polaroid polarization direction will be established by the observation of Brewester's angle in reflection experiment.

  8. Bayesian Predictive Models for Rayleigh Wind Speed

    DEFF Research Database (Denmark)

    Shahirinia, Amir; Hajizadeh, Amin; Yu, David C

    2017-01-01

    predictive model of the wind speed aggregates the non-homogeneous distributions into a single continuous distribution. Therefore, the result is able to capture the variation among the probability distributions of the wind speeds at the turbines’ locations in a wind farm. More specifically, instead of using...... a wind speed distribution whose parameters are known or estimated, the parameters are considered as random whose variations are according to probability distributions. The Bayesian predictive model for a Rayleigh which only has a single model scale parameter has been proposed. Also closed-form posterior...... and predictive inferences under different reasonable choices of prior distribution in sensitivity analysis have been presented....

  9. Radium isotope (223Ra, 224Ra, 226Ra and 228Ra) distribution near Brazil's largest port, Paranaguá Bay, Brazil

    International Nuclear Information System (INIS)

    Dias, Thais H.; Oliveira, Joselene de; Sanders, Christian J.; Carvalho, Franciane; Sanders, Luciana M.; Machado, Eunice C.; Sá, Fabian

    2016-01-01

    This work investigates the 223 Ra, 224 Ra, 226 Ra and 228 Ra isotope distribution in river, estuarine waters and sediments of the Paranaguá Estuarine Complex (PEC). The stratification of the Ra isotopes along water columns indicate differing natural sources. In sediments, the radium isotope activities was inversely proportional to the particle size. The highest concentrations of 223 Ra, 224 Ra, 226 Ra and 228 Ra in the water column were found in the bottom more saline waters and towards the inner of the estuary. These relatively high concentrations towards the bottom of the estuary may be attributed to the influence of tidally driven groundwater source and desorption from particles at the maximum turbidity zone. The apparent river water ages from the radium isotope ratios, 223 Ra/ 224 Ra and 223 Ra/ 228 Ra, indicate that the principal rivers that flow into the estuary have residence times from between 6 and 11 days. - Highlights: • Radium isotope concentrations were evaluated along a large estuarine system. • The radioactivity level in river, estuary and sediments was within a normal range. • Spatial distributions of site specific radionuclides have differing activities and sources.

  10. RA Reactor applications, Annex A

    International Nuclear Information System (INIS)

    Cupac, S.; Vukadin, Z.

    2000-01-01

    Full text: In 2000 Ra reactor was not operated. New instrumentation is not complete, without it, it is not possible to think about reactor start-up. Since 1985, when reactor operation was forbidden, there are 480 fuel elements left in 48 fuel channels in the reactor core. Heavy water was removed from the reactor core because of the repair of the heavy water pumps in 1986. The old instrumentation was removed. Eleven years after being left to its own destiny, it would be difficult to imagine that anybody would think of reactor restart without examining the state of reactor vessel and other vital reactor components. Maintaining the reactor under existing conditions without final decision about restart or permanent shutdown is destructive for this nuclear facility. The existing state that pertains for more than 10 years would have only one result, destruction of the RA reactor [sr

  11. RA Reactor applications, Annex A

    International Nuclear Information System (INIS)

    Cupac, S.; Vukadin, Z.

    1998-01-01

    Full text: In 1998 Ra reactor was not operated. New instrumentation is not complete, without it, it is not possible to think about reactor start-up. Since 1985, when reactor operation was forbidden, there are 480 fuel elements left in 48 fuel channels in the reactor core. Heavy water was removed from the reactor core because of the repair of the heavy water pumps in 1986. The old instrumentation was removed. Eleven years after being left to its own destiny, it would be difficult to imagine that anybody would think of reactor restart without examining the state of reactor vessel and other vital reactor components. Maintaining the reactor under existing conditions without final decision about restart or permanent shutdown is destructive for this nuclear facility. The existing state that pertains for more than 10 years would have only one result, destruction of the RA reactor [sr

  12. RA Reactor applications, Annex A

    International Nuclear Information System (INIS)

    Cupac, S.; Vukadin, Z.

    1996-01-01

    Full text: In 2000 Ra reactor was not operated. New instrumentation is not complete, without it, it is not possible to think about reactor start-up. Since 1985, when reactor operation was forbidden, there are 480 fuel elements left in 48 fuel channels in the reactor core. Heavy water was removed from the reactor core because of the repair of the heavy water pumps in 1986. The old instrumentation was removed. Eleven years after being left to its own destiny, it would be difficult to imagine that anybody would think of reactor restart without examining the state of reactor vessel and other vital reactor components. Maintaining the reactor under existing conditions without final decision about restart or permanent shutdown is destructive for this nuclear facility. The existing state that pertains for more than 10 years would have only one result, destruction of the RA reactor [sr

  13. 228Ra in monazite processing

    International Nuclear Information System (INIS)

    Paul, A.C.; Pillai, K.C.

    1979-01-01

    The treatment of monazite, adopted by the Indian Rare Earths plant is based on alkali digestion by caustic soda and acid leaching by hydrochloric acid. The paper deals with the distribution of 228 Ra, the daughter product of 232 Th in the effluents and outlines the treatment procedures adopted to reduce its levels. The activity gets distributed into the soluble and insoluble fractions in the effluent depending on its acidic/alkaline nature. The scheme for further deactivation of the effluent was based on lime treatment. It is observed that more than 95% removal of Ra is achievable by the treatment. The procedures leading to the proposed final treatment and disposal of effluent are schematically represented. Some environmental data are presented to show the impact of effluent releases in river, water and sediments. (B.G.W.)

  14. Short Rayleigh length free electron lasers

    Directory of Open Access Journals (Sweden)

    W. B. Colson

    2006-03-01

    Full Text Available Conventional free electron laser (FEL oscillators minimize the optical mode volume around the electron beam in the undulator by making the resonator Rayleigh length about one third to one half of the undulator length. This maximizes gain and beam-mode coupling. In compact configurations of high-power infrared FELs or moderate power UV FELs, the resulting optical intensity can damage the resonator mirrors. To increase the spot size and thereby reduce the optical intensity at the mirrors below the damage threshold, a shorter Rayleigh length can be used, but the FEL interaction is significantly altered. We model this interaction using a coordinate system that expands with the rapidly diffracting optical mode from the ends of the undulator to the mirrors. Simulations show that the interaction of the strongly focused optical mode with a narrow electron beam inside the undulator distorts the optical wave front so it is no longer in the fundamental Gaussian mode. The simulations are used to study how mode distortion affects the single-pass gain in weak fields, and the steady-state extraction in strong fields.

  15. Lightcurve of NEA 1993 RA

    Science.gov (United States)

    Vaduvescu, Ovidiu; Aznar Macias, Amadeo

    2018-01-01

    The near-Earth asteroid (NEA) 1993 RA was observed with the 2.5-m Isaac Newton Telescope (INT) in full Moon conditions for 8h total during three successive nights (2017 Oct 3-6). The composite lightcurve could be fit by a 3-order period P = 5.64 ± 0.01 h with amplitude of 0.13 mag; other solutions are possible.

  16. Regulations for RA reactor operation

    International Nuclear Information System (INIS)

    1980-09-01

    Regulations for RA reactor operation are written in accordance with the legal regulations defined by the Law about radiation protection and related legal acts, as well as technical standards according to the IAEA recommendations. The contents of this book include: fundamental data about the reactor; legal regulations for reactor operation; organizational scheme for reactor operation; general and detailed instructions for operation, behaviour in the reactor building, performing experiments; operating rules for operation under steady state and accidental conditions [sr

  17. Research nuclear reactor RA - Annual Report 1994; Istrazivacki nuklearni reaktor RA - Izvestaj za 1994. godinu

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1994-12-01

    Activities related to revitalisation of the RA reactor stared in 1986, were continued in 1991. A number of interventions on the reactor components were finished that are supposed to enable continuous and reliable operation. The last, and at the same time largest action, related to exchange of complete reactor instrumentation is underway, but it is behind the schedule in 1991 because the delivery of components from USSR is late. Production of this instruments is financed by the IAEA according to the contract signed in December 1988 with Russian Atomenergoexport. According to this contract, it has been planned that the RA reactor instrumentation should be delivered to the Vinca Institute by the end of 1990. Only 56% of the instrumentation was delivered until September 1991. Since then any delivery of components to Yugoslavia was stopped because of the temporary embargo imposed by the IAEA. In 1991 most of the existing RA reactor instrumentation was dismantled, only the part needed for basic measurements when reactor is not operated, was maintained. Activities related to improvement of Russian project were continued in 1994. Control and maintenance of the reactor components was done regularly and efficiently. Extensive repair of the secondary coolant loop is almost finished and will be completed in the first part of 1995 according to existing legal procedures and IAEA recommendations. Fuel inspection by the IAEA safeguards inspectors was done on a monthly basis. There have been on the average 47 employees at the RA reactor which is considered sufficient for maintenance and repair conditions. Research reactor RA Annual report for year 1991 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection. [Serbo-Croat] U 1994. godini nastavljeni su poslovi na revitalizaciji reaktora RA, zapocetoj 1986. godine. Okoncan je niz zahvata na opremi postrojenja kojima ce se u narednom periodu omoguciti kontinualan i

  18. Post-stroke infection: a role for IL-1ra?

    Science.gov (United States)

    Tanzi, Pat; Cain, Kevin; Kalil, Angela; Zierath, Dannielle; Savos, Anna; Gee, J Michael; Shibata, Dean; Hadwin, Jessica; Carter, Kelly; Becker, Kyra

    2011-04-01

    Infection is common following stroke and is independently associated with worse outcome. Clinical studies suggest that infections occur more frequently in those individuals with stroke-induced immunologic dysfunction. This study sought to explore the contribution of immunomodulatory cytokines and hormones to lymphocyte function and infection risk. Patients (N = 112) were enrolled as soon as possible after the onset of ischemic stroke. Blood was drawn to assess plasma cortisol, IL-10, IL-1ra, lymphocyte numbers, and lymphocyte function at 72 h after stroke onset; infections were censored through 21 days after stroke onset. Infection occurred in 25% of patients. Stroke severity was the most important predictor of infection risk. Increased plasma cortisol, IL-10, and IL-1ra, as well as decreased lymphocyte numbers, at 72 h after stroke onset were associated with risk of subsequent infection. After controlling for stroke severity, only IL-1ra was independently associated with infection risk, and the degree of risk was consistent throughout the post-stroke period. Infection, but not IL-1ra itself, was associated with worse outcome at 3 months. In this study cohort, increased plasma IL-1ra was independently associated with the risk of post-stroke infection. Further studies are needed to validate this finding, which could have important implications for stroke therapy.

  19. RA research nuclear reactor - Annual report 1985; Istrazivacki nuklearni reaktor RA - Izvestaj za 1985. godinu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1985-12-01

    Research reactor RA Annual report for year 1985 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection. [Serbo-Croat] Godisnji izvestaj po projektu 'Istrazivacki nuklearni reaktor RA' za 1985 godinu sastoji se od dva dela: prvi deo obuhvata pogon i odzavanje reaktora RA, a drugi poslove zastite od zracenja na reaktoru RA.

  20. RA Research reactor, Annual report 1986; Istrazivacki nuklearni reaktor RA - Izvestaj za 1986. godinu

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1986-12-01

    Research reactor RA Annual report for year 1985 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection. [Serbo-Croat] Godisnji izvestaj po projektu 'Istrazivacki nuklearni reaktor RA' za 1986 godinu sastoji se od dva dela: prvi deo obuhvata pogon i odzavanje reaktora RA, a drugi poslove zastite od zracenja na reaktoru RA.

  1. Cell structures caused by settling particles in turbulent Rayleigh-Bénard convection

    Science.gov (United States)

    Lee, Changhoon; Park, Sangro

    2016-11-01

    Turbulent thermal convection is an important phenomenon frequently found in nature and industrial processes, often with laden particles. In the last several decades, the vast majority of studies have addressed single phase convective flow with focus on the scaling relation of flow parameters associated with heat transfer. Particle-laden Rayleigh-Bénard convection, however, has not been sufficiently studied. In this study, modulation of cell structures by settling particles in turbulent Rayleigh-Bénard convection in a doubly periodic square channel is investigated using direct numerical simulation with a point particle approach. Flow parameters are fixed at Rayleigh number=106, Prandtl number=0.7, the aspect ratio=6, and Froude number=0.19. We report from the simulations that settling heavy particles modulate irregular large-scale thermal plume structures into organized polygonal cell structures. Different shapes of flow structures are obtained for different particle diameters and mass loadings. We found that polygonal cell structures arise due to asymmetric feedback force exerted by particles onto hot and cold plumes. Increasing the number of particles augments the asymmetry and the polygonal cell structures become smaller, eventually going to the hexagonal structures.

  2. Effect of resistivity on the Rayleigh-Taylor instability in an accelerated plasma

    International Nuclear Information System (INIS)

    Castillo, J.L.; Huerta, M.A.

    1993-01-01

    We study the Rayleigh-Taylor instability in finite-conductivity accelerated plasma arcs of the type found in electromagnetic rail launchers. For a plasma of length l, acceleration a, and thermal speed v T we consider the case where v T 2 /al much-gt 1, which is valid when the projectile mass is large compared to the plasma mass. The conductivity σ enters via a magnetic Reynolds number R=σμ(al 3 ) 1/2 . The fourth-order mode equation is solved analytically using an asymptotic WKB expansion in 1/R. We find the first-order 1/R correction to the classical Rayleigh-Taylor dispersion relation for large wave number K but with K much-lt R 2 /l. The analytical results show good agreement with previous numerical calculations

  3. Measurements of neutron flux in the RA reactor; Merenje karakteristika neutronskog fluksa u reaktoru RA

    Energy Technology Data Exchange (ETDEWEB)

    Raisic, N [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    This report includes the following separate parts: Thermal neutron flux in the experimental channels od RA reactor; Epithermal neutron flux in the experimental channels od RA reactor; Fast neutron flux in the experimental channels od RA reactor; Thermal neutron flux in the thermal column and biological experimental channel; Neutronic measurements in the RA reactor cell; Temperature reactivity coefficient of the RA reactor; design of the device for measuring the activity of wire. [Serbo-Croat] Ovaj izvestaj sadrzi sledece referate: Fluks termalnih neutrona u eksperimentalnim kanalima reaktora RA; Fluks epitermalnih neutrona u eksperimentalnim kanalima reaktora RA; Fluks brzih neutrona u eksperimentalnim kanalima reaktora RA; Fluks termalnih neurona u termalnoj koloni i bioloskom eksperimentalnom kanalu; Neutronska merenja u elementarnoj celiji reaktora RA; Temperaturni koeficijent reaktivnosti reaktora RA; Projekat uredjaja za merenje radioaktivnosti zice.

  4. Nonlinear spectrum of the ablative Rayleigh-Taylor instability in laser-accelerated planar plasmas

    International Nuclear Information System (INIS)

    Keskinen, M. J.; Schmitt, A.

    2007-01-01

    A model for the nonlinear spectrum of the ablative Rayleigh-Taylor instability in laser-accelerated planar plasmas has been developed for a wide range of Froude numbers and scale sizes. It is found that the spectrum can be characterized by an inverse power law with spectral index of approximately 2 in the limit of small-wavenumber spectrum cutoffs and small-scale density gradient scale lengths. Comparison of the model spectrum with recent experimental observations is made with good agreement

  5. Rayleigh-Taylor instability in the presence of a density transition layer

    International Nuclear Information System (INIS)

    Tavakoli, A.; Tskhakaya, D.D.; Tsintsadze, N.L.

    1999-01-01

    A new type of symmetry for the Rayleigh equation is found. For small Atwood number an analytic solution is obtained for a smoothly varying density profile. The spectra of unstable modes are defined. It is shown that a transition layer with finite width can undergo stratification, and velocity shear between new-formed sublayers forms. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  6. Rayleigh-type parametric chemical oscillation

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Shyamolina; Ray, Deb Shankar, E-mail: pcdsr@iacs.res.in [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2015-09-28

    We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

  7. Rayleigh-type parametric chemical oscillation.

    Science.gov (United States)

    Ghosh, Shyamolina; Ray, Deb Shankar

    2015-09-28

    We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

  8. Rayleigh's hypothesis and the geometrical optics limit.

    Science.gov (United States)

    Elfouhaily, Tanos; Hahn, Thomas

    2006-09-22

    The Rayleigh hypothesis (RH) is often invoked in the theoretical and numerical treatment of rough surface scattering in order to decouple the analytical form of the scattered field. The hypothesis stipulates that the scattered field away from the surface can be extended down onto the rough surface even though it is formed by solely up-going waves. Traditionally this hypothesis is systematically used to derive the Volterra series under the small perturbation method which is equivalent to the low-frequency limit. In this Letter we demonstrate that the RH also carries the high-frequency or the geometrical optics limit, at least to first order. This finding has never been explicitly derived in the literature. Our result comforts the idea that the RH might be an exact solution under some constraints in the general case of random rough surfaces and not only in the case of small-slope deterministic periodic gratings.

  9. Influence of the IL-1Ra gene polymorphism on in vivo synthesis of IL-1Ra and IL-1beta after live yellow fever vaccination.

    Science.gov (United States)

    Hacker, U T; Erhardt, S; Tschöp, K; Jelinek, T; Endres, S

    2001-09-01

    The inflammatory response in infectious and autoimmune diseases is regulated by the balance between pro- and anti-inflammatory cytokines. The IL-1 complex contains polymorphic genes coding for IL-1alpha, IL-1beta and IL-1Ra. The IL-1Ra (variable number of tanden repeat) VNTR polymorphism has been shown to influence the capacity to produce IL-1beta and IL-1Ra after in vitro stimulation. Allele 2 of this polymorphism is associated with a number of inflammatory diseases. To determine the impact of the IL-1Ra polymorphism on in vivo human cytokine synthesis, we used a yellow fever vaccination model for the induction of cytokine synthesis in healthy volunteers. Two different yellow fever vaccines were used. After administration of the RKI vaccine (34 volunteers), plasma TNF-alpha concentration increased from 13.4 +/- 0.9 pg/ml to 23.3 +/- 1.1 pg/ml (P < 0.001), and plasma IL-1Ra concentration increased from 308 +/- 25 pg/ml to 1019 +/- 111 pg/ml (P < 0.001), on day 2. Using Stamaril vaccine, no increase in the plasma concentrations of either TNF-alpha or IL-1Ra could be detected (n = 17). Only the RKI vaccine induced TNF-alpha synthesis after in vitro stimulation of MNC. Carriers of allele 2 of the IL-1Ra polymorphism had increased baseline concentrations of IL-1Ra (350 +/- 32 pg/ml) compared with non-carriers (222 +/- 18 pg/ml, P < 0.001), and decreased concentrations of IL-1beta (0.9 +/- 0.2 pg/ml for carriers versus 2.8 +/- 0.7 pg/ml for non-carriers, P = 0.017). After yellow fever vaccination (RKI vaccine), no significant differences in the increase of IL-1Ra plasma levels were detected between carriers and non-carriers of allele 2 of the IL-1Ra gene polymorphism. This is the first study to examine the influence of this genetic polymorphism on in vivo-induced human IL-1beta and IL-1Ra synthesis. Baseline concentrations of IL-1Ra and IL-1beta were significantly influenced by the IL-1Ra polymorphism. No influence of the IL-1Ra polymorphism on the in vivo

  10. A model for near-wall dynamics in turbulent Rayleigh Bénard convection

    Science.gov (United States)

    Theerthan, S. Ananda; Arakeri, Jaywant H.

    1998-10-01

    Experiments indicate that turbulent free convection over a horizontal surface (e.g. Rayleigh Bénard convection) consists of essentially line plumes near the walls, at least for moderately high Rayleigh numbers. Based on this evidence, we propose here a two-dimensional model for near-wall dynamics in Rayleigh Bénard convection and in general for convection over heated horizontal surfaces. The model proposes a periodic array of steady laminar two-dimensional plumes. A plume is fed on either side by boundary layers on the wall. The results from the model are obtained in two ways. One of the methods uses the similarity solution of Rotem & Classen (1969) for the boundary layer and the similarity solution of Fuji (1963) for the plume. We have derived expressions for mean temperature and temperature and velocity fluctuations near the wall. In the second approach, we compute the two-dimensional flow field in a two-dimensional rectangular open cavity. The number of plumes in the cavity depends on the length of the cavity. The plume spacing is determined from the critical length at which the number of plumes increases by one. The results for average plume spacing and the distribution of r.m.s. temperature and velocity fluctuations are shown to be in acceptable agreement with experimental results.

  11. Direct Numerical Simulations of Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Livescu, D; Wei, T; Petersen, M R

    2011-01-01

    The development of the Rayleigh-Taylor mixing layer is studied using data from an extensive new set of Direct Numerical Simulations (DNS), performed on the 0.5 Petaflops, 150k compute cores BG/L Dawn supercomputer at Lawrence Livermore National Laboratory. This includes a suite of simulations with grid size of 1024 2 × 4608 and Atwood number ranging from 0.04 to 0.9, in order to examine small departures from the Boussinesq approximation as well as large Atwood number effects, and a high resolution simulation of grid size 4096 2 × 4032 and Atwood number of 0.75. After the layer width had developed substantially, additional branched simulations have been run under reversed and zero gravity conditions. While the bulk of the results will be published elsewhere, here we present preliminary results on: 1) the long-standing open question regarding the discrepancy between the numerically and experimentally measured mixing layer growth rates and 2) mixing characteristics.

  12. QUADRO: A SUPERVISED DIMENSION REDUCTION METHOD VIA RAYLEIGH QUOTIENT OPTIMIZATION.

    Science.gov (United States)

    Fan, Jianqing; Ke, Zheng Tracy; Liu, Han; Xia, Lucy

    We propose a novel Rayleigh quotient based sparse quadratic dimension reduction method-named QUADRO (Quadratic Dimension Reduction via Rayleigh Optimization)-for analyzing high-dimensional data. Unlike in the linear setting where Rayleigh quotient optimization coincides with classification, these two problems are very different under nonlinear settings. In this paper, we clarify this difference and show that Rayleigh quotient optimization may be of independent scientific interests. One major challenge of Rayleigh quotient optimization is that the variance of quadratic statistics involves all fourth cross-moments of predictors, which are infeasible to compute for high-dimensional applications and may accumulate too many stochastic errors. This issue is resolved by considering a family of elliptical models. Moreover, for heavy-tail distributions, robust estimates of mean vectors and covariance matrices are employed to guarantee uniform convergence in estimating non-polynomially many parameters, even though only the fourth moments are assumed. Methodologically, QUADRO is based on elliptical models which allow us to formulate the Rayleigh quotient maximization as a convex optimization problem. Computationally, we propose an efficient linearized augmented Lagrangian method to solve the constrained optimization problem. Theoretically, we provide explicit rates of convergence in terms of Rayleigh quotient under both Gaussian and general elliptical models. Thorough numerical results on both synthetic and real datasets are also provided to back up our theoretical results.

  13. VELoCiRaPTORS.

    Science.gov (United States)

    Lundgren, J.; Esham, B.; Padalino, S. J.; Sangster, T. C.; Glebov, V.

    2007-11-01

    The Venting and Exhausting of Low Level Air Contaminants in the Rapid Pneumatic Transport of Radioactive Samples (VELoCiRaPTORS) system is constructed to transport radioactive materials quickly and safely at the NIF. A radioactive sample will be placed inside a carrier that is transported via an airflow system produced by controlled differential pressure. Midway through the transportation process, the carrier will be stopped and vented by a powered exhaust blower which will remove radioactive gases within the transport carrier. A Geiger counter will monitor the activity of the exhaust gas to ensure that it is below acceptable levels. If the radiation level is sufficient, the carrier will pass through the remainder of the system, pneumatically braking at the counting station. The complete design will run manually or automatically with control software. Tests were performed using an inactive carrier to determine possible transportation problems. The system underwent many consecutive trials without failure. VELoCiRaPTORS is a prototype of a system that could be installed at both the Laboratory for Laser Energetics at the University of Rochester and the National Ignition Facility at LLNL.

  14. Measurements at the RA Reactor related to the VISA-2 project - Part 1, Start-up of the RA reactor and measurement of new RA reactor core parameters; Fizicka merenja na reaktoru RA u vezi projekta VISA-2 - I deo, Pustanje u rad reaktora RA i merenje fizickih parametara novog jezgra reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    Markovic, H [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1962-07-15

    The objective of the measurements was determining the neutron flux in the RA reactor core. Since the number of fuel channels is increased from 56 to 68 within the VISA-2 project, it was necessary to attain criticality of the RA reactor and measure the neutron flux properties. The 'program of RA reactor start-up' has been prepared separately and it is included in this report. Measurements were divided in two phases. First phase was measuring of the neutron flux after the criticality was achieved but at zero power. During phase two measurements were repeated at several power levels, at equilibrium xenon poisoning. This report includes experimental data of flux distributions and absolute values of the thermal and fast neutron flux in the RA reactor experimental channels and values of cadmium ratio for determining the neutron epithermal flux. Data related to calibration of regulatory rods for cold un poisoned core are included. [Serbo-Croat] Svrha merenja je odredjivanje neutronskog fluksa u reaktoru RA. S obzirom na uvecani broj tehnoloskih kanala of 56 na 68 u vezi projekta VISA-2, bilo je potrebno ponovo dovesti reaktora RA do kriticnosti i izvrsiti merenja karakteristika fluksa neutrona. Posebno je pripremljen 'program pustanja u pogon reaktora RA', koji je sadrzan u ovom dokumentu. Program merenja bio je podeljen na dve faze. Prva faza je merenje fluksa pre podizanju reaktora na nominalnu snagu. Slicna merenja vrsena su i na vecim snagama u drugoj fazi, pod uslovima ravnoteznog zatrovanja reaktora ksenonom, jer se tada pokazuju izvesne promene u odgovarajucim karakteristikama fluksa neutrona. Ovaj izvestaj sadrzi merene vrednosti raspodele fluksa i apsolutne vrednosti termalnih i brzih neutrona kao i kadmijumskih odnosa koji su korisceni za odredjivanje fluksa epitermalnih neutrona. Opisana je kalibracija regulacionih sipki za hladan nezatrovan reaktor.

  15. Adapting a Fourier pseudospectral method to Dirichlet boundary conditions for Rayleigh-Bénard convection

    Directory of Open Access Journals (Sweden)

    I. C. Ramos

    2015-10-01

    Full Text Available We present the adaptation to non-free boundary conditions of a pseudospectral method based on the (complex Fourier transform. The method is applied to the numerical integration of the Oberbeck-Boussinesq equations in a Rayleigh-Bénard cell with no-slip boundary conditions for velocity and Dirichlet boundary conditions for temperature. We show the first results of a 2D numerical simulation of dry air convection at high Rayleigh number (. These results are the basis for the later study, by the same method, of wet convection in a solar still. Received: 20 Novembre 2014, Accepted: 15 September 2015; Edited by: C. A. Condat, G. J. Sibona; DOI:http://dx.doi.org/10.4279/PIP.070015 Cite as: I C Ramos, C B Briozzo, Papers in Physics 7, 070015 (2015

  16. Seafloor age dependence of Rayleigh wave phase velocities in the Indian Ocean

    Science.gov (United States)

    Godfrey, Karen E.; Dalton, Colleen A.; Ritsema, Jeroen

    2017-05-01

    Variations in the phase velocity of fundamental-mode Rayleigh waves across the Indian Ocean are determined using two inversion approaches. First, variations in phase velocity as a function of seafloor age are estimated using a pure-path age-dependent inversion method. Second, a two-dimensional parameterization is used to solve for phase velocity within 1.25° × 1.25° grid cells. Rayleigh wave travel time delays have been measured between periods of 38 and 200 s. The number of measurements in the study area ranges between 4139 paths at a period of 200 s and 22,272 paths at a period of 40 s. At periods Rodriguez Triple Junction and the Australian-Antarctic Discordance and anomalously low velocities immediately to the west of the Central Indian Ridge.

  17. GRAVITATIONALLY UNSTABLE FLAMES: RAYLEIGH-TAYLOR STRETCHING VERSUS TURBULENT WRINKLING

    International Nuclear Information System (INIS)

    Hicks, E. P.; Rosner, R.

    2013-01-01

    In this paper, we provide support for the Rayleigh-Taylor-(RT)-based subgrid model used in full-star simulations of deflagrations in Type Ia supernovae explosions. We use the results of a parameter study of two-dimensional direct numerical simulations of an RT unstable model flame to distinguish between the two main types of subgrid models (RT or turbulence dominated) in the flamelet regime. First, we give scalings for the turbulent flame speed, the Reynolds number, the viscous scale, and the size of the burning region as the non-dimensional gravity (G) is varied. The flame speed is well predicted by an RT-based flame speed model. Next, the above scalings are used to calculate the Karlovitz number (Ka) and to discuss appropriate combustion regimes. No transition to thin reaction zones is seen at Ka = 1, although such a transition is expected by turbulence-dominated subgrid models. Finally, we confirm a basic physical premise of the RT subgrid model, namely, that the flame is fractal, and thus self-similar. By modeling the turbulent flame speed, we demonstrate that it is affected more by large-scale RT stretching than by small-scale turbulent wrinkling. In this way, the RT instability controls the flame directly from the large scales. Overall, these results support the RT subgrid model.

  18. Research nuclear reactor RA - Annual Report 1989

    International Nuclear Information System (INIS)

    Sotic, O.

    1989-12-01

    Annual report concerning the project 'RA research nuclear reactor' for 1989, financed by the Serbian ministry of science is divided into two parts. First part is concerned with RA reactor operation and maintenance, which is the task of the Division for reactor engineering of the Institute for multidisciplinary studies and RA reactor engineering. Second part deals with radiation protection activities at the RA reactor which is the responsibility of the Institute for radiation protection. Scientific council of the Institute for multidisciplinary studies and RA reactor engineering has stated that this report describes adequately the activity and tasks fulfilled at the RA reactor in 1989. The scope and the quality of the work done were considered successful both concerning the maintenance and reconstruction, as well as radiation protection activities [sr

  19. RA Research nuclear reactor - Annual report 1987

    International Nuclear Information System (INIS)

    1987-12-01

    Annual report concerning the project 'RA research nuclear reactor' for 1987, financed by the Serbian ministry of science is divided into two parts. First part is concerned with RA reactor operation and maintenance, which is the task of the Division for reactor engineering of the Institute for multidisciplinary studies and RA reactor engineering. Second part deals with radiation protection activities at the RA reactor which is the responsibility of the Institute for radiation protection. Scientific council of the Institute for multidisciplinary studies and RA reactor engineering has stated that this report describes adequately the activity and tasks fulfilled at the RA reactor in 1989. The scope and the quality of the work done were considered successful both concerning the maintenance and reconstruction, as well as radiation protection activities [sr

  20. RA Research reactor, Annual report 1988

    International Nuclear Information System (INIS)

    Sotic, O.

    1988-12-01

    Annual report concerning the project 'RA research nuclear reactor' for 1989, financed by the Serbian ministry of science is divided into two parts. First part is concerned with RA reactor operation and maintenance, which is the task of the Division for reactor engineering of the Institute for multidisciplinary studies and RA reactor engineering. Second part deals with radiation protection activities at the RA reactor which is the responsibility of the Institute for radiation protection. Scientific council of the Institute for multidisciplinary studies and RA reactor engineering has stated that this report describes adequately the activity and tasks fulfilled at the RA reactor in 1989. The scope and the quality of the work done were considered successful both concerning the maintenance and reconstruction, as well as radiation protection activities [sr

  1. LCA versus RA - an introduction

    DEFF Research Database (Denmark)

    Olsen, Stig Irving

    2000-01-01

    Risk Assessment (RA) of chemicals is an environmental management tool used to assess the risk of specific chemicals, which are harmful to man or the environment under certain circumstances of use or in certain environmental recipients. Life Cycle Assessment (LCA) or environmental assessment...... of Industrial Products) developed in Denmark (Wenzel et al., 1997), respectively. The interactions between the two tools can be viewed from two different angles: 1. As a general reflection of how the tools supplement each other in the total environmental effort. 2. As an assessment of coincidences...... on Principles and Methods for Hazard and Risk Assessment)focuses on an assessment of the toxicological and ecotoxicological risks, the focus of this article's comparison of assessment principles, data requirements etc. will be on the assessment of toxicity and ecotoxicity in EDIP's impact assessment methodology...

  2. RA radiological characterization database application

    International Nuclear Information System (INIS)

    Steljic, M.M; Ljubenov, V.Lj. . E-mail address of corresponding author: milijanas@vin.bg.ac.yu; Steljic, M.M.)

    2005-01-01

    Radiological characterization of the RA research reactor is one of the main activities in the first two years of the reactor decommissioning project. The raw characterization data from direct measurements or laboratory analyses (defined within the existing sampling and measurement programme) have to be interpreted, organized and summarized in order to prepare the final characterization survey report. This report should be made so that the radiological condition of the entire site is completely and accurately shown with the radiological condition of the components clearly depicted. This paper presents an electronic database application, designed as a serviceable and efficient tool for characterization data storage, review and analysis, as well as for the reports generation. Relational database model was designed and the application is made by using Microsoft Access 2002 (SP1), a 32-bit RDBMS for the desktop and client/server database applications that run under Windows XP. (author)

  3. Optimum RA reactor fuelling scheme

    International Nuclear Information System (INIS)

    Strugar, P.; Nikolic, V.

    1965-10-01

    Ideal reactor refueling scheme can be achieved only by continuous fuel elements movement in the core, which is not possible, and thus approximations are applied. One of the possible approximations is discontinuous movement of fuel elements groups in radial direction. This enables higher burnup especially if axial exchange is possible. Analysis of refueling schemes in the RA reactor core and schemes with mixing the fresh and used fuel elements show that 30% higher burnup can be achieved by applying mixing, and even 40% if reactivity due to decrease in experimental space is taken into account. Up to now, mean burnup of 4400 MWd/t has been achieved, and the proposed fueling scheme with reduction of experimental space could achieve mean burnup of 6300 MWd/t which means about 25 Mwd/t per fuel channel [sr

  4. RA Reactor applications, Annex A

    International Nuclear Information System (INIS)

    Martinc, R.; Cupac, S.; Stanic, A.

    1990-01-01

    RA reactor was not operated during the past five years due to the renewal and reconstruction of the reactor systems, which in underway. In the period from 1986-1990, reactor was operated only 144 MWh in 1986, for the need of testing the reactor systems and possibility of irradiating 125 I. Reactor will not be operated in 1991 because of the exchange of complete instrumentation which is planned to be finished by the end of 1991. It is expected to start operation in May 1992. That is why this annex includes the plan of reactor operation for period of nine months starting from from the moment of start-up. It is planned to operate the reactor at 0.02 MW power first three months, to increase the power gradually and reach 3.5 MW after 8 months of operation. It is foreseen to operate the reactor at 4.7 MW from the tenth month on [sr

  5. Filtered Rayleigh Scattering Measurements in a Buoyant Flow Field

    National Research Council Canada - National Science Library

    Meents, Steven M

    2008-01-01

    Filtered Rayleigh Scattering (FRS) is a non-intrusive, laser-based flow characterization technique that consists of a narrow linewidth laser, a molecular absorption filter, and a high resolution camera behind the filter to record images...

  6. Rayleigh scattering and depolarization ratio in linear alkylbenzene

    International Nuclear Information System (INIS)

    Liu, Qian; Zhou, Xiang; Huang, Wenqian; Zhang, Yuning; Wu, Wenjie; Luo, Wentai; Yu, Miao; Zheng, Yangheng; Zhou, Li; Cao, Jun; Wang, Yifang

    2015-01-01

    It is planned to use linear alkylbenzene (LAB) as the organic solvent for the Jiangmen Underground Neutrino Observatory (JUNO) liquid scintillator detectors, due to its ultra-transparency. However, the current Rayleigh scattering length calculation for LAB disagrees with the experimental measurement. This paper reports for the first time that the Rayleigh scattering of LAB is anisotropic, with a depolarization ratio of 0.31±0.01(stat.)±0.01(sys.). We use an indirect method for Rayleigh scattering measurement with the Einstein–Smoluchowski–Cabannes formula, and the Rayleigh scattering length of LAB is determined to be 28.2±1.0 m at 430 nm

  7. Effectiveness of a web-based personalized rheumatoid arthritis risk tool with or without a health educator for knowledge of RA risk factors.

    Science.gov (United States)

    Prado, Maria G; Iversen, Maura D; Yu, Zhi; Miller Kroouze, Rachel; Triedman, Nellie A; Kalia, Sarah S; Lu, Bing; Green, Robert C; Karlson, Elizabeth W; Sparks, Jeffrey A

    2018-01-05

    To assess knowledge of rheumatoid arthritis (RA) risk factors among unaffected first-degree relatives (FDRs) and to study whether a personalized RA education tool increases risk factor knowledge. We performed a randomized controlled trial assessing RA educational interventions among 238 FDRs. The web-based Personalized Risk Estimator for RA (PRE-RA) tool displayed personalized RA risk results (genetics, autoantibodies, demographics, and behaviors) and educated about risk factors. Subjects were randomly assigned to: Comparison arm (standard RA education, n=80), PRE-RA arm (PRE-RA alone, n=78), or PRE-RA Plus arm (PRE-RA and a one-on-one session with a trained health educator, n=80). The RA Knowledge Score (RAKS, the number of 8 established RA risk factors identified as related to RA) was calculated at baseline and post-education (immediate/6 weeks/6 months/12 months). We compared RAKS and its components at each post-education point by randomization arm. At baseline before education, few FDRs identified behavioral RA risk factors (15.9% for dental health, 31.9% for smoking, 47.5% for overweight/obesity, and 54.2% for diet). After education, RAKS increased in all arms, higher in PRE-RA and PRE-RA Plus than Comparison at all post-education points (peducation (proportion agreeing smoking is a risk factor at 6 weeks: 83.1% in PRE-RA Plus arm, 71.8% in PRE-RA, and 43.1% in Comparison arms, peducation tool successfully increased RA risk factor knowledge. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  8. Rayleigh scattering under light-atom coherent interaction

    OpenAIRE

    Takamizawa, Akifumi; Shimoda, Koichi

    2012-01-01

    Semi-classical calculation of an oscillating dipole induced in a two-level atom indicates that spherical radiation from the dipole under coherent interaction, i.e., Rayleigh scattering, has a power level comparable to that of spontaneous emission resulting from an incoherent process. Whereas spontaneous emission is nearly isotropic and has random polarization generally, Rayleigh scattering is strongly anisotropic and polarized in association with incident light. In the case where Rabi frequen...

  9. Kinetic simulations of Rayleigh-Taylor instabilities

    International Nuclear Information System (INIS)

    Sagert, Irina; Bauer, Wolfgang; Colbry, Dirk; Howell, Jim; Staber, Alec; Strother, Terrance

    2014-01-01

    We report on an ongoing project to develop a large scale Direct Simulation Monte Carlo code. The code is primarily aimed towards applications in astrophysics such as simulations of core-collapse supernovae. It has been tested on shock wave phenomena in the continuum limit and for matter out of equilibrium. In the current work we focus on the study of fluid instabilities. Like shock waves these are routinely used as test-cases for hydrodynamic codes and are discussed to play an important role in the explosion mechanism of core-collapse supernovae. As a first test we study the evolution of a single-mode Rayleigh-Taylor instability at the interface of a light and a heavy fluid in the presence of a gravitational acceleration. To suppress small-wavelength instabilities caused by the irregularity in the separation layer we use a large particle mean free path. The latter leads to the development of a diffusion layer as particles propagate from one fluid into the other. For small amplitudes, when the instability is in the linear regime, we compare its position and shape to the analytic prediction. Despite the broadening of the fluid interface we see a good agreement with the analytic solution. At later times we observe the development of a mushroom like shape caused by secondary Kelvin-Helmholtz instabilities as seen in hydrodynamic simulations and consistent with experimental observations.

  10. Acoustofluidic particle dynamics: Beyond the Rayleigh limit.

    Science.gov (United States)

    Baasch, Thierry; Dual, Jürg

    2018-01-01

    In this work a numerical model to calculate the trajectories of multiple acoustically and hydrodynamically interacting spherical particles is presented. The acoustic forces are calculated by solving the fully coupled three-dimensional scattering problem using finite element software. The method is not restricted to single re-scattering events, mono- and dipole radiation, and long wavelengths with respect to the particle diameter, thus expanding current models. High frequency surface acoustic waves have been used in the one cell per well technology to focus individual cells in a two-dimensional wave-field. Sometimes the cells started forming clumps and it was not possible to focus on individual cells. Due to a lack of existing theory, this could not be fully investigated. Here, the authors use the full dynamic simulations to identify limiting factors of the one-cell-per-well technology. At first, the authors demonstrate good agreement of the numerical model with analytical results in the Rayleigh limiting case. A frequency dependent stability exchange between the pressure and velocity was then demonstrated. The numerical formulation presented in this work is relatively general and can be used for a multitude of different high frequency applications. It is a powerful tool in the analysis of microscale acoustofluidic devices and processes.

  11. On the interaction of Rayleigh surface waves with structures

    International Nuclear Information System (INIS)

    Simpson, I.C.

    1976-12-01

    A two-dimensional soil-structure interaction analysis is carried out for transient Rayleigh surface waves that are incident on a structure. The structure is modelled by a three-degree of freedom rigid basemat to which is attached a flexible superstructure, modelled by a single mass-spring system. The structural responses to a given Rayleigh wave train are compared with those that would have been obtained if the free-field acceleration-time history had been applied as a normally incident body wave. The results clearly exhibit the 'frequency filtering' effects of the rigid basemat on the incident Rayleigh waves. It is shown that, if seismic excitation of a structure is, in fact, due to Rayleigh surface waves, then an analysis assuming normally incident body waves can considerably over-estimate structural response, both at basemat level for horizontal and vertical oscillations of the superstructure. However, in the examples considered here, relatively large rocking effects were induced by the Rayleigh waves, thus giving maximum horizontal accelerations in the superstructure that were of comparable magnitude for Rayleigh and normally incident body waves. (author)

  12. Distribution of 226Ra and 228Ra in drinking water and dose assessment

    International Nuclear Information System (INIS)

    Ajay Kumar; Sugandhi, S.; Usha, N.; Rupali, K.; Gurg, R.P.

    2002-01-01

    The radioactivity concentrations of 226 Ra and 228 Ra have been analysed in 123 drinking water samples received from different regions of India. The maximum concentrations of 226 Ra and 228 Ra in drinking water are 8 mBq/l and 11.5 mBq/l respectively. The higher doses due to intake of 228 Ra through drinking water suggests that 228 Ra should also be measured in the assessment of ingestion dose to the population. The estimated committed effective doses range from 0.082 to 2.45 μSv/year and from 1.53 to 8.81 μSv/year for the ingestion of 226 Ra and 228 Ra respectively. (author)

  13. Operation and maintenance of the RA reactor, RA Research reactor. Annual report 1976; Pogon i odrzavanje reaktora RA, Izvestaj o radu u 1976. godini

    Energy Technology Data Exchange (ETDEWEB)

    Martinc, R [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1976-12-15

    During 1976 the Ra reactor was operating for about 30% shorter period than usual. The reason were extraordinary repair activities within regular and investment maintenance as well as repair of failures caused by neglected maintenance during previous 6 years. Delay was caused by unavailability of fuel (2% enriched fuel elements are spent) and the new 80% enriched fuel demanded experimental and theoretical analyses before being introduced into the core. Safety analyses concerned with using 80% enriched fuel both experimental and theoretical were successfully fulfilled. The December 1976 successful experimental campaign can be marked as end of the 17 years period of using 2% enriched fuel and start of the new period of using highly enriched fuel. This is significant not only for the reactor itself but for the users, because it would result in increase of neutron flux by 50% with the increase of costs by only 4%. Demand was submitted for obtaining the final license for transition operating regime with highly enriched fuel which would save at least 2 200 000 dinars. This will enable reactor operation in 1977 and later on, without interruption by 'critical' and other experiments related to new highly enriched fuel. A high number of repair and other urgent activities were fulfilled in order to enable safe operation. Some of these activities were done never before and some were neglected during past 6 years. The most important tasks were: purchase of Al tubes made of special alloy, fabrication and mounting of the fuel channel; overall investigation of reactor vessel leakage; repair of the heavy water pump; exchange of two vertical channels. basic equipment for construction of emergency cooling system was purchased. Hot cells are equipped for independent utilisation. [Serbo-Croat] Reaktor RA je u 1976. godini radio za oko 30% krace vreme od uobicajenog. Razlog su bill izuzetno veliki obim remontnih i drugih radova u okviru tekuceg i investicionog odrzavanja, kao i krupnih

  14. Determination of ''226Ra by Alpha Spectrometry by Using ''225Ra as Yield Tracer

    International Nuclear Information System (INIS)

    Crespo, M. T.; Oller, O.

