WorldWideScience

Sample records for stratified stability decreases

  1. RADIAL STABILITY IN STRATIFIED STARS

    International Nuclear Information System (INIS)

    Pereira, Jonas P.; Rueda, Jorge A.

    2015-01-01

    We formulate within a generalized distributional approach the treatment of the stability against radial perturbations for both neutral and charged stratified stars in Newtonian and Einstein's gravity. We obtain from this approach the boundary conditions connecting any two phases within a star and underline its relevance for realistic models of compact stars with phase transitions, owing to the modification of the star's set of eigenmodes with respect to the continuous case

  2. Stability of unstably stratified shear flow between parallel plates

    Energy Technology Data Exchange (ETDEWEB)

    Fujimura, Kaoru; Kelly, R E

    1987-09-01

    The linear stability of unstably stratified shear flows between two horizontal parallel plates was investigated. Eigenvalue problems were solved numerically by making use of the expansion method in Chebyshev polynomials, and the critical Rayleigh numbers were obtained accurately in the Reynolds number range of (0.01, 100). It was found that the critical Rayleigh number increases with an increase of the Reynolds number. The result strongly supports previous stability analyses except for the analysis by Makino and Ishikawa (J. Jpn. Soc. Fluid Mech. 4 (1985) 148 - 158) in which a decrease of the critical Rayleigh number was obtained.

  3. Stability of unstably stratified shear flow between parallel plates

    International Nuclear Information System (INIS)

    Fujimura, Kaoru; Kelly, R.E.

    1987-01-01

    The linear stability of unstably stratified shear flows between two horizontal parallel plates was investigated. Eigenvalue problems were solved numerically by making use of the expansion method in Chebyshev polynomials, and the critical Rayleigh numbers were obtained accurately in the Reynolds number range of [0.01, 100]. It was found that the critical Rayleigh number increases with an increase of the Reynolds number. The result strongly supports previous stability analyses except for the analysis by Makino and Ishikawa [J. Jpn. Soc. Fluid Mech. 4 (1985) 148 - 158] in which a decrease of the critical Rayleigh number was obtained. (author)

  4. Stability of Miscible Displacements Across Stratified Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Shariati, Maryam; Yortsos, Yanis C.

    2000-09-11

    This report studied macro-scale heterogeneity effects. Reflecting on their importance, current simulation practices of flow and displacement in porous media were invariably based on heterogeneous permeability fields. Here, it was focused on a specific aspect of such problems, namely the stability of miscible displacements in stratified porous media, where the displacement is perpendicular to the direction of stratification.

  5. Hydromagnetic stability of rotating stratified compressible fluid flows

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, V; Kandaswamy, P [Dept. of Mathematics, Bharathiar University, Coimbatore, Tamil Nadu, India; Debnath, L [Dept. of Mathematics, University of Central Florida, Orlando, USA

    1984-09-01

    The hydromagnetic stability of a radially stratified compressible fluid rotating between two coaxial cylinders is investigated. The stability with respect to axisymmetric disturbances is examined. The fluid system is found to be thoroughly stable to axisymmetric disturbances provided the fluid rotates very rapidly. The system is shown to be unstable to non-axisymmetric disturbances, and the slow amplifying hydromagnetic wave modes propagate against the basic rotation. The lower and upper bounds of the azimuthal phase speeds of the amplifying waves are determined. A quadrant theorem on the slow waves characteristic of a rapidly rotating fluid is derived. Special attention is given to the effects of compressibility of the fluid. Some results concerning the stability of an incompressible fluid system are obtained as special cases of the present analysis.

  6. Linear and nonlinear stability of a thermally stratified magnetically driven rotating flow in a cylinder.

    Science.gov (United States)

    Grants, Ilmars; Gerbeth, Gunter

    2010-07-01

    The stability of a thermally stratified liquid metal flow is considered numerically. The flow is driven by a rotating magnetic field in a cylinder heated from above and cooled from below. The stable thermal stratification turns out to destabilize the flow. This is explained by the fact that a stable stratification suppresses the secondary meridional flow, thus indirectly enhancing the primary rotation. The instability in the form of Taylor-Görtler rolls is consequently promoted. These rolls can only be excited by finite disturbances in the isothermal flow. A sufficiently strong thermal stratification transforms this nonlinear bypass instability into a linear one reducing, thus, the critical value of the magnetic driving force. A weaker temperature gradient delays the linear instability but makes the bypass transition more likely. We quantify the non-normal and nonlinear components of this transition by direct numerical simulation of the flow response to noise. It is observed that the flow sensitivity to finite disturbances increases considerably under the action of a stable thermal stratification. The capabilities of the random forcing approach to identify disconnected coherent states in a general case are discussed.

  7. Electrohydrodynamic stability of two stratified power law liquid in couette flow

    International Nuclear Information System (INIS)

    Eldabe, N.T.

    1988-01-01

    Consideration is given to the stability of the flow of two power law liquids under the influence of normal electric field between two infinite parallel planes when one of the planes moves with constant velocity in its own plane. It is found that the electric fields have a dramatic effect and can be chosen to stabilize or destabilize the flow. The effects of the power law parameters on the problem are examinated

  8. Decreased stability of DNA in cells treated with alkylating agents

    Energy Technology Data Exchange (ETDEWEB)

    Frankfurt, O.S. (Cedars Medical Center, Miami, FL (United States))

    1990-12-01

    A modified highly sensitive procedure for the evaluation of DNA damage in individual cells treated with alkylating agents is reported. The new methodology is based on the amplification of single-strandedness in alkylated DNA by heating in the presence of Mg{sup 2+}. Human ovarian carcinoma cells A2780 were treated with nitrogen mustard (HN2), fixed in methanol, and stained with monoclonal antibody (MOAB) F7-26 generated against HN2-treated DNA. Binding of MOAB was measured by flow cytometry with indirect immunofluorescence. Intensive binding of MOAB to control and drug-treated cells was observed after heating in Tris buffer supplemented with MgCl{sub 2}. Thus, the presence of phosphates and MgCl{sub 2} during heating was necessary for the detection of HN2-induced changes in DNA stability. Fluorescence of HN2-treated cells decreased to background levels after treatment with single-strand-specific S{sub 1} nuclease. MOAB F7-26 interacted with single-stranded regions in DNA and did not bind to dsDNA or other cellular antigens. It is suggested that alkylation of guanines decreased the stability of the DNA molecule and increased the access of MOAB F7-26 to deoxycytidines on the opposite DNA strand.

  9. Transformation of vortex structures in the wake of a sphere moving in the stratified fluid with decreasing of internal Froude number

    International Nuclear Information System (INIS)

    Matyushin, Pavel; Gushchin, Valentin

    2011-01-01

    The 3D separated, density stratified viscous fluid flows around a sphere are investigated by means of the direct numerical simulation (DNS) on the basis of the Navier-Stokes equations in the Boussinesq approximation on the supercomputers at the wide range of internal Froude (Fr) and Reynolds (Re) numbers. For DNS the Splitting on physical factors Method for Incompressible Fluid flows (SMIF) with the hybrid explicit finite difference scheme (second-order accuracy in space, minimum scheme viscosity and dispersion, monotonous) has been used. At Fr > 10 with increasing of Re we observed the flow regimes of the homogeneous viscous fluid (including the laminar-turbulent transition in the boundary layer on the sphere). With decreasing of Fr at Re < 500 the strong transformation of vortex structures in the sphere wake is demonstrated by means of the β – visualization. Thus the refined classification of the flow regimes around a sphere moving in the viscous stratified fluid is presented.

  10. Convective plasma stability consistent with MHD equilibrium in magnetic confinement systems with a decreasing field

    International Nuclear Information System (INIS)

    Tsventoukh, M. M.

    2010-01-01

    A study is made of the convective (interchange, or flute) plasma stability consistent with equilibrium in magnetic confinement systems with a magnetic field decreasing outward and large curvature of magnetic field lines. Algorithms are developed which calculate convective plasma stability from the Kruskal-Oberman kinetic criterion and in which the convective stability is iteratively consistent with MHD equilibrium for a given pressure and a given type of anisotropy in actual magnetic geometry. Vacuum and equilibrium convectively stable configurations in systems with a decreasing, highly curved magnetic field are calculated. It is shown that, in convectively stable equilibrium, the possibility of achieving high plasma pressures in the central region is restricted either by the expansion of the separatrix (when there are large regions of a weak magnetic field) or by the filamentation of the gradient plasma current (when there are small regions of a weak magnetic field, in which case the pressure drops mainly near the separatrix). It is found that, from the standpoint of equilibrium and of the onset of nonpotential ballooning modes, a kinetic description of convective stability yields better plasma confinement parameters in systems with a decreasing, highly curved magnetic field than a simpler MHD model and makes it possible to substantially improve the confinement parameters for a given type of anisotropy. For the Magnetor experimental compact device, the maximum central pressure consistent with equilibrium and stability is calculated to be as high as β ∼ 30%. It is shown that, for the anisotropy of the distribution function that is typical of a background ECR plasma, the limiting pressure gradient is about two times steeper than that for an isotropic plasma. From a practical point of view, the possibility is demonstrated of achieving better confinement parameters of a hot collisionless plasma in systems with a decreasing, highly curved magnetic field than those

  11. Modeling Nitrogen Decrease in Water Lettuce Ponds from Waste Stabilization Ponds

    Science.gov (United States)

    Putri, Gitta Agnes; Sunarsih

    2018-02-01

    This paper presents about the dynamic modeling of the Water Lettuce ponds as a form of improvement from the Water Hyacinth ponds. The purpose of this paper is to predict nitrogen decrease and nitrogen transformation in Water Lettuce ponds integrated with Waste Stabilization Ponds. The model consists of 4 mass balances, namely Dissolved Organic Nitrogen (DON), Particulate Organic Nitrogen (PON), ammonium (NH4+), Nitrate and Nitrite (NOx). The process of nitrogen transformation which considered in a Water Lettuce ponds, namely hydrolysis, mineralization, nitrification, denitrification, plant and bacterial uptake processes. Numerical simulations are performed by giving the values of parameters and the initial values of nitrogen compounds based on a review of previous studies. Numerical results show that the rate of change in the concentration of nitrogen compounds in the integration ponds of waste stabilization and water lettuce decreases and reaches stable at different times.

  12. Mast cell stabilization decreases cardiomyocyte and LV function in dogs with isolated mitral regurgitation.

    Science.gov (United States)

    Pat, Betty; Killingsworth, Cheryl; Chen, Yuanwen; Gladden, James D; Walcott, Greg; Powell, Pamela C; Denney, Thomas; Gupta, Himanshu; Desai, Ravi; Tillson, Michael; Dillon, A Ray; Dell'italia, Louis J

    2010-09-01

    Mast cells are increased in isolated mitral regurgitation (MR) in the dog and may mediate extracellular matrix loss and left ventricular (LV) dilatation. We tested the hypothesis that mast cell stabilization would attenuate LV remodeling and improve function in the MR dog. MR was induced in adult dogs randomized to no treatment (MR, n = 5) or to the mast cell stabilizer, ketotifen (MR + MCS, n = 4) for 4 months. LV hemodynamics were obtained at baseline and after 4 months of MR and magnetic resonance imaging (MRI) was performed at sacrifice. MRI-derived, serial, short-axis LV end-diastolic (ED) and end-systolic (ES) volumes, LVED volume/mass ratio, and LV 3-dimensional radius/wall thickness were increased in MR and MR + MCS dogs compared with normal dogs (n = 6) (P < .05). Interstitial collagen was decreased by 30% in both MR and MR + MCS versus normal dogs (P < .05). LV contractility by LV maximum time-varying elastance was significantly depressed in MR and MR + MCS dogs. Furthermore, cardiomyocyte fractional shortening was decreased in MR versus normal dogs and further depressed in MR + MCS dogs (P < .05). In vitro administration of ketotifen to normal cardiomyocytes also significantly decreased fractional shortening and calcium transients. Chronic mast cell stabilization did not attenuate eccentric LV remodeling or collagen loss in MR. However, MCS therapy had a detrimental effect on LV function because of a direct negative inotropic effect on cardiomyocyte function. Published by Elsevier Inc.

  13. Encapsulation and Nano-Encapsulation of Papain Active Sites to Enhance Radiolityc Stability and Decrease Toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Lugão, A. B.; Varca, G. H.C.; Paiffer, F.; Mathor, M. B.; Lopes, P. S.; Rogero, S.; Rogero, J. R. [Comissão Nacional de Energia Nuclear (CNEN), Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo (Brazil)

    2009-07-01

    Papain is used as an ingredient in various enzymatic debridement preparations. Those paste-like preparations are based on water solution and usually are sterilized by radiation. As a consequence, there is a major decrease in papain activity. Papain containing preparations are used in chronic wounds treatment in order to clean and remove the necrotic tissue. However FDA (2008) is taking an action against such products due to severe adverse events reported in patients which were submitted to papain treatments. Thus, the main goal of this proposal is to develop encapsulated papain containing membranes based on hydrogels and silicone rubber in an attempt to achieve a controllable distribution of size and delivery profile, a toxicity reduction and provide stability towards radiation processing through nanoencapsulation with cyclodextrins, which may also provide protection to the enzyme against radiation induced radiolysis. (author)

  14. Encapsulation and Nano-Encapsulation of Papain Active Sites to Enhance Radiolityc Stability and Decrease Toxicity

    International Nuclear Information System (INIS)

    Lugão, A.B.; Varca, G.H.C.; Paiffer, F.; Mathor, M.B.; Lopes, P.S.; Rogero, S.; Rogero, J.R.

    2009-01-01

    Papain is used as an ingredient in various enzymatic debridement preparations. Those paste-like preparations are based on water solution and usually are sterilized by radiation. As a consequence, there is a major decrease in papain activity. Papain containing preparations are used in chronic wounds treatment in order to clean and remove the necrotic tissue. However FDA (2008) is taking an action against such products due to severe adverse events reported in patients which were submitted to papain treatments. Thus, the main goal of this proposal is to develop encapsulated papain containing membranes based on hydrogels and silicone rubber in an attempt to achieve a controllable distribution of size and delivery profile, a toxicity reduction and provide stability towards radiation processing through nanoencapsulation with cyclodextrins, which may also provide protection to the enzyme against radiation induced radiolysis. (author)

  15. Encapsulation and Nano-Encapsulation of Papain Active Sites to Enhance Radiolityc Stability and Decrease Toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Lugão, A. B.; Varca, G. H.C.; Mathor, M. B.; Santos Lopes, P.; Rogero, M. S.S.; Rogero, J.R., E-mail: ablugao@ipen.br [Comissão Nacional de Energia Nuclear (CNEN), Instituto de Pesquisas Energeticas e Nucleares (IPEN), Av. Prof. Lineu Prestes, 2242 Cidade Universitaria, 05508-000 Sao Paulo (Brazil)

    2010-07-01

    Papain is used as an ingredient in various enzymatic debridement preparations. Those paste-like preparations are based on water solution and usually are sterilized by radiation. As a consequence, there is a major decrease in papain activity. Papain containing preparations are used in chronic wounds treatment in order to clean and remove the necrotic tissue. However FDA (2008) is taking an action against such products due to severe adverse events reported in patients submitted to papain treatments. Thus, the main goal of this proposal is to develop encapsulated papain containing membranes based on hydrogels and silicone rubber in an attempt to achieve a controllable distribution of size and delivery profile, a toxicity reduction and provide stability towards radiation processing through molecular encapsulation with β-cyclodextrin, which may also provide protection to the enzyme against radiation induced radiolysis. (author)

  16. Encapsulation and Nano-Encapsulation of Papain Active Sites to Enhance Radiolityc Stability and Decrease Toxicity

    International Nuclear Information System (INIS)

    Lugão, A.B.; Varca, G.H.C.; Mathor, M.B.; Santos Lopes, P.; Rogero, M.S.S.; Rogero, J.R.

    2010-01-01

    Papain is used as an ingredient in various enzymatic debridement preparations. Those paste-like preparations are based on water solution and usually are sterilized by radiation. As a consequence, there is a major decrease in papain activity. Papain containing preparations are used in chronic wounds treatment in order to clean and remove the necrotic tissue. However FDA (2008) is taking an action against such products due to severe adverse events reported in patients submitted to papain treatments. Thus, the main goal of this proposal is to develop encapsulated papain containing membranes based on hydrogels and silicone rubber in an attempt to achieve a controllable distribution of size and delivery profile, a toxicity reduction and provide stability towards radiation processing through molecular encapsulation with β-cyclodextrin, which may also provide protection to the enzyme against radiation induced radiolysis. (author)

  17. Postural stability decreases in elite young soccer players after a competitive soccer match

    DEFF Research Database (Denmark)

    Brito, João; Fontes, Ivo; Ribeiro, Fernando

    2012-01-01

    To investigate the effects of an official soccer match on postural stability in youth elite soccer players.......To investigate the effects of an official soccer match on postural stability in youth elite soccer players....

  18. Estrogen-related receptor α decreases RHOA stability to induce orientated cell migration.

    Science.gov (United States)

    Sailland, Juliette; Tribollet, Violaine; Forcet, Christelle; Billon, Cyrielle; Barenton, Bruno; Carnesecchi, Julie; Bachmann, Alice; Gauthier, Karine Cécile; Yu, Shan; Giguère, Vincent; Chan, Franky L; Vanacker, Jean-Marc

    2014-10-21

    Several physiopathological processes require orientated cellular migration. This phenomenon highly depends on members of the RHO family of GTPases. Both excessive and deficient RHO activity impair directional migration. A tight control is thus exerted on these proteins through the regulation of their activation and of their stability. Here we show that the estrogen-related receptor α (ERRα) directly activates the expression of TNFAIP1, the product of which [BTB/POZ domain-containing adapter for Cullin3-mediated RhoA degradation 2 (BACURD2)] regulates RHOA protein turnover. Inactivation of the receptor leads to enhanced RHOA stability and activation. This results in cell disorientation, increased actin network, and inability to form a lamellipodium at the migration edge. As a consequence, directional migration, but not cell motility per se, is impaired in the absence of the receptor, under pathological as well as physiological conditions. Altogether, our results show that the control exerted by ERRα on RHOA stability is required for directional migration.

  19. Postural equilibrium during pregnancy: decreased stability with an increased reliance on visual cues.

    Science.gov (United States)

    Butler, Erin E; Colón, Iris; Druzin, Maurice L; Rose, Jessica

    2006-10-01

    The purpose of this study was to determine whether there are changes in postural equilibrium during pregnancy and to examine whether the incidence of falls increases during pregnancy. Static postural balance measures were collected from 12 pregnant women at 11 to 14, 19 to 22, and 36 to 39 weeks gestation and at 6 to 8 weeks after delivery and from 12 nulligravid control subjects who were matched for age, height, weight, and body mass index. Subjects were asked to stand quietly on a stable force platform for 30 seconds with eyes open and closed. Path length and average radial displacement were computed on the basis of the average of 3 trials for each condition. The women were asked at each session if they had sustained a fall in the previous 3 months. Postural stability remained relatively stable during the first trimester; however, second and third trimester and postpartum values for path length and average radial displacement with eyes open and closed were increased significantly compared with the control subjects, which indicates diminished postural balance. The difference between the eyes open and closed values of path length increased as pregnancy progressed. Although 25% of pregnant women sustained falls, none of the control subjects had fallen in the past year. These data suggest that postural stability declines during pregnancy and remains diminished at 6 to 8 weeks after delivery. The study also indicates that there is an increased reliance on visual cues to maintain balance during pregnancy.

  20. Mechanical Stability of Stratified Sediments along the upper continental Slope off Vesterålen, northern Norway - Insights from in situ CPTU Tests

    Science.gov (United States)

    Voelker, D.; Stegmann, S.; Kreiter, S.; L'Heureux, J. S.; Vanneste, M. W. B.; Baeten, N. J.; Knudsen, S.; Rise, L.; Longva, O.; Brendryen, J.; Haflidason, H.; Chand, S.; Mörz, T.; Kopf, A.

    2015-12-01

    High-resolution single channel-seismic data (3.5 kHz) reveal small-scale submarine landslide structures and superficial deformation features (e.g. tension cracks) along the gently dipping (3°) upper continental slope west of the Vesterålen Archipelago off northern Norway. Previous laboratory-based geotechnical studies attest that the slope is per sestable and that seismic events in an order of magnitude M5.7 may have triggered the slope sediments to fail. Here we present geotechnical in situ data (sedimentary strength, pore pressure), which were obtained with RV Poseidon in summer 2014 using the static CPTU system GOST. The CPTU system provided high-resolution geotechnical profiles of the uppermost sediments to a maximum penetration depth of ~ 20 m at six sites within the landslide features and beside them in undisturbed slope sediments as reference. The CPTU data reveal the occurrence of mechanically weaker zones (MWZ) by the drop of sedimentary strength. These zones are interbedded by coarser, more competent layers. The occurrence of sensitive fine-grained material may be responsible for the loss of strength in the deeper portion (appx. 12 to 18 m below seafloor). An 1D infinite pseudo-static stability analysis attests that the mechanically weaker zones (MWZ) correlate well with portions, where the Factor of Safety (FoS) ≤ 1 (meta-stable to unstable) indicates permanent deformation or failure in case additional dynamic load is induced by an earthquake. Thus, the mechanically weak layers can be considered as one important pre-condition for landslide activity. In conclusion, the integration of in situ CPTU data with geophysical data improves soil characterization and hence foster a better understanding of the pre-conditioning factors for slope instability at the upper continental slope off Vesterålen. Risk assessment for the present-day slope off Vesterålen is particularly crucial, because the opening of the region for offshore oil and gas exploration is

  1. Free Falling in Stratified Fluids

    Science.gov (United States)

    Lam, Try; Vincent, Lionel; Kanso, Eva

    2017-11-01

    Leaves falling in air and discs falling in water are examples of unsteady descents due to complex interaction between gravitational and aerodynamic forces. Understanding these descent modes is relevant to many branches of engineering and science such as estimating the behavior of re-entry space vehicles to studying biomechanics of seed dispersion. For regularly shaped objects falling in homogenous fluids, the motion is relatively well understood. However, less is known about how density stratification of the fluid medium affects the falling behavior. Here, we experimentally investigate the descent of discs in both pure water and in stable linearly stratified fluids for Froude numbers Fr 1 and Reynolds numbers Re between 1000 -2000. We found that stable stratification (1) enhances the radial dispersion of the disc at landing, (2) increases the descent time, (3) decreases the inclination (or nutation) angle, and (4) decreases the fluttering amplitude while falling. We conclude by commenting on how the corresponding information can be used as a predictive model for objects free falling in stratified fluids.

  2. Artificial climate warming positively affects arbuscular mycorrhizae but decreases soil aggregate water stability in an annual grassland

    Energy Technology Data Exchange (ETDEWEB)

    Rillig, M.C.; Wright, S.F.; Shaw, M.R.; Field, C.B.

    2002-04-01

    Despite the importance of arbuscular mycorrhizae to the functioning of terrestrial ecosystems (e.g. nutrient uptake, soil aggregation), and the increasing evidence of global warming, responses of arbuscular mycorrhizal fungi (AMF) to climate warming are poorly understood. In a field experiment using infrared heaters, we found effects of warming on AMF after one growing season in an annual grassland, in the absence of any effects on measured root parameters (weight, length, average diameter). AMF soil hyphal length was increased by over 40% in the warmed plots, accompanied by a strong trend for AMF root colonization increase. In the following year, root weight was again not significantly changed, and AMF root colonization increased significantly in the warmed plots. Concentration of the soil protein glomalin, a glycoprotein produced by AMF hyphae with importance in soil aggregation, was decreased in the warmed plots. Soil aggregate water stability, measured for five diameter size classes, was also decreased significantly. In the following year, soil aggregate weight in two size classes was decreased significantly, but the effect size was very small. These results indicate that ecosystem warming may have stimulated carbon allocation to AMF. Other factors either influenced glomalin decomposition or production, hence influencing the role of these symbionts in soil aggregation. The observed small changes in soil aggregation, if widespread among terrestrial ecosystems, could have important consequences for soil carbon storage and erosion in a warmed climate, especially if there are cumulative effects of warming. (au)

  3. Increased Protein Stability and Decreased Protein Turnover in the Caenorhabditis elegans Ins/IGF-1 daf-2 Mutant.

    Science.gov (United States)

    Depuydt, Geert; Shanmugam, Nilesh; Rasulova, Madina; Dhondt, Ineke; Braeckman, Bart P

    2016-12-01

    In Caenorhabditis elegans, cellular proteostasis is likely essential for longevity. Autophagy has been shown to be essential for lifespan extension of daf-2 insulin/IGF mutants. Therefore, it can be hypothesized that daf-2 mutants achieve this phenotype by increasing protein turnover. However, such a mechanism would exert a substantial energy cost. By using classical 35 S pulse-chase labeling, we observed that protein synthesis and degradation rates are decreased in young adults of the daf-2 insulin/IGF mutants. Although reduction of protein turnover may be energetically favorable, it may lead to accumulation and aggregation of damaged proteins. As this has been shown not to be the case in daf-2 mutants, another mechanism must exist to maintain proteostasis in this strain. We observed that proteins isolated from daf-2 mutants are more soluble in acidic conditions due to increased levels of trehalose. This suggests that trehalose may decrease the potential for protein aggregation and increases proteostasis in the daf-2 mutants. We postulate that daf-2 mutants save energy by decreasing protein turnover rates and instead stabilize their proteome by trehalose. © The Author 2016. Published by Oxford University Press on behalf of The Gerontological Society of America.

  4. The stratified Boycott effect

    Science.gov (United States)

    Peacock, Tom; Blanchette, Francois; Bush, John W. M.

    2005-04-01

    We present the results of an experimental investigation of the flows generated by monodisperse particles settling at low Reynolds number in a stably stratified ambient with an inclined sidewall. In this configuration, upwelling beneath the inclined wall associated with the Boycott effect is opposed by the ambient density stratification. The evolution of the system is determined by the relative magnitudes of the container depth, h, and the neutral buoyancy height, hn = c0(ρp-ρf)/|dρ/dz|, where c0 is the particle concentration, ρp the particle density, ρf the mean fluid density and dρ/dz Boycott layer transports dense fluid from the bottom to the top of the system; subsequently, the upper clear layer of dense saline fluid is mixed by convection. For sufficiently strong stratification, h > hn, layering occurs. The lowermost layer is created by clear fluid transported from the base to its neutral buoyancy height, and has a vertical extent hn; subsequently, smaller overlying layers develop. Within each layer, convection erodes the initially linear density gradient, generating a step-like density profile throughout the system that persists after all the particles have settled. Particles are transported across the discrete density jumps between layers by plumes of particle-laden fluid.

  5. Technologies for Decreasing Mining Losses

    Science.gov (United States)

    Valgma, Ingo; Väizene, Vivika; Kolats, Margit; Saarnak, Martin

    2013-12-01

    In case of stratified deposits like oil shale deposit in Estonia, mining losses depend on mining technologies. Current research focuses on extraction and separation possibilities of mineral resources. Selective mining, selective crushing and separation tests have been performed, showing possibilities of decreasing mining losses. Rock crushing and screening process simulations were used for optimizing rock fractions. In addition mine backfilling, fine separation, and optimized drilling and blasting have been analyzed. All tested methods show potential and depend on mineral usage. Usage in addition depends on the utilization technology. The questions like stability of the material flow and influences of the quality fluctuations to the final yield are raised.

  6. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  7. Concurrent Increases and Decreases in Local Stability and Conformational Heterogeneity in Cu, Zn Superoxide Dismutase Variants Revealed by Temperature-Dependence of Amide Chemical Shifts.

    Science.gov (United States)

    Doyle, Colleen M; Rumfeldt, Jessica A; Broom, Helen R; Sekhar, Ashok; Kay, Lewis E; Meiering, Elizabeth M

    2016-03-08

    The chemical shifts of backbone amide protons in proteins are sensitive reporters of local structural stability and conformational heterogeneity, which can be determined from their readily measured linear and nonlinear temperature-dependences, respectively. Here we report analyses of amide proton temperature-dependences for native dimeric Cu, Zn superoxide dismutase (holo pWT SOD1) and structurally diverse mutant SOD1s associated with amyotrophic lateral sclerosis (ALS). Holo pWT SOD1 loses structure with temperature first at its periphery and, while having extremely high global stability, nevertheless exhibits extensive conformational heterogeneity, with ∼1 in 5 residues showing evidence for population of low energy alternative states. The holo G93A and E100G ALS mutants have moderately decreased global stability, whereas V148I is slightly stabilized. Comparison of the holo mutants as well as the marginally stable immature monomeric unmetalated and disulfide-reduced (apo(2SH)) pWT with holo pWT shows that changes in the local structural stability of individual amides vary greatly, with average changes corresponding to differences in global protein stability measured by differential scanning calorimetry. Mutants also exhibit altered conformational heterogeneity compared to pWT. Strikingly, substantial increases as well as decreases in local stability and conformational heterogeneity occur, in particular upon maturation and for G93A. Thus, the temperature-dependence of amide shifts for SOD1 variants is a rich source of information on the location and extent of perturbation of structure upon covalent changes and ligand binding. The implications for potential mechanisms of toxic misfolding of SOD1 in disease and for general aspects of protein energetics, including entropy-enthalpy compensation, are discussed.

  8. Electromagnetic waves in stratified media

    CERN Document Server

    Wait, James R; Fock, V A; Wait, J R

    2013-01-01

    International Series of Monographs in Electromagnetic Waves, Volume 3: Electromagnetic Waves in Stratified Media provides information pertinent to the electromagnetic waves in media whose properties differ in one particular direction. This book discusses the important feature of the waves that enables communications at global distances. Organized into 13 chapters, this volume begins with an overview of the general analysis for the electromagnetic response of a plane stratified medium comprising of any number of parallel homogeneous layers. This text then explains the reflection of electromagne

  9. Glucocorticoids selectively inhibit the transcription of the interleukin 1β gene and decrease the stability of interleukin 1β mRNA

    International Nuclear Information System (INIS)

    Lee, S.W.; Tsou, A.P.; Chan, H.; Thomas, J.; Petrie, K.; Eugui, E.M.; Allison, A.C.

    1988-01-01

    Transcription of the interleukin 1β (IL-1β) gene was studied by mRNA hybridization with a cDNA probe in the human promonocytic cell line U-937. Phorbol ester and lipopolysaccharide increased the steady-state level of Il-1β mRNA. Glucocorticoids markedly decreased IL-1β mRNA levels by two mechanisms. Transcription of the IL-1 gene was inhibited, as shown by in vitro transcription assays with nuclei isolated from glucocorticoid-treated cells. Moreover, kinetic analyses and pulse-labeling of mRNAs showed that glucocorticoids selectively decrease the stability of IL-1β mRNA, without affecting the stability of β-actin and FOS mRNAs. Inhibition of the formation and effects IL-1 is a mechanism by which glucocorticoids can exert antiinflammatory and immunosuppressive effects

  10. The effect of Pilates based exercise on mobility, postural stability, and balance in order to decrease fall risk in older adults.

    Science.gov (United States)

    Pata, Rachel W; Lord, Katrina; Lamb, Jamie

    2014-07-01

    Falls are a common problem in older adults. Impaired balance, mobility and postural stability are risk factors for falling. Limited research has been performed on Pilates exercise and the ability to decrease fall risk. In this quasi-experimental study, 35 adults (61-87 years old) participated in an 8-week Pilates based exercise program. Blind examiners conducted the Timed Up and Go (TUG), Forward Reach Test, and Turn 180 Test before and after the intervention. Number of falls, perception of Pilates, and fear of falling was also recorded. Thirty-two (91.4%) participants completed post-test measures. Significant improvements were seen in the TUG (p falling was shown. Results suggest a Pilates based exercise program may be effective in improving balance, mobility and postural stability to decrease fall risk. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Microencapsulation of butyl stearate with melamine-formaldehyde resin: Effect of decreasing the pH value on the composition and thermal stability of microcapsules

    Directory of Open Access Journals (Sweden)

    M. Krajnc

    2012-10-01

    Full Text Available The object of this study was to investigate how different decreasing of pH regimes during microencapsulation process with melamine-formaldehyde (MF resin affects the composition, morphology and thermal stability of microcapsules containing a phase-change material (PCM. Technical butyl stearate was used as PCM. Microencapsulation was carried out at 70°C. For all experiments the starting pH value was 6.0. After one hour of microencapsulation at the starting pH value, the pH value was lowered to final pH value (5.5; 5.0; 4.5 in a stepwise or linear way. The properties of microcapsules were monitored during and after the microencapsulation process. The results showed that pH value decreasing regime was critical for the morphology and stability of microcapsules. During microencapsulations with a stepwise decrease of pH value we observed faster increase of the amount of MF resin in the microencapsulation product compared to the microencapsulations with a linear pH value decrease. However, faster deposition in the case of microencapsulations with stepwise decrease of pH value did not result in thicker MF shells. The shell thickness increased much faster when the pH value was decreased in a linear way or in several smaller steps. It was shown that for the best thermal stability of microcapsules, the pH value during microencapsulation had to be lowered in a linear way or in smaller steps to 5.0 or lower.

  12. Stratified medicine and reimbursement issues

    NARCIS (Netherlands)

    Fugel, Hans-Joerg; Nuijten, Mark; Postma, Maarten

    2012-01-01

    Stratified Medicine (SM) has the potential to target patient populations who will most benefit from a therapy while reducing unnecessary health interventions associated with side effects. The link between clinical biomarkers/diagnostics and therapies provides new opportunities for value creation to

  13. The Stratified Legitimacy of Abortions.

    Science.gov (United States)

    Kimport, Katrina; Weitz, Tracy A; Freedman, Lori

    2016-12-01

    Roe v. Wade was heralded as an end to unequal access to abortion care in the United States. However, today, despite being common and safe, abortion is performed only selectively in hospitals and private practices. Drawing on 61 interviews with obstetrician-gynecologists in these settings, we examine how they determine which abortions to perform. We find that they distinguish between more and less legitimate abortions, producing a narrative of stratified legitimacy that privileges abortions for intended pregnancies, when the fetus is unhealthy, and when women perform normative gendered sexuality, including distress about the abortion, guilt about failure to contracept, and desire for motherhood. This stratified legitimacy can perpetuate socially-inflected inequality of access and normative gendered sexuality. Additionally, we argue that the practice by physicians of distinguishing among abortions can legitimate legislative practices that regulate and restrict some kinds of abortion, further constraining abortion access. © American Sociological Association 2016.

  14. Stratified Medicine and Reimbursement Issues

    Directory of Open Access Journals (Sweden)

    Hans-Joerg eFugel

    2012-10-01

    Full Text Available Stratified Medicine (SM has the potential to target patient populations who will most benefit from a therapy while reducing unnecessary health interventions associated with side effects. The link between clinical biomarkers/diagnostics and therapies provides new opportunities for value creation to strengthen the value proposition to pricing and reimbursement (P&R authorities. However, the introduction of SM challenges current reimbursement schemes in many EU countries and the US as different P&R policies have been adopted for drugs and diagnostics. Also, there is a lack of a consistent process for value assessment of more complex diagnostics in these markets. New, innovative approaches and more flexible P&R systems are needed to reflect the added value of diagnostic tests and to stimulate investments in new technologies. Yet, the framework for access of diagnostic–based therapies still requires further development while setting the right incentives and appropriate align stakeholders interests when realizing long- term patient benefits. This article addresses the reimbursement challenges of SM approaches in several EU countries and the US outlining some options to overcome existing reimbursement barriers for stratified medicine.

  15. Design of dry sand soil stratified sampler

    Science.gov (United States)

    Li, Erkang; Chen, Wei; Feng, Xiao; Liao, Hongbo; Liang, Xiaodong

    2018-04-01

    This paper presents a design of a stratified sampler for dry sand soil, which can be used for stratified sampling of loose sand under certain conditions. Our group designed the mechanical structure of a portable, single - person, dry sandy soil stratified sampler. We have set up a mathematical model for the sampler. It lays the foundation for further development of design research.

  16. Stratified patterns of divorce: Earnings, education, and gender

    Directory of Open Access Journals (Sweden)

    Amit Kaplan

    2015-05-01

    Full Text Available Background: Despite evidence that divorce has become more prevalent among weaker socioeconomic groups, knowledge about the stratification aspects of divorce in Israel is lacking. Moreover, although scholarly debate recognizes the importance of stratificational positions with respect to divorce, less attention has been given to the interactions between them. Objective: Our aim is to examine the relationship between social inequality and divorce, focusing on how household income, education, employment stability, relative earnings, and the intersection between them affect the risk of divorce in Israel. Methods: The data is derived from combined census files for 1995-2008, annual administrative employment records from the National Insurance Institute and the Tax Authority, and data from the Civil Registry of Divorce. We used a series of discrete-time event-history analysis models for marital dissolution. Results: Couples in lower socioeconomic positions had a higher risk of divorce in Israel. Higher education in general, and homogamy in terms of higher education (both spouses have degrees in particular, decreased the risk of divorce. The wife's relative earnings had a differential effect on the likelihood of divorce, depending on household income: a wife who outearned her husband increased the log odds of divorce more in the upper tertiles than in the lower tertile. Conclusions: Our study shows that divorce indeed has a stratified pattern and that weaker socioeconomic groups experience the highest levels of divorce. Gender inequality within couples intersects with the household's economic and educational resources.

  17. Suppression of stratified explosive interactions

    Energy Technology Data Exchange (ETDEWEB)

    Meeks, M.K.; Shamoun, B.I.; Bonazza, R.; Corradini, M.L. [Wisconsin Univ., Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics

    1998-01-01

    Stratified Fuel-Coolant Interaction (FCI) experiments with Refrigerant-134a and water were performed in a large-scale system. Air was uniformly injected into the coolant pool to establish a pre-existing void which could suppress the explosion. Two competing effects due to the variation of the air flow rate seem to influence the intensity of the explosion in this geometrical configuration. At low flow rates, although the injected air increases the void fraction, the concurrent agitation and mixing increases the intensity of the interaction. At higher flow rates, the increase in void fraction tends to attenuate the propagated pressure wave generated by the explosion. Experimental results show a complete suppression of the vapor explosion at high rates of air injection, corresponding to an average void fraction of larger than 30%. (author)

  18. Humid Heat Autoclaving of Hybrid Nanoparticles Achieved by Decreased Nanoparticle Concentration and Improved Nanoparticle Stability Using Medium Chain Triglycerides as a Modifier.

    Science.gov (United States)

    Gou, Jingxin; Chao, Yanhui; Liang, Yuheng; Zhang, Ning; He, Haibing; Yin, Tian; Zhang, Yu; Xu, Hui; Tang, Xing

    2016-09-01

    Humid heat autoclaving is a facile technique widely used in the sterilization of injections, but the high temperature employed would destroy nanoparticles composed of biodegradable polymers. The aim of this study was to investigate whether incorporation of medium chain triglycerides (MCT) could stabilize nanoparticles composed of poly (ethylene glycol)-b-polycaprolactone (PEG-b-PCL) during autoclaving (121°C, 10 min). Polymeric nanoparticles with different MCT contents were prepared by dialysis. Block copolymer degradation was studied by GPC. The critical aggregation concentrations of nanoparticles at different temperatures were determined using pyrene fluorescence. The size, morphology and weight averaged molecular weight of pristine/autoclaved nanoparticles were studied using DLS, TEM and SLS, respectively. Drug loading content and release profile were determined using RP-HPLC. The protecting effect of MCT on nanoparticles was dependent on the amount of MCT incorporated. Nanoparticles with high MCT contents, which assumed an emulsion-like morphology, showed reduced block copolymer degradation and particle disassociation after incubation at 100°C for 24 h. Nanoparticles with high MCT content showed the lowest critical aggregation concentration (CAC) under either room temperature or 60°C and the lowest particle concentration among all samples. And the particle size, drug loading content, physical stability and release profile of nanoparticles with high MCT contents remained nearly unchanged after autoclaving. Incorporation of high amount of MCT changed the morphology of PEG-b-PCL based nanoparticles to an emulsion-like structure and the nanoparticles prepared could withstand autoclaving due to improved particle stability and decreased particle concentration caused by MCT incorporation.

  19. PHOTOSPHERIC EMISSION FROM STRATIFIED JETS

    International Nuclear Information System (INIS)

    Ito, Hirotaka; Nagataki, Shigehiro; Ono, Masaomi; Lee, Shiu-Hang; Mao, Jirong; Yamada, Shoichi; Pe'er, Asaf; Mizuta, Akira; Harikae, Seiji

    2013-01-01

    We explore photospheric emissions from stratified two-component jets, wherein a highly relativistic spine outflow is surrounded by a wider and less relativistic sheath outflow. Thermal photons are injected in regions of high optical depth and propagated until the photons escape at the photosphere. Because of the presence of shear in velocity (Lorentz factor) at the boundary of the spine and sheath region, a fraction of the injected photons are accelerated using a Fermi-like acceleration mechanism such that a high-energy power-law tail is formed in the resultant spectrum. We show, in particular, that if a velocity shear with a considerable variance in the bulk Lorentz factor is present, the high-energy part of observed gamma-ray bursts (GRBs) photon spectrum can be explained by this photon acceleration mechanism. We also show that the accelerated photons might also account for the origin of the extra-hard power-law component above the bump of the thermal-like peak seen in some peculiar bursts (e.g., GRB 090510, 090902B, 090926A). We demonstrate that time-integrated spectra can also reproduce the low-energy spectrum of GRBs consistently using a multi-temperature effect when time evolution of the outflow is considered. Last, we show that the empirical E p -L p relation can be explained by differences in the outflow properties of individual sources

  20. Grain distinct stratified nanolayers in aluminium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Donatus, U., E-mail: uyimedonatus@yahoo.com [School of Materials, The University of Manchester, Manchester, M13 9PL, England (United Kingdom); Thompson, G.E.; Zhou, X.; Alias, J. [School of Materials, The University of Manchester, Manchester, M13 9PL, England (United Kingdom); Tsai, I.-L. [Oxford Instruments NanoAnalysis, HP12 2SE, High Wycombe (United Kingdom)

    2017-02-15

    The grains of aluminium alloys have stratified nanolayers which determine their mechanical and chemical responses. In this study, the nanolayers were revealed in the grains of AA6082 (T6 and T7 conditions), AA5083-O and AA2024-T3 alloys by etching the alloys in a solution comprising 20 g Cr{sub 2}O{sub 3} + 30 ml HPO{sub 3} in 1 L H{sub 2}O. Microstructural examination was conducted on selected grains of interest using scanning electron microscopy and electron backscatter diffraction technique. It was observed that the nanolayers are orientation dependent and are parallel to the {100} planes. They have ordered and repeated tunnel squares that are flawed at the sides which are aligned in the <100> directions. These flawed tunnel squares dictate the tunnelling corrosion morphology as well as appearing to have an affect on the arrangement and sizes of the precipitation hardening particles. The inclination of the stratified nanolayers, their interpacing, and the groove sizes have significant influence on the corrosion behaviour and seeming influence on the strengthening mechanism of the investigated aluminium alloys. - Highlights: • Stratified nanolayers in aluminium alloy grains. • Relationship of the stratified nanolayers with grain orientation. • Influence of the inclinations of the stratified nanolayers on corrosion. • Influence of the nanolayers interspacing and groove sizes on hardness and corrosion.

  1. Optimal energy growth in a stably stratified shear flow

    Science.gov (United States)

    Jose, Sharath; Roy, Anubhab; Bale, Rahul; Iyer, Krithika; Govindarajan, Rama

    2018-02-01

    Transient growth of perturbations by a linear non-modal evolution is studied here in a stably stratified bounded Couette flow. The density stratification is linear. Classical inviscid stability theory states that a parallel shear flow is stable to exponentially growing disturbances if the Richardson number (Ri) is greater than 1/4 everywhere in the flow. Experiments and numerical simulations at higher Ri show however that algebraically growing disturbances can lead to transient amplification. The complexity of a stably stratified shear flow stems from its ability to combine this transient amplification with propagating internal gravity waves (IGWs). The optimal perturbations associated with maximum energy amplification are numerically obtained at intermediate Reynolds numbers. It is shown that in this wall-bounded flow, the three-dimensional optimal perturbations are oblique, unlike in unstratified flow. A partitioning of energy into kinetic and potential helps in understanding the exchange of energies and how it modifies the transient growth. We show that the apportionment between potential and kinetic energy depends, in an interesting manner, on the Richardson number, and on time, as the transient growth proceeds from an optimal perturbation. The oft-quoted stabilizing role of stratification is also probed in the non-diffusive limit in the context of disturbance energy amplification.

  2. Stratified charge rotary engine for general aviation

    Science.gov (United States)

    Mount, R. E.; Parente, A. M.; Hady, W. F.

    1986-01-01

    A development history, a current development status assessment, and a design feature and performance capabilities account are given for stratified-charge rotary engines applicable to aircraft propulsion. Such engines are capable of operating on Jet-A fuel with substantial cost savings, improved altitude capability, and lower fuel consumption by comparison with gas turbine powerplants. Attention is given to the current development program of a 400-hp engine scheduled for initial operations in early 1990. Stratified charge rotary engines are also applicable to ground power units, airborne APUs, shipboard generators, and vehicular engines.

  3. A polymorphic variant in the human electron transfer flavoprotein alpha-chain (alpha-T171) displays decreased thermal stability and is overrepresented in very-long-chain acyl-CoA dehydrogenase-deficient patients with mild childhood presentation

    DEFF Research Database (Denmark)

    Bross, P; Pedersen, P; Nyholm, M

    1999-01-01

    The consequences of two amino acid polymorphisms of human electron transfer flavoprotein (alpha-T/I171 in the alpha-subunit and beta-M/T154 in the beta-subunit) on the thermal stability of the enzyme are described. The alpha-T171 variant displayed a significantly decreased thermal stability, wher....... This is compatible with a negative modulating effect of the less-stable alpha-T171 ETF variant in this group of VLCAD patients that harbor missense mutations in at least one allele and therefore potentially display residual levels of VLCAD enzyme activity. Udgivelsesdato: 1999-Jun...

  4. Nitrogen transformations in stratified aquatic microbial ecosystems

    DEFF Research Database (Denmark)

    Revsbech, N. P.; Risgaard-Petersen, N.; Schramm, A.

    2006-01-01

    Abstract  New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about n...

  5. Dietary fish oil replacement with palm or poultry oil increases fillet oxidative stability and decreases liver glutathione peroxidase activity in barramundi (Lates calcarifer).

    Science.gov (United States)

    Wan Ahmad, Wan A R; Stone, David A J; Schuller, Kathryn A

    2013-12-01

    Complete dietary fish oil replacement with palm or poultry oil in barramundi (Lates calcarifer) had no detrimental effects on growth or hepatosomatic index of juvenile fish up to an average size of ~50 g. However, it significantly decreased the omega-3 (n-3) long-chain polyunsaturated fatty acid content of the fish muscle (fillet) lipids. This was particularly true for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) which are recognised for their health beneficial effects in the human diet. As a result of their decreased EPA and DHA content, the peroxidation index of the muscle lipids was also decreased. This was associated with increased simulated retail storage shelf life as indicated by decreased thiobarbituric acid reactive substances in muscle samples from fish fed the palm or poultry oil-based diets. Concomitantly, glutathione peroxidase (GPx) activity, but not glutathione S-transferase (GST) activity or reduced glutathione concentration, was significantly reduced in the liver of barramundi fed the palm or poultry oil-based diets as compared with the fish fed the fish oil-based diet. Furthermore, GPx and GST activity were very low in muscle, much lower than in gastrointestinal tract, liver or swim bladder. Therefore, we propose that liver GPx activity may be a good predictor of fillet shelf life in barramundi and other fish species.

  6. Missense mutation Lys18Asn in dystrophin that triggers X-linked dilated cardiomyopathy decreases protein stability, increases protein unfolding, and perturbs protein structure, but does not affect protein function.

    Directory of Open Access Journals (Sweden)

    Surinder M Singh

    Full Text Available Genetic mutations in a vital muscle protein dystrophin trigger X-linked dilated cardiomyopathy (XLDCM. However, disease mechanisms at the fundamental protein level are not understood. Such molecular knowledge is essential for developing therapies for XLDCM. Our main objective is to understand the effect of disease-causing mutations on the structure and function of dystrophin. This study is on a missense mutation K18N. The K18N mutation occurs in the N-terminal actin binding domain (N-ABD. We created and expressed the wild-type (WT N-ABD and its K18N mutant, and purified to homogeneity. Reversible folding experiments demonstrated that both mutant and WT did not aggregate upon refolding. Mutation did not affect the protein's overall secondary structure, as indicated by no changes in circular dichroism of the protein. However, the mutant is thermodynamically less stable than the WT (denaturant melts, and unfolds faster than the WT (stopped-flow kinetics. Despite having global secondary structure similar to that of the WT, mutant showed significant local structural changes at many amino acids when compared with the WT (heteronuclear NMR experiments. These structural changes indicate that the effect of mutation is propagated over long distances in the protein structure. Contrary to these structural and stability changes, the mutant had no significant effect on the actin-binding function as evident from co-sedimentation and depolymerization assays. These results summarize that the K18N mutation decreases thermodynamic stability, accelerates unfolding, perturbs protein structure, but does not affect the function. Therefore, K18N is a stability defect rather than a functional defect. Decrease in stability and increase in unfolding decrease the net population of dystrophin molecules available for function, which might trigger XLDCM. Consistently, XLDCM patients have decreased levels of dystrophin in cardiac muscle.

  7. MC3D modelling of stratified explosion

    International Nuclear Information System (INIS)

    Picchi, S.; Berthoud, G.

    1999-01-01

    It is known that a steam explosion can occur in a stratified geometry and that the observed yields are lower than in the case of explosion in a premixture configuration. However, very few models are available to quantify the amount of melt which can be involved and the pressure peak that can be developed. In the stratified application of the MC3D code, mixing and fragmentation of the melt are explained by the growth of Kelvin Helmholtz instabilities due to the shear flow of the two phase coolant above the melt. Such a model is then used to recalculate the Frost-Ciccarelli tin-water experiment. Pressure peak, speed of propagation, bubble shape and erosion height are well reproduced as well as the influence of the inertial constraint (height of the water pool). (author)

  8. MC3D modelling of stratified explosion

    Energy Technology Data Exchange (ETDEWEB)

    Picchi, S.; Berthoud, G. [DTP/SMTH/LM2, CEA, 38 - Grenoble (France)

    1999-07-01

    It is known that a steam explosion can occur in a stratified geometry and that the observed yields are lower than in the case of explosion in a premixture configuration. However, very few models are available to quantify the amount of melt which can be involved and the pressure peak that can be developed. In the stratified application of the MC3D code, mixing and fragmentation of the melt are explained by the growth of Kelvin Helmholtz instabilities due to the shear flow of the two phase coolant above the melt. Such a model is then used to recalculate the Frost-Ciccarelli tin-water experiment. Pressure peak, speed of propagation, bubble shape and erosion height are well reproduced as well as the influence of the inertial constraint (height of the water pool). (author)

  9. Equipment for extracting and conveying stratified minerals

    Energy Technology Data Exchange (ETDEWEB)

    Blumenthal, G.; Kunzer, H.; Plaga, K.

    1991-08-14

    This invention relates to equipment for extracting stratified minerals and conveying the said minerals along the working face, comprising a trough shaped conveyor run assembled from lengths, a troughed extraction run in lengths matching the lengths of conveyor troughing, which is linked to the top edge of the working face side of the conveyor troughing with freedom to swivel vertically, and a positively guided chain carrying extraction tools and scrapers along the conveyor and extraction runs.

  10. Inviscid incompressible limits of strongly stratified fluids

    Czech Academy of Sciences Publication Activity Database

    Feireisl, Eduard; Jin, B.J.; Novotný, A.

    2014-01-01

    Roč. 89, 3-4 (2014), s. 307-329 ISSN 0921-7134 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes system * anelastic approximation * stratified fluid Subject RIV: BA - General Mathematics Impact factor: 0.528, year: 2014 http://iospress.metapress.com/content/d71255745tl50125/?p=969b60ae82634854ab8bd25505ce1f71&pi=3

  11. Internal circle uplifts, transversality and stratified G-structures

    Energy Technology Data Exchange (ETDEWEB)

    Babalic, Elena Mirela [Department of Theoretical Physics, National Institute of Physics and Nuclear Engineering,Str. Reactorului no.30, P.O.BOX MG-6, Postcode 077125, Bucharest-Magurele (Romania); Department of Physics, University of Craiova,13 Al. I. Cuza Str., Craiova 200585 (Romania); Lazaroiu, Calin Iuliu [Center for Geometry and Physics, Institute for Basic Science,Pohang 790-784 (Korea, Republic of)

    2015-11-24

    We study stratified G-structures in N=2 compactifications of M-theory on eight-manifolds M using the uplift to the auxiliary nine-manifold M̂=M×S{sup 1}. We show that the cosmooth generalized distribution D̂ on M̂ which arises in this formalism may have pointwise transverse or non-transverse intersection with the pull-back of the tangent bundle of M, a fact which is responsible for the subtle relation between the spinor stabilizers arising on M and M̂ and for the complicated stratified G-structure on M which we uncovered in previous work. We give a direct explanation of the latter in terms of the former and relate explicitly the defining forms of the SU(2) structure which exists on the generic locus U of M to the defining forms of the SU(3) structure which exists on an open subset Û of M̂, thus providing a dictionary between the eight- and nine-dimensional formalisms.

  12. Nitrogen transformations in stratified aquatic microbial ecosystems

    DEFF Research Database (Denmark)

    Revsbech, Niels Peter; Risgaard-Petersen, N.; Schramm, Andreas

    2006-01-01

    Abstract  New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about n...... performing dissimilatory reduction of nitrate to ammonium have given new dimensions to the understanding of nitrogen cycling in nature, and the occurrence of these organisms and processes in stratified microbial communities will be described in detail.......Abstract  New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about...... nitrogen fixation, nitrification, denitrification, and dissimilatory reduction of nitrate to ammonium, and about the microorganisms performing the processes, has been produced by use of these techniques. During the last decade the discovery of anammmox bacteria and migrating, nitrate accumulating bacteria...

  13. Large eddy simulation of stably stratified turbulence

    International Nuclear Information System (INIS)

    Shen Zhi; Zhang Zhaoshun; Cui Guixiang; Xu Chunxiao

    2011-01-01

    Stably stratified turbulence is a common phenomenon in atmosphere and ocean. In this paper the large eddy simulation is utilized for investigating homogeneous stably stratified turbulence numerically at Reynolds number Re = uL/v = 10 2 ∼10 3 and Froude number Fr = u/NL = 10 −2 ∼10 0 in which u is root mean square of velocity fluctuations, L is integral scale and N is Brunt-Vaïsälä frequency. Three sets of computation cases are designed with different initial conditions, namely isotropic turbulence, Taylor Green vortex and internal waves, to investigate the statistical properties from different origins. The computed horizontal and vertical energy spectra are consistent with observation in atmosphere and ocean when the composite parameter ReFr 2 is greater than O(1). It has also been found in this paper that the stratification turbulence can be developed under different initial velocity conditions and the internal wave energy is dominated in the developed stably stratified turbulence.

  14. Appetite - decreased

    Science.gov (United States)

    Loss of appetite; Decreased appetite; Anorexia ... Any illness can reduce appetite. If the illness is treatable, the appetite should return when the condition is cured. Loss of appetite can cause weight ...

  15. E25 stratified torch ignition engine emissions and combustion analysis

    International Nuclear Information System (INIS)

    Rodrigues Filho, Fernando Antonio; Baêta, José Guilherme Coelho; Teixeira, Alysson Fernandes; Valle, Ramón Molina; Fonseca de Souza, José Leôncio

    2016-01-01

    Highlights: • A stratified torch ignition (STI) engine was built and tested. • The STI engines was tested in a wide range of load and speed. • Significant reduction on emissions was achieved by means of the STI system. • Low cyclic variability characterized the lean combustion process of the torch ignition engine. • HC emission is the main drawback of the stratified torch ignition engine. - Abstract: Vehicular emissions significantly increase atmospheric air pollution and greenhouse gases (GHG). This fact associated with fast global vehicle fleet growth calls for prompt scientific community technological solutions in order to promote a significant reduction in vehicle fuel consumption and emissions, especially of fossil fuels to comply with future legislation. To meet this goal, a prototype stratified torch ignition (STI) engine was built from a commercial existing baseline engine. In this system, combustion starts in a pre-combustion chamber, where the pressure increase pushes the combustion jet flames through calibrated nozzles to be precisely targeted into the main chamber. These combustion jet flames are endowed with high thermal and kinetic energy, being able to generate a stable lean combustion process. The high kinetic and thermal energy of the combustion jet flame results from the load stratification. This is carried out through direct fuel injection in the pre-combustion chamber by means of a prototype gasoline direct injector (GDI) developed for a very low fuel flow rate. In this work the engine out-emissions of CO, NOx, HC and CO_2 of the STI engine are presented and a detailed analysis supported by the combustion parameters is conducted. The results obtained in this work show a significant decrease in the specific emissions of CO, NOx and CO_2 of the STI engine in comparison with the baseline engine. On the other hand, HC specific emission increased due to wall wetting from the fuel hitting in the pre-combustion chamber wall.

  16. [Causes of emergency dizziness stratified by etiology].

    Science.gov (United States)

    Qiao, Wenying; Liu, Jianguo; Zeng, Hong; Liu, Yugeng; Jia, Weihua; Wang, Honghong; Liu, Bo; Tan, Jing; Li, Changqing

    2014-06-03

    To explore the causes of emergency dizziness stratified to improve the diagnostic efficiency. A total of 1 857 cases of dizziness at our emergency department were collected and their etiologies stratified by age and gender. The top three diagnoses were benign paroxysmal positional vertigo (BPPV, 31.7%), hypertension (24.0%) and posterior circulation ischemia (PCI, 20.5%). Stratified by age, the main causes of dizziness included BPPV (n = 6), migraine-associated vertigo (n = 2), unknown cause (n = 1) for the group of vertigo (14.5%) and neurosis (7.3%) for 18-44 years; BPPV (36.8%), hypertension (22.4%) and migraine-associated vertigo (11.2%) for 45-59 years; hypertension (30.8%), PCI (29.8%) and BPPV (22.9%) for 60-74 years; PCI (30.7%), hypertension (28.6%) and BPPV (25.5%) for 75-92 years. BPPV, migraine and neurosis were more common in females while hypertension and PCI predominated in males (all P hypertension, neurosis and migraine showed the following significant demographic features: BPPV, PCI, hypertension, neurosis and migraine may be the main causes of dizziness. BPPV should be considered initially when vertigo was triggered repeatedly by positional change, especially for young and middle-aged women. And the other common causes of dizziness were migraine-associated vertigo, neurosis and Meniere's disease.Hypertension should be screened firstly in middle-aged and elderly patients presenting mainly with head heaviness and stretching. In elders with dizziness, BPPV is second in constituent ratio to PCI and hypertension.In middle-aged and elderly patients with dizziness, psychological factors should be considered and diagnosis and treatment should be offered timely.

  17. White dwarf stars with chemically stratified atmospheres

    Science.gov (United States)

    Muchmore, D.

    1982-01-01

    Recent observations and theory suggest that some white dwarfs may have chemically stratified atmospheres - thin layers of hydrogen lying above helium-rich envelopes. Models of such atmospheres show that a discontinuous temperature inversion can occur at the boundary between the layers. Model spectra for layered atmospheres at 30,000 K and 50,000 K tend to have smaller decrements at 912 A, 504 A, and 228 A than uniform atmospheres would have. On the basis of their continuous extreme ultraviolet spectra, it is possible to distinguish observationally between uniform and layered atmospheres for hot white dwarfs.

  18. Bayesian stratified sampling to assess corpus utility

    Energy Technology Data Exchange (ETDEWEB)

    Hochberg, J.; Scovel, C.; Thomas, T.; Hall, S.

    1998-12-01

    This paper describes a method for asking statistical questions about a large text corpus. The authors exemplify the method by addressing the question, ``What percentage of Federal Register documents are real documents, of possible interest to a text researcher or analyst?`` They estimate an answer to this question by evaluating 200 documents selected from a corpus of 45,820 Federal Register documents. Bayesian analysis and stratified sampling are used to reduce the sampling uncertainty of the estimate from over 3,100 documents to fewer than 1,000. A possible application of the method is to establish baseline statistics used to estimate recall rates for information retrieval systems.

  19. Stratified B-trees and versioning dictionaries

    OpenAIRE

    Twigg, Andy; Byde, Andrew; Milos, Grzegorz; Moreton, Tim; Wilkes, John; Wilkie, Tom

    2011-01-01

    A classic versioned data structure in storage and computer science is the copy-on-write (CoW) B-tree -- it underlies many of today's file systems and databases, including WAFL, ZFS, Btrfs and more. Unfortunately, it doesn't inherit the B-tree's optimality properties; it has poor space utilization, cannot offer fast updates, and relies on random IO to scale. Yet, nothing better has been developed since. We describe the `stratified B-tree', which beats all known semi-external memory versioned B...

  20. Soil mixing of stratified contaminated sands.

    Science.gov (United States)

    Al-Tabba, A; Ayotamuno, M J; Martin, R J

    2000-02-01

    Validation of soil mixing for the treatment of contaminated ground is needed in a wide range of site conditions to widen the application of the technology and to understand the mechanisms involved. Since very limited work has been carried out in heterogeneous ground conditions, this paper investigates the effectiveness of soil mixing in stratified sands using laboratory-scale augers. This enabled a low cost investigation of factors such as grout type and form, auger design, installation procedure, mixing mode, curing period, thickness of soil layers and natural moisture content on the unconfined compressive strength, leachability and leachate pH of the soil-grout mixes. The results showed that the auger design plays a very important part in the mixing process in heterogeneous sands. The variability of the properties measured in the stratified soils and the measurable variations caused by the various factors considered, highlighted the importance of duplicating appropriate in situ conditions, the usefulness of laboratory-scale modelling of in situ conditions and the importance of modelling soil and contaminant heterogeneities at the treatability study stage.

  1. Stratified coastal ocean interactions with tropical cyclones

    Science.gov (United States)

    Glenn, S. M.; Miles, T. N.; Seroka, G. N.; Xu, Y.; Forney, R. K.; Yu, F.; Roarty, H.; Schofield, O.; Kohut, J.

    2016-01-01

    Hurricane-intensity forecast improvements currently lag the progress achieved for hurricane tracks. Integrated ocean observations and simulations during hurricane Irene (2011) reveal that the wind-forced two-layer circulation of the stratified coastal ocean, and resultant shear-induced mixing, led to significant and rapid ahead-of-eye-centre cooling (at least 6 °C and up to 11 °C) over a wide swath of the continental shelf. Atmospheric simulations establish this cooling as the missing contribution required to reproduce Irene's accelerated intensity reduction. Historical buoys from 1985 to 2015 show that ahead-of-eye-centre cooling occurred beneath all 11 tropical cyclones that traversed the Mid-Atlantic Bight continental shelf during stratified summer conditions. A Yellow Sea buoy similarly revealed significant and rapid ahead-of-eye-centre cooling during Typhoon Muifa (2011). These findings establish that including realistic coastal baroclinic processes in forecasts of storm intensity and impacts will be increasingly critical to mid-latitude population centres as sea levels rise and tropical cyclone maximum intensities migrate poleward. PMID:26953963

  2. Stratified Simulations of Collisionless Accretion Disks

    Energy Technology Data Exchange (ETDEWEB)

    Hirabayashi, Kota; Hoshino, Masahiro, E-mail: hirabayashi-k@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, Tokyo, 113-0033 (Japan)

    2017-06-10

    This paper presents a series of stratified-shearing-box simulations of collisionless accretion disks in the recently developed framework of kinetic magnetohydrodynamics (MHD), which can handle finite non-gyrotropy of a pressure tensor. Although a fully kinetic simulation predicted a more efficient angular-momentum transport in collisionless disks than in the standard MHD regime, the enhanced transport has not been observed in past kinetic-MHD approaches to gyrotropic pressure anisotropy. For the purpose of investigating this missing link between the fully kinetic and MHD treatments, this paper explores the role of non-gyrotropic pressure and makes the first attempt to incorporate certain collisionless effects into disk-scale, stratified disk simulations. When the timescale of gyrotropization was longer than, or comparable to, the disk-rotation frequency of the orbit, we found that the finite non-gyrotropy selectively remaining in the vicinity of current sheets contributes to suppressing magnetic reconnection in the shearing-box system. This leads to increases both in the saturated amplitude of the MHD turbulence driven by magnetorotational instabilities and in the resultant efficiency of angular-momentum transport. Our results seem to favor the fast advection of magnetic fields toward the rotation axis of a central object, which is required to launch an ultra-relativistic jet from a black hole accretion system in, for example, a magnetically arrested disk state.

  3. Monte Carlo stratified source-sampling

    International Nuclear Information System (INIS)

    Blomquist, R.N.; Gelbard, E.M.

    1997-01-01

    In 1995, at a conference on criticality safety, a special session was devoted to the Monte Carlo open-quotes eigenvalue of the worldclose quotes problem. Argonne presented a paper, at that session, in which the anomalies originally observed in that problem were reproduced in a much simplified model-problem configuration, and removed by a version of stratified source-sampling. The original test-problem was treated by a special code designed specifically for that purpose. Recently ANL started work on a method for dealing with more realistic eigenvalue of the world configurations, and has been incorporating this method into VIM. The original method has been modified to take into account real-world statistical noise sources not included in the model problem. This paper constitutes a status report on work still in progress

  4. Ecosystem metabolism in a stratified lake

    DEFF Research Database (Denmark)

    Stæhr, Peter Anton; Christensen, Jesper Philip Aagaard; Batt, Ryan D.

    2012-01-01

    , differences were not significant. During stratification, daily variability in epilimnetic DO was dominated by metabolism (46%) and air-water gas exchange (44%). Fluxes related to mixed-layer deepening dominated in meta- and hypolimnic waters (49% and 64%), while eddy diffusion (1% and 14%) was less important....... Although air-water gas exchange rates differed among the three formulations of gas-transfer velocity, this had no significant effect on metabolic rates....... that integrates rates across the entire depth profile and includes DO exchange between depth layers driven by mixed-layer deepening and eddy diffusivity. During full mixing, NEP was close to zero throughout the water column, and GPP and R were reduced 2-10 times compared to stratified periods. When present...

  5. Stratified growth in Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Werner, E.; Roe, F.; Bugnicourt, A.

    2004-01-01

    In this study, stratified patterns of protein synthesis and growth were demonstrated in Pseudomonas aeruginosa biofilms. Spatial patterns of protein synthetic activity inside biofilms were characterized by the use of two green fluorescent protein (GFP) reporter gene constructs. One construct...... synthesis was restricted to a narrow band in the part of the biofilm adjacent to the source of oxygen. The zone of active GFP expression was approximately 60 Am wide in colony biofilms and 30 Am wide in flow cell biofilms. The region of the biofilm in which cells were capable of elongation was mapped...... by treating colony biofilms with carbenicillin, which blocks cell division, and then measuring individual cell lengths by transmission electron microscopy. Cell elongation was localized at the air interface of the biofilm. The heterogeneous anabolic patterns measured inside these biofilms were likely a result...

  6. Thermal instability in a stratified plasma

    International Nuclear Information System (INIS)

    Hermanns, D.F.M.; Priest, E.R.

    1989-01-01

    The thermal instability mechansism has been studied in connection to observed coronal features, like, e.g. prominences or cool cores in loops. Although these features show a lot of structure, most studies concern the thermal instability in an uniform medium. In this paper, we investigate the thermal instability and the interaction between thermal modes and the slow magneto-acoustic subspectrum for a stratified plasma slab. We fomulate the relevant system of equations and give some straightforward properties of the linear spectrum of a non-uniform plasma slab, i.e. the existence of continuous parts in the spectrum. We present a numerical scheme with which we can investigate the linear spectrum for equilibrium states with stratification. The slow and thermal subspectra of a crude coronal model are given as a preliminary result. (author). 6 refs.; 1 fig

  7. Information content of household-stratified epidemics

    Directory of Open Access Journals (Sweden)

    T.M. Kinyanjui

    2016-09-01

    Full Text Available Household structure is a key driver of many infectious diseases, as well as a natural target for interventions such as vaccination programs. Many theoretical and conceptual advances on household-stratified epidemic models are relatively recent, but have successfully managed to increase the applicability of such models to practical problems. To be of maximum realism and hence benefit, they require parameterisation from epidemiological data, and while household-stratified final size data has been the traditional source, increasingly time-series infection data from households are becoming available. This paper is concerned with the design of studies aimed at collecting time-series epidemic data in order to maximize the amount of information available to calibrate household models. A design decision involves a trade-off between the number of households to enrol and the sampling frequency. Two commonly used epidemiological study designs are considered: cross-sectional, where different households are sampled at every time point, and cohort, where the same households are followed over the course of the study period. The search for an optimal design uses Bayesian computationally intensive methods to explore the joint parameter-design space combined with the Shannon entropy of the posteriors to estimate the amount of information in each design. For the cross-sectional design, the amount of information increases with the sampling intensity, i.e., the designs with the highest number of time points have the most information. On the other hand, the cohort design often exhibits a trade-off between the number of households sampled and the intensity of follow-up. Our results broadly support the choices made in existing epidemiological data collection studies. Prospective problem-specific use of our computational methods can bring significant benefits in guiding future study designs.

  8. Information content of household-stratified epidemics.

    Science.gov (United States)

    Kinyanjui, T M; Pellis, L; House, T

    2016-09-01

    Household structure is a key driver of many infectious diseases, as well as a natural target for interventions such as vaccination programs. Many theoretical and conceptual advances on household-stratified epidemic models are relatively recent, but have successfully managed to increase the applicability of such models to practical problems. To be of maximum realism and hence benefit, they require parameterisation from epidemiological data, and while household-stratified final size data has been the traditional source, increasingly time-series infection data from households are becoming available. This paper is concerned with the design of studies aimed at collecting time-series epidemic data in order to maximize the amount of information available to calibrate household models. A design decision involves a trade-off between the number of households to enrol and the sampling frequency. Two commonly used epidemiological study designs are considered: cross-sectional, where different households are sampled at every time point, and cohort, where the same households are followed over the course of the study period. The search for an optimal design uses Bayesian computationally intensive methods to explore the joint parameter-design space combined with the Shannon entropy of the posteriors to estimate the amount of information in each design. For the cross-sectional design, the amount of information increases with the sampling intensity, i.e., the designs with the highest number of time points have the most information. On the other hand, the cohort design often exhibits a trade-off between the number of households sampled and the intensity of follow-up. Our results broadly support the choices made in existing epidemiological data collection studies. Prospective problem-specific use of our computational methods can bring significant benefits in guiding future study designs. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  9. Stratified sampling design based on data mining.

    Science.gov (United States)

    Kim, Yeonkook J; Oh, Yoonhwan; Park, Sunghoon; Cho, Sungzoon; Park, Hayoung

    2013-09-01

    To explore classification rules based on data mining methodologies which are to be used in defining strata in stratified sampling of healthcare providers with improved sampling efficiency. We performed k-means clustering to group providers with similar characteristics, then, constructed decision trees on cluster labels to generate stratification rules. We assessed the variance explained by the stratification proposed in this study and by conventional stratification to evaluate the performance of the sampling design. We constructed a study database from health insurance claims data and providers' profile data made available to this study by the Health Insurance Review and Assessment Service of South Korea, and population data from Statistics Korea. From our database, we used the data for single specialty clinics or hospitals in two specialties, general surgery and ophthalmology, for the year 2011 in this study. Data mining resulted in five strata in general surgery with two stratification variables, the number of inpatients per specialist and population density of provider location, and five strata in ophthalmology with two stratification variables, the number of inpatients per specialist and number of beds. The percentages of variance in annual changes in the productivity of specialists explained by the stratification in general surgery and ophthalmology were 22% and 8%, respectively, whereas conventional stratification by the type of provider location and number of beds explained 2% and 0.2% of variance, respectively. This study demonstrated that data mining methods can be used in designing efficient stratified sampling with variables readily available to the insurer and government; it offers an alternative to the existing stratification method that is widely used in healthcare provider surveys in South Korea.

  10. Stratified charge rotary engine combustion studies

    Science.gov (United States)

    Shock, H.; Hamady, F.; Somerton, C.; Stuecken, T.; Chouinard, E.; Rachal, T.; Kosterman, J.; Lambeth, M.; Olbrich, C.

    1989-07-01

    Analytical and experimental studies of the combustion process in a stratified charge rotary engine (SCRE) continue to be the subject of active research in recent years. Specifically to meet the demand for more sophisticated products, a detailed understanding of the engine system of interest is warranted. With this in mind the objective of this work is to develop an understanding of the controlling factors that affect the SCRE combustion process so that an efficient power dense rotary engine can be designed. The influence of the induction-exhaust systems and the rotor geometry are believed to have a significant effect on combustion chamber flow characteristics. In this report, emphasis is centered on Laser Doppler Velocimetry (LDV) measurements and on qualitative flow visualizations in the combustion chamber of the motored rotary engine assembly. This will provide a basic understanding of the flow process in the RCE and serve as a data base for verification of numerical simulations. Understanding fuel injection provisions is also important to the successful operation of the stratified charge rotary engine. Toward this end, flow visualizations depicting the development of high speed, high pressure fuel jets are described. Friction is an important consideration in an engine from the standpoint of lost work, durability and reliability. MSU Engine Research Laboratory efforts in accessing the frictional losses associated with the rotary engine are described. This includes work which describes losses in bearing, seal and auxillary components. Finally, a computer controlled mapping system under development is described. This system can be used to map shapes such as combustion chamber, intake manifolds or turbine blades accurately.

  11. Degradation of organic dyes using spray deposited nanocrystalline stratified WO3/TiO2 photoelectrodes under sunlight illumination

    Science.gov (United States)

    Hunge, Y. M.; Yadav, A. A.; Mahadik, M. A.; Bulakhe, R. N.; Shim, J. J.; Mathe, V. L.; Bhosale, C. H.

    2018-02-01

    The need to utilize TiO2 based metal oxide hetero nanostructures for the degradation of environmental pollutants like Rhodamine B and reactive red 152 from the wastewater using stratified WO3/TiO2 catalyst under sunlight illumination. WO3, TiO2 and stratified WO3/TiO2 catalysts were prepared by a spray pyrolysis method. It was found that the stratified WO3/TiO2 heterostructure has high crystallinity, no mixed phase formation occurs, strong optical absorption in the visible region of the solar spectrum, and large surface area. The photocatalytic activity was tested for degradation of Rhodamine B (Rh B) and reactive red 152 in an aqueous medium. TiO2 layer in stratified WO3/TiO2 catalyst helps to extend its absorption spectrum in the solar light region. Rh B and Reactive red 152is eliminated up to 98 and 94% within the 30 and 40 min respectively at optimum experimental condition by stratified WO3/TiO2. Moreover, stratified WO3/TiO2 photoelectrode has good stability and reusability than individual TiO2 and WO3 thin film in the degradation of Rh B and reactive red 152. The photoelectrocatalytic experimental results indicate that stratified WO3/TiO2 photoelectrode is a promising material for dye removal.

  12. The effect of surfactant on stratified and stratifying gas-liquid flows

    Science.gov (United States)

    Heiles, Baptiste; Zadrazil, Ivan; Matar, Omar

    2013-11-01

    We consider the dynamics of a stratified/stratifying gas-liquid flow in horizontal tubes. This flow regime is characterised by the thin liquid films that drain under gravity along the pipe interior, forming a pool at the bottom of the tube, and the formation of large-amplitude waves at the gas-liquid interface. This regime is also accompanied by the detachment of droplets from the interface and their entrainment into the gas phase. We carry out an experimental study involving axial- and radial-view photography of the flow, in the presence and absence of surfactant. We show that the effect of surfactant is to reduce significantly the average diameter of the entrained droplets, through a tip-streaming mechanism. We also highlight the influence of surfactant on the characteristics of the interfacial waves, and the pressure gradient that drives the flow. EPSRC Programme Grant EP/K003976/1.

  13. Simulation model of stratified thermal energy storage tank using finite difference method

    Science.gov (United States)

    Waluyo, Joko

    2016-06-01

    Stratified TES tank is normally used in the cogeneration plant. The stratified TES tanks are simple, low cost, and equal or superior in thermal performance. The advantage of TES tank is that it enables shifting of energy usage from off-peak demand for on-peak demand requirement. To increase energy utilization in a stratified TES tank, it is required to build a simulation model which capable to simulate the charging phenomenon in the stratified TES tank precisely. This paper is aimed to develop a novel model in addressing the aforementioned problem. The model incorporated chiller into the charging of stratified TES tank system in a closed system. The model was developed in one-dimensional type involve with heat transfer aspect. The model covers the main factors affect to degradation of temperature distribution namely conduction through the tank wall, conduction between cool and warm water, mixing effect on the initial flow of the charging as well as heat loss to surrounding. The simulation model is developed based on finite difference method utilizing buffer concept theory and solved in explicit method. Validation of the simulation model is carried out using observed data obtained from operating stratified TES tank in cogeneration plant. The temperature distribution of the model capable of representing S-curve pattern as well as simulating decreased charging temperature after reaching full condition. The coefficient of determination values between the observed data and model obtained higher than 0.88. Meaning that the model has capability in simulating the charging phenomenon in the stratified TES tank. The model is not only capable of generating temperature distribution but also can be enhanced for representing transient condition during the charging of stratified TES tank. This successful model can be addressed for solving the limitation temperature occurs in charging of the stratified TES tank with the absorption chiller. Further, the stratified TES tank can be

  14. Improved patient selection by stratified surgical intervention

    DEFF Research Database (Denmark)

    Wang, Miao; Bünger, Cody E; Li, Haisheng

    2015-01-01

    BACKGROUND CONTEXT: Choosing the best surgical treatment for patients with spinal metastases remains a significant challenge for spine surgeons. There is currently no gold standard for surgical treatments. The Aarhus Spinal Metastases Algorithm (ASMA) was established to help surgeons choose...... the most appropriate surgical intervention for patients with spinal metastases. PURPOSE: The purpose of this study was to evaluate the clinical outcome of stratified surgical interventions based on the ASMA, which combines life expectancy and the anatomical classification of patients with spinal metastases...... survival times in the five surgical groups determined by the ASMA were 2.1 (TS 0-4, TC 1-7), 5.1 (TS 5-8, TC 1-7), 12.1 (TS 9-11, TC 1-7 or TS 12-15, TC 7), 26.0 (TS 12-15, TC 4-6), and 36.0 (TS 12-15, TC 1-3) months. The 30-day mortality rate was 7.5%. Postoperative neurological function was maintained...

  15. Experimental study of unsteady thermally stratified flow

    International Nuclear Information System (INIS)

    Lee, Sang Jun; Chung, Myung Kyoon

    1985-01-01

    Unsteady thermally stratified flow caused by two-dimensional surface discharge of warm water into a oblong channel was investigated. Experimental study was focused on the rapidly developing thermal diffusion at small Richardson number. The basic objectives were to study the interfacial mixing between a flowing layer of warm water and an underlying body of cold water and to accumulate experimental data to test computational turbulence models. Mean velocity field measurements were carried out by using NMR-CT(Nuclear Magnetic Resonance-Computerized Tomography). It detects quantitative flow image of any desired section in any direction of flow in short time. Results show that at small Richardson number warm layer rapidly penetrates into the cold layer because of strong turbulent mixing and instability between the two layers. It is found that the transfer of heat across the interface is more vigorous than that of momentum. It is also proved that the NMR-CT technique is a very valuable tool to measure unsteady three dimensional flow field. (Author)

  16. Classification of archaeologically stratified pumice by INAA

    International Nuclear Information System (INIS)

    Peltz, C.; Bichler, M.

    2001-01-01

    In the framework of the research program 'Synchronization of Civilization in the Eastern Mediterranean Region in the 2nd Millenium B.C.' instrumental neutron activation analysis (INAA) was used to determine 30 elements in pumice from archaeological excavations to reveal their specific volcanic origin. The widespread pumiceous products of several eruptions in the Aegean region were used as abrasive tools and were therefore popular trade objects. A remarkable quantity of pumice and pumiceous tephra (several km 3 ) was produced by the 'Minoan eruption' of Thera (Santorini), which is assumed to have happened between 1450 and 1650 B.C. Thus the discovery of the primary fallout of 'Minoan' tephra in archaeologically stratified locations can be used as a relative time mark. Additionally, pumice lumps used as abrasive can serve for dating by first appearance. Essential to an identification of the primary volcanic source is the knowledge that pumices from the Aegean region can easily be distinguished by their trace element distribution patterns, as previous work has shown. The elements Al, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, Ti, U, V, Yb, Zn and Zr were determined in 16 samples of pumice lumps from excavations in Tell-el-Dab'a and Tell-el-Herr (Egypt). Two irradiation cycles and five measurement runs were applied. A reliable identification of the samples is achieved by comparing these results to the database compiled in previous studies. (author)

  17. Turbulent fluxes in stably stratified boundary layers

    International Nuclear Information System (INIS)

    L'vov, Victor S; Procaccia, Itamar; Rudenko, Oleksii

    2008-01-01

    We present here an extended version of an invited talk we gave at the international conference 'Turbulent Mixing and Beyond'. The dynamical and statistical description of stably stratified turbulent boundary layers with the important example of the stable atmospheric boundary layer in mind is addressed. Traditional approaches to this problem, based on the profiles of mean quantities, velocity second-order correlations and dimensional estimates of the turbulent thermal flux, run into a well-known difficulty, predicting the suppression of turbulence at a small critical value of the Richardson number, in contradiction to observations. Phenomenological attempts to overcome this problem suffer from various theoretical inconsistencies. Here, we present an approach taking into full account all the second-order statistics, which allows us to respect the conservation of total mechanical energy. The analysis culminates in an analytic solution of the profiles of all mean quantities and all second-order correlations, removing the unphysical predictions of previous theories. We propose that the approach taken here is sufficient to describe the lower parts of the atmospheric boundary layer, as long as the Richardson number does not exceed an order of unity. For much higher Richardson numbers, the physics may change qualitatively, requiring careful consideration of the potential Kelvin-Helmoholtz waves and their interaction with the vortical turbulence.

  18. Analysis of Turbulent Combustion in Simplified Stratified Charge Conditions

    Science.gov (United States)

    Moriyoshi, Yasuo; Morikawa, Hideaki; Komatsu, Eiji

    The stratified charge combustion system has been widely studied due to the significant potentials for low fuel consumption rate and low exhaust gas emissions. The fuel-air mixture formation process in a direct-injection stratified charge engine is influenced by various parameters, such as atomization, evaporation, and in-cylinder gas motion at high temperature and high pressure conditions. It is difficult to observe the in-cylinder phenomena in such conditions and also challenging to analyze the following stratified charge combustion. Therefore, the combustion phenomena in simplified stratified charge conditions aiming to analyze the fundamental stratified charge combustion are examined. That is, an experimental apparatus which can control the mixture distribution and the gas motion at ignition timing was developed, and the effects of turbulence intensity, mixture concentration distribution, and mixture composition on stratified charge combustion were examined. As a result, the effects of fuel, charge stratification, and turbulence on combustion characteristics were clarified.

  19. Longevity of Compositionally Stratified Layers in Ice Giants

    Science.gov (United States)

    Friedson, A. J.

    2017-12-01

    In the hydrogen-rich atmospheres of gas giants, a decrease with radius in the mixing ratio of a heavy species (e.g. He, CH4, H2O) has the potential to produce a density stratification that is convectively stable if the heavy species is sufficiently abundant. Formation of stable layers in the interiors of these planets has important implications for their internal structure, chemical mixing, dynamics, and thermal evolution, since vertical transport of heat and constituents in such layers is greatly reduced in comparison to that in convecting layers. Various processes have been suggested for creating compositionally stratified layers. In the interiors of Jupiter and Saturn, these include phase separation of He from metallic hydrogen and dissolution of dense core material into the surrounding metallic-H envelope. Condensation of methane and water has been proposed as a mechanism for producing stable zones in the atmospheres of Saturn and the ice giants. However, if a stably stratified layer is formed adjacent to an active region of convection, it may be susceptible to progressive erosion as the convection intrudes and entrains fluid into the unstable envelope. We discuss the principal factors that control the rate of entrainment and associated erosion and present a specific example concerning the longevity of stable layers formed by condensation of methane and water in Uranus and Neptune. We also consider whether the temporal variability of such layers may engender episodic behavior in the release of the internal heat of these planets. This research is supported by a grant from the NASA Solar System Workings Program.

  20. Stratified charge rotary engine critical technology enablement. Volume 2: Appendixes

    Science.gov (United States)

    Irion, C. E.; Mount, R. E.

    1992-01-01

    This second volume of appendixes is a companion to Volume 1 of this report which summarizes results of a critical technology enablement effort with the stratified charge rotary engine (SCRE) focusing on a power section of 0.67 liters (40 cu. in.) per rotor in single and two rotor versions. The work is a continuation of prior NASA Contracts NAS3-23056 and NAS3-24628. Technical objectives are multi-fuel capability, including civil and military jet fuel and DF-2, fuel efficiency of 0.355 Lbs/BHP-Hr. at best cruise condition above 50 percent power, altitude capability of up to 10Km (33,000 ft.) cruise, 2000 hour TBO and reduced coolant heat rejection. Critical technologies for SCRE's that have the potential for competitive performance and cost in a representative light-aircraft environment were examined. Objectives were: the development and utilization of advanced analytical tools, i.e. higher speed and enhanced three dimensional combustion modeling; identification of critical technologies; development of improved instrumentation; and to isolate and quantitatively identify the contribution to performance and efficiency of critical components or subsystems. A family of four-stage third-order explicit Runge-Kutta schemes is derived that required only two locations and has desirable stability characteristics. Error control is achieved by embedding a second-order scheme within the four-stage procedure. Certain schemes are identified that are as efficient and accurate as conventional embedded schemes of comparable order and require fewer storage locations.

  1. Modelling of vapour explosion in stratified geometrie

    International Nuclear Information System (INIS)

    Picchi, St.

    1999-01-01

    When a hot liquid comes into contact with a colder volatile liquid, one can obtain in some conditions an explosive vaporization, told vapour explosion, whose consequences can be important on neighbouring structures. This explosion needs the intimate mixing and the fine fragmentation between the two liquids. In a stratified vapour explosion, these two liquids are initially superposed and separated by a vapor film. A triggering of the explosion can induce a propagation of this along the film. A study of experimental results and existent models has allowed to retain the following main points: - the explosion propagation is due to a pressure wave propagating through the medium; - the mixing is due to the development of Kelvin-Helmholtz instabilities induced by the shear velocity between the two liquids behind the pressure wave. The presence of the vapour in the volatile liquid explains experimental propagation velocity and the velocity difference between the two fluids at the pressure wave crossing. A first model has been proposed by Brayer in 1994 in order to describe the fragmentation and the mixing of the two fluids. Results of the author do not show explosion propagation. We have therefore built a new mixing-fragmentation model based on the atomization phenomenon that develops itself during the pressure wave crossing. We have also taken into account the transient aspect of the heat transfer between fuel drops and the volatile liquid, and elaborated a model of transient heat transfer. These two models have been introduced in a multi-components, thermal, hydraulic code, MC3D. Results of calculation show a qualitative and quantitative agreement with experimental results and confirm basic options of the model. (author)

  2. Aligning the Economic Value of Companion Diagnostics and Stratified Medicines

    Directory of Open Access Journals (Sweden)

    Edward D. Blair

    2012-11-01

    Full Text Available The twin forces of payors seeking fair pricing and the rising costs of developing new medicines has driven a closer relationship between pharmaceutical companies and diagnostics companies, because stratified medicines, guided by companion diagnostics, offer better commercial, as well as clinical, outcomes. Stratified medicines have created clinical success and provided rapid product approvals, particularly in oncology, and indeed have changed the dynamic between drug and diagnostic developers. The commercial payback for such partnerships offered by stratified medicines has been less well articulated, but this has shifted as the benefits in risk management, pricing and value creation for all stakeholders become clearer. In this larger healthcare setting, stratified medicine provides both physicians and patients with greater insight on the disease and provides rationale for providers to understand cost-effectiveness of treatment. This article considers how the economic value of stratified medicine relationships can be recognized and translated into better outcomes for all healthcare stakeholders.

  3. Stratified polymer brushes from microcontact printing of polydopamine initiator on polymer brush surfaces.

    Science.gov (United States)

    Wei, Qiangbing; Yu, Bo; Wang, Xiaolong; Zhou, Feng

    2014-06-01

    Stratified polymer brushes are fabricated using microcontact printing (μCP) of initiator integrated polydopamine (PDOPBr) on polymer brush surfaces and the following surface initiated atom transfer radical polymerization (SI-ATRP). It is found that the surface energy, chemically active groups, and the antifouling ability of the polymer brushes affect transfer efficiency and adhesive stability of the polydopamine film. The stickiness of the PDOPBr pattern on polymer brush surfaces is stable enough to perform continuous μCP and SI-ATRP to prepare stratified polymer brushes with a 3D topography, which have broad applications in cell and protein patterning, biosensors, and hybrid surfaces. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Turbulent structure of stably stratified inhomogeneous flow

    Science.gov (United States)

    Iida, Oaki

    2018-04-01

    Effects of buoyancy force stabilizing disturbances are investigated on the inhomogeneous flow where disturbances are dispersed from the turbulent to non-turbulent field in the direction perpendicular to the gravity force. Attaching the fringe region, where disturbances are excited by the artificial body force, a Fourier spectral method is used for the inhomogeneous flow stirred at one side of the cuboid computational box. As a result, it is found that the turbulent kinetic energy is dispersed as layered structures elongated in the streamwise direction through the vibrating motion. A close look at the layered structures shows that they are flanked by colder fluids at the top and hotter fluids at the bottom, and hence vertically compressed and horizontally expanded by the buoyancy related to the countergradient heat flux, though they are punctuated by the vertical expansion of fluids at the forefront of the layered structures, which is related to the downgradient heat flux, indicating that the layered structures are gravity currents. However, the phase between temperature fluctuations and vertical velocity is shifted by π/2 rad, indicating that temperature fluctuations are generated by the propagation of internal gravity waves.