    1999-01-01

    A method for the determination of low-level ''226 Ra in environmental and geological samples by alpha spectrometry is described. The method is based on the use of ''225 Ra from ''229 Th as yield tracer and has been developed to analyze U, Th and Ra in the same sample. (Author) 12 refs

  15. Phosphoproteome and Transcriptome of RA-Responsive and RA-Resistant Breast Cancer Cell Lines.

    Directory of Open Access Journals (Sweden)

    Marilyn Carrier

    Full Text Available Retinoic acid (RA, the main active vitamin A metabolite, controls multiple biological processes such as cell proliferation and differentiation through genomic programs and kinase cascades activation. Due to these properties, RA has proven anti-cancer capacity. Several breast cancer cells respond to the antiproliferative effects of RA, while others are RA-resistant. However, the overall signaling and transcriptional pathways that are altered in such cells have not been elucidated. Here, in a large-scale analysis of the phosphoproteins and in a genome-wide analysis of the RA-regulated genes, we compared two human breast cancer cell lines, a RA-responsive one, the MCF7 cell line, and a RA-resistant one, the BT474 cell line, which depicts several alterations of the "kinome". Using high-resolution nano-LC-LTQ-Orbitrap mass spectrometry associated to phosphopeptide enrichment, we found that several proteins involved in signaling and in transcription, are differentially phosphorylated before and after RA addition. The paradigm of these proteins is the RA receptor α (RARα, which was phosphorylated in MCF7 cells but not in BT474 cells after RA addition. The panel of the RA-regulated genes was also different. Overall our results indicate that RA resistance might correlate with the deregulation of the phosphoproteome with consequences on gene expression.

  16. Operators retraining in RA-1

    International Nuclear Information System (INIS)

    Pereira, R; Daoud, A

    2012-01-01

    The nuclear activity in Argentina has its foundational milestone in the creation of the Comision Nacional de EnergIa Atomica in 1950. Achievements since then, linked to the area of nuclear reactors and nuclear fuel materials, fuel cycle facilities and the applications of nuclear technology in medicine, industry, agriculture, food preservation, environmental studies and many others, have relied on personnel trained in this specific technology in both professional and technical level. This training has been done in most cases in the exclusive scope of CNEA. Eventually CNEA has been linked with the University to ensure that personnel training concerned to work done in the nuclear field had guarantees of formality and excellence. The creation of the Instituto de Tecnologia Nuclear Dan Beninson that, under an agreement with the Universidad Nacional de General San Martin, has set up an enabling environment for the training of professionals and university technicians to serve with the multiple and growing use of this technology. On the other hand the Institute has been issuing, along with its careers, specialized courses that, in some cases, have been requested by CNEA's nuclear installations and companies related to the nuclear sector. In particular, the Specialization in Nuclear Reactors and its Fuel Cycle (ERCC) and the Courses of Introduction to Nuclear Technology-Complementary training for Installations Personnel Class I (CI-CC), this last, recognized by the ARN as a requirement for applying to the individual licensing examination, providing work experience in the RA-1 reactor among which we can find commissioning, control rods calibration by various methods and calculations of reactivity. With this practical framework developed in the RA-1 and the academic support provided by the Instituto de Tecnologia Nuclear Dan Beninson it was developed a training program for nuclear reactors operators. Let us stress that this research reactor has been forming generations

  17. Direct numerical simulations of type Ia supernovae flames II: The Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Bell, J.B.; Day, M.S.; Rendleman, C.A.; Woosley, S.E.; Zingale, M.

    2004-01-01

    A Type Ia supernova explosion likely begins as a nuclear runaway near the center of a carbon-oxygen white dwarf. The outward propagating flame is unstable to the Landau-Darrieus, Rayleigh-Taylor, and Kelvin-Helmholtz instabilities, which serve to accelerate it to a large fraction of the speed of sound. We investigate the Rayleigh-Taylor unstable flame at the transition from the flamelet regime to the distributed-burning regime, around densities of 10e7 gm/cc, through detailed, fully resolved simulations. A low Mach number, adaptive mesh hydrodynamics code is used to achieve the necessary resolution and long time scales. As the density is varied, we see a fundamental change in the character of the burning--at the low end of the density range the Rayleigh-Taylor instability dominates the burning, whereas at the high end the burning suppresses the instability. In all cases, significant acceleration of the flame is observed, limited only by the size of the domain we are able to study. We discuss the implications of these results on the potential for a deflagration to detonation transition

  18. Rayleigh-Taylor-instability evolution in colliding-plasma-jet experiments with magnetic and viscous stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Colin Stuart [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States); Univ. of Washington, Seattle, WA (United States)

    2015-01-15

    The Rayleigh-Taylor instability causes mixing in plasmas throughout the universe, from micron-scale plasmas in inertial confinement fusion implosions to parsec-scale supernova remnants. The evolution of this interchange instability in a plasma is influenced by the presence of viscosity and magnetic fields, both of which have the potential to stabilize short-wavelength modes. Very few experimental observations of Rayleigh-Taylor growth in plasmas with stabilizing mechanisms are reported in the literature, and those that are reported are in sub-millimeter scale plasmas that are difficult to diagnose. Experimental observations in well-characterized plasmas are important for validation of computational models used to make design predictions for inertial confinement fusion efforts. This dissertation presents observations of instability growth during the interaction between a high Mach-number, initially un-magnetized plasma jet and a stagnated, magnetized plasma. A multi-frame fast camera captures Rayleigh-Taylor-instability growth while interferometry, spectroscopy, photodiode, and magnetic probe diagnostics are employed to estimate plasma parameters in the vicinity of the collision. As the instability grows, an evolution to longer mode wavelength is observed. Comparisons of experimental data with idealized magnetohydrodynamic simulations including a physical viscosity model suggest that the observed instability evolution is consistent with both magnetic and viscous stabilization. These data provide the opportunity to benchmark computational models used in astrophysics and fusion research.

  19. Coherent structures in ablatively compressed ICF targets and Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Pant, H.C.; Desai, T.

    1996-01-01

    One of the major issues in laser induced inertial confinement fusion (ICF) is a stable ablative compression of spherical fusion pellets. The main impediment in achievement of this objective is Rayleigh-Taylor instability at the pellet's ablation front. Under sufficiently high acceleration this instability can grow out of noise. However, it can also arise either due to non-uniform laser intensity distribution over the pellet surface or due to pellet wall areal mass irregularity. Coherent structures in the dense target behind the ablation front can be effectively utilised for stabilisation of the Rayleigh-Taylor phenomenon. Such coherent structures in the form of a super lattice can be created by doping the pellet pusher with high atomic number (Z) micro particles. A compressed-cool pusher under laser irradiation behaves like a strongly correlated non ideal plasma when compressed to sufficiently high density such that the non ideality parameter exceeds unity. Moreover, the nonideality parameter for high Z microinclusions may exceed a critical value of 180 and as a consequence they remain in the form of intact clusters, maintaining the superlattice intact during ablative acceleration. Micro-hetrogeneity and its superlattice plays an important role in stabilization of Rayleigh-Taylor instability, through a variety of mechanisms. (orig.)

  20. Temperature boundary layer profiles in turbulent Rayleigh-Benard convection

    Science.gov (United States)

    Ching, Emily S. C.; Emran, Mohammad S.; Horn, Susanne; Shishkina, Olga

    2017-11-01

    Classical boundary-layer theory for steady flows cannot adequately describe the boundary layer profiles in turbulent Rayleigh-Benard convection. We have developed a thermal boundary layer equation which takes into account fluctuations in terms of an eddy thermal diffusivity. Based on Prandtl's mixing length ideas, we relate the eddy thermal diffusivity to the stream function. With this proposed relation, we can solve the thermal boundary layer equation and obtain a closed-form expression for the dimensionless mean temperature profile in terms of two independent parameters: θ(ξ) =1/b∫0b ξ [ 1 +3a3/b3(η - arctan(η)) ] - c dη , where ξ is the similarity variable and the parameters a, b, and c are related by the condition θ(∞) = 1 . With a proper choice of the parameters, our predictions of the temperature profile are in excellent agreement with the results of our direct numerical simulations for a wide range of Prandtl numbers (Pr), from Pr=0.01 to Pr=2547.9. OS, ME and SH acknowledge the financial support by the Deutsche Forschungsgemeinschaft (DFG) under Grants Sh405/4-2 (Heisenberg fellowship), Sh405/3-2 and Ho 5890/1-1, respectively.

  1. The dynamics of droplets in moist Rayleigh-Benard turbulence

    Science.gov (United States)

    Chandrakar, Kamal Kant; van der Voort, Dennis; Kinney, Greg; Cantrell, Will; Shaw, Raymond

    2017-11-01

    Clouds are an intricate part of the climate, and strongly influence atmospheric dynamics and radiative balances. While properties such as cloud albedo and precipitation rate are large scale effects, these properties are determined by dynamics on the microscale, such droplet sizes, liquid water content, etc. The growth of droplets from condensation is dependent on a multitude of parameters, such as aerosol concentration (nucleation sites) and turbulence (scalar fluctuations and coalescence). However, the precise mechanism behind droplet growth and clustering in a cloud environment is still unclear. In this investigation we use a facility called the Pi Chamber to generate a (miniature) cloud in a laboratory setting with known boundary conditions, such as aerosol concentration, temperature, and humidity. Through the use of particle imaging velocimetry (PIV) on the droplets generated in the cloud, we can investigate the dynamics of these cloud droplets in the convective (Rayleigh-Benard) turbulence generated through an induced temperature gradient. We show the influence of the temperature gradient and Froude number (gravity forces) on the changing turbulence anisotropy, large scale circulation, and small-scale dissipation rates. This work was supported by National Science Foundation Grant AGS-1623429.

  2. Potential Flow Model for Compressible Stratified Rayleigh-Taylor Instability

    Science.gov (United States)

    Rydquist, Grant; Reckinger, Scott; Owkes, Mark; Wieland, Scott

    2017-11-01

    The Rayleigh-Taylor Instability (RTI) is an instability that occurs when a heavy fluid lies on top of a lighter fluid in a gravitational field, or a gravity-like acceleration. It occurs in many fluid flows of a highly compressive nature. In this study potential flow analysis (PFA) is used to model the early stages of RTI growth for compressible fluids. In the localized region near the bubble tip, the effects of vorticity are negligible, so PFA is applicable, as opposed to later stages where the induced velocity due to vortices generated from the growth of the instability dominate the flow. The incompressible PFA is extended for compressibility effects by applying the growth rate and the associated perturbation spatial decay from compressible linear stability theory. The PFA model predicts theoretical values for a bubble terminal velocity for single-mode compressible RTI, dependent upon the Atwood (A) and Mach (M) numbers, which is a parameter that measures both the strength of the stratification and intrinsic compressibility. The theoretical bubble terminal velocities are compared against numerical simulations. The PFA model correctly predicts the M dependence at high A, but the model must be further extended to include additional physics to capture the behavior at low A. Undergraduate Scholars Program - Montana State University.

  3. Modal model for the nonlinear multimode Rayleigh endash Taylor instability

    International Nuclear Information System (INIS)

    Ofer, D.; Alon, U.; Shvarts, D.; McCrory, R.L.; Verdon, C.P.

    1996-01-01

    A modal model for the Rayleigh endash Taylor (RT) instability, applicable at all stages of the flow, is introduced. The model includes a description of nonlinear low-order mode coupling, mode growth saturation, and post-saturation mode coupling. It is shown to significantly extend the range of applicability of a previous model proposed by Haan, to cases where nonlinear mode generation is important. Using the new modal model, we study the relative importance of mode coupling at late nonlinear stages and resolve the difference between cases in which mode generation assumes a dominant role, leading to the late time inverse cascade of modes and loss of memory of initial conditions, and cases where mode generation is not important and memory of initial conditions is retained. Effects of finite density ratios (Atwood number A<1) are also included in the model and the difference between various measures of the mixing zone penetration depth for A<1 is discussed. copyright 1996 American Institute of Physics

  4. Characterizing G-Loading, Swirl Direction, and Rayleigh Losses in an Ultra Compact Combustor

    Science.gov (United States)

    2013-07-01

    low Mach numbers to avoid these pressure losses while burning. Radtke [25] used a modified version of the Anthenien et al. [9] rig to study pressure...losses in the combustor due to Rayleigh effects. Radtke saw this increase in Mach number when comparing reacting and non-reacting cases, seen in...Anderson, W., Radtke , J., King, P., Thornburg, H., Zelina, J., Sekar, B., “Effects of Main Swirl Direction on High-g Combustion,” 44th AIAA/ASME/SAE

  5. Hyper-Rayleigh scattering in centrosymmetric systems

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Mathew D.; Ford, Jack S.; Andrews, David L., E-mail: david.andrews@physics.org [School of Chemistry, University of East Anglia, Norwich NR4 7TJ (United Kingdom)

    2015-09-28

    Hyper-Rayleigh scattering (HRS) is an incoherent mechanism for optical second harmonic generation. The frequency-doubled light that emerges from this mechanism is not emitted in a laser-like manner, in the forward direction; it is scattered in all directions. The underlying theory for this effect involves terms that are quadratic in the incident field and involves an even-order optical susceptibility (for a molecule, its associated hyperpolarizability). In consequence, HRS is often regarded as formally forbidden in centrosymmetric media. However, for the fundamental three-photon interaction, theory based on the standard electric dipole approximation, representable as E1{sup 3}, does not account for all experimental observations. The relevant results emerge upon extending the theory to include E1{sup 2}M1 and E1{sup 2}E2 contributions, incorporating one magnetic dipolar or electric quadrupolar interaction, respectively, to a consistent level of multipolar expansion. Both additional interactions require the deployment of higher orders in the multipole expansion, with the E1{sup 2}E2 interaction analogous in rank and parity to a four-wave susceptibility. To elicit the correct form of response from fluid or disordered media invites a tensor representation which does not oversimplify the molecular components, yet which can produce results to facilitate the interpretation of experimental observations. The detailed derivation in this work leads to results which are summarized for the following: perpendicular detection of polarization components both parallel and perpendicular to the pump radiation, leading to distinct polarization ratio results, as well as a reversal ratio for forward scattered circular polarizations. The results provide a route to handling data with direct physical interpretation, to enable the more sophisticated design of molecules with sought nonlinear optical properties.

  6. Model for the induction of bone cancer by 224Ra

    International Nuclear Information System (INIS)

    Groer, P.G.; Marshall, J.H.

    1976-01-01

    A mathematical model for the transformation of normal endosteal cells into malignant tumor cells by α irradiation is applied to 224 Ra. The model postulates that a normal endosteal cell near the bone surface is transformed into a malignant cell by three consecutive events. The first two events are the initiation events. The probability of their occurrence is proportional to the absorbed endosteal dose and they generate dormant tumor cells. These dormant tumor cells are promoted by the third event, the promotion event. The probability of this last event is proportional to the rate of bone remodeling but independent of the radiation dose. In competition with these transforming events is the killing of any endosteal cell by α irradiation. Killing is balanced by replacement of killed endosteal cells by normal stem cells. This model provides the following interesting predictions for the human 224 Ra cases: after the decay of 224 Ra the tumor rate decreases exponentially at a rate proportional to the bone turnover rate; for exposure to the same dose the model predicts an increased number of tumors for protracted exposure (i.e., exposure at a lower dose rate). Implications of this model for the therapy of ankylosing spondylitis are discussed. Statistical procedures are suggested for comparison of this theoretical model with the existing data on the induction of osteosarcomas by 224 Ra in man

  7. Study of Rayleigh-Love coupling from Spatial Gradient Observation

    Science.gov (United States)

    Lin, C. J.; Hosseini, K.; Donner, S.; Vernon, F.; Wassermann, J. M.; Igel, H.

    2017-12-01

    We present a new method to study Rayleigh-Love coupling. Instead of using seismograms solely, where ground motion is recorded as function of time, we incorporate with rotation and strain, also called spatial gradient where ground is represented as function of distance. Seismic rotation and strain are intrinsic different observable wavefield so are helpful to indentify wave type and wave propagation. A Mw 7.5 earthquake on 29 March 2015 occurred in Kokopo, Papua New Guinea recorded by a dense seismic array at PFO, California are used to obtaint seismic spatial gradient. We firstly estimate time series of azimuthal direction and phase velocity of SH wave and Rayleigh wave by analyzing collocated seismograms and rotations. This result also compares with frequency wavenumber methods using a nearby ANZA seismic array. We find the direction of Rayleigh wave fits well with great-circle back azimuth during wave propagation, while the direction of Love wave deviates from that, especially when main energy of Rayleigh wave arrives. From the analysis of cross-correlation between areal strain and vertical rotation, it reveals that high coherence, either positive or negative, happens at the same time when Love wave deparate from great-circle path. We also find the observed azimuth of Love wave and polarized particle motion of Rayleigh wave fits well with the fast direction of Rayleigh wave, for the period of 50 secs. We conclude the cause of deviated azimuth of Love wave is due to Rayleigh-Love coupling, as surface wave propagates through the area with anisotropic structure.

  8. Determination of 226Ra and 228Ra in surface seawater around Sagami bay and its vicinity

    International Nuclear Information System (INIS)

    Nakano-Ohta, T.; Kubota, T.; Mahara, Y.; Yoshikawa, M.; Sato, J.

    2006-01-01

    Activity ratios of 228 Ra/ 226 Ra in surface seawaters were observed at 5 ports of Izu-Oshima, Ajiro port of Sagami bay and Umizuri park of Tokyo bay. The 228 Ra/ 226 Ra activity ratio in surface seawaters were from 0.2 to 0.7 for Izu-Oshima, from 0.2 to 0.7 for Ajiro port and from 0.6 to 0.8 for Tokyo bay. The activity ratio in surface seawaters of Izu-Oshima and Atami of Sagami bay showed lower in spring and highly in autumn, while narrow variation pattern was observed in Umizuri park of Tokyo bay. The observed variation patterns of 228 Ra/ 226 Ra in surface seawaters at Izu-oshima, Ajiro park and Umizuri park may be reflected by difference of contribution from amount of seawater far off coast with low 228 Ra concentration. (author)

  9. Preparation of 227Ac/223Ra by neutron irradiation of 226Ra

    International Nuclear Information System (INIS)

    Ekaterina Kukleva; Jan Kozempel; Martin Vlk; Petra Micolova; Dusan Vopalka

    2015-01-01

    Radium-223 is a prospective alpha-emitter for targeted radionuclide therapy. Although 223 Ra is formed naturally by the decay of 235 U, for practical reasons its preparation involves neutron irradiation of 226 Ra. The β - decay of the 227 Ra (T ½ = 43 min) produced via 226 Ra(n,γ) 227 Ra reaction leads to 227 Ac, a mother nuclide of 227 Th and subsequently 223 Ra. Radium target material is generally available in multigram quantities from historical stock. The main aim of this study was to experimentally as well as theoretically evaluate and verify the available literature data on production of 227 Ac/ 223 Ra. According to the data obtained from the γ-spectra, the approximate yield values were determined and effective cross section value for the 227 Ac production was calculated to 14 ± 4 b. (author)

  10. RA Research reactor, Annual report 1971

    International Nuclear Information System (INIS)

    Milosevic, D. et al.

    1971-12-01

    During 1971, the RA Reactor was operated at nominal power of 6.5 MW for 190 days, and 50 days at lower power levels. Total production mounted to 31606 MWh which is 5.3% higher than planned, and the highest annual level since the reactor started operation. Reactor was used for irradiation and experiments according to the demand of 425 users, of which 370 from the Institute and 55 external users. This report contains detailed data about reactor power and experiments performed in 1971. Discrepancies from the action plan, meaning higher production was achieved in June and December due to special demand of the users. Total number of interruptions was lower than during all the previous years, and were caused mainly due to power cuts during reactor operation. There was no longer interruption caused by failures of the equipment. There was only on scram shutdown during this year caused by a false signal of the reactor control instrumentation. Shorter interruptions resulted from breaking of connectors in the technical water pipe system caused by soil sliding near the pumping station on the Danube. Total personnel exposure dose was lower than during previous years. There was no accident nor any event that could be called accidental. Decontamination od surfaces was less than during previous years. It was concluded that the successful operation in 1971 resulted from efficient work during past years. But, some of the activities were interrupted due to undefined policy concerned with operation of the RA reactor and financial issues. This involves study of the possibility to use highly enriched fuel that would increase the useful neutron flux and the reactor compatibility with similar reactors for the future ten years. Another project that has been interrupted is construction of the emergency core cooling system which is important for the reactor safety. Financial problems have influenced not only the reactor operation but the number of employees, which could cause negative

  11. Rayleigh scattering in few-mode optical fibers.

    Science.gov (United States)

    Wang, Zhen; Wu, Hao; Hu, Xiaolong; Zhao, Ningbo; Mo, Qi; Li, Guifang

    2016-10-24

    The extremely low loss of silica fibers has enabled the telecommunication revolution, but single-mode fiber-optic communication systems have been driven to their capacity limits. As a means to overcome this capacity crunch, space-division multiplexing (SDM) using few-mode fibers (FMF) has been proposed and demonstrated. In single-mode optical fibers, Rayleigh scattering serves as the dominant mechanism for optical loss. However, to date, the role of Rayleigh scattering in FMFs remains elusive. Here we establish and experimentally validate a general model for Rayleigh scattering in FMFs. Rayleigh backscattering not only sets the intrinsic loss limit for FMFs but also provides the theoretical foundation for few-mode optical time-domain reflectometry, which can be used to probe perturbation-induced mode-coupling dynamics in FMFs. We also show that forward inter-modal Rayleigh scattering ultimately sets a fundamental limit on inter-modal-crosstalk for FMFs. Therefore, this work not only has implications specifically for SDM systems but also broadly for few-mode fiber optics and its applications in amplifiers, lasers, and sensors in which inter-modal crosstalk imposes a fundamental performance limitation.

  12. Rayleigh scattering in an emitter-nanofiber-coupling system

    Science.gov (United States)

    Tang, Shui-Jing; Gao, Fei; Xu, Da; Li, Yan; Gong, Qihuang; Xiao, Yun-Feng

    2017-04-01

    Scattering is a general process in both fundamental and applied physics. In this paper, we investigate Rayleigh scattering of a solid-state-emitter coupled to a nanofiber, by S -matrix-like theory in k -space description. Under this model, both Rayleigh scattering and dipole interaction are studied between a two-level artificial atom embedded in a nanocrystal and fiber modes (guided and radiation modes). It is found that Rayleigh scattering plays a critical role in the transport properties and quantum statistics of photons. On the one hand, Rayleigh scattering produces the transparency in the optical transmitted field of the nanofiber, accompanied by the change of atomic phase, population, and frequency shift. On the other hand, the interference between two kinds of scattering fields by Rayleigh scattering and dipole transition modifies the photon statistics (second-order autocorrelation function) of output fields, showing a strong wavelength dependence. This study provides guidance for the solid-state emitter acting as a single-photon source and can be extended to explore the scattering effect in many-body physics.

  13. Radiation protection at reactors RA and RB

    International Nuclear Information System (INIS)

    Ninkovic, M.

    2003-02-01

    Radiation protection activities at the RA and RB reactors are imposed by the existing legal regulations and international recommendations in this field. This annual report contains five parts which cover the following topics: Radiation safety, dosimetry control and technical radiation protection at reactors RA and RB; Handling of radioactive waste, actions and decontamination; Control of the environment (surroundings of RA and RB reactors) and meteorological measurements; Control of internal contamination and internal exposure; Health control od personnel exposed to radiation. Personnel as well as financial data are part of this report

  14. Operation and maintenance of the RA reactor; Pogon i odrzavanje reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, M; Zecevic, V [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    During 1961 the RA reactor was used for irradiation of samples for 258 users ( from which 188 from the Institute) and for 34 experiments, this means productions of 5958 MWh. The production was almost four times bigger than during previous year due to the demand of the Laboratories of the Institute. Burnup of the fuel from the first batch was about 30%. This means that the operation time could be much higher. Number of safety shut-downs was 11. The reasons were related to electrical faults, 9 occurrences, failure of the instrument for reactor period measurement, once, and failure of the pump once. This report covers state and operation data of the reactor components, control instruments, devices for reactor protection, dosimetry, heavy water system, helium system, mechanical and electrical equipment. Problems related to training of the staff and lack of personnel are mentioned as well.

  15. Reproduction of the RA reactor fuel element fabrication; Reprodukcija izrade gorivnog elementa za reaktor RA

    Energy Technology Data Exchange (ETDEWEB)

    Novakovic, M [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    This document includes the following nine reports: Final report on task 08/12 - testing the Ra reactor fuel element; design concept for fabrication of RA reactor fuel element; investigation of the microstructure of the Ra reactor fuel element; Final report on task 08/13 producing binary alloys with Al, Mo, Zr, Nb and B additions; fabrication of U-Al alloy; final report on tasks 08/14 and 08/16; final report on task 08/32 diffusion bond between the fuel and the cladding of the Ra reactor fuel element; Final report on task 08/33, fabrication of the RA reactor fuel element cladding; and final report on task 08/36, diffusion of solid state metals. Ovaj rad sadrzi devet priloga: 1. Zavrsni izvestaj o podzadatku 08/12, ispitivanje elementa goriva reaktora RA; 2. Koncepcija izrade gorivnog elementa reaktora RA; 3. Ispitivanje mikrostrukture gorivnog elementa reaktora RA; 4. Zavrsni izvestaj o podzadatku 08/13, dobijanje binarnih legura urana sa legirajucim komponentama Al, Mo, Zr, Nb i B; 5. Dobijanje legure U-Al; 6. Zavrsni izvestaj o podzadacima 08/14 i 08/16; 7. Zavrsni izvestaj o podzadatku 08/32, difuziona veza goriva i kosuljice gorivnog elementa reaktora RA; 8. Zavrsni izvestaj o podzadatku 08/33, izrada kosuljice gorivnog elementa reaktora RA; 9. Zavrsni izvestaj o podzadatku 08/36, difuzija kod metala u cvrstom stanju.

  16. The Rayleigh-Taylor instability in the spherical pinch

    International Nuclear Information System (INIS)

    Chen, H.B.; Hilko, B.; Panarella, E.

    1994-01-01

    The spherical pinch (SP) concept is an outgrowth of the inertial confinement model (ICF). Unlike the ICF where instabilities, especially the Rayleigh-Taylor instability, have been studied extensively, the instability study of the spherical pinch has just begun. The Raleigh-Taylor instability is investigated for the first time in the SP in the present work. By using the simple condition for the Rayleigh-Taylor instability ∇p · ∇p < O (density and pressure gradients have opposite direction), we have qualitatively identified the regions for development of instabilities in the SP. It is found that the explosion phase (central discharge) is stable and instabilities take place in the imploding phase. However, the growth rate for the instability is not in exponential form, and the appearance of the Rayleigh-Taylor instability does not prevent the main shock wave from converging to the center of the sphere

  17. Rayleigh-Taylor instability of cylindrical jets with radial motion

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiang M. [GE Nuclear, Wilmington, NC (United States); Schrock, V.E.; Peterson, P.F. [Univ. of California, Berkeley, CA (United States)

    1995-09-01

    Rayleigh-Taylor instability of an interface between fluids with different densities subjected to accelleration normal to itself has interested researchers for almost a century. The classic analyses of a flat interface by Rayleigh and Taylor have shown that this type of instability depends on the direction of acceleration and the density differences of the two fluids. Plesset later analyzed the stability of a spherically symmetric flows (and a spherical interface) and concluded that the instability also depends on the velocity of the interface as well as the direction and magnitude of radial acceleration. The instability induced by radial motion in cylindrical systems seems to have been neglected by previous researchers. This paper analyzes the Rayleigh-Taylor type of the spherical case, the radial velocity also plays an important role. As an application, the example of a liquid jet surface in an Inertial Confinement Fusion (ICF) reactor design is analyzed.

  18. Rayleigh-Taylor instability and mixing in SN 1987A

    International Nuclear Information System (INIS)

    Ebisuzaki, T.; Shigeyama, T.; Nomoto, K.

    1989-01-01

    The stability of the supernova ejecta is compared with the Rayleigh-Taylor instability for a realistic model of SN 1987A. A linear analysis indicates that the layers around the composition interface between the hydrogen-rich and helium zones, and become Rayleigh-Taylor unstable between the helium and metal zones. In these layers, the pressure increases outward because of deceleration due to the reverse shock which forms when the blast shock hits the massive hydrogen-rich envelope. On the contrary, the density steeply decreases outward because of the preexisting nuclear burning shell. Then, these layers undergo the Raleigh-Taylor instability because of the opposite signs of the pressure and density gradients. The estimated growth rate is larger than the expansion rate of the supernova. The Rayleigh-Taylor instability near the composition interface is likely to induce mixing, which has been strongly suggested from observations of SN 1987A. 25 refs

  19. Nonlinear saturation of the Rayleigh endash Taylor instability

    International Nuclear Information System (INIS)

    Das, A.; Mahajan, S.; Kaw, P.; Sen, A.; Benkadda, S.; Verga, A.

    1997-01-01

    A detailed numerical simulation of the nonlinear state of the Rayleigh endash Taylor instability has been carried out. There are three distinct phases of evolution where it is governed by the (i) linear effects, (ii) effects arising from the conventional nonlinear terms and (iii) subtle nonlinear effects arising through the coupling terms. During the third phase of evolution, there is a self-consistent generation of shear flow which saturates the Rayleigh endash Taylor instability even in situations (with periodic boundaries) where, in principle, an infinite amount of gravitational energy can be tapped. The Galerkin approximation is presented to provide an understanding of our numerical findings. Last, there is an attempt to provide a comprehensive understanding of the nonlinear state of the Rayleigh endash Taylor instability by comparing and contrasting this work with earlier studies. copyright 1997 American Institute of Physics

  20. Rayleigh wave ellipticity across the Iberian Peninsula and Morocco

    Science.gov (United States)

    Gómez García, Clara; Villaseñor, Antonio

    2015-04-01

    Spectral amplitude ratios between horizontal and vertical components (H/V ratios) from seismic records are useful to evaluate site effects, predict ground motion and invert for S velocity in the top several hundred meters. These spectral ratios can be obtained from both ambient noise and earthquakes. H/V ratios from ambient noise depend on the content and predominant wave types: body waves, Rayleigh waves, a mixture of different waves, etc. The H/V ratio computed in this way is assumed to measure Rayleigh wave ellipticity since ambient vibrations are dominated by Rayleigh waves. H/V ratios from earthquakes are able to determine the local crustal structure at the vicinity of the recording station. These ratios obtained from earthquakes are based on surface wave ellipticity measurements. Although long period (>20 seconds) Rayleigh H/V ratio is not currently used because of large scatter has been reported and uncertainly about whether these measurements are compatible with traditional phase and group velocity measurements, we will investigate whether it is possible to obtain stable estimates after collecting statistics for many earthquakes. We will use teleseismic events from shallow earthquakes (depth ≤ 40 km) between 2007 January 1 and 2012 December 31 with M ≥ 6 and we will compute H/V ratios for more than 400 stations from several seismic networks across the Iberian Peninsula and Morocco for periods between 20 and 100 seconds. Also H/V ratios from cross-correlations of ambient noise in different components for each station pair will be computed. Shorter period H/V ratio measurements based on ambient noise cross-correlations are strongly sensitive to near-surface structure, rather than longer period earthquake Rayleigh waves. The combination of ellipticity measurements based on earthquakes and ambient noise will allow us to perform a joint inversion with Rayleigh wave phase velocity. Upper crustal structure is better constrained by the joint inversion compared

  1. The decay scheme of 229Ra

    International Nuclear Information System (INIS)

    Yang, W.F.; Yuan, S.G.; Fang, K.M.; Shen, S.F.; Mou, W.T.; Zhang, X.Q.; Li, Z.Q.

    1997-01-01

    By bombarding the natural thorium targets with 14 MeV neutrons, 229 Ra was produced through the reaction 232 Th(n,α) 229 Ra. The radium activities were separated from the irradiated targets by coprecipitation with the BaCl 2 . A total of 18 new weak γ rays with energies of 14.5, 15.6, 18.8, 21.8, 22.5, 44.0, 47.5, 55.0, 63.0, 69.6, 93.6, 94.1, 98.5, 102.2, 104.5, 106.1, 161.1, and 171.5 keV which could be assigned to the decay of 229 Ra were observed in the isolated radium fractions employing high resolution HPGe detectors and γ(X)-γ coincidence methods. A decay scheme of 229 Ra based on these observations is proposed. (orig.). With 2 figs

  2. Understanding Rheumatoid Arthritis (RA): Treatment and Causes

    Science.gov (United States)

    ... this page please turn JavaScript on. Feature: Understanding Rheumatoid Arthritis (RA) Treatment and Causes Past Issues / Summer 2014 Table of Contents How Is Rheumatoid Arthritis Treated? Doctors have many ways to treat this ...

  3. RA Construction KC, LLC Information Sheet

    Science.gov (United States)

    RA Construction KC, LLC (the Company) is located in Gladstone, Missouri. The settlement involves renovation activities conducted at a property constructed prior to 1978, located in Kansas City, Missouri.

  4. RA Research nuclear reactor Part 1, RA Reactor operation and maintenance in 1987; Istrazivacki nuklearni reaktor RA Deo 1 - Pogon i odrzavanje nuklearnog reaktora RA u 1987. godini

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O; Martinc, R; Cupac, S; Sulem, B; Badrljica, R; Majstorovic, D; Sanovic, V [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1987-12-15

    RA research reacto was not operated due to the prohibition issued in 1984 by the Government of Serbia. Three major tasks were finished in order to fulfill the licensing regulations about safety of nuclear facilities which is the condition for obtaining permanent operation licence. These projects involved construction of the emergency cooling system, reconstruction of the existing special ventilation system, and renewal of the system for electric power supply of the reactor systems. Renewal of the RA reactor instrumentation system was initiated. Design project was done by the Russian Atomenergoeksport, and is foreseen to be completed by the end of 1988. The RA reactor safety report was finished in 1987. This annual report includes 8 annexes concerning reactor operation, activities of services and financial issues, and three special annexes: report on testing the emergency cooling system, report on renewal of the RA reactor and design specifications for reactor renewal and reconstruction. [Serbo-Croat] Reaktor RA nije radio usled zabrane Izvsnog veca Skupstine Srbije od 27. avgusta 1984. U cilju povecanja pouzdanosti rada reaktora a da bi se udovoljilo zakonskim propisima sto je uslov za dobijanje stalne dozvole za rad realizovana su tri velika zahvata na reaktoru RA. Ovi zahvati obuhvatili su izgradnju sistema za hladjenje jezgra reaktora u slucaju nuzde, rekonstukciju postojeceg sistema specijalne ventilacije i rekonstrukciju sistema napajanja elektricnom energijom neophodnih potrosaca reaktora RA. Zapoceti su radovi na modernizaciji intrumentacije reaktora RA, projekat je izradjen u sovjetskoj organizaciji Atomenergoeksport, a trebalo bi da se realizuje do kraja 1989. godine. U cilju povecanja prostora za skladistenje ozracenog nuklearnog goriva i njegovog efikasnijeg koriscenja, izradjen je su projekti za rekonstrukciju postojecih uredjaja za rukovanje gorivom, povecanje smestajnog kapaciteta i preciscavanje vode u bazenima za odlezavanje. Realizaija ovih

  5. Numerical simulation of Rayleigh-Taylor turbulent mixing layers

    International Nuclear Information System (INIS)

    Poujade, O.; Lardjane, N.; Peybernes, M.; Boulet, M.

    2009-01-01

    Accelerations in actual Rayleigh-Taylor instabilities are often variable. This article focuses on a particular class of variable accelerations where g(t) ∝ t n . A reference database is built from high resolution hydrodynamic numerical simulations. The successful comparison with a simple OD analytical model and the statistical 2SFK (2-Structure, 2-Fluid, 2-Turbulence) turbulence model is provided. Moreover, we show the difference between the mechanism at play in the Rayleigh-Taylor turbulent mixing zone and Kolmogorov's in the self similar developed turbulent regime. (authors)

  6. Passive retrieval of Rayleigh waves in disordered elastic media

    International Nuclear Information System (INIS)

    Larose, Eric; Derode, Arnaud; Clorennec, Dominique; Margerin, Ludovic; Campillo, Michel

    2005-01-01

    When averaged over sources or disorder, cross correlation of diffuse fields yields the Green's function between two passive sensors. This technique is applied to elastic ultrasonic waves in an open scattering slab mimicking seismic waves in the Earth's crust. It appears that the Rayleigh wave reconstruction depends on the scattering properties of the elastic slab. Special attention is paid to the specific role of bulk to Rayleigh wave coupling, which may result in unexpected phenomena, such as a persistent time asymmetry in the diffuse regime

  7. Grain size measurements by ultrasonic Rayleigh surface waves

    International Nuclear Information System (INIS)

    Palanichamy, P.; Jayakumar, T.

    1996-01-01

    The use of Rayleigh surface waves to determine average grain size nondestructively in an austenitic stainless steel AISI type 316 stainless is discussed. Two commercial type 4MHz frequency surface wave transducers, one as transmitter and the other as receiver were employed for the measurement of surface wave amplitudes. Relative amplitudes of the Rayleigh surface waves were correlated with the metallographically obtained grain sizes. Results indicate that surface/sub-surface average grain sizes of AISI type 316 austenitic stainless steel can be estimated with a confidence level of more than 80% in the grain size range 30-170 μm. (author)

  8. Study on evaluation methods for Rayleigh wave dispersion characteristic

    Science.gov (United States)

    Shi, L.; Tao, X.; Kayen, R.; Shi, H.; Yan, S.

    2005-01-01

    The evaluation of Rayleigh wave dispersion characteristic is the key step for detecting S-wave velocity structure. By comparing the dispersion curves directly with the spectra analysis of surface waves (SASW) method, rather than comparing the S-wave velocity structure, the validity and precision of microtremor-array method (MAM) can be evaluated more objectively. The results from the China - US joint surface wave investigation in 26 sites in Tangshan, China, show that the MAM has the same precision with SASW method in 83% of the 26 sites. The MAM is valid for Rayleigh wave dispersion characteristic testing and has great application potentiality for site S-wave velocity structure detection.

  9. Rayleigh waves in elastic medium with double porosity

    Directory of Open Access Journals (Sweden)

    Rajneesh KUMAR

    2018-03-01

    Full Text Available The present paper deals with the propagation of Rayleigh waves in isotropic homogeneous elastic half-space with double porosity whose surface is subjected to stress-free boundary conditions. The compact secular equations for elastic solid half-space with voids are deduced as special cases from the present analysis. In order to illustrate the analytical developments, the secular equations have been solved numerically. The computer simulated results for copper materials in respect of Rayleigh wave velocity and attenuation coe¢ cient have been presented graphically.

  10. Rayleigh-Schrödinger series and Birkhoff decomposition

    Science.gov (United States)

    Novelli, Jean-Christophe; Paul, Thierry; Sauzin, David; Thibon, Jean-Yves

    2018-01-01

    We derive new expressions for the Rayleigh-Schrödinger series describing the perturbation of eigenvalues of quantum Hamiltonians. The method, somehow close to the so-called dimensional renormalization in quantum field theory, involves the Birkhoff decomposition of some Laurent series built up out of explicit fully non-resonant terms present in the usual expression of the Rayleigh-Schrödinger series. Our results provide new combinatorial formulae and a new way of deriving perturbation series in quantum mechanics. More generally we prove that such a decomposition provides solutions of general normal form problems in Lie algebras.

  11. Rayleigh-Bénard convection instability in the presence of temperature variation at the lower wall

    Directory of Open Access Journals (Sweden)

    Jovanović Miloš M.

    2012-01-01

    Full Text Available This paper analyzes the two-dimensional viscous fluid flow between two parallel plates, where the lower plate is heated and the upper one is cooled. The temperature difference between the plates is gradually increased during a certain time period, and afterwards it is temporarily constant. The temperature distribution on the lower plate is not constant in x-direction, and there is longitudinal sinusoidal temperature variation imposed on the mean temperature. We investigate the wave number and amplitude influence of this variation on the stability of Rayleigh-Benard convective cells, by direct numerical simulation of 2-D Navier-Stokes and energy equation.

  12. Scalability analysis of large-scale LoRaWAN networks in ns-3

    OpenAIRE

    Abeele, Floris Van den; Haxhibeqiri, Jetmir; Moerman, Ingrid; Hoebeke, Jeroen

    2017-01-01

    As LoRaWAN networks are actively being deployed in the field, it is important to comprehend the limitations of this Low Power Wide Area Network technology. Previous work has raised questions in terms of the scalability and capacity of LoRaWAN networks as the number of end devices grows to hundreds or thousands per gateway. Some works have modeled LoRaWAN networks as pure ALOHA networks, which fails to capture important characteristics such as the capture effect and the effects of interference...

  13. Determination of sup 226 Ra and sup 228 Ra in gypsum

    Energy Technology Data Exchange (ETDEWEB)

    Godoy, J M [Instituto de Radioprotecao e Dosimetria, Rio de Janeiro, RJ (Brazil)

    1989-01-01

    The content of {sup 226}Ra and {sup 228}Ra in different samples of phosphogypsum and three samples of gypsite were determined by gamma spectroscopy. For {sup 226}Ra the 295, 352 and 609 KeV lines and for {sup 228}Ra the 911 and 969 KeV lines were used. The specific activities values ranged from 0.36 to 22.8 pCi/g for {sup 226}Ra and 0.90 to 10.3 pCi/g for {sup 228}Ra. The contribution of a sypsum roof-covering to the {sup 222}Rn concentration in a room was estimated, based on the highest value reported. (author).

  14. 224Ra and 226Ra experimentally induced dental changes in rats

    International Nuclear Information System (INIS)

    Reichart, P.A.; Althoff, J.; Eckhardt, W.; Rippel, W.

    1979-01-01

    Sprague-Dawley rats received intragastrically a single dose of 226 Ra or 224 Ra once weekly for 21 weeks. During this period the animals of both groups were thus exposed to comparable doses. After 12 weeks, a shortening of the maxillary incisors was observed, and this progressed during the course of the 55-week experiment. Radiologically, a loss of pulpal transparency and an apical irregular opacity in the maxillary incisors were demonstrable. Histologically, dysplastic changes of the maxillary incisors and multiple resorptions at the cemento-enamel junction of the molars were seen. The observed alterations were more pronounced in the 226 Ra group than in the 224 Ra treated group. The experimentally induced resorptions were comparable to those observed in patients who had incorporated 224 Ra or 226 Ra. Clinical, radiological, histological, γspecrometrical, and autoradiographical findings, as well as dose-estimations, are described. (author)

  15. Distribution and flux of 226Ra and 228Ra in the Amazon River estuary

    International Nuclear Information System (INIS)

    Key, R.M.; Sarmiento, J.L.; Stallard, R.F.; Moore, W.S.

    1985-01-01

    Measurements of 226 Ra and 228 Ra in the Amazon River estuary show that desorption from riverborne suspended particulate matter in the estuary increases the riverine flux of both isotopes to the ocean by a factor of approximately 5 over the flux attributable to radium dissolved in the river water alone. The total Amazon flux supplies approximately 0.20% of the 226 Ra and approximately 2.6% of the 228 Ra standing crops in the near-surface Atlantic (0-200 m). Diffusive flux from estuarine and shelf sediments and desorption from resuspended sediments in the region of the estuary approximately double the estuarine 226 Ra concentration and quadruple the estuarine 228 Ra concentration above that caused by the dissolved and desorbed river components alone

  16. Nd:YAG Laser-Based Dual-Line Detection Rayleigh Scattering and Current Efforts on UV, Filtered Rayleigh Scattering

    Science.gov (United States)

    Otugen, M. Volkan; Popovic, Svetozar

    1996-01-01

    Ongoing research in Rayleigh scattering diagnostics for variable density low speed flow applications and for supersonic flow measurements are described. During the past several years, the focus has been on the development and use of a Nd:YAG-based Rayleigh scattering system with improved signal-to-noise characteristics and with applicability to complex, confined flows. This activity serves other research projects in the Aerodynamics Laboratory which require the non-contact, accurate, time-frozen measurement of gas density, pressure, and temperature (each separately), in a fairly wide dynamic range of each parameter. Recently, with the acquisition of a new seed-injected Nd:YAG laser, effort also has been directed to the development of a high-speed velocity probe based on a spectrally resolved Rayleigh scattering technique.

  17. RA Research reactor, Annual report 1988; Istrazivacki nuklearni reaktor RA - Izvestaj za 1988. godinu

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1988-12-15

    Annual report concerning the project 'RA research nuclear reactor' for 1989, financed by the Serbian ministry of science is divided into two parts. First part is concerned with RA reactor operation and maintenance, which is the task of the Division for reactor engineering of the Institute for multidisciplinary studies and RA reactor engineering. Second part deals with radiation protection activities at the RA reactor which is the responsibility of the Institute for radiation protection. Scientific council of the Institute for multidisciplinary studies and RA reactor engineering has stated that this report describes adequately the activity and tasks fulfilled at the RA reactor in 1989. The scope and the quality of the work done were considered successful both concerning the maintenance and reconstruction, as well as radiation protection activities. [Serbo-Croat] Godisnji izvestaj po projektu 'Istrazivacki nuklearni reaktor RA' za 1989. godinu, koji finansira republicka zajednica za nauku SR Srbije po ugovoru br. 3705/1 sastoji se iz dva dela. Prvi deo obuhvata pogon i odrzavanje nuklearnog reaktora RA, sto predstavlja obavezu Odeljenja za reaktorski inzenjering u sastavu OOUR Instituta za multidisciplinarna istrazivanja i inzenjering RA. Drugi deo obuhvata poslove zastite od zracenja na reaktoru RA, sto predstavlja obavezu OOUR Instituta za zastitu od zracenja 'Zastita'. Naucno vece Instituta za multidisciplinarna istrazivanja i inzenjering RA ocenilo je da sadrzina ovog izvestaja odgovara izvrsenim poslovima na reaktoru RA u 1989. godini. Pozitivno se ocenjuje obim i kvalitet izvrsenih radova kako u pogledu odrzavanja i rekonstrukcije reaktora, tako i u pogledu poslova zastite od zracenja izvrsenih kod njega.

  18. Research nuclear reactor RA - Annual Report 1989; Istrazivacki nuklearni reaktor RA - Izvestaj za 1989. godinu

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1989-12-15

    Annual report concerning the project 'RA research nuclear reactor' for 1989, financed by the Serbian ministry of science is divided into two parts. First part is concerned with RA reactor operation and maintenance, which is the task of the Division for reactor engineering of the Institute for multidisciplinary studies and RA reactor engineering. Second part deals with radiation protection activities at the RA reactor which is the responsibility of the Institute for radiation protection. Scientific council of the Institute for multidisciplinary studies and RA reactor engineering has stated that this report describes adequately the activity and tasks fulfilled at the RA reactor in 1989. The scope and the quality of the work done were considered successful both concerning the maintenance and reconstruction, as well as radiation protection activities. [Serbo-Croat] Godisnji izvestaj po projektu 'Istrazivacki nuklearni reaktor RA' za 1989. godinu, koji finansira republicka zajednica za nauku SR Srbije po ugovoru br. 3705/1 sastoji se iz dva dela. Prvi deo obuhvata pogon i odrzavanje nuklearnog reaktora RA, sto predstavlja obavezu Odeljenja za reaktorski inzenjering u sastavu OOUR Instituta za multidisciplinarna istrazivanja i inzenjering RA. Drugi deo obuhvata poslove zastite od zracenja na reaktoru RA, sto predstavlja obavezu OOUR Instituta za zastitu od zracenja 'Zastita'. Naucno vece Instituta za multidisciplinarna istrazivanja i inzenjering RA ocenilo je da sadrzina ovog izvestaja odgovara izvrsenim poslovima na reaktoru RA u 1989. godini. Pozitivno se ocenjuje obim i kvalitet izvrsenih radova kako u pogledu odrzavanja i rekonstrukcije reaktora, tako i u pogledu poslova zastite od zracenja izvrsenih kod njega.

  19. Radiochemical determination and separation or total radium, 226Ra and 224Ra

    International Nuclear Information System (INIS)

    Suarez, J. A.; Gonzalez, J. A.; Pablo, M. A. de

    1987-01-01

    Radiochemical purification and separation of radium has been carried out and the determination of total radium solubilized in aqueous samples has been studied assuming that all the alpha emitters of the sample have their origin in the 226Ra and elements of its desintegration chain. Also, the activities of 22Ra and 226 Ra have been evaluated separately doing a measurement after the chemical separation of the radium and another one 10 days after. (Author) 9 refs

  20. Ba(Ra)SO4 species flotation for decontamination of Ra(II) residual solution

    International Nuclear Information System (INIS)

    Stoica, Ligia; Catuneanu, Rodica; Filip, Gheorghe

    1993-01-01

    The paper presents the results of the research performed on Ra(II) separation from complex composition solutions in a HCO 3 - /CO 3 2- buffer system by Ba(Ra)SO 4 precipitation followed by flotation. The collector selection was done by electrokinetic potential determinations. The optimum concentrations of precipitation-flocculation reagents were established on the basis of the experimental data obtained for synthetic solutions having the same Ra(II) activity, namely 20 pCi/l. (authors)

  1. Depolarization Rayleigh scattering as a means of molecular concentration determination in plasmas

    NARCIS (Netherlands)

    Meulenbroeks, R.F.G.; Schram, D.C.; Jaegers, L.J.M.; Sanden, van de M.C.M.

    1992-01-01

    The difference in polarization for Rayleigh scattered radiation on spherically and nonspherically symmetric scattering objects has been used to obtain molecular species concentrations in plasmas of simple composition. Using a Rayleigh scattering diagnostic, the depolarized component of the scattered

  2. Determination of 226Ra and 224Ra in drinking waters by liquid scintillation counting

    International Nuclear Information System (INIS)

    Manjon, G.; Vioque, I.; Moreno, H.; Garcia-Tenorio, R.; Garcia-Leon, M.

    1997-01-01

    A method for the determination of Ra-isotopes in water samples has been developed. Ra is coprecipitated with Ba as sulphate. The precipitate is then dissolved with EDTA and counted with a liquid scintillation system after mixing with a scintillation cocktail. The study of the temporal evolution of the separated activity gives the isotopic composition of the sample, i.e. the 224 Ra and 226 Ra contribution to the total activity. The method has been applied to some Spanish drinking waters. (author)

  3. Experimental investigation of quantum effects in time-resolved resonance Rayleigh scattering from quantum well excitons

    DEFF Research Database (Denmark)

    Birkedal, Dan; Shah, Jagdeep; Shchegrov, Andrei V.

    2000-01-01

    Resonant Rayleigh scattering from quantum well excitons is investigated using ultrafast spectral interferometry. We isolate the coherent Rayleigh scattering from incoherent luminescence in a single speckle. Averaging the resonant Rayleigh intensity over several speckles allows us to identify...... features in support of quantum corrections to the classical description of the underlying scattering process....

  4. Instantaneous Rayleigh scattering from excitons localized in monolayer islands

    DEFF Research Database (Denmark)

    Langbein, Wolfgang; Leosson, Kristjan; Jensen, Jacob Riis

    2000-01-01

    We show that the initial dynamics of Rayleigh scattering from excitons in quantum wells can be either instantaneous or delayed, depending on the exciton ensemble studied. For excitation of the entire exciton resonance, a finite rise time given by the inverse inhomogeneous broadening: of the exciton...

  5. Rayleigh-Taylor convective overturn in stellar collapse

    International Nuclear Information System (INIS)

    Bruenn, S.W.; Buchler, J.R.; Livio, M.

    1979-01-01

    Rayleigh--Taylor convective overturn in collapsing stellar cores is modeled with a one-dimensional parametrization. The results of a numerical hydrodynamic study are very encouraging and indicate that such an overturn could well be a dominant feature in the supernova explosion mechanism

  6. Measurement of the stimulated thermal Rayleigh scattering instability

    International Nuclear Information System (INIS)

    Karr, T.J.; Rushford, M.C.; Murray, J.R.; Morris, J.R.

    1989-04-01

    Growth of perturbations due to stimulated thermal Rayleigh scattering was observed on a laser beam propagating in a 1 meter cell of CC14. Initial sinusoidal irradiance perturbations were seeded onto the laser leam, and their amplification in the cell was recorded by a near field camera. The perturbation growth rate is in agreement with analytical predictions of linearized propagation theory

  7. The prediction and discovery of Rayleigh line fine structure

    International Nuclear Information System (INIS)

    Fabelinskii, Immanuil L

    2000-01-01

    The history of the theoretical prediction and experimental discovery of the Rayleigh line fine structure (which belongs to one of the most important phenomena in optics and physics of condensed matter) is discussed along with the history of first publications concerning this topic. (from the history of physics)

  8. Using the self-learning intellectual models for predicting the development of the Rayleigh-Taylor turbulent mixing

    International Nuclear Information System (INIS)

    Nuzhnyj, A.S.; Rozanov, V.B.; Stepanov, R.V.; Shumskij, S.A.

    2005-01-01

    Stability of target compression in the laser thermonuclear synthesis is discussed. The process is determined by developing the Rayleigh-Taylor instability (RNI). A program unit for description of the RNI evolution by its initial distributions is developed. The results of statistical analysis of the RT mixing calculations are given. The analysis is carried out by means of learning base system and is substantiated on the generalization of great number of data, fulfilled by means of the neural network methods [ru

  9. Timing is everything: Reiterative Wnt, BMP and RA signaling regulate developmental competence during endoderm organogenesis.

    Science.gov (United States)

    Rankin, Scott A; McCracken, Kyle W; Luedeke, David M; Han, Lu; Wells, James M; Shannon, John M; Zorn, Aaron M

    2018-02-01

    A small number of signaling pathways are used repeatedly during organogenesis, and they can have drastically different effects on the same population of cells depending on the embryonic stage. How cellular competence changes over developmental time is not well understood. Here we used Xenopus, mouse, and human pluripotent stem cells to investigate how the temporal sequence of Wnt, BMP, and retinoic acid (RA) signals regulates endoderm developmental competence and organ induction, focusing on respiratory fate. While Nkx2-1+ lung fate is not induced until late somitogenesis stages, here we show that lung competence is restricted by the gastrula stage as a result of Wnt and BMP-dependent anterior-posterior (A-P) patterning. These early Wnt and BMP signals make posterior endoderm refractory to subsequent RA/Wnt/BMP-dependent lung induction. We further mapped how RA modulates the response to Wnt and BMP in a temporal specific manner. In the gastrula RA promotes posterior identity, however in early somite stages of development RA regulates respiratory versus pharyngeal potential in anterior endoderm and midgut versus hindgut potential in posterior endoderm. Together our data suggest a dynamic and conserved response of vertebrate endoderm during organogenesis, wherein early Wnt/BMP/RA impacts how cells respond to later Wnt/BMP/RA signals, illustrating how reiterative combinatorial signaling can regulate both developmental competence and subsequent fate specification. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Nuclear Reactor RA Safety Report, Vol. 4, Reactor

    International Nuclear Information System (INIS)

    1986-11-01

    RA research reactor is thermal heavy water moderated and cooled reactor. Metal uranium 2% enriched fuel elements were used at the beginning of its operation. Since 1976, 80% enriched uranium oxide dispersed in aluminium fuel elements were gradually introduced into the core and are the only ones presently used. Reactor core is cylindrical, having diameter 40 cm and 123 cm high. Reaktor core is made up of 82 fuel elements in aluminium channels, lattice is square, lattice pitch 13 cm. Reactor vessel is cylindrical made of 8 mm thick aluminium, inside diameter 140 cm and 5.5 m high surrounded with neutron reflector and biological shield. There is no containment, the reactor building is playing the shielding role. Three pumps enable circulation of heavy water in the primary cooling circuit. Degradation of heavy water is prevented by helium cover gas. Control rods with cadmium regulate the reactor operation. There are eleven absorption rods, seven are used for long term reactivity compensation, two for automatic power regulation and two for safety shutdown. Total anti reactivity of the rods amounts to 24%. RA reactor is equipped with a number of experimental channels, 45 vertical (9 in the core), 34 in the graphite reflector and two in the water biological shield; and six horizontal channels regularly distributed in the core. This volume include detailed description of systems and components of the RA reactor, reactor core parameters, thermal hydraulics of the core, fuel elements, fuel elements handling equipment, fuel management, and experimental devices [sr

  11. Assessment of 226Ra, 228Ra and 40K contents in the Egyptian bottled natural water

    International Nuclear Information System (INIS)

    El-Afifi, E.M.; Hilal, M.A.; Khalifa, S.M.; Aly, H.F.

    2004-01-01

    The activity concentrations of 2 26Ra, 2 28Ra and 4 0 and k in different brands of the bottled egyptian natural water of different origins obtained from four regions, have been analyzed nondestructively by gamma- ray spectrometry. The study covers nine brands of natural water commonly used mainly for drinking in egypt. The results showed, concentrations up to 184, 156 and 1700 mBq I - 1 for 2 26Ra, 2 28Ra and 4 0K, respectively, in one brand of the natural water from water from Siwa oasis. Whereas, lower activity concentrations of 2 26Ra and 2 28Ra were found in one brand of these natural waters from El sadat region. The activity concentration of 4 0K was found to be in the background range in the brands from El sadat, kafr El arbein and beilbeis regions. The committed effective doses reached 1.9 x 10 - 2 m Sy Y - 1 for ingestion of 2 26Ra and 2 28Ra for one liter per day, respectively, which are lower than the standard permissible limit by the WHO and IAEA. However, it is recommended to moderate drinking of bottled natural water to avoid the accumulation effect of radioactive nuclides especially radium

  12. Techniques for precise mapping of 226Ra and 228Ra in the ocean

    International Nuclear Information System (INIS)

    Moore, W.S.; Key, R.M.; Sarmiento, J.L.

    1985-01-01

    Improvements in the analyses of 226 Ra and 228 Ra in seawater made possible by better extraction and processing techniques reduce significantly the errors associated with these measurements. These improvements and the extensive sampling for Ra isotopes conducted on the TTO North Atlantic Study should enable us to use the distribution of 228 Ra to study mixing processes on a 3-15 year time scale in both the upper and deep North Atlantic. The 228 Ra profiles already analyzed show a closer resemblance to GEOSECS tritium data than to TTO tritium data in the upper ocean. This is because the transient tracer tritium was responding on a 10-year time scale during GEOSECS and a 20-year time scale during TTO. The steady state tracer 228 Ra should always respond on a time scale of 8 years. Thus the 228 Ra data obtained on TTO should provide a means to extend the features of the GEOSECS tritium field to the regions of the TTO study. The 226 Ra data are of high enough quality to identify features associated with different water masses. Changes in the positions of the deep-water masses since the GEOSECS cruise are revealed by the 226 Radata

  13. Use of nuclear recoil for separating 228Ra, 224Ra, and 233Pa from colloidal thorium

    International Nuclear Information System (INIS)

    Beydon, J.; Gratot, I.

    1968-01-01

    By using α-recoil it is possible to separate by dialysis the α disintegration products (224 Ra; 228 Ra) of thorium from colloidal thorium hydroxide.The use of n, γ recoil allows the separation of 233 Pa produced by the neutron irradiation of thorium, on condition that the colloidal thorium hydroxide is irradiated in the presence of a dispersing. (author) [fr

  14. Rayleigh-Benard convection in a Hele-Shaw cell - a numerical study

    International Nuclear Information System (INIS)

    Guenther, C.; Mueller, U.

    1987-05-01

    Free convection in narrow vertical gaps heated from below gives rise to several different flow patterns as has been demonstrated by previous experimental investigations. A numerical study is presented aimed at simulating the observed flow phenomena in Hele-Shaw cells of small lateral extend. The numerical study is based on the assumption that the flow is essentially two-dimensional. This allows an approach using a one-term Galerkin approximation with respect to the direction perpendicular to the gap and a finite difference scheme with regard to the coordinates in the plane of the gap. The calculations result in realistic values of the critical Rayleigh numbers for the onset of steady and oscillatory convection. Most of the observed unsteady flow patterns can be simulated numerically. It is shown that five different stable flow patterns can occur at one particular Rayleigh number. The different stable flow patterns are coupled by a variety of complex transitions. Moreover the calculations show that a realistic description of the observed flow phenomena can not be obtained by a simplified model using the Darcy law in the momentum equation and implying slip flow at the small confining boundaries. (orig.) [de

  15. Ablative stabilization of the Rayleigh-Taylor instability in regimes relevant to inertial confinement fusion

    International Nuclear Information System (INIS)

    Kilkenny, J.D.

    1994-01-01

    As shown elsewhere an ablatively imploded shell is hydrodynamically unstable, the dominant instability being the well known Rayleigh-Taylor instability with growth rate γ = √Akg where k = 2π/λ is the wave number, g is the acceleration and A the Attwood number (ρ hi - ρ lo )/(ρ hi + ρ lo ) where ρ hi is the density of the heavier fluid and ρ lo is the density of the lighter fluid. A theoretical understanding of ablative stabilization has gradually evolved, confirmed over the last five years by experiments. The linear growth is very well understood with excellent agreement between experiment and simulation for planar geometry with wavelengths in the region of 30--100μm. There is an accurate, albeit phenomenological dispersion relation. The non-linear growth has been measured and agrees with calculations. In this lecture, the authors go into the fundamentals of the Rayleigh-Taylor instability and the experimental measurements that show it is stabilized sufficiently by ablation in regimes relevant to ICF

  16. Thermal Rayleigh-Marangoni convection in a three-layer liquid-metal-battery model

    Science.gov (United States)

    Köllner, Thomas; Boeck, Thomas; Schumacher, Jörg

    2017-05-01

    The combined effects of buoyancy-driven Rayleigh-Bénard convection (RC) and surface tension-driven Marangoni convection (MC) are studied in a triple-layer configuration which serves as a simplified model for a liquid metal battery (LMB). The three-layer model consists of a liquid metal alloy cathode, a molten salt separation layer, and a liquid metal anode at the top. Convection is triggered by the temperature gradient between the hot electrolyte and the colder electrodes, which is a consequence of the release of resistive heat during operation. We present a linear stability analysis of the state of pure thermal conduction in combination with three-dimensional direct numerical simulations of the nonlinear turbulent evolution on the basis of a pseudospectral method. Five different modes of convection are identified in the configuration, which are partly coupled to each other: RC in the upper electrode, RC with internal heating in the molten salt layer, and MC at both interfaces between molten salt and electrode as well as anticonvection in the middle layer and lower electrode. The linear stability analysis confirms that the additional Marangoni effect in the present setup increases the growth rates of the linearly unstable modes, i.e., Marangoni and Rayleigh-Bénard instability act together in the molten salt layer. The critical Grashof and Marangoni numbers decrease with increasing middle layer thickness. The calculated thresholds for the onset of convection are found for realistic current densities of laboratory-sized LMBs. The global turbulent heat transfer follows scaling predictions for internally heated RC. The global turbulent momentum transfer is comparable with turbulent convection in the classical Rayleigh-Bénard case. In summary, our studies show that incorporating Marangoni effects generates smaller flow structures, alters the velocity magnitudes, and enhances the turbulent heat transfer across the triple-layer configuration.

  17. Does a family history of RA influence the clinical presentation and treatment response in RA?

    Science.gov (United States)

    Frisell, Thomas; Saevarsdottir, Saedis; Askling, Johan

    2016-06-01

    To assess whether family history of rheumatoid arthritis (RA), among the strongest risk factors for developing RA, also carries information on the clinical presentation and treatment response. The prospective Swedish Rheumatology register was linked to family history of RA, defined as diagnosed RA in any first-degree relative, ascertained through the Swedish Multi-Generation and Patient registers. Clinical presentation was examined among patients with early RA 2000-2011 (symptom onset clinical characteristics, drug survival, European League Against Rheumatism (EULAR) response and change in disease activity at 3 and 6 months was estimated using linear and generalised logistic regression models. Correlation in relatives' response measures was also assessed. Patients with early RA with family history of RA were more often rheumatoid factor positive, but with no other clinically meaningful differences in their clinical presentation. Family history of RA did not predict response to MTX or TNFi, with the possible exception of no versus good EULAR response to TNFi at 6 months (OR=1.4, 95% CI 1.1 to 1.7). Having a relative who discontinued TNFi within a year increased the odds of doing the same (OR=3.7, 95% CI 1.8 to 7.5), although we found no significant familial correlations in change in disease activity measures. Family history of RA did not modify the clinical presentation of RA or predict response to standard treatment with MTX or TNFi. Treatment response, particularly drug survival, may itself be familial. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  18. A new determination method of 226Ra, 224Ra, and 228Th in water

    International Nuclear Information System (INIS)

    Horiuchi, Kimiko; Murakami, Yukio.

    1981-01-01

    A new method for the determination of 226 Ra, 224 Ra and 228 Th in water samples is described. It consists of extraction of 222 Rn and 220 Rn into a scintillator-toluene solution in equilibrium with 226 Ra and 224 Ra and the application of integral counting techniques with a liquid scintillation counter. One liter water sample, weakly acidified with hydrochloric acid, is transferred to a glass bottle, and vigorously bubbled with a stream of nitrogen to expel any radon or thoron in the water sample. Twenty five ml of the scintillator-toluene solution is added to the bottle (time is recorded). The bottle is stoppered with a Teflon stopper and kept at an upside-down position for a given period of time (usually 4 -- 16 days) to allow radon and thoron in partial equilibrium with their parent nuclides. Then, the sample system is vigorously shaken for 2 m and the organic layer is gently transferred to a counting vial through a specially devised transferring tube which is connected to the bottle. The initial counting time is set at 4 h after the separation of organic layer. The measurements are repeated 3 times each immediately and after 106 h from the initial counting time. From these results, the integral counting rates of radon and thoron at the initial counting time are easily obtained. The activities of 226 Ra, 224 Ra and 228 Th in the water sample are calculated from these integral counting rates by the proposed formulas. Some data on the 226 Ra and 224 Ra contents of mineral springs are presented. The lowest detection limits for 226 Ra and 224 Ra were 1.10 x 10 -12 and 1.47 x 10 -9 Ci, respectively. The present method is rapid, easy and accurate and eliminates a time-consuming sealing of the sample in Curie bottle and tedious procedure to transfer the sample gas through a vacuum system to the detector. (author)

  19. Research nuclear reactor RA, Annual Report 2001

    International Nuclear Information System (INIS)

    Sotic, O.

    2002-01-01

    During 2001, activities at the RA research nuclear reactor in were performed according to the Contract about financing of the RA reactor for the period January-December 2001, signed by the Ministry of Science, technology and development of the Republic of Serbia. RA reactor was not operated since shutdown in August 1984. Although, the most of the planned reconstruction activities were finished until 1991, the most important, which was concerned with exchange of the reactor instrumentation, financed by the IAEA, was interrupted due to international sanctions imposed on the country. Since 1992, all the renewal and reconstruction activities were ceased. Continuous aging and degradation of the equipment and facilities demand decision making about the future status of the Ra reactor. Until this decision is made it is an obligation to maintain control and maintenance of ventilation system, power supply, internal transportation system, spent fuel storage, hot cells, electronic fuel surveillance system, and part of the stationary dosimetry system. In 2001, apart from the mentioned activities, actions were undertaken related to maintenance of the reactor building and installations. The most important tasks fulfilled were: protection of the roof of the ventilation system building, purchase and installing the fire protection system and twelve new battery cells in the reactor building. There were no actions concerned with improvement of the conditions for intermediate spent fuel storage. With the support of IAEA, actions were initiated for possible transport of the spent fuel tu Russia. At the end of 2001, preparations were started for possible future decommissioning of the RA reactor. After, renewal of the membership of our country in the IAEA, the Government of Yugoslavia has declared its attitude about the intention of RA reactor decommissioning at the General Conference in September 2001 [sr

  20. Measurements of neutron flux in the RA reactor

    International Nuclear Information System (INIS)

    Raisic, N.

    1961-12-01

    This report includes the following separate parts: Thermal neutron flux in the experimental channels od RA reactor; Epithermal neutron flux in the experimental channels od RA reactor; Fast neutron flux in the experimental channels od RA reactor; Thermal neutron flux in the thermal column and biological experimental channel; Neutronic measurements in the RA reactor cell; Temperature reactivity coefficient of the RA reactor; design of the device for measuring the activity of wire [sr

  1. On Multiple Users Scheduling Using Superposition Coding over Rayleigh Fading Channels

    KAUST Repository

    Zafar, Ammar

    2013-02-20

    In this letter, numerical results are provided to analyze the gains of multiple users scheduling via superposition coding with successive interference cancellation in comparison with the conventional single user scheduling in Rayleigh blockfading broadcast channels. The information-theoretic optimal power, rate and decoding order allocation for the superposition coding scheme are considered and the corresponding histogram for the optimal number of scheduled users is evaluated. Results show that at optimality there is a high probability that only two or three users are scheduled per channel transmission block. Numerical results for the gains of multiple users scheduling in terms of the long term throughput under hard and proportional fairness as well as for fixed merit weights for the users are also provided. These results show that the performance gain of multiple users scheduling over single user scheduling increases when the total number of users in the network increases, and it can exceed 10% for high number of users

  2. Summary of dosimetry, pathology, and dose response for bone sarcomas in beagles injected with 226Ra

    International Nuclear Information System (INIS)

    Wrenn, M.E.; Taylor, G.N.; Stevens, W.

    1985-01-01

    One hundred and sixty dogs given single intravenous injections of 226 Ra citrate at age 17 +/- 2 months (116) or a non-radioactive solution (44 controls) were part of a 30 year long experiment to determine the relative radiotoxicity of injected 226 Ra and 239 Pu. The authors report a preliminary summary of the results of the 226 Ra study. Skeletal development of the beagles used in this study is analogous to a young adult human, simulating that of a young adult radium dial painter or occupationally exposed person. Injected dosage of 226 Ra, average skeletal dose, and number of dogs and dogs developing bone sarcomas in each group are presented. The lowest nominal injected activity was 0.007 μCi/kg. Each of the 8 dosage levels contained about 12 dogs, except for 23 dogs at 0.06 μCi/kg and 25 dogs at 0.02 μCi/kg

  3. RA-0 reactor. New neutronic calculations

    International Nuclear Information System (INIS)

    Rumis, D.; Leszczynski, F.

    1990-01-01

    An updating of the neutronic calculations performed at the RA-0 reactor, located at the Natural, Physical and Exact Sciences Faculty of Cordoba National University, are herein described. The techniques used for the calculation of a reactor like the RA-0 allows prediction in detail of the flux behaviour in the core's interior and in the reflector, which will be helpful for experiments design. In particular, the use of WIMSD4 code to make calculations on the reactor implies a novelty in the possible applications of this code to solve the problems that arise in practice. (Author) [es

  4. ICMPv6 RA Flooding Vulnerability Research

    Directory of Open Access Journals (Sweden)

    Linas Jočys

    2016-06-01

    Full Text Available ICMPv6 is the newest version of internet control message protocol, whose main purpose is to send error message indicating packet processing failure. It is know that ICMPv6 is technologically vulnerable. One of those vulnerabilities is the ICMPv6 RA flooding vulnerability, which can lead to systems in Local Area Network slow down or full stop. This paper will discuss Windows (XP, 7, 8.1 and Linux Ubuntu 14 operating systems resistance to RA flooding attack research and countermeasures to minimize this vulnerability.

  5. Determination of 226 Ra and 228 Ra in mineral spring waters of the Aguas da Prata region

    International Nuclear Information System (INIS)

    Oliveira, J. de.

    1993-01-01

    Concentration levels of 226 Ra and 228 Ra have been analysed in most of the mineral spring waters available in the Aguas da Prata region. The 226 Ra and 228 Ra were determined by coprecipitation with barium sulphate. The 226 Ra was determined by gross alpha counting of the Ba(Ra)SO 4 precipitate. The determination of 228 Ra was done by measuring the gross beta activity of the same precipitate. Both measurements were carried out in a low background gas flow proportional counter. Dose calculations were performed in order to evaluate the relative importance of such radionuclides to the radiation exposure due to the ingestion of these waters. Based upon measured concentrations, committed effective doses up to 5.5 x 10 -1 mSv/y and 1.0 x 10 -2 mSv/y were observed for 226 Ra and 228 Ra, respectively. These results show that 226 Ra is the main contributor to radiation exposure. (author)

  6. On the ""early-time"" evolution of variables relevant to turbulence models for Rayleigh-Taylor instability

    Energy Technology Data Exchange (ETDEWEB)

    Rollin, Bertrand [Los Alamos National Laboratory; Andrews, Malcolm J [Los Alamos National Laboratory

    2010-01-01

    We present our progress toward setting initial conditions in variable density turbulence models. In particular, we concentrate our efforts on the BHR turbulence model for turbulent Rayleigh-Taylor instability. Our approach is to predict profiles of relevant parameters before the fully turbulent regime and use them as initial conditions for the turbulence model. We use an idealized model of the mixing between two interpenetrating fluids to define the initial profiles for the turbulence model parameters. Velocities and volume fractions used in the idealized mixing model are obtained respectively from a set of ordinary differential equations modeling the growth of the Rayleigh-Taylor instability and from an idealization of the density profile in the mixing layer. A comparison between predicted initial profiles for the turbulence model parameters and initial profiles of the parameters obtained from low Atwood number three dimensional simulations show reasonable agreement.

  7. On the ""early-time"" evolution of variables relevant to turbulence models for the Rayleigh-Taylor instability

    Energy Technology Data Exchange (ETDEWEB)

    Rollin, Bertrand [Los Alamos National Laboratory; Andrews, Malcolm J [Los Alamos National Laboratory

    2010-01-01

    We present our progress toward setting initial conditions in variable density turbulence models. In particular, we concentrate our efforts on the BHR turbulence model for turbulent Rayleigh-Taylor instability. Our approach is to predict profiles of relevant variables before fully turbulent regime and use them as initial conditions for the turbulence model. We use an idealized model of mixing between two interpenetrating fluids to define the initial profiles for the turbulence model variables. Velocities and volume fractions used in the idealized mixing model are obtained respectively from a set of ordinary differential equations modeling the growth of the Rayleigh-Taylor instability and from an idealization of the density profile in the mixing layer. A comparison between predicted profiles for the turbulence model variables and profiles of the variables obtained from low Atwood number three dimensional simulations show reasonable agreement.

  8. Power Laws and Similarity of Rayleigh-Taylor and Richtmyer-Meshkov Mixing Fronts at All Density Ratios

    International Nuclear Information System (INIS)

    Alon, U.; Hecht, J.; Ofer, D.; Shvarts, D.

    1995-01-01

    The nonlinear evolution of large structure in Rayleigh-Taylor and Richtmyer-Meshkov bubble and spike fronts is studied numerically and explained theoretically on the basis of single-mode and two-bubble interaction physics at Atwood numbers (A). Multimode Rayleigh-Taylor bubble (spike) fronts are found as h B =α B Agt 2 [h s =α s (A)gt 2 ] with α B =0.05, while Richtmyer-Meshkov bubble (spike) fronts are found as h B =a B t θ B (h s =a s t θ s (A) ) with θ B =0.4 at all A's. The dependence of these scaling laws and parameters on A and on initial conditions is explained

  9. RA Research reactor, Annual report 1969

    International Nuclear Information System (INIS)

    Milosevic, D. et al.

    1969-12-01

    During 1969, the RA Reactor was operated at nominal power of 6.5 MW for 200 days, and 15 days at lower power levels. Total production mounted to 31131 MWh which is 3.77% higher than planned. Reactor was used for irradiation and experiments according to the demand of 463 users from the Institute and 63 external users. This report contains detailed data about reactor power and experiments performed in 1969. It is concluded that the reactor operated successfully according to the plan. If there had been no problems with power supply during last three months and Danube low water level in September and October the past year would have been the most successful up to now. The number od scram shutdowns was not higher than during past two years in spite of the difficulties in the last quarter. There were three incidents which caused higher personnel exposure during operation. One, was the destruction of the canner with silver (because the time spent in the core was too long) which caused the surface contamination of the platform, the background radiation was 10 to 100 times higher than regular. The other two cases were caused by failure of the device for handling the fuel slugs in the fuel channels during refuelling. Reactor refuelling was done four times during 1969, and 499 fresh fuel slugs were used. Refuelling applied the approach of 'mixing' the fresh fuel slugs with the 'old' fuel slugs in the fuel channel. Decontamination of surfaces was on the same level as previously in spite of the problems with silver. Since two staff members have left, the present number od employees is now the minimum needed for reactor operation and maintenance. It is stated that the operation of components and equipment is on sufficiently high level after ten years of reactor operation. The action plan for 1970 is made according to the same principles as in previous four years but the planned production is decreased to 25000 MWh, because control of important components is needed after ten

  10. Fine structures in 14C emission of 223Ra and 224Ra

    International Nuclear Information System (INIS)

    Hourani, E.; Rosier, L.; Berrier-Ronsin, G.; Elayi, A.; Mueller, A.C.; Rappenecker, G.; Rotbard, G.; Renou, G.; Liebe, A.; Stab, L.

    1991-01-01

    The measurement of the energy spectrum of 14 C nuclei emitted in the spontaneous radioactivity from 223 Ra and 224 Ra has been carried out, using thin and intense sources (480 MBq for 223 Ra and 3550 MBq for 224 Ra). The sources were obtained by implanting mass-separated beams from ISOLDE (CERN) into Al and vitreous C catchers. The measurement was performed with the supraconducting solenoidal spectrometer SOLENO installed at Orsay. The discovery, of a fine structure in the energy spectrum of 14 C emission from 223 Ra, which is analogous to the one known for α emission, is confirmed. Only 13% of the branching ratio in 14 C decay leads to the ground state of the residual nucleus, while 8l% to the first excited state. For 14 C emission of 224 Ra, a lower limit of 2 for the hindrance factor has been measured for the transition to the first excited state in the residual nucleus. Also, a precise identification in Z with a E·ΔE telescope has been performed for the radiation from the 223 Ra source. (author) 22 refs., 11 figs., 1 tab

  11. Therapy palliative with 223Ra without special radiation protection measures?

    International Nuclear Information System (INIS)

    Just, Guenther; Petzold, Juergen

    2015-01-01

    For nearly 2 years now as a therapy of the castration resistant prostata carcinoma a nuclide therapy with 223 Ra-Dichloride (trade-mark Xofigo) is applied. Xofigo is applied by a medical specialist for nuclear medicine altogether 6 times in a monthly distance. The activity used in each case is according to the body weight (50 kBq/kg BW). This therapy is licensed by the supervisory authorities of the German federal countries as an ambulant therapy. Special radiation protection measures are only required when exceeding a given number of 17 patients per year as incorparation measurements.

  12. RA research reactor - properties and experimental capabilities

    International Nuclear Information System (INIS)

    Milosevic, M.; Martinc, R.

    1978-01-01

    The brief survey of the Reactor RA exploitation experience, as well as the reactor equipment state, after 18 years of operation is presented. The results of efforts spent on reactor characteristics improvement in order to ensure safe and reliable reactor operation for next 15-20 years, are described [sr

  13. Waste Management During RA Reactor Decommissioning

    International Nuclear Information System (INIS)

    Markovic, M.; Avramovic, I.

    2008-01-01

    The objective of radioactive waste management during the RA reactor decommissioning is to deal with radioactive waste in a manner that protects human health and the environment now and in the future. The estimation of waste quantities to be expected during decommissioning is a very important step in the initial planning. (author)

  14. Chôra : Creation and Pathology

    DEFF Research Database (Denmark)

    Isar, Nicoletta

    2009-01-01

    Plato's dialogue the Timaeus describes not only the making of the cosmos (order), but also the condition of what is not order, neither for the human body nor for the universe. What is disorder in cosmogonic terms it is disease for the human body. Timaeus applies to the concept chôra in discussing...

  15. Regulations and instructions for RA reactor operation

    International Nuclear Information System (INIS)

    1989-01-01

    This regulatory guide consists of following 4 chapters: Description of the RA reactor, organization scheme, regulations for performing experiments; Regulations for staff on duty; Instructions for operating the vacuum systems, heavy water and helium systems; and evacuation in case of accident [sr

  16. Status of RA3 conversion studies

    International Nuclear Information System (INIS)

    Testoni, J.

    1983-01-01

    Studies carried out at CNEA in Argentina for the conversion of the RA3 3.5 MW reactor to LEU fuel dealt with neutronic, thermal hydraulic, safety analysis, as well as fuel manufacture. Some of the results for the neutronic studies are reported

  17. GENERALIZATION OF RAYLEIGH MAXIMUM LIKELIHOOD DESPECKLING FILTER USING QUADRILATERAL KERNELS

    Directory of Open Access Journals (Sweden)

    S. Sridevi

    2013-02-01

    Full Text Available Speckle noise is the most prevalent noise in clinical ultrasound images. It visibly looks like light and dark spots and deduce the pixel intensity as murkiest. Gazing at fetal ultrasound images, the impact of edge and local fine details are more palpable for obstetricians and gynecologists to carry out prenatal diagnosis of congenital heart disease. A robust despeckling filter has to be contrived to proficiently suppress speckle noise and simultaneously preserve the features. The proposed filter is the generalization of Rayleigh maximum likelihood filter by the exploitation of statistical tools as tuning parameters and use different shapes of quadrilateral kernels to estimate the noise free pixel from neighborhood. The performance of various filters namely Median, Kuwahura, Frost, Homogenous mask filter and Rayleigh maximum likelihood filter are compared with the proposed filter in terms PSNR and image profile. Comparatively the proposed filters surpass the conventional filters.

  18. Rayleigh-Taylor/gravitational instability in dense magnetoplasmas

    Energy Technology Data Exchange (ETDEWEB)

    Ali, S., E-mail: shahid.ali@ncp.edu.p [National Centre for Physics, Quaid-i-Azam University Campus, Islamabad (Pakistan); IPFN, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Ahmed, Z. [COMSATS Institute of Information Technology, Department of Physics, Wah Campus (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Physics Department, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Ahmad, I. [COMSATS Institute of Information Technology, Department of Physics, Islamabad Campus (Pakistan)

    2009-08-10

    The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

  19. Rayleigh-Taylor/gravitational instability in dense magnetoplasmas

    International Nuclear Information System (INIS)

    Ali, S.; Ahmed, Z.; Mirza, Arshad M.; Ahmad, I.

    2009-01-01

    The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

  20. Influence of velocity shear on the Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Guzdar, P.N.; Satyanarayana, P.; Huba, J.D.; Ossakow, S.L.

    1982-01-01

    The influence of a transverse velocity shear on the Rayleigh-Taylor instability is investigated. It is found that a sheared velocity flow can substantially reduce the growth rate of the Rayleigh-Taylor instability in short wavelength regime (i.e., kL>1 where L is the scale length of the density inhomogeneity), and causes the growth rate to maximize at kL<1.0. Applications of this result to ionospheric phenomena [equatorial spread F (ESF) and ionospheric plasma clouds] are discussed. In particular, the effect of shear could account for, at times, the 100's of km modulation observed on the bottomside of the ESF ionosphere and the km scale size wavelengths observed in barium cloud prompt striation phenomena

  1. An Experimental Study on Rayleigh-Benard Natural Convection

    International Nuclear Information System (INIS)

    Moon, Je Young; Chung, Bum Jin

    2012-01-01

    Core melt in a severe accident condition, forms a molten pool in the reactor vessel lower head. The molten pool is divided by a metallic pool (top) and an oxide pool (bottom) by the density difference. Due to the decay heat generated in oxide pool, Rayleigh- Benard natural convection heated from below and cooled from above occurs in the metallic pool. Experiments were performed to investigate Rayleigh- Benard natural convection as a preparatory study before an in-depth severe accident study. The natural convection heat transfers were measured varying the plate separation distance and the area of plate with and without the side wall. Using the analogy concept, heat transfer experiments were replaced by mass transfer experiments. A cupric acid.copper sulfate (H 2 SO 4 -CuSO 4 ) electroplating system was adopted as the mass transfer system and the electric currents were measured rather than the heat

  2. Reduced-Order Modeling of 3D Rayleigh-Benard Turbulent Convection

    Science.gov (United States)

    Hassanzadeh, Pedram; Grover, Piyush; Nabi, Saleh

    2017-11-01

    Accurate Reduced-Order Models (ROMs) of turbulent geophysical flows have broad applications in science and engineering; for example, to study the climate system or to perform real-time flow control/optimization in energy systems. Here we focus on 3D Rayleigh-Benard turbulent convection at the Rayleigh number of 106 as a prototype for turbulent geophysical flows, which are dominantly buoyancy driven. The purpose of the study is to evaluate and improve the performance of different model reduction techniques using this setting. One-dimensional ROMs for horizontally averaged temperature are calculated using several methods. Specifically, the Linear Response Function (LRF) of the system is calculated from a large DNS dataset using Dynamic Mode Decomposition (DMD) and Fluctuation-Dissipation Theorem (FDT). The LRF is also calculated using the Green's function method of Hassanzadeh and Kuang (2016, J. Atmos. Sci.), which is based on using numerous forced DNS runs. The performance of these LRFs in estimating the system's response to weak external forcings or controlling the time-mean flow are compared and contrasted. The spectral properties of the LRFs and the scaling of the accuracy with the length of the dataset (for the data-driven methods) are also discussed.

  3. General Switch-and-Stay Combing for Space Diversity over Rayleigh Fading Channels

    Directory of Open Access Journals (Sweden)

    Yawgeng A. Chau

    2012-01-01

    Full Text Available Three multibranch switch-and-stay combining (MSSC schemes are analyzed for Rayleigh fading channels, where different decision statistics for antenna switching (i.e., switch statistic are used. Let a and r denote the fading factor and the received baseband signal of a diversity branch, respectively. In contrast to the traditional MSSC that uses the faded signal-to-noise ratio (SNR of diversity branches as the corresponding switch statistic, to enhance the receiver performance, |r|, |ar|, and a new linear combination of a and |r| are used as switch statistics of the three MSSC schemes, respectively. For performance evaluation, the bit error rate (BER of BPSK is derived for the three MSSC schemes over both independent-and-identical distributed (i.i.d. and independent-and-nonidentical distributed (i.n.d. Rayleigh fading channels. To pursue optimal performance, the locally optimal switch threshold (ST of each MSSC scheme is obtained for general i.n.d. fading channels. In addition, the locally optimal ST becomes the globally optimal ST for i.i.d. channels. Numerical results based on the analysis and simulations are presented. In contrast to the MSSC over i.i.d. fading channels, we will show that the performance of MSSC schemes can be improved by increasing the number of branches, if i.n.d. channels are considered.

  4. The propagation of nonlinear rayleigh waves in layered elastic half-space

    International Nuclear Information System (INIS)

    Ahmetolan, S.

    2004-01-01

    In this work, the propagation of small but finite amplitude generalized Rayleigh waves in an elastic half-space covered by a different elastic layer of uniform and finite thickness is considered. The constituent materials are assumed to be homogeneous, isotropic, compressible hyperelastic. Excluding the harmonic resonance phenomena, it is shown that the nonlinear self modulation of generalized Rayleigh waves is governed asymptotically by a nonlinear Schrodinger (NLS) equation. The stability of the solutions and the existence of solitary wave-type solutions a NLS are strongly depend on the sign of the product of the coefficients of the nonlinear and dipersion terms of the equation.Therefore the analysis continues with the examination of dependence of these coefficients on the nonlinear material parameters. Three different models have been considered which are nonlinear layer-nonlinear half space, linear layer-nonlinear half space and nonlinear layer-linear half space. The behavior of the coefficients of the NLS equation was also analyzed the limit as h(thickness of the layer) goes to zero and k(the wave number) is constant. Then conclusions are drawn about the effect of nonlinear material parameters on the wave modulation. In the numerical investigations both hypothetical and real material models are used

  5. Experimental test of Neel's theory of the Rayleigh rule using gradually devitrified Co-based glass

    International Nuclear Information System (INIS)

    Lachowicz, H.K.