  5. The stratified H-index makes scientific impact transparent

    DEFF Research Database (Denmark)

    Würtz, Morten; Schmidt, Morten

    2017-01-01

    The H-index is widely used to quantify and standardize researchers' scientific impact. However, the H-index does not account for the fact that co-authors rarely contribute equally to a paper. Accordingly, we propose the use of a stratified H-index to measure scientific impact. The stratified H......-index supplements the conventional H-index with three separate H-indices: one for first authorships, one for second authorships and one for last authorships. The stratified H-index takes scientific output, quality and individual author contribution into account....

  6. 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)

  7. Experimental analysis of an oblique turbulent flame front propagating in a stratified flow

    Energy Technology Data Exchange (ETDEWEB)

    Galizzi, C.; Escudie, D. [Universite de Lyon, CNRS, CETHIL, INSA-Lyon, UMR5008, F-69621 Cedex (France)

    2010-12-15

    This paper details the experimental study of a turbulent V-shaped flame expanding in a nonhomogeneous premixed flow. Its aim is to characterize the effects of stratification on turbulent flame characteristics. The setup consists of a stationary V-shaped flame stabilized on a rod and expanding freely in a lean premixed methane-air flow. One of the two oblique fronts interacts with a stratified slice, which has an equivalence ratio close to one and a thickness greater than that of the flame front. Several techniques such as PIV and CH{sup *} chemiluminescence are used to investigate the instantaneous fields, while laser Doppler anemometry and thermocouples are combined with a concentration probe to provide information on the mean fields. First, in order to provide a reference, the homogeneous turbulent case is studied. Next, the stratified turbulent premixed flame is investigated. Results show significant modifications of the whole flame and of the velocity field upstream of the flame front. The analysis of the geometric properties of the stratified flame indicates an increase in flame brush thickness, closely related to the local equivalence ratio. (author)

  8. RANS Modeling of Stably Stratified Turbulent Boundary Layer Flows in OpenFOAM®

    Directory of Open Access Journals (Sweden)

    Wilson Jordan M.

    2015-01-01

    Full Text Available Quantifying mixing processes relating to the transport of heat, momentum, and scalar quantities of stably stratified turbulent geophysical flows remains a substantial task. In a stably stratified flow, such as the stable atmospheric boundary layer (SABL, buoyancy forces have a significant impact on the flow characteristics. This study investigates constant and stability-dependent turbulent Prandtl number (Prt formulations linking the turbulent viscosity (νt and diffusivity (κt for modeling applications of boundary layer flows. Numerical simulations of plane Couette flow and pressure-driven channel flow are performed using the Reynolds-averaged Navier-Stokes (RANS framework with the standard k-ε turbulence model. Results are compared with DNS data to evaluate model efficacy for predicting mean velocity and density fields. In channel flow simulations, a Prandtl number formulation for wall-bounded flows is introduced to alleviate overmixing of the mean density field. This research reveals that appropriate specification of Prt can improve predictions of stably stratified turbulent boundary layer flows.

  9. A Mechanism for Stratifying Lava Flows

    Science.gov (United States)

    Rice, A.

    2005-12-01

    Relict lava flows (e.g., komatiites) are often reported to be zoned in the vertical, each zone separated by a sharp contact. Such stratifications in igneous flows, both intrusive and extrusive, can be treated as analogues of suspended loads of sediments in rivers and streams, and hence amenable to quantitative treatment derived for the hydraulic environment as long as dynamic similitude is assured. Situations typically encountered in the hydraulic environment are streams carrying a bed load at the bottom of the stream, the bed load separated by a sharp horizon from a sediment load carried above it. This sediment load may be topped by others of decreasing density as one moves to the surface of the flow, with perhaps the uppermost layer clear of any suspended matter. Rules exist for estimating the thickness D of these loads: one of them is given by D ~ 4.4V3/rgcvs where V is the shear velocity or average velocity of the flow, r = (ρs - ρl)/ρl where ρs is the density of the suspended solid matter, ρl the density of the fluid, g the acceleration of gravity, c the concentration of the particulate content and vs the settling velocity. The settling velocity is secured through Stoke's Law and the velocity of the flow is given by V = R2/3S1/2/n where R is the hydraulic radius, S the gradient along which the fluid flows and n is the Manning Coefficient. In the igneous case, the bed load would be composed of primocrysts, i.e., of the first crystals to come out of solution as the flow cools along its run. This would leave the upper portions of the flow more evolved except perhaps for a quenched crust riding atop the flow. As the viscosity of the flow is dependent not only on temperature but on composition and crystal content, the mean velocity of each layer will be different from the layer above and below it. This requires shear at the interface of adjoining stratifications, which brings into play another mechanism: dispersive pressure (the Bagnold effect). Dispersive

  10. Internal and vorticity waves in decaying stratified flows

    Science.gov (United States)

    Matulka, A.; Cano, D.

    2009-04-01

    Most predictive models fail when forcing at the Rossby deformation Radius is important and a large range of scales have to be taken into account. When mixing of reactants or pollutants has to be accounted, the range of scales spans from hundreds of Kilometers to the Bachelor or Kolmogorov sub milimiter scales. We present some theoretical arguments to describe the flow in terms of the three dimensional vorticity equations, using a lengthscale related to the vorticity (or enstrophy ) transport. Effect of intermittent eddies and non-homogeneity of diffusion are also key issues in the environment because both stratification and rotation body forces are important and cause anisotropy/non-homogeneity. These problems need further theoretical, numerical and observational work and one approach is to try to maximize the relevant geometrical information in order to understand and therefore predict these complex environmental dispersive flows. The importance of the study of turbulence structure and its relevance in diffusion of contaminants in environmental flows is clear when we see the effect of environmental disasters such as the Prestige oil spill or the Chernobil radioactive cloud spread in the atmosphere. A series of Experiments have been performed on a strongly stratified two layer fluid consisting of Brine in the bottom and freshwater above in a 1 square meter tank. The evolution of the vortices after the passage of a grid is video recorded and Particle tracking is applied on small pliolite particles floating at the interface. The combination of internal waves and vertical vorticity produces two separate time scales that may produce resonances. The vorticity is seen to oscilate in a complex way, where the frecuency decreases with time.

  11. Sensitivity of the Geomagnetic Octupole to a Stably Stratified Layer in the Earth's Core

    Science.gov (United States)

    Yan, C.; Stanley, S.

    2017-12-01

    The presence of a stably stratified layer at the top of the core has long been proposed for Earth, based on evidence from seismology and geomagnetic secular variation. Geodynamo modeling offers a unique window to inspect the properties and dynamics in Earth's core. For example, numerical simulations have shown that magnetic field morphology is sensitive to the presence of stably stratified layers in a planet's core. Here we use the mMoSST numerical dynamo model to investigate the effects of a thin stably stratified layer at the top of the fluid outer core in Earth on the resulting large-scale geomagnetic field morphology. We find that the existence of a stable layer has significant influence on the octupolar component of the magnetic field in our models, whereas the quadrupole doesn't show an obvious trend. This suggests that observations of the geomagnetic field can be applied to provide information of the properties of this plausible stable layer, such as how thick and how stable this layer could be. Furthermore, we have examined whether the dominant thermal signature from mantle tomography at the core-mantle boundary (CMB) (a degree & order 2 spherical harmonic) can influence our results. We found that this heat flux pattern at the CMB has no outstanding effects on the quadrupole and octupole magnetic field components. Our studies suggest that if there is a stably stratified layer at the top of the Earth's core, it must be limited in terms of stability and thickness, in order to be compatible with the observed paleomagnetic record.

  12. The effect of existing turbulence on stratified shear instability

    Science.gov (United States)

    Kaminski, Alexis; Smyth, William

    2017-11-01

    Ocean turbulence is an essential process governing, for example, heat uptake by the ocean. In the stably-stratified ocean interior, this turbulence occurs in discrete events driven by vertical variations of the horizontal velocity. Typically, these events have been modelled by assuming an initially laminar stratified shear flow which develops wavelike instabilities, becomes fully turbulent, and then relaminarizes into a stable state. However, in the real ocean there is always some level of turbulence left over from previous events, and it is not yet understood how this turbulence impacts the evolution of future mixing events. Here, we perform a series of direct numerical simulations of turbulent events developing in stratified shear flows that are already at least weakly turbulent. We do so by varying the amplitude of the initial perturbations, and examine the subsequent development of the instability and the impact on the resulting turbulent fluxes. This work is supported by NSF Grant OCE1537173.

  13. Direct numerical simulation of thermally-stratified turbulent boundary layer subjected to adverse pressure gradient

    International Nuclear Information System (INIS)

    Hattori, Hirofumi; Kono, Amane; Houra, Tomoya

    2016-01-01

    Highlights: • We study various thermally-stratified turbulent boundary layers having adverse pressure gradient (APG) by means of DNS. • The detailed turbulent statistics and structures in various thermally-stratified turbulent boundary layers having APG are discussed. • It is found that the friction coefficient and Stanton number decrease along the streamwise direction due to the effects of stable thermal stratification and APG, but those again increase due to the APG effect in the case of weak stable thermal stratification. • In the case of strong stable stratification with or without APG, the flow separation is observed in the downstream region. - Abstract: The objective of this study is to investigate and observe turbulent heat transfer structures and statistics in thermally-stratified turbulent boundary layers subjected to a non-equilibrium adverse pressure gradient (APG) by means of direct numerical simulation (DNS). DNSs are carried out under conditions of neutral, stable and unstable thermal stratifications with a non-equilibrium APG, in which DNS results reveal heat transfer characteristics of thermally-stratified non-equilibrium APG turbulent boundary layers. In cases of thermally-stratified turbulent boundary layers affected by APG, heat transfer performances increase in comparison with a turbulent boundary layer with neutral thermal stratification and zero pressure gradient (ZPG). Especially, it is found that the friction coefficient and Stanton number decrease along the streamwise direction due to the effects of stable thermal stratification and APG, but those again increase due to the APG effect in the case of weak stable thermal stratification (WSBL). Thus, the analysis for both the friction coefficient and Stanton number in the case of WSBL with/without APG is conducted using the FIK identity in order to investigate contributions from the transport equations, in which it is found that both Reynolds-shear-stress and the mean convection terms

  14. Salinization in a stratified aquifer induced by heat transfer from well casings

    Science.gov (United States)

    van Lopik, Jan H.; Hartog, Niels; Zaadnoordijk, Willem Jan; Cirkel, D. Gijsbert; Raoof, Amir

    2015-12-01

    The temperature inside wells used for gas, oil and geothermal energy production, as well as steam injection, is in general significantly higher than the groundwater temperature at shallower depths. While heat loss from these hot wells is known to occur, the extent to which this heat loss may result in density-driven flow and in mixing of surrounding groundwater has not been assessed so far. However, based on the heat and solute effects on density of this arrangement, the induced temperature contrasts in the aquifer due to heat transfer are expected to destabilize the system and result in convection, while existing salt concentration contrasts in an aquifer would act to stabilize the system. To evaluate the degree of impact that may occur under field conditions, free convection in a 50-m-thick aquifer driven by the heat loss from penetrating hot wells was simulated using a 2D axisymmetric SEAWAT model. In particular, the salinization potential of fresh groundwater due to the upward movement of brackish or saline water in a stratified aquifer is studied. To account for a large variety of well applications and configurations, as well as different penetrated aquifer systems, a wide range of well temperatures, from 40 to 100 °C, together with a range of salt concentration (1-35 kg/m3) contrasts were considered. This large temperature difference with the native groundwater (15 °C) required implementation of a non-linear density equation of state in SEAWAT. We show that density-driven groundwater flow results in a considerable salt mass transport (up to 166,000 kg) to the top of the aquifer in the vicinity of the well (radial distance up to 91 m) over a period of 30 years. Sensitivity analysis showed that density-driven groundwater flow and the upward salt transport was particularly enhanced by the increased heat transport from the well into the aquifer by thermal conduction due to increased well casing temperature, thermal conductivity of the soil, as well as decreased

  15. Large eddy simulation of turbulent and stably-stratified flows

    International Nuclear Information System (INIS)

    Fallon, Benoit

    1994-01-01

    The unsteady turbulent flow over a backward-facing step is studied by mean of Large Eddy Simulations with structure function sub grid model, both in isothermal and stably-stratified configurations. Without stratification, the flow develops highly-distorted Kelvin-Helmholtz billows, undergoing to helical pairing, with A-shaped vortices shed downstream. We show that forcing injected by recirculation fluctuations governs this oblique mode instabilities development. The statistical results show good agreements with the experimental measurements. For stably-stratified configurations, the flow remains more bi-dimensional. We show with increasing stratification, how the shear layer growth is frozen by inhibition of pairing process then of Kelvin-Helmholtz instabilities, and the development of gravity waves or stable density interfaces. Eddy structures of the flow present striking analogies with the stratified mixing layer. Additional computations show the development of secondary Kelvin-Helmholtz instabilities on the vorticity layers between two primary structures. This important mechanism based on baroclinic effects (horizontal density gradients) constitutes an additional part of the turbulent mixing process. Finally, the feasibility of Large Eddy Simulation is demonstrated for industrial flows, by studying a complex stratified cavity. Temperature fluctuations are compared to experimental measurements. We also develop three-dimensional un-stationary animations, in order to understand and visualize turbulent interactions. (author) [fr

  16. Bacterial production, protozoan grazing, and mineralization in stratified Lake Vechten

    NARCIS (Netherlands)

    Bloem, J.

    1989-01-01

    The role of heterotrophic nanoflagellates (HNAN, size 2-20 μm) in grazing on bacteria and mineralization of organic matter in stratified Lake Vechten was studied.

    Quantitative effects of manipulation and fixation on HNAN were checked. Considerable losses were caused by

  17. The dynamics of small inertial particles in weakly stratified turbulence

    NARCIS (Netherlands)

    van Aartrijk, M.; Clercx, H.J.H.

    We present an overview of a numerical study on the small-scale dynamics and the large-scale dispersion of small inertial particles in stably stratified turbulence. Three types of particles are examined: fluid particles, light inertial particles (with particle-to-fluid density ratio 1Ͽp/Ͽf25) and

  18. Dispersion of (light) inertial particles in stratified turbulence

    NARCIS (Netherlands)

    van Aartrijk, M.; Clercx, H.J.H.; Armenio, Vincenzo; Geurts, Bernardus J.; Fröhlich, Jochen

    2010-01-01

    We present a brief overview of a numerical study of the dispersion of particles in stably stratified turbulence. Three types of particles arc examined: fluid particles, light inertial particles ($\\rho_p/\\rho_f = \\mathcal{O}(1)$) and heavy inertial particles ($\\rho_p/\\rho_f \\gg 1$). Stratification

  19. On Internal Waves in a Density-Stratified Estuary

    NARCIS (Netherlands)

    Kranenburg, C.

    1991-01-01

    In this article some field observations, made in recent years, of internal wave motions in a density-stratified estuary are presented, In order to facilitate the appreciation of the results, and to make some quantitative comparisons, the relevant theory is also summarized. Furthermore, the origins

  20. FDTD scattered field formulation for scatterers in stratified dispersive media.

    Science.gov (United States)

    Olkkonen, Juuso

    2010-03-01

    We introduce a simple scattered field (SF) technique that enables finite difference time domain (FDTD) modeling of light scattering from dispersive objects residing in stratified dispersive media. The introduced SF technique is verified against the total field scattered field (TFSF) technique. As an application example, we study surface plasmon polariton enhanced light transmission through a 100 nm wide slit in a silver film.

  1. Plane Stratified Flow in a Room Ventilated by Displacement Ventilation

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm; Nickel, J.; Baron, D. J. G.

    2004-01-01

    The air movement in the occupied zone of a room ventilated by displacement ventilation exists as a stratified flow along the floor. This flow can be radial or plane according to the number of wall-mounted diffusers and the room geometry. The paper addresses the situations where plane flow...

  2. Dual Spark Plugs For Stratified-Charge Rotary Engine

    Science.gov (United States)

    Abraham, John; Bracco, Frediano V.

    1996-01-01

    Fuel efficiency of stratified-charge, rotary, internal-combustion engine increased by improved design featuring dual spark plugs. Second spark plug ignites fuel on upstream side of main fuel injector; enabling faster burning and more nearly complete utilization of fuel.

  3. Prognosis research strategy (PROGRESS) 4: Stratified medicine research

    NARCIS (Netherlands)

    A. Hingorani (Aroon); D.A.W.M. van der Windt (Daniëlle); R.D. Riley (Richard); D. Abrams; K.G.M. Moons (Karel); E.W. Steyerberg (Ewout); S. Schroter (Sara); W. Sauerbrei (Willi); D.G. Altman (Douglas); H. Hemingway; A. Briggs (Andrew); N. Brunner; P. Croft (Peter); J. Hayden (Jill); P.A. Kyzas (Panayiotis); N. Malats (Núria); G. Peat; P. Perel (Pablo); I. Roberts (Ian); A. Timmis (Adam)

    2013-01-01

    textabstractIn patients with a particular disease or health condition, stratified medicine seeks to identify thosewho will have the most clinical benefit or least harm from a specific treatment. In this article, thefourth in the PROGRESS series, the authors discuss why prognosis research should form

  4. Economic viability of Stratified Medicine concepts: An investor perspective on drivers and conditions that favour using Stratified Medicine approaches in a cost-contained healthcare environment.

    Science.gov (United States)

    Fugel, Hans-Joerg; Nuijten, Mark; Postma, Maarten

    2016-12-25

    Stratified Medicine (SM) is becoming a natural result of advances in biomedical science and a promising path for the innovation-based biopharmaceutical industry to create new investment opportunities. While the use of biomarkers to improve R&D efficiency and productivity is very much acknowledged by industry, much work remains to be done to understand the drivers and conditions that favour using a stratified approach to create economically viable products and to justify the investment in SM interventions as a stratification option. In this paper we apply a decision analytical methodology to address the economic attractiveness of different SM development options in a cost-contained healthcare environment. For this purpose, a hypothetical business case in the oncology market has been developed considering four feasible development scenarios. The article outlines the effects of development time and time to peak sales as key economic value drivers influencing profitability of SM interventions under specific conditions. If regulatory and reimbursement challenges can be solved, decreasing development time and enhancing early market penetration would most directly improve the economic attractiveness of SM interventions. Appropriate tailoring of highly differentiated patient subgroups is the prerequisite to leverage potential efficiency gains in the R&D process. Also, offering a better targeted and hence ultimately more cost-effective therapy at reimbursable prices will facilitate time to market access and allow increasing market share gains within the targeted populations. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Effect of Decreasing Cobalt Content on the Electrochemical Properties and Structural Stability of Li_(1-x)Ni_(y)Co_(z)Al_(0.05)O_(2) Type Cathode Materials

    OpenAIRE

    Ghatak, Kamalika; Kumar, Hemant; Nadimpalli, Siva; Datta, Dibakar

    2017-01-01

    In Lithium ion batteries (LIBs), proper design of cathode materials influences its intercalation behavior, overall cost, structural stability, and its impact on environment. At present, the most common type of cathode materials, NCA , has very high cobalt concentration. Since cobalt is toxic and expensive, the existing design of cathode materials is not cost-effective, and environmentally benign. However, these immensely important issues have not yet been properly addressed. Therefore, we hav...

  6. Exploring the role of wave drag in the stable stratified oceanic and atmospheric bottom boundary layer in the cnrs-toulouse (cnrm-game) large stratified water flume

    NARCIS (Netherlands)

    Kleczek, M.; Steeneveld, G.J.; Paci, A.; Calmer, R.; Belleudy, A.; Canonici, J.C.; Murguet, F.; Valette, V.

    2014-01-01

    This paper reports on a laboratory experiment in the CNRM-GAME (Toulouse) stratified water flume of a stably stratified boundary layer, in order to quantify the momentum transfer due to orographically induced gravity waves by gently undulating hills in a boundary layer flow. In a stratified fluid, a

  7. Standing Stability in Knee Osteoarthritis Patients

    Directory of Open Access Journals (Sweden)

    M.T. Karimi

    2016-09-01

    Full Text Available Aims: Being prevalent in the more than 40 years old persons, the knee osteoarthritis is one of the main factors in the function system failure mainly affecting their life. There is a type of instability in the persons with knee osteoarthritis, which is an increase in the domain and frequency of body pressure center. The aim of the present study was to compare the standing stability parameters in persons with knee osteoarthritis and healthy persons. Instrument & Methods: In this case-control, 15 patients with knee osteoarthritis referred to the physiotherapy clinic of the rehabilitation center and Al-Zahra hospital were studied in the muscle-skeletal research center of Isfahan University of Medical Sciences in 2015. The subjects were selected via stratified sampling method. As control group, 15 healthy persons were also studied in Isfahan. Total path length and the domain and frequency of pressure center in different directions were measured to assess the stability. Data was analyzed by SPSS 19 software using descriptive statistics and paired T test. Findings: There were increases in the mean movement domain and the frequency of pressure center in the anterior-posterior and the internal-external directions, as well as in the total path proceeded by the pressure center in the internal-external direction, in the persons with knee osteoarthritis than the healthy persons (p0.05. Conclusion: Standing stability and balance in persons with knee osteoarthritis decreases compared to healthy persons.

  8. Simulation of steam explosion in stratified melt-coolant configuration

    International Nuclear Information System (INIS)

    Leskovar, Matjaž; Centrih, Vasilij; Uršič, Mitja

    2016-01-01

    Highlights: • Strong steam explosions may develop spontaneously in stratified configurations. • Considerable melt-coolant premixed layer formed in subcooled water with hot melts. • Analysis with MC3D code provided insight into stratified steam explosion phenomenon. • Up to 25% of poured melt was mixed with water and available for steam explosion. • Better instrumented experiments needed to determine dominant mixing process. - Abstract: A steam explosion is an energetic fuel coolant interaction process, which may occur during a severe reactor accident when the molten core comes into contact with the coolant water. In nuclear reactor safety analyses steam explosions are primarily considered in melt jet-coolant pool configurations where sufficiently deep coolant pool conditions provide complete jet breakup and efficient premixture formation. Stratified melt-coolant configurations, i.e. a molten melt layer below a coolant layer, were up to now believed as being unable to generate strong explosive interactions. Based on the hypothesis that there are no interfacial instabilities in a stratified configuration it was assumed that the amount of melt in the premixture is insufficient to produce strong explosions. However, the recently performed experiments in the PULiMS and SES (KTH, Sweden) facilities with oxidic corium simulants revealed that strong steam explosions may develop spontaneously also in stratified melt-coolant configurations, where with high temperature melts and subcooled water conditions a considerable melt-coolant premixed layer is formed. In the article, the performed study of steam explosions in a stratified melt-coolant configuration in PULiMS like conditions is presented. The goal of this analytical work is to supplement the experimental activities within the PULiMS research program by addressing the key questions, especially regarding the explosivity of the formed premixed layer and the mechanisms responsible for the melt-water mixing. To

  9. Identification of major planktonic sulfur oxidizers in stratified freshwater lake.

    Directory of Open Access Journals (Sweden)

    Hisaya Kojima

    Full Text Available Planktonic sulfur oxidizers are important constituents of ecosystems in stratified water bodies, and contribute to sulfide detoxification. In contrast to marine environments, taxonomic identities of major planktonic sulfur oxidizers in freshwater lakes still remain largely unknown. Bacterioplankton community structure was analyzed in a stratified freshwater lake, Lake Mizugaki in Japan. In the clone libraries of 16S rRNA gene, clones very closely related to a sulfur oxidizer isolated from this lake, Sulfuritalea hydrogenivorans, were detected in deep anoxic water, and occupied up to 12.5% in each library of different water depth. Assemblages of planktonic sulfur oxidizers were specifically analyzed by constructing clone libraries of genes involved in sulfur oxidation, aprA, dsrA, soxB and sqr. In the libraries, clones related to betaproteobacteria were detected with high frequencies, including the close relatives of Sulfuritalea hydrogenivorans.

  10. Study of MRI in stratified viscous plasma configuration

    Science.gov (United States)

    Carlevaro, Nakia; Montani, Giovanni; Renzi, Fabrizio

    2017-02-01

    We analyze the morphology of the magneto-rotational instability (MRI) for a stratified viscous plasma disk configuration in differential rotation, taking into account the so-called corotation theorem for the background profile. In order to select the intrinsic Alfvénic nature of MRI, we deal with an incompressible plasma and we adopt a formulation of the local perturbation analysis based on the use of the magnetic flux function as a dynamical variable. Our study outlines, as consequence of the corotation condition, a marked asymmetry of the MRI with respect to the equatorial plane, particularly evident in a complete damping of the instability over a positive critical height on the equatorial plane. We also emphasize how such a feature is already present (although less pronounced) even in the ideal case, restoring a dependence of the MRI on the stratified morphology of the gravitational field.

  11. Mixing of stratified flow around bridge piers in steady current

    DEFF Research Database (Denmark)

    Jensen, Bjarne; Carstensen, Stefan; Christensen, Erik Damgaard

    2018-01-01

    This paper presents the results of an experimental and numerical investigation of the mixing of stratified flow around bridge pier structures. In this study, which was carried out in connection with the Fehmarnbelt Fixed Link environmental impact assessment, the mixing processes of two-layer stra......This paper presents the results of an experimental and numerical investigation of the mixing of stratified flow around bridge pier structures. In this study, which was carried out in connection with the Fehmarnbelt Fixed Link environmental impact assessment, the mixing processes of two......-layer stratification was studied in which the lower level had a higher salinity than the upper layer. The physical experiments investigated two different pier designs. A general study was made regarding forces on the piers in which the effect of the current angle relative to the structure was also included...

  12. Stratified charge rotary aircraft engine technology enablement program

    Science.gov (United States)

    Badgley, P. R.; Irion, C. E.; Myers, D. M.

    1985-01-01

    The multifuel stratified charge rotary engine is discussed. A single rotor, 0.7L/40 cu in displacement, research rig engine was tested. The research rig engine was designed for operation at high speeds and pressures, combustion chamber peak pressure providing margin for speed and load excursions above the design requirement for a high is advanced aircraft engine. It is indicated that the single rotor research rig engine is capable of meeting the established design requirements of 120 kW, 8,000 RPM, 1,379 KPA BMEP. The research rig engine, when fully developed, will be a valuable tool for investigating, advanced and highly advanced technology components, and provide an understanding of the stratified charge rotary engine combustion process.

  13. Analysis of photonic band-gap structures in stratified medium

    DEFF Research Database (Denmark)

    Tong, Ming-Sze; Yinchao, Chen; Lu, Yilong

    2005-01-01

    in electromagnetic and microwave applications once the Maxwell's equations are appropriately modeled. Originality/value - The method validates its values and properties through extensive studies on regular and defective 1D PBG structures in stratified medium, and it can be further extended to solving more......Purpose - To demonstrate the flexibility and advantages of a non-uniform pseudo-spectral time domain (nu-PSTD) method through studies of the wave propagation characteristics on photonic band-gap (PBG) structures in stratified medium Design/methodology/approach - A nu-PSTD method is proposed...... in solving the Maxwell's equations numerically. It expands the temporal derivatives using the finite differences, while it adopts the Fourier transform (FT) properties to expand the spatial derivatives in Maxwell's equations. In addition, the method makes use of the chain-rule property in calculus together...

  14. Community genomics among stratified microbial assemblages in the ocean's interior

    DEFF Research Database (Denmark)

    DeLong, Edward F; Preston, Christina M; Mincer, Tracy

    2006-01-01

    Microbial life predominates in the ocean, yet little is known about its genomic variability, especially along the depth continuum. We report here genomic analyses of planktonic microbial communities in the North Pacific Subtropical Gyre, from the ocean's surface to near-sea floor depths. Sequence......, and host-viral interactions. Comparative genomic analyses of stratified microbial communities have the potential to provide significant insight into higher-order community organization and dynamics....

  15. Large Eddy Simulation of stratified flows over structures

    OpenAIRE

    Brechler J.; Fuka V.

    2013-01-01

    We tested the ability of the LES model CLMM (Charles University Large-Eddy Microscale Model) to model the stratified flow around three dimensional hills. We compared the quantities, as the height of the dividing streamline, recirculation zone length or length of the lee waves with experiments by Hunt and Snyder[3] and numerical computations by Ding, Calhoun and Street[5]. The results mostly agreed with the references, but some important differences are present.

  16. Large Eddy Simulation of stratified flows over structures

    Directory of Open Access Journals (Sweden)

    Brechler J.

    2013-04-01

    Full Text Available We tested the ability of the LES model CLMM (Charles University Large-Eddy Microscale Model to model the stratified flow around three dimensional hills. We compared the quantities, as the height of the dividing streamline, recirculation zone length or length of the lee waves with experiments by Hunt and Snyder[3] and numerical computations by Ding, Calhoun and Street[5]. The results mostly agreed with the references, but some important differences are present.

  17. Large Eddy Simulation of stratified flows over structures

    Science.gov (United States)

    Fuka, V.; Brechler, J.

    2013-04-01

    We tested the ability of the LES model CLMM (Charles University Large-Eddy Microscale Model) to model the stratified flow around three dimensional hills. We compared the quantities, as the height of the dividing streamline, recirculation zone length or length of the lee waves with experiments by Hunt and Snyder[3] and numerical computations by Ding, Calhoun and Street[5]. The results mostly agreed with the references, but some important differences are present.

  18. Propagation of acoustic waves in a stratified atmosphere, 1

    Science.gov (United States)

    Kalkofen, W.; Rossi, P.; Bodo, G.; Massaglia, S.

    1994-01-01

    This work is motivated by the chromospheric 3 minute oscillations observed in the K(sub 2v) bright points. We study acoustic gravity waves in a one-dimensional, gravitationally stratified, isothermal atmosphere. The oscillations are excited either by a velocity pulse imparted to a layer in an atmosphere of infinite vertical extent, or by a piston forming the lower boundary of a semi-infinite medium. We consider both linear and non-linear waves.

  19. A statistical mechanics approach to mixing in stratified fluids

    OpenAIRE

    Venaille , Antoine; Gostiaux , Louis; Sommeria , Joël

    2016-01-01

    Accepted for the Journal of Fluid Mechanics; Predicting how much mixing occurs when a given amount of energy is injected into a Boussinesq fluid is a longstanding problem in stratified turbulence. The huge number of degrees of freedom involved in these processes renders extremely difficult a deterministic approach to the problem. Here we present a statistical mechanics approach yielding a prediction for a cumulative, global mixing efficiency as a function of a global Richard-son number and th...

  20. Sutudy on exchange flow under the unstably stratified field

    OpenAIRE

    文沢, 元雄

    2005-01-01

    This paper deals with the exchange flow under the unstably stratified field. The author developed the effective measurement system as well as the numerical analysis program. The system and the program are applied to the helium-air exchange flow in a rectangular channel with inclination. Following main features of the exchange flow were discussed based on the calculated results.(1) Time required for establishing a quasi-steady state exchange flow.(2) The relationship between the inclination an...

  1. Background stratified Poisson regression analysis of cohort data.

    Science.gov (United States)

    Richardson, David B; Langholz, Bryan

    2012-03-01

    Background stratified Poisson regression is an approach that has been used in the analysis of data derived from a variety of epidemiologically important studies of radiation-exposed populations, including uranium miners, nuclear industry workers, and atomic bomb survivors. We describe a novel approach to fit Poisson regression models that adjust for a set of covariates through background stratification while directly estimating the radiation-disease association of primary interest. The approach makes use of an expression for the Poisson likelihood that treats the coefficients for stratum-specific indicator variables as 'nuisance' variables and avoids the need to explicitly estimate the coefficients for these stratum-specific parameters. Log-linear models, as well as other general relative rate models, are accommodated. This approach is illustrated using data from the Life Span Study of Japanese atomic bomb survivors and data from a study of underground uranium miners. The point estimate and confidence interval obtained from this 'conditional' regression approach are identical to the values obtained using unconditional Poisson regression with model terms for each background stratum. Moreover, it is shown that the proposed approach allows estimation of background stratified Poisson regression models of non-standard form, such as models that parameterize latency effects, as well as regression models in which the number of strata is large, thereby overcoming the limitations of previously available statistical software for fitting background stratified Poisson regression models.

  2. Stratified source-sampling techniques for Monte Carlo eigenvalue analysis

    International Nuclear Information System (INIS)

    Mohamed, A.

    1998-01-01

    In 1995, at a conference on criticality safety, a special session was devoted to the Monte Carlo ''Eigenvalue of the World'' problem. Argonne presented a paper, at that session, in which the anomalies originally observed in that problem were reproduced in a much simplified model-problem configuration, and removed by a version of stratified source-sampling. In this paper, stratified source-sampling techniques are generalized and applied to three different Eigenvalue of the World configurations which take into account real-world statistical noise sources not included in the model problem, but which differ in the amount of neutronic coupling among the constituents of each configuration. It is concluded that, in Monte Carlo eigenvalue analysis of loosely-coupled arrays, the use of stratified source-sampling reduces the probability of encountering an anomalous result over that if conventional source-sampling methods are used. However, this gain in reliability is substantially less than that observed in the model-problem results

  3. Ethanol dehydration to ethylene in a stratified autothermal millisecond reactor.

    Science.gov (United States)

    Skinner, Michael J; Michor, Edward L; Fan, Wei; Tsapatsis, Michael; Bhan, Aditya; Schmidt, Lanny D

    2011-08-22

    The concurrent decomposition and deoxygenation of ethanol was accomplished in a stratified reactor with 50-80 ms contact times. The stratified reactor comprised an upstream oxidation zone that contained Pt-coated Al(2)O(3) beads and a downstream dehydration zone consisting of H-ZSM-5 zeolite films deposited on Al(2)O(3) monoliths. Ethanol conversion, product selectivity, and reactor temperature profiles were measured for a range of fuel:oxygen ratios for two autothermal reactor configurations using two different sacrificial fuel mixtures: a parallel hydrogen-ethanol feed system and a series methane-ethanol feed system. Increasing the amount of oxygen relative to the fuel resulted in a monotonic increase in ethanol conversion in both reaction zones. The majority of the converted carbon was in the form of ethylene, where the ethanol carbon-carbon bonds stayed intact while the oxygen was removed. Over 90% yield of ethylene was achieved by using methane as a sacrificial fuel. These results demonstrate that noble metals can be successfully paired with zeolites to create a stratified autothermal reactor capable of removing oxygen from biomass model compounds in a compact, continuous flow system that can be configured to have multiple feed inputs, depending on process restrictions. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Background stratified Poisson regression analysis of cohort data

    International Nuclear Information System (INIS)

    Richardson, David B.; Langholz, Bryan

    2012-01-01

    Background stratified Poisson regression is an approach that has been used in the analysis of data derived from a variety of epidemiologically important studies of radiation-exposed populations, including uranium miners, nuclear industry workers, and atomic bomb survivors. We describe a novel approach to fit Poisson regression models that adjust for a set of covariates through background stratification while directly estimating the radiation-disease association of primary interest. The approach makes use of an expression for the Poisson likelihood that treats the coefficients for stratum-specific indicator variables as 'nuisance' variables and avoids the need to explicitly estimate the coefficients for these stratum-specific parameters. Log-linear models, as well as other general relative rate models, are accommodated. This approach is illustrated using data from the Life Span Study of Japanese atomic bomb survivors and data from a study of underground uranium miners. The point estimate and confidence interval obtained from this 'conditional' regression approach are identical to the values obtained using unconditional Poisson regression with model terms for each background stratum. Moreover, it is shown that the proposed approach allows estimation of background stratified Poisson regression models of non-standard form, such as models that parameterize latency effects, as well as regression models in which the number of strata is large, thereby overcoming the limitations of previously available statistical software for fitting background stratified Poisson regression models. (orig.)

  5. Controls on Turbulent Mixing in a Strongly Stratified and Sheared Tidal River Plume

    Energy Technology Data Exchange (ETDEWEB)

    Jurisa, Joseph T.; Nash, Jonathan D.; Moum, James N.; Kilcher, Levi F.

    2016-08-01

    Considerable effort has been made to parameterize turbulent kinetic energy (TKE) dissipation rate ..epsilon.. and mixing in buoyant plumes and stratified shear flows. Here, a parameterization based on Kunze et al. is examined, which estimates ..epsilon.. as the amount of energy contained in an unstable shear layer (Ri < Ric) that must be dissipated to increase the Richardson number Ri = N2/S2 to a critical value Ric within a turbulent decay time scale. Observations from the tidal Columbia River plume are used to quantitatively assess the relevant parameters controlling ..epsilon.. over a range of tidal and river discharge forcings. Observed ..epsilon.. is found to be characterized by Kunze et al.'s form within a factor of 2, while exhibiting slightly decreased skill near Ri = Ric. Observed dissipation rates are compared to estimates from a constant interfacial drag formulation that neglects the direct effects of stratification. This is found to be appropriate in energetic regimes when the bulk-averaged Richardson number Rib is less than Ric/4. However, when Rib > Ric/4, the effects of stratification must be included. Similarly, ..epsilon.. scaled by the bulk velocity and density differences over the plume displays a clear dependence on Rib, decreasing as Rib approaches Ric. The Kunze et al. ..epsilon.. parameterization is modified to form an expression for the nondimensional dissipation rate that is solely a function of Rib, displaying good agreement with the observations. It is suggested that this formulation is broadly applicable for unstable to marginally unstable stratified shear flows.

  6. Evaluation of different toxicity assays applied to proliferating cells and to stratified epithelium in relation to permeability enhancement with glycocholate

    DEFF Research Database (Denmark)

    Eirheim, Heidi Ugelstad; Bundgaard, Christoffer; Nielsen, Hanne Mørck

    2004-01-01

    The purpose of the present study was to evaluate different toxicity assays for use on proliferating buccal TR146 cells and on stratified TR146 epithelium and to compare these results to the permeability enhancing effect of glycocholate (GC). Both the proliferating cells and the epithelium were...... across the epithelium concurrent with a decrease in the transepithelial electrical resistance (TEER) was also determined. The robustness of the epithelium was significantly higher than that of the proliferating cells (P...

  7. Numerical simulations of the stratified oceanic bottom boundary layer

    Science.gov (United States)

    Taylor, John R.

    Numerical simulations are used to consider several problems relevant to the turbulent oceanic bottom boundary layer. In the first study, stratified open channel flow is considered with thermal boundary conditions chosen to approximate a shallow sea. Specifically, a constant heat flux is applied at the free surface and the lower wall is assumed to be adiabatic. When the surface heat flux is strong, turbulent upwellings of low speed fluid from near the lower wall are inhibited by the stable stratification. Subsequent studies consider a stratified bottom Ekman layer over a non-sloping lower wall. The influence of the free surface is removed by using an open boundary condition at the top of the computational domain. Particular attention is paid to the influence of the outer layer stratification on the boundary layer structure. When the density field is initialized with a linear profile, a turbulent mixed layer forms near the wall, which is separated from the outer layer by a strongly stable pycnocline. It is found that the bottom stress is not strongly affected by the outer layer stratification. However, stratification reduces turbulent transport to the outer layer and strongly limits the boundary layer height. The mean shear at the top of the boundary layer is enhanced when the outer layer is stratified, and this shear is strong enough to cause intermittent instabilities above the pycnocline. Turbulence-generated internal gravity waves are observed in the outer layer with a relatively narrow frequency range. An explanation for frequency content of these waves is proposed, starting with an observed broad-banded turbulent spectrum and invoking linear viscous decay to explain the preferential damping of low and high frequency waves. During the course of this work, an open-source computational fluid dynamics code has been developed with a number of advanced features including scalar advection, subgrid-scale models for large-eddy simulation, and distributed memory

  8. Direct contact condensation induced transition from stratified to slug flow

    International Nuclear Information System (INIS)

    Strubelj, Luka; Ezsoel, Gyoergy; Tiselj, Iztok

    2010-01-01

    Selected condensation-induced water hammer experiments performed on PMK-2 device were numerically modelled with three-dimensional two-fluid models of computer codes NEPTUNE C FD and CFX. Experimental setup consists of the horizontal pipe filled with the hot steam that is being slowly flooded with cold water. In most of the experimental cases, slow flooding of the pipe was abruptly interrupted by a strong slugging and water hammer, while in the selected experimental runs performed at higher initial pressures and temperatures that are analysed in the present work, the transition from the stratified into the slug flow was not accompanied by the water hammer pressure peak. That makes these cases more suitable tests for evaluation of the various condensation models in the horizontally stratified flows and puts them in the range of the available CFD (Computational Fluid Dynamics) codes. The key models for successful simulation appear to be the condensation model of the hot vapour on the cold liquid and the interfacial momentum transfer model. The surface renewal types of condensation correlations, developed for condensation in the stratified flows, were used in the simulations and were applied also in the regions of the slug flow. The 'large interface' model for inter-phase momentum transfer model was compared to the bubble drag model. The CFD simulations quantitatively captured the main phenomena of the experiments, while the stochastic nature of the particular condensation-induced water hammer experiments did not allow detailed prediction of the time and position of the slug formation in the pipe. We have clearly shown that even the selected experiments without water hammer present a tough test for the applied CFD codes, while modelling of the water hammer pressure peaks in two-phase flow, being a strongly compressible flow phenomena, is beyond the capability of the current CFD codes.

  9. Technetium reduction and removal in a stratified fjord

    International Nuclear Information System (INIS)

    Keith-Roach, M.; Roos, P.

    2002-01-01

    The distribution of Tc in the water columns of a stratified fjord has been measured to investigate the behaviour and fate of Tc on reaching reducing waters. Slow mixing in the water column of the fjord results in vertical transport of the dissolved Tc to the oxic/anoxic interface. Tc is reduced just below the interface and at 21 m 60% is sorbed to particulate and colloidal material. Tc is carried to the sediments sorbed to the particulate material, where there is a current inventory of approximately 3 Bq m -2 . (LN)

  10. Stratifying patients with peripheral neuropathic pain based on sensory profiles

    DEFF Research Database (Denmark)

    Vollert, Jan; Maier, Christoph; Attal, Nadine

    2017-01-01

    In a recent cluster analysis, it has been shown that patients with peripheral neuropathic pain can be grouped into 3 sensory phenotypes based on quantitative sensory testing profiles, which are mainly characterized by either sensory loss, intact sensory function and mild thermal hyperalgesia and...... populations that need to be screened to reach a subpopulation large enough to conduct a phenotype-stratified study. The most common phenotype in diabetic polyneuropathy was sensory loss (83%), followed by mechanical hyperalgesia (75%) and thermal hyperalgesia (34%, note that percentages are overlapping...

  11. Technetium reduction and removal in a stratified fjord

    Energy Technology Data Exchange (ETDEWEB)

    Keith-Roach, M.; Roos, P. [Risoe National Lab., Roskilde (Denmark)

    2002-04-01

    The distribution of Tc in the water columns of a stratified fjord has been measured to investigate the behaviour and fate of Tc on reaching reducing waters. Slow mixing in the water column of the fjord results in vertical transport of the dissolved Tc to the oxic/anoxic interface. Tc is reduced just below the interface and at 21 m 60% is sorbed to particulate and colloidal material. Tc is carried to the sediments sorbed to the particulate material, where there is a current inventory of approximately 3 Bq m{sup -2}. (LN)

  12. Development of a natural gas stratified charge rotary engine

    Energy Technology Data Exchange (ETDEWEB)

    Sierens, R.; Verdonck, W.

    1985-01-01

    A water model has been used to determine the positions of separate inlet ports for a natural gas, stratified charge rotary engine. The flow inside the combustion chamber (mainly during the induction period) has been registered by a film camera. From these tests the best locations of the inlet ports have been obtained, a prototype of this engine has been built by Audi NSU and tested in the laboratories of the university of Gent. The results of these tests, for different stratification configurations, are given. These results are comparable with the best results obtained by Audi NSU for a homogeneous natural gas rotary engine.

  13. Characterization of forced response of density stratified reacting wake

    Science.gov (United States)

    Pawar, Samadhan A.; Sujith, Raman I.; Emerson, Benjamin; Lieuwen, Tim

    2018-02-01

    The hydrodynamic stability of a reacting wake depends primarily on the density ratio [i.e., ratio of unburnt gas density (ρu) to burnt gas density (ρb)] of the flow across the wake. The variation of the density ratio from high to low value, keeping ρ u / ρ b > 1 , transitions dynamical characteristics of the reacting wake from a linearly globally stable (or convectively unstable) to a globally unstable mode. In this paper, we propose a framework to analyze the effect of harmonic forcing on the deterministic and synchronization characteristics of reacting wakes. Using the recurrence quantification analysis of the forced wake response, we show that the deterministic behaviour of the reacting wake increases as the amplitude of forcing is increased. Furthermore, for different density ratios, we found that the synchronization of the top and bottom branches of the wake with the forcing signal is dependent on whether the mean frequency of the natural oscillations of the wake (fn) is lesser or greater than the frequency of external forcing (ff). We notice that the response of both branches (top and bottom) of the reacting wake to the external forcing is asymmetric and symmetric for the low and high density ratios, respectively. Furthermore, we characterize the phase-locking behaviour between the top and bottom branches of the wake for different values of density ratios. We observe that an increase in the density ratio results in a gradual decrease in the relative phase angle between the top and bottom branches of the wake, which leads to a change in the vortex shedding pattern from a sinuous (anti-phase) to a varicose (in-phase) mode of the oscillations.