    2000-01-01

    It is shown that gradually devitrified Co-based nonmagnetostrictive metallic glass is an excellent model material to verify Louis Neel's theory of the Rayleigh rule. In the course of the calculations, Neel showed that the parameter p=bH c /a (where H c is the coercivity, a and b are the coefficients of a quadratic polynomial expressing the Rayleigh rule) is expected to range between 0.6 (hard magnets) and 1.6 (soft). However, the experimental values of this parameter, reported in the literature for a number of mono- and poly-crystalline magnets, are much greater than those expected from the theory presented by Neel (in some cases even by two orders of magnitude). The measurements, performed for a series of Co-based metallic glass samples annealed at gradually increasing temperature to produce nanocrystalline structures with differentiated density and size of the crystallites, have shown that the calculated values of the parameter p fall within the range expected from Neel's theory

  6. On the MIMO Capacity for Distributed System under Composite Rayleigh/Rician Fading and Shadowing

    Directory of Open Access Journals (Sweden)

    Santiago González-Aurioles

    2015-01-01

    Full Text Available Wireless channels are commonly affected by short-term fading and long-term fading (shadowing. The shadowing effects must be taken into account also when mobility is present in the wireless scenario. Using a composite fading model, the total channel capacity can be studied for a scenario with short-term Rayleigh fading along with shadowing. This work provides quantitative results for these kinds of scenarios with Rayleigh fading and shadowing, considering also multiple-input and multiple-output systems, which have not been previously reported. In addition, the channel capacity has been studied in depth in its relation with the shadowing level, signal to noise ratio, and the number of elements in the multiple-input and multiple-output system. Moreover, the channel performance with shadowing has been compared to the one without it. Furthermore, Rician model with shadowing is studied and its results are reported. In addition, correlated and experimental results are provided. It is identified that the distributed MIMO systems can benefit from shadowing in Rician channels. This advantage has not been reported previously. This type of fading is proposed for massive MIMO by others and our results open the door to emulate massive MIMO on a reverberation chamber.

  7. Laser speckle velocimetry applied to Rayleigh-Benard convection

    International Nuclear Information System (INIS)

    Arroyo, M.P.; Yonte, T.; Quintanilla, M.; Saviron, J.M.

    1986-01-01

    An application of speckle velocimetry technique to Rayleigh-Benard convection is presented. A 5-mW He-Ne laser allows precise determination of the two-dimensional velocity flow field, up to several mm/sec. The digital techniques used to analyze automatically the multiexposed photographs and to generate velocity and vorticity fields are described. The obtained results are in good agreement with previously reported data. The ability of the technique to cover other experimental conditions is discussed. 14 references

  8. Stochastic model of Rayleigh-Taylor turbulent mixing

    International Nuclear Information System (INIS)

    Abarzhi, S.I.; Cadjan, M.; Fedotov, S.

    2007-01-01

    We propose a stochastic model to describe the random character of the dissipation process in Rayleigh-Taylor turbulent mixing. The parameter alpha, used conventionally to characterize the mixing growth-rate, is not a universal constant and is very sensitive to the statistical properties of the dissipation. The ratio between the rates of momentum loss and momentum gain is the statistic invariant and a robust parameter to diagnose with or without turbulent diffusion accounted for

  9. Rayleigh-Taylor instability in an equal mass plasma

    Energy Technology Data Exchange (ETDEWEB)

    Adak, Ashish, E-mail: ashish-adak@yahoo.com [Department of Instrumentation Science, Jadavpur University, Kolkata 700 032 (India); Ghosh, Samiran, E-mail: sran-g@yahoo.com [Department of Applied Mathematics, University of Calcutta 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chakrabarti, Nikhil, E-mail: nikhil.chakrabarti@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

    2014-09-15

    The Rayleigh-Taylor (RT) instability in an inhomogeneous pair-ion plasma has been analyzed. Considering two fluid model for two species of ions (positive and negative), we obtain the possibility of the existence of RT instability. The growth rate of the RT instability as usual depends on gravity and density gradient scale length. The results are discussed in context of pair-ion plasma experiments.

  10. Measurement of molecular polarizability on Rayleigh light scattering

    International Nuclear Information System (INIS)

    Nerushev, O.A.; Novopashin, S.A.

    1994-01-01

    The installation for measuring the polarizability of atoms and molecules on Rayleigh light scattering is described. The measurements in gases with the known polarizability are used for a calibration. Test measurements are carried out on nitrogen, argon, carbon dioxide, vapours of water and acetone. The results of measurements are compared with the table data. The technique is used for measuring the polarizability of fullerene molecules. 6 refs., 2 figs

  11. Rayleigh-Taylor instability in a visco-plastic fluid

    International Nuclear Information System (INIS)

    Demianov, A Yu; Doludenko, A N; Son, E E; Inogamov, N A

    2010-01-01

    The Rayleigh-Taylor and Richtmyer-Meshkov instabilities of a visco-plastic fluid are discussed. The Bingham model is used as an effective rheological model which takes into account plastic effects. For the purposes of numerical simulation a one-mode disturbance of the contact surface between two fluids is considered. The main goal of this work is to construct numerical 2D and 3D models and to obtain the relationship between yield stress and the development of instability.

  12. Rayleigh-Taylor instability in a visco-plastic fluid

    Science.gov (United States)

    Demianov, A. Yu; Doludenko, A. N.; Inogamov, N. A.; Son, E. E.

    2010-12-01

    The Rayleigh-Taylor and Richtmyer-Meshkov instabilities of a visco-plastic fluid are discussed. The Bingham model is used as an effective rheological model which takes into account plastic effects. For the purposes of numerical simulation a one-mode disturbance of the contact surface between two fluids is considered. The main goal of this work is to construct numerical 2D and 3D models and to obtain the relationship between yield stress and the development of instability.

  13. Dipping-interface mapping using mode-separated Rayleigh waves

    Science.gov (United States)

    Luo, Y.; Xia, J.; Xu, Y.; Zeng, C.; Miller, R.D.; Liu, Q.

    2009-01-01

    Multichannel analysis of surface waves (MASW) method is a non-invasive geophysical technique that uses the dispersive characteristic of Rayleigh waves to estimate a vertical shear (S)-wave velocity profile. A pseudo-2D S-wave velocity section is constructed by aligning 1D S-wave velocity profiles at the midpoint of each receiver spread that are contoured using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. Based on the assumption that a dipping-layer model can be regarded as stepped flat layers, high-resolution linear Radon transform (LRT) has been proposed to image Rayleigh-wave dispersive energy and separate modes of Rayleigh waves from a multichannel record. With the mode-separation technique, therefore, a dispersion curve that possesses satisfactory accuracy can be calculated using a pair of consecutive traces within a mode-separated shot gather. In this study, using synthetic models containing a dipping layer with a slope of 5, 10, 15, 20, or 30 degrees and a real-world example, we assess the ability of using high-resolution LRT to image and separate fundamental-mode Rayleigh waves from raw surface-wave data and accuracy of dispersion curves generated by a pair of consecutive traces within a mode-separated shot gather. Results of synthetic and real-world examples demonstrate that a dipping interface with a slope smaller than 15 degrees can be successfully mapped by separated fundamental waves using high-resolution LRT. ?? Birkh??user Verlag, Basel 2009.

  14. Radiation protection at the RA Reactor in 1985, Part -4, decontamination and treatment of solid radioactive materials for the needs of RA reactor

    International Nuclear Information System (INIS)

    Plecas, I.; Vukovic, Z.; Blagojevic, R.; Kostadinovic, A.

    1985-01-01

    This report describes the activity of the decontamination and treatment team for the needs of the RA reactor, its equipment, working conditions, methods for decontamination, means of decontamination, type and quantity of decontaminated surfaces, number of decontaminated objects, quantity of collected radioactive solid wastes, their packaging, transport to the storage place and topography od radiation field in the storage during 1985 [sr

  15. Rayleigh-Taylor instability of cylindrical jets with radial motion

    International Nuclear Information System (INIS)

    Chen, X.M.; Schrock, V.E.; Peterson, P.F.

    1997-01-01

    Rayleigh-Taylor instability of an interface between fluids with different densities subjected to acceleration normal to itself has interested researchers for almost a century. The classic analyses of a flat interface by Rayleigh and Taylor have shown that this type of instability depends on the direction of acceleration and the density differences of the two fluids. Plesset later analyzed the stability of a spherically symmetric flows (and a spherical interface) and concluded that the instability also depends on the velocity of the interface as well as the direction and magnitude of radial acceleration. The instability induced by radial motion in cylindrical systems seems to have been neglected by previous researchers. This paper analyzes the Rayleigh-Taylor type of instability for a cylindrical surface with radial motions. The results of the analysis show that, like the spherical case, the radial velocity also plays an important role. As an application, the example of a liquid jet surface in an Inertial Confinement Fusion (ICF) reactor design is analyzed. (orig.)

  16. Growth rates of the ablative Rayleigh endash Taylor instability in inertial confinement fusion

    International Nuclear Information System (INIS)

    Betti, R.; Goncharov, V.N.; McCrory, R.L.; Verdon, C.P.

    1998-01-01

    A simple procedure is developed to determine the Froude number Fr, the effective power index for thermal conduction ν, the ablation-front thickness L 0 , the ablation velocity V a , and the acceleration g of laser-accelerated ablation fronts. These parameters are determined by fitting the density and pressure profiles obtained from one-dimensional numerical simulations with the analytic isobaric profiles of Kull and Anisimov [Phys. Fluids 29, 2067 (1986)]. These quantities are then used to calculate the growth rate of the ablative Rayleigh endash Taylor instability using the theory developed by Goncharov et al. [Phys. Plasmas 3, 4665 (1996)]. The complicated expression of the growth rate (valid for arbitrary Froude numbers) derived by Goncharov et al. is simplified by using reasonably accurate fitting formulas. copyright 1998 American Institute of Physics

  17. Stabilization of the Rayleigh - Taylor instability with convection in an ablatively accelerated laser plasma

    International Nuclear Information System (INIS)

    Bud'ko, A.B.; Liberman, M.A.

    1992-01-01

    In the framework of WKB approximation the problem is studied of stabilizing the Rayleigh - Taylor instability with unhomogeneous convective flow, developing in the ablation zone during the ablative acceleration of the laser target plasma. The eigenvalue (instability growth rates) problem is reduced to solving an algebraic equation with the coefficients depending on the unperturbed profile structure of hydrodynamic variables. For the important case of the incompressible plasma subsonic flow, the instability growth rates is shown to vanish at k=k 0 =max(2(g|∇ ln p|) 1/2 /ν). The consistency condition of the model consists in the smallness of the local Froude number in the region of instability development. However, as seen from the comparison with the numerical calculations, the model is well appicable also for the case of the sufficiently abrupt density gradient provided the Froude number is of order of unity

  18. Performance of equal gain combining with quantized phases in rayleigh fading channels

    KAUST Repository

    Rizvi, Umar H.

    2011-01-01

    In this paper, we analyze the error probability of equal gain combining with quantized channel phase compensation for binary phase shift keying signalling over Rayleigh fading channels. The probability density and characteristic functions of the combined signal amplitude are derived and used to compute the analytic expressions for the bit error probability in dependance of the number of quantization levels L, the number of diversity branches N-R and the average received signal-to-noise ratio. The analysis is utilized to outline the trade-off between N-R and L and to compare the performance with non-coherent binary frequency shift keying and differential binary phase shift keying schemes under diversity reception. © 2011 IEEE.

  19. Rayleigh-Taylor instability of two superposed conducting Walters B' elastico-viscous fluids in hydromagnetics

    International Nuclear Information System (INIS)

    Sharma, R.C.; Kumar, Pardeep

    1998-01-01

    The Rayleigh-Taylor instability of two superposed electrically conducting Walters elastico-viscous fluids (Model B') of uniform densities when the whole system is immersed in a uniform horizontal magnetic field has been studied. The stability analysis has been carried out, for mathematical simplicity, for two highly viscoelastic fluids of equal kinematic viscosities and equal kinematic viscoelasticities. For the stable configuration as in hydrodynamic case, the system is found to be stable or unstable for the wave-number range k (2v') -12 depending on kinematic viscoelasticity v'. For the unstable configuration, the magnetic field has got stabilizing effect and completely stabilizes certain wave-number range which was always unstable in the absence of magnetic field. The behaviour of growth rates with respect kinematic viscosity and kinematic viscoelasticity parameters are examined analytically. (author)

  20. Ventilation system in the RA reactor building - design specifications; Sistem ventilacije u objektu 'RA' - Tehnicki opis

    Energy Technology Data Exchange (ETDEWEB)

    Badrljica, R [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1984-09-15

    Protective role of the ventilation system of nuclear facilities involve construction of ventilation barriers which prevent release of radioactive particulates or gases, elimination od radioactive particulates and gases from the air which is released from contaminated zones into the reactor environment. Ventilation barriers are created by dividing the building into a number of ventilation zones with different sub pressure compared to the atmospheric pressure. The RA reactor building is divided into four ventilation zones. First zone is the zone of highest risk. It includes reactor core with horizontal experimental channels, underground rooms of the primary coolant system (D{sub 2}O), helium system, hot cells and the space above the the reactor core. Second zone is the reactor hall and the room for irradiated fuel storage. The third zone includes corridors in the basement, ground floor and first floor where the probability of contamination is small. The fourth zone includes the annex where the contamination risk is low. There is no have natural air circulation in the reactor building. Ventilators for air input and outlet maintain the sub pressure in the building (pressure lower than the atmospheric pressure). This prevents release of radioactivity into the atmosphere. Zastitne uloge ventilacionog sistema kod nuklearnih postrojenja obuhvataju formiranje ventilacionih barijera koje onemugucavaju sirenje radioaktivnih cestica ili gasova putem cirkulacije vazduha; eliminaciju radioaktivnih cestica i gasova iz vazduha koji se evakuise iz kontaminiranih prostora u okolinu reaktorskog postrojenja. Formiranje zastitnih ventilacionih barijera ostvaruje se obicno podelom unutrasnjosti objekta na vise ventilacionih zona razlicitih podpritisaka u odnosu na spoljni atmosferski pritisak. Celi prostor zgrade reaktora RA podeljen je u cetiri ventilacione zone. Prva zona je zona najveceg rizika, u koju spadaju reaktorsko jezgro sa horizontalnim eksperimentalnim kanalima, tehnoloske

  1. Ra: The Sun for Science and Humanity

    Science.gov (United States)

    1996-01-01

    To guide the development of the Ra Strategic Framework, we defined scientific and applications objectives. For our primary areas of scientific interest, we choose the corona, the solar wind, the Sun's effect on the Earth, and solar theory and model development. For secondary areas of scientific interest, we selected sunspots, the solar constant, the Sun's gravitational field, helioseismology and the galactic cosmic rays. We stress the importance of stereoscopic imaging, observations at high spatial, spectral, and temporal resolutions, as well as of long duration measurements. Further exploration of the Sun's polar regions is also important, as shown already by the Ulysses mission. From an applications perspective, we adopted three broad objectives that would derive complementary inputs for the Strategic Framework. These were to identify and investigate: possible application spin-offs from science missions, possible solar-terrestrial missions dedicated to a particular application, and possible future applications that require technology development. The Sun can be viewed as both a source of resources and of threats. Our principal applications focus was that of threat mitigation, by examining ways to improve solar threat monitoring and early warning systems. We compared these objectives to the mission objectives of past, current, and planned international solar missions. Past missions (1962-1980) seem to have been focused on improvement of scientific knowledge, using multiple instrument spacecraft. A ten year gap followed this period, during which the results from previous missions were analyzed and solar study programmes were prepared in international organizations. Current missions (1990-1996) focus on particular topics such as the corona, solar flares, and coronal mass ejections. In planned missions, Sun/Earth interactions and environmental effects of solar activity are becoming more important. The corona is the centre of interest of almost all planned missions

  2. RA Research nuclear reactor Part 1, RA Reactor operation and maintenance in 1987

    International Nuclear Information System (INIS)

    Sotic, O.; Martinc, R.; Cupac, S.; Sulem, B.; Badrljica, R.; Majstorovic, D.; Sanovic, V.

    1987-01-01

    RA research reacto was not operated due to the prohibition issued in 1984 by the Government of Serbia. Three major tasks were finished in order to fulfill the licensing regulations about safety of nuclear facilities which is the condition for obtaining permanent operation licence. These projects involved construction of the emergency cooling system, reconstruction of the existing special ventilation system, and renewal of the system for electric power supply of the reactor systems. Renewal of the RA reactor instrumentation system was initiated. Design project was done by the Russian Atomenergoeksport, and is foreseen to be completed by the end of 1988. The RA reactor safety report was finished in 1987. This annual report includes 8 annexes concerning reactor operation, activities of services and financial issues, and three special annexes: report on testing the emergency cooling system, report on renewal of the RA reactor and design specifications for reactor renewal and reconstruction [sr

  3. Measurements of neutron flux in the RA reactor; Merenje karakteristika neutronskog fluksa u reaktoru RA

    Energy Technology Data Exchange (ETDEWEB)

    Raisic, N [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    This report includes results of the following measurements performed at the RA reactor: thermal neutron flux in the experimental channels, epithermal and fast neutron flux, neutron flux in the biological shield, neutron flux distribution in the reactor cell.

  4. 228Ra and 226Ra measurement on a BaSO4 co-precipitation source

    International Nuclear Information System (INIS)

    Medley, Peter; Martin, Paul; Bollhöfer, Andreas; Parry, David

    2015-01-01

    One of the most commonly-used methods for determination of 226 Ra, particularly in water samples, utilises co-precipitation of Ra with BaSO 4 , followed by microfiltration to produce a source for alpha counting. This paper describes two extensions to BaSO 4 co-precipitation methods which enable determination of 228 Ra using the same source. The adaptations presented here do not introduce any contaminants that will affect the separation of radium or alpha counting for 226 Ra, and can be used for re-analysis of already existing sources prepared by BaSO 4 co-precipitation. The first adaptation uses detection of 228 Ac on the source by gamma spectrometry. The detection efficiency is high, allowing analysis of water samples at sufficiently low activity to be suitable in testing for compliance with drinking water quality standards. As 228 Ac grows in quickly, taking less than 2 days to reach equilibrium with the 228 Ra parent, this can also be useful in radiological emergency response situations. The second adaptation incorporates a method for the digestion of BaSO 4 sources, allowing separation of thorium and subsequent determination of 228 Th activity. Although ingrowth periods for 228 Th can be lengthy, very low detection limits for 228 Ra can be achieved with this technique. - Highlights: • We developed two methods for 228 Ra measurement on Ba(Ra)SO 4 co-precipitation sources. • Measurement by gamma spectrometry using the daughter 228 Ac is rapid. • Detection limits are suitable for assessment of drinking water quality. • The second approach uses alpha spectrometry on a separated Th fraction. • This is more sensitive than gamma spectrometry after an ingrowth period greater than about 1 month

  5. Radiation protection at the RA Reactor in 1998, RA reactor annual report, Part -2

    International Nuclear Information System (INIS)

    Ninkovic, M.; Pavlovic, R.; Mandic, M.; Pavlovic, S.; Grsic, Z.

    1998-01-01

    Radiation protection tasks which enable safe operation of the RA reactor, and are defined according the the legal regulations and IAEA safety recommendations are sorted into four categories in this report: (1) Control of the working environment, dosimetry at the RA reactor; (2) Radioactivity control in the vicinity of the reactor and meteorology measurements; (3) Collecting and treatment of fluid effluents; and (4) radioactive wastes, decontamination and actions. Each of the category is described as a separate annex of this report [sr

  6. RA Research nuclear reactor, Part II: radiation protection at the RA reactor in 1987

    International Nuclear Information System (INIS)

    Ninkovic, M.; Ajdacic, N.; Zaric, M.; Vukovic, Z.

    1987-01-01

    Radiation protection tasks which enable safe operation of the RA reactor, and are defined according the the legal regulations and IAEA safety recommendations are sorted into four categories in this report: (1) Control of the working environment, dosimetry at the RA reactor and radiation protection; (2) Radioactivity control in the vicinity of the reactor and meteorology measurements; (3) Decontamination and relevant actions, collecting and treatment of fluid effluents; and and solid radioactive wastes [sr

  7. Radiation protection at the RA Reactor in 1988, Part -2, RA reactor annual report

    International Nuclear Information System (INIS)

    Ninkovic, M.; Ajdacic, N.; Zaric, M.; Vukovic, Z.

    1988-01-01

    Radiation protection tasks which enable safe operation of the RA reactor, and are defined according the the legal regulations and IAEA safety recommendations are sorted into four categories in this report: (1) Control of the working environment, dosimetry at the RA reactor and radiation protection; (2) Radioactivity control in the vicinity of the reactor and meteorology measurements; (3) Decontamination and relevant actions, collecting and treatment of fluid effluents; and and solid radioactive wastes [sr

  8. Simultaneous determination of Ra-226, Ra-228 and Pb-210 using a successive coprecipitations techniques

    International Nuclear Information System (INIS)

    Vilhena Schayer Sabino, C. de; Kastner, S.M.S.; Amaral, A.M.

    1990-01-01

    Several techniques for determination of Ra-226, Ra228 and Pb-210. were developed and used in routine at CDTN in the laboratories of radiochemistry. The matrixes were: water and industrial wastes. Some problems of these techniques were the time spent for analyses and chemical separations, interferents, among others. Now-a-days the method in routine developed here is the one of successive coprecipitations, followed α and β countings of the Ra-226 and Ra-228 daughters. This method is based on coprecipitation, purification of barium radium sulfate with EDTA in acetic solution. Lead is dissolved, radium remains precipitated and suffers a new purification and the time for growing of their daughters is waited to be performed the simultaneous α and β countings for Ra-226 and Ra-228 determination. Pb-210 is analyzed in the floating of the first purification with a carrier of bismuth, and the time for Bi-210 growing is waited. Then it is precipitated as hydroxid, purified as phosphate and the β counting of Bi-210 is done. (author) [pt

  9. 226Ra, 228Ra and 40K in scales formed in boilers of industrial installations

    International Nuclear Information System (INIS)

    Poggi, Claudia M. Braga; Farias, Emerson Emiliano G. de; Hazin, Clovis A.; Gazineu, Maria Helena P.; Universidade Catolica de Pernambuco

    2011-01-01

    Many industrial processes involve the production of steam in boilers, which is sent through pipes to machines and other equipment used in different sectors of the installations. The water commonly used in these processes is groundwater, which generally has high concentrations of calcium and magnesium salts, that can co-precipitate with naturally occurring radioactive elements such as 226 Ra and 228 Ra creating radioactive scales, which are deposited in pipes, thus decreasing the efficiency of steam production. In addition, 40 K that is present in all soils and rocks with a concentration of about 0.012% of natural potassium can also be concentrated in these scales. No data was found in literature relating to radionuclides present in the scales formed on boilers in general. In this context, the purpose of this work was to determine concentrations of 226 Ra, 228 Ra and 40 K, in scales generated inside boilers from different industries in the cities of Caruaru, Paulista and Goiana, Pernambuco. Determination of the radionuclides concentration was performed by gamma spectrometry with an HPGe detector, calculating their specific activities. Activity concentrations of 226 Ra were in the range of -1 and 228 Ra activity concentrations varied from 1 . Activity concentrations of 40 K were in the range of -1 . All these activity concentrations were lower than the limits established by the Brazilian Nuclear Energy Commission of for this type of matrix. (author)

  10. Factors affecting {sup 223}Ra therapy: clinical experience after 532 cycles from a single institution

    Energy Technology Data Exchange (ETDEWEB)

    Etchebehere, Elba C. [The University of Texas MD Anderson Cancer Center, Department of Nuclear Medicine, Houston, TX (United States); Campinas State University (Unicamp), Department of Nuclear Medicine, Campinas (Brazil); Milton, Denai R. [The University of Texas MD Anderson Cancer Center, Department of Biostatistics, Houston, TX (United States); Araujo, John C. [The University of Texas MD Anderson Cancer Center, Department of Genitourinary Medical Oncology, Houston, TX (United States); Swanston, Nancy M.; Macapinlac, Homer A.; Rohren, Eric M. [The University of Texas MD Anderson Cancer Center, Department of Nuclear Medicine, Houston, TX (United States)

    2016-01-15

    The aim of this study was to identify baseline features that predict outcome in {sup 223}Ra therapy. We retrospectively reviewed 110 patients with metastatic castration-resistant prostate cancer treated with {sup 223}Ra. End points were overall survival (OS), progression-free survival (PFS), bone event-free survival (BeFS), and bone marrow failure (BMF). The following parameters were evaluated prior to the first {sup 223}Ra cycle: serum levels of hemoglobin (Hb), prostate-specific antigen (PSA), alkaline phosphatase (ALP), Eastern Cooperative Oncology Group (ECOG) status, pain score, use of chemotherapy, and external beam radiation therapy (EBRT). During/after {sup 223}Ra we evaluated: the total number of radium cycles (Ra{sub Tot}), the PSA doubling time (PSA{sub DT}), and the use of chemotherapy, EBRT, abiraterone, and enzalutamide. A significant reduction of ALP (p < 0.001) and pain score (p = 0.041) occurred throughout the {sup 223} Ra cycles. The risk of progression was associated with declining ECOG status [hazard ratio (HR) = 3.79; p < 0.001] and decrease in PSA{sub DT} (HR = 8.22; p < 0.001). Ra{sub Tot}, ALP, initial ECOG status, initial pain score, and use of abiraterone were associated with OS (p ≤ 0.008), PFS (p ≤ 0.003), and BeFS (p ≤ 0.020). Ra{sub Tot}, ALP, initial ECOG status, and initial pain score were significantly associated with BMF (p ≤ 0.001) as well as Hb (p < 0.001) and EBRT (p = 0.009). On multivariable analysis, only Ra{sub Tot} and abiraterone remained significantly associated with OS (p < 0.001; p = 0.033, respectively), PFS (p < 0.001; p = 0.041, respectively), and BeFS (p < 0.001; p = 0.019, respectively). Additionally, Ra{sub Tot} (p = 0.027) and EBRT (p = 0.013) remained significantly associated with BMF. Concomitant use of abiraterone and {sup 223}Ra seems to have a beneficial effect, while the EBRT may increase the risk of BMF. (orig.)

  11. Epidemiological studies of German patients injected with Ra-224

    International Nuclear Information System (INIS)

    Mays, C.W.; Spiess, H.

    1983-01-01

    The health of 898 patients who received repeated injections of short-lived 224 Ra after World War II, mainly for the treatment of tuberculosis and ankylosing spondylitis has been followed. As of 1980, 53 of these patients had developed bone sarcoma vs only 0.2 cases expected naturally. Two patients with bone sarcoma subsequently developed an additional bone sarcoma. No new bone sarcomas have been reported since the end of 1974. For the patients in each category, the tumor rate at every year after 224 Ra injection was calculated by dividing the yearly number of bone sarcomas by the number of patients whose follow-up extended to that year. This corrected for the effects of death and incomplete follow-up. The yearly tumor rates were then summed to obtain the cumulative tumor rate. Dividing by the average skeletal dose in rads yielded the cumulative risk. The cumulative tumor risk was about 200 bone sarcomas/10 6 person rad of average skeletal dose and, with the dosimetric assumptions used, was not statistically different for (a) juveniles vs adults, (b) males vs females, or (c) TB patients vs spondylitic patients

  12. IL-1Ra (recombinant human IL-1 receptor antagonist in the treatment of rheumatoid arthritis: the efficacy

    Directory of Open Access Journals (Sweden)

    L. Cozzi

    2011-09-01

    Full Text Available Interleukin 1 receptor antagonist (IL-1Ra is a naturally occurring IL-1 inhibitor, acting as a “receptor antagonist”, which blocks IL-1 mediated signal transduction. In 1990 IL-1Ra was cloned and later on, a large numbers of studies led to disclosure of the crucial importance of the imbalance between IL-1 and IL-1Ra in the pathogenesis of rheumatoid arthritis (RA. In 1991, almost 8 years after the initial isolation of IL-1, recombinant IL-1Ra (IL-1ra, Kineret was introduced in clinical trials involving patients with RA. Between 2001 and 2002 IL-1ra was approved by the US Food and Drug Administration and by the European Agency for the Evaluation of the Medicinal Products and in 2003 it was registered in Italy, too. In RA recombinant IL-1ra has been evaluated in 5 randomized, placebo-controlled clinical trials involving more than 2900 patients. Two of the trials involved the use of IL-1ra as monotherapy versus placebo and two trials in combination with methotrexate (MTX; the last trial explored the use of a fixed 100 mg/day IL-1ra dosage in a RA patient population including a wide array of co-morbid conditions as well as concomitant medications. The studies confirmed both the efficacy and the safety of IL-1ra in patients with active and severe RA. 43% of patients receiving 150 mg/day IL-1ra achieved a 20% response according to the American College of Rheumatology criteria (ACR20, compared to 27% in the placebo group. In the MTX combination therapy study, 42% of the patients receiving 1 mg/Kg/day of IL-1ra achieved an ACR20, 24% an ACR50 and 10% an ACR70. In each study, significant improvements in the Health Assessment Questionnaire scores (HAQ were observed. There were rapid gains in the number of days at work or domestic activity in the treated patients, and the increases in productivity were dose related. At early 24 weeks, there was significant reduction of both the score for progression of joint space narrowing (JSN and the Total modified

  13. Preparation of 227Ac by neutron irradiation of 226Ra

    International Nuclear Information System (INIS)

    Kukleva, E.; Kozempel, J.; Vlk, M.; Micolova, P.; Vopalka, D.

    2015-01-01

    Radium-223 is prospective alpha-emitting therapeutic radionuclide for targeted radionuclide therapy. Although 223 Ra is formed naturally by the decay of 235 U, for practical reasons its preparation involves neutron irradiation of 226 Ra. The α-decay of the 227 Ra (T 12 = 43 min.) produced via 226 Ra(n,γ) 227 Ra reaction leads to 227 Ac, a mother nuclide of 227 Th and 223 Ra subsequently. Irradiation target radium material is generally available in multi-gram quantities from historical stock. Main aim of this study was to experimentally and theoretically evaluate and verify available literature data on production of 223 Ra. According to data obtained from γ-spectra, the approximate yield values were determined and effective cross-section for the 223 Ra production was calculated. (authors)

  14. Skeletal dosimetry of injected 226RA in young adult beagles

    International Nuclear Information System (INIS)

    Lloyd, R.D.; Mays, C.W.; Atherton, D.R.

    1986-01-01

    Revised equations are presented for the skeletal dose to young adult beagles from 226 Ra injection. For 0.1 kg of skel/kg body and given 1 μCi 226 Ra/kg with 210 Pb/ 226 Ra = 0.05, the average skeletal dose in rad at 6 yr is 226 Ra = 1200, 222 Rn -> 214 Po = 1050, injected 210 Pb = 56 and 210 Pb from Rn decay in bone = 22. For a Pb/Ra ratio = 0.4, dose from injected 210 Pb is about 20% of that from 226 Ra -> 214 Po. A similar but not numerically indentical relationship obtains for ingested 226 Ra, so the dose from 210 Pb should be included in any study of 226 Ra effects. (orig.)

  15. 226Ra and 228Ra in ground water of the Cambrian-Ordovician Aquifer System in northern Illinois

    International Nuclear Information System (INIS)

    Gilkeson, R.H.; Holtzman, R.B.

    1982-01-01

    Over a large region of Illinois, ground water of the Cambrian-Ordovician Aquifer System exceeds the US EPA drinking water standard of 5 pCi/L for the combined concentration of 226 Ra and 228 Ra. 226 Ra concentrations range from 226 Ra is the geochemistry of uranium in the ground-water flow system, while the 228 Ra activity in ground water which ranges from 232 Th-bearing minerals in the aquifer strata. The comparison of recent analyses to historical data gathered over the last 20 years indicates that, with few exceptions, 226 Ra and 228 Ra activities in ground water have remained constant. The combined concentrations of the two nuclides in ground water of the aquifer system ranged from 226 Ra concentrations were high (greater than or equal to 10 pCi/L), those of 228 Ra were low (less than or equal to 2 pCi/L), but, with few exceptions, in regions where 228 Ra concentrations were high, those of 226 Ra were also high. The range of values raises questions concerning the validity of the US EPA regulation which requires analysis for 228 Ra only when the concentration of 226 Ra exceeds 3.0 pCi/L

  16. Preliminary study of Rayleigh-Taylor instability in wire-array Z-pinch

    International Nuclear Information System (INIS)

    He Kaihui; Feng Kaiming; Li Qiang; Gao Chunming

    2000-01-01

    It is important to research into the MHD Rayleigh-Taylor instability developed in Z-pinch implosion. A snowplough model of the single wire Z-pinch is presented. The perturbation amplitude of Rayleigh-Taylor instability in the wire-array Z-pinch is analyzed quantitatively. Sheared axial flow is put forward to mitigate and reduce the Rayleigh-Taylor instability. And other approaches used to mitigate MHD instability in such a super-fast process are explored

  17. Determination of 226Ra by alpha spectrometry of liquid scintillation

    International Nuclear Information System (INIS)

    Nobrega, A.W.; Sachett, I.A.; Hespanhol, E.C.B.

    1987-01-01

    The determination of 226 Ra in environmental samples using alpha spectrometry in liquid scintilation is studied. The Radon 1-2 emanation method and 226 Ra separation process of other radionuclides alpha emissors are analyzed. The use of 226 Ra coprecipitation with barium sulphate is evaluated. (M.J.C.) [pt

  18. Rayleigh radiance computations for satellite remote sensing: accounting for the effect of sensor spectral response function.

    Science.gov (United States)

    Wang, Menghua

    2016-05-30

    To understand and assess the effect of the sensor spectral response function (SRF) on the accuracy of the top of the atmosphere (TOA) Rayleigh-scattering radiance computation, new TOA Rayleigh radiance lookup tables (LUTs) over global oceans and inland waters have been generated. The new Rayleigh LUTs include spectral coverage of 335-2555 nm, all possible solar-sensor geometries, and surface wind speeds of 0-30 m/s. Using the new Rayleigh LUTs, the sensor SRF effect on the accuracy of the TOA Rayleigh radiance computation has been evaluated for spectral bands of the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) satellite and the Joint Polar Satellite System (JPSS)-1, showing some important uncertainties for VIIRS-SNPP particularly for large solar- and/or sensor-zenith angles as well as for large Rayleigh optical thicknesses (i.e., short wavelengths) and bands with broad spectral bandwidths. To accurately account for the sensor SRF effect, a new correction algorithm has been developed for VIIRS spectral bands, which improves the TOA Rayleigh radiance accuracy to ~0.01% even for the large solar-zenith angles of 70°-80°, compared with the error of ~0.7% without applying the correction for the VIIRS-SNPP 410 nm band. The same methodology that accounts for the sensor SRF effect on the Rayleigh radiance computation can be used for other satellite sensors. In addition, with the new Rayleigh LUTs, the effect of surface atmospheric pressure variation on the TOA Rayleigh radiance computation can be calculated precisely, and no specific atmospheric pressure correction algorithm is needed. There are some other important applications and advantages to using the new Rayleigh LUTs for satellite remote sensing, including an efficient and accurate TOA Rayleigh radiance computation for hyperspectral satellite remote sensing, detector-based TOA Rayleigh radiance computation, Rayleigh radiance calculations for high altitude

  19. Finite-thickness effects on the Rayleigh-Taylor instability in accelerated elastic solids

    Science.gov (United States)

    Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

    2017-05-01

    A physical model has been developed for the linear Rayleigh-Taylor instability of a finite-thickness elastic slab laying on top of a semi-infinite ideal fluid. The model includes the nonideal effects of elasticity as boundary conditions at the top and bottom interfaces of the slab and also takes into account the finite transit time of the elastic waves across the slab thickness. For Atwood number AT=1 , the asymptotic growth rate is found to be in excellent agreement with the exact solution [Plohr and Sharp, Z. Angew. Math. Mech. 49, 786 (1998), 10.1007/s000330050121], and a physical explanation is given for the reduction of the stabilizing effectiveness of the elasticity for the thinner slabs. The feedthrough factor is also calculated.

  20. Modeling of the thermal boundary layer in turbulent Rayleigh-Bénard convection

    Science.gov (United States)

    Emran, Mohammad; Shishkina, Olga

    2016-11-01

    We report modeling of the thermal boundary layer in turbulent Rayleigh-Bénard convection (RBC), which incorporates the effect of turbulent fluctuations. The study is based on the thermal boundary layer equation from Shishkina et al., and new Direct Numerical Simulations (DNS) of RBC in a cylindrical cell of the aspect ratio 1, for the Prandtl number variation of several orders of magnitude. Our modeled temperature profiles are found to agree with the DNS much better than those obtained with the classical Prandtl-Blasius or Falkner-Skan approaches. The work is supported by the Deutsche Forschungsgemeinschaft (DFG) under the Grant Sh405/4 - Heisenberg fellowship and SFB963, Project A06.

  1. Generalized Euler transformation for summing strongly divergent Rayleigh-Schroedinger perturbation series: the Zeeman effect

    International Nuclear Information System (INIS)

    Silverman, J.N.

    1983-01-01

    A generalized Euler transformation (GET) is introduced which provides a powerful alternative method of accurately summing strongly divergent Rayleigh-Schroedinger (RS) perturbation series when other summability methods fail or are difficult to apply. The GET is simple to implement and, unlike a number of other summation procedures, requires no a priori knowledge of the analytic properties of the function underlying the RS series. Application of the GET to the difficult problem of the RS weak-field ground-state eigenvalue series of the hydrogen atom in a magnetic field (quadratic Zeeman effect) yields sums of good accuracy over a very wide range of field strengths up to the most intense fields of 10 14 G. The GET results are compared with those obtained by other summing methods

  2. Observation of Self-Similar Behavior of the 3D, Nonlinear Rayleigh-Taylor Instability

    International Nuclear Information System (INIS)

    Sadot, O.; Smalyuk, V.A.; Delettrez, J.A.; Sangster, T.C.; Goncharov, V.N.; Meyerhofer, D.D.; Betti, R.; Shvarts, D.

    2005-01-01

    The Rayleigh-Taylor unstable growth of laser-seeded, 3D broadband perturbations was experimentally measured in the laser-accelerated, planar plastic foils. The first experimental observation showing the self-similar behavior of the bubble size and amplitude distributions under ablative conditions is presented. In the nonlinear regime, the modulation σ rms grows as α σ gt 2 , where g is the foil acceleration, t is the time, and α σ is constant. The number of bubbles evolves as N(t)∝(ωt√(g)+C) -4 and the average size evolves as (t)∝ω 2 gt 2 , where C is a constant and ω=0.83±0.1 is the measured scaled bubble-merging rate

  3. Nonlinear traveling waves in rotating Rayleigh-Bacute enard convection: Stability boundaries and phase diffusion

    International Nuclear Information System (INIS)

    Liu, Y.; Ecke, R.E.

    1999-01-01

    We present experimental measurements of a sidewall traveling wave in rotating Rayleigh-Bacute enard convection. The fluid, water with Prandtl number about 6.3, was confined in a 1-cm-high cylindrical cell with radius-to-height ratio Γ=5. We used simultaneous optical-shadowgraph, heat-transport, and local temperature measurements to determine the stability and characteristics of the traveling-wave state for dimensionless rotation rates 60<Ω<420. The state is well described by the one-dimensional complex Ginzburg-Landau (CGL) equation for which the linear and nonlinear coefficients were determined for Ω=274. The Eckhaus-Benjamin-Feir-stability boundary was established and the phase-diffusion coefficient and nonlinear group velocity were determined in the stable regime. Higher-order corrections to the CGL equation were also investigated. copyright 1999 The American Physical Society

  4. Air-mass flux measurement system using Doppler-shifted filtered Rayleigh scattering

    Science.gov (United States)

    Shirley, John A.; Winter, Michael

    1993-01-01

    An optical system has been investigated to measure mass flux distributions in the inlet of a high speed air-breathing propulsion system. Rayleigh scattered light from air is proportional to the number density of molecules and hence can be used to ascertain the gas density in a calibrated system. Velocity field measurements are achieved by spectrally filtering the elastically-scattered Doppler-shifted light with an absorbing molecular filter. A novel anamorphic optical collection system is used which allows optical rays from different scattering angles, that have different Doppler shifts, to be recorded separately. This is shown to obviate the need to tune the laser through the absorption to determine velocities, while retaining the ability to make spatially-resolved measurements along a line. By properly selecting the laser tuning and filter parameters, simultaneous density measurements can be made. These properties are discussed in the paper and experiments demonstrating the velocimetry capability are described.

  5. Linear Rayleigh-Taylor instability in an accelerated Newtonian fluid with finite width

    Science.gov (United States)

    Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

    2018-04-01

    The linear theory of Rayleigh-Taylor instability is developed for the case of a viscous fluid layer accelerated by a semi-infinite viscous fluid, considering that the top interface is a free surface. Effects of the surface tensions at both interfaces are taken into account. When viscous effects dominate on surface tensions, an interplay of two mechanisms determines opposite behaviors of the instability growth rate with the thickness of the heavy layer for an Atwood number AT=1 and for sufficiently small values of AT. In the former case, viscosity is a less effective stabilizing mechanism for the thinnest layers. However, the finite thickness of the heavy layer enhances its viscous effects that, in general, prevail on the viscous effects of the semi-infinite medium.

  6. Stabilization of Rayleigh-Taylor instability due to the spontaneous magnetic field in laser produced plasma

    International Nuclear Information System (INIS)

    Ogasawara, Masatada; Takita, Masami.

    1981-08-01

    Spontaneous magnetic fields due to the temperature gradient nabla T 0 produced by a focussed laser beam on one point of a pellet are taken into account in deriving the dispersion relation of Rayleigh-Taylor instability. Growth rate γ decreases with time. Density fluctuation with wavelength shorter than 1.5(R/L sub(T)) x (n sub(s)/n 0 )sup(1/2) μm is remarkably stabilized, where R, L sub(T), n sub(s) and n 0 are the radius of a pellet, L sub(T)sup(-1) = + nabla T 0 /T 0 + , number densities of solid and the pellet. Validity condition of the theory is γt 0 >> 1 or in another form R >> L, where t 0 is the time of thermal expansion of a pellet and L -1 = + nabla n 0 /n 0 + . (author)

  7. Rayleigh scattering of Moessbauer radiation in superionic conductor RbAg4I5

    International Nuclear Information System (INIS)

    Ovanesyan, N.S.; Goffman, V.G.; Sokolov, V.B.; Tkachev, V.V.

    1984-01-01

    The dynamical properties of RbAg 4 I 5 has been investiaated by Rayleigh scattering of Moessbauer radiation (RSMR) with wave-length lambda = 0.86 A. The character of Ag + ion oscillatory motion and diffusion in RbAg 4 I 5 depending on temperature including the phase transitions region is studied. It is shown that in the superionic crystal RbAg 4 I 5 the diffusion process is strongly correlated, i.e. a great number of initial and final states at diffusion jumps coincides. The observed broadening can be less than the expected one by value orders. Diffusion correlation can strongly reduce the activation barrier and lead to anomalously high ionic conduction

  8. Research nuclear reactor RA - Annual Report 1997; Istrazivacki nuklearni reaktor RA - Izvestaj za 1997. godinu

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O [Vinca Institute of Nuclear Sciences, Beograd (Serbia and Montenegro)

    1997-12-01

    RA reactor is not in operation since 1984, activities related to revitalisation of the RA reactor started in 1986. The planned actions related to renewal of the reactor components were finished except for the most important action, related to exchange of complete reactor instrumentation which was delayed. Only 80% of the instrumentation was delivered until September 1991. Since then any delivery of components to Yugoslavia was stopped because of the sanctions imposed to our country. The existing RA reactor instrumentation was dismantled. Control and maintenance of the reactor components was done regularly and efficiently. Fuel inspection by the IAEA safeguards inspectors was done on a monthly basis. There have been on the average 42 employees at the RA reactor which is considered sufficient for maintenance and repair conditions. The problem of financing the reactor activities and maintenance remains unsolved. Research reactor RA Annual report for year 1997 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection. [Serbo-Croat] Reaktor RA nije u pogonu od 1984, aktivnosti na revitalizaciji, rekostrukciji i modernizaciji reaktorski sistema zapocete su 1986. godine. Okoncan je niz zahvata na opremi postrojenja kojima ce se u narednom periodu omoguciti kontinualan i pouzdan rad ovog reaktora. Poslednji, i ujedno najveci zahvat, koji se odnosi na zamenu celokupne instrumentacije kasni zbog zastoja u isporuci opreme koja se izradjuje u Sovjetskom savezu. Do septembra 1991. godine isporuceno svega 80% od predvidjene kolicine. Od tada je svaka isporuka obustavljena, a razlog je privremena zabrana na sve isporuke opreme za Jugoslaviju usled sankcija uvedenih od strane organizacije Ujedinjenih nacija. Demontirana je postojeca instrumentacija. Kontrola i odrzavanje celopkupne opreme postrojenja, kao i remontni radovi izvrsavani su redovno i efikasno. Kontrola goriva od strane safeguard inspektora MAAE obavljana

  9. Rayleigh scattering and nonlinear inversion of elastic waves

    Energy Technology Data Exchange (ETDEWEB)

    Gritto, Roland [Univ. of California, Berkeley, CA (United States)

    1995-12-01

    Rayleigh scattering of elastic waves by an inclusion is investigated and the limitations determined. In the near field of the inhomogeneity, the scattered waves are up to a factor of 300 stronger than in the far field, excluding the application of the far field Rayleigh approximation for this range. The investigation of the relative error as a function of parameter perturbation shows a range of applicability broader than previously assumed, with errors of 37% and 17% for perturbations of -100% and +100%, respectively. The validity range for the Rayleigh limit is controlled by large inequalities, and therefore, the exact limit is determined as a function of various parameter configurations, resulting in surprisingly high values of up to kpR = 0.9. The nonlinear scattering problem can be solved by inverting for equivalent source terms (moments) of the scatterer, before the elastic parameters are determined. The nonlinear dependence between the moments and the elastic parameters reveals a strong asymmetry around the origin, which will produce different results for weak scattering approximations depending on the sign of the anomaly. Numerical modeling of cross hole situations shows that near field terms are important to yield correct estimates of the inhomogeneities in the vicinity of the receivers, while a few well positioned sources and receivers considerably increase the angular coverage, and thus the model resolution of the inversion parameters. The pattern of scattered energy by an inhomogeneity is complicated and varies depending on the object, the wavelength of the incident wave, and the elastic parameters involved. Therefore, it is necessary to investigate the direction of scattered amplitudes to determine the best survey geometry.

  10. On Lamb and Rayleigh wave convergence in viscoelastic tissues

    Energy Technology Data Exchange (ETDEWEB)

    Nenadic, Ivan Z; Urban, Matthew W; Aristizabal, Sara; Mitchell, Scott A; Humphrey, Tye C; Greenleaf, James F, E-mail: Nenadic.Ivan@mayo.edu [Department of Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905 (United States)

    2011-10-21

    Characterization of the viscoelastic material properties of soft tissue has become an important area of research over the last two decades. Our group has been investigating the feasibility of using a shear wave dispersion ultrasound vibrometry (SDUV) method to excite Lamb waves in organs with plate-like geometry to estimate the viscoelasticity of the medium of interest. The use of Lamb wave dispersion ultrasound vibrometry to quantify the mechanical properties of viscoelastic solids has previously been reported. Two organs, the heart wall and the spleen, can be readily modeled using plate-like geometries. The elasticity of these two organs is important because they change in pathological conditions. Diastolic dysfunction is the inability of the left ventricle (LV) of the heart to supply sufficient stroke volumes into the systemic circulation and is accompanied by the loss of compliance and stiffening of the LV myocardium. It has been shown that there is a correlation between high splenic stiffness in patients with chronic liver disease and strong correlation between spleen and liver stiffness. Here, we investigate the use of the SDUV method to quantify the viscoelasticity of the LV free-wall myocardium and spleen by exciting Rayleigh waves on the organ's surface and measuring the wave dispersion (change of wave velocity as a function of frequency) in the frequency range 40-500 Hz. An equation for Rayleigh wave dispersion due to cylindrical excitation was derived by modeling the excised myocardium and spleen with a homogenous Voigt material plate immersed in a nonviscous fluid. Boundary conditions and wave potential functions were solved for the surface wave velocity. Analytical and experimental convergence between the Lamb and Rayleigh waves is reported in a finite element model of a plate in a fluid of similar density, gelatin plate and excised porcine spleen and left-ventricular free-wall myocardium.

  11. Shear flow stabilization of the hydromagnetic Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Roderick, N.F.; Shumlak, U.; Douglas, M.; Peterkin, R.E. Jr.; Ruden, E.

    1997-01-01

    Numerical simulations have indicated that shear flow may help stabilize the hydromagnetic Rayleigh-Taylor instability in imploding plasma z-pinches. A simple extension to a model presented in Chandrasekhar has been developed to study the linear stability of incompressible plasma subjected to both a shear flow and acceleration. The model has been used to investigate the stability plasma implosion schemes using externally imposed velocity shear which develops from the plasma flow itself. Specific parameters were chosen to represent plasma implosions driven by the Saturn and PBFA-Z, pulsed power generators at Sandia National Laboratories. Results indicate a high shear is necessary to stabilize the z-pinch implosions studied

  12. Rayleigh-Taylor instability in accelerated elastic-solid slabs

    Science.gov (United States)

    Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

    2017-12-01

    We develop the linear theory for the asymptotic growth of the incompressible Rayleigh-Taylor instability of an accelerated solid slab of density ρ2, shear modulus G , and thickness h , placed over a semi-infinite ideal fluid of density ρ110.1007/s000330050121] to arbitrary values of AT and unveil the singular feature of an instability threshold below which the slab is stable for any perturbation wavelength. As a consequence, an accelerated elastic-solid slab is stable if ρ2g h /G ≤2 (1 -AT) /AT .

  13. Analytical evaluation of atomic form factors: Application to Rayleigh scattering

    Energy Technology Data Exchange (ETDEWEB)

    Safari, L., E-mail: laleh.safari@ist.ac.at [IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg (Austria); Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Santos, J. P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Amaro, P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg (Germany); Jänkälä, K. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Fratini, F. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Institute of Atomic and Subatomic Physics, TU Wien, Stadionallee 2, 1020 Wien (Austria); Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG (Brazil)

    2015-05-15

    Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.

  14. Experimental demonstration of the Rayleigh acoustic viscous boundary layer theory.

    Science.gov (United States)

    Castrejón-Pita, J R; Castrejón-Pita, A A; Huelsz, G; Tovar, R

    2006-03-01

    Amplitude and phase velocity measurements on the laminar oscillatory viscous boundary layer produced by acoustic waves are presented. The measurements were carried out in acoustic standing waves in air with frequencies of 68.5 and 114.5 Hz using laser Doppler anemometry and particle image velocimetry. The results obtained by these two techniques are in good agreement with the predictions made by the Rayleigh viscous boundary layer theory and confirm the existence of a local maximum of the velocity amplitude and its expected location.

  15. Resonance scattering of Rayleigh waves by a mass defect

    International Nuclear Information System (INIS)

    Croitoru, M.; Grecu, D.

    1978-06-01

    The resonance scattering of an incident Rayleigh wave by a mass defect extending over a small cylindrical region situated in the surface of a semi-infinite isotropic, elastic medium is investigated by means of the Green's function method. The form of the differential cross-section for the scattering into different channels exhibits a strong resonance phenomenon at two frequencies. The expression of the resonance frequencies as well as of the corresponding widths depends on the relative change in mass density. The main assumption that the wavelengths of incoming and scattered wave are large compared to the defect dimension implies a large relative mass-density change. (author)

  16. Multiwavelength ytterbium-Brillouin random Rayleigh feedback fiber laser

    Science.gov (United States)

    Wu, Han; Wang, Zinan; Fan, Mengqiu; Li, Jiaqi; Meng, Qingyang; Xu, Dangpeng; Rao, Yunjiang

    2018-03-01

    In this letter, we experimentally demonstrate the multiwavelength ytterbium-Brillouin random fiber laser for the first time, in the half-open cavity formed by a fiber loop mirror and randomly distributed Rayleigh mirrors. With a cladding-pumped ytterbium-doped fiber and a long TrueWave fiber, the narrow linewidth Brillouin pump can generate multiple Brillouin Stokes lines with hybrid ytterbium-Brillouin gain. Up to six stable channels with a spacing of about 0.06 nm are obtained. This work extends the operation wavelength of the multiwavelength Brillouin random fiber laser to the 1 µm band, and has potential in various applications.

  17. Rayleigh-Brillouin spectrum in special relativistic hydrodynamics

    International Nuclear Information System (INIS)

    Garcia-Perciante, A. L.; Garcia-Colin, L. S.; Sandoval-Villalbazo, A.

    2009-01-01

    In this paper we calculate the Rayleigh-Brillouin spectrum for a relativistic simple fluid according to three different versions available for a relativistic approach to nonequilibrium thermodynamics. An outcome of these calculations is that Eckart's version predicts that such spectrum does not exist. This provides an argument to question its validity. The remaining two results, which differ one from another, do provide a finite form for such spectrum. This raises the rather intriguing question as to which of the two theories is a better candidate to be taken as a possible version of relativistic nonequilibrium thermodynamics. The answer will clearly require deeper examination of this problem.

  18. Statistical approach of weakly nonlinear ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Garnier, J.; Masse, L.

    2005-01-01

    A weakly nonlinear model is proposed for the Rayleigh-Taylor instability in presence of ablation and thermal transport. The nonlinear effects for a single-mode disturbance are computed, included the nonlinear correction to the exponential growth of the fundamental modulation. Mode coupling in the spectrum of a multimode disturbance is thoroughly analyzed by a statistical approach. The exponential growth of the linear regime is shown to be reduced by the nonlinear mode coupling. The saturation amplitude is around 0.1λ for long wavelengths, but higher for short instable wavelengths in the ablative regime

  19. Size estimates of nobel gas clusters by Rayleigh scattering experiments

    Institute of Scientific and Technical Information of China (English)

    Pinpin Zhu (朱频频); Guoquan Ni (倪国权); Zhizhan Xu (徐至展)

    2003-01-01

    Noble gases (argon, krypton, and xenon) are puffed into vacuum through a nozzle to produce clusters for studying laser-cluster interactions. Good estimates of the average size of the argon, krypton and xenon clusters are made by carrying out a series of Rayleigh scattering experiments. In the experiments, we have found that the scattered signal intensity varied greatly with the opening area of the pulsed valve. A new method is put forward to choose the appropriate scattered signal and measure the size of Kr cluster.

  20. Rayleigh-Benard convection as a Nambu-metriplectic problem

    International Nuclear Information System (INIS)

    Bihlo, A

    2008-01-01

    The traditional Hamiltonian structure of the equations governing conservative Rayleigh-Benard convection (RBC) is singular, i.e., its Poisson bracket possesses nontrivial Casimir functionals. We show that a special form of one of these Casimirs can be used to extend the bilinear Poisson bracket to a trilinear generalized Nambu bracket. It is further shown that the equations governing dissipative RBC can be written as the superposition of the conservative Nambu bracket with a dissipative symmetric bracket. This leads to a Nambu-metriplectic system, which completes the geometrical picture of RBC. (fast track communication)

  1. Theoretical and Experimental Studies of Magneto-Rayleigh-Taylor Instabilities

    International Nuclear Information System (INIS)

    Lau, Yue Ying; Gilgenbach, Ronald

    2013-01-01

    Magneto-Rayleigh-Taylor instability (MRT) is important to magnetized target fusion, wire-array z-pinches, and equation-of-state studies using flyer plates or isentropic compression. It is also important to the study of the crab nebula. The investigators performed MRT experiments on thin foils, driven by the mega-ampere linear transformer driver (LTD) facility completed in their laboratory. This is the first 1-MA LTD in the USA. Initial experiments on the seeding of MRT were performed. Also completed was an analytic study of MRT for a finite plasma slab with arbitrary magnetic fields tangential to the interfaces. The effects of magnetic shear and feedthrough were analyzed

  2. Theoretical and Experimental Studies of Magneto-Rayleigh-Taylor Instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Yue Ying [University of Michigan, Ann Arbor, MI (United States); Gilgenbach, Ronald [University of Michigan, Ann Arbor, MI (United States)

    2013-07-07

    Magneto-Rayleigh-Taylor instability (MRT) is important to magnetized target fusion, wire-array z-pinches, and equation-of-state studies using flyer plates or isentropic compression. It is also important to the study of the crab nebula. The investigators performed MRT experiments on thin foils, driven by the mega-ampere linear transformer driver (LTD) facility completed in their laboratory. This is the first 1-MA LTD in the USA. Initial experiments on the seeding of MRT were performed. Also completed was an analytic study of MRT for a finite plasma slab with arbitrary magnetic fields tangential to the interfaces. The effects of magnetic shear and feedthrough were analyzed.

  3. Operation and maintenance of the RA reactor, RA Research reactor. Annual report 1976

    International Nuclear Information System (INIS)

    Martinc, R.

    1976-12-01

    During 1976 the Ra reactor was operating for about 30% shorter period than usual. The reason were extraordinary repair activities within regular and investment maintenance as well as repair of failures caused by neglected maintenance during previous 6 years. Delay was caused by unavailability of fuel (2% enriched fuel elements are spent) and the new 80% enriched fuel demanded experimental and theoretical analyses before being introduced into the core. Safety analyses concerned with using 80% enriched fuel both experimental and theoretical were successfully fulfilled. The December 1976 successful experimental campaign can be marked as end of the 17 years period of using 2% enriched fuel and start of the new period of using highly enriched fuel. This is significant not only for the reactor itself but for the users, because it would result in increase of neutron flux by 50% with the increase of costs by only 4%. Demand was submitted for obtaining the final license for transition operating regime with highly enriched fuel which would save at least 2 200 000 dinars. This will enable reactor operation in 1977 and later on, without interruption by 'critical' and other experiments related to new highly enriched fuel. A high number of repair and other urgent activities were fulfilled in order to enable safe operation. Some of these activities were done never before and some were neglected during past 6 years. The most important tasks were: purchase of Al tubes made of special alloy, fabrication and mounting of the fuel channel; overall investigation of reactor vessel leakage; repair of the heavy water pump; exchange of two vertical channels. basic equipment for construction of emergency cooling system was purchased. Hot cells are equipped for independent utilisation [sr

  4. Productivity loss due to absenteeism and presenteeism by different instruments in patients with RA and subjects without RA

    NARCIS (Netherlands)

    Braakman-Jansen, Louise Marie Antoinette; Kuper, Ina H.; van de Laar, Mart A F J; Taal, Erik

    2012-01-01

    Objectives. To explore the impact of at-work productivity loss on the total productivity cost by different instruments in patients recently diagnosed with RA and controls without RA. Methods. Cross-sectional data were collected from outpatients with RA between December 2007 and February 2008. The

  5. Irradiation of an uranium silicide prototype in RA-3 reactor

    International Nuclear Information System (INIS)

    Calabrese, R.; Estrik, G.; Notari, C.

    1996-01-01

    The factibility of irradiation of an uranium silicide (U 3 Si 2 ) prototype in the RA-3 reactor was studied. The standard RA-3 fuel element uses U 3 O 8 as fissible material. The enrichment of both standard and prototype is the same: 20% U 235 and also the frame geometry and number of plates is identical. The differences are in the plate dimensions and the fissile content which is higher in the prototype. The cooling conditions of the core allow the insertion of the prototype in any core position, even near the water trap, if the overall power is kept below 5Mw. Nevertheless, the recommendation was to begin irradiation near the periphery and later on move the prototype towards more central positions in order to increase the burnup rate. The prototype was effectively introduced in a peripheral position and the thermal fluxes were measured between plates with the foil activation technique. These were also evaluated with the fuel management codes and a reasonable agreement was found. (author). 5 refs., 3 figs., 3 tabs

  6. Migration of 226 Ra, 228 Ra, 210 Pb, U and Th from phosphogypsum

    International Nuclear Information System (INIS)

    Silva, Nivaldo Carlos da; Cipriani, Moacir; Taddei, Maria Helena T.

    2002-01-01

    The physico-chemical availability of radioactive elements ( 210 Pb, 226 Ra, 228 Ra, Th and U) in Brazilian phosphogypsum was investigated in a large scale leaching experiment carried out in lysimeters, using phosphogypsum samples (approximately 1.2 tons) from two phosphoric acid industries. Lysimeters were built using cylindrical concrete containers with 0.9 m inner diameter and 2 m depth. The bottom of the lysimeter was filled with a 10 cm layer of gravel covered with geomembrane sheet. Under this layer a pipe was designed to drain the percolated water. Three lysimeters were filled with phosphogypsum from each industry and a mixture of both. As percolated water comes exclusively from the rain, sample was collected daily when available. Samples were then pooled weekly, carefully prepared and submitted to radiochemical analysis. Radiochemical characterization of phosphogypsum and percolated water was performed by radiochemical separation followed by gross alpha and beta counting ( 226 Ra, 228 Ra and 210 Pb) and UV-Vis spectrophotometry with Arsenazo III (U and Th). This experiment was carried out from 12/01/1999 to 01/22/2001, with a precipitation of 2,732 mm. It was observed that approximately 40% (534 L) of the rain fall percolated through the lysimeter 1. The analysis of 22 samples of percolated water from lysimeter 1 showed mean radionuclides activities of 70±30 mBqL -1 , 70±50 mBqL -1 , 100±60 mBqL -1 and 110±55 mBqL -1 for U, 226 Ra, 228 Ra and 210 Pb, respectively. Thorium activities were below detection limit. (author)

  7. Performance analysis of LoRa radio for an indoor IoT applications

    NARCIS (Netherlands)

    Ayele, Eyuel D.; Hakkenberg, Chiel; Meijers, Jan Pieter; Zhang, Kyle; Meratnia, Nirvana; Havinga, Paul J.M.

    2017-01-01

    LoRa is an emerging wireless standard specifically designed for Low Power Wide Area Networks (LPWANs). It provides long range, low data rate, and energy efficient wireless communication and is believed to have high potential for realization of a large number of Internet of Things (IoT) applications.

  8. Instructions for RA reactor decontamination - Annex 10; Prilog 10 - Uputstvo za dekontaminaciju Reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1963-12-15

    Instructions for RA reactor decontamination includes: action plan for decontamination of the heavy water system by 7% water solution of H{sub 3}PO{sub 4} + 2% CrO{sub 3} acid; description of the preparatory work including calculation of the pipes volume and installation of special pipes; detailed instructions for decontamination procedure. [Serbo-Croat] Uputstvo za dekontaminaciju Reaktora RA sadrzi: plan operacija za dekontaminaciju sistema teske vode 7% vodenim rastvorom kiseline H{sub 3}PO{sub 4} + 2% CrO{sub 3}; opis pripremnih radova ukljucujuci proracun zapremine covovoda i montiranje posebnih cevovoda; detaljno uputstvo za izvodjenje operacija pri dekontaminaciji.

  9. Radiation protection at the RA Reactor in 1993, RA research reactor, Part

    International Nuclear Information System (INIS)

    Ninkovic, M.; Pavlovic, R.; Mandic, M.; Sipka, V.; Grsic, Z.

    1993-01-01

    Radiation protection tasks which enable safe operation of the RA reactor, and are defined according the the legal regulations and IAEA safety recommendations are sorted into four categories in this report: (1) Control of the working environment, dosimetry and radiation protection at the RA reactor; (2) decontamination, collecting and treatment of fluid effluents and solid wastes; (3) Radioactivity control in the vicinity of the reactor and (4)meteorology measurements; (3). Each of the category is described as a separate annex of this report [sr

  10. Ra-226 bioaccumulation and growth indices in fish.

    Science.gov (United States)

    Shi, Xiaopei; Smith, Richard; Seymour, Colin; Mothersill, Carmel

    2017-06-01

    To determine the accumulated activity of Ra-226 in fathead minnows fed with environmentally relevant levels of Ra-226 for 5 months in water at 20 °C, and to evaluate the influence of this level of Ra-226 on the growth of fathead minnows. Fathead minnows were fed with fish food containing 10-10,000 mBq/g Ra-226 for 5 months. At the end of the experiment, the fish were sacrificed, flash frozen in liquid nitrogen and kept at -20 °C. Longitudinal sections of 40 μm thickness were cut at the middle of the fish body using a cryostat. The activity of Ra-226 in each section was determined using autoradiography with a nuclear track detector CR-39. According to the weight and the width of the fish, the activity of Ra-226 in the whole fish body could be estimated. In addition, the length and the weight of the fish were measured and the condition factor was calculated to evaluate the growth and fitness of the fish. There is a positive but non-linear relationship between the accumulated activity of Ra-226 in fish body and the concentration of Ra-226 in fish food. The highest activity of Ra-226 accumulated in fish body was found from fish fed with 10,000 mBq/g Ra-226 food. This was calculated as 256.4 ± 49.1 mBq/g, p fish fed with food containing lower concentration of Ra-226 (up to 1000 mBq/g), the bioaccumulation of Ra-226 in the body saturated. The Ra-226 concentration factor (CF) for fish was inversely proportional to the Ra-226 activity in food, and the highest CF value was 2.489, obtained from the lowest dietary Ra-226 activity (10 mBq/g). In addition, condition factors (K) of fish in all Ra-226-treated groups were significantly lower than those of the controls. The results show that the bioaccumulation of Ra-226 in fish is not simply related to the dietary Ra-226 activity, and has a saturation value when the dietary activity is low. In addition, the environmental level of Ra-226 in the fish food has a small adverse effect on the growth and fitness of fathead

  11. Rayleigh-Taylor mixing with time-dependent acceleration

    Science.gov (United States)

    Abarzhi, Snezhana

    2016-10-01

    We extend the momentum model to describe Rayleigh-Taylor (RT) mixing driven by a time-dependent acceleration. The acceleration is a power-law function of time, similarly to astrophysical and plasma fusion applications. In RT flow the dynamics of a fluid parcel is driven by a balance per unit mass of the rates of momentum gain and loss. We find analytical solutions in the cases of balanced and imbalanced gains and losses, and identify their dependence on the acceleration exponent. The existence is shown of two typical regimes of self-similar RT mixing-acceleration-driven Rayleigh-Taylor-type and dissipation-driven Richtymer-Meshkov-type with the latter being in general non-universal. Possible scenarios are proposed for transitions from the balanced dynamics to the imbalanced self-similar dynamics. Scaling and correlations properties of RT mixing are studied on the basis of dimensional analysis. Departures are outlined of RT dynamics with time-dependent acceleration from canonical cases of homogeneous turbulence as well as blast waves with first and second kind self-similarity. The work is supported by the US National Science Foundation.

  12. Rayleigh-Taylor mixing with space-dependent acceleration

    Science.gov (United States)

    Abarzhi, Snezhana

    2016-11-01

    We extend the momentum model to describe Rayleigh-Taylor (RT) mixing driven by a space-dependent acceleration. The acceleration is a power-law function of space coordinate, similarly to astrophysical and plasma fusion applications. In RT flow the dynamics of a fluid parcel is driven by a balance per unit mass of the rates of momentum gain and loss. We find analytical solutions in the cases of balanced and imbalanced gains and losses, and identify their dependence on the acceleration exponent. The existence is shown of two typical sub-regimes of self-similar RT mixing - the acceleration-driven Rayleigh-Taylor-type mixing and dissipation-driven Richtymer-Meshkov-type mixing with the latter being in general non-universal. Possible scenarios are proposed for transitions from the balanced dynamics to the imbalanced self-similar dynamics. Scaling and correlations properties of RT mixing are studied on the basis of dimensional analysis. Departures are outlined of RT dynamics with space-dependent acceleration from canonical cases of homogeneous turbulence as well as blast waves with first and second kind self-similarity. The work is supported by the US National Science Foundation.

  13. Development of Rayleigh Doppler lidar for measuring middle atmosphere winds

    Science.gov (United States)

    Raghunath, K.; Patra, A. K.; Narayana Rao, D.

    Interpretation of most of the middle and upper atmospheric dynamical and chemical data relies on the climatological description of the wind field Rayleigh Doppler lidar is one instrument which monitors wind profiles continuously though continuity is limited to clear meteorological conditions in the middle atmosphere A Doppler wind lidar operating in incoherent mode gives excellent wind and temperature information at these altitudes with necessary spectral sensitivity It observes atmospheric winds by measuring the spectral shift of the scattered light due to the motions of atmospheric molecules with background winds and temperature by spectral broadening The presentation is about the design and development of Incoherent Doppler lidar to obtain wind information in the height regions of 30-65 km The paper analyses and describes various types of techniques that can be adopted viz Edge technique and Fringe Imaging technique The paper brings out the scientific objectives configuration simulations error sources and technical challenges involved in the development of Rayleigh Doppler lidar The presentation also gives a novel technique for calibrating the lidar

  14. Subsonic leaky Rayleigh waves at liquid-solid interfaces.

    Science.gov (United States)

    Mozhaev, V G; Weihnacht, M

    2002-05-01

    The paper is devoted to the study of leaky Rayleigh waves at liquid-solid interfaces close to the border of the existence domain of these modes. The real and complex roots of the secular equation are computed for interface waves at the boundary between water and a binary isotropic alloy of gold and silver with continuously variable composition. The change of composition of the alloy allows one to cross a critical velocity for the existence of leaky waves. It is shown that, contrary to popular opinion, the critical velocity does not coincide with the phase velocity of bulk waves in liquid. The true threshold velocity is found to be smaller, the correction being of about 1.45%. Attention is also drawn to the fact that using the real part of the complex phase velocity as a velocity of leaky waves gives only approximate value. The most interesting feature of the waves under consideration is the presence of energy leakage in the subsonic range of the phase velocities where, at first glance, any radiation by harmonic waves is not permitted. A simple physical explanation of this radiation with due regard for inhomogeneity of radiated and radiating waves is given. The controversial question of the existence of leaky Rayleigh waves at a water/ice interface is reexamined. It is shown that the solution considered previously as a leaky wave is in fact the solution of the bulk-wave-reflection problem for inhomogeneous waves.

  15. Nonlinear interaction of Rayleigh--Taylor and shear instabilities

    International Nuclear Information System (INIS)

    Finn, J.M.

    1993-01-01

    Results on the nonlinear behavior of the Rayleigh--Taylor instability and consequent development of shear flow by the shear instability [Phys. Fluids B 4, 488 (1992)] are presented. It is found that the shear flow is generated at sufficient amplitude to reduce greatly the convective transport. For high viscosity, the time-asymptotic state consists of an equilibrium with shear flow and vortex flow (with islands, or ''cat's eyes''), or a relaxation oscillation involving an interplay between the shear instability and the Rayleigh--Taylor instability in the presence of shear. For low viscosity, the dominant feature is a high-frequency nonlinear standing wave consisting of convective vortices localized near the top and bottom boundaries. The localization of these vortices is due to the smaller shear near the boundary regions. The convective transport is largest around these convective vortices near the boundary and there is a region of good confinement near the center. The possible relevance of this behavior to the H mode and edge-localized modes (ELM's) in the tokamak edge region is discussed

  16. Rayleigh-Taylor instability under curved substrates: An optimal transient growth analysis

    Science.gov (United States)

    Balestra, Gioele; Brun, P.-T.; Gallaire, François

    2016-12-01

    We investigate the stability of thin viscous films coated on the inside of a horizontal cylindrical substrate. In such a case, gravity acts both as a stabilizing force through the progressive drainage of the film and as a destabilizing force prone to form droplets via the Rayleigh-Taylor instability. The drainage solution, derived from lubrication equations, is found asymptotically stable with respect to infinitesimally small perturbations, although in reality, droplets often form. To resolve this paradox, we perform an optimal transient growth analysis for the first-order perturbations of the liquid's interface, generalizing the results of Trinh et al. [Phys. Fluids 26, 051704 (2014), 10.1063/1.4876476]. We find that the system displays a linear transient growth potential that gives rise to two different scenarios depending on the value of the Bond number (prescribing the relative importance of gravity and surface tension forces). At low Bond numbers, the optimal perturbation of the interface does not generate droplets. In contrast, for higher Bond numbers, perturbations on the upper hemicircle yield gains large enough to potentially form droplets. The gain increases exponentially with the Bond number. In particular, depending on the amplitude of the initial perturbation, we find a critical Bond number above which the short-time linear growth is sufficient to trigger the nonlinear effects required to form dripping droplets. We conclude that the transition to droplets detaching from the substrate is noise and perturbation dependent.

  17. Macrodistribution of 226Ra in the human skeleton as determined in vitro by gamma-ray spectrometry

    International Nuclear Information System (INIS)

    Essling, M.A.; Huff, D.R.

    1976-01-01

    A large number of γ-ray measurements of 226 Ra in human bone has been made both at MIT and CHR-ANL. These data are analyzed for correlations of the specific activity ratio of a bone group with other parameters, an interlaboratory comparison of the measurements, and an estimate of the errors expected when a whole-body content is calculated from the 226 Ra determination on a partial skeleton

  18. Ra-226 concentrations in the Lower Weser region in the vicinity of a pollution source

    International Nuclear Information System (INIS)

    Lauer, R.

    1981-01-01

    Near Nordenham at the lower Weser Ra-containing waste water is discharged from a fertilizer factory. The measurements are restricted to Ra-analysis and the Ra in fish, sediment, and river water samples (Ra-226). (DG) [de

  19. Age-related and 224Ra-induced abnormalities in the teeth of male mice

    International Nuclear Information System (INIS)

    Humphreys, E.R.; Stones, V.A.

    1985-01-01

    A high incidence of incisor abnormalities was found in aged control and aged 224 Ra-treated male CBA mice. Visual examination of the abnormalities in both controls and treated mice revealed extreme shortening of the upper incisors and hypoplastic, grooved or undulating enamel. The administration of 865 or 1730 nCi of 224 Ra hastened the onset of incisor abnormalities although no specific feature was attributable solely to radium toxicity. Radiography and histology revealed corrugated incisors, obliteration of the pulp cavity, extension and disorganized growth of incisors basally, secondary incisors, open pulp and fractures within the alveoli. There was a statistically-significant reduction in the number of molars present in animals given 432, 865 or 1730 nCi 224 Ra. (author)

  20. From Leonardo to the graser: light scattering in historical perspective. Pt. 5. The fourth Baron Rayleigh

    Energy Technology Data Exchange (ETDEWEB)

    Hey, J D

    1986-07-01

    The optical research of Robert John Strutt, fourth Baron Rayleigh, on the transparency of the terrestrial atmosphere as determined by the distribution of ozone, is reviewed in relation to the studies of Hartley, Cornu, Fabry and Buisson, and Fowler on this subject. It is shown that the basis of Rayleigh's work is now incorporated in the modern optical techniques for atmospheric monitoring.

  1. Dynamics of globular molecules: moisture effect on the Rayleigh scattering spectrum of the Moessbauer radiation

    International Nuclear Information System (INIS)

    Chesskaya, T.Yu.

    1998-01-01

    The Rayleigh scattering spectrum of the Moessbauer radiation is plotted on the model simulating globular macromolecules. The modeling results are compared with experimental data on the spectra of the Rayleigh scattering of the Moessbauer radiation for various moisture content and hydratation dependence of the elastic scattering portion

  2. Design of fuel element for RA10

    International Nuclear Information System (INIS)

    Estevez, Esteban A.; Markiewicz, Mario; Gerding, Roberto

    2012-01-01

    The RA-10 reactor is an open pool multipurpose reactor. It is intended for radioisotopes production, fuel irradiation and use of neutron beam experiments. The nominal configuration core consists of 19 fuel elements (FE) and 6 in-core irradiation positions. With regard to the FE, although both conceptual design and manufacturing technology are similar to the already developed and qualified by CNEA (MTR fuel flat plate), the conditions imposed by the new reactor on FE's are more demanding that previous supplies. Here it should be mentioned the magnitude of the hydrodynamic forces acting on the FE caused by coolant flow through the core (upward) and mainly by the high coolant velocity between fuel plates (greater than 5 times than those currently in operation). Moreover, the high power density results in higher heat flux in fuel plates and greater temperature gradient. As a result of these increased demands present during irradiation, and in order to maintain a high level of reliability, it is necessary carry out some modifications in the mechanical design of the FE (with respect to the so-called ECBE design or s tandard ) . Design verification is performed through analytical and code calculations, and hydrodynamic tests on a full-scale prototype. This article describes the design of the FE for RA 10 reactor, with special emphasis on those aspects that represent innovations in the traditional design (ECBE). It also presents the functional requirements, design criteria and design limits established according to the reactor operational states (author)

  3. High-Speed RaPToRS

    Science.gov (United States)

    Henchen, Robert; Esham, Benjamin; Becker, William; Pogozelski, Edward; Padalino, Stephen; Sangster, Thomas; Glebov, Vladimir

    2008-11-01

    The High-Speed Rapid Pneumatic Transport of Radioactive Samples (HS-RaPToRS) system, designed to quickly and safely move radioactive materials, was assembled and tested at the Mercury facility of the Naval Research Laboratory (NRL) in Washington D.C. A sample, which is placed inside a four-inch-diameter carrier, is activated before being transported through a PVC tube via airflow. The carrier travels from the reaction chamber to the end station where it pneumatically brakes prior to the gate. A magnetic latch releases the gate when the carrier arrives and comes to rest. The airflow, optical carrier-monitoring devices, and end gate are controlled manually or automatically with LabView software. The installation and testing of the RaPToRS system at NRL was successfully completed with transport times of less than 3 seconds. The speed of the carrier averaged 16 m/s. Prospective facilities for similar systems include the Laboratory for Laser Energetics and the National Ignition Facility.

  4. Alpha-particle doses to human organs and tissues from internally-deposited 226Ra and 228Ra

    International Nuclear Information System (INIS)

    Keane, A.T.; Schlenker, R.A.

    1981-01-01

    Estimation of radiation doses to the soft tissues from internally-deposited 226 Ra and 228 Ra is relevant to an investigation of soft-tissue malignancies in radium-exposed persons being conducted at the Center for Human Radiobiology. Alpha-particle doses in a 50-year period following a single injection of 226 Ra or 228 Ra are presented for 31 soft tissues and organs of the adult human. The dose estimates were derived from the ICRP alkaline earth model fitted to data on retention of 226 Ra in soft tissues and bone, combined with reported ratios of 226 Ra to Ca in soft tissue and bone at natural levels and the distribution of Ca in the tissues of Reference Man (ICRP23). The median of the 31 organ and tissue doses from the α-particles of 226 Ra itself is 0.08 rad per injected μCi. An additional average dose of 0.01 rad per μCi 226 Ra daughter products produced in soft tissue or transferred from bone to soft tissue. Soft-tissue doses from α-particles of the 228 Ra decay series are about six times those from 226 Ra α-particles for equal injected activities of 228 Ra and 226 Ra, with the assumption that 228 Ra daughter products do not transfer from the organ in which they are produced. The 50-year dose to the red marrow of bone from α-particles originating in bone is 0.55 rad per μCi 226 Ra injected and 1.0 rad per μCi 228 Ra injected. For ingestion by dial painters of luminous compound containg 226 Ra or 228 Ra with a daughter-to-parent activity ratio of 0.5, the dose to the mucosal alyer of the lower large intestine from α-particles originating in the gut contents is about 0.1 rad per μCi systemic intake of 226 Ra or 228 Ra

  5. RA reactor operation and maintenance, Annual report 1974

    International Nuclear Information System (INIS)

    Milosevic, D. et al

    1974-12-01

    During 1974, RA reactor was operated at nominal power for 194 days and 13 days at lower power levels. The total production was 30711 MWh which is 2.4% higher than planned. Practically there were no discrepancies from the plan. The reactor was used for irradiation and experiments according to the demand of 437 users. This report contains detailed data about reactor power and experiments performed in 1974. Total number of afety shutdowns was 11, of which 8 were caused by power cuts, and 3 due to human error. Maximum individual personnel exposure dose was 50% of the maximum permissible dose. There were no accidents during this year. Decontamination of surfaces was less than during previous years. About 805 m 2 of surfaces and 178 objects were decontaminated. It was concluded that the successful operation in 1974 has a special significance taking into account the financial problems [sr

  6. Analysis of RA-8 critical facility core in some configurations

    International Nuclear Information System (INIS)

    Abbate, Maximo J.; Sbaffoni, Maria M.

    2000-01-01

    The RA-8 critical facility was designated and built to be used in the experimental plan of the 'CAREM' Project but is, in itself, very versatile and adequate to perform many types of other experiments. The present paper includes calculated estimates of some critical configurations and comparisons with experimental results obtained during its start up. Results for Core 1 with homogeneous arrangement of rods containing 1.8 % enriched uranium, showed very good agreement. In fact, an experimentally critical configuration was reached with 1.300 rods and calculated values were: 1.310 using the WIMS code and 1.148 from the CONDOR code. Moreover, it was verified that the estimated number of 3.4% enriched uranium rods to be fabricated is enough to build a heterogeneous core or even a homogeneous core with this enrichment. The replacement of 3.4 % enriched uranium by 3.6 % will not present problems related with the original plan. (author)

  7. IoT devices and applications based on LoRa/LoRaWAN

    CSIR Research Space (South Africa)

    Khutsoane, Oratile C

    2017-10-01

    Full Text Available such as smart water management systems. However, they require high energy-efficient sensor nodes that are able to communicate across long distance. This motivates the development of many Low-Power Wide Area Networks (LPWAN) technologies, such as LoRa, to fulfill...

  8. Research nuclear reactor RA - Annual report 1992; Istrazivacki nuklearni reaktor RA - Izvestaj za 1992. godinu

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1992-12-01

    Research reactor RA Annual report for year 1992 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection. First part includes 8 annexes describing reactor operation, activities of services for maintenance of reactor components and instrumentation, financial report and staffing. Second annex B is a paper by Z. Vukadin 'Recurrence formulas for evaluating expansion series of depletion functions' published in 'Kerntechnik' 56, (1991) No.6 (INIS record no. 23024136. Second part of the report is devoted to radiation protection issues and contains 4 annexes with data about radiation control of the working environment and reactor environment, description of decontamination activities, collection of radioactive wastes, and meteorology data. [Serbo-Croat] Godisnji izvestaj o radu nuklearnog reaktora RA za 1992. godinu sastoji se od dva dela: prvi deo obuhvata pogon i odzavanje reaktora RA, a drugi poslove zastite od zracenja na reaktoru RA. Prvi deo sadrzi 8 priloga, koji opisuju rad reaktora i poslove sluzbi za odrzavanje opreme i komponenti, finansijski izvestaj, kadrovsku strukturu osoblja reaktora. Drugi prilog (B) je rad Z. Vukadina 'Recurrence formulas for evaluating expansion series of depletion functions' objavljen u casopisu Kerntechnik, 1991. Drugi deo izvestaja o poslovima zastite od zracenja sadrzi 4 priloga sa podacima radijacione kontrole radne sredine i okoline reaktora, opis poslova dekontaminacije i sakupljanja radioaktivnih materija, kao i meteoroloske podatke.

  9. RA-0 reactor. New neutronic calculations; Reactor RA-0. Nuevos calculos neutronicos

    Energy Technology Data Exchange (ETDEWEB)

    Rumis, D; Leszczynski, F

    1991-12-31

    An updating of the neutronic calculations performed at the RA-0 reactor, located at the Natural, Physical and Exact Sciences Faculty of Cordoba National University, are herein described. The techniques used for the calculation of a reactor like the RA-0 allows prediction in detail of the flux behaviour in the core`s interior and in the reflector, which will be helpful for experiments design. In particular, the use of WIMSD4 code to make calculations on the reactor implies a novelty in the possible applications of this code to solve the problems that arise in practice. (Author). [Espanol] En este trabajo se actualizan los calculos neutronicos realizados para el reactor RA-0, instalado en la Facultad de Ciencias Exactas, Fisicas y Naturales de la Universidad Nacional de Cordoba. Se describen los calculos realizados hasta la fecha y los resultados obtenidos. Las tecnicas incorporadas al calculo de un reactor como el RA-0 permiten predecir en detalle el comportamiento del flujo en el interior del nucleo y en el reflector, lo que sera una importante ayuda en el diseno de experimentos. En particular, el empleo del codigo WIMSD4 para calculos del reactor completo constituye una novedad en las posibles aplicaciones de ese codigo para resolver problemas que se presentan en la practica. (Autor).

  10. Investigation of floor Nusselt number in floor heating system for insulated ceiling conditions

    International Nuclear Information System (INIS)

    Karadag, Refet; Teke, Ismail

    2007-01-01

    In this study, in a floor heated room, natural convection heat transfer over the floor is analysed numerically for different thermal conditions. An equation relevant to Nusselt number over the floor has been obtained by using the numerical data. Different equations are given in the literature. They consider the effect of floor Rayleigh number while neglecting the effect of wall and ceiling thermal conditions. Numerical data obtained in this study show that the Nusselt number over the floor depends on not only the floor Rayleigh number but also the wall Rayleigh number (for insulated ceiling conditions). The equations given in the literature are different from each other due to their not considering the effect of wall and ceiling Rayleigh numbers. This difference between the equations may be eliminated by obtaining an equation containing the effect of floor, wall and ceiling Rayleigh numbers. In this new approach, an equation relevant to the floor Nusselt number that depends on the floor and wall Rayleigh numbers has been obtained in the floor heating system for insulated ceiling conditions. The equation obtained in this study has been compared with the equations given in the literature. It has been seen that the equation obtained in this study matches the numerical values under more extensive thermal conditions than the equations given in the literature. The maximum deviation for the equations given in the literature is 35%, but in the current study, the maximum deviation has been found to be 10%. As a result, it is more convenient to use the equation found in the new approach as a function of Rayleigh number over the floor and wall for insulated ceiling conditions

  11. Research nuclear reactor RA - Annual Report 1996; Istrazivacki nuklearni reaktor RA - Izvestaj za 1996. godinu

    Energy Technology Data Exchange (ETDEWEB)

    Sotic, O [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1996-12-01

    Activities related to revitalisation of the RA reactor started in 1986, were continued in 1996. All the planned actions related to renewal of the reactor components were finished. The last, and at the same time most important action, related to exchange of complete reactor instrumentation is underway, delayed. The delivery of components from USSR is late. Production of this instruments is financed by the IAEA according to the contract signed in December 1988 with Russian Atomenergoexport. According to this contract, it has been planned that the RA reactor instrumentation should be delivered to the Vinca Institute by the end of 1990. Only 80% of the instrumentation was delivered until September 1991. Since then any delivery of components to Yugoslavia was stopped because of the temporary embargo imposed by the IAEA. The existing RA reactor instrumentation was dismantled. Control and maintenance of the reactor components was done regularly and efficiently. Fuel inspection by the IAEA safeguards inspectors was done on a monthly basis. There have been on the average 43 employees at the RA reactor which is considered sufficient for maintenance and repair conditions. The problem of financing the reactor activities and maintenance remains unsolved. Research reactor RA Annual report for year 1996 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection. [Serbo-Croat] U toku 1996. godine nastavljeni su poslovi na revitalizaciji reaktora RA, zapocetoj 1986. godine. Okoncan je niz zahvata na opremi postrojenja kojima ce se u narednom periodu omoguciti kontinualan i pouzdan rad ovog reaktora. Poslednji, i ujedno najveci zahvat, koji se odnosi na zamenu celokupne instrumentacije kasni zbog zastoja u isporuci opreme koja se izradjuje u Sovjetskom savezu. Izradu ove opreme finansira Medjunarodna agencija za atomsku energiju kroz ugovor sklopljen decembra 1988. godine sa moskovskom firmom Atomenergoexport. Prema tom

  12. Behavior and distribution of 226Ra and 228Ra in the east coast of Peninsular Malaysia marine environment

    International Nuclear Information System (INIS)

    Nurrul Assyikeen Mohd Jaffary; Zal Uyun Wan Mahmood; Zaharudin Ahmad; Yii, Mei Wo; Kamarozaman Ishak

    2010-01-01

    The present distributions of 226 Ra, 228 Ra and activity ratios of 228 Ra/ 226 Ra covering the east coast of Peninsular Malaysia were studied. Sediment core samples were collected at 10 identified stations with the thickness of water column between 14 - 72 m depth during the cruise conducted in 2008. Activity concentrations of 226 Ra and 228 Ra in sediment cores of the studied area were in the range of 18.95 ±4.25 Bq/ kg to 46.48 ± 6.41 Bq/ kg dry wt. and 35.50 ± 7.50 Bq/ kg to 77.10 ±11.37 Bq/ kg dry wt., respectively. Meanwhile, the calculated activity ratios of 228 Ra/ 226 Ra were varied mostly 1.48 to 2.24. The finding showed that there has relationships between 226 Ra, 228 Ra and oceanographic parameters which are can be attributed for better understanding of its transport processes and behavior in the east coast of Peninsular Malaysia marine environment. (author)

  13. Earth's core formation due to the Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Ida, S.; Nakagawa, Y.; Nakazawa, K.