  14. Crystallization of a compositionally stratified basal magma ocean

    Science.gov (United States)

    Laneuville, Matthieu; Hernlund, John; Labrosse, Stéphane; Guttenberg, Nicholas

    2018-03-01

    Earth's ∼3.45 billion year old magnetic field is regenerated by dynamo action in its convecting liquid metal outer core. However, convection induces an isentropic thermal gradient which, coupled with a high core thermal conductivity, results in rapid conducted heat loss. In the absence of implausibly high radioactivity or alternate sources of motion to drive the geodynamo, the Earth's early core had to be significantly hotter than the melting point of the lower mantle. While the existence of a dense convecting basal magma ocean (BMO) has been proposed to account for high early core temperatures, the requisite physical and chemical properties for a BMO remain controversial. Here we relax the assumption of a well-mixed convecting BMO and instead consider a BMO that is initially gravitationally stratified owing to processes such as mixing between metals and silicates at high temperatures in the core-mantle boundary region during Earth's accretion. Using coupled models of crystallization and heat transfer through a stratified BMO, we show that very high temperatures could have been trapped inside the early core, sequestering enough heat energy to run an ancient geodynamo on cooling power alone.

  15. Dyadic Green's function of an eccentrically stratified sphere.

    Science.gov (United States)

    Moneda, Angela P; Chrissoulidis, Dimitrios P

    2014-03-01

    The electric dyadic Green's function (dGf) of an eccentrically stratified sphere is built by use of the superposition principle, dyadic algebra, and the addition theorem of vector spherical harmonics. The end result of the analytical formulation is a set of linear equations for the unknown vector wave amplitudes of the dGf. The unknowns are calculated by truncation of the infinite sums and matrix inversion. The theory is exact, as no simplifying assumptions are required in any one of the analytical steps leading to the dGf, and it is general in the sense that any number, position, size, and electrical properties can be considered for the layers of the sphere. The point source can be placed outside of or in any lossless part of the sphere. Energy conservation, reciprocity, and other checks verify that the dGf is correct. A numerical application is made to a stratified sphere made of gold and glass, which operates as a lens.

  16. Crenothrix are major methane consumers in stratified lakes.

    Science.gov (United States)

    Oswald, Kirsten; Graf, Jon S; Littmann, Sten; Tienken, Daniela; Brand, Andreas; Wehrli, Bernhard; Albertsen, Mads; Daims, Holger; Wagner, Michael; Kuypers, Marcel Mm; Schubert, Carsten J; Milucka, Jana

    2017-09-01

    Methane-oxidizing bacteria represent a major biological sink for methane and are thus Earth's natural protection against this potent greenhouse gas. Here we show that in two stratified freshwater lakes a substantial part of upward-diffusing methane was oxidized by filamentous gamma-proteobacteria related to Crenothrix polyspora. These filamentous bacteria have been known as contaminants of drinking water supplies since 1870, but their role in the environmental methane removal has remained unclear. While oxidizing methane, these organisms were assigned an 'unusual' methane monooxygenase (MMO), which was only distantly related to 'classical' MMO of gamma-proteobacterial methanotrophs. We now correct this assignment and show that Crenothrix encode a typical gamma-proteobacterial PmoA. Stable isotope labeling in combination swith single-cell imaging mass spectrometry revealed methane-dependent growth of the lacustrine Crenothrix with oxygen as well as under oxygen-deficient conditions. Crenothrix genomes encoded pathways for the respiration of oxygen as well as for the reduction of nitrate to N 2 O. The observed abundance and planktonic growth of Crenothrix suggest that these methanotrophs can act as a relevant biological sink for methane in stratified lakes and should be considered in the context of environmental removal of methane.

  17. LONGITUDINAL OSCILLATIONS IN DENSITY STRATIFIED AND EXPANDING SOLAR WAVEGUIDES

    Energy Technology Data Exchange (ETDEWEB)

    Luna-Cardozo, M. [Instituto de Astronomia y Fisica del Espacio, CONICET-UBA, CC. 67, Suc. 28, 1428 Buenos Aires (Argentina); Verth, G. [School of Computing, Engineering and Information Sciences, Northumbria University, Newcastle Upon Tyne NE1 8ST (United Kingdom); Erdelyi, R., E-mail: mluna@iafe.uba.ar, E-mail: robertus@sheffield.ac.uk, E-mail: gary.verth@northumbria.ac.uk [Solar Physics and Space Plasma Research Centre (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

    2012-04-01

    Waves and oscillations can provide vital information about the internal structure of waveguides in which they propagate. Here, we analytically investigate the effects of density and magnetic stratification on linear longitudinal magnetohydrodynamic (MHD) waves. The focus of this paper is to study the eigenmodes of these oscillations. It is our specific aim to understand what happens to these MHD waves generated in flux tubes with non-constant (e.g., expanding or magnetic bottle) cross-sectional area and density variations. The governing equation of the longitudinal mode is derived and solved analytically and numerically. In particular, the limit of the thin flux tube approximation is examined. The general solution describing the slow longitudinal MHD waves in an expanding magnetic flux tube with constant density is found. Longitudinal MHD waves in density stratified loops with constant magnetic field are also analyzed. From analytical solutions, the frequency ratio of the first overtone and fundamental mode is investigated in stratified waveguides. For small expansion, a linear dependence between the frequency ratio and the expansion factor is found. From numerical calculations it was found that the frequency ratio strongly depends on the density profile chosen and, in general, the numerical results are in agreement with the analytical results. The relevance of these results for solar magneto-seismology is discussed.

  18. Random forcing of geostrophic motion in rotating stratified turbulence

    Science.gov (United States)

    Waite, Michael L.

    2017-12-01

    Random forcing of geostrophic motion is a common approach in idealized simulations of rotating stratified turbulence. Such forcing represents the injection of energy into large-scale balanced motion, and the resulting breakdown of quasi-geostrophic turbulence into inertia-gravity waves and stratified turbulence can shed light on the turbulent cascade processes of the atmospheric mesoscale. White noise forcing is commonly employed, which excites all frequencies equally, including frequencies much higher than the natural frequencies of large-scale vortices. In this paper, the effects of these high frequencies in the forcing are investigated. Geostrophic motion is randomly forced with red noise over a range of decorrelation time scales τ, from a few time steps to twice the large-scale vortex time scale. It is found that short τ (i.e., nearly white noise) results in about 46% more gravity wave energy than longer τ, despite the fact that waves are not directly forced. We argue that this effect is due to wave-vortex interactions, through which the high frequencies in the forcing are able to excite waves at their natural frequencies. It is concluded that white noise forcing should be avoided, even if it is only applied to the geostrophic motion, when a careful investigation of spontaneous wave generation is needed.

  19. Improvements to TRAC models of condensing stratified flow. Pt. 1

    International Nuclear Information System (INIS)

    Zhang, Q.; Leslie, D.C.

    1991-12-01

    Direct contact condensation in stratified flow is an important phenomenon in LOCA analyses. In this report, the TRAC interfacial heat transfer model for stratified condensing flow has been assessed against the Bankoff experiments. A rectangular channel option has been added to the code to represent the experimental geometry. In almost all cases the TRAC heat transfer coefficient (HTC) over-predicts the condensation rates and in some cases it is so high that the predicted steam is sucked in from the normal outlet in order to conserve mass. Based on their cocurrent and countercurrent condensing flow experiments, Bankoff and his students (Lim 1981, Kim 1985) developed HTC models from the two cases. The replacement of the TRAC HTC with either of Bankoff's models greatly improves the predictions of condensation rates in the experiment with cocurrent condensing flow. However, the Bankoff HTC for countercurrent flow is preferable because it is based only on the local quantities rather than on the quantities averaged from the inlet. (author)

  20. Designing Wood Supply Scenarios from Forest Inventories with Stratified Predictions

    Directory of Open Access Journals (Sweden)

    Philipp Kilham

    2018-02-01

    Full Text Available Forest growth and wood supply projections are increasingly used to estimate the future availability of woody biomass and the correlated effects on forests and climate. This research parameterizes an inventory-based business-as-usual wood supply scenario, with a focus on southwest Germany and the period 2002–2012 with a stratified prediction. First, the Classification and Regression Trees algorithm groups the inventory plots into strata with corresponding harvest probabilities. Second, Random Forest algorithms generate individual harvest probabilities for the plots of each stratum. Third, the plots with the highest individual probabilities are selected as harvested until the harvest probability of the stratum is fulfilled. Fourth, the harvested volume of these plots is predicted with a linear regression model trained on harvested plots only. To illustrate the pros and cons of this method, it is compared to a direct harvested volume prediction with linear regression, and a combination of logistic regression and linear regression. Direct harvested volume regression predicts comparable volume figures, but generates these volumes in a way that differs from business-as-usual. The logistic model achieves higher overall classification accuracies, but results in underestimations or overestimations of harvest shares for several subsets of the data. The stratified prediction method balances this shortcoming, and can be of general use for forest growth and timber supply projections from large-scale forest inventories.

  1. A modified stratified model for the 3C 273 jet

    International Nuclear Information System (INIS)

    Liu Wenpo; Shen Zhiqiang

    2009-01-01

    We present a modified stratified jet model to interpret the observed spectral energy distributions of knots in the 3C 273 jet. Based on the hypothesis of the single index of the particle energy spectrum at injection and identical emission processes among all the knots, the observed difference of spectral shape among different 3C 273 knots can be understood as a manifestation of the deviation of the equivalent Doppler factor of stratified emission regions in an individual knot from a characteristic one. The summed spectral energy distributions of all ten knots in the 3C 273 jet can be well fitted by two components: a low-energy component (radio to optical) dominated by synchrotron radiation and a high-energy component (UV, X-ray and γ-ray) dominated by inverse Compton scattering of the cosmic microwave background. This gives a consistent spectral index of α = 0.88 (S v ∝ v -α ) and a characteristic Doppler factor of 7.4. Assuming the average of the summed spectrum as the characteristic spectrum of each knot in the 3C 273 jet, we further get a distribution of Doppler factors. We discuss the possible implications of these results for the physical properties in the 3C 273 jet. Future GeV observations with GLAST could separate the γ-ray emission of 3C 273 from the large scale jet and the small scale jet (i.e. the core) through measuring the GeV spectrum.

  2. STRESS DISTRIBUTION IN THE STRATIFIED MASS CONTAINING VERTICAL ALVEOLE

    Directory of Open Access Journals (Sweden)

    Bobileva Tatiana Nikolaevna

    2017-08-01

    Full Text Available Almost all subsurface rocks used as foundations for various types of structures are stratified. Such heterogeneity may cause specific behaviour of the materials under strain. Differential equations describing the behaviour of such materials contain rapidly fluctuating coefficients, in view of this, solution of such equations is more time-consuming when using today’s computers. The method of asymptotic averaging leads to getting homogeneous medium under study to averaged equations with fixed factors. The present article is concerned with stratified soil mass consisting of pair-wise alternative isotropic elastic layers. In the results of elastic modules averaging, the present soil mass with horizontal rock stratification is simulated by homogeneous transversal-isotropic half-space with isotropy plane perpendicular to the standing axis. Half-space is loosened by a vertical alveole of circular cross-section, and virgin ground is under its own weight. For horizontal parting planes of layers, the following two types of surface conditions are set: ideal contact and backlash without cleavage. For homogeneous transversal-isotropic half-space received with a vertical alveole, the analytical solution of S.G. Lekhnitsky, well known in scientific papers, is used. The author gives expressions for stress components and displacements in soil mass for different marginal conditions on the alveole surface. Such research problems arise when constructing and maintaining buildings and when composite materials are used.

  3. Measuring mixing efficiency in experiments of strongly stratified turbulence

    Science.gov (United States)

    Augier, P.; Campagne, A.; Valran, T.; Calpe Linares, M.; Mohanan, A. V.; Micard, D.; Viboud, S.; Segalini, A.; Mordant, N.; Sommeria, J.; Lindborg, E.

    2017-12-01

    Oceanic and atmospheric models need better parameterization of the mixing efficiency. Therefore, we need to measure this quantity for flows representative of geophysical flows, both in terms of types of flows (with vortices and/or waves) and of dynamical regimes. In order to reach sufficiently large Reynolds number for strongly stratified flows, experiments for which salt is used to produce the stratification have to be carried out in a large rotating platform of at least 10-meter diameter.We present new experiments done in summer 2017 to study experimentally strongly stratified turbulence and mixing efficiency in the Coriolis platform. The flow is forced by a slow periodic movement of an array of large vertical or horizontal cylinders. The velocity field is measured by 3D-2C scanned horizontal particles image velocimetry (PIV) and 2D vertical PIV. Six density-temperature probes are used to measure vertical and horizontal profiles and signals at fixed positions.We will show how we rely heavily on open-science methods for this study. Our new results on the mixing efficiency will be presented and discussed in terms of mixing parameterization.

  4. The role of the complete Coriolis force in weakly stratified oceanic flows

    Science.gov (United States)

    Tort, M.; Winters, K. B.; Ribstein, B.; Zeitlin, V.

    2016-02-01

    Ocean dynamics is usually described using the primitive equations based on the so-called traditional approximation (TA), where the Coriolis force associated with the horizontal component of the planetary rotation is neglected (also called non-traditional (NT) part proportional to cosΦ, see Fig 1.). However, recent studies have shown that the NT part of the Coriolis force plays a non-negligible dynamical role in some particular oceanic flows (see Gerkema et al., 2008 for an extensive review of NT effects for geophysical and astrophysical flows). Here we explore the relevance of including the NT component of the Coriolis force in ocean models, by presenting particular results regarding two different mid-latitude flow configurations after relaxing the TA: Propagation of wind-induced near-inertial waves (NIWs). Under the TA, NIWs propagate toward the equator, the inertially poleward propagation being internally reflected at a depth-independent critical latitude. The combined effects of the NT Coriolis force and weak stratification in the deep ocean leads to the existence of waveguides for sub-inertial waves, which get trapped and propagate further poleward (Winters et al., 2011). Here we consider storm-induced NIWs and their evolution in a non-linear Boussinesq model on the β-plane in the NT approximation. Preliminary results are presented concerning the behavior of the waves in a weakly stratified mixed-layer, where NT effects are expected to be significant. Inertial instability. A detailed linear stability analysis of the Bickley jet at large Rossby numbers in the NT approximation on the f-plane is performed for long waves in a continuously stratified Boussinesq model. For a sufficiently weak stratification, both symmetric and asymmetric inertial instabilities have substantially higher growth rates than in the TA while no discernible differences between the two approximations are observed for strong enough stratifications (Tort et al., 2015).

  5. Reflection and transmission of electromagnetic waves in planarly stratified media

    International Nuclear Information System (INIS)

    Caviglia, G.

    1999-01-01

    Propagation of time-harmonic electromagnetic waves in planarly stratified multilayers is investigated. Each layer is allowed to be inhomogeneous and the layers are separated by interfaces. The procedure is based on the representation of the electromagnetic field in the basis of the eigenvectors of the matrix characterizing the first-order system. Hence the local reflection and transmission matrices are defined and the corresponding differential equations, in the pertinent space variable are determined. The jump conditions at interfaces are also established. The present model incorporates dissipative materials and the procedure holds without any restrictions to material symmetries. Differential equations appeared in the literature are shown to hold in particular (one-dimensional) cases or to represent homogeneous layers only

  6. Microstructure of Turbulence in the Stably Stratified Boundary Layer

    Science.gov (United States)

    Sorbjan, Zbigniew; Balsley, Ben B.

    2008-11-01

    The microstructure of a stably stratified boundary layer, with a significant low-level nocturnal jet, is investigated based on observations from the CASES-99 campaign in Kansas, U.S.A. The reported, high-resolution vertical profiles of the temperature, wind speed, wind direction, pressure, and the turbulent dissipation rate, were collected under nocturnal conditions on October 14, 1999, using the CIRES Tethered Lifting System. Two methods for evaluating instantaneous (1-sec) background profiles are applied to the raw data. The background potential temperature is calculated using the “bubble sort” algorithm to produce a monotonically increasing potential temperature with increasing height. Other scalar quantities are smoothed using a running vertical average. The behaviour of background flow, buoyant overturns, turbulent fluctuations, and their respective histograms are presented. Ratios of the considered length scales and the Ozmidov scale are nearly constant with height, a fact that can be applied in practice for estimating instantaneous profiles of the dissipation rate.

  7. Hydrodynamics of stratified epithelium: Steady state and linearized dynamics

    Science.gov (United States)

    Yeh, Wei-Ting; Chen, Hsuan-Yi

    2016-05-01

    A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.

  8. A study of stratified gas-liquid pipe flow

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, George W.

    2005-07-01

    This work includes both theoretical modelling and experimental observations which are relevant to the design of gas condensate transport lines. Multicomponent hydrocarbon gas mixtures are transported in pipes over long distances and at various inclinations. Under certain circumstances, the heavier hydrocarbon components and/or water vapour condense to form one or more liquid phases. Near the desired capacity, the liquid condensate and water is efficiently transported in the form of a stratified flow with a droplet field. During operating conditions however, the flow rate may be reduced allowing liquid accumulation which can create serious operational problems due to large amounts of excess liquid being expelled into the receiving facilities during production ramp-up or even in steady production in severe cases. In particular, liquid tends to accumulate in upward inclined sections due to insufficient drag on the liquid from the gas. To optimize the transport of gas condensates, a pipe diameters should be carefully chosen to account for varying flow rates and pressure levels which are determined through the knowledge of the multiphase flow present. It is desirable to have a reliable numerical simulation tool to predict liquid accumulation for various flow rates, pipe diameters and pressure levels which is not presently accounted for by industrial flow codes. A critical feature of the simulation code would include the ability to predict the transition from small liquid accumulation at high flow rates to large liquid accumulation at low flow rates. A semi-intermittent flow regime of roll waves alternating with a partly backward flowing liquid film has been observed experimentally to occur for a range of gas flow rates. Most of the liquid is transported in the roll waves. The roll wave regime is not well understood and requires fundamental modelling and experimental research. The lack of reliable models for this regime leads to inaccurate prediction of the onset of

  9. The Risk-Stratified Osteoporosis Strategy Evaluation study (ROSE)

    DEFF Research Database (Denmark)

    Rubin, Katrine Hass; Holmberg, Teresa; Rothmann, Mette Juel

    2015-01-01

    The risk-stratified osteoporosis strategy evaluation study (ROSE) is a randomized prospective population-based study investigating the effectiveness of a two-step screening program for osteoporosis in women. This paper reports the study design and baseline characteristics of the study population....... 35,000 women aged 65-80 years were selected at random from the population in the Region of Southern Denmark and-before inclusion-randomized to either a screening group or a control group. As first step, a self-administered questionnaire regarding risk factors for osteoporosis based on FRAX......(®) was issued to both groups. As second step, subjects in the screening group with a 10-year probability of major osteoporotic fractures ≥15 % were offered a DXA scan. Patients diagnosed with osteoporosis from the DXA scan were advised to see their GP and discuss pharmaceutical treatment according to Danish...

  10. Temporally stratified sampling programs for estimation of fish impingement

    International Nuclear Information System (INIS)

    Kumar, K.D.; Griffith, J.S.

    1977-01-01

    Impingement monitoring programs often expend valuable and limited resources and fail to provide a dependable estimate of either total annual impingement or those biological and physicochemical factors affecting impingement. In situations where initial monitoring has identified ''problem'' fish species and the periodicity of their impingement, intensive sampling during periods of high impingement will maximize information obtained. We use data gathered at two nuclear generating facilities in the southeastern United States to discuss techniques of designing such temporally stratified monitoring programs and their benefits and drawbacks. Of the possible temporal patterns in environmental factors within a calendar year, differences among seasons are most influential in the impingement of freshwater fishes in the Southeast. Data on the threadfin shad (Dorosoma petenense) and the role of seasonal temperature changes are utilized as an example to demonstrate ways of most efficiently and accurately estimating impingement of the species

  11. Direct numerical simulation of homogeneous stratified rotating turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Iida, O.; Tsujimura, S.; Nagano, Y. [Nagoya Institute of Technology, Department of Mech. Eng., Nagoya (Japan)

    2005-12-01

    The effects of the Prandtl number on stratified rotating turbulence have been studied in homogeneous turbulence by using direct numerical simulations and a rapid distortion theory. Fluctuations under strong stable-density stratification can be theoretically divided into the WAVE and the potential vorticity (PV) modes. In low-Prandtl-number fluids, the WAVE mode deteriorates, while the PV mode remains. Imposing rotation on a low-Prandtl-number fluid makes turbulence two-dimensional as well as geostrophic; it is found from the instantaneous turbulent structure that the vortices merge to form a few vertically-elongated vortex columns. During the period toward two-dimensionalization, the vertical vortices become asymmetric in the sense of rotation. (orig.)

  12. Advanced stratified charge rotary aircraft engine design study

    Science.gov (United States)

    Badgley, P.; Berkowitz, M.; Jones, C.; Myers, D.; Norwood, E.; Pratt, W. B.; Ellis, D. R.; Huggins, G.; Mueller, A.; Hembrey, J. H.

    1982-01-01

    A technology base of new developments which offered potential benefits to a general aviation engine was compiled and ranked. Using design approaches selected from the ranked list, conceptual design studies were performed of an advanced and a highly advanced engine sized to provide 186/250 shaft Kw/HP under cruise conditions at 7620/25,000 m/ft altitude. These are turbocharged, direct-injected stratified charge engines intended for commercial introduction in the early 1990's. The engine descriptive data includes tables, curves, and drawings depicting configuration, performance, weights and sizes, heat rejection, ignition and fuel injection system descriptions, maintenance requirements, and scaling data for varying power. An engine-airframe integration study of the resulting engines in advanced airframes was performed on a comparative basis with current production type engines. The results show airplane performance, costs, noise & installation factors. The rotary-engined airplanes display substantial improvements over the baseline, including 30 to 35% lower fuel usage.

  13. Prototypic Features of Loneliness in a Stratified Sample of Adolescents

    Directory of Open Access Journals (Sweden)

    Mathias Lasgaard

    2009-06-01

    Full Text Available Dominant theoretical approaches in loneliness research emphasize the value of personality characteristics in explaining loneliness. The present study examines whether dysfunctional social strategies and attributions in lonely adolescents can be explained by personality characteristics. A questionnaire survey was conducted with 379 Danish Grade 8 students (M = 14.1 years, SD = 0.4 from 22 geographically stratified and randomly selected schools. Hierarchical linear regression analysis showed that network orientation, success expectation and avoidance in affiliative situations predicted loneliness independent of personality characteristics, demographics and social desirability. The study indicates that dysfunctional strategies and attributions in affiliative situations are directly related to loneliness in adolescence. These strategies and attributions may preclude lonely adolescents from guidance and intervention. Thus, professionals need to be knowledgeable about prototypic features of loneliness in addition to employing a pro-active approach when assisting adolescents who display prototypic features.

  14. The optimism trap: Migrants' educational choices in stratified education systems.

    Science.gov (United States)

    Tjaden, Jasper Dag; Hunkler, Christian

    2017-09-01

    Immigrant children's ambitious educational choices have often been linked to their families' high level of optimism and motivation for upward mobility. However, previous research has mostly neglected alternative explanations such as information asymmetries or anticipated discrimination. Moreover, immigrant children's higher dropout rates at the higher secondary and university level suggest that low performing migrant students could have benefitted more from pursuing less ambitious tracks, especially in countries that offer viable vocational alternatives. We examine ethnic minority's educational choices using a sample of academically low performing, lower secondary school students in Germany's highly stratified education system. We find that their families' optimism diverts migrant students from viable vocational alternatives. Information asymmetries and anticipated discrimination do not explain their high educational ambitions. While our findings further support the immigrant optimism hypothesis, we discuss how its effect may have different implications depending on the education system. Copyright © 2017. Published by Elsevier Inc.

  15. Internal combustion engine using premixed combustion of stratified charges

    Science.gov (United States)

    Marriott, Craig D [Rochester Hills, MI; Reitz, Rolf D [Madison, WI

    2003-12-30

    During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

  16. Visualization periodic flows in a continuously stratified fluid.

    Science.gov (United States)

    Bardakov, R.; Vasiliev, A.

    2012-04-01

    To visualize the flow pattern of viscous continuously stratified fluid both experimental and computational methods were developed. Computational procedures were based on exact solutions of set of the fundamental equations. Solutions of the problems of flows producing by periodically oscillating disk (linear and torsion oscillations) were visualized with a high resolutions to distinguish small-scale the singular components on the background of strong internal waves. Numerical algorithm of visualization allows to represent both the scalar and vector fields, such as velocity, density, pressure, vorticity, stream function. The size of the source, buoyancy and oscillation frequency, kinematic viscosity of the medium effects were traced in 2D an 3D posing problems. Precision schlieren instrument was used to visualize the flow pattern produced by linear and torsion oscillations of strip and disk in a continuously stratified fluid. Uniform stratification was created by the continuous displacement method. The buoyancy period ranged from 7.5 to 14 s. In the experiments disks with diameters from 9 to 30 cm and a thickness of 1 mm to 10 mm were used. Different schlieren methods that are conventional vertical slit - Foucault knife, vertical slit - filament (Maksoutov's method) and horizontal slit - horizontal grating (natural "rainbow" schlieren method) help to produce supplementing flow patterns. Both internal wave beams and fine flow components were visualized in vicinity and far from the source. Intensity of high gradient envelopes increased proportionally the amplitude of the source. In domains of envelopes convergence isolated small scale vortices and extended mushroom like jets were formed. Experiments have shown that in the case of torsion oscillations pattern of currents is more complicated than in case of forced linear oscillations. Comparison with known theoretical model shows that nonlinear interactions between the regular and singular flow components must be taken

  17. Investigations on flow reversal in stratified horizontal flow

    International Nuclear Information System (INIS)

    Staebler, T.; Meyer, L.; Schulenberg, T.; Laurien, E.

    2005-01-01

    The phenomena of flow reversal in stratified flows are investigated in a horizontal channel with application to the Emergency Core Cooling System (ECCS) in Pressurized Water Reactors (PWR). In case of a Loss-of-Coolant-Accident (LOCA), coolant can be injected through a secondary pipe within the feeding line of the primary circuit, the so called hot leg, counter-currently to the steam flow. It is essential that the coolant reaches the reactor core to prevent overheating. Due to high temperatures in such accident scenarios, steam is generated in the core, which escapes from the reactor vessel through the hot leg. In case of sufficiently high steam flow rates, only a reduced amount of coolant or even no coolant will be delivered to the reactor core. The WENKA test facility at the Institute for Nuclear and Energy Technologies (IKET) at Forschungszentrum Karlsruhe is capable to investigate the fluid dynamics of two-phase flows in such scenarios. Water and air flow counter-currently in a horizontal channel made of clear acrylic glass to allow full optical access. Flow rates of water and air can be varied independently within a wide range. Once flow reversal sets in, a strong hysteresis effect must be taken into account. This was quantified during the present investigations. Local experimental data are needed to expand appropriate models on flow reversal in horizontal two-phase flow and to include them into numerical codes. Investigations are carried out by means of Particle Image Velocimetry (PIV) to obtain local flow velocities without disturbing the flow. Due to the wavy character of the flow, strong reflections at the interfacial area must be taken into account. Using fluorescent particles and an optical filter allows eliminating the reflections and recording only the signals of the particles. The challenges in conducting local investigations in stratified wavy flows by applying optical measurement techniques are discussed. Results are presented and discussed allowing

  18. Stratified flow model for convective condensation in an inclined tube

    International Nuclear Information System (INIS)

    Lips, Stéphane; Meyer, Josua P.

    2012-01-01

    Highlights: ► Convective condensation in an inclined tube is modelled. ► The heat transfer coefficient is the highest for about 20° below the horizontal. ► Capillary forces have a strong effect on the liquid–vapour interface shape. ► A good agreement between the model and the experimental results was observed. - Abstract: Experimental data are reported for condensation of R134a in an 8.38 mm inner diameter smooth tube in inclined orientations with a mass flux of 200 kg/m 2 s. Under these conditions, the flow is stratified and there is an optimum inclination angle, which leads to the highest heat transfer coefficient. There is a need for a model to better understand and predict the flow behaviour. In this paper, the state of the art of existing models of stratified two-phase flows in inclined tubes is presented, whereafter a new mechanistic model is proposed. The liquid–vapour distribution in the tube is determined by taking into account the gravitational and the capillary forces. The comparison between the experimental data and the model prediction showed a good agreement in terms of heat transfer coefficients and pressure drops. The effect of the interface curvature on the heat transfer coefficient has been quantified and has been found to be significant. The optimum inclination angle is due to a balance between an increase of the void fraction and an increase in the falling liquid film thickness when the tube is inclined downwards. The effect of the mass flux and the vapour quality on the optimum inclination angle has also been studied.

  19. Mean-field theory of differential rotation in density stratified turbulent convection

    Science.gov (United States)

    Rogachevskii, I.

    2018-04-01

    A mean-field theory of differential rotation in a density stratified turbulent convection has been developed. This theory is based on the combined effects of the turbulent heat flux and anisotropy of turbulent convection on the Reynolds stress. A coupled system of dynamical budget equations consisting in the equations for the Reynolds stress, the entropy fluctuations and the turbulent heat flux has been solved. To close the system of these equations, the spectral approach, which is valid for large Reynolds and Péclet numbers, has been applied. The adopted model of the background turbulent convection takes into account an increase of the turbulence anisotropy and a decrease of the turbulent correlation time with the rotation rate. This theory yields the radial profile of the differential rotation which is in agreement with that for the solar differential rotation.

  20. Turbulent entrainment across turbulent-nonturbulent interfaces in stably stratified mixing layers

    Science.gov (United States)

    Watanabe, T.; Riley, J. J.; Nagata, K.

    2017-10-01

    The entrainment process in stably stratified mixing layers is studied in relation to the turbulent-nonturbulent interface (TNTI) using direct numerical simulations. The statistics are calculated with the interface coordinate in an Eulerian frame as well as with the Lagrangian fluid particles entrained from the nonturbulent to the turbulent regions. The characteristics of entrainment change as the buoyancy Reynolds number Reb decreases and the flow begins to layer. The baroclinic torque delays the enstrophy growth of the entrained fluids at small Reb, while this effect is less efficient for large Reb. The entrained particle movement within the TNTI layer is dominated by the small dissipative scales, and the rapid decay of the kinetic energy dissipation rate due to buoyancy causes the entrained particle movement relative to the interface location to become slower. Although the Eulerian statistics confirm that there exists turbulent fluid with strong vorticity or with large buoyancy frequency near the TNTI, the entrained fluid particles circumvent these regions by passing through the TNTI in strain-dominant regions or in regions with small buoyancy frequency. The multiparticle statistics show that once the nonturbulent fluid volumes are entrained, they are deformed into flattened shapes in the vertical direction and diffuse in the horizontal direction. When Reb is large enough for small-scale turbulence to exist, the entrained fluid is able to penetrate into the turbulent core region. Once the flow begins to layer with decreasing Reb, however, the entrained fluid volume remains near the outer edge of the turbulent region and forms a stably stratified layer without vertical overturning.

  1. Dynamic Transitions and Baroclinic Instability for 3D Continuously Stratified Boussinesq Flows

    Science.gov (United States)

    Şengül, Taylan; Wang, Shouhong

    2018-02-01

    The main objective of this article is to study the nonlinear stability and dynamic transitions of the basic (zonal) shear flows for the three-dimensional continuously stratified rotating Boussinesq model. The model equations are fundamental equations in geophysical fluid dynamics, and dynamics associated with their basic zonal shear flows play a crucial role in understanding many important geophysical fluid dynamical processes, such as the meridional overturning oceanic circulation and the geophysical baroclinic instability. In this paper, first we derive a threshold for the energy stability of the basic shear flow, and obtain a criterion for local nonlinear stability in terms of the critical horizontal wavenumbers and the system parameters such as the Froude number, the Rossby number, the Prandtl number and the strength of the shear flow. Next, we demonstrate that the system always undergoes a dynamic transition from the basic shear flow to either a spatiotemporal oscillatory pattern or circle of steady states, as the shear strength of the basic flow crosses a critical threshold. Also, we show that the dynamic transition can be either continuous or catastrophic, and is dictated by the sign of a transition number, fully characterizing the nonlinear interactions of different modes. Both the critical shear strength and the transition number are functions of the system parameters. A systematic numerical method is carried out to explore transition in different flow parameter regimes. In particular, our numerical investigations show the existence of a hypersurface which separates the parameter space into regions where the basic shear flow is stable and unstable. Numerical investigations also yield that the selection of horizontal wave indices is determined only by the aspect ratio of the box. We find that the system admits only critical eigenmodes with roll patterns aligned with the x-axis. Furthermore, numerically we encountered continuous transitions to multiple

  2. Decreasing Relative Risk Premium

    DEFF Research Database (Denmark)

    Hansen, Frank

    relative risk premium in the small implies decreasing relative risk premium in the large, and decreasing relative risk premium everywhere implies risk aversion. We finally show that preferences with decreasing relative risk premium may be equivalently expressed in terms of certain preferences on risky......We consider the risk premium demanded by a decision maker with wealth x in order to be indifferent between obtaining a new level of wealth y1 with certainty, or to participate in a lottery which either results in unchanged present wealth or a level of wealth y2 > y1. We define the relative risk...... premium as the quotient between the risk premium and the increase in wealth y1–x which the decision maker puts on the line by choosing the lottery in place of receiving y1 with certainty. We study preferences such that the relative risk premium is a decreasing function of present wealth, and we determine...

  3. Immediate release niacin effect at stratified lipid levels

    Directory of Open Access Journals (Sweden)

    Elise Vo

    2015-12-01

    If initial LDL-C was  =130, LDL-C decreased 35% in MTG vs. 32% decrease in CTG. If initial HDL-C  150, there was a 48% decrease in MTG vs. 54% decrease in CTG. Lpa decreased 49% for all patients with initially elevated Lpa. Data except for LDL-C  130, but not significantly when LDL-C < 130. Patients in AIM-HIGH and HPS-2-THIRVE received statin therapy causing very low initial LDL-C. Our results may explain why adding niacin to statin therapy failed in AIM-HIGH and HPS-2-THRIVE since niacin did not further lower LDL-C.

  4. Decreasing Serial Cost Sharing

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Østerdal, Lars Peter

    The increasing serial cost sharing rule of Moulin and Shenker [Econometrica 60 (1992) 1009] and the decreasing serial rule of de Frutos [Journal of Economic Theory 79 (1998) 245] have attracted attention due to their intuitive appeal and striking incentive properties. An axiomatic characterization...... of the increasing serial rule was provided by Moulin and Shenker [Journal of Economic Theory 64 (1994) 178]. This paper gives an axiomatic characterization of the decreasing serial rule...

  5. Decreasing serial cost sharing

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Østerdal, Lars Peter Raahave

    2009-01-01

    The increasing serial cost sharing rule of Moulin and Shenker (Econometrica 60:1009-1037, 1992) and the decreasing serial rule of de Frutos (J Econ Theory 79:245-275, 1998) are known by their intuitive appeal and striking incentive properties. An axiomatic characterization of the increasing serial...... rule was provided by Moulin and Shenker (J Econ Theory 64:178-201, 1994). This paper gives an axiomatic characterization of the decreasing serial rule....

  6. Cable Stability

    Energy Technology Data Exchange (ETDEWEB)

    Bottura, L [European Organization for Nuclear Research, Geneva (Switzerland)

    2014-07-01

    Superconductor stability is at the core of the design of any successful cable and magnet application. This chapter reviews the initial understanding of the stability mechanism, and reviews matters of importance for stability such as the nature and magnitude of the perturbation spectrum and the cooling mechanisms. Various stability strategies are studied, providing criteria that depend on the desired design and operating conditions.

  7. Stratified flows with variable density: mathematical modelling and numerical challenges.

    Science.gov (United States)

    Murillo, Javier; Navas-Montilla, Adrian

    2017-04-01

    Stratified flows appear in a wide variety of fundamental problems in hydrological and geophysical sciences. They may involve from hyperconcentrated floods carrying sediment causing collapse, landslides and debris flows, to suspended material in turbidity currents where turbulence is a key process. Also, in stratified flows variable horizontal density is present. Depending on the case, density varies according to the volumetric concentration of different components or species that can represent transported or suspended materials or soluble substances. Multilayer approaches based on the shallow water equations provide suitable models but are not free from difficulties when moving to the numerical resolution of the governing equations. Considering the variety of temporal and spatial scales, transfer of mass and energy among layers may strongly differ from one case to another. As a consequence, in order to provide accurate solutions, very high order methods of proved quality are demanded. Under these complex scenarios it is necessary to observe that the numerical solution provides the expected order of accuracy but also converges to the physically based solution, which is not an easy task. To this purpose, this work will focus in the use of Energy balanced augmented solvers, in particular, the Augmented Roe Flux ADER scheme. References: J. Murillo , P. García-Navarro, Wave Riemann description of friction terms in unsteady shallow flows: Application to water and mud/debris floods. J. Comput. Phys. 231 (2012) 1963-2001. J. Murillo B. Latorre, P. García-Navarro. A Riemann solver for unsteady computation of 2D shallow flows with variable density. J. Comput. Phys.231 (2012) 4775-4807. A. Navas-Montilla, J. Murillo, Energy balanced numerical schemes with very high order. The Augmented Roe Flux ADER scheme. Application to the shallow water equations, J. Comput. Phys. 290 (2015) 188-218. A. Navas-Montilla, J. Murillo, Asymptotically and exactly energy balanced augmented flux

  8. Deep silicon maxima in the stratified oligotrophic Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Y. Crombet

    2011-02-01

    Full Text Available The silicon biogeochemical cycle has been studied in the Mediterranean Sea during late summer/early autumn 1999 and summer 2008. The distribution of nutrients, particulate carbon and silicon, fucoxanthin (Fuco, and total chlorophyll-a (TChl-a were investigated along an eastward gradient of oligotrophy during two cruises (PROSOPE and BOUM encompassing the entire Mediterranean Sea during the stratified period. At both seasons, surface waters were depleted in nutrients and the nutriclines gradually deepened towards the East, the phosphacline being the deepest in the easternmost Levantine basin. Following the nutriclines, parallel deep maxima of biogenic silica (DSM, fucoxanthin (DFM and TChl-a (DCM were evidenced during both seasons with maximal concentrations of 0.45 μmol L−1 for BSi, 0.26 μg L−1 for Fuco, and 1.70 μg L−1 for TChl-a, all measured during summer. Contrary to the DCM which was a persistent feature in the Mediterranean Sea, the DSM and DFMs were observed in discrete areas of the Alboran Sea, the Algero-Provencal basin, the Ionian sea and the Levantine basin, indicating that diatoms were able to grow at depth and dominate the DCM under specific conditions. Diatom assemblages were dominated by Chaetoceros spp., Leptocylindrus spp., Pseudonitzschia spp. and the association between large centric diatoms (Hemiaulus hauckii and Rhizosolenia styliformis and the cyanobacterium Richelia intracellularis was observed at nearly all sites. The diatom's ability to grow at depth is commonly observed in other oligotrophic regions and could play a major role in ecosystem productivity and carbon export to depth. Contrary to the common view that Si and siliceous phytoplankton are not major components of the Mediterranean biogeochemistry, we suggest here that diatoms, by persisting at depth during the stratified period, could contribute to a

  9. Experimental CFD grade data for stratified two-phase flows

    Energy Technology Data Exchange (ETDEWEB)

    Vallee, Christophe, E-mail: c.vallee@fzd.d [Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, D-01314 Dresden (Germany); Lucas, Dirk; Beyer, Matthias; Pietruske, Heiko; Schuetz, Peter; Carl, Helmar [Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, D-01314 Dresden (Germany)

    2010-09-15

    Stratified two-phase flows were investigated at two test facilities with horizontal test-sections. For both, rectangular channel cross-sections were chosen to provide optimal observation possibilities for the application of optical measurement techniques. In order to show the local flow structure, high-speed video observation was applied, which delivers the high-resolution in space and time needed for CFD code validation. The first investigations were performed in the Horizontal Air/Water Channel (HAWAC), which is made of acrylic glass and allows the investigation of air/water co-current flows at atmospheric pressure and room temperature. At the channel inlet, a special device was designed for well-defined and adjustable inlet boundary conditions. For the quantitative analysis of the optical measurements performed at the HAWAC, an algorithm was developed to recognise the stratified interface in the camera frames. This allows to make statistical treatments for comparison with CFD calculation results. As an example, the unstable wave growth leading to slug flow is shown from the test-section inlet. Moreover, the hydraulic jump as the quasi-stationary discontinuous transition between super- and subcritical flow was investigated in this closed channel. The structure of the hydraulic jump over time is revealed by the calculation of the probability density of the water level. A series of experiments show that the hydraulic jump profile and its position from the inlet vary substantially with the inlet boundary conditions due to the momentum exchange between the phases. The second channel is built in the pressure chamber of the TOPFLOW test facility, which is used to perform air/water and steam/water experiments at pressures of up to 5.0 MPa and temperatures of up to 264 {sup o}C, but under pressure equilibrium with the vessel inside. In the present experiment, the test-section represents a flat model of the hot leg of the German Konvoi pressurised water reactor scaled at

  10. Experimental CFD grade data for stratified two-phase flows

    International Nuclear Information System (INIS)

    Vallee, Christophe; Lucas, Dirk; Beyer, Matthias; Pietruske, Heiko; Schuetz, Peter; Carl, Helmar

    2010-01-01

    Stratified two-phase flows were investigated at two test facilities with horizontal test-sections. For both, rectangular channel cross-sections were chosen to provide optimal observation possibilities for the application of optical measurement techniques. In order to show the local flow structure, high-speed video observation was applied, which delivers the high-resolution in space and time needed for CFD code validation. The first investigations were performed in the Horizontal Air/Water Channel (HAWAC), which is made of acrylic glass and allows the investigation of air/water co-current flows at atmospheric pressure and room temperature. At the channel inlet, a special device was designed for well-defined and adjustable inlet boundary conditions. For the quantitative analysis of the optical measurements performed at the HAWAC, an algorithm was developed to recognise the stratified interface in the camera frames. This allows to make statistical treatments for comparison with CFD calculation results. As an example, the unstable wave growth leading to slug flow is shown from the test-section inlet. Moreover, the hydraulic jump as the quasi-stationary discontinuous transition between super- and subcritical flow was investigated in this closed channel. The structure of the hydraulic jump over time is revealed by the calculation of the probability density of the water level. A series of experiments show that the hydraulic jump profile and its position from the inlet vary substantially with the inlet boundary conditions due to the momentum exchange between the phases. The second channel is built in the pressure chamber of the TOPFLOW test facility, which is used to perform air/water and steam/water experiments at pressures of up to 5.0 MPa and temperatures of up to 264 o C, but under pressure equilibrium with the vessel inside. In the present experiment, the test-section represents a flat model of the hot leg of the German Konvoi pressurised water reactor scaled at 1

  11. Why turbulence sustains in supercritically stratified free atmosphere?

    Science.gov (United States)

    Zilitinkevich, Sergej

    2016-04-01

    It is widely believed that in very stable stratifications, at Richardson numbers (Ri) exceeding critical value Ric ˜ 0.25 turbulence decays and flow becomes laminar. This is so at low Reynolds numbers (Re), e.g., in lab experiments; but this is not true in very-high-Re geophysical flows. Free atmosphere and deep ocean are turbulent in spite of strongly supercritical stratifications: 1 role of negative buoyancy flux, Fb > 0, in turbulence energetics was treated in terms of the turbulent kinetic energy (TKE) budget equation and understood as just consumption of TKE by the buoyancy forces. This has led to the conclusion that sufficiently strong static stability causes the negative buoyancy flux sufficiently strong to exceed the TKE generation rate and thus to kill turbulence. However, considering TKE equation together with budget equation for turbulent potential energy (TPE proportional to the squared buoyancy fluctuations) shows that the role of Fb in turbulence energetics is nothing but conversion of TKE into TPE (Fb just quantifies the rate of this conversion); so that Fb does not affect total turbulent energy (TTE = TKE + TPE). Moreover, as follows from the buoyancy-flux budget equation, TPE generates positive (directed upward) buoyancy flux irrespective of the sign of the buoyancy gradient. Indeed, the warmer fluid particles (with positive buoyancy fluctuation) rise up, whereas the cooler particles sink down, so that both contribute to the positive buoyancy flux opposing to the usual, negative flux generated by mean buoyancy gradient. In this context, strengthening the negative buoyancy flux leads to decreasing TKE and increasing TPE. The latter enhances the counter-gradient share of the total flux, thus reduces |Fb| and, eventually, increases TKE. The above negative feedback was disregarded in the conventional concept of down-gradient turbulent transport. This mechanism imposes a limit on the maximal (independent of the buoyancy gradient) value of |Fb| and thus

  12. Control of locomotor stability in stabilizing and destabilizing environments.

    Science.gov (United States)

    Wu, Mengnan/Mary; Brown, Geoffrey; Gordon, Keith E

    2017-06-01

    To develop effective interventions targeting locomotor stability, it is crucial to understand how people control and modify gait in response to changes in stabilization requirements. Our purpose was to examine how individuals with and without incomplete spinal cord injury (iSCI) control lateral stability in haptic walking environments that increase or decrease stabilization demands. We hypothesized that people would adapt to walking in a predictable, stabilizing viscous force field and unpredictable destabilizing force field by increasing and decreasing feedforward control of lateral stability, respectively. Adaptations in feedforward control were measured using after-effects when fields were removed. Both groups significantly (pfeedforward adaptions to increase control of lateral stability. In contrast, in the destabilizing field, non-impaired subjects increased movement variability (p0.05). When the destabilizing field was removed, increases in movement variability persisted (pfeedforward decreases in resistance to perturbations. Published by Elsevier B.V.