    1987-01-01

    A protoearth accretion stage configuration consisting of an undifferentiated solid core, an intermediate metal-melt layer, and an outer silicate-melt layer, is presently taken as the initial state in an investigation of Rayleigh-Taylor instability-induced core formation. The Ida et al. (to be published) quantitative results on the instability in a self-gravitating fluid sphere are used. The instability is found to occur through the translational mode on a time-scale of about 10 hr, in the case where the metal-melt layer is greater than about 1 km; this implies that the earth's core formed due to the undifferentiated solid core's translation upon the outer layer's melting. Differentiation would then have occurred in the late accretion stage. 17 references

  14. Relationship between ultrasonic Rayleigh waves and surface residual stress

    International Nuclear Information System (INIS)

    Adler, L.; Cook, K.V.; Dewey, B.R.; King, R.T.

    1977-01-01

    Local variations of Rayleigh (surface) circumferential ultrasonic wave velocity near a pipe-girth weld in large-diameter thin-wall type 316H stainless steel pipe were measured. The weldment was similar to those anticipated for the Liquid Metal Fast Breeder Reactor (LMFBR) piping systems. The residual stress distribution was estimated independently from shell theory for an elastic, infinite, thin shell with circumferential line loading. An upper bound on the magnitude of the residual stresses was estimated assuming the deformation of the shell was entirely elastic. The pattern of surface wave velocity variations matches the theoretical residual stress pattern closely. It is suggested that the monitoring of surface wave velocity variations might be used for characterizing residual stress patterns near critical welds in piping, aiding in design calculations, and for in-service monitoring of the state of stress of weldments

  15. Rayleigh Instability-Assisted Satellite Droplets Elimination in Inkjet Printing.

    Science.gov (United States)

    Yang, Qiang; Li, Huizeng; Li, Mingzhu; Li, Yanan; Chen, Shuoran; Bao, Bin; Song, Yanlin

    2017-11-29

    Elimination of satellite droplets in inkjet printing has long been desired for high-resolution and precision printing of functional materials and tissues. Generally, the strategy to suppress satellite droplets is to control ink properties, such as viscosity or surface tension, to assist ink filaments in retracting into one drop. However, this strategy brings new restrictions to the ink, such as ink viscosity, surface tension, and concentration. Here, we report an alternative strategy that the satellite droplets are eliminated by enhancing Rayleigh instability of filament at the break point to accelerate pinch-off of the droplet from the nozzle. A superhydrophobic and ultralow adhesive nozzle with cone morphology exhibits the capability to eliminate satellite droplets by cutting the ink filament at breakup point effectively. As a result, the nozzles with different sizes (10-80 μm) are able to print more inks (1 printing electronics and biotechnologies.

  16. Numerical simulation of anisotropic preheating ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Wang Lifeng; Ye Wenhua; Li Yingjun

    2010-01-01

    The linear growth rate of the anisotropic preheating ablative Rayleigh-Taylor instability (ARTI) is studied by numerical simulations. The preheating model κ(T)=κ SH [1+f(T)] is applied, where f(T) is the preheating function interpreting the preheating tongue effect in the cold plasma ahead of the ablative front. An arbitrary coefficient D is introduced in the energy equation to study the influence of transverse thermal conductivity on the growth of the ARTI. We find that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. Numerical simulations exhibit a significant stabilization of the ablation front by improving the transverse thermal conduction. Our results are in general agreement with the theory analysis and numerical simulations by Masse. (authors)

  17. Observation of Rayleigh - Taylor growth to short wavelengths on Nike

    International Nuclear Information System (INIS)

    Pawley, C.J.; Bodner, S.E.; Dahlburg, J.P.; Obenschain, S.P.; Schmitt, A.J.; Sethian, J.D.; Sullivan, C.A.; Gardner, J.H.; Aglitskiy, Y.; Chan, Y.; Lehecka, T.

    1999-01-01

    The uniform and smooth focal profile of the Nike KrF laser [S. Obenschain et al., Phys. Plasmas 3, 2098 (1996)] was used to ablatively accelerate 40 μm thick polystyrene planar targets with pulse shaping to minimize shock heating of the compressed material. The foils had imposed small-amplitude sinusoidal wave perturbations of 60, 30, 20, and 12.5 μm wavelength. The shortest wavelength is near the ablative stabilization cutoff for Rayleigh - Taylor growth. Modification of the saturated wave structure due to random laser imprint was observed. Excellent agreement was found between the two-dimensional simulations and experimental data for most cases where the laser imprint was not dominant. copyright 1999 American Institute of Physics

  18. The Magnetic Rayleigh-Taylor Instability in Astrophysical Discs

    Science.gov (United States)

    Contopoulos, I.; Kazanas, D.; Papadopoulos, D. B.

    2016-01-01

    This is our first study of the magnetic Rayleigh-Taylor instability at the inner edge of an astrophysical disc around a central back hole. We derive the equations governing small-amplitude oscillations in general relativistic ideal magnetodydrodynamics and obtain a criterion for the onset of the instability. We suggest that static disc configurations where magnetic field is held by the disc material are unstable around a Schwarzschild black hole. On the other hand, we find that such configurations are stabilized by the space-time rotation around a Kerr black hole. We obtain a crude estimate of the maximum amount of poloidal magnetic flux that can be accumulated around the centre, and suggest that it is proportional to the black hole spin. Finally, we discuss the astrophysical implications of our result for the theoretical and observational estimations of the black hole jet power.

  19. Stability of a short Rayleigh length laser resonator

    Directory of Open Access Journals (Sweden)

    P. P. Crooker

    2005-04-01

    Full Text Available Motivated by the prospect of constructing a short Rayleigh length free-electron laser in a high-vibration environment, we demonstrate the use of a collection of rays to study the effect of mirror vibration and distortion on the behavior of the fundamental optical mode of a cold-cavity resonator. We find that the ray collection accurately describes both on-axis and off-axis optical beams. We show that a tilt or transverse shift of a mirror causes the optical mode to rock about the original resonator axis, while a longitudinal mirror shift or a change in the mirror’s radius of curvature causes the beam diameter at a mirror to successively dilate and contract on the mirror. Results are in excellent agreement with analytic calculations and wave front propagation simulations as long as the mirrors remain large with respect to the beam diameter.

  20. Front propagation in Rayleigh-Taylor systems with reaction

    International Nuclear Information System (INIS)

    Scagliarini, A; Biferale, L; Sbragaglia, M; Mantovani, F; Pivanti, M; Schifano, S F; Tripiccione, R; Pozzati, F; Toschi, F

    2011-01-01

    A special feature of Rayleigh-Taylor systems with chemical reactions is the competition between turbulent mixing and the 'burning processes', which leads to a highly non-trivial dynamics. We studied the problem performing high resolution numerical simulations of a 2d system, using a thermal lattice Boltzmann (LB) model. We spanned the various regimes emerging at changing the relative chemical/turbulent time scales, from slow to fast reaction; in the former case we found numerical evidence of an enhancement of the front propagation speed (with respect to the laminar case), providing a phenomenological argument to explain the observed behaviour. When the reaction is very fast, instead, the formation of sharp fronts separating patches of pure phases, leads to an increase of intermittency in the small scale statistics of the temperature field.

  1. IL-1Ra: its role in rheumatoid arthritis

    Directory of Open Access Journals (Sweden)

    M. Cutolo

    2011-09-01

    Full Text Available Interleukin-1 (IL-1 is one of the pivotal cytokines in initiating and driving the processes of rheumatoid arthritis (RA, and the body’s natural response, IL-1 receptor antagonist (IL-1Ra, has been shown conclusively to block its effects. IL-1 mediate several clinical symptoms of the inflammatory reaction (i.e. fever, pain, sleep disturbances. IL-1 is considered a key mediator in RA joint damage because of its greater capacity (greater than TNF of increasing matrix degradation by inducing the production of MMPs and PGE2 in synovial cells, as well by its role as mediator of bone and cartilage destruction. In addition, IL-1 decreases the repair process by suppressing matrix synthesis and shows a strong synergism with TNF in inducing many inflammatory genes at both local and systemic level. The induced endogenous production of IL-1Ra, in presence of the RA synovitis, is too low to contrast the high affinity of IL-1 for the cell receptors. Therefore, IL-1Ra presence should result in very effective prevention of IL-1 signal transduction particularly in the inflammatory site. In laboratory and animal studies inhibition of IL-1 by either antibodies to IL-1 or IL-1Ra proved beneficial to the outcome. IL-1Ra is a member of the IL-1 superfamily. The effects of different DMARDs on IL-1Ra levels in RA patients support the important role that selected anticytokine treatments might exert in the pathophysiology of the disease. However, since anti TNFα therapy it is not effective in all RA patients, nor does it fully control the arthritic process in affected joints of good responders and complete TNF suppression should be avoided, the combined treatment with intermediate doses of TNF and IL-1 blockers, reaching synergistic suppression of arthritis, seems warranted in RA.

  2. Radon emanometric technique for 226Ra estimation

    International Nuclear Information System (INIS)

    Mandakini Maharana; Sengupta, D.; Eappen, K.P.

    2010-01-01

    Studies on natural background radiation show that the major contribution of radiation dose received by population is through inhalation pathway vis-a-vis contribution from radon ( 222 Rn) gas. The immediate parent of radon being radium ( 226 Ra), it is imperative that radium content is measured in the various matrices that are present in the environment. Among the various methods available for the measurement of radium, gamma spectrometry and radiochemical method are the two extensively used measurement methods. In comparison with these two methods, the radon emanometric technique, described here, is a simple and convenient method. The paper gives details of sample processing, radon bubbler, Lucas cell and the methodology used in the emanometric method. Comparison of emanometric method with gamma spectrometry has also undertaken and the results for a few soil samples are given. The results show a fairly good agreement among the two methods. (author)

  3. Research nuclear reactor RA - Annual report 1992

    International Nuclear Information System (INIS)

    Sotic, O.

    1992-12-01

    Research reactor RA Annual report for year 1992 is divided into two main parts to cover: (1) operation and maintenance and (2) activities related to radiation protection. First part includes 8 annexes describing reactor operation, activities of services for maintenance of reactor components and instrumentation, financial report and staffing. Second annex B is a paper by Z. Vukadin 'Recurrence formulas for evaluating expansion series of depletion functions' published in 'Kerntechnik' 56, (1991) No.6 (INIS record no. 23024136. Second part of the report is devoted to radiation protection issues and contains 4 annexes with data about radiation control of the working environment and reactor environment, description of decontamination activities, collection of radioactive wastes, and meteorology data [sr

  4. RA research reactor - potentials and prospective

    International Nuclear Information System (INIS)

    Sotic, O.

    1984-01-01

    Since December 1959, the RA reactor was operated successfully, except for a few shorter periods needed for maintenance and a four longer shutdown periods caused by decrease in the heavy water quality. Accordingly, reconstruction of some reactor systems was started at the beginning of this decad, as well as increase of its experimental potential which would enable its efficient reliable operation in the future period. Reconstruction is concerned with emergency core cooling system, special ventilation system, and modernization of the reactor instrumentation. Improvement of the experimental potential is related to modifications of the neutron scattering instruments. Development of methods for isotope production is described as well. Design of the reactor experimental loop with external cooling system will be of significant importance in improvement of reactor potential in the future

  5. Measurements of multipolarities in 225Ra

    International Nuclear Information System (INIS)

    Andersen, E.; Nyboe, K.; Thorsteinsen, T.F.; Gietz, H.; Kaffrell, N.; Mattsson, S.; Nyman, G.

    1989-01-01

    Multipolarities of 45 transitions in 225 Ra have been established by investigating the radiations associated with the β - decay of 225 Fr. The study includes β - , e - and γ-singles spectra, e - γ- and γγ-coincidence measurements. The conversion electrons were measured with a mini-orange electron spectrometer, and the γ-spectra with Ge detectors. The multipolarities obtained from the measured conversion coefficients support the assignments of spin-parity doublets thus giving evidence for a stable octupole deformation of this nucleus. The negative parity of the 394.2 keV level established in the present work indicates that this level is a candidate for the parity-doublet partner of the 5/2 + state at 236.3 keV. (orig.)

  6. RaPToRS Sample Delivery System

    Science.gov (United States)

    Henchen, Robert; Shibata, Kye; Krieger, Michael; Pogozelski, Edward; Padalino, Stephen; Glebov, Vladimir; Sangster, Craig

    2010-11-01

    At various labs (NIF, LLE, NRL), activated material samples are used to measure reaction properties. The Rapid Pneumatic Transport of Radioactive Samples (RaPToRS) system quickly and safely moves these radioactive samples through a closed PVC tube via airflow. The carrier travels from the reaction chamber to the control and analysis station, pneumatically braking at the outlet. A reversible multiplexer routes samples from various locations near the shot chamber to the analysis station. Also, the multiplexer allows users to remotely load unactivated samples without manually approaching the reaction chamber. All elements of the system (pneumatic drivers, flow control valves, optical position sensors, multiplexers, Geiger counters, and release gates at the analysis station) can be controlled manually or automatically using a custom LabVIEW interface. A prototype is currently operating at NRL in Washington DC. Prospective facilities for Raptors systems include LLE and NIF.

  7. Unstable Titan-generated Rayleigh-Taylor Lakes Impact Ice

    Science.gov (United States)

    Umurhan, O. M.; Korycansky, D. G.; Zahnle, K. J.

    2014-12-01

    The evolution of surface morphology on Titan, Triton, and other worlds is strongly influenced by the interplay of various fluid dynamical processes. Specifically, overturning instabilities can easily arise due to the special circumstances of landform evolution that probably occurred on these worlds. On Titan, large impacts that formed basins like Menrva crater (and possibly Hotei Regio) would have generated impact-melt ice lakes unstably arranged over less dense ice. Cantaloupe terrains, for example as seen on Triton, may be the result of condensation of volatiles (methane, nitrogen) leading to unstably stratified layers of different compositions and densities. In each of these cases, Rayleigh-Taylor instabilities leading to large scale diapirism may be at play. In addition to the dynamics of these instabilities, other physical effects (e.g. heat diffusion, freezing/melting, porosity, temperature dependent viscosity) likely play an important role in the evolution of these features. In this ongoing study, we examine the properties of unstably stratified fluids in which the lower less-dense ice has a temperature dependent viscosity. Surprisingly, we find that there exists an optimal disturbance length scale corresponding to the fastest growth of the Rayleigh-Taylor instability. For unstably stratified layers of water (low viscosity heavy liquid lying above an ice whose viscosity increases with depth) the fastest growing mode corresponds to 40-60 km scales with overturn times of approximately 100 days. We present a detailed numerical stability analysis in a corresponding Boussinessq model (in the creeping flow limit) incorporating thermal conduction and latent heat release and we examine the stability properties surveying a variety of parameters. We have also developed a two-dimensional numerical code (a hybrid spectral/compact-differencing scheme) to model the evolution of such systems for which we shall present preliminary numerical results depicting the outcome of

  8. Generation of Rayleigh waves into mortar and concrete samples.

    Science.gov (United States)

    Piwakowski, B; Fnine, Abdelilah; Goueygou, M; Buyle-Bodin, F

    2004-04-01

    The paper deals with a non-destructive method for characterizing the degraded cover of concrete structures using high-frequency ultrasound. In a preliminary study, the authors emphasized on the interest of using higher frequency Rayleigh waves (within the 0.2-1 MHz frequency band) for on-site inspection of concrete structures with subsurface damage. The present study represents a continuation of the previous work and aims at optimizing the generation and reception of Rayleigh waves into mortar and concrete be means of wedge transducers. This is performed experimentally by checking the influence of the wedge material and coupling agent on the surface wave parameters. The selection of the best combination wedge/coupling is performed by searching separately for the best wedge material and the best coupling material. Three wedge materials and five coupling agents were tested. For each setup the five parameters obtained from the surface wave measurement i.e. the frequency band, the maximal available central frequency, the group velocity error and its standard deviation and finally the error in velocity dispersion characteristic were investigated and classed as a function of the wedge material and the coupling agent. The selection criteria were chosen so as to minimize the absorption of both materials, the randomness of measurements and the systematic error of the group velocity and of dispersion characteristic. Among the three tested wedge materials, Teflon was found to be the best. The investigation on the coupling agent shows that the gel type materials are the best solutions. The "thick" materials displaying higher viscosity were found as the worst. The results show also that the use of a thin plastic film combined with the coupling agent even increases the bandwidth and decreases the uncertainty of measurements.

  9. Experimental investigation of turbulent mixing by Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Youngs, D.L.

    1992-01-01

    A key feature of compressible turbulent mixing is the generation of vorticity via the ∇px ∇(1/ρ) term. This source of vorticity is also present in incompressible flows involving the mixing of fluids of different density, for example Rayleigh-Taylor unstable flows. This paper gives a summary of an experimental investigation of turbulent mixing at a plane boundary between two fluids, of densities ρ 1 , and ρ 2 . (ρ 1 > ρ 2 ) due to Rayleigh-Taylor instability. The two fluids are near incompressible and mixing occurs when an approximately constant acceleration, g, is applied normal to the interface with direction from fluid 2 to fluid 1. Full details of the experimental programme are given in a set of three reports. Some of the earlier experiments are also described by Read. Previous experimental work and much of the theoretical research has concentrated on studying the growth of the instability from a single wavelength perturbation rather than turbulent mixing. Notable exceptions are published in the Russian literature. A related process, turbulent mixing induced by the passage of shock waves though an interface between fluids of different density is described by Andronov et al. The major purpose of the experiments described here was to study the evolution of the instability from small random perturbations where it is found that large and larger structures appear as time proceeds. A novel technique was used to provide the desired acceleration. The two fluids were enclosed in a rectangular tank, the lighter fluid 2 initially resting on top of the denser fluid 1. One or more rocket motors were then used to drive the tank vertically downwards. The aim of the experimental programme is to provide data for the calibration of a turbulence model used to predict mixing in real situations

  10. Disassembling and modification of RA-3

    International Nuclear Information System (INIS)

    Tarizzo, R.D.

    1990-01-01

    The objective of this paper is to describe the partial disassembling and modification of RA-3, called the Modernization Project. It comprises all the technical and administrative steps directly related with this task. The improvement of RA-3 is a result of the lack of 90% enriched uranium obliging a change over to 20% enriched uranium. This brought about design modifications both in fuel elements and the reactor. The presentation of documents for the licensing authority as well as are detailed separately. The modernization project was divided in 25 tasks: 1) changing fuel element support table, 2) changing heat exchanger, 3) repairing of cooling towers, 4) repairing of primary circuit valves, 5) repairing of irradiation channels, 6) construction of a new sampler, 7) changing tangential channel, 8) cleaning and disassembling of reactor (inside), 9) changing continuous demineralizer (ion exchange column), 10) detection of failure in fuel elements, 11) modification of nuclear instrumentation, 12) modification of conventional instrumentation, 13) modification of electrical system, 14) changing telemanipulators, 15) construction of mechanism bridge, 16) changing a primary circuit valve when the heat exchanger is changed too, 17) painting ground floor, hall floor, and pump room floor with epoxy resin levelling, 18) installation of fire alarm system, 19) radioactive liquid discharge, 20) modification of secondary circuit (This task involves: a) installation of a third secondary pump, b) extension of this piping, c) installation of two 12 inch valves to the present cooling towers pools independent, d) installation of filtering system), 21) optimization hot water bed, 22) changing detector support table, 23) removal, decontamination and reinstallation of shielding, 25) changing pneumatic system

  11. Influence of relativistic effects on hydrolysis of Ra2+

    International Nuclear Information System (INIS)

    Zielinska, B.; Bilewicz, A.

    2005-01-01

    Using 224 Ra radiotracer the first hydrolysis constant (pK 1h ) of Ra 2+ cations has been determined. The pK 1h value of Ra 2+ was compared with the pK 1h values of other Group 2 cations. It has been shown that the electrostatic hydrolysis model based on assumption that pK 1h is a linear function of reciprocal ionic radii (1/r i ) does not describe well the hydrolysis of Group 2 metal cations. The reason of higher Ra 2+ hydrolysis as expected is the influence of relativistic effects on bonding 7s and 7p 1/2 orbitals. (author)

  12. Research on background neutron of 226Ra γ source

    International Nuclear Information System (INIS)

    Ji Changsong

    1996-01-01

    This work studies the background neutron emission of 226 Ra γ source: the mechanism of resulting in background neutron is studied; a thesis that the (α, n) type reaction on Radium carriers Cl or Br is the main source of creating background neutron emission of 226 Ra γ source has been proposed and certificated; a proposal of substitution of Cl carrier by Br in radium source produced in China in order to reduce background neutron emission is put forward. A result to reduce the background neutron from 96.4 neutrons/4πsmgRa to 6.1 neutrons/4πsmgRa is obtained

  13. Cardiovascular safety of biologic therapies for the treatment of RA.

    Science.gov (United States)

    Greenberg, Jeffrey D; Furer, Victoria; Farkouh, Michael E

    2011-11-15

    Cardiovascular disease represents a major source of extra-articular comorbidity in patients with rheumatoid arthritis (RA). A combination of traditional cardiovascular risk factors and RA-related factors accounts for the excess risk in RA. Among RA-related factors, chronic systemic inflammation has been implicated in the pathogenesis and progression of atherosclerosis. A growing body of evidence--mainly derived from observational databases and registries--suggests that specific RA therapies, including methotrexate and anti-TNF biologic agents, can reduce the risk of future cardiovascular events in patients with RA. The cardiovascular profile of other biologic therapies for the treatment of RA has not been adequately studied, including of investigational drugs that improve systemic inflammation but alter traditional cardiovascular risk factors. In the absence of large clinical trials adequately powered to detect differences in cardiovascular events between biologic drugs in RA, deriving firm conclusions on cardiovascular safety is challenging. Nevertheless, observational research using large registries has emerged as a promising approach to study the cardiovascular risk of emerging RA biologic therapies.

  14. Modeling the Energy Performance of LoRaWAN

    OpenAIRE

    Casals, Lluís; Mir, Bernat; Vidal, Rafael; Gomez, Carles

    2017-01-01

    LoRaWAN is a flagship Low-Power Wide Area Network (LPWAN) technology that has highly attracted much attention from the community in recent years. Many LoRaWAN end-devices, such as sensors or actuators, are expected not to be powered by the electricity grid; therefore, it is crucial to investigate the energy consumption of LoRaWAN. However, published works have only focused on this topic to a limited extent. In this paper, we present analytical models that allow the characterization of LoRaWAN...

  15. RA Reactor operation and maintenance (I-IX), Part IV, Task 3.08/04, Refurbishment of the RA reactor; Pogon i odrzavanje reaktora RA (I-IX), IV Deo, Zadatak 3.08/04 Remont reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    Zecevic, V [Institute of Nuclear Sciences Boris Kidric, Reaktor RA, Vinca, Beograd (Serbia and Montenegro)

    1963-12-15

    This volume contains reports describing maintenance and repair work of the RA reactor instrumentation, equipment of the reactor dosimetry control system, and equipment for regulation and control systems.

  16. Concentration of natural radionuclides (40K, 228Ra and 226Ra) in vegetables and fruits collected around Kudankulam, South India

    International Nuclear Information System (INIS)

    Mahiban Ross, E.; Feroz Khan, M.; Lenin Raj, Y.; Godwin Wesley, S.; Kumar, M.; Sundar Rajan, P.

    2007-01-01

    Baseline activity concentration of the natural radio nuclides 40 K, 228 Ra and 226 Ra in vegetables and fruits was determined around Kudankulam. In many of the samples, 228 Ra and 226 Ra was below minimum detection limit. 40 K was found to be more in leafy vegetables followed by pods, tubers and fleshy fruits. The highest accumulator among the matrices was the leafy vegetables with the geometric mean of 189.47 Bq.kg -1 fresh for vegetables and fruits with the geometric mean of 128.95 Bq.kg -1 fresh. 228 Ra activity in vegetables and fruits ranged from 0.074 to 1.153 and 0.074 to 0.131 Bq.kg -l fresh respectively. 226 Ra in vegetables and fruits ranged from BDL to 0.07 and BDL-.044 Bq.kg -l fresh respectively. 40 K in vegetables and fruits followed a log normal distribution. (author)

  17. Analysis of recovery efficiency in high-temperature aquifer thermal energy storage: a Rayleigh-based method

    Science.gov (United States)

    Schout, Gilian; Drijver, Benno; Gutierrez-Neri, Mariene; Schotting, Ruud

    2014-01-01

    High-temperature aquifer thermal energy storage (HT-ATES) is an important technique for energy conservation. A controlling factor for the economic feasibility of HT-ATES is the recovery efficiency. Due to the effects of density-driven flow (free convection), HT-ATES systems applied in permeable aquifers typically have lower recovery efficiencies than conventional (low-temperature) ATES systems. For a reliable estimation of the recovery efficiency it is, therefore, important to take the effect of density-driven flow into account. A numerical evaluation of the prime factors influencing the recovery efficiency of HT-ATES systems is presented. Sensitivity runs evaluating the effects of aquifer properties, as well as operational variables, were performed to deduce the most important factors that control the recovery efficiency. A correlation was found between the dimensionless Rayleigh number (a measure of the relative strength of free convection) and the calculated recovery efficiencies. Based on a modified Rayleigh number, two simple analytical solutions are proposed to calculate the recovery efficiency, each one covering a different range of aquifer thicknesses. The analytical solutions accurately reproduce all numerically modeled scenarios with an average error of less than 3 %. The proposed method can be of practical use when considering or designing an HT-ATES system.

  18. RA Research nuclear reactor - Annual report 1987; Istrazivacki nuklearni reaktor RA - Izvestaj o radu za 1987. godinu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1987-12-15

    Annual report concerning the project 'RA research nuclear reactor' for 1987, financed by the Serbian ministry of science is divided into two parts. First part is concerned with RA reactor operation and maintenance, which is the task of the Division for reactor engineering of the Institute for multidisciplinary studies and RA reactor engineering. Second part deals with radiation protection activities at the RA reactor which is the responsibility of the Institute for radiation protection. Scientific council of the Institute for multidisciplinary studies and RA reactor engineering has stated that this report describes adequately the activity and tasks fulfilled at the RA reactor in 1989. The scope and the quality of the work done were considered successful both concerning the maintenance and reconstruction, as well as radiation protection activities. [Serbo-Croat] Godisnji izvestaj po projektu 'Istrazivacki nuklearni reaktor RA' za 1987. godinu, koji finansira republicka zajednica za nauku SR Srbije po ugovoru br. 3509/1 sastoji se iz dva dela. Prvi deo obuhvata pogon i odrzavanje nuklearnog reaktora RA, sto predstavlja obavezu Odeljenja za reaktorski inzenjering u sastavu OOUR Instituta za multidisciplinarna istrazivanja i inzenjering RA. Drugi deo obuhvata poslove zastite od zracenja na reaktoru RA, sto predstavlja obavezu OOUR Instituta za zastitu od zracenja 'Zastita'. Naucno vece Instituta za multidisciplinarna istrazivanja i inzenjjring RA ocenilo je da sadrzina ovog izvestaja odgovara izvrsenim poslovima na reaktoru RA u 1989. godini. Pozitivno se ocenjuje obim i kvalitet izvrsenih radova kako u pogledu odrzavanja i rekonstrukcije reaktora, tako i u pogledu poslova zastite od zracenja izvrsenih kod njega.

  19. Transfer of 226Ra, 228Ra, 210Pb and 210Po in aquatic organisms and food chain

    International Nuclear Information System (INIS)

    Yang Xiaotong; Weng Detong; Chen Wenyin; Chen Xiuyun; Chen Jixi; Zhao Shimin

    1998-01-01

    Objective: To find out the transfer regularities of 226 Ra, 228 Ra, 210 Pb and 210 Po, which are natural radionuclides in the aquatic organisms and food chain. Methods: Large amount of breed of representative aquatic products and their living waters and sediments were collected and treated according to routine experimental procedures. The contents of 226 Ra, 228 Ra, 210 Pb and 210 Po were detected in each sample. Measured data were analyzed statistically and pairwise comparisons were made to determine the differences between groups. Results: 226 Ra, 228 Ra and 210 Pb were mainly deposited in the bones (or shells), their concentration factors (CF) ranged from 10 2 to 10 3 ; the CF ranged only from 10 0 to 10 2 in the flesh. 210 Po was mainly deposited in the soft tissues, CF ranged from 10 2 to 10 4 ; especially in the stomachs and intestines of fishes, the value reached 10 4 . The cooking process did not impinge significantly on the transfer of 226 Ra, 228 Ra and 210 Pb in the food chain (P>0.05), but did significantly influence the transfer of 210 Po, especially in the freshwater fishes and shrimps. Paired comparison test of the activities between raw flesh and cooked flesh showed very significant difference (P 226 Ra, 228 Ra, 210 Pb and 210 Po. Even though the bones (or shells) of aquatic organisms contained relatively higher levels of 226 Ra, 228 Ra and 210 Pb, the cooking process does not significantly increase the radioactive contents in the foodstuffs. However, the cooking process does significantly influence the transfer of 210 Po. It does significantly increase the content of 210 Po in foodstuffs

  20. Doses from 222Rn, 226Ra, and 228Ra in groundwater from Guarani aquifer, South America.

    Science.gov (United States)

    Bonotto, D M

    2004-01-01

    Groundwater samples were analysed for 222Rn, 226Ra, and 228Ra in Guarani aquifer spreading around 1 million km2 within four countries in South America, and it was found that their activity concentrations are lognormally distributed. Population-weighted average activity concentration for these radionuclides allowed to estimate a value either slightly higher (0.13 mSv/year) than 0.1 mSv for the total effective dose or two times higher (0.21 mSv/year) than this limit, depending on the choice of the dose conversion factor. Such calculation adds useful information for the appropriate management of this transboundary aquifer that is socially and economically very important to about 15 million inhabitants living in Brazil, Argentina, Uruguay and Paraguay.

  1. Doses from 222Rn, 226Ra, and 228Ra in groundwater from Guarani aquifer, South America

    International Nuclear Information System (INIS)

    Bonotto, D.M.

    2004-01-01

    Groundwater samples were analysed for 222 Rn, 226 Ra, and 228 Ra in Guarani aquifer spreading around 1 million km 2 within four countries in South America, and it was found that their activity concentrations are lognormally distributed. Population-weighted average activity concentration for these radionuclides allowed to estimate a value either slightly higher (0.13 mSv/year) than 0.1 mSv for the total effective dose or two times higher (0.21 mSv/year) than this limit, depending on the choice of the dose conversion factor. Such calculation adds useful information for the appropriate management of this transboundary aquifer that is socially and economically very important to about 15 million inhabitants living in Brazil, Argentina, Uruguay and Paraguay

  2. Separation of Ra/Ca by ion exchange; Separacion de Ra/Ca por intercambio ionico

    Energy Technology Data Exchange (ETDEWEB)

    Iturbe, J L; Jimenez R, M; Flores M, J

    1991-04-15

    The radium and the calcium belong to the same group in the periodic classification and as consequence both they present very similar chemical properties, that makes difficult its separation. Both elements are also frequently associate in the nature, the calcium is very abundant, the radium is not it and for that reason it is indispensable its separation to analyze to this last one. The alpha spectroscopy is very appropriate to analyze to the {sup 226} Ra, however to achieve a good resolution of the spectra, the samples should contain small quantities of calcium. The purposes of this work were to know the chromatographic behavior of the alkaline-earthy cations: calcium, barium and radium and to apply these knowledge to the separation of the {sup 226} Ra and its analysis by means of alpha spectroscopy. (Author)

  3. RA Research reactor, Part 1, Operation and maintenance of the RA nuclear reactor for 1986

    International Nuclear Information System (INIS)

    Sotic, O.; Martinc, R.; Cupac, S.; Sulem, B.; Badrljica, R.; Majstorovic, D.; Sanovic, V.

    1986-01-01

    In order to enable future reliable operation of the RA reactor, according to new licensing regulations, three major tasks started in 1984 were fulfilled: building of the new emergency system, reconstruction of the existing ventilation system, and reconstruction of the power supply system. Simultaneously in 1985/1986 renewal of the instrumentation and reconstruction of the system for handling and storage of the spent fuel in the reactor building have started. Design projects for these tasks are almost finished and the reconstruction of both systems is expected to be finished until 1988 and mid 1989 respectively. RA reactor Safety report was finished according to the recommendations of the IAEA. Investments in 1986 were used for 8000 kg of heavy water, maintenance of reactor systems and supply of new components, reconstruction of reactor systems. This report includes 8 annexes concerning reactor operation, activities of services and financial issues [sr

  4. Diagrams about RA reactor operation, Annex 7; Prilog 7 - Rad reaktora RA po godinama - dijagrami

    Energy Technology Data Exchange (ETDEWEB)

    Martinc, R [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1976-01-15

    This Annex 7 includes diagrams about RA reactor operation (MWh) from 1960-1975; mean values of reactor power per day and month in 1975, and percent of utilisation of experimental space during 1975. [Serbo-Croat] Ovaj prilog sadrzi dijagrame o radu reaktora (MWh) po godinama (1960-1975); srednje vrednosti dnevne snage reaktora u 1975. godini; rad reakrora (MWh) po mesecima u 1975; procenat iskoriscenja eksperimentalnog prostora u 1975. godini.

  5. RA Reactor operation and maintenance (I-IX), Part IV, Task 3.08/04, Refurbishment of the RA reactor

    International Nuclear Information System (INIS)

    Zecevic, V.

    1963-12-01

    This volume contains reports describing maintenance and repair work of the RA reactor instrumentation, equipment of the reactor dosimetry control system, and equipment for regulation and control systems

  6. Determination of the four natural Ra isotopes in thermal waters by gamma-ray spectrometry

    International Nuclear Information System (INIS)

    Condomines, M.; Rihs, S.; Lloret, E.; Seidel, J.L.

    2010-01-01

    Our method for the simultaneous determination of the four natural Ra isotopes ( 226 Ra, 228 Ra, 224 Ra and 223 Ra) in thermal waters involves a separation of Ra on a selective filter (3 M EMPORE TM Radium Rad disk), and a single counting using a broad-energy HPGe detector (BE Ge manufactured by CANBERRA TM ). The calculation of 223 Ra and 228 Ra activities requires interference and cascade summing corrections. The 226 Ra activities in CO 2 -rich thermal waters of the Lodeve Basin (South of France) range from 530 to 2240 mBq/l. The low ( 228 Ra/ 226 Ra) activity ratios (0.19-0.29) suggest that Ra is mostly derived from the aquifer carbonates. The short-lived 224 Ra and 223 Ra are probably added to the water through recoil or desorption processes from Th-enriched coatings on the fracture walls.

  7. Determination of 226Ra and 224Ra in sediments samples by liquid scintillation counting

    International Nuclear Information System (INIS)

    Villa, M.; Moreno, H.P.; Manjon, G.

    2005-01-01

    An experimental procedure has been developed for a rapid determination of the activity concentration of 226 Ra and 224 Ra in sediments by liquid scintillation counting. The importance of the method lies in its application to the measurement of sediments where the Ra-isotopes activity concentration has been increased due to an anthropomorphic enhancement based on releases of naturally occurring radioactive material (NORM). A sample pre-treatment, including a digestion with aqua regia and a precipitation of hydroxides, was applied to samples before the radium extraction, which was made by co-precipitation with barium. Measurements were done in a low background scintillation spectrometer Quantulus 1220, which can separate and detect simultaneously α and β particles. Additionally, some improvements are suggested for a better α and β interference correction of the results. The obtaining of radiochemical yields is also improved using 133 Ba as tracer, which decays by emission of conversion electrons and γ-rays; the wide range of radiochemical yields obtained confirms the need of this analyses. The procedure has been applied to the measurement of riverbed sediments from an estuary in the south-west of Spain, affected in the past by direct and indirect phosphogypsum discharges

  8. RA Research nuclear reactor, Part I - RA nuclear reactor operation, maintenance and utilization in 1983

    International Nuclear Information System (INIS)

    Sotic, O.; Martinc, R.; Kozomara-Maic, S.; Cupac, S.; Raickovic, N.; Radivojevic, J.; Badrljica, R.; Majstorovic, D.; Sanovic, V.

    1983-12-01

    After regular shutdown in November 1982, inspection of the fuel elements from the RA reactor core which was done from December 1982 - February 1983 has shown that there are deposits of aluminium oxides on the surface of the fuel cladding. After restart The RA reactor was operated at power levels from 1.8 - 2 MW, with 80% enriched uranium dioxide fuel elements. It was found that there was no corrosion of the fuel element cladding and that it was not possible to find the cause of surface deposition on the cladding surfaces without further operation. It was decided to purify the heavy water permanently during operation and to increase the heavy water flow by operating two pumps. This procedure was adopted in order to decrease the possibility of corrosion. The Safety committee of the Institute has approved this procedure for operating the RA reactor in 1983. The core was made of 80% enriched fuel, critical experiments were done until June 1983, and after that the operation was continued at power levels up to 2 MW [sr

  9. On Rayleigh waves in a thinly layered laminated thermoelastic medium with stress couples under initial stresses

    Directory of Open Access Journals (Sweden)

    Pijush Pal Roy

    1988-01-01

    Full Text Available A study is made of the propagation of Rayleigh waves in a thinly layered laminated thermoelastic medium under deviatoric, hydrostatic, and couple stresses. The frequency equation of the Rayleigh waves is obtained. The phase velocity of the Rayleigh waves depends on the initial stress, deviatoric stress, and the couple stress. The laminated medium is first replaced by an equivalent anisotropic thermoelastic continuum. The corresponding thermoelastic coefficients (after deformation are derived in terms of initially isotropic thermoelastic coefficients (before deformation of individual layers. Several particular cases are discussed for the determination of the displacement fields with or without the effect of the couple stress.

  10. Quantum effects on the Rayleigh-Taylor instability in a horizontal inhomogeneous rotating plasma

    International Nuclear Information System (INIS)

    Hoshoudy, G. A.

    2009-01-01

    The Rayleigh-Taylor instability is studied analytically in inhomogeneous plasma rotating uniformly in an external transverse magnetic field. The influence of the quantum mechanism is considered. For a stratified layer the linear growth rate is obtained. Some special cases that isolate the effect of various parameters on the growth rate of the Rayleigh-Taylor instability are discussed. It is shown that for some cases, the presence of the external transverse magnetic field beside the quantum effect will bring about more stability on the Rayleigh-Taylor instability.

  11. Effect of FLR correction on Rayleigh -Taylor instability of quantum and stratified plasma

    International Nuclear Information System (INIS)

    Sharma, P.K.; Tiwari, Anita; Argal, Shraddha; Chhajlani, R.K.

    2013-01-01

    The Rayleigh Taylor instability of stratified incompressible fluids is studied in presence of FLR Correction and quantum effects in bounded medium. The Quantum magneto hydrodynamic equations of the problem are solved by using normal mode analysis method. A dispersion relation is carried out for the case where plasma is bounded by two rigid planes z = 0 and z = h. The dispersion relation is obtained in dimensionless form to discuss the growth rate of Rayleigh Taylor instability in presence of FLR Correction and quantum effects. The stabilizing or destabilizing behavior of quantum effect and FLR correction on the Rayleigh Taylor instability is analyzed. (author)

  12. A Numerical Model for Prediction of Residual Stress Using Rayleigh Waves

    International Nuclear Information System (INIS)

    Yuan, Mao Dan; Kang, To; Kim, Hak Joon; Song, Sung Jin

    2011-01-01

    In this work, a numerical model is proposed for the relation between the magnitudes and the depth residual stress with the velocity of Rayleigh wave. Three cases, stress-free, uniform stress and layered stress, are investigated for the change tendency of the Rayleigh wave speed. Using the simulated signal with variation of residual stress magnitude and depth, investigation of the parameters for fitting residual stress and velocity change are performed. The speed change of Rayleigh wave shows a linear relation with the magnitude and an exponential relation with the depth of residual stress. The combination of these two effects could be used for the depth profile evaluation of the residual stress

  13. Radiation protection at the RA Reactor in 1986, Part -2, Annex 2a, Radioactivity control of the RA reactor environment (atmospheric precipitations, dust, water, soil, plants, fruit...)

    International Nuclear Information System (INIS)

    Ajdacic, N.; Martic, M.; Jovanovic, J.

    1986-01-01

    Control of radioactivity in the biosphere in the vicinity of the RA reactor is part of the radioactivity control done regularly for the whole territory of the Vinca institute (report by the same authors included in this Annex). During 1986 control was conducted according to the plan until May 1, 1986 when a dramatic increase of the precipitations and all other samples from the biosphere was recorded. According to the measured data no significant changes have been found in the surroundings of the RA reactor, until April 29 1986. Since then more detailed control was conducted, the number of samples was increased, apart from standard measuring procedure of total beta activity measurements, gamma spectrometry of all samples was applied. High activity level of the following nuclides was found: Iodine, cerium,cesium, tellurium, ruthenium, barium, lanthanum, etc. As an example activity of ?1?3?1 I in one sample was 564±5 kBq/m 2 [sr

  14. RA reactor operation and maintenance, Annual report 1974; Pogon i odrzavanje reaktora RA - Izvestaj o radu u 1974. godini

    Energy Technology Data Exchange (ETDEWEB)

    Milosevic, D et al [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1974-12-15

    During 1974, RA reactor was operated at nominal power for 194 days and 13 days at lower power levels. The total production was 30711 MWh which is 2.4% higher than planned. Practically there were no discrepancies from the plan. The reactor was used for irradiation and experiments according to the demand of 437 users. This report contains detailed data about reactor power and experiments performed in 1974. Total number of afety shutdowns was 11, of which 8 were caused by power cuts, and 3 due to human error. Maximum individual personnel exposure dose was 50% of the maximum permissible dose. There were no accidents during this year. Decontamination of surfaces was less than during previous years. About 805 m{sup 2} of surfaces and 178 objects were decontaminated. It was concluded that the successful operation in 1974 has a special significance taking into account the financial problems. [Serbo-Croat] Reaktor RA je u 1974. godini radio na nominalnoj snazi 194 dana i 13 dana na manjim snagama. Ukupni rad iznosio je 30711 MWh odnosno 1,4% vise od planiranog. Prakticno nije bilo odstupanja od plana rada. Reaktor je koriscen za ozracivanja i eksperimente za 437 korisnika. Ovaj izvestaj sadrzi detaljne podatke o radu i eksperimentima koji su obavljani. U toku godine bilo je 11 sigurnosnih zaustavljanja, od cega 8 zbog elektricnog napona i 3 usled greske osoblja. Ukupna doza ozracivanja ljudstva bila je manja nego prethodnih godina. Maksimalna doza po oveku bila je 50% manja od maksimalno dozvoljene doze. Nije bilo ni jednog akcidenta. Dekontaminirano je znatno manje povrsina nego ranijih godina, i sakupljeno manje otpada nego prethodnih godina, dok tecnih efluenata nije bilo. Zakljuceno je da uspesan rad reaktora u 1974. godini ima poseban znacaj kada se imaju na umu problemi finansiranja reaktora.

  15. Apparatus for real-time acoustic imaging of Rayleigh-Bénard convection

    Energy Technology Data Exchange (ETDEWEB)

    Kuehn, Kerry, K.

    2008-10-28

    We have successfully designed, built and tested an experimental apparatus which is capable of providing the first real-time ultrasound images of Rayleigh-B\\'{e}nard convection in optically opaque fluids confined to large aspect ratio experimental cells. The apparatus employs a modified version of a commercially available ultrasound camera to capture images (30 frames per second) of flow patterns in a fluid undergoing Rayleigh Bénard convection. The apparatus was validated by observing convection rolls in 5cSt polydimethylsiloxane (PDMS) polymer fluid. Our first objective, after having built the apparatus, was to use it to study the sequence of transitions from diffusive to time--dependent heat transport in liquid mercury. The aim was to provide important information on pattern formation in the largely unexplored regime of very low Prandtl number fluids. Based on the theoretical stability diagram for liquid mercury, we anticipated that straight rolls should be stable over a range of Rayleigh numbers, between 1708 and approximately 1900. Though some of our power spectral densities were suggestive of the existence of weak convection, we have been unable to unambiguously visualize stable convection rolls above the theoretical onset of convection in liquid mercury. Currently, we are seeking ways to increase the sensitivity of our apparatus, such as (i) improving the acoustic impedance matching between our materials in the ultrasound path and (ii) reducing the noise level in our acoustic images due to turbulence and cavitation in the cooling fluids circulating above and below our experimental cell. If we are able to convincingly improve the sensitivity of our apparatus, and we still do not observe stable convection rolls in liquid mercury, then it may be the case that the theoretical stability diagram requires revision. In that case, either (i) straight rolls are not stable in a large aspect ratio cell at the Prandtl numbers associated with liquid mercury, or (ii

  16. Growth retardation in children injected with 224Ra

    International Nuclear Information System (INIS)

    Spiess, H.; Mays, C.W.; Spiess-Paulus, E.

    1986-01-01

    We have obtained the adult heights of 133 patients formerly injected with 224 Ra as juveniles. 224 Ra induced growth retardation was greatest in children injected at young ages and increased with dose. The growth retardation was well represented as a 2% decrease in potential growth post irradiation per 100 rads of calculated average skeletal dose. (orig.)

  17. 226Ra determination in phosphogypsum by alpha-particle spectrometry

    International Nuclear Information System (INIS)

    Aguado, J.L.; Bolivar, J.P.; Garcia-Tenorio, R.

    1999-01-01

    A radiochemical method for 226 Ra determination by alpha-particle spectrometry in environmental samples has been developed in our laboratory. The method has been validated by measurements in samples with known concentrations of this radionuclide and it has been applied in studies related to 226 Ra behaviour in phosphogypsum (the main by-product of producing phosphoric acid from phosphate rocks). (author)

  18. Rheumatoid Arthritis (RA) associated interstitial lung disease (ILD).

    LENUS (Irish Health Repository)

    O'Dwyer, David N

    2013-10-01

    Rheumatoid Arthritis (RA) is the most common Connective Tissue Disease (CTD) and represents an increasing burden on global health resources. Interstitial lung disease (ILD) has been recognised as a complication of RA but its potential for mortality and morbidity has arguably been under appreciated for decades. New studies have underscored a significant lifetime risk of ILD development in RA. Contemporary work has identified an increased risk of mortality associated with the Usual Interstitial Pneumonia (UIP) pattern which shares similarity with the most devastating of the interstitial pulmonary diseases, namely Idiopathic Pulmonary Fibrosis (IPF). In this paper, we discuss recent studies highlighting the associated increase in mortality in RA-UIP. We explore associations between radiological and histopathological features of RA-ILD and the prognostic implications of same. We emphasise the need for translational research in this area given the growing burden of RA-ILD. We highlight the importance of the respiratory physician as a key stakeholder in the multidisciplinary management of this disorder. RA-ILD focused research offers the opportunity to identify early asymptomatic disease and define the natural history of this extra articular manifestation. This may provide a unique opportunity to define key regulatory fibrotic events driving progressive disease. We also discuss some of the more challenging and novel aspects of therapy for RA-ILD.

  19. 226Ra concentrations in some Illinois well waters

    International Nuclear Information System (INIS)

    Holtzman, R.B.; Gilkeson, R.H.

    1982-01-01

    226 Ra concentrations are reported for the waters from deep wells in 43 communities in Illinois. The concentrations range from 0.08 to 20.6 pCi/L. The effectiveness of additives (nitric acid or EDTA) in keeping the 226 Ra in solution in the samples is discussed

  20. RA Reactor operation and maintenance (I-IX), Part I

    International Nuclear Information System (INIS)

    Zecevic, V.

    1963-12-01

    The report on RA reactor operation and maintenance for year 1963 is divided in six tasks. This volume contains the introductory report, and three tasks of the final report, namely reactor exploitation, reactivity changes of the RA reactor before repair, planning of refuelling

  1. The study of 226Ra concentration in Teheran's pasteurized milk

    International Nuclear Information System (INIS)

    Khademi, B.; Sekhavat, A.; Movahed Shari'atpanahi, J.

    1975-01-01

    A study of 226 88 Ra concentration in pasteurized milk distributed in Tehran during 1970-72 was accomplished. The Ash resulting from the milk was 4.5 to 5.5 gr., which might be due to poor nourishment of the animals. These results are compared with the Ra concentration in France and Puerto Rico

  2. Rayleigh scatter in kilovoltage x-ray imaging: is the independent atom approximation good enough?

    Science.gov (United States)

    Poludniowski, G.; Evans, P. M.; Webb, S.

    2009-11-01

    Monte Carlo simulation is the gold standard method for modelling scattering processes in medical x-ray imaging. General-purpose Monte Carlo codes, however, typically use the independent atom approximation (IAA). This is known to be inaccurate for Rayleigh scattering, for many materials, in the forward direction. This work addresses whether the IAA is sufficient for the typical modelling tasks in medical kilovoltage x-ray imaging. As a means of comparison, we incorporate a more realistic 'interference function' model into a custom-written Monte Carlo code. First, we conduct simulations of scatter from isolated voxels of soft tissue, adipose, cortical bone and spongiosa. Then, we simulate scatter profiles from a cylinder of water and from phantoms of a patient's head, thorax and pelvis, constructed from diagnostic-quality CT data sets. Lastly, we reconstruct CT numbers from simulated sets of projection images and investigate the quantitative effects of the approximation. We show that the IAA can produce errors of several per cent of the total scatter, across a projection image, for typical x-ray beams and patients. The errors in reconstructed CT number, however, for the phantoms simulated, were small (typically < 10 HU). The IAA can therefore be considered sufficient for the modelling of scatter correction in CT imaging. Where accurate quantitative estimates of scatter in individual projection images are required, however, the appropriate interference functions should be included.

  3. Stabilization of the Rayleigh-Taylor instability by convection in an ablatively accelerated laser plasma

    International Nuclear Information System (INIS)

    Bul'ko, A.B.; Liberman, M.A.

    1992-01-01

    The authors use the WKB-approximation to treat the problem of the stabilization by an inhomogeneous convective current of the Rayleigh-Taylor instability developing in the ablation zone when the plasma of laser targets is accelerated by ablation. The problem of the eigenvalues - the instability growth rates - is reduced to the solution of an algebraic equation with coefficients which depend on the structure of the unperturbed profiles of the hydrodynamic variables. They show for the practically important case of subsonic flow of an incompressible plasma that the instability growth rate vanishes for k = k o = max[2(g|∇lnρ|) 1/2 /v]. The condition for the self-consistency of the model is that the local Froude number be small in the region where the instability develops; however, comparison with numerical calculations shows that the model is also applicable in the case of rather steep density gradients when the Froude number is of order unity. 32 refs., 2 figs

  4. The effect of centrifugal buoyancy on the heat transport in rotating Rayleigh-Bénard convection

    Science.gov (United States)

    Horn, Susanne; Aurnou, Jonathan

    2017-11-01

    In a rapidly rotating and differentially heated fluid, the centrifugal acceleration can play a similar role to that of gravity in generating convective motion. However, in the paradigm system of rotating Rayleigh-Bénard convection, centrifugal buoyancy is typically not considered in theoretical studies and, thus, usually undesired in laboratory experiments, despite being unavoidable. How centrifugal buoyancy affects the turbulent flow, including the heat transport, is still largely unknown, in particular, when it can be considered negligible. We study this problem by means of direct numerical simulations. Unlike in experiments, we are able to systematically vary the Froude number Fr (ratio of centrifugal to gravitational acceleration) and the Rossby number Ro (dimensionless rotation rate) independently, and even set each to zero exactly. We show that the centrifugal acceleration simultaneously leads to contending phenomena, e.g. reflected by an increase and a decrease of the center temperature, or a suppression and an enhancement of the heat transfer efficiency. Which one prevails as net effect strongly depends on the combination of Fr and Ro. Furthermore, we discuss implications for experiments of rapidly rotating convection. SH acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG) under Grant HO 5890/1-1, JA by the NSF Geophysics Program.

  5. Performance and delay analysis of hybrid ARQ with incremental redundancy over double rayleigh fading channels

    KAUST Repository

    Chelli, Ali

    2014-11-01

    In this paper, we study the performance of hybrid automatic repeat request (HARQ) with incremental redundancy over double Rayleigh channels, a common model for the fading amplitude of vehicle-to-vehicle communication systems. We investigate the performance of HARQ from an information theoretic perspective. Analytical expressions are derived for the \\\\epsilon-outage capacity, the average number of transmissions, and the average transmission rate of HARQ with incremental redundancy assuming a maximum number of HARQ rounds. Moreover, we evaluate the delay experienced by Poisson arriving packets for HARQ with incremental redundancy. We provide analytical expressions for the expected waiting time, the packet\\'s sojourn time in the queue, the average consumed power, and the energy efficiency. In our study, the communication rate per HARQ round is adjusted to the average signal-to-noise ratio (SNR) such that a target outage probability is not exceeded. This setting conforms with communication systems in which a quality of service is expected regardless of the channel conditions. Our analysis underscores the importance of HARQ in improving the spectral efficiency and reliability of communication systems. We demonstrate as well that the explored HARQ scheme achieves full diversity. Additionally, we investigate the tradeoff between energy efficiency and spectral efficiency.

  6. LoRa Scalability: A Simulation Model Based on Interference Measurements

    Directory of Open Access Journals (Sweden)

    Jetmir Haxhibeqiri

    2017-05-01

    Full Text Available LoRa is a long-range, low power, low bit rate and single-hop wireless communication technology. It is intended to be used in Internet of Things (IoT applications involving battery-powered devices with low throughput requirements. A LoRaWAN network consists of multiple end nodes that communicate with one or more gateways. These gateways act like a transparent bridge towards a common network server. The amount of end devices and their throughput requirements will have an impact on the performance of the LoRaWAN network. This study investigates the scalability in terms of the number of end devices per gateway of single-gateway LoRaWAN deployments. First, we determine the intra-technology interference behavior with two physical end nodes, by checking the impact of an interfering node on a transmitting node. Measurements show that even under concurrent transmission, one of the packets can be received under certain conditions. Based on these measurements, we create a simulation model for assessing the scalability of a single gateway LoRaWAN network. We show that when the number of nodes increases up to 1000 per gateway, the losses will be up to 32%. In such a case, pure Aloha will have around 90% losses. However, when the duty cycle of the application layer becomes lower than the allowed radio duty cycle of 1%, losses will be even lower. We also show network scalability simulation results for some IoT use cases based on real data.

  7. LoRa Scalability: A Simulation Model Based on Interference Measurements.

    Science.gov (United States)

    Haxhibeqiri, Jetmir; Van den Abeele, Floris; Moerman, Ingrid; Hoebeke, Jeroen

    2017-05-23

    LoRa is a long-range, low power, low bit rate and single-hop wireless communication technology. It is intended to be used in Internet of Things (IoT) applications involving battery-powered devices with low throughput requirements. A LoRaWAN network consists of multiple end nodes that communicate with one or more gateways. These gateways act like a transparent bridge towards a common network server. The amount of end devices and their throughput requirements will have an impact on the performance of the LoRaWAN network. This study investigates the scalability in terms of the number of end devices per gateway of single-gateway LoRaWAN deployments. First, we determine the intra-technology interference behavior with two physical end nodes, by checking the impact of an interfering node on a transmitting node. Measurements show that even under concurrent transmission, one of the packets can be received under certain conditions. Based on these measurements, we create a simulation model for assessing the scalability of a single gateway LoRaWAN network. We show that when the number of nodes increases up to 1000 per gateway, the losses will be up to 32%. In such a case, pure Aloha will have around 90% losses. However, when the duty cycle of the application layer becomes lower than the allowed radio duty cycle of 1%, losses will be even lower. We also show network scalability simulation results for some IoT use cases based on real data.

  8. Reproduction of the RA reactor fuel element fabrication

    International Nuclear Information System (INIS)

    Novakovic, M.

    1961-12-01

    This document includes the following nine reports: Final report on task 08/12 - testing the Ra reactor fuel element; design concept for fabrication of RA reactor fuel element; investigation of the microstructure of the Ra reactor fuel element; Final report on task 08/13 producing binary alloys with Al, Mo, Zr, Nb and B additions; fabrication of U-Al alloy; final report on tasks 08/14 and 08/16; final report on task 08/32 diffusion bond between the fuel and the cladding of the Ra reactor fuel element; Final report on task 08/33, fabrication of the RA reactor fuel element cladding; and final report on task 08/36, diffusion of solid state metals [sr

  9. Recovery of Ra-223 from natural thorium irradiated by protons

    Energy Technology Data Exchange (ETDEWEB)

    Vasiliev, Aleksandr N.; Ostapenko, Valentina S. [Lomonosov Moscow State Univ. (Russian Federation); Russian Academy of Sciences, Moscow-Troitsk (Russian Federation). Inst. for Nuclear Research; Lapshina, Elena V.; Ermolaev, Stanislav V.; Zhuikov, Boris L. [Russian Academy of Sciences, Moscow-Troitsk (Russian Federation). Inst. for Nuclear Research; Danilov, Sergey S. [Lomonosov Moscow State Univ. (Russian Federation); Kalmykov, Stepan N. [Lomonosov Moscow State Univ. (Russian Federation); National Research Center ' Kurchatov Institute' (NRC ' Kurchatov Institute' ), Moscow (Russian Federation)

    2016-11-01

    Irradiation of natural thorium with medium-energy protons is considered to be a prospective approach to large-scale production of {sup 225}Ac and {sup 223}Ra. In addition to the earlier-developed method of {sup 225}Ac isolation, the present work focuses on the simultaneous recovery of {sup 223}Ra from the same thorium target. Radiochemical procedure is based on liquid-liquid extraction, cation exchange and extraction chromatography. The procedure provides separation of radium from spallation and fission products generated in the thorium target. High chemical yield (85-90%) and radionuclide purity of {sup 223}Ra (> 99.8% except {sup 224}Ra and {sup 225}Ra isotopes) have been achieved.

  10. THE IMMUNOLOGICAL CHARACTERISTIC OF RA PATIENTS WITH ANAEMIA

    Directory of Open Access Journals (Sweden)

    A. E. Sizikov

    2014-07-01

    Full Text Available Abstract. The aim of the investigation was to study the immunological characteristics of RA patients with anaemia. Clinical and laboratory data including the percentage of the main lymphocyte subclasses, phagocyte and DTH-effector activity, serum concentration of immunoglobulins, the percentage of cells producing IFNγ and/or IL-4 and percent of monocytes producing TNF. We revealed some significant clinical, laboratory and immunological differences between RA patients and healthy donors and between patients with and without anaemia. Our data demonstrate RA anemic patients to have more severe disorders than patients without anaemia. We also revealed some significant immunological differences between RA patients and healthy donors and between patients with and without anaemia, including percent of cells producing IFNγ and/or IL-4. Our data permit to conclude that RA patients have many different immunological disturbances, more severe in anaemic patients.

  11. Ablation front rayleigh taylor dispersion curve in indirect drive

    International Nuclear Information System (INIS)

    Budil, K.S.; Lasinski, B.; Edwards, M.J.; Wan, A.S.; Remington, B.A.; Weber, S.V.; Glendinning, S.G.; Suter, L.; Stry, P.

    2000-01-01

    The Rayleigh-Taylor (RT) instability, which occurs when a lower-density fluid accelerates a higher-density layer, is common in nature. At an ablation front a sharp reduction in the growth rate of the instability at short wave-lengths can occur, in marked contrast to the classical case where growth rates are highest at the shortest wavelengths. Theoretical and numerical investigations of the ablative RT instability are numerous and differ considerably on the level of stabilization expected. We present here the results of a series of laser experiments designed to probe the roll-over and cutoff region of the ablation-front RT dispersion curve in indirect drive. Aluminum foils with imposed sinusoidal perturbations ranging in wavelength from 10 to 70 pm were ablatively accelerated with a radiation drive generated in a gold cylindrical hohlraum. A strong shock wave compresses the package followed by an ∼2 ns period of roughly constant acceleration and the experiment is diagnosed via face-on radiography. Perturbations with wavelengths (ge) 20 (micro)m experienced substantial growth during the acceleration phase while shorter wavelengths showed a sharp drop off in overall growth. These experimental results compared favorably to calculations with a 2-D radiation-hydrodynamics code, however, the growth is significantly affected by the rippled shock launched by the drive. We performed numerical simulations to elucidate the influence of the rippled shock wave on the eventual growth of the perturbations, allowing comparisons to the analytic model developed by Betti et al. This combination of experiments, simulations and analytic modeling illustrates the qualitative simplicity yet quantitative complexity of the compressible RT instability. We have measured the Rayleigh-Taylor (RT) dispersion curve for a radiatively-driven sample in a series of experiments on the Nova laser facility. Planar aluminum foils were ablatively-accelerated and the subsequent perturbation growth was

  12. A model for the induction of bone cancer by 224Ra

    International Nuclear Information System (INIS)

    Groer, P.G.; Marshall, J.H.

    1976-01-01

    A mathematical model for the transformation of normal endosteal cells into malignant tumor cells by α-irradiation is applied to 224 Ra. The model postulates that a normal endosteal cell near the bone surface is transformed into a malignant cell by three consecutive events. The first two events are the initiation events. The probability of their occurrence is proportional to the absorbed endosteal dose and they generate dormant tumor cells. These dormant tumor cells are promoted by the third event, the promotion event. The probability of this last event is proportional to the rate of bone remodeling but independent of the radiation dose. In competition with these transformig events is the killing of any endosteal cell by α-irradiation. Killing is balanced by replacement of killed endosteal cells by normal stem cells. This model provides the following interesting predictions for the human 224 Ra cases. 1) After the decay of 224 Ra the tumor rate decreases exponentially at a rate proportional to the bone turnover rate. 2) For exposure to the same dose the model predicts an increased number of tumors for protacted exposure (i.e. exposure at a lower dose rate). Implications of this model for the therapy of ankylosing spondylitis are discussed. Statistical procedures are suggested for comparison of this theoretical model with the existing data on the induction of osteosarcomas by 224 Ra in man. (orig.) [de

  13. Detection of fission products release in the research reactor 'RA' spent fuel storage pool

    International Nuclear Information System (INIS)

    Matausek, M.V.; Vukadin, Z.; Pavlovic, S.; Maksin, T.; Idakovic, Z.; Marinkovic, N.

    1997-05-01

    Spent fuel resulting from 25 years of operating the 6.5/10 MW thermal heavy water moderated and cooled research reactor RA at the VINCA Institute is presently all stored in the temporary spent fuel storage pool in the basement of the reactor building. In 1984, the reactor was shut down for refurbishment, which for a number of reasons has not yet been completed. Recent investigations show that independent of the future status of the research reactor, safe disposal of the so far irradiated fuel must be the subject of primary concern. The present status of the research reactor RA spent fuel storage pool at the VINCA Institute presents a serious safety problem. Action is therefore initiated in two directions. First, safety of the existing spent fuel storage should be improved. Second, transferring spent fuel into another, presumably dry storage space should be considered. By storing the previously irradiated fuel of the research reactor RA in a newly built storage space, sufficient free space will be provided in the existing spent fuel storage pool for the newly irradiated fuel when the reactor starts operation again. In the case that it would be decided to decommission the research reactor RA, the newly built storage space would provide safe disposal for the fuel irradiated so far

  14. Zernike polynomial based Rayleigh-Ritz model of a piezoelectric unimorph deformable mirror

    CSIR Research Space (South Africa)

    Long, CS

    2012-04-01

    Full Text Available , are routinely and conveniently described using Zernike polynomials. A Rayleigh-Ritz structural model, which uses Zernike polynomials directly to describe the displacements, is proposed in this paper. The proposed formulation produces a numerically inexpensive...

  15. Positive periodic solution for p-Laplacian neutral Rayleigh equation with singularity of attractive type.

    Science.gov (United States)

    Xin, Yun; Liu, Hongmin; Cheng, Zhibo

    2018-01-01

    In this paper, we consider a kind of p -Laplacian neutral Rayleigh equation with singularity of attractive type, [Formula: see text] By applications of an extension of Mawhin's continuation theorem, sufficient conditions for the existence of periodic solution are established.

  16. Rayleigh Waves in a Rotating Orthotropic Micropolar Elastic Solid Half-Space

    Directory of Open Access Journals (Sweden)

    Baljeet Singh

    2013-01-01

    Full Text Available A problem on Rayleigh wave in a rotating half-space of an orthotropic micropolar material is considered. The governing equations are solved for surface wave solutions in the half space of the material. These solutions satisfy the boundary conditions at free surface of the half-space to obtain the frequency equation of the Rayleigh wave. For numerical purpose, the frequency equation is approximated. The nondimensional speed of Rayleigh wave is computed and shown graphically versus nondimensional frequency and rotation-frequency ratio for both orthotropic micropolar elastic and isotropic micropolar elastic cases. The numerical results show the effects of rotation, orthotropy, and nondimensional frequency on the nondimensional speed of the Rayleigh wave.

  17. On the intensity and polarization of radiation emerging from a thick Rayleigh scattering atmosphere

    Directory of Open Access Journals (Sweden)

    V. Natraj

    2011-09-01

    Full Text Available We compute the intensity and polarization of reflected and transmitted light in optically thick Rayleigh scattering atmospheres. We obtain results accurate to seven decimal places. The results have been validated using a variety of methods.

  18. Rayleigh-Sommerfield Diffraction vs Fresnel-Kirchhoff, Fourier Propagation and Poisson's Spot

    National Research Council Canada - National Science Library

    Lucke, Robert

    2004-01-01

    .... These problems are absent in the Rayleigh- Sommerfeld (RS) solution. The difference between RS and FK is in the inclination factor and is usually immaterial because the inclination factor is approximated by unity...

  19. Transmit selection for imperfect threshold-based receive MRC in Rayleigh fading channels

    KAUST Repository

    Radaydeh, Redha Mahmoud Mesleh; Alouini, Mohamed-Slim

    2010-01-01

    experience identically distributed and non-identically distributed Rayleigh fading conditions. New closed-form expressions for the combined SNR statistics and some performance measures are presented. The system models adopted herein and the presented

  20. Rayleigh Taylor instability of two superposed compressible fluids in un-magnetized plasma

    International Nuclear Information System (INIS)

    Sharma, P K; Tiwari, A; Argal, S; Chhajlani, R K

    2014-01-01

    The linear Rayleigh Taylor instability of two superposed compressible Newtonian fluids is discussed with the effect of surface tension which can play important roles in space plasma. As in both the superposed Newtonian fluids, the system is stable for potentially stable case and unstable for potentially unstable case in the present problem also. The equations of the problem are solved by normal mode method and a dispersion relation is obtained for such a system. The behaviour of growth rate is examined in the presence of surface tension and it is found that the surface tension has stabilizing influence on the Rayleigh Taylor instability of two superposed compressible fluids. Numerical analysis is performed to show the effect of sound velocity and surface tension on the growth rate of Rayleigh Taylor instability. It is found that both parameters have stabilizing influence on the growth rate of Rayleigh Taylor instability.

  1. Higher order capacity statistics of multi-hop transmission systems over Rayleigh fading channels

    KAUST Repository

    Yilmaz, Ferkan; Tabassum, Hina; Alouini, Mohamed-Slim

    2012-01-01

    In this paper, we present an exact analytical expression to evaluate the higher order statistics of the channel capacity for amplify and forward (AF) multihop transmission systems operating over Rayleigh fading channels. Furthermore, we present

  2. Ultraviolet Rayleigh Scatter Imaging for Spatial Temperature Profiles in Atmospheric Microdischarges

    Science.gov (United States)

    2014-09-01

    approximation of Rayleigh scattering for atomic gases, such as helium and argon . 13 Approved for public release; distribution unlimited. Figure 3... polarizability tensor , as [13] = + + = + + ...22�. (25) 16 Approved for public release; distribution unlimited. To further define the polarizability

  3. 226Ra and 228Ra in scale and sludge samples and their correlation with the chemical composition.

    Science.gov (United States)

    Godoy, José Marcus; da Cruz, Rosana Petinatti

    2003-01-01

    In order to contribute to a future waste management policy related to the presence of technologically enhanced natural occurring radioactive material (TENORM) in the Brazilian petroleum industry, the present work presents the chemical composition and the (226)Ra and (228)Ra content of sludge and scales generated during the offshore E and P petroleum activities in the Campos Basin, the primary offshore oil production region in Brazil. The (226)Ra and (228)Ra content on 36 sludge and scales samples were determined by gamma-spectrometry. Based on X-ray diffractometry results, a chemical analysis schema for these samples was developed. The results have shown that scales are 75% barium and strontium sulfates, with a mean (226)Ra and (228)Ra content of 106 kBq kg(-1) and 78 kBq kg(-1), respectively. On the other hand, sludge samples have a much more complex chemical composition than the scales. The (226)Ra and (228)Ra content in sludge also varies much more than the content observed in the scales samples and ranged from 0.36 to 367 kBq kg(-1) and 0.25 to 343 kBq kg(-1), respectively.

  4. RA Reactor operation and maintenance (I-IX), Part I; Pogon i odrzavanje reaktora RA (I-IX), I Deo

    Energy Technology Data Exchange (ETDEWEB)

    Zecevic, V [Institute of Nuclear Sciences Boris Kidric, Reaktor RA, Vinca, Beograd (Serbia and Montenegro)

    1963-12-15

    The report on RA reactor operation and maintenance for year 1963 is divided in six tasks. This volume contains the introductory report, and three tasks of the final report, namely reactor exploitation, reactivity changes of the RA reactor before repair, planning of refuelling.

  5. RA Reactor operation and maintenance (I-IX), part VII, Task 3.08/04, Refurbishment of the RA reactor

    International Nuclear Information System (INIS)

    Zecevic, V.

    1963-12-01

    This volume covers the following reports concerned with the maintenance and repair work of the RA reactor: repair of the technical water system; maintenance of the transportation equipment; vacuuming and drying during refurbishment; repair and decontamination of the distillation device; and the report on participation of the operational dosimetry division in the RA reactor refurbishment activities

  6. Filtered Rayleigh scattering mixing measurements of merging and non-merging streamwise vortex interactions in supersonic flow

    Science.gov (United States)

    Ground, Cody R.; Gopal, Vijay; Maddalena, Luca

    2018-04-01

    By introducing large-scale streamwise vortices into a supersonic flow it is possible to enhance the rate of mixing between two fluid streams. However, increased vorticity content alone does not explicitly serve as a predictor of mixing enhancement. Additional factors, particularly the mutual interactions occurring between neighboring vortical structures, affect the underlying fundamental physics that influence the rate at which the fluids mix. As part of a larger systematic study on supersonic streamwise vortex interactions, this work experimentally quantifies the average rate of mixing of helium and air in the presence of two separate modes of vortex interaction, the merging and non-merging of a pair of co-rotating vortices. In these experiments vortex-generating expansion ramps are placed on a strut injector. The freestream Mach number is set at 2.5 and helium is injected as a passive scalar. Average injectant mole fractions at selected flow planes downstream of the injector are measured utilizing the filtered Rayleigh scattering technique. The filtered Rayleigh scattering measurements reveal that, in the domain surveyed, the merging vortex interaction strongly displaces the plume from its initial horizontal orientation while the non-merging vortex interaction more rapidly mixes the helium and air. The results of the current experiments are consistent with associated knowledge derived from previous analyses of the two studied configurations which have included the detailed experimental characterization of entrainment, turbulent kinetic energy, and vorticity of both modes of vortex interaction.

  7. Effects of thermal conduction and compressibility on Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Takabe, Hideaki; Mima, Kunioki.

    1980-01-01

    In order to study the stability of the ablation front in laser driven implosion, the thermal conduction and compressibility effects on the Rayleigh-Taylor instability are considered. It is found that the thermal conduction effect cannot stabilize the Rayleigh-Taylor mode, but reduce the growth rate in the short wavelength case. But, the growth rate is found not to differ from the classical value √gk in the long wavelength limit, where the compressibility is essential. (author)

  8. Search for Rayleigh-Taylor instability in laser irradiated layered thin foil targets

    International Nuclear Information System (INIS)

    Kilkenny, J.D.; Hares, J.D.; Rumsby, P.T.

    1980-01-01

    An experiment to measure the Rayleigh-Taylor instability at the vacuum-ablation surface of laser irradiated layered targets by time resolved x-ray spectroscopy is described. The time taken to burn through a layer of material is measured to be the same for massive targets as for thin foil accelerating targets. It is inferred that the thin foil targets might be Rayleigh-Taylor stable despite the values of γtauapproximately equal to15 calculated from classical theory. (author)

  9. Study on Software Quality Improvement based on Rayleigh Model and PDCA Model

    OpenAIRE

    Ning Jingfeng; Hu Ming

    2013-01-01

    As the software industry gradually becomes mature, software quality is regarded as the life of a software enterprise. This article discusses how to improve the quality of software, applies Rayleigh model and PDCA model to the software quality management, combines with the defect removal effectiveness index, exerts PDCA model to solve the problem of quality management objectives when using the Rayleigh model in bidirectional quality improvement strategies of software quality management, a...

  10. Regimes of the magnetized Rayleigh endash Taylor instability

    International Nuclear Information System (INIS)

    Winske, D.

    1996-01-01

    Hybrid simulations with kinetic ions and massless fluid electrons are used to investigate the linear and nonlinear behavior of the magnetized Rayleigh endash Taylor instability in slab geometry with the plasma subject to a constant gravity. Three regimes are found, which are determined by the magnitude of the complex frequency ω=ω r +iγ. For |ω| i (Ω i = ion gyrofrequency), one finds the typical behavior of the usual fluid regime, namely the development of open-quote open-quote mushroom-head close-quote close-quote spikes and bubbles in the density and a strongly convoluted boundary between the plasma and magnetic field, where the initial gradient is not relaxed much. A second regime, where |ω|∼0.1Ω i , is characterized by the importance of the Hall term. Linearly, the developing flute modes are more finger-like and tilted along the interface; nonlinearly, clump-like structures form, leading to a significant broadening of the interface. The third regime is characterized by unmagnetized ion behavior, with |ω|∼Ω i . Density clumps, rather than flutes, form in the linear stage, while nonlinearly, longer-wavelength modes that resemble those in fluid regime dominate. Finite Larmor radius stabilization of short-wavelength modes is observed in each regime. copyright 1996 American Institute of Physics

  11. New mitigation schemes of the ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Azechi, H.; Shiraga, H.; Nakai, M.; Shigemori, K.; Fujioka, S.; Sakaiya, T.; Tamari, Y.; Ohtani, K.; Watari, T.; Murakami, M.; Sunahara, A.; Nagatomo, H.; Nishihara, K.; Miyanaga, N.; Izawa, Y.; Ohnishi, N.

    2005-01-01

    The Rayleigh-Taylor (RT) instability with material ablation through the unstable interface is the key physics that determines success or failure of inertial fusion energy (IFE) generation, as the RT instability potentially quenches ignition and burn by disintegrating the IFE target. We present two suppression schemes of the RT growth without significant degradation of the target density. The first scheme is to generate double ablation structure in high-Z doped plastic targets. In addition to the electron ablation surface, a new ablation surface is created by x-ray radiation from the high-Z ions. Contrary to the previous thought, the electron ablation surface is almost completely stabilized by extremely high flow velocity. On the other hand, the RT instability on the radiative ablation surface is significantly moderated. The second is to enhance the nonlocal nature of the electron heat transport by illuminating the target with long wavelength laser light, whereas the high ablation pressure is generated by irradiating short wavelength laser light. The significant suppression of the RT instability may increase the possibility of impact ignition which uses a high velocity fuel colliding with a preformed main fuel. (author)

  12. Analytic-continuation approach to the resummation of divergent series in Rayleigh-Schrödinger perturbation theory

    Science.gov (United States)

    Mihálka, Zsuzsanna É.; Surján, Péter R.

    2017-12-01

    The method of analytic continuation is applied to estimate eigenvalues of linear operators from finite order results of perturbation theory even in cases when the latter is divergent. Given a finite number of terms E(k ),k =1 ,2 ,⋯M resulting from a Rayleigh-Schrödinger perturbation calculation, scaling these numbers by μk (μ being the perturbation parameter) we form the sum E (μ ) =∑kμkE(k ) for small μ values for which the finite series is convergent to a certain numerical accuracy. Extrapolating the function E (μ ) to μ =1 yields an estimation of the exact solution of the problem. For divergent series, this procedure may serve as resummation tool provided the perturbation problem has a nonzero radius of convergence. As illustrations, we treat the anharmonic (quartic) oscillator and an example from the many-electron correlation problem.

  13. 226Ra and 228Ra activities associated with agricultural drainage ponds and wetland ponds in the Kankakee Watershed, Illinois-Indiana, USA

    International Nuclear Information System (INIS)

    Sidle, W.C.; Shanklin, D.; Lee, P.Y.; Roose, D.L.

    2001-01-01

    Background radioactivity is elevated in many agricultural drainage ponds and also constructed wetland ponds in the Kankakee watershed. During 1995-1999, gross-α and -β activities were measured up to 455 and 1650 mBq L -1 , respectively. 226 Ra and 228 Ra averaged 139 and 192 mBq L -1 in controlled drainage ponds compared to 53 and 58 mBq L -1 for 226 Ra and 228 Ra, respectively, in native wetland ponds. Analyses of applied ammonium phosphate fertilizers near both native and controlled ponds indicate comparable 226 Ra/ 228 Ra and 228 Ra/ 232 Th activity ratios with only the surface waters in the controlled ponds. For example, 226 Ra/ 228 Ra activity ratios in controlled ponds ranged from 0.79 to 0.91 and group with a local fertilizer batch containing FL phosphate compounds with 226 Ra/ 228 Ra activity ratios of 0.83-1.04. Local soils of the Kankakee watershed have 226 Ra/ 228 Ra activity ratios of 0.54-0.70. Calculated Ra fluxes of waters, in drainage ditches associated with these controlled ponds, for 226 Ra ranged from 0.77 to 9.00 mBq cm -2 d -1 and for 228 Ra ranged from 1.22 to 8.43 mBq cm -2 d -1 . Ra activity gradients were measured beneath these controlled ponds both in agricultural landscapes and in constructed wetlands, all being associated with drainage ditches. Ra had infiltrated to the local water table but was below regulatory maximum contaminant limits. Still, measurable Ra activity was measured downgradient of even the constructed wetlands in the Kankakee watershed, suggesting that the attenuation of Ra was low. However, no Ra excess was observed in the riparian zone or the Kankakee River downgradient of the native wetland ponds

  14. RA reactor exploitation, task 3.08/01; Zadatak 3.08/01 - Eksploatacija reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    Zecevic, V [Institute of Nuclear Sciences Boris Kidric, Reaktor RA, Vinca, Beograd (Serbia and Montenegro)

    1963-12-15

    During 1963 the RA reactor was operated for 1852 hours at mean power of 5.7 MW (total power production was 10716 MWh). Reactor was used for irradiation according to the demand of 356 users, and 15 experiments. The reason for decreased operation in comparison with the previous year was repair of all the reactor equipment and decontamination of the heavy water system. This report contains detailed data about reactor power, reactivity changes and fuel burnup. Mean monthly usage of the reactor experimental channels as well as samples which were irradiated are part of this report.

  15. RA research reactor - properties and experimental capabilities; Istrazivacki reaktor RA - Tehnicke karakteristike i eksploatacione mogucnosti

    Energy Technology Data Exchange (ETDEWEB)

    Milosevic, M; Martinc, R [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1978-05-15

    The brief survey of the Reactor RA exploitation experience, as well as the reactor equipment state, after 18 years of operation is presented. The results of efforts spent on reactor characteristics improvement in order to ensure safe and reliable reactor operation for next 15-20 years, are described. Prikazani su fragmenti iz eksploatacije reaktora kao i stanje opreme, posle 18 godina rada. Na kraju je dat prikaz sta je preduzeto i sta se preduzima da se poboljsaju karakteristike i poveca sigurnost i bezbednost rada za sledecih 15-20 godina.

  16. Measurement of neutrons in the RA reactor cell; Merenje neutrona u elementarnoj celiji reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    Raisic, N; Bosevski, T [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    A special experimental device was constructed for measuring the neutron flux distribution in the RA reactor cell. This device simulated the reactor cell in order to avoid disturbance in the reactor core. It was made of an aluminium cylindrical vessel having outer diameter same as the vertical experimental channel and contained three fuel slugs. Hole was made in through the center of the fuel slugs and a copper wire was placed in the hole for measuring the thermal neutron flux distribution. It was placed in the experimental channel VK-5 in the location of highest neutron flux. Handling of samples for irradiation was quite simple.

  17. Seasonal variations in 228Ra/226Ra ratio within coastal waters of the Sea of Japan: implications for water circulation patterns in coastal areas

    International Nuclear Information System (INIS)

    Inoue, M.; Tanaka, K.; Watanabe, S.; Kofuji, H.; Yamamoto, M.; Komura, K.

    2006-01-01

    In this study, low-background γ-spectrometry was used to determine the 228 Ra/ 226 Ra ratio of 131 coastal water samples from various environments around Honshu Island, Japan (mainly around Noto Peninsula) at 1-3 month intervals from April 2003 until September 2005. Spatial variation in 228 Ra/ 226 Ra ratios was also assessed by analyzing 34 coastal water samples from five areas within the Sea of Japan during May and June 2004. The 228 Ra/ 226 Ra ratio of coastal water from all sites around Noto Peninsula shows seasonal variation, with minimum values during summer ( 228 Ra/ 226 Ra = 0.7) and maximum values during autumn-winter ( 228 Ra/ 226 Ra = 1.7-2). This seasonal variation is similar to that recorded for coastal water between Tsushima Strait and Noto Peninsula. The measured lateral variation in 228 Ra/ 226 Ra ratios within coastal water between Tsushima Strait and Noto Peninsula is only minor (0.5-0.7; May-June 2004). Coastal waters from two other sites (Pacific shore and Tsugaru Strait, north Honshu) show no clear seasonal variation in 228 Ra/ 226 Ra ratio. These measured variations in 228 Ra/ 226 Ra ratio, especially the temporal variations, have important implications for seasonal changes in patterns of coastal water circulation within the Sea of Japan

  18. Hydroxyapatite particles as carriers for "2"2"3Ra

    International Nuclear Information System (INIS)

    Vasiliev, A.N.

    2017-01-01

    Systematic investigation of optimal conditions for preparation and in vitro stability of HAP particles labeled with "2"2"3Ra, that could be considered as promising candidates for targeted α-therapy, has been carried out. Two different approaches to HAP labelling were tested: sorption of Ra"2"+ on pre-synthesized HAP-particles and incorporation of Ra"2"+ into the structure of HAP during its synthesis. Two textural forms of HAP particles were used-nanoparticles and particles with the diameter of 350 ± 20 μm. Kinetics of "2"2"3Ra sorption on HAP of different particle size and desorption in 0.9 % NaCl solution were studied. The influence of solution acidity and solid to liquid phase ratio on sorption of Ra was evaluated and the sorption yield up to 98 % was achieved. It was found that the optimal conditions for the sorption included synthesis of HAP nanoparticles in the presence of "2"2"3Ra at pH values of 4-7 followed by annealing at 900 deg C. In this case subsequent cumulative desorption of Ra was <5 % of initial activity. (author)

  19. Modeling the Energy Performance of LoRaWAN.

    Science.gov (United States)

    Casals, Lluís; Mir, Bernat; Vidal, Rafael; Gomez, Carles

    2017-10-16

    LoRaWAN is a flagship Low-Power Wide Area Network (LPWAN) technology that has highly attracted much attention from the community in recent years. Many LoRaWAN end-devices, such as sensors or actuators, are expected not to be powered by the electricity grid; therefore, it is crucial to investigate the energy consumption of LoRaWAN. However, published works have only focused on this topic to a limited extent. In this paper, we present analytical models that allow the characterization of LoRaWAN end-device current consumption, lifetime and energy cost of data delivery. The models, which have been derived based on measurements on a currently prevalent LoRaWAN hardware platform, allow us to quantify the impact of relevant physical and Medium Access Control (MAC) layer LoRaWAN parameters and mechanisms, as well as Bit Error Rate (BER) and collisions, on energy performance. Among others, evaluation results show that an appropriately configured LoRaWAN end-device platform powered by a battery of 2400 mAh can achieve a 1-year lifetime while sending one message every 5 min, and an asymptotic theoretical lifetime of 6 years for infrequent communication.

  20. Modeling the Energy Performance of LoRaWAN

    Directory of Open Access Journals (Sweden)

    Lluís Casals

    2017-10-01

    Full Text Available LoRaWAN is a flagship Low-Power Wide Area Network (LPWAN technology that has highly attracted much attention from the community in recent years. Many LoRaWAN end-devices, such as sensors or actuators, are expected not to be powered by the electricity grid; therefore, it is crucial to investigate the energy consumption of LoRaWAN. However, published works have only focused on this topic to a limited extent. In this paper, we present analytical models that allow the characterization of LoRaWAN end-device current consumption, lifetime and energy cost of data delivery. The models, which have been derived based on measurements on a currently prevalent LoRaWAN hardware platform, allow us to quantify the impact of relevant physical and Medium Access Control (MAC layer LoRaWAN parameters and mechanisms, as well as Bit Error Rate (BER and collisions, on energy performance. Among others, evaluation results show that an appropriately configured LoRaWAN end-device platform powered by a battery of 2400 mAh can achieve a 1-year lifetime while sending one message every 5 min, and an asymptotic theoretical lifetime of 6 years for infrequent communication.

  1. Behavior of 226Ra in the Mississippi River mixing zone

    Science.gov (United States)

    Moore, Daniel G.; Scott, Martha R.

    1986-12-01

    The behavior of 226Ra in the Mississippi River mixing zone is strongly nonconservative and includes desorption similar to that reported for the Hudson, Pee Dee, and Amazon rivers. However, dissolved and desorbed 226Ra concentrations in the Mississippi are 2 to 5 times greater than in the other rivers at the same salinity. Radium concentrations vary inversely with the water discharge rate. The 226Ra desorption maximum occurs at a salinity of 5.0, much lower than the 18 to 28 salinity values for the maxima of the other three rivers. High concentrations of dissolved 226Ra (up to 82 dpm per 100 L) and the low salinity values for the desorption maximum in the Mississippi River result from three major factors. Suspended sediments include a large fraction of montmorillonite, which gives the sediment a high cation exchange capacity, 0.54 meq/g. The average suspended sediment load is large, about 510 mg/L, and contains 1.9 dpm/g desorbable 226Ra. The dissolved 226Ra river water end-member (9.6 dpm per 100 L) is higher than in surface seawater. The annual contribution of 226Ra to the ocean from the Mississippi River is 3.7 × 1014 dpm/yr, based on data from three cruises. Evidence of flux of 226Ra from estuarine and shelf sediments is common in vertical profile sampling of the deltaic waters but is not reflected in calculations made with an "apparent" river water Ra value extrapolated to zero salinity.

  2. Factors associated with absenteeism, presenteeism and activity impairment in patients in the first years of RA.

    Science.gov (United States)

    Bansback, Nick; Zhang, Wei; Walsh, David; Kiely, Patrick; Williams, Richard; Guh, Daphne; Anis, Aslam; Young, Adam

    2012-02-01

    To understand the impact of the early years of RA on all aspects of work productivity, and determine how this is related to clinical markers. Previous research on work productivity has examined predominantly early retirement and absenteeism. The impact of reduced work performance (presenteeism) and activity impairment is less well understood in early RA populations. Working patients enrolled in an RA inception cohort were recruited into a nested study. A questionnaire incorporating the Work Productivity and Activity Impairment (WPAI) instrument was administered with a number of clinical outcomes, including the Multidimensional Health Assessment Questionnaire (MD-HAQ) and scales for pain, fatigue and patient assessment of disease patient global assessment (PtGA). Analysis included 150 RA patients, with the mean age at onset being 48 years (s.d. 10 years) and disease duration from symptom onset being 49 months. Patients had relatively mild disease: MD-HAQ (0.6), pain (3.6), PtGA (3.6) and fatigue (4.6). Of the 92% patients working for pay, 19% reported missing work (absenteeism) in the past week due to their health, accounting for 46% of their working time. Even while at work, ∼25% of actual hours was lost due to poor health, while outside work 33% of patients' regular daily activities were prevented. In multivariate analyses, disease severity was associated with the presence of absenteeism, presenteeism and activity impairment. Patients able to self-schedule their work had lower presenteeism and activity impairment. Productivity loss is common in patients in the first years of RA who are in paid work and was associated with work characteristics and adverse clinical outcomes.

  3. Mitigating Inter-Network Interference in LoRa Networks

    OpenAIRE

    Voigt, Thiemo; Bor, Martin; Roedig, Utz; Alonso, Juan

    2017-01-01

    Long Range (LoRa) is a popular technology used to construct Low-Power Wide-Area Network (LPWAN) networks. Given the popularity of LoRa it is likely that multiple independent LoRa networks are deployed in close proximity. In this situation, neighbouring networks interfere and methods have to be found to combat this interference. In this paper we investigate the use of directional antennae and the use of multiple base stations as methods of dealing with inter-network interference. Directional a...