  13. Plume Splitting in a Two-layer Stratified Ambient Fluid

    Science.gov (United States)

    Ma, Yongxing; Flynn, Morris; Sutherland, Bruce

    2017-11-01

    A line-source plume descending into a two-layer stratified ambient fluid in a finite sized tank is studied experimentally. Although the total volume of ambient fluid is fixed, lower- and upper-layer fluids are respectively removed and added at a constant rate mimicking marine outfall through diffusers and natural and hybrid ventilated buildings. The influence of the plume on the ambient depends on the value of λ, defined as the ratio of the plume buoyancy to the buoyancy loss of the plume as it crosses the ambient interface. Similar to classical filling-box experiments, the plume can always reach the bottom of the tank if λ > 1 . By contrast, if λ < 1 , an intermediate layer eventually forms as a result of plume splitting. Eventually all of the plume fluid spreads within the intermediate layer. The starting time, tv, and the ending time, tt, of the transition process measured from experiments correlate with the value of λ. A three-layer ambient fluid is observed after transition, and the mean value of the measured densities of the intermediate layer fluid is well predicted using plume theory. Acknowledgments: Funding for this study was provided by NSERC.

  14. Economic evaluation in stratified medicine: methodological issues and challenges

    Directory of Open Access Journals (Sweden)

    Hans-Joerg eFugel

    2016-05-01

    Full Text Available Background: Stratified Medicine (SM is becoming a practical reality with the targeting of medicines by using a biomarker or genetic-based diagnostic to identify the eligible patient sub-population. Like any healthcare intervention, SM interventions have costs and consequences that must be considered by reimbursement authorities with limited resources. Methodological standards and guidelines exist for economic evaluations in clinical pharmacology and are an important component for health technology assessments (HTAs in many countries. However, these guidelines have initially been developed for traditional pharmaceuticals and not for complex interventions with multiple components. This raises the issue as to whether these guidelines are adequate to SM interventions or whether new specific guidance and methodology is needed to avoid inconsistencies and contradictory findings when assessing economic value in SM.Objective: This article describes specific methodological challenges when conducting health economic (HE evaluations for SM interventions and outlines potential modifications necessary to existing evaluation guidelines /principles that would promote consistent economic evaluations for SM.Results/Conclusions: Specific methodological aspects for SM comprise considerations on the choice of comparator, measuring effectiveness and outcomes, appropriate modelling structure and the scope of sensitivity analyses. Although current HE methodology can be applied for SM, greater complexity requires further methodology development and modifications in the guidelines.

  15. Operations and Maintenance Cost for Stratified Buildings: A Critical Review

    Directory of Open Access Journals (Sweden)

    Che-Ghani Nor Zaimah

    2016-01-01

    Full Text Available Building maintenance is essential in preserving buildings’ appearance and performance. It needs to upkeep the building performance to prolong its value and building life cycle. Malaysia is still lacking in managing cost for building operation and maintenance. It has been found that the cost for housing maintenance is high due to poor maintenance practices. In order to get better understanding on how to manage the cost, this study reviews the contributing factors that affecting operation and maintenance cost of stratified buildings in Malaysia. The research first identified the factors through extensive literature review and scrutinize on factors that affecting and can minimize operation and maintenance cost. This literature review offers insight into building maintenance scenario in Malaysia focusing on the issues and challenges. The study also finds that operation and maintenance cost for housing in Malaysia is still in poor state. Interestingly, this paper revealed that operation and maintenance cost is also influenced by three significant factors like expectation of tenants, building characteristics and building defects. Measures to reduce the housing operation and maintenance cost are also highlighted so that this study can be a stepping stone towards proposing efficient and effective facilities management strategies for affordable housing in future.

  16. Clinical research in small genomically stratified patient populations.

    Science.gov (United States)

    Martin-Liberal, J; Rodon, J

    2017-07-01

    The paradigm of early drug development in cancer is shifting from 'histology-oriented' to 'molecularly oriented' clinical trials. This change can be attributed to the vast amount of tumour biology knowledge generated by large international research initiatives such as The Cancer Genome Atlas (TCGA) and the use of next generation sequencing (NGS) techniques developed in recent years. However, targeting infrequent molecular alterations entails a series of special challenges. The optimal molecular profiling method, the lack of standardised biological thresholds, inter- and intra-tumor heterogeneity, availability of enough tumour material, correct clinical trials design, attrition rate, logistics or costs are only some of the issues that need to be taken into consideration in clinical research in small genomically stratified patient populations. This article examines the most relevant challenges inherent to clinical research in these populations. Moreover, perspectives from the Academia point of view are reviewed as well as initiatives to be taken in forthcoming years. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Stratifying the Risk of Venous Thromboembolism in Otolaryngology

    Science.gov (United States)

    Shuman, Andrew G.; Hu, Hsou Mei; Pannucci, Christopher J.; Jackson, Christopher R.; Bradford, Carol R.; Bahl, Vinita

    2015-01-01

    Objective The consequences of perioperative venous thromboembolism (VTE) are devastating; identifying patients at risk is an essential step in reducing morbidity and mortality. The utility of perioperative VTE risk assessment in otolaryngology is unknown. This study was designed to risk-stratify a diverse population of otolaryngology patients for VTE events. Study Design Retrospective cohort study. Setting Single-institution academic tertiary care medical center. Subjects and Methods Adult patients presenting for otolaryngologic surgery requiring hospital admission from 2003 to 2010 who did not receive VTE chemoprophylaxis were included. The Caprini risk assessment was retrospectively scored via a validated method of electronic chart abstraction. Primary study variables were Caprini risk scores and the incidence of perioperative venous thromboembolic outcomes. Results A total of 2016 patients were identified. The overall 30-day rate of VTE was 1.3%. The incidence of VTE in patients with a Caprini risk score of 6 or less was 0.5%. For patients with scores of 7 or 8, the incidence was 2.4%. Patients with a Caprini risk score greater than 8 had an 18.3% incidence of VTE and were significantly more likely to develop a VTE when compared to patients with a Caprini risk score less than 8 (P otolaryngology patients for 30-day VTE events and allows otolaryngologists to identify patient subgroups who have a higher risk of VTE in the absence of chemoprophylaxis. PMID:22261490

  18. Stratified Charge Rotary Engine Critical Technology Enablement, Volume 1

    Science.gov (United States)

    Irion, C. E.; Mount, R. E.

    1992-01-01

    This report summarizes results of a critical technology enablement effort with the stratified charge rotary engine (SCRE) focusing on a power section of 0.67 liters (40 cu. in.) per rotor in single and two rotor versions. The work is a continuation of prior NASA Contracts NAS3-23056 and NAS3-24628. Technical objectives are multi-fuel capability, including civil and military jet fuel and DF-2, fuel efficiency of 0.355 Lbs/BHP-Hr. at best cruise condition above 50 percent power, altitude capability of up to 10Km (33,000 ft.) cruise, 2000 hour TBO and reduced coolant heat rejection. Critical technologies for SCRE's that have the potential for competitive performance and cost in a representative light-aircraft environment were examined. Objectives were: the development and utilization of advanced analytical tools, i.e. higher speed and enhanced three dimensional combustion modeling; identification of critical technologies; development of improved instrumentation, and to isolate and quantitatively identify the contribution to performance and efficiency of critical components or subsystems.

  19. Layer contributions to the nonlinear acoustic radiation from stratified media.

    Science.gov (United States)

    Vander Meulen, François; Haumesser, Lionel

    2016-12-01

    This study presents the thorough investigation of the second harmonic generation scenario in a three fluid layer system. An emphasis is on the evaluation of the nonlinear parameter B/A in each layer from remote measurements. A theoretical approach of the propagation of a finite amplitude acoustic wave in a multilayered medium is developed. In the frame of the KZK equation, the weak nonlinearity of the media, attenuation and diffraction effects are computed for the fundamental and second harmonic waves propagating back and forth in each of the layers of the system. The model uses a gaussian expansion to describe the beam propagation in order to quantitatively evaluate the contribution of each part of the system (layers and interfaces) to its nonlinearity. The model is validated through measurements on a water/aluminum/water system. Transmission as well as reflection configurations are studied. Good agreement is found between the theoretical results and the experimental data. The analysis of the second harmonic field sources measured by the transducers from outside the stratified medium highlights the factors that favor the cumulative effects. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Local properties of countercurrent stratified steam-water flow

    International Nuclear Information System (INIS)

    Kim, H.J.

    1985-10-01

    A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel/flat plate geometry over a wide range of inclination angles (4 0 -87 0 ) at several aspect ratios. Variables were inlet water and steam flow rates, and inlet water temperature. Local condensation rates and pressure gradients were measured, and local condensation heat transfer coefficients and interfacial shear stress were calculated. Contact probe traverses of the surface waves were made, which allowed a statistical analysis of the wave properties. The local condensation Nusselt number was correlated in terms of local water and steam Reynolds or Froude numbers, as well as the liquid Prandtl number. A turbulence-centered model developed by Theofanous, et al. principally for gas absorption in several geometries, was modified. A correlation for the interfacial shear stress and the pressure gradient agreed with measured values. Mean water layer thicknesses were calculated. Interfacial wave parameters, such as the mean water layer thickness, liquid fraction probability distribution, wave amplitude and wave frequency, are analyzed

  1. Distribution-Preserving Stratified Sampling for Learning Problems.

    Science.gov (United States)

    Cervellera, Cristiano; Maccio, Danilo

    2017-06-09

    The need for extracting a small sample from a large amount of real data, possibly streaming, arises routinely in learning problems, e.g., for storage, to cope with computational limitations, obtain good training/test/validation sets, and select minibatches for stochastic gradient neural network training. Unless we have reasons to select the samples in an active way dictated by the specific task and/or model at hand, it is important that the distribution of the selected points is as similar as possible to the original data. This is obvious for unsupervised learning problems, where the goal is to gain insights on the distribution of the data, but it is also relevant for supervised problems, where the theory explains how the training set distribution influences the generalization error. In this paper, we analyze the technique of stratified sampling from the point of view of distances between probabilities. This allows us to introduce an algorithm, based on recursive binary partition of the input space, aimed at obtaining samples that are distributed as much as possible as the original data. A theoretical analysis is proposed, proving the (greedy) optimality of the procedure together with explicit error bounds. An adaptive version of the algorithm is also introduced to cope with streaming data. Simulation tests on various data sets and different learning tasks are also provided.

  2. Double-diffusive convection and baroclinic instability in a differentially heated and initially stratified rotating system: the barostrat instability

    Energy Technology Data Exchange (ETDEWEB)

    Vincze, Miklos; Borcia, Ion; Harlander, Uwe [Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology (BTU) Cottbus-Senftenberg, Siemens-Halske-Ring 14, D-03046 Cottbus (Germany); Gal, Patrice Le, E-mail: vincze.m@lecso.elte.hu [Institut de Recherche sur les Phénomènes Hors Equilibre, CNRS—Aix-Marseille University—Ecole Centrale Marseille, 49 rue F. Joliot-Curie, F-13384 Marseille (France)

    2016-12-15

    A water-filled differentially heated rotating annulus with initially prepared stable vertical salinity profiles is studied in the laboratory. Based on two-dimensional horizontal particle image velocimetry data and infrared camera visualizations, we describe the appearance and the characteristics of the baroclinic instability in this original configuration. First, we show that when the salinity profile is linear and confined between two non-stratified layers at top and bottom, only two separate shallow fluid layers can be destabilized. These unstable layers appear nearby the top and the bottom of the tank with a stratified motionless zone between them. This laboratory arrangement is thus particularly interesting to model geophysical or astrophysical situations where stratified regions are often juxtaposed to convective ones. Then, for more general but stable initial density profiles, statistical measures are introduced to quantify the extent of the baroclinic instability at given depths and to analyze the connections between this depth-dependence and the vertical salinity profiles. We find that, although the presence of stable stratification generally hinders full-depth overturning, double-diffusive convection can lead to development of multicellular sideways convection in shallow layers and subsequently to a multilayered baroclinic instability. Therefore we conclude that by decreasing the characteristic vertical scale of the flow, stratification may even enhance the formation of cyclonic and anticyclonic eddies (and thus, mixing) in a local sense. (paper)

  3. Double-diffusive convection and baroclinic instability in a differentially heated and initially stratified rotating system: the barostrat instability

    International Nuclear Information System (INIS)

    Vincze, Miklos; Borcia, Ion; Harlander, Uwe; Gal, Patrice Le

    2016-01-01

    A water-filled differentially heated rotating annulus with initially prepared stable vertical salinity profiles is studied in the laboratory. Based on two-dimensional horizontal particle image velocimetry data and infrared camera visualizations, we describe the appearance and the characteristics of the baroclinic instability in this original configuration. First, we show that when the salinity profile is linear and confined between two non-stratified layers at top and bottom, only two separate shallow fluid layers can be destabilized. These unstable layers appear nearby the top and the bottom of the tank with a stratified motionless zone between them. This laboratory arrangement is thus particularly interesting to model geophysical or astrophysical situations where stratified regions are often juxtaposed to convective ones. Then, for more general but stable initial density profiles, statistical measures are introduced to quantify the extent of the baroclinic instability at given depths and to analyze the connections between this depth-dependence and the vertical salinity profiles. We find that, although the presence of stable stratification generally hinders full-depth overturning, double-diffusive convection can lead to development of multicellular sideways convection in shallow layers and subsequently to a multilayered baroclinic instability. Therefore we conclude that by decreasing the characteristic vertical scale of the flow, stratification may even enhance the formation of cyclonic and anticyclonic eddies (and thus, mixing) in a local sense. (paper)

  4. Postoperative Complications of Total Joint Arthroplasty in Obese Patients Stratified by BMI.

    Science.gov (United States)

    Zusmanovich, Mikhail; Kester, Benjamin S; Schwarzkopf, Ran

    2018-03-01

    High body mass index (BMI) is associated with significant complications in patients undergoing total joint arthroplasty. Many studies have evaluated this trend, but few have looked at the rates of complications based on BMI as a continuous variable. The purpose of this study was to stratify obese patients into 3 BMI categories and evaluate their rates of complications and gauge whether transitioning from higher to lower BMI category lowers complication. Patients undergoing primary total joint arthroplasty were selected from the National Surgical Quality Improvement Program database from 2008-2015 and arranged into 3 groups based on BMI: O1 (BMI 30-34.9 kg/m 2 ), O2 (BMI 35-39.9 kg/m 2 ), and O3 (BMI >40 kg/m 2 ). Thirty-day complications were recorded and evaluated utilizing univariate and multivariate analyses stratified by BMI. A total of 268,663 patients were identified. Patients with a BMI >30 kg/m 2 had more infectious and medical complications compared with nonobese patients. Furthermore, there were increased complications as the BMI categories increased. Patients with a BMI >40 kg/m 2 (O3) had longer operating times, length of stay, higher rates of readmissions, reoperations, deep venous thrombosis, renal insufficiency, superficial infections, deep infections, and wound dehiscence. These trends were present when comparing the O2 with O1 category as well. We have demonstrated increased rates of medical and surgical complications in obese patients. Furthermore, we demonstrated a stepwise increase in complication rates when transitioning to higher BMI groups. Based on our data, we believe that preoperative counseling and interventions to decrease BMI should be explored before offering elective surgery to obese patients. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Large eddy simulation and laboratory experiments on the decay of grid wakes in strongly stratified flows

    International Nuclear Information System (INIS)

    Fraunie, P.; Berrella, S.; Chashechkin, Y.D.; Velasco, D.; Redondo, M.

    2008-01-01

    A detailed analysis of the flow structure resulting from the combination of turbulence and internal waves is carried out and visualized by means of the Schlieren method on waves in a strongly stratified fluid at the Laboratory of the IPM in Moscow. The joint appearance of the more regular internal wave oscillations and the small-scale turbulence that is confined vertically to the Ozmidov length scale favours the use of a simple geometrical analysis to investigate their time-space span and evolution. This provides useful information on the collapse of internal wave breaking processes in the ocean and the atmosphere. The measurements were performed under a variety of linear stratifications and different grid forcing scales, combining the grid wake and velocity shear. A numerical simulation using LES on the passage of a single bar in a linearly stratified fluid medium has been compared with the experiments identifying the different influences of the environmental agents on the actual affective vertical diffusion of the wakes. The equation of state, which connects the density and salinity, is assumed to be linear, with the coefficient of the salt contraction being included into the definition of salinity or heat. The characteristic internal waves as well as the entire beam width are related to the diameter of the bar, the Richardson number and the peak-to-peak value of oscillations. The ultimate frequency of the infinitesimal periodic internal waves is limited by the maximum buoyancy frequency relating the decrease in the vertical scale with the anisotropy of the velocity turbulent r.m.s. velocity.

  6. Decreasing relative risk premium

    DEFF Research Database (Denmark)

    Hansen, Frank

    2007-01-01

    such that the corresponding relative risk premium is a decreasing function of present wealth, and we determine the set of associated utility functions. We find a new characterization of risk vulnerability and determine a large set of utility functions, closed under summation and composition, which are both risk vulnerable...

  7. Decreasing asthma morbidity

    African Journals Online (AJOL)

    1994-12-12

    Dec 12, 1994 ... Apart from the optimal use of drugs, various supplementary methods have been tested to decrease asthma morbidity, usually in patients from reiatively affluent socio-economic backgrounds. A study of additional measures taken in a group of moderate to severe adult asthmatics from very poor socio- ...

  8. Second law characterization of stratified thermal storage tanks

    Energy Technology Data Exchange (ETDEWEB)

    Fraidenraich, N [Departamento de Energia Nuclear-UFPE (Brazil)

    2000-07-01

    It is well known that fluid stratification in thermal storage tanks improves the overall performance of solar thermal systems, when compared with systems operating with uniform fluid temperature. From the point of view of the first law of thermodynamics, no difference exists between storage tanks with the same mass and average temperature, even if they have different stratified thermal structures. Nevertheless, the useful thermal energy that can be obtained from them might differ significantly. In this work, we derive an expression able to characterize the stratified configuration of thermal fluid. Using results obtained by thermodynamics of irreversible processes, the procedure adopted consists in calculating the maximum work available from the tank's thermal layer is able to develop. We arrive, then, at a dimensionless expression, the stratification parameter (SP), which depends on the mass fraction and absolute temperature of each thermal layer as well as the thermal fluid average temperature. Numerical examples for different types of tank stratification are given and it is verified that the expression obtained is sensitive to small differences in the reservoir thermal configuration. For example a thermal storage with temperatures equal to 74 Celsius degrees, 64 Celsius degrees and 54 Celsius degrees, with its mass equally distributed along the tank yields, for the parameter SP, a figure equal to 0.000294. On the other hand a storage tank with the same average temperature but with different layer's temperatures 76 Celsius degrees, 64 and 52 Celsius degrees, also with uniform mass distribution, yields for SP a value equal to quantitative evaluation of the stratification structure of thermal reservoirs. [Spanish] Es bien conocido que la estratificacion fluida en tanques de almacenamiento termico mejora el rendimiento total de los sistemas termicos solares en comparacion con sistemas que operan con temperatura uniforme del fluido. Desde el punto de vista

  9. Multigrid Computation of Stratified Flow over Two-Dimensional Obstacles

    Science.gov (United States)

    Paisley, M. F.

    1997-09-01

    A robust multigrid method for the incompressible Navier-Stokes equations is presented and applied to the computation of viscous flow over obstacles in a bounded domain under conditions of neutral stability and stable density stratification. Two obstacle shapes have been used, namely a vertical barrier, for which the grid is Cartesian, and a smooth cosine-shaped obstacle, for which a boundary-conforming transformation is incorporated. Results are given for laminar flows at low Reynolds numbers and turbulent flows at a high Reynolds number, when a simple mixing length turbulence model is included. The multigrid algorithm is used to compute steady flows for each obstacle at low and high Reynolds numbers in conditions of weak static stability, defined byK=ND/πU≤ 1, whereU,N, andDare the upstream velocity, bouyancy frequency, and domain height respectively. Results are also presented for the vertical barrier at low and high Reynolds number in conditions of strong static stability,K> 1, when lee wave motions ensure that the flow is unsteady, and the multigrid algorithm is used to compute the flow at each timestep.

  10. A Comparison of the Characteristics of Planar and Axisymmetric Bluff-Body Combustors Operated under Stratified Inlet Mixture Conditions

    Directory of Open Access Journals (Sweden)

    G. Paterakis

    2013-01-01

    Full Text Available The work presents comparisons of the flame stabilization characteristics of axisymmetric disk and 2D slender bluff-body burner configurations, operating with inlet mixture stratification, under ultralean conditions. A double cavity propane air premixer formed along three concentric disks, supplied with a radial equivalence ratio gradient the afterbody disk recirculation, where the first flame configuration is stabilized. Planar fuel injection along the center plane of the leading face of a slender square cylinder against the approach cross-flow results in a stratified flame configuration stabilized alongside the wake formation region in the second setup. Measurements of velocities, temperatures, OH∗ and CH∗ chemiluminescence, local extinction criteria, and large-eddy simulations are employed to examine a range of ultralean and close to extinction flame conditions. The variations of the reacting front disposition within these diverse reacting wake topologies, the effect of the successive suppression of heat release on the near flame region characteristics, and the reemergence of large-scale vortical activity on approach to lean blowoff (LBO are investigated. The cross-correlation of the performance of these two popular flame holders that are at the opposite ends of current applications might offer helpful insights into more effective control measures for expanding the operational margin of a wider range of stabilization configurations.

  11. Undersized description on motile gyrotactic micro-organisms individualities in MHD stratified water-based Newtonian nanofluid

    Science.gov (United States)

    Rehman, Khalil Ur; Malik, Aneeqa Ashfaq; Tahir, M.; Malik, M. Y.

    2018-03-01

    The current pagination summarized the influence of bio-convection Schmidt number, bio-convection Peclet number and micro-organisms concentration difference parameter on the density of motile gyrotactic micro-organisms when they have interaction with the thermally stratified magneto-nanofluid flow past a vertical stretching surface. It is observed that the density of motile microorganisms is the decreasing function of the bio-convection Schmidt and Peclet numbers. It is trusted that the outcomes of present analysis will serve as a helping source for the upcoming developments regarding individualities of motile gyrotactic micro-organisms subject to boundary layer flows induced by stretching surfaces.

  12. New numerical approaches for modeling thermochemical convection in a compositionally stratified fluid

    Science.gov (United States)

    Puckett, Elbridge Gerry; Turcotte, Donald L.; He, Ying; Lokavarapu, Harsha; Robey, Jonathan M.; Kellogg, Louise H.

    2018-03-01

    Geochemical observations of mantle-derived rocks favor a nearly homogeneous upper mantle, the source of mid-ocean ridge basalts (MORB), and heterogeneous lower mantle regions. Plumes that generate ocean island basalts are thought to sample the lower mantle regions and exhibit more heterogeneity than MORB. These regions have been associated with lower mantle structures known as large low shear velocity provinces (LLSVPS) below Africa and the South Pacific. The isolation of these regions is attributed to compositional differences and density stratification that, consequently, have been the subject of computational and laboratory modeling designed to determine the parameter regime in which layering is stable and understanding how layering evolves. Mathematical models of persistent compositional interfaces in the Earth's mantle may be inherently unstable, at least in some regions of the parameter space relevant to the mantle. Computing approximations to solutions of such problems presents severe challenges, even to state-of-the-art numerical methods. Some numerical algorithms for modeling the interface between distinct compositions smear the interface at the boundary between compositions, such as methods that add numerical diffusion or 'artificial viscosity' in order to stabilize the algorithm. We present two new algorithms for maintaining high-resolution and sharp computational boundaries in computations of these types of problems: a discontinuous Galerkin method with a bound preserving limiter and a Volume-of-Fluid interface tracking algorithm. We compare these new methods with two approaches widely used for modeling the advection of two distinct thermally driven compositional fields in mantle convection computations: a high-order accurate finite element advection algorithm with entropy viscosity and a particle method that carries a scalar quantity representing the location of each compositional field. All four algorithms are implemented in the open source finite

  13. Experimental Validation of a Domestic Stratified Hot Water Tank Model in Modelica for Annual Performance Assessment

    DEFF Research Database (Denmark)

    Carmo, Carolina; Dumont, Olivier; Nielsen, Mads Pagh

    2015-01-01

    The use of stratified hot water tanks in solar energy systems - including ORC systems - as well as heat pump systems is paramount for a better performance of these systems. However, the availability of effective and reliable models to predict the annual performance of stratified hot water tanks...

  14. Properties of the endogenous post-stratified estimator using a random forests model

    Science.gov (United States)

    John Tipton; Jean Opsomer; Gretchen G. Moisen

    2012-01-01

    Post-stratification is used in survey statistics as a method to improve variance estimates. In traditional post-stratification methods, the variable on which the data is being stratified must be known at the population level. In many cases this is not possible, but it is possible to use a model to predict values using covariates, and then stratify on these predicted...

  15. Implementing content constraints in alpha-stratified adaptive testing using a shadow test approach

    NARCIS (Netherlands)

    van der Linden, Willem J.; Chang, Hua-Hua

    2001-01-01

    The methods of alpha-stratified adaptive testing and constrained adaptive testing with shadow tests are combined in this study. The advantages are twofold. First, application of the shadow test allows the researcher to implement any type of constraint on item selection in alpha-stratified adaptive

  16. Stratified turbulent Bunsen flames : flame surface analysis and flame surface density modelling

    NARCIS (Netherlands)

    Ramaekers, W.J.S.; Oijen, van J.A.; Goey, de L.P.H.

    2012-01-01

    In this paper it is investigated whether the Flame Surface Density (FSD) model, developed for turbulent premixed combustion, is also applicable to stratified flames. Direct Numerical Simulations (DNS) of turbulent stratified Bunsen flames have been carried out, using the Flamelet Generated Manifold

  17. Turbulence Statistics of a Buoyant Jet in a Stratified Environment

    Science.gov (United States)

    McCleney, Amy Brooke

    Using non-intrusive optical diagnostics, turbulence statistics for a round, incompressible, buoyant, and vertical jet discharging freely into a stably linear stratified environment is studied and compared to a reference case of a neutrally buoyant jet in a uniform environment. This is part of a validation campaign for computational fluid dynamics (CFD). Buoyancy forces are known to significantly affect the jet evolution in a stratified environment. Despite their ubiquity in numerous natural and man-made flows, available data in these jets are limited, which constrain our understanding of the underlying physical processes. In particular, there is a dearth of velocity field data, which makes it challenging to validate numerical codes, currently used for modeling these important flows. Herein, jet near- and far-field behaviors are obtained with a combination of planar laser induced fluorescence (PLIF) and multi-scale time-resolved particle image velocimetry (TR-PIV) for Reynolds number up to 20,000. Deploying non-intrusive optical diagnostics in a variable density environment is challenging in liquids. The refractive index is strongly affected by the density, which introduces optical aberrations and occlusions that prevent the resolution of the flow. One solution consists of using index matched fluids with different densities. Here a pair of water solutions - isopropanol and NaCl - are identified that satisfy these requirements. In fact, they provide a density difference up to 5%, which is the largest reported for such fluid pairs. Additionally, by design, the kinematic viscosities of the solutions are identical. This greatly simplifies the analysis and subsequent simulations of the data. The spectral and temperature dependence of the solutions are fully characterized. In the near-field, shear layer roll-up is analyzed and characterized as a function of initial velocity profile. In the far-field, turbulence statistics are reported for two different scales, one

  18. Thermal stratification built up in hot water tank with different inlet stratifiers

    DEFF Research Database (Denmark)

    Dragsted, Janne; Furbo, Simon; Dannemand, Mark

    2017-01-01

    Thermal stratification in a water storage tank can strongly increase the thermal performance of solar heating systems. Thermal stratification can be built up in a storage tank during charge, if the heated water enters through an inlet stratifier. Experiments with a test tank have been carried out...... in order to elucidate how well thermal stratification is established in the tank with differently designed inlet stratifiers under different controlled laboratory conditions. The investigated inlet stratifiers are from Solvis GmbH & Co KG and EyeCular Technologies ApS. The inlet stratifier from Solvis Gmb...... for Solvis GmbH & Co KG had a better performance at 4 l/min. In the intermediate charge test the stratifier from EyeCular Technologies ApS had a better performance in terms of maintaining the thermal stratification in the storage tank while charging with a relative low temperature. [All rights reserved...

  19. Horizontal stratified flow model for the 1-D module of WCOBRA/TRAC-TF2: modeling and validation

    Energy Technology Data Exchange (ETDEWEB)

    Liao, J.; Frepoli, C.; Ohkawa, K., E-mail: liaoj@westinghouse.com [Westinghouse Electric Company LLC, LOCA Integrated Services I, Cranberry Twp, Pennsylvania (United States)

    2011-07-01

    For a two-phase flow in a horizontal pipe, the individual phases may separate by gravity. This horizontal stratification significantly impacts the interfacial drag, interfacial heat transfer and wall drag of the two phase flow. For a PWR small break LOCA, the horizontal stratification in cold legs is a highly important phenomenon during loop seal clearance, boiloff and recovery periods. The low interfacial drag in the stratified flow directly controls the time period for the loop clearance and the level of residual water in the loop seal. Horizontal stratification in hot legs also impacts the natural circulation stage of a small break LOCA. In addition, the offtake phenomenon and cold leg condensation phenomenon are also affected by the occurrence of horizontal stratification in the cold legs. In the 1-D module of the WCOBRA/TRAC-TF2 computer code, a horizontal stratification criterion was developed by combining the Taitel-Dukler model and the Wallis-Dobson model, which approximates the viscous Kelvin-Helmholtz neutral stability boundary. The objective of this paper is to present the horizontal stratification model implemented in the code and its assessment against relevant data. The adequacy of the horizontal stratification transition criterion is confirmed by examining the code-predicted flow regime in a horizontal pipe with the measured data in the flow regime map. The void fractions (or liquid level) for the horizontal stratified flow in cold leg or hot leg are predicted with a reasonable accuracy. (author)

  20. Indications for tonsillectomy stratified by the level of evidence

    Science.gov (United States)

    Windfuhr, Jochen P.

    2016-01-01

    Background: One of the most significant clinical trials, demonstrating the efficacy of tonsillectomy (TE) for recurrent throat infection in severely affected children, was published in 1984. This systematic review was undertaken to compile various indications for TE as suggested in the literature after 1984 and to stratify the papers according to the current concept of evidence-based medicine. Material and methods: A systematic Medline research was performed using the key word of “tonsillectomy“ in combination with different filters such as “systematic reviews“, “meta-analysis“, “English“, “German“, and “from 1984/01/01 to 2015/05/31“. Further research was performed in the Cochrane Database of Systematic Reviews, National Guideline Clearinghouse, Guidelines International Network and BMJ Clinical Evidence using the same key word. Finally, data from the “Trip Database” were researched for “tonsillectomy” and “indication“ and “from: 1984 to: 2015“ in combination with either “systematic review“ or “meta-analysis“ or “metaanalysis”. Results: A total of 237 papers were retrieved but only 57 matched our inclusion criteria covering the following topics: peritonsillar abscess (3), guidelines (5), otitis media with effusion (5), psoriasis (3), PFAPA syndrome (6), evidence-based indications (5), renal diseases (7), sleep-related breathing disorders (11), and tonsillitis/pharyngitis (12), respectively. Conclusions: 1) The literature suggests, that TE is not indicated to treat otitis media with effusion. 2) It has been shown, that the PFAPA syndrome is self-limiting and responds well to steroid administration, at least in a considerable amount of children. The indication for TE therefore appears to be imbalanced but further research is required to clarify the value of surgery. 3) Abscesstonsillectomy as a routine is not justified and indicated only for cases not responding to other measures of treatment, evident complications

  1. Hydrogeologic appraisal of a stratified-drift aquifer near Smyrna, Chenango County, New York

    Science.gov (United States)

    Reynolds, R.J.; Brown, G.A.

    1984-01-01

    A broad, Y-shaped valley near Smyrna, New York, contains extensive water-table and confined aquifers that are largely hydraulically separated from the nearby Chenango River to the east. Accordingly, ground-water withdrawals from this valley would not appreciably decrease streamflow in the Chenango River by induced infiltration and could be used for specialized needs. The aquifers in the valley are capable of sustaining a long-term total withdrawal of about 12.7 million gallons per day during prolonged drought conditions. Larger withdrawals could be made on a short-term basis or during periods of normal or above-normal precipitation. Saturated thickness of undifferentiated stratified-drift deposits in the valley ranges from 20 feet in the northwestern part of the valley to more than 300 feet at its southern end. Direct areal recharge accounts for about 56 percent of the total recharge to the valley aquifer infiltration from streams accounts for 24 percent, and runoff from the adjacent till-mantled hillsides accounts for 20 percent. The water-table and confined aquifers within the valley hold at least 19.6 billion gallons of usable ground water in storage. (USGS)

  2. Exploring the salivary microbiome of children stratified by the oral hygiene index

    Science.gov (United States)

    Mashima, Izumi; Theodorea, Citra F.; Thaweboon, Boonyanit; Thaweboon, Sroisiri; Scannapieco, Frank A.

    2017-01-01

    Poor oral hygiene often leads to chronic diseases such as periodontitis and dental caries resulting in substantial economic costs and diminished quality of life in not only adults but also in children. In this study, the salivary microbiome was characterized in a group of children stratified by the Simplified Oral Hygiene Index (OHI-S). Illumina MiSeq high-throughput sequencing based on the 16S rRNA was utilized to analyze 90 salivary samples (24 Good, 31 Moderate and 35 Poor oral hygiene) from a cohort of Thai children. A total of 38,521 OTUs (Operational Taxonomic Units) with a 97% similarity were characterized in all of the salivary samples. Twenty taxonomic groups (Seventeen genera, two families and one class; Streptococcus, Veillonella, Gemellaceae, Prevotella, Rothia, Porphyromonas, Granulicatella, Actinomyces, TM-7-3, Leptotrichia, Haemophilus, Selenomonas, Neisseria, Megasphaera, Capnocytophaga, Oribacterium, Abiotrophia, Lachnospiraceae, Peptostreptococcus, and Atopobium) were found in all subjects and constituted 94.5–96.5% of the microbiome. Of these twenty genera, the proportion of Streptococcus decreased while Veillonella increased with poor oral hygiene status (P oral hygiene group. This is the first study demonstrating an important association between increase of Veillonella and poor oral hygiene status in children. However, further studies are required to identify the majority of Veillonella at species level in salivary microbiome of the Poor oral hygiene group. PMID:28934367

  3. A stratified percolation model for saturated and unsaturated flow through natural fractures

    International Nuclear Information System (INIS)

    Pyrak-Nolte, L.J.

    1990-01-01

    The geometry of the asperities of contact between the two surfaces of a fracture and of the adjacent void spaces determines fluid flow through a fracture and the mechanical deformation across a fracture. Heuristically we have developed a stratified continuum percolation model to describe this geometry based on a fractal construction that includes scale invariance and correlation of void apertures. Deformation under stress is analyzed using conservation of rock volume to correct for asperity interpenetration. Single phase flow is analyzed using a critical path along which the principal resistance is a result of laminar flow across the critical neck in this path. Results show that flow decreases with apparent aperture raised to a variable power greater than cubic, as is observed in flow experiments on natural fractures. For two phases, flow of the non-wetting phase is likewise governed by the critical neck along the critical path of largest aperture but flow of the wetting phase is governed by tortuosity. 17 refs., 10 figs

  4. Investigation of Stratified Thermal Storage Tank Performance for Heating and Cooling Applications

    Directory of Open Access Journals (Sweden)

    Azharul Karim

    2018-04-01

    Full Text Available A large amount of energy is consumed by heating and cooling systems to provide comfort conditions for commercial building occupants, which generally contribute to peak electricity demands. Thermal storage tanks in HVAC systems, which store heating/cooling energy in the off-peak period for use in the peak period, can be used to offset peak time energy demand. In this study, a theoretical investigation on stratified thermal storage systems is performed to determine the factors that significantly influence the thermal performance of these systems for both heating and cooling applications. Five fully-insulated storage tank geometries, using water as the storage medium, were simulated to determine the effects of water inlet velocity, tank aspect ratio and temperature difference between charging (inlet and the tank water on mixing and thermocline formation. Results indicate that thermal stratification enhances with increased temperature difference, lower inlet velocities and higher aspect ratios. It was also found that mixing increased by 303% when the temperature difference between the tank and inlet water was reduced from 80 °C to 10 °C, while decreasing the aspect ratio from 3.8 to 1.0 increased mixing by 143%. On the other hand, increasing the inlet water velocity significantly increased the storage mixing. A new theoretical relationship between the inlet water velocity and thermocline formation has been developed. It was also found that inlet flow rates can be increased, without increasing the mixing, after the formation of the thermocline.

  5. Two-phase flow through small branches in a horizontal pipe with stratified flow

    International Nuclear Information System (INIS)

    Smoglie, C.

    1985-02-01

    In the field of reactor safety the occurrence of a small break in a horizontal primary coolant pipe is of great importance. This report presents the description and results of experiments designed to determine the mass flow rate and quality through a small break at the bottom, the top or the side of a main pipe with stratified gas-liquid flow. If the interface level is far below (above) the branch, only single-phase gas (liquid) flow enters the branch. For smaller distances the interface is locally deformed because of the pressure decrease due to the fluid acceleration near the branch inlet (Bernoulli effect) and liquid (gas) can be entrained. This report contains photographs illustrating the flow phenomena as well as a general correlation to determine the beginning of entrainment. Results are presented on the branch mass flow rate and quality as a function of a normalized distance between the interface and the branch inlet. A model was developed which enables to predict the branch quality and mass flux. Results from air-water flow through horizontal branches, were extrapolated for steam water flow at high pressure with critical branch mass flux. (orig./HS) [de

  6. Two-phase flow through small branches in a horizontal pipe with stratified flow

    International Nuclear Information System (INIS)

    Smoglie, C.

    1984-12-01

    This report presents the description and results of experiments designed to determine the mass flow rate and quality through a small break at the bottom, the top or the side of a main pipe with stratified gas-liquid flow. If the interface level is far below (above) the branch, only single-phase gas (liquid) flow enters the branch. For smaller distances the interface is locally deformed because of the pressure decrease due to the fluid acceleration near the branch inlet (Bernoulli effect) and liquid (gas) can be entrained. This report contains photographs illustrating the flow phenomena as well as a general correlation to determine the beginning of entrainment. Results are presented on the branch mass flow rate and quality as a function of a normalized distance between the interface and the branch inlet. A model was developed which enables to predict the branch quality and mass flux. Results from air-water flow through horizontal branches, were extrapolated for steam water flow at high pressure with critical branch mass flux. (orig./HP) [de

  7. Influences of source condition and dissolution on bubble plume in a stratified environment

    Science.gov (United States)

    Chu, Shigan; Prosperetti, Andrea

    2017-11-01

    A cross-sectionally averaged model is used to study a bubble plume rising in a stratified quiescent liquid. Scaling analyses for the peel height, at which the plume momentum vanishes, and the neutral height, at which its average density equals the ambient density, are presented. Contrary to a widespread practice in the literature, it is argued that the neutral height cannot be identified with the experimentally reported intrusion height. Recognizing this difference provides an explanation of the reason why the intrusion height is found so frequently to lie so much above predictions, and brings the theoretical results in line with observations. The mathematical model depends on three dimensionless parameters, some of which are related to the inlet conditions at the plume source. Their influence on the peel and neutral heights is illustrated by means of numerical results. Aside from the source parameters, we incorporate dissolution of bubbles and the corresponding density change of plume into the model. Contrary to what's documented in literature, density change of plume due to dissolution plays an important role in keeping the total buoyancy of plume, thus alleviating the rapid decrease of peel height because of dissolution.

  8. Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

    Directory of Open Access Journals (Sweden)

    S. Masina

    2002-05-01

    Full Text Available Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC. Analysis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uniform, 10° wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simulate more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscillations that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature.  This study shows that the potential for baroclinic instability in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect.Key words. Oceanography: general (equatorial oceanography; numerical modeling – Oceanography: physics (fronts and jets

  9. Heat and mass transfers between two stratified liquid phases in a bubbly flow

    International Nuclear Information System (INIS)

    Lapuerta, C.

    2006-10-01

    During an hypothetical major accident in a pressurized water reactor, the deterioration of the core can produce a stratified pool crossed by a bubbly flow. This latter strongly impacts the heat transfers, whose intensities are crucial in the progression of the accident. In this context, this work is devoted to the diffuse interface modelling for the study of an-isothermal incompressible flows, composed of three immiscible components, with no phase change. In the diffuse interface methods, the system evolution is driven by the minimization of a free energy. The originality of our approach, derived from the Cahn-Hilliard model, is based on the particular form of the energy we proposed, which enables to have an algebraically and dynamically consistent model, in the following sense: on the one hand, the triphasic free energy is equal to the diphasic one when only two phases are present; on the other, if a phase is not initially present then it will not appear during system evolution, this last property being stable with respect to numerical errors. The existence and the uniqueness of weak and strong solutions are proved in two and three dimensions as well as a stability result for metastable states. The modelling of an an-isothermal three phase flow is further accomplished by coupling the Cahn-Hilliard equations with the energy balance and Navier-Stokes equations where surface tensions are taken into account through volume capillary forces. These equations are discretized in time and space in order to preserve properties of continuous model (volume conservation, energy estimate). Different numerical results are given, from the validation case of the lens spreading between two phases, to the study of the heat and mass transfers through a liquid/liquid interface crossed by a single bubble or a series of bubbles. (author)

  10. A recursive transfer-matrix solution for a dipole radiating inside and outside a stratified sphere

    International Nuclear Information System (INIS)

    Moroz, Alexander

    2005-01-01

    Fast and numerically stable transfer-matrix solution is presented for the classical electromagnetics problem of a dipole radiating inside and outside a stratified sphere consisting of concentric spherical shells. There is no limitation on the dipole position, the number of the concentric shells, the shell medium, or on the sphere radius. Electromagnetic fields are determined anywhere in the space, the time-averaged angular distribution of the radiated power, the total radiated power, Ohmic losses due to an absorbing shell, and Green's function are calculated. An absorbing, optically active, and ultrathin (-bar 10nm) metallic shell (core), characterized by a nonlocal dielectric function, are all allowed. The classical results are then applied to inelastic light scattering (fluorescence and Raman), the radiative and nonradiative normalized decay rates, and frequency shift. Using correspondence principle, the radiative decay rate is calculated from the Poynting vector, whereas the nonradiative decay rate is calculated from the Ohmic losses inside a sphere absorptive shell. Numerical stability of our method and limitations of classical description of decay rates are addressed. The importance of grouping various radiative and nonradiative decay mechanisms into local and nonlocal decay rates is emphasized. Further possible extensions of the theory presented here to the case of an arbitrary multilayered (axially symmetric) particle and to the classical problem of a radiating quadrupole in the presence of a multilayered particle are briefly outlined. Various applications for chemical speciation, LIDAR, fluorescent microscopy, engineering of decay rates, identification of biological particles, and monitoring specific cell functions are envisaged. Computer program is freely available at http://www.wave-scattering.com

  11. Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

    Directory of Open Access Journals (Sweden)

    S. Masina

    Full Text Available Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC. Analysis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uniform, 10° wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simulate more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscillations that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature. 

    This study shows that the potential for baroclinic instability in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect.

    Key words. Oceanography: general (equatorial oceanography; numerical modeling – Oceanography: physics (fronts and jets

  12. 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.

  13. Slip analysis of squeezing flow using doubly stratified fluid

    Science.gov (United States)

    Ahmad, S.; Farooq, M.; Javed, M.; Anjum, Aisha

    2018-06-01

    The non-isothermal flow is modeled and explored for squeezed fluid. The influence of velocity, thermal and solutal slip effects on transport features of squeezed fluid are analyzed through Darcy porous channel when fluid is moving due to squeezing of upper plate towards the stretchable lower plate. Dual stratification effects are illustrated in transport equations. A similarity analysis is performed and reduced governing flow equations are solved using moderated and an efficient convergent approach i.e. Homotopic technique. The significant effects of physical emerging parameters on flow velocity, temperature and fluid concentration are reporting through various plots. Graphical explanations for drag force, Nusselt and Sherwood numbers are stated and examined. The results reveal that minimum velocity field occurs near the plate, whereas it increases far away from the plate for strong velocity slip parameter. Furthermore, temperature and fluid concentration significantly decreases with increased slip effects. The current analysis is applicable in some advanced technological processes and industrial fluid mechanics.

  14. Economic viability of Stratified Medicine concepts : An investor perspective on drivers and conditions that favour using Stratified Medicine approaches in a cost-contained healthcare environment

    NARCIS (Netherlands)

    Fugel, Hans-Joerg; Nuijten, Mark; Postma, Maarten

    2016-01-01

    RATIONALE: Stratified Medicine (SM) is becoming a natural result of advances in biomedical science and a promising path for the innovation-based biopharmaceutical industry to create new investment opportunities. While the use of biomarkers to improve R&D efficiency and productivity is very much

  15. Theoretical study of evaporation heat transfer in horizontal microfin tubes: stratified flow model

    Energy Technology Data Exchange (ETDEWEB)

    Honda, H; Wang, Y S [Kyushu Univ., Inst. for Materials Chemistry and Engineering, Kasuga, Fukuoka (Japan)

    2004-08-01

    The stratified flow model of evaporation heat transfer in helically grooved, horizontal microfin tubes has been developed. The profile of stratified liquid was determined by a theoretical model previously developed for condensation in horizontal microfin tubes. For the region above the stratified liquid, the meniscus profile in the groove between adjacent fins was determined by a force balance between the gravity and surface tension forces. The thin film evaporation model was applied to predict heat transfer in the thin film region of the meniscus. Heat transfer through the stratified liquid was estimated by using an empirical correlation proposed by Mori et al. The theoretical predictions of the circumferential average heat transfer coefficient were compared with available experimental data for four tubes and three refrigerants. A good agreement was obtained for the region of Fr{sub 0}<2.5 as long as partial dry out of tube surface did not occur. (Author)

  16. Mechanisms and Variability of Salt Transport in Partially-Stratified Estuaries

    National Research Council Canada - National Science Library

    Bowen, Melissa

    2000-01-01

    .... Analysis of salt transport from observations in the Hudson Estuary show that stratified periods with elevated estuarine salt transport occur in five-day intervals once a month during apogean neap tides...

  17. Visualization of mole fraction distribution of slow jet forming stably stratified field

    International Nuclear Information System (INIS)

    Fumizawa, Motoo; Hishida, Makoto

    1990-01-01

    An experimental study has been performed to investigate the behavior of flow and mass transfer in gaseous slow jet in which buoyancy force opposed the flow forming stably stratified field. The study has been performed to understand the basic features of air ingress phenomena at pipe rupture accident of the high temperature gas-cooled reactor. A displacement fringe technique was adopted in Mach-Zehnder interferometer to visualize the mole fraction distribution. As the result, the followings were obtained: (1) The stably stratified fields were formed in the vicinity of the outlet of the slow jet. The penetration distance of the stably stratified fields increased with Froude number. (2) Mass fraction distributions in the stably stratified fields were well correlated with the present model using the ramp mole velocity profile. (author)

  18. Stratifying a Risk for an Increased Variation of Airway Caliber among the Clinically Stable Asthma

    Directory of Open Access Journals (Sweden)

    Atsushi Hayata

    2013-01-01

    Conclusions: These results indicate that ACQ, %FEV1 and FENO can stratify the risk for increased variation in airway caliber among patients with stable asthma. This may help identify subjects in whom further monitoring of lung function fluctuations is indicated.

  19. Dipole formation by two interacting shielded monopoles in a stratified fluid

    NARCIS (Netherlands)

    Beckers, M.; Clercx, H.J.H.; Heijst, van G.J.F.; Verzicco, R.

    2002-01-01

    The interaction between two shielded monopolar vortices has been investigated experimentally in a nonrotating linearly stratified fluid and by full three-dimensional (3D) numerical simulations. The characteristic Reynolds and Froude numbers in the experiments are approximately Re [[approximate

  20. Molecular polymorphism of a cell surface proteoglycan: distinct structures on simple and stratified epithelia.

    Science.gov (United States)

    Sanderson, R D; Bernfield, M

    1988-12-01

    Epithelial cells are organized into either a single layer (simple epithelia) or multiple layers (stratified epithelia). Maintenance of these cellular organizations requires distinct adhesive mechanisms involving many cell surface molecules. One such molecule is a cell surface proteoglycan, named syndecan, that contains both heparan sulfate and chondroitin sulfate chains. This proteoglycan binds cells to fibrillar collagens and fibronectin and thus acts as a receptor for interstitial matrix. The proteoglycan is restricted to the basolateral surface of simple epithelial cells, but is located over the entire surface of stratified epithelial cells, even those surfaces not contacting matrix. We now show that the distinct localization in simple and stratified epithelia correlates with a distinct proteoglycan structure. The proteoglycan from simple epithelia (modal molecular size, 160 kDa) is larger than that from stratified epithelia (modal molecular size, 92 kDa), but their core proteins are identical in size and immunoreactivity. The proteoglycan from simple epithelia has more and larger heparan sulfate and chondroitin sulfate chains than the proteoglycan from stratified epithelia. Thus, the cell surface proteoglycan shows a tissue-specific structural polymorphism due to distinct posttranslational modifications. This polymorphism likely reflects distinct proteoglycan functions in simple and stratified epithelia, potentially meeting the different adhesive requirements of the cells in these different organizations.

  1. Stabilizing Niger

    DEFF Research Database (Denmark)

    Hahonou, Eric Komlavi

    international intervention in Niger. Their main objective is to secure their own strategic, economic and political interests by strengthening the Nigerien authorities through direct intervention and capacity building activities. For western states reinforcing state security institutions and stabilizing elite...

  2. The structure of the stably stratified internal boundary layer in offshore flow over the sea

    Science.gov (United States)

    Garratt, J. R.; Ryan, B. F.

    1989-04-01

    Observations obtained mainly from a research aircraft are presented of the mean and turbulent structure of the stably stratified internal boundary layer (IBL) over the sea formed by warm air advection from land to sea. The potential temperature and humidity fields reveal the vertical extent of the IBL, for fetches out to several hundred of kilometres, geostrophic winds of 20 25 m s-1, and potential temperature differences between undisturbed continental air and the sea surface of 7 to 17 K. The dependence of IBL depth on these external parameters is discussed in the context of the numerical results of Garratt (1987), and some discrepancies are noted. Wind observations show the development of a low-level wind maximum (wind component normal to the coast) and rotation of the wind to smaller cross-isobar flow angles. Potential temperature (θ) profiles within the IBL reveal quite a different structure to that found in the nocturnal boundary layer (NBL) over land. Over the sea, θ profiles have large positive curvature with vertical gradients increasing monotonically with height; this reflects the dominance of turbulent cooling within the layer. The behaviour is consistent with known behaviour in the NBL over land where curvature becomes negative (vertical gradients of θ decreasing with height) as radiative cooling becomes dominant. Turbulent properties are discussed in terms of non-dimensional quantities, normalised by the surface friction velocity, as functions of normalised height using the IBL depth. Vertical profiles of these and the normalised wavelength of the spectral maximum agree well with known results for the stable boundary layer over land (Caughey et al., 1979).

  3. Stability of the stratifield cylindrical annulus flow. [toward a model of global atmospheric circulation

    Science.gov (United States)

    Antar, B. N.

    1980-01-01

    The linear stability analysis for the stratified flow between two rotating circular cylinders is formulated. Two approaches for the stability analysis are presented. The first approach results in an algebraic eigenvalue problem, while the second results in an initial value problem for the perturbation function. The advantages and disadvantages of both approaches are discussed and a preferable numerical solution technique is outlined.

  4. Population-Stratified Analysis of Bone Mineral Density Distribution in Cervical and Lumbar Vertebrae of Chinese from Quantitative Computed Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yong [Department of Radiology, The Fourth Clinical Medical College of Peking University, Beijing Jishuitan Hospital, Beijing 100035 (China); Zhou, Zhuang [Department of Orthopedic Oncology, The Third Hospital of Hebei Medical University, Shijiazhuang 050051 (China); Wu, Cheng' ai; Zhao, Danhui; Wang, Chao [Beijing Institute of Traumatology and Orthopedics, Beijing 100035 (China); Cheng, Xiaoguang; Cai, Wei; Wang, Ling; Duanmu, Yangyang; Zhang, Chenxin [Department of Radiology, The Fourth Clinical Medical College of Peking University, Beijing Jishuitan Hospital, Beijing 100035 (China); Tian, Wei [Department of Spine Surgery, The Fourth Clinical Medical College of Peking University, Beijing Jishuitan Hospital, Beijing 100035 (China)

    2016-11-01

    To investigate the bone mineral density (BMD) of cervical vertebrae in a population-stratified manner and correlate with that of the lumbar vertebrae. Five hundred and ninety-eight healthy volunteers (254 males, 344 females), ranging from 20 to 64 years of age, were recruited for volumetric BMD (vBMD) measurements by quantitative computed tomography. Basic information (age, height, weight, waistline, and hipline), and vBMD of the cervical and lumbar vertebrae (C2–7 and L2–4) were recorded. Comparisons among sex, age groups and different levels of vertebrae were analyzed using analysis of variance. Linear regression was performed for relevance of different vertebral levels. The vBMD of cervical and lumbar vertebrae was higher in females than males in each age group. The vBMD of the cervical and lumbar vertebrae in males and the vBMD of lumbar vertebrae in females decreased with aging. In each age group, the vBMD of the cervical vertebrae was higher than that of the lumbar vertebrae with gradual decreases from C2 to C7 except for C3; moreover, the vBMD of C6 and C7 was significantly different from that of C2–5. Correlations of vBMD among different cervical vertebrae (females: r = 0.62–0.94; males: r = 0.63–0.94) and lumbar vertebrae (males: r = 0.93–0.98; females: r = 0.82–0.97) were statistically significant at each age group. The present study provided normative data of cervical vertebrae in an age- and sex-stratified manner. Sex differences in vBMD prominently vary with age, which can be helpful to design a more comprehensive pre-operative surgical plan.

  5. Population=stratified analysis of bone mineral density distribution in cervical and lumbar vertebrae of chinese from quantitative computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yong; Cheng, Xiaoguang; Cai, Wei; Wang, Ling; Duanmu, Yangyang; Zhang, Chen Xin [Dept. of Radiology, The Fourth Clinical Medical College of Peking University, Beijing Jishuitan Hospital, Beijing (China); Zhou, Zhuang [Dept. of Orthopedic Oncology, The Third Hospital of Hebei Medical University, Shijiazhuang (China); Wu, Cheng' ai; Zhao, Danhui; Wang, Chao [Beijing Institute of Traumatology and Orthopedics, Beijing (China); Tian, Wei [Dept. of Spine Surgery, The Fourth Clinical Medical College of Peking University, Beijing Jishuitan Hospital, Beijing (China)

    2016-09-15

    To investigate the bone mineral density (BMD) of cervical vertebrae in a population-stratified manner and correlate with that of the lumbar vertebrae. Five hundred and ninety-eight healthy volunteers (254 males, 344 females), ranging from 20 to 64 years of age, were recruited for volumetric BMD (vBMD) measurements by quantitative computed tomography. Basic information (age, height, weight, waistline, and hipline), and vBMD of the cervical and lumbar vertebrae (C2–7 and L2–4) were recorded. Comparisons among sex, age groups and different levels of vertebrae were analyzed using analysis of variance. Linear regression was performed for relevance of different vertebral levels. The vBMD of cervical and lumbar vertebrae was higher in females than males in each age group. The vBMD of the cervical and lumbar vertebrae in males and the vBMD of lumbar vertebrae in females decreased with aging. In each age group, the vBMD of the cervical vertebrae was higher than that of the lumbar vertebrae with gradual decreases from C2 to C7 except for C3; moreover, the vBMD of C6 and C7 was significantly different from that of C2–5. Correlations of vBMD among different cervical vertebrae (females: r = 0.62–0.94; males: r = 0.63–0.94) and lumbar vertebrae (males: r = 0.93–0.98; females: r = 0.82–0.97) were statistically significant at each age group. The present study provided normative data of cervical vertebrae in an age- and sex-stratified manner. Sex differences in vBMD prominently vary with age, which can be helpful to design a more comprehensive pre-operative surgical plan.

  6. Education and patient preferences for treating type 2 diabetes: a stratified discrete-choice experiment

    Directory of Open Access Journals (Sweden)

    Janssen EM

    2017-10-01

    Full Text Available Ellen M Janssen,1 Daniel R Longo,2 Joan K Bardsley,3 John FP Bridges1 1Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 2Department of Family Medicine and Population Health, Virginia Commonwealth University, Richmond, VA, 3MedStar Health Research Institute and MedStar Nursing, Hyattsville, MD, USA Purpose: Diabetes is a chronic condition that is more prevalent among people with lower educational attainment. This study assessed the treatment preferences of patients with type 2 diabetes by educational attainment. Methods: Patients with type 2 diabetes were recruited from a national online panel in the US. Treatment preferences were assessed using a discrete-choice experiment. Participants completed 16 choice tasks in which they compared pairs of treatment profiles composed of six attributes: A1c decrease, stable blood glucose, low blood glucose, nausea, treatment burden, and out-of-pocket cost. Choice models and willingness-to-pay (WTP estimates were estimated using a conditional logit model and were stratified by educational status. Results: A total of 231 participants with a high school diploma or less education, 156 participants with some college education, and 165 participants with a college degree or more completed the survey. Participants with a college degree or more education were willing to pay more for A1c decreases ($58.84, standard error [SE]: 10.6 than participants who had completed some college ($28.47, SE: 5.53 or high school or less ($17.56, SE: 3.55 (p≤0.01. People with a college education were willing to pay more than people with high school or less to avoid nausea, low blood glucose events during the day/night, or two pills per day. Conclusion: WTP for aspects of diabetes medication differed for people with a college education or more and a high school education or less. Advanced statistical methods might overcome limitations of stratification and advance understanding

  7. Spinning phenomena and energetics of spherically pulsating patterns in stratified fluids

    International Nuclear Information System (INIS)

    Ibragimov, Ranis N; Dameron, Michael

    2011-01-01

    The nonlinear solutions of the two-dimensional Boussinesq equations describing internal waves in rotating stratified fluids were obtained as group invariant solutions. The latter nonlinear solutions correspond to the rotation transformation preserving the form of the original nonlinear equations of motion. It is shown that the obtained class of exact solutions can be associated with the spherically pulsating patterns observed in uniformly stratified fluids. It is also shown that the obtained rotationally symmetric solutions are bounded functions that can be visualized as spinning patterns in stratified fluids. It is also shown that the rotational transformation provides the energy conservation law together with other conservation laws for which the spinning phenomena is observed. The effects of nonlinearity and the Earth's rotation on such a phenomenon are also discussed.

  8. Two-phase air-water stratified flow measurement using ultrasonic techniques

    International Nuclear Information System (INIS)

    Fan, Shiwei; Yan, Tinghu; Yeung, Hoi

    2014-01-01

    In this paper, a time resolved ultrasound system was developed for investigating two-phase air-water stratified flow. The hardware of the system includes a pulsed wave transducer, a pulser/receiver, and a digital oscilloscope. The time domain cross correlation method is used to calculate the velocity profile along ultrasonic beam. The system is able to provide velocities with spatial resolution of around 1mm and the temporal resolution of 200μs. Experiments were carried out on single phase water flow and two-phase air-water stratified flow. For single phase water flow, the flow rates from ultrasound system were compared with those from electromagnetic flow (EM) meter, which showed good agreement. Then, the experiments were conducted on two-phase air-water stratified flow and the results were given. Compared with liquid height measurement from conductance probe, it indicated that the measured velocities were explainable

  9. A criterion for the onset of slugging in horizontal stratified air-water countercurrent flow

    International Nuclear Information System (INIS)

    Chun, Moon-Hyun; Lee, Byung-Ryung; Kim, Yang-Seok

    1995-01-01

    This paper presents an experimental and theoretical investigation of wave height and transition criterion from wavy to slug flow in horizontal air-water countercurrent stratified flow conditions. A theoretical formula for the wave height in a stratified wavy flow regime has been developed using the concept of total energy balance over a wave crest to consider the shear stress acting on the interface of two fluids. From the limiting condition of the formula for the wave height, a necessary criterion for transition from a stratified wavy flow to a slug flow has been derived. A series of experiments have been conducted changing the non-dimensional water depth and the flow rates of air in a horizontal pipe and a duct. Comparisons between the measured data and the predictions of the present theory show that the agreement is within ±8%

  10. A criterion for the onset of slugging in horizontal stratified air-water countercurrent flow

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Moon-Hyun; Lee, Byung-Ryung; Kim, Yang-Seok [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)] [and others

    1995-09-01

    This paper presents an experimental and theoretical investigation of wave height and transition criterion from wavy to slug flow in horizontal air-water countercurrent stratified flow conditions. A theoretical formula for the wave height in a stratified wavy flow regime has been developed using the concept of total energy balance over a wave crest to consider the shear stress acting on the interface of two fluids. From the limiting condition of the formula for the wave height, a necessary criterion for transition from a stratified wavy flow to a slug flow has been derived. A series of experiments have been conducted changing the non-dimensional water depth and the flow rates of air in a horizontal pipe and a duct. Comparisons between the measured data and the predictions of the present theory show that the agreement is within {plus_minus}8%.

  11. Macroeconomic stability

    DEFF Research Database (Denmark)

    Jespersen, Jesper

    2004-01-01

    It is demonstrated that full employment and sustainable development not necessarily are conflicting goals. On the other hand macroeconomic stability cannot be obtained without a deliberate labour sharing policy and a shift in the composition of private consumption away from traditional material...

  12. Stabilized superconductors

    International Nuclear Information System (INIS)

    Wong, J.

    1975-01-01

    The stable, high field, high current composite wire comprises multiple filaments in a depleted bronze matrix, each filament comprising a type II superconducting, beta-tungsten structure, intermetallic compound layer jacketing and metallurgically bonded to a stabilizing copper core, directly or via an intermediate layer of refractory metal

  13. Inhibition of Rho-associated kinases disturbs the collective cell migration of stratified TE-10 cells

    Directory of Open Access Journals (Sweden)

    Taro Mikami

    2015-01-01

    Full Text Available BACKGROUND: The collective cell migration of stratified epithelial cells is considered to be an important phenomenon in wound healing, development, and cancer invasion; however, little is known about the mechanisms involved. Furthermore, whereas Rho family proteins, including RhoA, play important roles in cell migration, the exact role of Rho-associated coiled coil-containing protein kinases (ROCKs in cell migration is controversial and might be cell-type dependent. Here, we report the development of a novel modified scratch assay that was used to observe the collective cell migration of stratified TE-10 cells derived from a human esophageal cancer specimen. RESULTS: Desmosomes were found between the TE-10 cells and microvilli of the surface of the cell sheet. The leading edge of cells in the cell sheet formed a simple layer and moved forward regularly; these rows were followed by the stratified epithelium. ROCK inhibitors and ROCK small interfering RNAs (siRNAs disturbed not only the collective migration of the leading edge of this cell sheet, but also the stratified layer in the rear. In contrast, RhoA siRNA treatment resulted in more rapid migration of the leading rows and disturbed movement of the stratified portion. CONCLUSIONS: The data presented in this study suggest that ROCKs play an important role in mediating the collective migration of TE-10 cell sheets. In addition, differences between the effects of siRNAs targeting either RhoA or ROCKs suggested that distinct mechanisms regulate the collective cell migration in the simple epithelium of the wound edge versus the stratified layer of the epithelium.

  14. Numerical simulation of stratified flows with different k-ε turbulence models

    International Nuclear Information System (INIS)

    Dagestad, S.

    1991-01-01

    The thesis comprises the numerical simulation of stratified flows with different k-ε models. When using the k-ε model, two equations are solved to describe the turbulence. The k-equation represents the turbulent kinetic energy of the turbulence and the ε-equation is the turbulent dissipation. Different k-ε models predict stratified flows differently. The standard k-ε model leads to higher turbulent mixing than the low-Reynolds model does. For lower Froude numbers, F 0 , this effect becomes enhanced. Buoyancy extension of the k-ε model also leads to less vertical mixing in cases with strong stratification. When the stratification increases, buoyancy-extension becomes larger influence. The turbulent Prandtl number effects have large impact on the transport of heat and the development of the flow. Two different formulae which express the turbulent Prandtl effects have been tested. For unstably stratified flows, the rapid mixing and three-dimensionality of the flow can in fact be computed using a k-ε model when buoyancy-extended is employed. The turbulent heat transfer and thus turbulent production in unstable stratified flows depends strongly upon the turbulent Prandtl number effect. The main conclusions are: Stable stratified flows should be computed with a buoyancy-extended low-Reynolds k-ε model; Unstable stratified flows should be computed with a buoyancy-extended standard k-ε model; The turbulent Prandtl number effects should be included in the computations; Buoyancy-extension has lead to more correct description of the physics for all of the investigated flows. 78 refs., 128 figs., 17 tabs

  15. Unit Stratified Sampling as a Tool for Approximation of Stochastic Optimization Problems

    Czech Academy of Sciences Publication Activity Database

    Šmíd, Martin

    2012-01-01

    Roč. 19, č. 30 (2012), s. 153-169 ISSN 1212-074X R&D Projects: GA ČR GAP402/11/0150; GA ČR GAP402/10/0956; GA ČR GA402/09/0965 Institutional research plan: CEZ:AV0Z10750506 Institutional support: RVO:67985556 Keywords : Stochastic programming * approximation * stratified sampling Subject RIV: BB - Applied Statistics, Operational Research http://library.utia.cas.cz/separaty/2013/E/smid-unit stratified sampling as a tool for approximation of stochastic optimization problems.pdf

  16. Experimental observation of the stratified electrothermal instability on aluminum with thickness greater than a skin depth

    Science.gov (United States)

    Hutchinson, T. M.; Awe, T. J.; Bauer, B. S.; Yates, K. C.; Yu, E. P.; Yelton, W. G.; Fuelling, S.

    2018-05-01

    A direct observation of the stratified electrothermal instability on the surface of thick metal is reported. Aluminum rods coated with 70 μ m Parylene-N were driven to 1 MA in 100 ns , with the metal thicker than the skin depth. The dielectric coating suppressed plasma formation, enabling persistent observation of discrete azimuthally correlated stratified thermal perturbations perpendicular to the current whose wave numbers, k , grew exponentially with rate γ (k ) =0.06 n s-1-(0.4 n s-1μ m2ra d-2 ) k2 in ˜1 g /c m3 , ˜7000 K aluminum.

  17. Stereo imaging and random array stratified imaging for cargo radiation inspecting

    International Nuclear Information System (INIS)

    Wang Jingjin; Zeng Yu

    2003-01-01

    This paper presents a Stereo Imaging and Random Array Stratified Imaging for cargo container radiation Inspecting. By using dual-line vertical detector array scan, a stereo image of inspected cargo can be obtained and watched with virtual reality view. The random detector array has only one-row of detectors but distributed in a certain horizontal dimension randomly. To scan a cargo container with this random array detector, a 'defocused' image is obtained. By using 'anti-random focusing', one layer of the image can be focused on the background of all defocused images from other layers. A stratified X-ray image of overlapped bike wheels is presented

  18. Experimental Observation of the Stratified Electrothermal Instability on Aluminum with Thickness Greater than a Skin Depth

    Energy Technology Data Exchange (ETDEWEB)

    Hutchinson, Trevor M. [Univ. of Nevada, Reno, NV (United States); Hutchinson, Trevor M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Awe, Thomas James [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bauer, Bruno S. [Univ. of Nevada, Reno, NV (United States); Yates, Kevin [Univ. of New Mexico, Albuquerque, NM (United States); Yu, Edmund p. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Yelton, William G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Fuelling, Stephan [Univ. of Nevada, Reno, NV (United States)

    2017-07-01

    The first direct observation of the stratified electrothermal instability on the surface of thick metal is reported. Aluminum rods coated with 70 μm Parylene-N were driven to 1 MA in approximately 100 ns, with the metal thicker than the skin depth. The dielectric coating suppressed plasma formation, enabling persistent observation of discrete azimuthally-correlated stratified structures perpendicular to the current. Strata amplitudes grow rapidly, while their Fourier spectrum shifts toward longer wavelength. Assuming blackbody emission, radiometric calculations indicate strata are temperature perturbations that grow exponentially with rate γ = 0.04 ns -1 in 3000- 10,000 K aluminum.

  19. An analysis direct-contact condensation in horizontal cocurrent stratified flow of steam and cold water

    International Nuclear Information System (INIS)

    Lee, Suk Ho; Kim, Hho Jung

    1992-01-01

    The physical benchmark problem on the direct-contact condensation under the horizontal cocurrent stratified flow was analyzed using the RELAP5/MOD2 and /MOD3 one-dimensional model. Analysis was performed for the Northwestern experiments, which involved condensing steam/water flow in a rectangular channel. The study showed that the RELAP5 interfacial heat transfer model, under the horizontal stratified flow regime, predicted the condensation rate well though the interfacial heat transfer area was underpredicted. However, some discrepancies in water layer thickness and local heat transfer coefficient with experimental results were found especially when there is a wavy interface, and those were satisfied only within the range. (Author)

  20. Effects of a random spatial variation of the plasma density on the mode conversion in cold, unmagnetized, and stratified plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Jung Yu, Dae [School of Space Research, Kyung Hee University, Yongin 446-701 (Korea, Republic of); Kim, Kihong [Department of Energy Systems Research, Ajou University, Suwon 443-749 (Korea, Republic of)

    2013-12-15

    We study the effects of a random spatial variation of the plasma density on the mode conversion of electromagnetic waves into electrostatic oscillations in cold, unmagnetized, and stratified plasmas. Using the invariant imbedding method, we calculate precisely the electromagnetic field distribution and the mode conversion coefficient, which is defined to be the fraction of the incident wave power converted into electrostatic oscillations, for the configuration where a numerically generated random density variation is added to the background linear density profile. We repeat similar calculations for a large number of random configurations and take an average of the results. We obtain a peculiar nonmonotonic dependence of the mode conversion coefficient on the strength of randomness. As the disorder increases from zero, the maximum value of the mode conversion coefficient decreases initially, then increases to a maximum, and finally decreases towards zero. The range of the incident angle in which mode conversion occurs increases monotonically as the disorder increases. We present numerical results suggesting that the decrease of mode conversion mainly results from the increased reflection due to the Anderson localization effect originating from disorder, whereas the increase of mode conversion of the intermediate disorder regime comes from the appearance of many resonance points and the enhanced tunneling between the resonance points and the cutoff point. We also find a very large local enhancement of the magnetic field intensity for particular random configurations. In order to obtain high mode conversion efficiency, it is desirable to restrict the randomness close to the resonance region.

  1. Effects of a random spatial variation of the plasma density on the mode conversion in cold, unmagnetized, and stratified plasmas

    International Nuclear Information System (INIS)

    Jung Yu, Dae; Kim, Kihong

    2013-01-01

    We study the effects of a random spatial variation of the plasma density on the mode conversion of electromagnetic waves into electrostatic oscillations in cold, unmagnetized, and stratified plasmas. Using the invariant imbedding method, we calculate precisely the electromagnetic field distribution and the mode conversion coefficient, which is defined to be the fraction of the incident wave power converted into electrostatic oscillations, for the configuration where a numerically generated random density variation is added to the background linear density profile. We repeat similar calculations for a large number of random configurations and take an average of the results. We obtain a peculiar nonmonotonic dependence of the mode conversion coefficient on the strength of randomness. As the disorder increases from zero, the maximum value of the mode conversion coefficient decreases initially, then increases to a maximum, and finally decreases towards zero. The range of the incident angle in which mode conversion occurs increases monotonically as the disorder increases. We present numerical results suggesting that the decrease of mode conversion mainly results from the increased reflection due to the Anderson localization effect originating from disorder, whereas the increase of mode conversion of the intermediate disorder regime comes from the appearance of many resonance points and the enhanced tunneling between the resonance points and the cutoff point. We also find a very large local enhancement of the magnetic field intensity for particular random configurations. In order to obtain high mode conversion efficiency, it is desirable to restrict the randomness close to the resonance region

  2. Axisymmetric annular curtain stability

    International Nuclear Information System (INIS)

    Ahmed, Zahir U; Khayat, Roger E; Maissa, Philippe; Mathis, Christian

    2012-01-01

    A temporal stability analysis was carried out to investigate the stability of an axially moving viscous annular liquid jet subject to axisymmetric disturbances in surrounding co-flowing viscous gas media. We investigated in this study the effects of inertia, surface tension, the gas-to-liquid density ratio, the inner-to-outer radius ratio and the gas-to-liquid viscosity ratio on the stability of the jet. With an increase in inertia, the growth rate of the unstable disturbances is found to increase. The dominant (or most unstable) wavenumber decreases with increasing Reynolds number for larger values of the gas-to-liquid viscosity ratio. However, an opposite tendency for the most unstable wavenumber is predicted for small viscosity ratio in the same inertia range. The surrounding gas density, in the presence of viscosity, always reduces the growth rate, hence stabilizing the flow. There exists a critical value of the density ratio above which the flow becomes stable for very small viscosity ratio, whereas for large viscosity ratio, no stable flow appears in the same range of the density ratio. The curvature has a significant destabilizing effect on the thin annular jet, whereas for a relatively thick jet, the maximum growth rate decreases as the inner radius increases, irrespective of the surrounding gas viscosity. The degree of instability increases with Weber number for a relatively large viscosity ratio. In contrast, for small viscosity ratio, the growth rate exhibits a dramatic dependence on the surface tension. There is a small Weber number range, which depends on the viscosity ratio, where the flow is stable. The viscosity ratio always stabilizes the flow. However, the dominant wavenumber increases with increasing viscosity ratio. The range of unstable wavenumbers is affected only by the curvature effect. (paper)

  3. Risk of falling among hospitalized patients with high modified Morse scores could be further Stratified

    Directory of Open Access Journals (Sweden)

    Irina Gringauz

    2017-11-01

    Full Text Available Abstract Background Falls during hospitalization harbor both clinical and financial outcomes. The modified Morse fall scale [MMFS] is widely used for an in-hospital risk-of-fall assessment. Nevertheless, the majority of patients at risk of falling, i.e. with high MMFS, do not fall. The aim of this study was to ascertain our study hypothesis that certain patients' characteristics (e.g. serum electrolytes, usage of a walking device etc. could further stratify the risk of falls among hospitalized patients with MMFS. Methods This was a retrospective cohort analysis of adult patients hospitalized in Internal Medicine departments. Results The final cohort included 428 patients aged 76.8±14.0 years. All patients had high (9 or more MMFS upon admission, and their mean MMFS was 16.2±6.1. A group of 139 (32.5% patients who fell during their hospitalization was compared with a control group of 289 (67.5% patients who did not fall. The fallers had higher MMFS, a higher prevalence of mild dependence, and a greater use of a cane or no walking device. Regression analysis showed the following patients' characteristics to be independently associated with an increased risk of falling: mild dependence (OR=3.99, 95% CI 1.97-8.08; p<0.0001, treatment by anti-epileptics (OR=3.9, 95% CI 1.36-11.18; p=0.011, treatment by hypoglycemic agents (OR=2.64, 95% CI 1.08-6.45; p= 0.033, and hypothyroidism (OR=3.66, 05%CI 1.62-8.30; p=0.002. In contrast to their role in the MMFS, the use of a walker or a wheelchair was found to decrease the risk of falling (OR=0.3, 95% CI 0.13-0.69; p=0.005 and OR=0.25, 95% CI 0.11-0.59; p= 0.002. Conclusions Further risk stratification of hospitalized patients, already known to have a high MMFS, which would take into account the characteristics pointed out in this study, should be attained.

  4. The stably stratified internal boundary layer for steady and diurnally varying offshore flow

    Science.gov (United States)

    Garratt, J. R.

    1987-03-01

    A two-dimensional numerical mesoscale model is used to investigate the internal structure and growth of the stably stratified internal boundary layer (IBL) beneath warm, continental air flowing over a cooler sea. Two situations are studied — steady-state and diurnally varying offshore flow. In the steady-state case, vertical profiles of mean quantities and eddy diffusion coefficients ( K) within the IBL show small, but significant, changes with increasing distance from the coast. The top of the IBL is well defined, with large vertical gradients within the layer and a maximum in the coast-normal wind component near the top. Well away from the coast, turbulence, identified by non-zero K, decreases to insignificant levels near the top of the IBL; the IBL itself is characterised by a critical value of the layer-flux Richardson number equal to 0.18. The overall behaviour of the mean profiles is similar to that found in the horizontally homogeneous stable boundary layer over land. A simple physical model is used to relate the depth of the layer h to several relevant physical parameters viz., x, the distance from the coast and U, the large-scale wind (both normal to the coastline) and gδθ/θ, Δθ being the temperature difference between continental mixed-layer air and sea surface, θ is the mean potential temperature and g is the acceleration due to gravity. Excellent agreement with the numerical results is found, with h = 0.014 x 1/2 U ( gδθ/θ)-1/2. In the diurnally varying case, the mean profiles within the IBL show only small differences from the steady-state case, although diurnal variations, particularly in the wind maximum, are evident within a few hundred kilometres of the coast. A mesoscale circulation normal to the coast, and superimposed upon the mean offshore flow, develops seawards of the coastline with maximum vertical velocities about sunset, of depth about 2 km and horizontal scale ≈ 500 km. The circulation is related to the advection, and

  5. E25 stratified torch ignition engine performance, CO_2 emission and combustion analysis

    International Nuclear Information System (INIS)

    Rodrigues Filho, Fernando Antonio; Moreira, Thiago Augusto Araujo; Valle, Ramon Molina; Baêta, José Guilherme Coelho; Pontoppidan, Michael; Teixeira, Alysson Fernandes

    2016-01-01

    Highlights: • A torch ignition engine prototype was built and tested. • Significant reduction of BSFC was achieved due to the use of the torch ignition system. • Low cyclic variability characterized the lean combustion process of the torch ignition engine prototype. • The torch ignition system allowed an average reduction of 8.21% at the CO_2 specific emissions. - Abstract: Vehicular emissions significantly increase atmospheric air pollution and the greenhouse effect. This fact associated with the fast growth of the global motor vehicle fleet demands technological solutions from the scientific community in order to achieve a decrease in fuel consumption and CO_2 emission, especially of fossil fuels to comply with future legislation. To meet this goal, a prototype stratified torch ignition engine was designed from a commercial baseline engine. In this system, the combustion starts in a pre-combustion chamber where the pressure increase pushes the combustion jet flames through a calibrated nozzle to be precisely targeted into the main chamber. These combustion jet flames are endowed with high thermal and kinetic energy being able to promote a stable lean combustion process. The high kinetic and thermal energy of the combustion jet flame results from the load stratification. This is carried out through direct fuel injection in the pre-combustion chamber by means of a prototype gasoline direct injector (GDI) developed for low fuel flow rate. During the compression stroke, lean mixture coming from the main chamber is forced into the pre-combustion chamber and, a few degrees before the spark timing, fuel is injected into the pre-combustion chamber aiming at forming a slightly rich mixture cloud around the spark plug which is suitable for the ignition and kernel development. The performance of the torch ignition engine running with E25 is presented for different mixture stratification levels, engine speed and load. The performance data such as combustion phasing

  6. Gender Stratified Monopoly: Why Do I Earn Less and Pay More?

    Science.gov (United States)

    Smith, Stacy L.

    2017-01-01

    A modified version of Monopoly has long been used as a simulation exercise to teach inequality. Versions of Modified Monopoly (MM) have touched on minority status relative to inequality but without an exploration of the complex interaction between minority status and class. This article introduces Gender Stratified Monopoly (GSM), an adaptation…

  7. Modeling the Conducting Stably-Stratified Layer of the Earth's Core

    Science.gov (United States)

    Petitdemange, L.; Philidet, J.; Gissinger, C.

    2017-12-01

    Observations of the Earth magnetic field as well as recent theoretical works tend to show that the Earth's outer liquid core is mostly comprised of a convective zone in which the Earth's magnetic field is generated - likely by dynamo action -, but also features a thin, stably stratified layer at the top of the core.We carry out direct numerical simulations by modeling this thin layer as an axisymmetric spherical Couette flow for a stably stratified fluid embedded in a dipolar magnetic field. The dynamo region is modeled by a conducting inner core rotating slightly faster than the insulating mantle due to magnetic torques acting on it, such that a weak differential rotation (low Rossby limit) can develop in the stably stratified layer.In the case of a non-stratified fluid, the combined action of the differential rotation and the magnetic field leads to the well known regime of `super-rotation', in which the fluid rotates faster than the inner core. Whereas in the classical case, this super-rotation is known to vanish in the magnetostrophic limit, we show here that the fluid stratification significantly extends the magnitude of the super-rotation, keeping this phenomenon relevant for the Earth core. Finally, we study how the shear layers generated by this new state might give birth to magnetohydrodynamic instabilities or waves impacting the secular variations or jerks of the Earth's magnetic field.

  8. Modification of Measures of Acute Kidney Injury to Risk Stratify Combat Casualties

    Science.gov (United States)

    2017-08-26

    REPORT TYPE 08/26/2017 Poster 4. TJTLE AND SUBTITLE t\\.1odification of l’vfeasures,of Acute Kidney Injury to Risk Stratify Cotnbat Casualties 6...profiles and potential future conflicts , identifying acute kidney injury (AKI) early can help us determine the need for rapidity of evacuation

  9. Dominance of a clonal green sulfur bacterial population in a stratified lake

    DEFF Research Database (Denmark)

    Gregersen, Lea H; Habicht, Kirsten S; Peduzzi, Sandro

    2009-01-01

    surveys using FISH cell counting and population multilocus sequence typing [clone library sequence analysis of the small subunit (SSU) rRNA locus and two loci involved in photosynthesis in GSB: fmoA and csmCA]. All bacterial populations clearly stratified according to water column chemistry. The GSB...

  10. Measures to assess the prognostic ability of the stratified Cox proportional hazards model

    DEFF Research Database (Denmark)

    (Tybjaerg-Hansen, A.) The Fibrinogen Studies Collaboration.The Copenhagen City Heart Study; Tybjærg-Hansen, Anne

    2009-01-01

    Many measures have been proposed to summarize the prognostic ability of the Cox proportional hazards (CPH) survival model, although none is universally accepted for general use. By contrast, little work has been done to summarize the prognostic ability of the stratified CPH model; such measures...

  11. Analysing stratified medicine business models and value systems: innovation-regulation interactions.

    Science.gov (United States)

    Mittra, James; Tait, Joyce

    2012-09-15

    Stratified medicine offers both opportunities and challenges to the conventional business models that drive pharmaceutical R&D. Given the increasingly unsustainable blockbuster model of drug development, due in part to maturing product pipelines, alongside increasing demands from regulators, healthcare providers and patients for higher standards of safety, efficacy and cost-effectiveness of new therapies, stratified medicine promises a range of benefits to pharmaceutical and diagnostic firms as well as healthcare providers and patients. However, the transition from 'blockbusters' to what might now be termed 'niche-busters' will require the adoption of new, innovative business models, the identification of different and perhaps novel types of value along the R&D pathway, and a smarter approach to regulation to facilitate innovation in this area. In this paper we apply the Innogen Centre's interdisciplinary ALSIS methodology, which we have developed for the analysis of life science innovation systems in contexts where the value creation process is lengthy, expensive and highly uncertain, to this emerging field of stratified medicine. In doing so, we consider the complex collaboration, timing, coordination and regulatory interactions that shape business models, value chains and value systems relevant to stratified medicine. More specifically, we explore in some depth two convergence models for co-development of a therapy and diagnostic before market authorisation, highlighting the regulatory requirements and policy initiatives within the broader value system environment that have a key role in determining the probable success and sustainability of these models. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Experimental investigation on isothermal stratified flow mixing in a horizontal T-junction

    Energy Technology Data Exchange (ETDEWEB)

    Isaev, Alexander; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. fuer Kernenergetik und Energiesysteme (IKE)

    2016-10-15

    Turbulent and stratified flows can lead to thermal fatigue in piping systems of nuclear power plants (NPP). Such flows can be investigated in the University of Stuttgart Fluid-Structure-Interaction (FSI) facility with a T-Junction at thermal conditions with temperature differences of up to 255 K and at pressures of maximum 75 bars.

  13. Mathematical modeling of turbulent stratified flows. Application of liquid metal fast breeders

    Energy Technology Data Exchange (ETDEWEB)

    Villand, M; Grand, D [CEA-Service des Transferts Thermiques, Grenoble (France)

    1983-07-01

    Mathematical model of turbulent stratified flow was proposed under the following assumptions: Newtonian fluid; incompressible fluid; coupling between temperature and momentum fields according to Boussinesq approximation; two-dimensional invariance for translation or rotation; coordinates cartesian or curvilinear. Solutions obtained by the proposed method are presented.

  14. The Fokker-Planck equation for ray dispersion in gyrotropic stratified media

    NARCIS (Netherlands)

    Golynski, S.M.

    1984-01-01

    The Hamilton equations of geometrical optics determine the rays of the relevant wave field in the short wavelength. We give a systematic derivation of the Fokker-Planck equation for the joint probability density of the position and unit direction vector of rays propagating in a gyrotropic stratified

  15. Design and simulation of stratified probability digital receiver with application to the multipath communication

    Science.gov (United States)

    Deal, J. H.

    1975-01-01

    One approach to the problem of simplifying complex nonlinear filtering algorithms is through using stratified probability approximations where the continuous probability density functions of certain random variables are represented by discrete mass approximations. This technique is developed in this paper and used to simplify the filtering algorithms developed for the optimum receiver for signals corrupted by both additive and multiplicative noise.

  16. Computational Fluid Dynamics model of stratified atmospheric boundary-layer flow

    DEFF Research Database (Denmark)

    Koblitz, Tilman; Bechmann, Andreas; Sogachev, Andrey

    2015-01-01

    For wind resource assessment, the wind industry is increasingly relying on computational fluid dynamics models of the neutrally stratified surface-layer. So far, physical processes that are important to the whole atmospheric boundary-layer, such as the Coriolis effect, buoyancy forces and heat...

  17. Internal wave patterns in enclosed density-stratified and rotating fluids

    NARCIS (Netherlands)

    Manders, A.M.A.

    2003-01-01

    Stratified fluids support internal waves, which propagate obliquely through the fluid. The angle with respectto the stratification direction is contrained: it is purely determined by the wave frequency and the strength of the density stratification (internal gravity waves) or the rotation rate

  18. Seasonal cyclogenesis and the role of near-surface stratified layer in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Sarma, M.S.S.; Tilvi, V.

    The role of the near-surface stratified layer developed due to the spread of low salinity waters under the influence of freshwater influx on the cyclogenesis over the Bay of Bengal is addressed. The seasonal variation of the Effective Oceanic Layer...

  19. A review of recent developments on turbulent entrainment in stratified flows

    International Nuclear Information System (INIS)

    Cotel, Aline J

    2010-01-01

    Stratified interfaces are present in many geophysical flow situations, and transport across such an interface is an essential factor for correctly evaluating the physical processes taking place at many spatial and temporal scales in such flows. In order to accurately evaluate vertical and lateral transport occurring when a turbulent flow impinges on a stratified interface, the turbulent entrainment and vorticity generation mechanisms near the interface must be understood and quantified. Laboratory experiments were performed for three flow configurations: a vertical thermal, a sloping gravity current and a vertical turbulent jet with various tilt angles and precession speeds. All three flows impinged on an interface separating a two-layer stably stratified environment. The entrainment rate is quantified for each flow using laser-induced fluorescence and compared to predictions of Cotel and Breidenthal (1997 Appl. Sci. Res. 57 349-66). The possible applications of transport across stratified interfaces include the contribution of hydrothermal plumes to the global ocean energy budget, turbidity currents on the ocean floor, the design of lake de-stratification systems, modeling gas leaks from storage reservoirs, weather forecasting and global climate change.