  4. Thin layer model for nonlinear evolution of the Rayleigh-Taylor instability

    Science.gov (United States)

    Zhao, K. G.; Wang, L. F.; Xue, C.; Ye, W. H.; Wu, J. F.; Ding, Y. K.; Zhang, W. Y.

    2018-03-01

    On the basis of the thin layer approximation [Ott, Phys. Rev. Lett. 29, 1429 (1972)], a revised thin layer model for incompressible Rayleigh-Taylor instability has been developed to describe the deformation and nonlinear evolution of the perturbed interface. The differential equations for motion are obtained by analyzing the forces (the gravity and pressure difference) of fluid elements (i.e., Newton's second law). The positions of the perturbed interface are obtained from the numerical solution of the motion equations. For the case of vacuum on both sides of the layer, the positions of the upper and lower interfaces obtained from the revised thin layer approximation agree with that from the weakly nonlinear (WN) model of a finite-thickness fluid layer [Wang et al., Phys. Plasmas 21, 122710 (2014)]. For the case considering the fluids on both sides of the layer, the bubble-spike amplitude from the revised thin layer model agrees with that from the WN model [Wang et al., Phys. Plasmas 17, 052305 (2010)] and the expanded Layzer's theory [Goncharov, Phys. Rev. Lett. 88, 134502 (2002)] in the early nonlinear growth regime. Note that the revised thin layer model can be applied to investigate the perturbation growth at arbitrary Atwood numbers. In addition, the large deformation (the large perturbed amplitude and the arbitrary perturbed distributions) in the initial stage can also be described by the present model.

  5. Weakly nonlinear incompressible Rayleigh-Taylor instability growth at cylindrically convergent interfaces

    International Nuclear Information System (INIS)

    Wang, L. F.; He, X. T.; Wu, J. F.; Zhang, W. Y.; Ye, W. H.

    2013-01-01

    A weakly nonlinear (WN) model has been developed for the incompressible Rayleigh-Taylor instability (RTI) in cylindrical geometry. The transition from linear to nonlinear growth is analytically investigated via a third-order solutions for the cylindrical RTI initiated by a single-mode velocity perturbation. The third-order solutions can depict the early stage of the interface asymmetry due to the bubble-spike formation, as well as the saturation of the linear (exponential) growth of the fundamental mode. The WN results in planar RTI [Wang et al., Phys. Plasmas 19, 112706 (2012)] are recovered in the limit of high-mode number perturbations. The difference between the WN growth of the RTI in cylindrical geometry and in planar geometry is discussed. It is found that the interface of the inward (outward) development spike/bubble is extruded (stretched) by the additional inertial force in cylindrical geometry compared with that in planar geometry. For interfaces with small density ratios, the inward growth bubble can grow fast than the outward growth spike in cylindrical RTI. Moreover, a reduced formula is proposed to describe the WN growth of the RTI in cylindrical geometry with an acceptable precision, especially for small-amplitude perturbations. Using the reduced formula, the nonlinear saturation amplitude of the fundamental mode and the phases of the Fourier harmonics are studied. Thus, it should be included in applications where converging geometry effects play an important role, such as the supernova explosions and inertial confinement fusion implosions.

  6. Nonlinear saturated states of the magnetic-curvature-driven Rayleigh-Taylor instability in three dimensions

    International Nuclear Information System (INIS)

    Das, Amita; Sen, Abhijit; Kaw, Predhiman; Benkadda, S.; Beyer, Peter

    2005-01-01

    Three-dimensional electromagnetic fluid simulations of the magnetic-curvature-driven Rayleigh-Taylor instability are presented. Issues related to the existence of nonlinear saturated states and the nature of the temporal evolution to such states from random initial conditions are addressed. It is found that nonlinear saturated states arising from generation of zonal shear flows continue to exist in certain parametric domains but their spectrum and spatial characteristics have important differences from earlier two-dimensional results reported in Phys. Plasmas 4, 1018 (1997) and Phys. Plasmas 8, 5104 (2001). In particular, the three-dimensional nonlinear states possess a significant power level in short scales and the spatial structures of the potential and density fluctuations appear not to develop any functional correlations. Electromagnetic effects are found to inhibit the formation of zonal flows and thereby to considerably restrict the parametric domain of nonlinear stabilization. The role of finite k parallel and the contribution of the unstable drift wave branch are also discussed and delineated through a number of simulation studies carried out in special simplified limits

  7. Spanwise homogeneous buoyancy-drag model for Rayleigh-Taylor mixing and experimental evaluation

    International Nuclear Information System (INIS)

    Dimonte, Guy

    2000-01-01

    A buoyancy-drag model for Rayleigh-Taylor (RT) mixing is developed on the premise that the bubble and spike regions behave as distinct and spanwise homogeneous fluids. Then, mass conservation is applied accross the mixing zone to obtain their average mixture densities dynamically. These are used to explicitly calculate the inertia and buoyancy terms in the evolutionary equation. The only unknown parameter in the model is the Newtonian drag constant C∼2.5±0.6, which is determined from turbulent RT experiments over various Atwood numbers A and acceleration histories g(t). The bubble (i=2) and spike (i=1) amplitudes are found to obey the familiar h i =α i Agt 2 for a constant g and h i ∼t θ i for an impulsive g. For bubbles, both α 2 and θ 2 are insensitive to A. For the spikes, both α 1 and θ 1 increase as a power law with the density ratio. However, θ 1 is not universal because it depends on the initial value of h 1 /h 2 . (c) 2000 American Institute of Physics

  8. Statistics for Ratios of Rayleigh, Rician, Nakagami-m, and Weibull Distributed Random Variables

    Directory of Open Access Journals (Sweden)

    Dragana Č. Pavlović

    2013-01-01

    Full Text Available The distributions of ratios of random variables are of interest in many areas of the sciences. In this brief paper, we present the joint probability density function (PDF and PDF of maximum of ratios μ1=R1/r1 and μ2=R2/r2 for the cases where R1, R2, r1, and r2 are Rayleigh, Rician, Nakagami-m, and Weibull distributed random variables. Random variables R1 and R2, as well as random variables r1 and r2, are correlated. Ascertaining on the suitability of the Weibull distribution to describe fading in both indoor and outdoor environments, special attention is dedicated to the case of Weibull random variables. For this case, analytical expressions for the joint PDF, PDF of maximum, PDF of minimum, and product moments of arbitrary number of ratios μi=Ri/ri, i=1,…,L are obtained. Random variables in numerator, Ri, as well as random variables in denominator, ri, are exponentially correlated. To the best of the authors' knowledge, analytical expressions for the PDF of minimum and product moments of {μi}i=1L are novel in the open technical literature. The proposed mathematical analysis is complemented by various numerical results. An application of presented theoretical results is illustrated with respect to performance assessment of wireless systems.

  9. Rayleigh scattering of a cylindrical sound wave by an infinite cylinder.

    Science.gov (United States)

    Baynes, Alexander B; Godin, Oleg A

    2017-12-01

    Rayleigh scattering, in which the wavelength is large compared to the scattering object, is usually studied assuming plane incident waves. However, full Green's functions are required in a number of problems, e.g., when a scatterer is located close to the ocean surface or the seafloor. This paper considers the Green's function of the two-dimensional problem that corresponds to scattering of a cylindrical wave by an infinite cylinder embedded in a homogeneous fluid. Soft, hard, and impedance cylinders are considered. Exact solutions of the problem involve infinite series of products of Bessel functions. Here, simple, closed-form asymptotic solutions are derived, which are valid for arbitrary source and receiver locations outside the cylinder as long as its diameter is small relative to the wavelength. The scattered wave is given by the sum of fields of three linear image sources. The viability of the image source method was anticipated from known solutions of classical electrostatic problems involving a conducting cylinder. The asymptotic acoustic Green's functions are employed to investigate reception of low-frequency sound by sensors mounted on cylindrical bodies.

  10. Coupling of sausage, kink, and magneto-Rayleigh-Taylor instabilities in a cylindrical liner

    International Nuclear Information System (INIS)

    Weis, M. R.; Zhang, P.; Lau, Y. Y.; Gilgenbach, R. M.; Schmit, P. F.; Peterson, K. J.; Hess, M.

    2015-01-01

    This paper analyzes the coupling of magneto-Rayleigh-Taylor (MRT), sausage, and kink modes in an imploding cylindrical liner, using ideal MHD. A uniform axial magnetic field of arbitrary value is included in each region: liner, its interior, and its exterior. The dispersion relation is solved exactly, for arbitrary radial acceleration (-g), axial wavenumber (k), azimuthal mode number (m), liner aspect ratio, and equilibrium quantities in each region. For small k, a positive g (inward radial acceleration in the lab frame) tends to stabilize the sausage mode, but destabilize the kink mode. For large k, a positive g destabilizes both the kink and sausage mode. Using the 1D-HYDRA simulation results for an equilibrium model that includes a pre-existing axial magnetic field and a preheated fuel, we identify several stages of MRT-sausage-kink mode evolution. We find that the m = 1 kink-MRT mode has a higher growth rate at the initial stage and stagnation stage of the implosion, and that the m = 0 sausage-MRT mode dominates at the main part of implosion. This analysis also sheds light on a puzzling feature in Harris' classic paper of MRT [E. G. Harris, Phys. Fluids 5, 1057 (1962)]. An attempt is made to interpret the persistence of the observed helical structures [Awe et al., Phys. Rev. Lett. 111, 235005 (2013)] in terms of non-axisymmetric eigenmode

  11. Linear theory of the Rayleigh-Taylor instability in the equatorial ionsophere

    International Nuclear Information System (INIS)

    Russel, D.A.; Ott, E.

    1979-01-01

    We present a liner theory of the Rayleigh-Taylor instability in the equatorial ionosphere. For a purely exponential density profile, we find that no unstable eigenmode solutions exist. For a particular model ionosphere with an F peak, unstable eigenmode solutions exist only for sufficiently small horizontal wave numbers. In the later case, purely exponential growth at a rate identical to that for the sharp boundary instability is found. To clarify the situation in the case that eigenmodes do not exist, we solve the initial value problem for the linearized ion equation of motion in the long time asymptotic limit. Ion inertia and ion-neutral collisions are included. Assuming straight magnetic field lines, we find that when eigenmodes do not exist the growth of the response to an impulse is slower than exponential viz, t=/sup -1/2/ exp (γ/sup t/) below the F peak and t/sup -3/2/ exp(γ/sup t/) above the peak; and we determine γ

  12. Rayleigh-Brillouin scattering in SF6 in the kinetic regime

    Science.gov (United States)

    Wang, Yuanqing; Yu, Yin; Liang, Kun; Marques, Wilson; van de Water, Willem; Ubachs, Wim

    2017-02-01

    Rayleigh-Brillouin spectral profiles are measured with a laser-based scatterometry setup for a 90° scattering angle at a high signal-to-noise ratio (r.m.s. noise below 0.15% w.r.t. peak intensity) in sulfur-hexafluoride gas for pressures in the range 0.2-5 bar and for a wavelength of λ = 403.0 nm. The high quality data are compared to a number of light scattering models in order to address the effects of rotational and vibrational relaxation. While the vibrational relaxation rate is so slow that vibration degrees of freedom remain frozen, rotations relax on time scales comparable to those of the density fluctuations. Therefore, the heat capacity, the thermal conductivity and the bulk viscosity are all frequency-dependent transport coefficients. This is relevant for the Tenti model that depends on the values chosen for these transport coefficients. This is not the case for the other two models considered: a kinetic model based on rough-sphere interactions, and a model based on fluctuating hydrodynamics. The deviations with the experiment are similar between the three different models, except for the hydrodynamic model at pressures p≲ 2bar . As all models are in line with the ideal gas law, we hypothesize the presence of real gas effects in the measured spectra.

  13. The Experimental Study of Rayleigh-Taylor Instability using a Linear Induction Motor Accelerator

    Science.gov (United States)

    Yamashita, Nicholas; Jacobs, Jeffrey

    2009-11-01

    The experiments to be presented utilize an incompressible system of two stratified miscible liquids of different densities that are accelerated in order to produce the Rayleigh-Taylor instability. Three liquid combinations are used: isopropyl alcohol with water, a calcium nitrate solution or a lithium polytungstate solution, giving Atwood numbers of 0.11, 0.22 and 0.57, respectively. The acceleration required to drive the instability is produced by two high-speed linear induction motors mounted to an 8 m tall drop tower. The motors are mounted in parallel and have an effective acceleration length of 1.7 m and are each capable of producing 15 kN of thrust. The liquid system is contained within a square acrylic tank with inside dimensions 76 x76x184 mm. The tank is mounted to an aluminum plate, which is driven by the motors to create constant accelerations in the range of 1-20 g's, though the potential exists for higher accelerations. Also attached to the plate are a high-speed camera and an LED backlight to provide continuous video of the instability. In addition, an accelerometer is used to provide acceleration measurements during each experiment. Experimental image sequences will be presented which show the development of a random three-dimensional instability from an unforced initial perturbation. Measurements of the mixing zone width will be compared with traditional growth models.

  14. Bubble velocity in the nonlinear Rayleigh-Taylor instability at a deflagration front

    International Nuclear Information System (INIS)

    Modestov, Mikhail; Bychkov, Vitaly; Betti, Riccardo; Eriksson, Lars-Erik

    2008-01-01

    The Rayleigh-Taylor instability at a deflagration front is studied systematically using extensive direct numerical simulations. It is shown that, for a sufficiently large gravitational field, the effects of bubble rising dominate the deflagration dynamics. It is demonstrated both analytically and numerically that the deflagration speed is described asymptotically by the Layzer theory in the limit of large acceleration. In the opposite limit of small and zero gravitational field, intrinsic properties of the deflagration front become important. In that case, the deflagration speed is determined by the velocity of a planar front and by the Darrieus-Landau instability. Because of these effects, the deflagration speed is larger than predicted by the Layzer theory. An analytical formula for the deflagration speed is suggested, which matches two asymptotic limits of large and small acceleration. The formula is in good agreement with the numerical data in a wide range of Froude numbers. The present results are also in agreement with previous numerical simulations on this problem

  15. Exact capture probability analysis of GSC receivers over Rayleigh fading channel

    KAUST Repository

    Nam, Sungsik

    2010-01-01

    For third generation systems and ultrawideband systems, RAKE receivers have been introduced due to the advantage of RAKE receivers which is their ability to combine different replicas of the transmitted signal arriving at different delays in a rich multipath environment. In principle, RAKE receivers combine all resolvable paths which gives the best performance in a rich diversity environment. However, this is usually costly in terms of hardware required as the number of RAKE fingers increases. Therefore, generalized selection combining (GSC) RAKE reception was proposed and has been studied by many researcher as an alternative to the classical two fundamental diversity schemes: maximal ratio combining and selection combining. Previous work on performance analyses of GSC RAKE receivers based on the signal to noise ratio focused on the development of methodologies to derive exact closedform expressions for various performance measures. However, the remaining set of uncombined paths affect the overall performance both in terms of loss in power. Therefore, to have a full understanding of the performance of GSC RAKE receivers, we introduce in this paper the notion of capture probability, which is defined as the ratio of the captured power (essentially combined paths power) to that of the total available power. The major difficulty in these problems is to derive some joint statistics of ordered exponential variates. With this motivation in mind, we capitalize in this paper on some new order statistics results to derive exact closed-form expressions for the capture probability over independent and identically distributed Rayleigh fading channels. © 2010 IEEE.

  16. RA research reactor, Part 1, Operation and maintenance of the RA nuclear reactor for 1985

    International Nuclear Information System (INIS)

    Sotic, O.; Martinc, R.; Cupac, S.; Sulem, B.; Badrljica, R.; Majstorovic, D.; Sanovic, V.

    1985-01-01

    According to the plan, RA reactor was to be in operation in mid September 1985. But, since the building of the emergency cooling system, nor the reconstruction of the existing special ventilation system were not finished until the end of August reactor was not operated during 1985. During the previous four years reactor operation was limited by the temporary operating license issued by the Committee of Serbian ministry for health and social care, which was cancelled in August 1984. The reason was the non existing emergency cooling system and lack of appropriate filters in the special ventilation system. This temporary license has limited the reactor power to 2 MW from 1981-1984. Control and maintenance of the reactor instrumentation and tools was done regularly but dependent on the availability of the spare parts. In order to enable future reliable operation of the RA reactor, according to new licensing regulations, during 1984, three major tasks have started: building of the new emergency system, reconstruction of the existing ventilation system, and renewal of the reactor instrumentation. IAEA has approved the amount of 1,300,000 US dollars for the renewal of the instrumentation [sr

  17. Concentrations and activity ratios of 228Ra and 226Ra in surface seawater along the Pacific coast of Japan

    International Nuclear Information System (INIS)

    Ohta, T.; Mahara, Y.; Kubota, T.; Sato, J.; Gamo, T.

    2011-01-01

    We measured the 228 Ra/ 226 Ra activity ratios in surface seawater along the Pacific coast of Japan at five ports around the island of Izu-Oshima (n = 29), at Atami in Sagami Bay (n = 13), and at Umizuri Park in Tokyo Bay (n = 14). We also conducted these measurements along a transect from the open Pacific Ocean across the Kuroshio to the mouth of Tokyo Bay (n = 7). The activity ratios decreased with increasing salinity of the sampling sites. The 228 Ra/ 226 Ra activity ratios in surface seawater along the coast gradually decreased after at the end of autumn and were lowest in winter and the beginning of spring. The surface salinity along the coast decreased from summer into autumn and increased from winter to the beginning of spring. The activity ratios decreased with the increase of salinity. The variation in activity ratios at the three coastal sites is possibly caused by differing contributions of surface seawater from the Kuroshio and surrounding open ocean. The different patterns and ranges of variation in the 228 Ra/ 226 Ra activity ratios in surface seawater at Izu-Oshima, Atami, and Umizuri Park may reflect both the amount of water from the Kuroshio and vicinity, and the local bathymetry, because continental shelf sediment is the source of Ra isotopes in surface seawater. (orig.)

  18. Free diffusion of translation of macromolecules in solution with the rayleigh interferometer; Diffusion libre de translation des macromolecules en solution, par interferometrie de rayleigh

    Energy Technology Data Exchange (ETDEWEB)

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

    1969-07-01

    The aim of this study is to develop a rapid and accurate measurement, with the Rayleigh interferometer, of the free diffusion coefficient of translation of macromolecules in solution. After having explained the choice of a diffusion cell with laminar lateral flow, and explained the principle of the Rayleigh interferometer, a semi-automatic technique of free diffusion are then introduced. Solutions are proposed for systems composed of two or three components, such as biopolymers. The paper ends by drafting the possible treatment of recorded experimental data by means of electronic computer. (author) [French] Cette etude a ete entreprise pour mettre au point une methode precise et rapide de mesure, par interferometre de Rayleigh, du coefficient de diffusion libre de translation des macromolecules en solution. Apres avoir justifie le choix d'une cellule de diffusion a ecoulement laminaire lateral et explique le principe de l'interferometre de Rayleigh, l'auteur decrit une technique semi-automatique d'enregistrement des cliches d'interference. Il introduit ensuite les equations differentielles de diffusion libre et propose des solutions pour les systemes a deux et trois composants applicables aux biopolymeres. L'article se termine par une esquisse concernant le traitement des donnees experimentales enregistrees au moyen du calcul electronique. (auteur)

  19. Development of a liquid scintillation method for in vitro determination of 226Ra and 228 Ra in bioassay samples

    International Nuclear Information System (INIS)

    Fernandes, Paulo Cesar P.; Sousa, Wanderson O.; Juliao, Ligia M.Q.C.; Dantas, Bernardo M.

    2011-01-01

    Radium isotopes are dispersed in the environment according to their physicochemical characteristics. The intake of 226 Ra and 228 Ra in humans can occur by inhalation and ingestion and the risk of internal exposure are related to their long half-lives, characteristics of the emission and biokinetics of the isotopes in the human body. The goal of this work is to develop a methodology for the analysis of 226 Ra and 228 Ra in excreta samples (urine and feces), using liquid scintillation technique. Excreta samples were provided by non-exposed humans for the purpose of standardizing the methodology and the establishment of a background level of radium excretion. Radium isotopes were concentrated and separated from the constituents of the sample by co-precipitation with barium sulphate. The precipitate of Ba(Ra)SO 4 was filtrated and weighted for the determination of the chemical yield. The filter containing the precipitate was transferred to a scintillation vial. In the scintillation vial, 8 mL of water, 8 mL of Instagel XF and 4 mL of UltimaGold were added, forming a gel suspension, after stirring the solution. The 226 Ra and 228 Ra activities were determined 21 days after the precipitation of samples. The samples were counted in a liquid scintillation spectrometer. The technique presented adequate sensitivity and reproducibility for the analysis of urine and feces. The activities of 226 Ra and 228 Ra in excreta samples provide useful information for the identification of the main route of intake and for the assessment of the internal exposure of occupationally exposed workers and inhabitants of high background areas. (author)

  20. Ventilation system in the RA reactor building - design specifications

    International Nuclear Information System (INIS)

    Badrljica, R.

    1984-09-01

    Protective role of the ventilation system of nuclear facilities involve construction of ventilation barriers which prevent release of radioactive particulates or gases, elimination od radioactive particulates and gases from the air which is released from contaminated zones into the reactor environment. Ventilation barriers are created by dividing the building into a number of ventilation zones with different sub pressure compared to the atmospheric pressure. The RA reactor building is divided into four ventilation zones. First zone is the zone of highest risk. It includes reactor core with horizontal experimental channels, underground rooms of the primary coolant system (D 2 O), helium system, hot cells and the space above the the reactor core. Second zone is the reactor hall and the room for irradiated fuel storage. The third zone includes corridors in the basement, ground floor and first floor where the probability of contamination is small. The fourth zone includes the annex where the contamination risk is low. There is no have natural air circulation in the reactor building. Ventilators for air input and outlet maintain the sub pressure in the building (pressure lower than the atmospheric pressure). This prevents release of radioactivity into the atmosphere [sr

  1. Performance Characterization of RaPToRS Systems

    Science.gov (United States)

    Shibata, K.; Krieger, M.; Fallica, J.; Henchen, R.; Pogozelski, E.; Padalino, S.; SUNY Geneseo Collaboration; LaboratoryLaser Energetics at University of Rochester Collaboration

    2011-10-01

    The Rapid Pneumatic Transport of Radioactive Samples (RaPToRS) system can quickly and efficiently move radioactive materials from their activation site to a counting station. Facilities such as the NIF and LLE are considering these systems while NRL is currently using one. The system is essentially a 10 cm diameter pneumatic tube with a cylindrical sample carrier. The performance of the system depends on many factors, including the mass of the carrier, length of the tube, angle and difference in height of the tube's endpoints, the carrier's physical design, and the number, type, and distribution of blowers attached to the tube. These factors have been systematically examined to develop the fastest and most reliable system. The most significant factors are the mass and the vertical travel of the carrier. When the carrier mass is low, moving air supports the carrier in the tube, resulting in low friction. The terminal velocity ranges from 13.5 to 2.5 m/s for masses varying from 1 kg to 3 kg. Using a single 1100 W blower, the initial force exerted on the carrier was 11.3 N. This work was supported in part by the US Department of Energy through the LLE.

  2. Diode Laser Velocity Measurements by Modulated Filtered Rayleigh Scattering

    Science.gov (United States)

    Mach, J. J.; Varghese, P. L.; Jagodzinski, J. J.

    1999-01-01

    The ability of solid-state lasers to be tuned in operating frequency at MHz rates by input current modulation, while maintaining a relatively narrow line-width, has made them useful for spectroscopic measurements. Their other advantages include low cost, reliability, durability, compact size, and modest power requirements, making them a good choice for a laser source in micro-gravity experiments in drop-towers and in flight. For their size, they are also very bright. In a filtered Rayleigh scattering (FRS) experiment, a diode laser can be used to scan across an atomic or molecular absorption line, generating large changes in transmission at the resonances for very small changes in frequency. The hyperfine structure components of atomic lines of alkali metal vapors are closely spaced and very strong, which makes such atomic filters excellent candidates for sensitive Doppler shift detection and therefore for high-resolution velocimetry. In the work we describe here we use a Rubidium vapor filter, and work with the strong D(sub 2) transitions at 780 nm that are conveniently accessed by near infrared diode lasers. The low power output of infrared laser diodes is their primary drawback relative to other laser systems commonly used for velocimetry. However, the capability to modulate the laser frequency rapidly and continuously helps mitigate this. Using modulation spectroscopy and a heterodyne detection scheme with a lock-in amplifier, one can extract sub-microvolt signals occurring at a specific frequency from a background that is orders of magnitude stronger. The diode laser modulation is simply achieved by adding a small current modulation to the laser bias current. It may also be swept repetitively in wavelength using an additional lower frequency current ramp.

  3. Rayleigh-Taylor instability in inertial confinement fusion

    International Nuclear Information System (INIS)

    Gupta, N.K.

    1987-01-01

    This report summarises the main results of theoretical analysis on the problem of Rayleigh-Tylor instability in inertial confinement fusion (ICF). Work presented in this report essentially covers four basic problems. Firstly, an analytical formulation to analyse the effects of plasma density inhomogeneities on the growth of the instability in plane geometry is presented. As a result of this analysis it is concluded that, for minimizing the growth rate of the instability, it may be advantageous to use the driver laser beams of higher irradiance and an optimum wave length in an ICF experiment. Secondly, a new formulation for the analysis of the instability in curved (cylindrical and spherical) geometries is presented. A general eigenvalue equation for the growth rate of the instability which is applicable for both plane and curved geometries is derived. A comparative study is made between the plane, cylindrical and spherical geometries. Also analytical expressions for the growth rates are obtained in the cases of spherical and cylindrical shell targets and their variations with respect to the aspect ratios of the shells are discussed. Thirdly, a semi-analytical analysis of the instability where the growth rate is obtained by solving numerically a (2N-1)x(2N-1) determinantal equation is presented. The semi-analytical analysis developed is applicable for the study of the growth of the instability in the present day multi-structured spherical shell targets. Finally, a dynamic analysis of the growth of the instability for a representative spherical solid target driven by laser beams symmetrically from all the sides is carried out numerically using a computer code developed for this purpose. This study confirms analytical predictions. Further, it is observed that an approximate analytical analysis with time independent density profile gives conservative estimates for the growth rate. In passing, the computer code is also used to estimate the pellet gain for spin

  4. The rapid mode of calcium uptake into heart mitochondria (RaM): comparison to RaM in liver mitochondria.

    Science.gov (United States)

    Buntinas, L; Gunter, K K; Sparagna, G C; Gunter, T E

    2001-04-02

    A mechanism of Ca(2+) uptake, capable of sequestering significant amounts of Ca(2+) from cytosolic Ca(2+) pulses, has previously been identified in liver mitochondria. This mechanism, the Rapid Mode of Ca(2+) uptake (RaM), was shown to sequester Ca(2+) very rapidly at the beginning of each pulse in a sequence [Sparagna et al. (1995) J. Biol. Chem. 270, 27510-27515]. The existence and properties of RaM in heart mitochondria, however, are unknown and are the basis for this study. We show that RaM functions in heart mitochondria with some of the characteristics of RaM in liver, but its activation and inhibition are quite different. It is feasible that these differences represent different physiological adaptations in these two tissues. In both tissues, RaM is highly conductive at the beginning of a Ca(2+) pulse, but is inhibited by the rising [Ca(2+)] of the pulse itself. In heart mitochondria, the time required at low [Ca(2+)] to reestablish high Ca(2+) conductivity via RaM i.e. the 'resetting time' of RaM is much longer than in liver. RaM in liver mitochondria is strongly activated by spermine, activated by ATP or GTP and unaffected by ADP and AMP. In heart, RaM is activated much less strongly by spermine and unaffected by ATP or GTP. RaM in heart is strongly inhibited by AMP and has a biphasic response to ADP; it is activated at low concentrations and inhibited at high concentrations. Finally, an hypothesis consistent with the data and characteristics of liver and heart is presented to explain how RaM may function to control the rate of oxidative phosphorylation in each tissue. Under this hypothesis, RaM functions to create a brief, high free Ca(2+) concentration inside mitochondria which may activate intramitochondrial metabolic reactions with relatively small amounts of Ca(2+) uptake. This hypothesis is consistent with the view that intramitochondrial [Ca(2+)] may be used to control the rate of ADP phosphorylation in such a way as to minimize the probability of

  5. Seasonal changes in submarine groundwater discharge to coastal salt ponds estimated using 226Ra and 228Ra as tracers

    Science.gov (United States)

    Hougham, A.L.; Moran, S.B.; Masterson, J.P.; Kelly, R.P.

    2008-01-01

    Submarine groundwater discharge (SGD) to coastal southern Rhode Island was estimated from measurements of the naturally-occurring radioisotopes 226Ra (t1/2 = 1600??y) and 228Ra (t1/2 = 5.75??y). Surface water and porewater samples were collected quarterly in Winnapaug, Quonochontaug, Ninigret, Green Hill, and Pt. Judith-Potter Ponds, as well as nearly monthly in the surface water of Rhode Island Sound, from January 2002 to August 2003; additional porewater samples were collected in August 2005. Surface water activities ranged from 12-83??dpm 100??L- 1 (60??dpm = 1??Bq) and 21-256??dpm 100??L- 1 for 226Ra and 228Ra, respectively. Porewater 226Ra activities ranged from 16-736??dpm 100??L- 1 (2002-2003) and 95-815??dpm 100??L- 1 (2005), while porewater 228Ra activities ranged from 23-1265??dpm 100??L- 1. Combining these data with a simple box model provided average 226Ra-based submarine groundwater fluxes ranging from 11-159??L m- 2 d- 1 and average 228Ra-derived fluxes of 15-259??L m- 2 d- 1. Seasonal changes in Ra-derived SGD were apparent in all ponds as well as between ponds, with SGD values of 30-472??L m- 2 d- 1 (Winnapaug Pond), 6-20??L m- 2 d- 1 (Quonochontaug Pond), 36-273??L m- 2 d- 1 (Ninigret Pond), 29-76??L m- 2 d- 1 (Green Hill Pond), and 19-83??L m- 2 d- 1 (Pt. Judith-Potter Pond). These Ra-derived fluxes are up to two orders of magnitude higher than results predicted by a numerical model of groundwater flow, estimates of aquifer recharge for the study period, and values published in previous Ra-based SGD studies in Rhode Island. This disparity may result from differences in the type of flow (recirculated seawater versus fresh groundwater) determined using each technique, as well as variability in porewater Ra activity. ?? 2007 Elsevier B.V. All rights reserved.

  6. High Ra, high Pr convection with viscosity gradients

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. High Ra, high Pr convection with viscosity gradients. Weak upward flow through mesh. Top fluid more viscous. Unstable layer Instability Convection.

  7. The distribution of 226Ra in the Atlantic Ocean

    International Nuclear Information System (INIS)

    Broecker, W.S.; Goddard, J.; Sarmiento, J.L.

    1976-01-01

    Based on results obtained during the GEOSECS program the primary features of the distribution of 226 Ra in the Atlantic Ocean can be defined. Outside the Antarctic no significant variation has been found in the 226 Ra content of surface waters. Eighty samples yield an average of 7.4 dpm/100 kg (normalized to a salinity of 35.00%). Deep waters in the central Atlantic have 226 Ra contents several dpm/100 kg higher than expected from the mixing of Antarctic Bottom Water (21.3 dpm/100 kg) and basal North Atlantic Deep Water (10.3 dpm/100 kg). These excesses correlate well with deficiencies in O 2 and excesses in SiO 2 . The intermediate water 226 Ra maximum in the South Atlantic is associated with the inflow of low-oxygen Circumpolar Intermediate Water beneath the Antarctic Intermediate Water. (Auth.)

  8. Tehnikaromud saab peagi tasuta ära anda / Urmas Tooming

    Index Scriptorium Estoniae

    Tooming, Urmas

    2005-01-01

    13. augustist saab vana elektroonikat tasuta ära anda. MTÜ Eesti Elektroonikaromu on juba loonud selleks üle Eesti 44 kogumispunkti, EES-Ringlus ühingus endale konkurenti ei näe. Lisa: Vana tehnika

  9. 226Ra adsorption on active coals from waste waters

    International Nuclear Information System (INIS)

    Panturu, E.; Georgescu, D.P.; Serban, N.; Filip, D.; Radulescu, R.

    2000-01-01

    During the mining and extraction of uranium, the principle means of protection measurement is to prevent uranium and its products diffusing into the environment. The main carriers of radioactive elements in the environment are air and water. Therefore, reduction of the pollution at a uranium mine can be achieved by the treatment of waste waters contaminated with 226 Ra Radium contaminated waste waters represent a major biological risk. This paper presents the results of the study of the sorption of 226 Ra on active coal mechanisme and the influence of the physical and chemical characteristics of fluid. The 226 Ra removal from the residue pond water at the uranium ore processing plant was studied using eight types of indigenous active coals. The experimental results for each type of active coal and their effect on removal of 226 Ra from waste waters are presented in this paper. (author)

  10. Radiosensitivity and thermoresistance of rat RA-2 rhabdomyosarcoma cells

    International Nuclear Information System (INIS)

    Fedorova, E.V.; Trusova, V.D.; Vakhtin, Yu.B.

    1990-01-01

    The data obtained show that clonogenic RA-2T cells are 2-3 times more thermoresistant than clonogenic cells of the original thermosensitive RA-2T strain as estimated by D 0 value upon heating up to 43-45 deg C. After X-irradiation of rat rhabdomyosarcoma, a decrease in the capacity of forming pulmonary colonies is more pronounced in cells of the thermosensitive RA-2 strain cells than in those of the thermoresistant strain RA-2T (D 0 =1.6 Gy and D 0 =2.4 Gy, respectively). In all appearance, within one and the same tumor cell population, the hereditarily thermoresistant cells are more radioresistant than the thermosensitive ones

  11. MSFIA-LOV system for {sup 226}Ra isolation and pre-concentration from water samples previous radiometric detection

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, Rogelio [Environmental Radioactivity Laboratory (LaboRA), University of the Balearic Islands, Cra. Valldemossa km 7.5, 07122, Palma (Spain); Environment and Energy Department, Advanced Materials Research Center (CIMAV) S.C., Miguel de Cervantes 120, Chihuahua, Chih. 31136 (Mexico); Borràs, Antoni [Environmental Radioactivity Laboratory (LaboRA), University of the Balearic Islands, Cra. Valldemossa km 7.5, 07122, Palma (Spain); Leal, Luz [Environment and Energy Department, Advanced Materials Research Center (CIMAV) S.C., Miguel de Cervantes 120, Chihuahua, Chih. 31136 (Mexico); Cerdà, Víctor [Department of Chemistry, University of the Balearic Islands, Cra. Valldemossa km 7.5, 07122, Palma (Spain); Ferrer, Laura, E-mail: laura.ferrer@uib.es [Environmental Radioactivity Laboratory (LaboRA), University of the Balearic Islands, Cra. Valldemossa km 7.5, 07122, Palma (Spain)

    2016-03-10

    An automatic system based on multisyringe flow injection analysis (MSFIA) and lab-on-valve (LOV) flow techniques for separation and pre-concentration of {sup 226}Ra from drinking and natural water samples has been developed. The analytical protocol combines two different procedures: the Ra adsorption on MnO{sub 2} and the BaSO{sub 4} co-precipitation, achieving more selectivity especially in water samples with low radium levels. Radium is adsorbed on MnO{sub 2} deposited on macroporous of bead cellulose. Then, it is eluted with hydroxylamine to transform insoluble MnO{sub 2} to soluble Mn(II) thus freeing Ra, which is then coprecipitated with BaSO{sub 4}. The {sup 226}Ra can be directly detected in off-line mode using a low background proportional counter (LBPC) or through a liquid scintillation counter (LSC), after performing an on-line coprecipitate dissolution. Thus, the versatility of the proposed system allows the selection of the radiometric detection technique depending on the detector availability or the required response efficiency (sample number vs. response time and limit of detection). The MSFIA-LOV system improves the precision (1.7% RSD), and the extraction frequency (up to 3 h{sup −1}). Besides, it has been satisfactorily applied to different types of water matrices (tap, mineral, well and sea water). The {sup 226}Ra minimum detectable activities (LSC: 0.004 Bq L{sup −1}; LBPC: 0.02 Bq L{sup −1}) attained by this system allow to reach the guidance values proposed by the relevant international agencies e.g. WHO, EPA and EC. - Highlights: • Automatic, rapid and selective method for {sup 226}Ra extraction/pre-concentration from water. • MSFIA-LOV system performs a sample clean-up prior to {sup 226}Ra radiometric detection. • {sup 226}Ra sample preparation allows using two radiometric detectors (LBPC and LSC). • Environmental levels of {sup 226}Ra are easily quantified. • High sensitivity and selectivity are achieved, reaching the

  12. RA reactor operation and maintenance in 1992, Part 1

    International Nuclear Information System (INIS)

    Sotic, O.; Cupac, S.; Sulem, B.; Zivotic, Z.; Majstorovic, D.; Tanaskovic, M.

    1992-01-01

    During 1992 Ra reactor was not in operation. All the activities were fulfilled according to the previously adopted plan. Basic activities were concerned with revitalisation of the RA reactor and maintenance of reactor components. All the reactor personnel was busy with reconstruction and renewal of the existing reactor systems and building of the new systems, maintenance of the reactor devices. Part of the staff was trained for relevant tasks and maintenance of reactor systems [sr

  13. 226Ra bioavailability of plants at urgeirica uranium mill tailings

    International Nuclear Information System (INIS)

    Madruga, M.J.; Brogueira, A.

    2002-01-01

    Large amounts of solid wastes (tailings) resulting from the exploitation and treatment of uranium ore at the Urgeirica mine (north of Portugal) have been accumulated in dams (tailing ponds). To reduce the dispersion of natural radionuclides into the environment some dams were revegetated with eucalyptus (Eucalyptus globolus) and pines (Pinus pinea). Besides, some shrubs (Cytisus s.p.) are growing at some of the dams. The objective of this study is to determine the 226 Ra bioavailability from uranium mill tailings through the quantification of the total and available fraction of radium in the solid wastes and to estimate its transfer to the plants growing on the tailing piles. Plants and solid waste samples were randomly collected at dams. Activity concentration of 226 Ra in plants (aerial part and roots) and solid wastes were measured by gamma spectrometry. The exchangeable fraction of radium in solid wastes was quantified using one single step extraction with 1 mol dm -3 ammonium acetate (pH=7) or 1 mol dm -3 calcium chloride solutions. The results obtained for the 226 Ra uptake by plants show that 226 Ra concentration ratios for eucalyptus and pines decrease at low 226 Ra concentration in the solid wastes and appear relatively constant at higher radium concentrations. For shrubs, the concentration ratios increase at higher 226 Ra solid waste concentrations approaching a saturation value. Percentage values of 16.0±8.3 and 12.9±8.9, for the fraction of radium extracted from the solid wastes, using 1 mol dm -3 ammonium acetate or calcium chloride solutions respectively, were obtained. The 226 Ra concentration ratios determined on the basis of exchangeable radium are one order of magnitude higher than those based on total radium. It can be concluded that, within the standard error values, more consistent 226 Ra concentration ratios were obtained when calculated on the basis of available radium than when total radium was considered, for all the dams. (author)

  14. RA Research nuclear reactor, Part II - radiation protection at the RA nuclear reactor in 1984; Istrazivacki nuklearni reaktor RA - Deo II - zastita od zracenja kod nuklearnog reaktora RA u 1984. godini

    Energy Technology Data Exchange (ETDEWEB)

    Ninkovic, M; Ajdacic, N; Zaric, M; Vukovic, Z [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1984-12-15

    Radon protection tasks which enable safe operation of the RA reactor, and are defined according the the legal regulations and IAEA safety recommendations are sorted into four categories in this report: (1) Control of the working environment, dosimetry at the RA reactor; (2) Radioactivity control in the vicinity of the reactor and meteorology measurements; (3) Collecting and treatment of fluid effluents; and (4) radioactive wastes, decontamination and actions. Each category is described as a separate annex of this report.

  15. On the octupole deformation in Ra-Th region

    International Nuclear Information System (INIS)

    Rozmej, P.; Boening, K.; Sobiczewski, A.

    1986-03-01

    The problem of the existence of a stable octupole deformation in Ra-Th region has been reinvestigated using a Nilsson single-particle potential with a newly fitted set of parameters, which reproduce the spins of the ground states of odd-A nuclei. In the energy surfaces, calculated for 222 Ra and 222 Th, the octupole deformed minima, separated by the barriers of 150 KeV and 210 keV, respectively, have been obtained. (orig.)

  16. Radioactive decay of 223Ra by 14C emission

    International Nuclear Information System (INIS)

    Yashita, S.; Gregorich, K.; Ghiorso, A.

    1985-01-01

    Recently H.J. Rose and G.A. Jones at the University of Oxford reported the very difficult observation of an exotic radioactive decay mode in 233 Ra, its spontaneous disintegration by the emission of 14 C particles. The authors have confirmed their somewhat surprising discovery by an independent method. Within the present experimental accuracy the magnetic rigidity, energy and branching ratio support the assignment of 14 C emission from 223 Ra as proposed by the Oxford experiment

  17. Kinetic parameters of the RB and RA reactors

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, M; Obradovic, D [Institute of nuclear sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

    1965-12-15

    In the paper the expressions for transfer functions of the zero power reactors, as well as power reactors of the RA reactor type are given, based on the space independent model. The modulation method for reactor transfer function measurements is explained. The results of the measurement and interpretation are given. The measurement were done on the RB and RA reactors in 'Boris Kidrich' Institute for Nuclear Sciences in Vincha (author)

  18. Rayleigh-Taylor instability and mushroom-pattern formation in a two-component Bose-Einstein condensate

    International Nuclear Information System (INIS)

    Sasaki, Kazuki; Suzuki, Naoya; Saito, Hiroki; Akamatsu, Daisuke

    2009-01-01

    The Rayleigh-Taylor instability at the interface in an immiscible two-component Bose-Einstein condensate is investigated using the mean field and Bogoliubov theories. Rayleigh-Taylor fingers are found to grow from the interface and mushroom patterns are formed. Quantized vortex rings and vortex lines are then generated around the mushrooms. The Rayleigh-Taylor instability and mushroom-pattern formation can be observed in a trapped system.

  19. Therapy palliative with {sup 2}23Ra without special radiation protection measures?; Palliative Therapie mit {sup 223}Ra ohne besondere Strahlenschutzmassnahmen?

    Energy Technology Data Exchange (ETDEWEB)

    Just, Guenther [Forschungsbuero Radonbalneologie (FRB), Grosspoesna (Germany); Petzold, Juergen

    2015-07-01

    For nearly 2 years now as a therapy of the castration resistant prostata carcinoma a nuclide therapy with {sup 223}Ra-Dichloride (trade-mark Xofigo) is applied. Xofigo is applied by a medical specialist for nuclear medicine altogether 6 times in a monthly distance. The activity used in each case is according to the body weight (50 kBq/kg BW). This therapy is licensed by the supervisory authorities of the German federal countries as an ambulant therapy. Special radiation protection measures are only required when exceeding a given number of 17 patients per year as incorparation measurements.

  20. Effective 226Ra-content of some Hungarian building materials

    International Nuclear Information System (INIS)

    Toth, A.; Feher, I.

    1976-01-01

    The aim of the work was to analyse the effective 226 Ra content of building- and back filling materials used in Hungary. The quantity of radon was determined by ionization chambers connected to vibrating-reed electrometers, as well as by a scintillation radon counter. The radon measuring instruments were calibrated by known 222 Rn quantities given off from standard RaCl 2 solutions. The overall uncertainty of the data obtained is estimated as being 25%. The minimum measurable effective 226 Ra concentration due to a 10 4 g building material source is calculated as 16 fCi/g for the ionization chambers and 8 fCi/g for the scintillation counter. 68 building material samples and 11 backfill (concrete made by fly-ashes) samples have been studied and it has been found, that the effective 226 Ra contents of the tested building materials are 2 to 9 times greater than those found in the Soviet Union though none exceeds the recommended 600 fCi/g level. Among the back filling materials made with fly-ash the maximum 226 Ra content was 3300 fCi/g. The effective 226 Ra content measurements are well suited for a priori radon escape qualification of building materials. (K.A.)