  20. Low-frequency linear waves and instabilities in uniform and stratified plasmas: the role of kinetic effects

    Directory of Open Access Journals (Sweden)

    K. M. Ferrière

    2004-01-01

    Full Text Available We review the basic approximations underlying magnetohydrodynamic (MHD theory, with special emphasis on the closure approximations, i.e. the approximations used in any fluid approach to close the hierarchy of moment equations. We then present the main closure models that have been constructed for collisionless plasmas in the large-scale regime, and we describe our own mixed MHD-kinetic model, which is designed to study low-frequency linear waves and instabilities in collisionless plasmas. We write down the full dispersion relation in a new, general form, which gathers all the specific features of our MHD-kinetic model into four polytropic indices, and which can be applied to standard adiabatic MHD and to double-adiabatic MHD through a simple change in the expressions of the polytropic indices. We study the mode solutions and the stability properties of the full dispersion relation in each of these three theories, first in the case of a uniform plasma, and then in the case of a stratified plasma. In both cases, we show how the results are affected by the collisionless nature of the plasma.

  1. Before Stabilization

    DEFF Research Database (Denmark)

    Plesner, Ursula; Horst, Maja

    2013-01-01

    of the communication about innovations in information and communication technology (ICT), and to contribute to an understanding of how different visions promise particular future configurations of workflows, communication processes, politics, economic models and social relations. Hereby, the paper adds...... to the literature on the relationship between ICTs and organizing, but with a distinct focus on innovation communication and distributed innovation processes taking place before ICTs are stabilized, issues which cannot be captured by studies of diffusion and adaptation of new ICTs within single organizations....

  2. General Practitioners' and patients' perceptions towards stratified care: a theory informed investigation.

    Science.gov (United States)

    Saunders, Benjamin; Bartlam, Bernadette; Foster, Nadine E; Hill, Jonathan C; Cooper, Vince; Protheroe, Joanne

    2016-08-31

    Stratified primary care involves changing General Practitioners' (GPs) clinical behaviour in treating patients, away from the current stepped care approach to instead identifying early treatment options that are matched to patients' risk of persistent disabling pain. This article explores the perspectives of UK-based GPs and patients about a prognostic stratified care model being developed for patients with the five most common primary care musculoskeletal pain presentations. The focus was on views about acceptability, and anticipated barriers and facilitators to the use of stratified care in routine practice. Four focus groups and six semi-structured telephone interviews were conducted with GPs (n = 23), and three focus groups with patients (n = 20). Data were analysed thematically; and identified themes examined in relation to the Theoretical Domains Framework (TDF), which facilitates comprehensive identification of behaviour change determinants. A critical approach was taken in using the TDF, examining the nuanced interrelationships between theoretical domains. Four key themes were identified: Acceptability of clinical decision-making guided by stratified care; impact on the therapeutic relationship; embedding a prognostic approach within a biomedical model; and practical issues in using stratified care. Whilst within each theme specific findings are reported, common across themes was the identified relationships between the theoretical domains of knowledge, skills, professional role and identity, environmental context and resources, and goals. Through analysis of these identified relationships it was found that, for GPs and patients to perceive stratified care as being acceptable, it must be seen to enhance GPs' knowledge and skills, not undermine GPs' and patients' respective identities and be integrated within the environmental context of the consultation with minimal disruption. Findings highlight the importance of taking into account the context of

  3. Airplane radiation dose decrease during a strong Forbush decrease

    Czech Academy of Sciences Publication Activity Database

    Spurný, František; Kudela, K.; Dachev, T.

    2004-01-01

    Roč. 2, S05001 (2004), s. 1-4 ISSN 1542-7390 Grant - others:EC project(XE) FIGM-CT2000-00068 Institutional research plan: CEZ:AV0Z1048901 Keywords : airplane dose * Forbush decrease * cosmic rays Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  4. Mixed Convection Flow along a Stretching Cylinder in a Thermally Stratified Medium

    Directory of Open Access Journals (Sweden)

    Swati Mukhopadhyay

    2012-01-01

    Full Text Available An analysis for the axisymmetric laminar boundary layer mixed convection flow of a viscous and incompressible fluid towards a stretching cylinder immersed in a thermally stratified medium is presented in this paper. Similarity transformation is employed to convert the governing partial differential equations into highly nonlinear ordinary differential equations. Numerical solutions of these equations are obtained by a shooting method. It is found that the heat transfer rate at the surface is lower for flow in a thermally stratified medium compared to that of an unstratified medium. Moreover, both the skin friction coefficient and the heat transfer rate at the surface are larger for a cylinder compared to that for a flat plate.

  5. Doubly stratified mixed convection flow of Maxwell nanofluid with heat generation/absorption

    Energy Technology Data Exchange (ETDEWEB)

    Abbasi, F.M., E-mail: abbasisarkar@gmail.com [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Shehzad, S.A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Hayat, T. [Department of Mathematics, Quaid-i-Azam University, 45320, Islamabad 44000 (Pakistan); NAAM Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Ahmad, B. [NAAM Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2016-04-15

    Magnetohydrodynamic (MHD) doubly stratified flow of Maxwell nanofluid in presence of mixed convection is analyzed in this article. Effects of thermophoresis, Brownian motion and heat generation/absorption are present. The flow is induced due to linear stretching of sheet. Mathematical formulation is made under boundary layer approach. Expressions of velocity, temperature and nanoparticles concentration are developed. The obtained results are plotted and discussed to examine the variations in temperature and nanoparticles concentration due to different physical parameters. Numerical computations are made to obtain the values of local Nusselt and Sherwood numbers. Impact of sundry parameters on the flow quantities is analyzed graphically. - Highlights: • Double stratified flow of Maxwell nanofluid with mixed convection is modeled. • Thermophoresis and Brownian motion effects are encountered. • Computations are made to obtain the solution expressions. • Numerical values of local Nusselt and Sherwood numbers are computed and examined.

  6. Estimation of Finite Population Mean in Multivariate Stratified Sampling under Cost Function Using Goal Programming

    Directory of Open Access Journals (Sweden)

    Atta Ullah

    2014-01-01

    Full Text Available In practical utilization of stratified random sampling scheme, the investigator meets a problem to select a sample that maximizes the precision of a finite population mean under cost constraint. An allocation of sample size becomes complicated when more than one characteristic is observed from each selected unit in a sample. In many real life situations, a linear cost function of a sample size nh is not a good approximation to actual cost of sample survey when traveling cost between selected units in a stratum is significant. In this paper, sample allocation problem in multivariate stratified random sampling with proposed cost function is formulated in integer nonlinear multiobjective mathematical programming. A solution procedure is proposed using extended lexicographic goal programming approach. A numerical example is presented to illustrate the computational details and to compare the efficiency of proposed compromise allocation.

  7. Experimental and numerical investigation of stratified gas-liquid flow in inclined circular pipes

    International Nuclear Information System (INIS)

    Faccini, J.L.H.; Sampaio, P.A.B. de; Botelho, M.H.D.S.; Cunha, M.V.; Cunha Filho, J.S.; Su, J.

    2012-01-01

    In this paper, a stratified gas-liquid flow is experimentally and numerically investigated. Two measurement techniques, namely an ultrasonic technique and a visualization technique, are applied on an inclined circular test section using a fast single transducer pulse-echo technique and a high-speed camera. A numerical model is employed to simulate the stratified gas-liquid flow, formed by a system of non-linear differential equations consisting of the Reynolds averaged Navier-Stokes equations with the κ-ω turbulence model. The test section used in this work is comprised mainly of a transparent circular pipe with inner diameter 1 inch, and inclination angles varying from -2.5 to -10.0 degrees. Numerical solutions are obtained for the liquid height as a function of inclination angles, and compared with our own experimental data. (author)

  8. Analysis of natural convection heat transfer and flows in internally heated stratified liquid pools

    International Nuclear Information System (INIS)

    Gubaidullin, A.A. Jr.; Dinh, T.N.; Sehgal, B.R.

    1999-01-01

    In this paper, natural convection flows and heat transfer in a liquid pool, with two superposed immiscible fluid layers, are analyzed. The objective of the study is to examine the effect of interfacial hydrodynamics and to develop a method which enables energy splitting to be evaluated in a stratified liquid pool. The thermal convection, with and without an internal heat source, in a rectangular cavity with different pairs of fluids was numerically simulated by a CFD code FLOW-3D. It was found that the code performs very well for prediction of heat transfer coefficients for different conditions. The hydrodynamic coupling between immiscible layers was found to have minor, if any, impact on the natural convection heat transfer for the conditions examined. Calculated results were used to develop, and validate, a new correlation for energy splitting and for heat transfer in stratified liquid pools

  9. Numerical simulation of stratified shear flow using a higher order Taylor series expansion method

    Energy Technology Data Exchange (ETDEWEB)

    Iwashige, Kengo; Ikeda, Takashi [Hitachi, Ltd. (Japan)

    1995-09-01

    A higher order Taylor series expansion method is applied to two-dimensional numerical simulation of stratified shear flow. In the present study, central difference scheme-like method is adopted for an even expansion order, and upwind difference scheme-like method is adopted for an odd order, and the expansion order is variable. To evaluate the effects of expansion order upon the numerical results, a stratified shear flow test in a rectangular channel (Reynolds number = 1.7x10{sup 4}) is carried out, and the numerical velocity and temperature fields are compared with experimental results measured by laser Doppler velocimetry thermocouples. The results confirm that the higher and odd order methods can simulate mean velocity distributions, root-mean-square velocity fluctuations, Reynolds stress, temperature distributions, and root-mean-square temperature fluctuations.

  10. Turbulent transport of passive scalar behind line sources in an unstably stratified open channel flow

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chun-Ho [The Hong Kong Polytechnic University, Kowloon (Hong Kong). Department of Building and Real Estate; Leung, Dennis Y.C. [The University of Hong Kong (Hong Kong). Department of Mechanical Engineering

    2006-11-15

    This study employs a direct numerical simulation (DNS) technique to study the flow, turbulence structure, and passive scalar plume transport behind line sources in an unstably stratified open channel flow. The scalar transport behaviors for five emission heights (z{sub s}=0, 0.25H, 0.5H, 0.75H, and H, where H is the channel height) at a Reynolds number of 3000, a Prandtl number and a Schmidt number of 0.72, and a Richardson number of -0.2 are investigated. The vertically meandering mean plume heights and dispersion coefficients calculated by the current DNS model agree well with laboratory results and field measurements in literature. It is found that the plume meandering is due to the movement of the positive and negative vertical turbulent scalar fluxes above and below the mean plume heights, respectively. These findings help explaining the plume meandering mechanism in the unstably stratified atmospheric boundary layer. (author)

  11. Quantum image pseudocolor coding based on the density-stratified method

    Science.gov (United States)

    Jiang, Nan; Wu, Wenya; Wang, Luo; Zhao, Na

    2015-05-01

    Pseudocolor processing is a branch of image enhancement. It dyes grayscale images to color images to make the images more beautiful or to highlight some parts on the images. This paper proposes a quantum image pseudocolor coding scheme based on the density-stratified method which defines a colormap and changes the density value from gray to color parallel according to the colormap. Firstly, two data structures: quantum image GQIR and quantum colormap QCR are reviewed or proposed. Then, the quantum density-stratified algorithm is presented. Based on them, the quantum realization in the form of circuits is given. The main advantages of the quantum version for pseudocolor processing over the classical approach are that it needs less memory and can speed up the computation. Two kinds of examples help us to describe the scheme further. Finally, the future work are analyzed.

  12. The New Rich and Their Unplanned Births: Stratified Reproduction under China's Birth-planning Policy.

    Science.gov (United States)

    Shi, Lihong

    2017-12-01

    This article explores the creation and ramifications of a stratified reproductive system under China's state control of reproduction. Within this system, an emerging group of "new rich" are able to circumvent birth regulations and have unplanned births because of their financial capabilities and social networks. While China's birth-planning policy is meant to be enforced equally for all couples, the unequal access to wealth and bureaucratic power as a result of China's widening social polarization has created disparate reproductive rights and experiences. This article identifies three ways in which reproductive privileges are created. It further explores how a stratified reproductive system under state population control reinforces social polarization. While many socially marginalized couples are unable to register their unplanned children for citizenship status and social benefits, the new rich are able to legitimate their births and transfer their privilege and status to their children, thus reproducing a new generation of elites. © 2016 by the American Anthropological Association.

  13. The effect of sediments on turbulent plume dynamics in a stratified fluid

    Science.gov (United States)

    Stenberg, Erik; Ezhova, Ekaterina; Brandt, Luca

    2017-11-01

    We report large eddy simulation results of sediment-loaded turbulent plumes in a stratified fluid. The configuration, where the plume is discharged from a round source, provides an idealized model of subglacial discharge from a submarine tidewater glacier and is a starting point for understanding the effect of sediments on the dynamics of the rising plume. The transport of sediments is modeled by means of an advection-diffusion equation where sediment settling velocity is taken into account. We initially follow the experimental setup of Sutherland (Phys. Rev. Fluids, 2016), considering uniformly stratified ambients and further extend the work to pycnocline-type stratifications typical of Greenland fjords. Apart from examining the rise height, radial spread and intrusion of the rising plume, we gain further insights of the plume dynamics by extracting turbulent characteristics and the distribution of the sediments inside the plume.

  14. Emerging Techniques in Stratified Designs and Continuous Gradients for Tissue Engineering of Interfaces

    Science.gov (United States)

    Dormer, Nathan H.; Berkland, Cory J.; Detamore, Michael S.

    2013-01-01

    Interfacial tissue engineering is an emerging branch of regenerative medicine, where engineers are faced with developing methods for the repair of one or many functional tissue systems simultaneously. Early and recent solutions for complex tissue formation have utilized stratified designs, where scaffold formulations are segregated into two or more layers, with discrete changes in physical or chemical properties, mimicking a corresponding number of interfacing tissue types. This method has brought forth promising results, along with a myriad of regenerative techniques. The latest designs, however, are employing “continuous gradients” in properties, where there is no discrete segregation between scaffold layers. This review compares the methods and applications of recent stratified approaches to emerging continuously graded methods. PMID:20411333

  15. Scattering by multiple parallel radially stratified infinite cylinders buried in a lossy half space.

    Science.gov (United States)

    Lee, Siu-Chun

    2013-07-01

    The theoretical solution for scattering by an arbitrary configuration of closely spaced parallel infinite cylinders buried in a lossy half space is presented in this paper. The refractive index and permeability of the half space and cylinders are complex in general. Each cylinder is radially stratified with a distinct complex refractive index and permeability. The incident radiation is an arbitrarily polarized plane wave propagating in the plane normal to the axes of the cylinders. Analytic solutions are derived for the electric and magnetic fields and the Poynting vector of backscattered radiation emerging from the half space. Numerical examples are presented to illustrate the application of the scattering solution to calculate backscattering from a lossy half space containing multiple homogeneous and radially stratified cylinders at various depths and different angles of incidence.

  16. 3D elastic inversion of vertical seismic profiles in horizontally stratified media; Inversion elastique 3D de profils sismiques verticaux en milieux stratifies horizontalement

    Energy Technology Data Exchange (ETDEWEB)

    Petit, J.L.

    1997-07-21

    This thesis is devoted to the inversion of VSP (vertical seismic profile) seismic data in order to determine the elastic properties of horizontally stratified media. The VSP records are computed using the full wave elastic modelling in isotropic and transversely isotropic media using Hankel transform, a finite difference scheme and an inverse Hankel transform algorithm, and the propagation equations are determined and numerically solved; the importance of considering a 3D wave propagation model instead of a 1 D one is emphasized. The theoretical VSP inverse problem is then considered, with the seismic waveform inversion set as a least-squares problem, consisting in recovering the distribution of physical parameters which minimize the misfit between calculated and observed VSP. The corresponding problem requires the knowledge of the source function

  17. Radion cosmology and stabilization

    International Nuclear Information System (INIS)

    Chakraborty, Sumanta; SenGupta, Soumitra

    2014-01-01

    We solve the Einstein equation in five-dimensional space-time for Randall-Sundrum Brane world model with time dependent radion field to study the variation of brane scale factor with time. We have shown that as the radion field decreases with time compactifying the extra dimension, the scale factor increases exponentially with time leading to an inflationary scenario. We have also proposed a time dependent generalization of the Goldberger-Wise moduli stabilization mechanism to explain the time evolution of the radion field to reach a stable value, after which the scale factor on the brane exits from inflationary expansion. (orig.)

  18. A Case Study on Stratified Settlement and Rebound Characteristics due to Dewatering in Shanghai Subway Station

    OpenAIRE

    Wang, Jianxiu; Huang, Tianrong; Sui, Dongchang

    2013-01-01

    Based on the Yishan Metro Station Project of Shanghai Metro Line number 9, a centrifugal model test was conducted to investigate the behavior of stratified settlement and rebound (SSR) of Shanghai soft clay caused by dewatering in deep subway station pit. The soil model was composed of three layers, and the dewatering process was simulated by self-invention of decompressing devise. The results indicate that SSR occurs when the decompression was carried out, and only negative rebound was found...

  19. Advanced liquid-cooled, turbocharged and intercooled stratified charge rotary engines for aircraft

    Science.gov (United States)

    Mount, Robert E.; Bartel, John; Hady, William F.

    1987-01-01

    Developments concerning stratified-charge rotary (SCR) engines over the past 10 years are reviewed. Aircraft engines being developed using SCR technology are shown and described, and the ability of such technology to meet general aviation engine needs is considered. Production timing and availability of SCR technology for the development of aviation rotary engines are discussed, and continuing efforts toward improving this technology, including NASA efforts, are described.

  20. Generation of stratified squamous epithelial progenitor cells from mouse induced pluripotent stem cells.

    Directory of Open Access Journals (Sweden)

    Satoru Yoshida

    Full Text Available BACKGROUND: Application of induced pluripotent stem (iPS cells in regenerative medicine will bypass ethical issues associated with use of embryonic stem cells. In addition, patient-specific IPS cells can be useful to elucidate the pathophysiology of genetic disorders, drug screening, and tailor-made medicine. However, in order to apply iPS cells to mitotic tissue, induction of tissue stem cells that give rise to progeny of the target organ is required. METHODOLOGY/PRINCIPAL FINDINGS: We induced stratified epithelial cells from mouse iPS cells by co-culture with PA6 feeder cells (SDIA-method with use of BMP4. Clusters of cells positive for the differentiation markers KRT1 or KRT12 were observed in KRT14-positive colonies. We successfully cloned KRT14 and p63 double-positive stratified epithelial progenitor cells from iPS-derived epithelial cells, which formed stratified epithelial sheets consisting of five- to six-polarized epithelial cells in vitro. When these clonal cells were cultured on denuded mouse corneas, a robust stratified epithelial layer was observed with physiological cell polarity including high levels of E-cadherin, p63 and K15 expression in the basal layer and ZO-1 in the superficial layer, recapitulating the apico-basal polarity of the epithelium in vivo. CONCLUSIONS/SIGNIFICANCE: These results suggest that KRT14 and p63 double-positive epithelial progenitor cells can be cloned from iPS cells in order to produce polarized multilayer epithelial cell sheets.

  1. Spatial Analysis of Geothermal Resource Potential in New York and Pennsylvania: A Stratified Kriging Approach

    Science.gov (United States)

    Smith, J. D.; Whealton, C. A.; Stedinger, J. R.

    2014-12-01

    Resource assessments for low-grade geothermal applications employ available well temperature measurements to determine if the resource potential is sufficient for supporting district heating opportunities. This study used a compilation of bottomhole temperature (BHT) data from recent unconventional shale oil and gas wells, along with legacy oil, gas, and storage wells, in Pennsylvania (PA) and New York (NY). Our study's goal was to predict the geothermal resource potential and associated uncertainty for the NY-PA region using kriging interpolation. The dataset was scanned for outliers, and some observations were removed. Because these wells were drilled for reasons other than geothermal resource assessment, their spatial density varied widely. An exploratory spatial statistical analysis revealed differences in the spatial structure of the geothermal gradient data (the kriging semi-variogram and its nugget variance, shape, sill, and the degree of anisotropy). As a result, a stratified kriging procedure was adopted to better capture the statistical structure of the data, to generate an interpolated surface, and to quantify the uncertainty of the computed surface. The area was stratified reflecting different physiographic provinces in NY and PA that have geologic properties likely related to variations in the value of the geothermal gradient. The kriging prediction and the variance-of-prediction were determined for each province by the generation of a semi-variogram using only the wells that were located within that province. A leave-one-out cross validation (LOOCV) was conducted as a diagnostic tool. The results of stratified kriging were compared to kriging using the whole region to determine the impact of stratification. The two approaches provided similar predictions of the geothermal gradient. However, the variance-of-prediction was different. The stratified approach is recommended because it gave a more appropriate site-specific characterization of uncertainty

  2. Experiments on the Microenvironment and Breathing of a Person in Isothermal and Stratified Surroundings

    DEFF Research Database (Denmark)

    Nielsen, Peter V.; Jensen, Rasmus Lund; Litewnicki, Michal

    2009-01-01

    This study investigates the characteristics of human exhalation. Experiments are performed on a breathing thermal manikin in a test room. The manikin is heated, and an artificial lung is used to generate varying air flows with specific flow rates and temperatures for breathing. Smoke visualisation...... is used to show the formation, movement and disappearance of the exhalation jets from both nose and mouth. The exhalation of breathing without ventilation in the room, and with stratified surroundings (displacement ventilation) is analysed....

  3. Stratified prevention: opportunities and limitations. Report on the 1st interdisciplinary cardiovascular workshop in Augsburg.

    Science.gov (United States)

    Kirchhof, Gregor; Lindner, Josef Franz; Achenbach, Stephan; Berger, Klaus; Blankenberg, Stefan; Fangerau, Heiner; Gimpel, Henner; Gassner, Ulrich M; Kersten, Jens; Magnus, Dorothea; Rebscher, Herbert; Schunkert, Heribert; Rixen, Stephan; Kirchhof, Paulus

    2018-03-01

    Sufficient exercise and sleep, a balanced diet, moderate alcohol consumption and a good approach to handle stress have been known as lifestyles that protect health and longevity since the Middle Age. This traditional prevention quintet, turned into a sextet by smoking cessation, has been the basis of the "preventive personality" that formed in the twentieth century. Recent analyses of big data sets including genomic and physiological measurements have unleashed novel opportunities to estimate individual health risks with unprecedented accuracy, allowing to target preventive interventions to persons at high risk and at the same time to spare those in whom preventive measures may not be needed or even be harmful. To fully grasp these opportunities for modern preventive medicine, the established healthy life styles require supplementation by stratified prevention. The opportunities of these developments for life and health contrast with justified concerns: A "surveillance society", able to predict individual behaviour based on big data, threatens individual freedom and jeopardises equality. Social insurance law and the new German Disease Prevention Act (Präventionsgesetz) rightly stress the need for research to underpin stratified prevention which is accessible to all, ethical, effective, and evidence based. An ethical and acceptable development of stratified prevention needs to start with autonomous individuals who control and understand all information pertaining to their health. This creates a mandate for lifelong health education, enabled in an individualised form by digital technology. Stratified prevention furthermore requires the evidence-based development of a new taxonomy of cardiovascular diseases that reflects disease mechanisms. Such interdisciplinary research needs broad support from society and a better use of biosamples and data sets within an updated research governance framework.

  4. Effect of stratified inequality of blood flow on gas exchange in liquid-filled lungs.

    Science.gov (United States)

    West, J. B.; Maloney, J. E.; Castle, B. L.

    1972-01-01

    This investigation set out to answer two questions: (1) are the distal alveoli in the terminal lung units less well perfused than the proximal alveoli, i.e., is there stratification of blood flow; and (2) if so, does this enhance gas exchange in the presence of stratified inequality of ventilation. Excised dog lungs were ventilated with saline and perfused with blood. Following single inspirations of xenon 133 in saline and various periods of breath holding, the expired xenon concentration against volume was measured and it confirmed marked stratified inequality of ventilation under these conditions. By measuring the rate of depletion of xenon from alveoli during a period of blood flow, we showed that the alveoli which emptied at the end of expiration had 16% less blood flow than those exhaling earlier. However, by measuring the xenon concentration in pulmonary venous blood, we found that about 10% less tracer was transferred from the alveoli into the blood when the inspired xenon was stratified within the respiratory zone. Thus while stratification of blood flow was confirmed, it was shown to impair rather than enhance the efficiency of gas transfer.

  5. Energy Cascade from Internal Modes in Non-uniformly Stratified Fluid through Excitation of Superharmonic Disturbances

    Science.gov (United States)

    Sutherland, B. R.

    2016-02-01

    It is well established that two-dimensional internal plane waves and modes in uniformly stratified fluid efficiently transfer energy to smaller scale waves and ultimately turbulent mixing through parametric subharmonic instability (PSI). The numerical simulations of MacKinnon & Winters (GRL 2005) predicted PSI should act efficiently to disrupt the internal tide. However, while in situ observations showed the presence of PSI, it was not found to be appreciable. One reason for the discrepancy between simulations and observations is that the former examined an internal mode in uniformly stratified fluid whereas, in reality, the internal tide exists in non-uniform stratification and is manifest as sinusoidal oscillations of the thermocline. Through theory supported by numerical simulations, it is shown that internal modes in non-uniform stratification immediately excite superharmonics, not subharmonic disturbances. These have double the horizontal wavenumber and double the frequency of the parent mode and hence move with the same horizontal phase speed of the parent mode. As the disturbances grow in amplitude, however, they interact with the parent mode generating small-scale vertically propagating internal waves within the strongly stratified layer. The occurrence of PSI over very long times can occur, as in the simulations of Hazewinkel and Winters (JPO 2011). However, a comprehensive understanding of the energy cascade from the internal tide to small scales must consider the evolution of excited superharmonic disturbances.

  6. Theory of hyperbolic stratified nanostructures for surface-enhanced Raman scattering

    Science.gov (United States)

    Wong, Herman M. K.; Dezfouli, Mohsen Kamandar; Axelrod, Simon; Hughes, Stephen; Helmy, Amr S.

    2017-11-01

    We theoretically investigate the enhancement of surface enhanced Raman spectroscopy (SERS) using hyperbolic stratified nanostructures and compare to metal nanoresonators. The photon Green function of each nanostructure within its environment is first obtained from a semianalytical modal theory, which is used in a quantum optics formalism of the molecule-nanostructure interaction to model the SERS spectrum. An intuitive methodology is presented for calculating the single-molecule enhancement factor (SMEF), which is also able to predict known experimental SERS enhancement factors of a gold nanodimer. We elucidate the important figures-of-merit of the enhancement and explore these for different designs. We find that the use of hyperbolic stratified materials can enhance the photonic local density of states (LDOS) by close to two times in comparison to pure metal nanostructures, when both designed to work at the same operating wavelengths. However, the increased LDOS is accompanied by higher electric field concentration within the lossy hyperbolic material, which leads to increased quenching that serves to reduce the overall detected SERS enhancement in the far field. For nanoresonators with resonant localized surface plasmon wavelengths in the near-infrared, the SMEF for the hyperbolic stratified nanostructure is approximately one order of magnitude lower than the pure metal counterpart. Conversely, we show that by detecting the Raman signal using a near-field probe, hyperbolic materials can provide an improvement in SERS enhancement compared to using pure metal nanostructures when the probe is sufficiently close (<50 nm ) to the Raman active molecule at the plasmonic hotspot.

  7. Interfacial transport characteristics in a gas-liquid or an immiscible liquid-liquid stratified flow

    International Nuclear Information System (INIS)

    Inoue, A.; Aoki, S.; Aritomi, M.; Kozawa, Y.

    1982-01-01

    This paper is a review for an interfacial transport characteristics of mass, momentum and energy in a gas-liquid or a immiscible liquid-liquid stratified flow with wavy interface which have been studied in our division. In the experiment, a characteristic of wave motion and its effect to the turbulence near the interface as well as overall flow characteristics like pressure drop, position of the interface were investigated in an air-water, an air-mercury and a water-liquid metal stratified flow. On the other hand, several models based on the mixing length model and a two-equation model of turbulence, with special interfacial boundary conditions in which the wavy surface was regarded as a rough surface correspond to the wavy height, a source of turbulent energy equal to the wave energy and a damped-turbulence due to the surface tension, were proposed to predict the flow characteristics and the interfacial heat transfer in a fully developed and an undeveloped stratified flow and examined by the experimental data. (author)

  8. Stratified flows and internal waves in the Vema Fracture Zone of the Mid Atlantic Ridge

    Science.gov (United States)

    Makarenko, Nikolay; Morozov, Eugene; Tarakanov, Roman; Demidova, Tatiana; Frey, Dmitri; Grigorenko, Klim

    2017-04-01

    In this paper, we study stratified flows and internal waves in the Vema fracture zone of the Mid Atlantic Ridge. This fracture provides intense transportation of cold abyssal waters from the West Atlantic to the equatorial region of the East Atlantic [1]. The results of measurements [2,3] carried out in the cruises of RV Akademik Sergey Vavilov in 2014-2016 are presented. The structure of the near-bottom flow is studied experimentally on the basis of CTD- and LADCP profiling. Theoretical analysis involves mathematical formulation of stratified fluid flow which uses CTD-data obtained from field observation. Spectral properties and kinematic characteristics of internal waves are calculated and discussed. This work was supported by RFBR (grants No 15-01-03942, 16-35-50158). References [1] Morozov E., Demidov A., Tarakanov R. and Zenk W. Abyssal Channels in the Atlantic Ocean: Water Structure and Flows, Springer, Dordrecht, 2010. [2] Morozov E.G., Tarakanov R.Yu., and Makarenko N.I. Flows of Antarctic Bottom Water through fractures in the southern part of the North Mid Atlantic Ridge, Oceanology, 2015, 55, 796-800. [3] Grigorenko K.S., Makarenko N.I., Morozov E.G., Tarakanov R.Yu., and Frey D.I. Stratified flows and internal waves in the Central West Atlantic, J. Physics: Conf. Series, 2016, 722, 012011.

  9. Turbulent circulation above the surface heat source in stably stratified atmosphere

    Science.gov (United States)

    Kurbatskii, A. F.; Kurbatskaya, L. I.

    2016-10-01

    The 3-level RANS approach for simulating a turbulent circulation over the heat island in a stably stratified environment under nearly calm conditions is formulated. The turbulent kinetic energy its spectral consumption (dissipation) and the dispersion of turbulent fluctuations of temperature are found from differential equations, thus the correct modeling of transport processes in the interface layer with the counter-gradient heat flux is assured. The three-parameter turbulence RANS approach minimizes difficulties in simulating the turbulent transport in a stably stratified environment and reduces efforts needed for the numerical implementation of the 3-level RANS approach. Numerical simulation of the turbulent structure of the penetrative convection over the heat island under conditions of stably stratified atmosphere demonstrates that the three-equation model is able to predict the thermal circulation induced by the heat island. The temperature distribution, root-mean-square fluctuations of the turbulent velocity and temperature fields and spectral turbulent kinetic energy flux are in good agreement with the experimental data. The model describes such thin physical effects, as a crossing of vertical profiles of temperature of a thermal plume with the formation of the negative buoyancy area testifying to development of the dome-shaped form at the top part of a plume in the form of "hat".

  10. [Why is bread consumption decreasing?].

    Science.gov (United States)

    Rolland, M F; Chabert, C; Serville, Y

    1977-01-01

    In France bread plays a very special and ambivalent role among our foodstuffs because of the considerable drop in its consumption, its alleged harmful effects on our health and the respect in which it is traditionally held. More than half the 1 089 adults interviewed in this study say they have decreased their consumption of bread in the last 10 years. The reasons given vary according to age, body weight and urbanization level. The main reasons given for this restriction are the desire to prevent or reduce obesity, the decrease in physical activity, the general reduction in food consumption and the possibility of diversifying foods even further. Moreover, the decreasing appeal of bread in relation to other foods, as well as a modification in the structure of meals, in which bread becomes less useful to accompany other food, accentuate this loss of attraction. However, the respect for bread as part of the staple diet remains very acute as 95 p. 100 of those interviewed express a reluctance to throw bread away, more for cultural than economic reasons. Mechanization and urbanization having brought about a decrease in energy needs, the most common alimentary adaptation is general caloric restriction by which glucids, and especially bread, are curtailed.

  11. The stand-alone test and decreasing serial cost sharing

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Thorlund-Petersen, Lars

    2000-01-01

    The rule of decreasing serial cost sharing defined in de Frutos [1] over the class of concave cost functions may violate the important stand-alone test. Sufficient conditions for the test to be satisfied are given, in terms of individual rationality as well as coalitional stability...

  12. Implementing the Keele stratified care model for patients with low back pain: an observational impact study.

    Science.gov (United States)

    Bamford, Adrian; Nation, Andy; Durrell, Susie; Andronis, Lazaros; Rule, Ellen; McLeod, Hugh

    2017-02-03

    The Keele stratified care model for management of low back pain comprises use of the prognostic STarT Back Screening Tool to allocate patients into one of three risk-defined categories leading to associated risk-specific treatment pathways, such that high-risk patients receive enhanced treatment and more sessions than medium- and low-risk patients. The Keele model is associated with economic benefits and is being widely implemented. The objective was to assess the use of the stratified model following its introduction in an acute hospital physiotherapy department setting in Gloucestershire, England. Physiotherapists recorded data on 201 patients treated using the Keele model in two audits in 2013 and 2014. To assess whether implementation of the stratified model was associated with the anticipated range of treatment sessions, regression analysis of the audit data was used to determine whether high- or medium-risk patients received significantly more treatment sessions than low-risk patients. The analysis controlled for patient characteristics, year, physiotherapists' seniority and physiotherapist. To assess the physiotherapists' views on the usefulness of the stratified model, audit data on this were analysed using framework methods. To assess the potential economic consequences of introducing the stratified care model in Gloucestershire, published economic evaluation findings on back-related National Health Service (NHS) costs, quality-adjusted life years (QALYs) and societal productivity losses were applied to audit data on the proportion of patients by risk classification and estimates of local incidence. When the Keele model was implemented, patients received significantly more treatment sessions as the risk-rating increased, in line with the anticipated impact of targeted treatment pathways. Physiotherapists were largely positive about using the model. The potential annual impact of rolling out the model across Gloucestershire is a gain in approximately 30

  13. Investigation of temperature fluctuation phenomena in a stratified steam-water two-phase flow in a simulating pressurizer spray pipe of a pressurized water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Miyoshi, Koji, E-mail: miyoshi.koj@inss.co.jp; Takenaka, Nobuyuki; Ishida, Taisuke; Sugimoto, Katsumi

    2017-05-15

    Highlights: • Thermal hydraulics phenomena were discussed in a spray pipe of pressurizer. • Temperature fluctuation was investigated in a stratified steam-water two-phase. • Remarkable liquid temperature fluctuations were observed in the liquid layer. • The observed temperature fluctuations were caused by the internal gravity wave. • The temperature fluctuations decreased with increasing dissolved oxygen. - Abstract: Temperature fluctuation phenomena in a stratified steam-water two-phase flow in a horizontal rectangular duct, which simulate a pressurizer spray pipe of a pressurized water reactor, were studied experimentally. Vertical distributions of the temperature and the liquid velocity were measured with water of various dissolved oxygen concentrations. Large liquid temperature fluctuations were observed when the water was deaerated well and dissolved oxygen concentration was around 10 ppb. The large temperature fluctuations were not observed when the oxygen concentration was higher. It was shown that the observed temperature fluctuations were caused by the internal gravity wave since the Richardson numbers were larger than 0.25 and the temperature fluctuation frequencies were around the Brunt-Väisälä frequencies in the present experimental conditions. The temperature fluctuations decreased by the non-condensable gas since the non-condensable gas suppressed the condensation and the temperature difference in the liquid layer was small.

  14. Two-dimensional interaction of a shear flow with a free surface in a stratified fluid and its solitary-wave solutions via mathematical methods

    Science.gov (United States)

    Seadawy, Aly R.

    2017-12-01

    In this study, we presented the problem formulations of models for internal solitary waves in a stratified shear flow with a free surface. The nonlinear higher order of extended KdV equations for the free surface displacement is generated. We derived the coefficients of the nonlinear higher-order extended KdV equation in terms of integrals of the modal function for the linear long-wave theory. The wave amplitude potential and the fluid pressure of the extended KdV equation in the form of solitary-wave solutions are deduced. We discussed and analyzed the stability of the obtained solutions and the movement role of the waves by making graphs of the exact solutions.

  15. Investigations in the upper load range of stratified operation with injection pressures up to 1000 bar; Untersuchungen im oberen Lastbereich des Schichtbetriebes bei Einspritzdruecken bis 1000 bar

    Energy Technology Data Exchange (ETDEWEB)

    Buri, Stefan; Busch, Steve; Kubach, Heiko; Spicher, Ulrich [Karlsruhe Univ. (DE). Inst. fuer Kolbenmaschinen (IFKM)

    2010-07-01

    This paper presents the results of recent research that has been performed on a single-cylinder spray-guided DISI engine at the Institut fuer Kolbenmaschinen. A production multihole injector is used as a baseline and compared with a specially adapted injector at higher injection pressures. Injection pressures of up to 1000 bar are utilized to investigate the combustion and emissions characteristics at the stability limit of stratified combustion. With the modified injector, measurements with the two-color method are applied to analyze this operating condition in terms of soot formation. Included are results for a spark timing variation with 1000 bar injection pressure, an injection pressure variation with constant spark timing, and fuel consumption-optimized engine operating parameters in order to analyze realistic operating points. The benefits of injecting fuel at higher pressures are described, as are the limitations of the experimental setup. (orig.)

  16. Decreasing Physical Inactivity in the Veterans Health Administration Employee Population.

    Science.gov (United States)

    Schult, Tamara M; Schmunk, Sandra K; Awosika, Ebi R

    2016-12-01

    The aim of this study was to describe a comprehensive approach to decrease physical inactivity in the Veterans Health Administration (VHA) employee population. The approach included (1) initiatives to decrease physical inactivity in the workplace; (2) two operational surveys to assess system-wide service provision; and (3) two national employee surveys. From 2010 to 2012, 86 employee fitness centers were completed in VA medical centers. A grants program (2010 to 2015) funded smaller projects designed to decrease physical inactivity in the workplace. Projects involved the provision of equipment to decrease sedentary behaviors, including stability balls, treadmill and sit-to-stand desks, stairwell projects, and funding for on-site fitness classes, bicycle racks, and outdoor par courses and walking paths among others. A comprehensive approach to decrease physical inactivity in VHA employees was successful. Overall, self-reported, age-adjusted physical inactivity in VHA employees decreased from 25.3% in 2010 to 16.1% in 2015.

  17. Magical thinking decreases across adulthood.

    Science.gov (United States)

    Brashier, Nadia M; Multhaup, Kristi S

    2017-12-01

    Magical thinking, or illogical causal reasoning such as superstitions, decreases across childhood, but almost no data speak to whether this developmental trajectory continues across the life span. In four experiments, magical thinking decreased across adulthood. This pattern replicated across two judgment domains and could not be explained by age-related differences in tolerance of ambiguity, domain-specific knowledge, or search for meaning. These data complement and extend findings that experience, accumulated over decades, guides older adults' judgments so that they match, or even exceed, young adults' performance. They also counter participants' expectations, and cultural sayings (e.g., "old wives' tales"), that suggest that older adults are especially superstitious. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  18. Does fertility decrease household consumption?

    OpenAIRE

    Jungho Kim; Henriette Engelhardt; Alexia Fürnkranz-Prskawetz; Arnstein Aassve

    2009-01-01

    This paper presents an empirical analysis of the relationship between fertility and a direct measure of poverty for Indonesia, a country, which has experienced unprecedented economic growth and sharp fertility declines over recent decades. It focuses on illustrating the sensitivity of the effect of fertility on household consumption with respect to the equivalence scale by applying the propensity score matching method. The analysis suggests that a newborn child decreases household consumption...

  19. Spatial and seasonal changes in optical properties of autochthonous and allochthonous chromophoric dissolved organic matter in a stratified mountain lake.

    Science.gov (United States)

    Bracchini, Luca; Dattilo, Arduino Massimo; Hull, Vincent; Loiselle, Steven Arthur; Nannicini, Luciano; Picchi, Maria Pia; Ricci, Maso; Santinelli, Chiara; Seritti, Alfredo; Tognazzi, Antonio; Rossi, Claudio

    2010-03-01

    In this study, we present results on seasonal and spatial changes in CDOM absorption and fluorescence (fCDOM) in a deep mountain lake (Salto Lake, Italy). A novel approach was used to describe the shape of CDOM absorption between 250-700 nm (distribution of the spectral slope, S(lambda)) and a new fluorescence ratio is used to distinguish between humic and amino acid-like components. Solar ultraviolet irradiance, dissolved organic carbon (DOC), DOM fluorescence and absorption measurements were analysed and compared to other physicochemical parameters. We show that in the UV-exposed mixed layer: (i) fluorescence by autochthonous amino acid-like CDOM, (ii) values of S(lambda) across UV-C and UV-B wavebands increased during the summer months, whereas (i) average molar absorption coefficient and (ii) fluorescence by allochthonous humic CDOM decreased. In the unexposed deep layer of the water column (and in the entire water column in winter), humic-like CDOM presented high values of molar absorption coefficients and low values of S(lambda). UV attenuation coefficients correlated with both chlorophyll a concentrations and CDOM absorption. In agreement with changes in CDOM, minimal values in UV attenuation were found in summer. The S(lambda) curve was used as a signature of the mixture between photobleached and algal-derived CDOM with respect to the unexposed chromophoric dissolved compounds in this thermal stratified lake. Furthermore, S(lambda) curves were useful to distinguish between low and high molecular weight CDOM.

  20. Effects of piston surface treatments on performance and emissions of a methanol-fueled, direct injection, stratified charge engine

    Energy Technology Data Exchange (ETDEWEB)

    West, B.; Green, J.B. [Oak Ridge National Lab., TN (United States)

    1994-07-01

    The purpose of this study was to investigate the effects of thermal barrier coatings and/or surface treatments on the performance and emissions of a methanol-fueled, direct-injection, stratified-charge (DISC) engine. A Ricardo Hydra Mark III engine was used for this work and in previous experiments at Oak Ridge National Laboratory (ORNL). The primary focus of the study was to examine the effects of various piston insert surface treatments on hydrocarbon (HC) and oxides of nitrogen (NO{sub x}) emissions. Previous studies have shown that engines of this class have a tendency to perform poorly at low loads and have high unburned fuel emissions. A blank aluminum piston was modified to employ removable piston bowl inserts. Four different inserts were tested in the experiment: aluminum, stainless steel with a 1.27-mm (0.050-in.) air gap (to act as a thermal barrier), and two stainless steel/air-gap inserts with coatings. Two stainless steel inserts were dimensionally modified to account for the coating thickness (1.27-mm) and coated identically with partially stabilized zirconia (PSZ). One of the coated inserts then had an additional seal-coat applied. The coated inserts were otherwise identical to the stainless steel/air-gap insert (i.e., they employed the same 1.27-mm air gap). Thermal barrier coatings were employed in an attempt to increase combustion chamber surface temperatures, thereby reducing wall quenching and promoting more complete combustion of the fuel in the quench zone. The seal-coat was applied to the zirconia to reduce the surface porosity; previous research suggested that despite the possibly higher surface temperatures obtainable with a ceramic coating, the high surface area of a plasma-sprayed coating may actually allow fuel to adhere to the surface and increase the unburned fuel emissions and fuel consumption.

  1. The Values of Combined and Sub-Stratified Imaging Scores with Ultrasonography and Mammography in Breast Cancer Subtypes.

    Directory of Open Access Journals (Sweden)

    Tsun-Hou Chang

    Full Text Available The Breast Imaging Reporting and Data System (BI-RADS of Mammography (MG and Ultrasonography (US were equivalent to the "5-point score" and applied for combined and sub-stratified imaging assessments. This study evaluated the value of combined and sub-stratified imaging assessments with MG and US over breast cancer subtypes (BCS.Medical records of 5,037 cases having imaging-guided core biopsy, performed from 2009 to 2012, were retrospectively reviewed. This study selected 1,995 cases (1,457 benign and 538 invasive cancer having both MG and US before biopsy. These cases were categorized with the "5-point score" for their MG and US, and applied for combined and sub-stratified imaging assessments. Invasive cancers were classified on the basis of BCS, and correlated with combined and sub-stratified imaging assessments.These selected cases were evaluated by the "5-point score." MG, US, and combined and sub-stratified imaging assessments all revealed statistically significant (P < 0.001 incidence of malignancy. The sensitivity was increased in the combined imaging score (99.8%, and the specificity was increased in the sub-stratified combined score (75.4%. In the sub-stratified combined imaging assessment, all BCS can be classified with higher scores (abnormality hierarchy, and luminal B subtype showed the most salient result (hierarchy: higher, 95%; lower, 5%.Combined and sub-stratified imaging assessments can increase sensitivity and specificity of breast cancer diagnosis, respectively, and Luminal B subtype shows the best identification by sub-stratified combined imaging scoring.

  2. The stability of the water column in french ponds (limousin region by the calculation of the wedderburn number

    Directory of Open Access Journals (Sweden)

    TOUCHART L.

    2014-03-01

    Full Text Available Oxygenation and biological life in lakes, reservoirs and ponds depend on the stability of the water column and on the rhythms of stratification and mixing periods. Slight thermal stratification in ponds often is regarded as the same as instability in shallow lakes. Nevertheless fetch in ponds is very short, what reduces the mixing. Wedderburn number (quotient of the buoyancy by the mixing is used to quantify the stability in shallow water bodies. We calculate it for some ponds in French region Limousin, due to original hourly water temperature measurements in all depths and wind data of Météofrance stations. First results show that very high values (above 10 are frequent in summer and spring period (during 41% of the total time of 2 336 hours from May to July in three ponds. That is why we may consider Limousin ponds as stable stratified bodies of water despite their shallowness. Continuous measurements allow to calculate the diurnal cycle and other time scales of the Wedderburn number, with periods of weakening, when air temperatures and surface water temperatures decrease, wind speed increases and when the wind blows in the same direction with the length of the pond. The most complex variable is the depth of the thermocline; a light increase of the breeze thickens the upper warm layer and strengthens the stability, but an important increase of the wind tends to destroy the stratification.

  3. Decreasing Fires in Mediterranean Europe.

    Directory of Open Access Journals (Sweden)

    Marco Turco

    Full Text Available Forest fires are a serious environmental hazard in southern Europe. Quantitative assessment of recent trends in fire statistics is important for assessing the possible shifts induced by climate and other environmental/socioeconomic changes in this area. Here we analyse recent fire trends in Portugal, Spain, southern France, Italy and Greece, building on a homogenized fire database integrating official fire statistics provided by several national/EU agencies. During the period 1985-2011, the total annual burned area (BA displayed a general decreasing trend, with the exception of Portugal, where a heterogeneous signal was found. Considering all countries globally, we found that BA decreased by about 3020 km2 over the 27-year-long study period (i.e. about -66% of the mean historical value. These results are consistent with those obtained on longer time scales when data were available, also yielding predominantly negative trends in Spain and France (1974-2011 and a mixed trend in Portugal (1980-2011. Similar overall results were found for the annual number of fires (NF, which globally decreased by about 12600 in the study period (about -59%, except for Spain where, excluding the provinces along the Mediterranean coast, an upward trend was found for the longer period. We argue that the negative trends can be explained, at least in part, by an increased effort in fire management and prevention after the big fires of the 1980's, while positive trends may be related to recent socioeconomic transformations leading to more hazardous landscape configurations, as well as to the observed warming of recent decades. We stress the importance of fire data homogenization prior to analysis, in order to alleviate spurious effects associated with non-stationarities in the data due to temporal variations in fire detection efforts.

  4. Decreasing Fires in Mediterranean Europe.

    Science.gov (United States)

    Turco, Marco; Bedia, Joaquín; Di Liberto, Fabrizio; Fiorucci, Paolo; von Hardenberg, Jost; Koutsias, Nikos; Llasat, Maria-Carmen; Xystrakis, Fotios; Provenzale, Antonello

    2016-01-01

    Forest fires are a serious environmental hazard in southern Europe. Quantitative assessment of recent trends in fire statistics is important for assessing the possible shifts induced by climate and other environmental/socioeconomic changes in this area. Here we analyse recent fire trends in Portugal, Spain, southern France, Italy and Greece, building on a homogenized fire database integrating official fire statistics provided by several national/EU agencies. During the period 1985-2011, the total annual burned area (BA) displayed a general decreasing trend, with the exception of Portugal, where a heterogeneous signal was found. Considering all countries globally, we found that BA decreased by about 3020 km2 over the 27-year-long study period (i.e. about -66% of the mean historical value). These results are consistent with those obtained on longer time scales when data were available, also yielding predominantly negative trends in Spain and France (1974-2011) and a mixed trend in Portugal (1980-2011). Similar overall results were found for the annual number of fires (NF), which globally decreased by about 12600 in the study period (about -59%), except for Spain where, excluding the provinces along the Mediterranean coast, an upward trend was found for the longer period. We argue that the negative trends can be explained, at least in part, by an increased effort in fire management and prevention after the big fires of the 1980's, while positive trends may be related to recent socioeconomic transformations leading to more hazardous landscape configurations, as well as to the observed warming of recent decades. We stress the importance of fire data homogenization prior to analysis, in order to alleviate spurious effects associated with non-stationarities in the data due to temporal variations in fire detection efforts.

  5. Analysis of flame propagation phenomenon in simplified stratified charge conditions; Tanjunkasareta sojo kyukiba ni okeru kaen denpa gensho no kansatsu

    Energy Technology Data Exchange (ETDEWEB)

    Moriyoshi, Y; Morikawa, H [Chiba University, Chiba (Japan); Kamimoto, T [Tokyo Institute of Technology, Tokyo (Japan)

    1997-10-01

    Since the local inhomogeneity of mixture concentration inside the cylinder affects the combustion characteristics, a basic research on combustion phenomenon in stratified charge conditions is required. The authors have made experiments with a constant-volume chamber, which can simulate an idealized stratified charge field by using a removable partition, to obtain the combustion characteristics. Also, numerical calculations are made using some combustion models. As a result, the important feature that the combustion speed is faster in stratified condition than in homogeneous condition can be predicted by the two-step reaction model. 4 refs., 8 figs.

  6. Stabilized superconducting materials and fabrication process

    International Nuclear Information System (INIS)

    Chevallier, B.; Dance, J.M.; Etourneau, J.; Lozano, L.; Tressaud, A.; Tournier, R.; Sulpice, A.; Chaussy, J.; Lejay, P.

    1989-01-01

    Superconducting ceramics are fluorinated at a temperature ≤ 120 0 C. Are also claimed new superconducting materials with a fluorine concentration gradient decreasing from the surface to the core. Superconductivity is stabilized and/or improved [fr

  7. Importance of climate change-physical forcing on the increase of cyanobacterial blooms in a small, stratified lake

    Directory of Open Access Journals (Sweden)

    Dolores Planas

    2016-03-01

    Full Text Available The community structure of planktonic cyanobacteria was studied in a dimictic lake in which recurrent summer surface algal blooms have frequently occurred since the beginning of this millennium. In eutrophic-hypereutrophic lakes, epilimnetic cyanobacterial blooms are promoted by increased ambient temperatures and water column thermal stability, which favour the vertical migration of buoyancy-regulating cyanobacteria. Here we propose that intensified external energy (wind that alters thermocline stability could explain the occurence of heavy blooms in the surface of lakes with low external nutrient loading. Specifically, we hypothesized that: i in small stratified lakes with low external nutrient sources, cyanobacterial growth primarily occurs near the lake bottom, where phosphorus is more abundant and light is available; ii we additionally hypothesized that turbulence induced by strong winds increases the amplitude and energy of metalimnetic internal waves and entrains meta- and hypolimnetic water,  rich in nutrients and cyanobacteria, into the epilimnion. The study was done in a small lake (45 Ha, maximum and mean depth 7.2 m and 4.3 m, respectively with mean epilimnetic dissolved phosphorus concentrations ≈ 4 μg L-1 and chlorophyll α ≈ 8 μg L-1.  Vertical temperature profiles during the open season were continuously registered using thermistors.  Weekly vertical profiles of light transmission, phytoplankton distribution and water chemistry were also taken. On one occasion, these variables were measured throughout a continuous 24 h cycle. Results demonstrated that summer cyanobacterial blooms were dominated by Plankthotrix spp., which began their cycle in late spring at the bottom of the lake, and grew to form dense metalimnetic biomass peaks. Time series analysis of isotherms and the Lake number indicated that internal metalimnetic waves (seiches were present through the summer. During the diel sampling cycle, we found that medium to

  8. Field investigation of keyblock stability

    International Nuclear Information System (INIS)

    Yow, J.L. Jr.

    1985-04-01

    Discontinuities in a rock mass can intersect an excavation surface to form discrete blocks (keyblocks) which can be unstable. This engineering problem is divided into two parts: block identification, and evaluation of block stability. One stable keyblock and thirteen fallen keyblocks were observed in field investigations at the Nevada Test Site. Nine blocks were measured in detail sufficient to allow back-analysis of their stability. Measurements included block geometry, and discontinuity roughness and compressive strength. Back-analysis correctly predicted stability or failure in all but two cases. These two exceptions involved situations that violated the stress assumptions of the stability calculations. Keyblock faces correlated well with known joint set orientations. The effect of tunnel orientation on keyblock frequency was apparent. Back-analysis of physical models successfully predicted block pullout force for two-dimensional models of unit thickness. Two-dimensional (2D) and three-dimensional (3D) analytic models for the stability of simple pyramidal keyblocks were examined. Calculated stability is greater for 3D analyses than for 2D analyses. Calculated keyblock stability increases with larger in situ stress magnitudes, larger lateral stress ratios, and larger shear strengths. Discontinuity stiffness controls block displacement more strongly than it does stability itself. Large keyblocks are less stable than small ones, and stability increases as blocks become more slender. Rock mass temperature decreases reduce the confining stress magnitudes and can lead to failure. The pattern of stresses affecting each block face explains conceptually the occurrence of pyramidal keyblocks that are truncated near their apex

  9. Rapid shelf-wide cooling response of a stratified coastal ocean to hurricanes.

    Science.gov (United States)

    Seroka, Greg; Miles, Travis; Xu, Yi; Kohut, Josh; Schofield, Oscar; Glenn, Scott

    2017-06-01

    Large uncertainty in the predicted intensity of tropical cyclones (TCs) persists compared to the steadily improving skill in the predicted TC tracks. This intensity uncertainty has its most significant implications in the coastal zone, where TC impacts to populated shorelines are greatest. Recent studies have demonstrated that rapid ahead-of-eye-center cooling of a stratified coastal ocean can have a significant impact on hurricane intensity forecasts. Using observation-validated, high-resolution ocean modeling, the stratified coastal ocean cooling processes observed in two U.S. Mid-Atlantic hurricanes were investigated: Hurricane Irene (2011)-with an inshore Mid-Atlantic Bight (MAB) track during the late summer stratified coastal ocean season-and Tropical Storm Barry (2007)-with an offshore track during early summer. For both storms, the critical ahead-of-eye-center depth-averaged force balance across the entire MAB shelf included an onshore wind stress balanced by an offshore pressure gradient. This resulted in onshore surface currents opposing offshore bottom currents that enhanced surface to bottom current shear and turbulent mixing across the thermocline, resulting in the rapid cooling of the surface layer ahead-of-eye-center. Because the same baroclinic and mixing processes occurred for two storms on opposite ends of the track and seasonal stratification envelope, the response appears robust. It will be critical to forecast these processes and their implications for a wide range of future storms using realistic 3-D coupled atmosphere-ocean models to lower the uncertainty in predictions of TC intensities and impacts and enable coastal populations to better respond to increasing rapid intensification threats in an era of rising sea levels.

  10. Identification of distinct layers within the stratified squamous epithelium of the adult human true vocal fold.

    Science.gov (United States)

    Dowdall, Jayme R; Sadow, Peter M; Hartnick, Christopher; Vinarsky, Vladimir; Mou, Hongmei; Zhao, Rui; Song, Phillip C; Franco, Ramon A; Rajagopal, Jayaraj

    2015-09-01

    A precise molecular schema for classifying the different cell types of the normal human vocal fold epithelium is lacking. We hypothesize that the true vocal fold epithelium has a cellular architecture and organization similar to that of other stratified squamous epithelia including the skin, cornea, oral mucosa, and esophagus. In analogy to disorders of the skin and gastrointestinal tract, a molecular definition of the normal cell types within the human vocal fold epithelium and a description of their geometric relationships should serve as a foundation for characterizing cellular changes associated with metaplasia, dysplasia, and cancer. Qualitative study with adult human larynges. Histologic sections of normal human laryngeal tissue were analyzed for morphology (hematoxylin and eosin) and immunohistochemical protein expression profile, including cytokeratins (CK13 and CK14), cornified envelope proteins (involucrin), basal cells (NGFR/p75), and proliferation markers (Ki67). We demonstrated that three distinct cell strata with unique marker profiles are present within the stratified squamous epithelium of the true vocal fold. We used these definitions to establish that cell proliferation is restricted to certain cell types and layers within the epithelium. These distinct cell types are reproducible across five normal adult larynges. We have established that three layers of cells are present within the normal adult stratified squamous epithelium of the true vocal fold. Furthermore, replicating cell populations are largely restricted to the parabasal strata within the epithelium. This delineation of distinct cell populations will facilitate future studies of vocal fold regeneration and cancer. N/A. © 2015 The American Laryngological, Rhinological and Otological Society, Inc.

  11. Mortality in perforated peptic ulcer patients after selective management of stratified poor risk cases.

    Science.gov (United States)

    Rahman, M Mizanur; Islam, M Saiful; Flora, Sabrina; Akhter, S Fariduddin; Hossain, Shahid; Karim, Fazlul

    2007-12-01

    Perforated peptic ulcer disease continues to inflict high morbidity and mortality. Although patients can be stratified according to their surgical risk, optimal management has yet to be described. In this study we demonstrate a treatment option that improves the mortality among critically ill, poor risk patients with perforated peptic ulcer disease. In our study, two series were retrospectively reviewed: group A patients (n = 522) were treated in a single surgical unit at the Dhaka Medical College Hospital, Dhaka, Bangladesh during the 1980s. Among them, 124 patients were stratified as poor risk based on age, delayed presentation, peritoneal contamination, and coexisting medical problems. These criteria were the basis for selecting a group of poor risk patients (n = 84) for minimal surgical intervention (percutaneous peritoneal drainage) out of a larger group of patients, group B (n = 785) treated at Khulna Medical College Hospital during the 1990s. In group A, 479 patients underwent conventional operative management with an operative mortality of 8.97%. Among the 43 deaths, 24 patients were >60 years of age (55.8%), 12 patients had delayed presentation (27.9%), and 7 patients were in shock or had multiple coexisting medical problems (16.2%). In group B, 626 underwent conventional operative management, with 26 deaths at a mortality rate of 4.15%. Altogether, 84 patients were stratified as poor risk and were managed with minimal surgical intervention (percutaneous peritoneal drainage) followed by conservative treatment. Three of these patients died with an operative mortality of 3.5%. Minimal surgical intervention (percutaneous peritoneal drainage) can significantly lower the mortality rate among a selected group of critically ill, poor risk patients with perforated peptic ulcer disease.

  12. Stratified premedication strategy for the prevention of contrast media hypersensitivity in high-risk patients.

    Science.gov (United States)

    Lee, Suh-Young; Yang, Min Suk; Choi, Young-Hoon; Park, Chang Min; Park, Heung-Woo; Cho, Sang Heon; Kang, Hye-Ryun

    2017-03-01

    Although the severity of hypersensitivity reactions to iodinated contrast media varies, it is well correlated with the severity of recurrent reactions; however, prophylaxis protocols are not severity-stratified. To assess the outcomes of tailored prophylaxis according to the severity of hypersensitivity reactions to iodinated contrast media. Our premedication protocols were stratified based on the severity of previous reactions: (1) 4 mg of chlorpheniramine for mild reactions, (2) adding 40 mg of methylprednisolone for moderate reactions, and (3) adding multiple doses of 40 mg of methylprednisolone for severe index reactions. Cases of reexposure in patients with a history of hypersensitivity reactions were routinely monitored and mandatorily recorded. Among a total of 850 patients who underwent enhanced computed tomography after severity-tailored prophylaxis, breakthrough reactions occurred in 17.1%, but most breakthrough reactions (89.0%) were mild and did not require medical treatment. Additional corticosteroid use did not reduce the breakthrough reaction rate in cases with a mild index reaction (16.8% vs 17.2%, P = .70). However, underpremedication with a single dose of corticosteroid revealed significantly higher rates of breakthrough reaction than did double doses of corticosteroid in cases with a severe index reaction (55.6% vs 17.4%, P = .02). Changing the iodinated contrast media resulted in an additional reduction of the breakthrough reaction rate overall (14.9% vs 32.1%, P = .001). In a total severity-based stratified prophylaxis regimens and changing iodinated contrast media can be considered in patients with a history of previous hypersensitivity reaction to iodinated contrast media to reduce the risk of breakthrough reactions. Copyright © 2016 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

  13. Assessment of horizontal in-tube condensation models using MARS code. Part I: Stratified flow condensation

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Seong-Su [Department of Engineering Project, FNC Technology Co., Ltd., Bldg. 135-308, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Department of Nuclear Engineering, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Hong, Soon-Joon, E-mail: sjhong90@fnctech.com [Department of Engineering Project, FNC Technology Co., Ltd., Bldg. 135-308, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Park, Ju-Yeop; Seul, Kwang-Won [Korea Institute of Nuclear Safety, 19 Kuseong-dong, Yuseong-gu, Daejon (Korea, Republic of); Park, Goon-Cherl [Department of Nuclear Engineering, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer This study collected 11 horizontal in-tube condensation models for stratified flow. Black-Right-Pointing-Pointer This study assessed the predictive capability of the models for steam condensation. Black-Right-Pointing-Pointer Purdue-PCCS experiments were simulated using MARS code incorporated with models. Black-Right-Pointing-Pointer Cavallini et al. (2006) model predicts well the data for stratified flow condition. Black-Right-Pointing-Pointer Results of this study can be used to improve condensation model in RELAP5 or MARS. - Abstract: The accurate prediction of the horizontal in-tube condensation heat transfer is a primary concern in the optimum design and safety analysis of horizontal heat exchangers of passive safety systems such as the passive containment cooling system (PCCS), the emergency condenser system (ECS) and the passive auxiliary feed-water system (PAFS). It is essential to analyze and assess the predictive capability of the previous horizontal in-tube condensation models for each flow regime using various experimental data. This study assessed totally 11 condensation models for the stratified flow, one of the main flow regime encountered in the horizontal condenser, with the heat transfer data from the Purdue-PCCS experiment using the multi-dimensional analysis of reactor safety (MARS) code. From the assessments, it was found that the models by Akers and Rosson, Chato, Tandon et al., Sweeney and Chato, and Cavallini et al. (2002) under-predicted the data in the main condensation heat transfer region, on the contrary to this, the models by Rosson and Meyers, Jaster and Kosky, Fujii, Dobson and Chato, and Thome et al. similarly- or over-predicted the data, and especially, Cavallini et al. (2006) model shows good predictive capability for all test conditions. The results of this study can be used importantly to improve the condensation models in thermal hydraulic code, such as RELAP5 or MARS code.

  14. Rapid shelf‐wide cooling response of a stratified coastal ocean to hurricanes

    Science.gov (United States)

    Miles, Travis; Xu, Yi; Kohut, Josh; Schofield, Oscar; Glenn, Scott

    2017-01-01

    Abstract Large uncertainty in the predicted intensity of tropical cyclones (TCs) persists compared to the steadily improving skill in the predicted TC tracks. This intensity uncertainty has its most significant implications in the coastal zone, where TC impacts to populated shorelines are greatest. Recent studies have demonstrated that rapid ahead‐of‐eye‐center cooling of a stratified coastal ocean can have a significant impact on hurricane intensity forecasts. Using observation‐validated, high‐resolution ocean modeling, the stratified coastal ocean cooling processes observed in two U.S. Mid‐Atlantic hurricanes were investigated: Hurricane Irene (2011)—with an inshore Mid‐Atlantic Bight (MAB) track during the late summer stratified coastal ocean season—and Tropical Storm Barry (2007)—with an offshore track during early summer. For both storms, the critical ahead‐of‐eye‐center depth‐averaged force balance across the entire MAB shelf included an onshore wind stress balanced by an offshore pressure gradient. This resulted in onshore surface currents opposing offshore bottom currents that enhanced surface to bottom current shear and turbulent mixing across the thermocline, resulting in the rapid cooling of the surface layer ahead‐of‐eye‐center. Because the same baroclinic and mixing processes occurred for two storms on opposite ends of the track and seasonal stratification envelope, the response appears robust. It will be critical to forecast these processes and their implications for a wide range of future storms using realistic 3‐D coupled atmosphere‐ocean models to lower the uncertainty in predictions of TC intensities and impacts and enable coastal populations to better respond to increasing rapid intensification threats in an era of rising sea levels. PMID:28944132

  15. Decreasing incidence rates of bacteremia

    DEFF Research Database (Denmark)

    Nielsen, Stig Lønberg; Pedersen, C; Jensen, T G

    2014-01-01

    BACKGROUND: Numerous studies have shown that the incidence rate of bacteremia has been increasing over time. However, few studies have distinguished between community-acquired, healthcare-associated and nosocomial bacteremia. METHODS: We conducted a population-based study among adults with first......-time bacteremia in Funen County, Denmark, during 2000-2008 (N = 7786). We reported mean and annual incidence rates (per 100,000 person-years), overall and by place of acquisition. Trends were estimated using a Poisson regression model. RESULTS: The overall incidence rate was 215.7, including 99.0 for community......-acquired, 50.0 for healthcare-associated and 66.7 for nosocomial bacteremia. During 2000-2008, the overall incidence rate decreased by 23.3% from 254.1 to 198.8 (3.3% annually, p incidence rate of community-acquired bacteremia decreased by 25.6% from 119.0 to 93.8 (3.7% annually, p

  16. Price of forest chips decreasing

    International Nuclear Information System (INIS)

    Hakkila, P.

    2001-01-01

    Use of forest chips was studied in 1999 in the national Puuenergia (Wood Energy) research program. Wood combusting heating plants were questioned about are the main reasons restricting the increment of the use of forest chips. Heating plants, which did not use forest chips at all or which used less than 250 m 3 (625 bulk- m 3 ) in 1999 were excluded. The main restrictions for additional use of forest chips were: too high price of forest chips; lack of suppliers and/or uncertainty of deliveries; technical problems of reception and processing of forest chips; insufficiency of boiler output especially in winter; and unsatisfactory quality of chips. The price of forest chips becomes relatively high because wood biomass used for production of forest chips has to be collected from wide area. Heavy equipment has to be used even though small fragments of wood are processed, which increases the price of chips. It is essential for forest chips that the costs can be pressed down because competition with fossil fuels, peat and industrial wood residues is hard. Low market price leads to the situation in which forest owner gets no price of the raw material, the entrepreneurs operate at the limit of profitability and renovation of machinery is difficult, and forest chips suppliers have to sell the chips at prime costs. Price of forest chips has decreased significantly during the past decade. Nominal price of forest chips is now lower than two decades ago. The real price of chips has decreased even more than the nominal price, 35% during the past decade and 20% during the last five years. Chips, made of small diameter wood, are expensive because the price includes the felling costs and harvesting is carried out at thinning lots. Price is especially high if chips are made of delimbed small diameter wood due to increased the work and reduced amount of chips. The price of logging residue chips is most profitable because cutting does not cause additional costs. Recovery of chips is

  17. MUP, CEC-DES, STRADE. Codes for uncertainty propagation, experimental design and stratified random sampling techniques

    International Nuclear Information System (INIS)

    Amendola, A.; Astolfi, M.; Lisanti, B.

    1983-01-01

    The report describes the how-to-use of the codes: MUP (Monte Carlo Uncertainty Propagation) for uncertainty analysis by Monte Carlo simulation, including correlation analysis, extreme value identification and study of selected ranges of the variable space; CEC-DES (Central Composite Design) for building experimental matrices according to the requirements of Central Composite and Factorial Experimental Designs; and, STRADE (Stratified Random Design) for experimental designs based on the Latin Hypercube Sampling Techniques. Application fields, of the codes are probabilistic risk assessment, experimental design, sensitivity analysis and system identification problems

  18. Approximate solutions and error bounds for the wave equation in a stratified ionosphere with turning points

    International Nuclear Information System (INIS)

    Nalesso, G.F.; Jacobson, A.R.

    1991-01-01

    A solution to the problem of a plane electromagnetic wave traveling parallel to a constant magnetic field in a horizontally stratified ionosphere was developed assuming that the permittivity of the medium can be represented as the sum of an unperturbed component and a perturbed component. The method is successfully applied to the case of a linearly varying permittivity of a lossless ionosphere with a superimposed Gaussian perturbing term. The feasibility of applying the method in the presence of an odd number of turning points is discussed. 13 refs

  19. Design of a high-performance rotary stratified-charge research aircraft engine

    Science.gov (United States)

    Jones, C.; Mount, R. E.

    1984-01-01

    The power section for an advanced rotary stratified-charge general aviation engine has been designed under contract to NASA. The single-rotor research engine of 40 cubic-inches displacement (RCI-40), now being procured for test initiation this summer, is targeted for 320 T.O. horse-power in a two-rotor production engine. The research engine is designed for operating on jet-fuel, gasoline or diesel fuel and will be used to explore applicable advanced technologies and to optimize high output performance variables. Design of major components of the engine is described in this paper.

  20. Non-Darcy Mixed Convection in a Doubly Stratified Porous Medium with Soret-Dufour Effects

    Directory of Open Access Journals (Sweden)

    D. Srinivasacharya

    2014-01-01

    Full Text Available This paper presents the nonsimilarity solutions for mixed convection heat and mass transfer along a semi-infinite vertical plate embedded in a doubly stratified fluid saturated porous medium in the presence of Soret and Dufour effects. The flow in the porous medium is described by employing the Darcy-Forchheimer based model. The nonlinear governing equations and their associated boundary conditions are initially cast into dimensionless forms and then solved numerically. The influence of pertinent parameters on dimensionless velocity, temperature, concentration, heat, and mass transfer in terms of the local Nusselt and Sherwood numbers is discussed and presented graphically.

  1. Unsteady natural convection flow past an accelerated vertical plate in a thermally stratified fluid

    Directory of Open Access Journals (Sweden)

    Deka Rudra Kt.

    2009-01-01

    Full Text Available An exact solution to one-dimensional unsteady natural convection flow past an infinite vertical accelerated plate, immersed in a viscous thermally stratified fluid is investigated. Pressure work term and the vertical temperature advection are considered in the thermodynamic energy equation. The dimensionless governing equations are solved by Laplace Transform techniques for the Prandtl number unity. The velocity and temperature profiles as well as the skin-friction and the rate of heat transfer are presented graphically and discussed the effects of the Grashof number Gr, stratification parameter S at various times t.

  2. The optical interface of a photonic crystal: Modeling an opal with a stratified effective index

    OpenAIRE

    Maurin, Isabelle; Moufarej, Elias; Laliotis, Athanasios; Bloch, Daniel

    2014-01-01

    An artificial opal is a compact arrangement of transparent spheres, and is an archetype of a three-dimensional photonic crystal. Here, we describe the optics of an opal using a flexible model based upon a stratified medium whose (effective) index is governed by the opal density in a small planar slice of the opal. We take into account the effect of the substrate and assume a well- controlled number of layers, as it occurs for an opal fabricated by Langmuir-Blodgett deposition. The calculation...

  3. A Case Study of Offshore Advection of Boundary Layer Rolls over a Stably Stratified Sea Surface

    DEFF Research Database (Denmark)

    Svensson, Nina; Sahlée, Erik; Bergström, Hans

    2017-01-01

    originate from boundary layer rolls generated over the convective air above Swedish mainland, also supported by visual satellite images showing the typical signature cloud streets. The simulations indicate that the rolls are advected and maintained at least 30–80 km off the coast, in agreement...... considerably for long times and over large areas in coastal regions. Although boundary layer rolls are a well-studied feature, no previous study has presented results concerning their persistence during situations with advection to a strongly stratified boundary layer. Such conditions are commonly encountered...

  4. Performance of stratified thermal-storage system for Oliver Springs Elementary School. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Reid, R.L.; Bedinger, A.F.G.

    1981-01-01

    A progress report is given on the performance of a stratified thermal storage system coupled with a heat recovery refrigeration machine designed to provide space heating, cooling and service water heating. Water storage tanks utilizing a flexible membrane to resist temperature blending will be used as the thermal storage element. The two design goals of the heat recovery and thermal energy storage system are (1) to minimize the need to purchase energy for space heating and cooling and water heating and (2) to minimize electrical demand. An automatic data acquisition system will be used for system performance and data gathering. Data collection is expected to begin in September, 1981.

  5. Interfacial shear stress in stratified flow in a horizontal rectangular duct

    International Nuclear Information System (INIS)

    Lorencez, C.; Kawaji, M.; Murao, Y.

    1995-01-01

    Interfacial shear stress has been experimentally examined for both cocurrent and countercurrent stratified wavy flows in a horizontal interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress values at high gas flow rates which could be attributed to the assumptions and procedures involved in each method. The interfacial waves and secondary motions were also found to have significant effects on the accuracy of Reynolds stress and turbulence kinetic energy extrapolation methods

  6. Experimental determination and modelling of interface area concentration in horizontal stratified flow

    International Nuclear Information System (INIS)

    Junqua-Moullet, Alexandra

    2003-01-01

    This research thesis concerns the modelling and experimentation of biphasic liquid/gas flows (water/air) while using the two-fluid model, a six-equation model. The author first addresses the modelling of interfacial magnitudes for a known topology (problem of two-fluid model closure, closure relationships for some variables, equation for a given configuration). She reports the development of an equation system for interfacial magnitudes. The next parts deal with experiments and report the study of stratified flows in the THALC experiment, and more particularly the study of the interfacial area concentration and of the liquid velocities in such flows. Results are discussed, as well as their consistency

  7. Mixed convection boundary layer flow over a vertical surface embedded in a thermally stratified porous medium

    International Nuclear Information System (INIS)

    Ishak, Anuar; Nazar, Roslinda; Pop, Ioan

    2008-01-01

    The mixed convection boundary layer flow through a stable stratified porous medium bounded by a vertical surface is investigated. The external velocity and the surface temperature are assumed to vary as x m , where x is measured from the leading edge of the vertical surface and m is a constant. Numerical solutions for the governing Darcy and energy equations are obtained. The results indicate that the thermal stratification significantly affects the surface shear stress as well as the surface heat transfer, besides delays the boundary layer separation

  8. Thermalhydraulic study of a stratified flow in a piping elbow (Application to the model Coufast)

    International Nuclear Information System (INIS)

    Peniguel, C.; Stephan, J.M.

    1992-11-01

    In PWR's, mechanical damages (cracks) have been detected at the internal faces of steam generator feedwater piping and also in dead legs, when thermal stratification occurs. To gain some understanding on these issues, experimental and numerical programs have been set up at EDF. This paper reports a thermalhydraulic study of an elbow geometry under operating conditions leading to the establishment of a stable stratified flow. Results obtained with ESTET (a three dimensional finite differences-finite volume code solving the averaged Navier-Stokes equations) and comparisons with experimental data obtained on COUFAST (an analytical mock up, scale 1 of a French 900-MW PWR steam generator pipe elbow) are shown

  9. Estimation of instantaneous heat transfer coefficients for a direct-injection stratified-charge rotary engine

    Science.gov (United States)

    Lee, C. M.; Addy, H. E.; Bond, T. H.; Chun, K. S.; Lu, C. Y.

    1987-01-01

    The main objective of this report was to derive equations to estimate heat transfer coefficients in both the combustion chamber and coolant pasage of a rotary engine. This was accomplished by making detailed temperature and pressure measurements in a direct-injection stratified-charge rotary engine under a range of conditions. For each sppecific measurement point, the local physical properties of the fluids were calculated. Then an empirical correlation of the coefficients was derived by using a multiple regression program. This correlation expresses the Nusselt number as a function of the Prandtl number and Reynolds number.

  10. Performance and combustion characteristics of direct-injection stratified-charge rotary engines

    Science.gov (United States)

    Nguyen, Hung Lee

    1987-01-01

    Computer simulations of the direct-injection stratified-charge (DISC) Wankel engine have been used to calculate heat release rates and performance and efficiency characteristics of the 1007R engine. Engine pressure data have been used in a heat release analysis to study the effects of heat transfer, leakage, and crevice flows. Predicted engine performance data are compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the Wankel engine with faster combustion, reduced leakage, higher compression ratio, and turbocharging is presented.

  11. Stratified turbulent Bunsen flames: flame surface analysis and flame surface density modelling

    Science.gov (United States)

    Ramaekers, W. J. S.; van Oijen, J. A.; de Goey, L. P. H.

    2012-12-01

    In this paper it is investigated whether the Flame Surface Density (FSD) model, developed for turbulent premixed combustion, is also applicable to stratified flames. Direct Numerical Simulations (DNS) of turbulent stratified Bunsen flames have been carried out, using the Flamelet Generated Manifold (FGM) reduction method for reaction kinetics. Before examining the suitability of the FSD model, flame surfaces are characterized in terms of thickness, curvature and stratification. All flames are in the Thin Reaction Zones regime, and the maximum equivalence ratio range covers 0.1⩽φ⩽1.3. For all flames, local flame thicknesses correspond very well to those observed in stretchless, steady premixed flamelets. Extracted curvature radii and mixing length scales are significantly larger than the flame thickness, implying that the stratified flames all burn in a premixed mode. The remaining challenge is accounting for the large variation in (subfilter) mass burning rate. In this contribution, the FSD model is proven to be applicable for Large Eddy Simulations (LES) of stratified flames for the equivalence ratio range 0.1⩽φ⩽1.3. Subfilter mass burning rate variations are taken into account by a subfilter Probability Density Function (PDF) for the mixture fraction, on which the mass burning rate directly depends. A priori analysis point out that for small stratifications (0.4⩽φ⩽1.0), the replacement of the subfilter PDF (obtained from DNS data) by the corresponding Dirac function is appropriate. Integration of the Dirac function with the mass burning rate m=m(φ), can then adequately model the filtered mass burning rate obtained from filtered DNS data. For a larger stratification (0.1⩽φ⩽1.3), and filter widths up to ten flame thicknesses, a β-function for the subfilter PDF yields substantially better predictions than a Dirac function. Finally, inclusion of a simple algebraic model for the FSD resulted only in small additional deviations from DNS data

  12. Interfacial shear stress in stratified flow in a horizontal rectangular duct

    Energy Technology Data Exchange (ETDEWEB)

    Lorencez, C.; Kawaji, M. [Univ. of Toronto (Canada); Murao, Y. [Tokushima Univ. (Japan)] [and others

    1995-09-01

    Interfacial shear stress has been experimentally examined for both cocurrent and countercurrent stratified wavy flows in a horizontal interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress values at high gas flow rates which could be attributed to the assumptions and procedures involved in each method. The interfacial waves and secondary motions were also found to have significant effects on the accuracy of Reynolds stress and turbulence kinetic energy extrapolation methods.

  13. Turbulent circulation above the surface heat source in a stably stratified environment

    Science.gov (United States)

    Kurbatskii, A. F.; Kurbatskaya, L. I.

    2016-09-01

    The results of the numerical modeling of turbulent structure of the penetrating convection above the urban heat island with a small aspect ratio in a stably stratified medium at rest are presented. The gradient diffusion representations for turbulent momentum and heat fluxes are used, which depend on three parameters — the turbulence kinetic energy, the velocity of its spectral expenditure, and the dispersion of temperature fluctuations. These parameters are found from the closed differential equations of balance in the RANS approach of turbulence description. The distributions of averaged velocity and temperature fields as well as turbulent characteristics agree well with measurement data.

  14. Large-eddy simulation of stratified atmospheric flows with the CFD code Code-Saturne

    International Nuclear Information System (INIS)

    Dall'Ozzo, Cedric

    2013-01-01

    Large-eddy simulation (LES) of the physical processes in the atmospheric boundary layer (ABL) remains a complex subject. LES models have difficulties to capture the evolution of the turbulence in different conditions of stratification. Consequently, LES of the whole diurnal cycle of the ABL including convective situations in daytime and stable situations in the nighttime is seldom documented. The simulation of the stable atmospheric boundary layer which is characterized by small eddies and by weak and sporadic turbulence is especially difficult. Therefore The LES ability to well reproduce real meteorological conditions, particularly in stable situations, is studied with the CFD code developed by EDF R and D, Code-Saturne. The first study consist in validate LES on a quasi-steady state convective case with homogeneous terrain. The influence of the sub-grid-scale models (Smagorinsky model, Germano-Lilly model, Wong-Lilly model and Wall-Adapting Local Eddy-viscosity model) and the sensitivity to the parametrization method on the mean fields, flux and variances are discussed. In a second study, the diurnal cycle of the ABL during Wangara experiment is simulated. The deviation from the measurement is weak during the day, so this work is focused on the difficulties met during the night to simulate the stable atmospheric boundary layer. The impact of the different sub-grid-scale models and the sensitivity to the Smagorinsky constant are been analysed. By coupling radiative forcing with LES, the consequences of infra-red and solar radiation on the nocturnal low level jet and on thermal gradient, close to the surface, are exposed. More, enhancement of the domain resolution to the turbulence intensity and the strong atmospheric stability during the Wangara experiment are analysed. Finally, a study of the numerical oscillations inherent to Code-Saturne is realized in order to decrease their effects. (author) [fr

  15. Rigidity spectrum of Forbush decrease

    International Nuclear Information System (INIS)

    Sakakibara, S.; Munakata, K.; Nagashima, K.

    1985-01-01

    Using data from neutron monitors and muon telescopes at surface and underground stations, the average rigidity spectrum of Forbush decreases (Fds) during the period of 1978-1982 were obtained. Thirty eight Ed-events are classified into two groups, Hard Fd and Soft FD according to size of Fd at the Sakashita station. It is found that a spectral form of a fractional-power type (P to the-gamma sub 1 (P+P sub c) to the -gamma sub2) is more suitable than that of a power-exponential type or of a power type with an upper limiting rigidity. The best fitted spectrum of the fractional-power type is expressed by gamma sub1 = 0.37, gamma sub2 = 0.89 and P subc = 10 GV for Hard Fd and gamma sub1 = 0.77, gamma sub2 = 1.02 and P sub c - 14GV for Soft Fd

  16. Method of decreasing nuclear power

    International Nuclear Information System (INIS)

    Masuda, Hiromi

    1987-01-01

    Purpose: To easily attain the power decreasing in a HWLWR type reactor and improve the reactor safety. Method: The method is applied to a nuclear reactor in which the reactor reactivity is controlled by control rods and liquid posions dissolved in moderators. Means for forecasting the control rod operation amount required for the reactor power down and means for removing liquid poisons in the moderators are provided. The control rod operation amount required for the power down is forecast before the power down and the liquid poisons in the moderators are removed. Then, the control rods are inserted into a deep insertion position to reduce the reactor power. This invention can facilitate easy power down, as well as provide effects of improving the controllability in the usual operation and of avoiding abrupt power down which leads to an improved availability. (Kamimura, M.)

  17. National Coral Reef Monitoring Program: Benthic Images Collected from Stratified Random Sites (StRS) across American Samoa in 2015

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data described here are benthic habitat imagery that result from benthic photo-quadrat surveys conducted along transects at stratified random sites across...

  18. A comparative study of vertical stabilities in the Arabian sea and Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Sastry, J.S.; Rao, D.P.

    Stabilities in the upper 300 m in the Arabian Sea and the Bay of Bengal are computed and presented seasonwise. The water column in the Bay of Bengal is more strongly stratified than that in the Arabian Sea. These studies suggest that the vertical...

  19. Diagnostic accuracy of the STRATIFY clinical prediction rule for falls: A systematic review and meta-analysis

    LENUS (Irish Health Repository)

    Billington, Jennifer

    2012-08-07

    AbstractBackgroundThe STRATIFY score is a clinical prediction rule (CPR) derived to assist clinicians to identify patients at risk of falling. The purpose of this systematic review and meta-analysis is to determine the overall diagnostic accuracy of the STRATIFY rule across a variety of clinical settings.MethodsA literature search was performed to identify all studies that validated the STRATIFY rule. The methodological quality of the studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool. A STRATIFY score of ≥2 points was used to identify individuals at higher risk of falling. All included studies were combined using a bivariate random effects model to generate pooled sensitivity and specificity of STRATIFY at ≥2 points. Heterogeneity was assessed using the variance of logit transformed sensitivity and specificity.ResultsSeventeen studies were included in our meta-analysis, incorporating 11,378 patients. At a score ≥2 points, the STRATIFY rule is more useful at ruling out falls in those classified as low risk, with a greater pooled sensitivity estimate (0.67, 95% CI 0.52–0.80) than specificity (0.57, 95% CI 0.45 – 0.69). The sensitivity analysis which examined the performance of the rule in different settings and subgroups also showed broadly comparable results, indicating that the STRATIFY rule performs in a similar manner across a variety of different ‘at risk’ patient groups in different clinical settings.ConclusionThis systematic review shows that the diagnostic accuracy of the STRATIFY rule is limited and should not be used in isolation for identifying individuals at high risk of falls in clinical practice.

  20. The vulnerability of oil collection pipelines to corrosion under conditions of stratified oil-water emulsion

    Energy Technology Data Exchange (ETDEWEB)

    Marichev, F N; Chernobay, L A; Teterina, O P; Yarmizin, V G

    1980-01-01

    Problems with oil industry equipment and pipeline corrosion have recently highlighted the problems of increased water content in oil and the presence of biogenic hydrogen sulphide in petroleum matter. These findings underscore the importance of taking these problems into consideration when formulating long-term production plans. A study of pipeline corrosion and its causes, as well as other factors, has permitted researchers to correlate hydrodynamic parameters for gas-fluid transportability and structural contour flows. The water phase simultaneously carries corrosion-active ions of dissolved hydrogen sulphide and material which interact to corrode metal in the lower sections of pipelines. In order to determine the susceptibility of pipelines to corrosion, it is necessary to establish the presence of stratified fluids in oil and water as well as the gas-fluid flow. Analysis has shown that those sections with stratified emulsion could be identified and that it is necessary to disclose the pipeline's ability to withstand such conditions. The proper selection of transport parameters permits the technological protection of the oil collection pipelines. Partially as a result of the increased flow speed guaranteeing an emulsion flow regime for the gas-water-oil flow, it was found that the operational service-life of pipelines could be prolonged by a reduction of corrosion in oil collection pipelines.

  1. DCOMP Award Lecture (Metropolis): A 3D Spectral Anelastic Hydrodynamic Code for Shearing, Stratified Flows

    Science.gov (United States)

    Barranco, Joseph

    2006-03-01

    We have developed a three-dimensional (3D) spectral hydrodynamic code to study vortex dynamics in rotating, shearing, stratified systems (eg, the atmosphere of gas giant planets, protoplanetary disks around newly forming protostars). The time-independent background state is stably stratified in the vertical direction and has a unidirectional linear shear flow aligned with one horizontal axis. Superposed on this background state is an unsteady, subsonic flow that is evolved with the Euler equations subject to the anelastic approximation to filter acoustic phenomena. A Fourier-Fourier basis in a set of quasi-Lagrangian coordinates that advect with the background shear is used for spectral expansions in the two horizontal directions. For the vertical direction, two different sets of basis functions have been implemented: (1) Chebyshev polynomials on a truncated, finite domain, and (2) rational Chebyshev functions on an infinite domain. Use of this latter set is equivalent to transforming the infinite domain to a finite one with a cotangent mapping, and using cosine and sine expansions in the mapped coordinate. The nonlinear advection terms are time integrated explicitly, whereas the Coriolis force, buoyancy terms, and pressure/enthalpy gradient are integrated semi- implicitly. We show that internal gravity waves can be damped by adding new terms to the Euler equations. The code exhibits excellent parallel performance with the Message Passing Interface (MPI). As a demonstration of the code, we simulate vortex dynamics in protoplanetary disks and the Kelvin-Helmholtz instability in the dusty midplanes of protoplanetary disks.

  2. Measurements of density profile evolution during the stably-stratified filling of an open enclosure

    International Nuclear Information System (INIS)

    Tarawneh, Constantine M.; Homan, K.O.

    2008-01-01

    The stably-stratified filling of an open enclosure produces an interfacial gradient layer which is transported through the enclosure with the bulk flow. The evolution of this interfacial layer is strongly time-dependent and is driven by the nature of the interaction between the internal gravity waves and the inlet-driven interfacial shear. Measurements of density profile evolution have been completed for a rectangular enclosure with a single corner inlet and density variation produced by saline concentration. This system serves as a mass transfer analog to large-scale, thermally-stratified energy storage devices, preserving dynamic similitude in a laboratory-scale system. The experiments covered jet Reynolds numbers of 200-2200 and Froude numbers of 0.06-0.6 in an enclosure with a width 23 times the jet inlet height. The density profiles are seen to be strongly asymmetric and exhibit growth rates significantly different than due to simple one-dimensional molecular diffusion. In addition, shadowgraph and hydrogen bubble visualizations of the density and velocity fields in the gradient layer show the persistence of complex multi-dimensional flow structure even at relatively late stages of the filling process when the gradient layer has been transported well away from the enclosure inlet. The evolution of the vertical density profile has been compared quantitatively to a quasi one-dimensional model based upon empirical diffusivity coefficients

  3. Effects of unstratified and centre-stratified randomization in multi-centre clinical trials.

    Science.gov (United States)

    Anisimov, Vladimir V

    2011-01-01

    This paper deals with the analysis of randomization effects in multi-centre clinical trials. The two randomization schemes most often used in clinical trials are considered: unstratified and centre-stratified block-permuted randomization. The prediction of the number of patients randomized to different treatment arms in different regions during the recruitment period accounting for the stochastic nature of the recruitment and effects of multiple centres is investigated. A new analytic approach using a Poisson-gamma patient recruitment model (patients arrive at different centres according to Poisson processes with rates sampled from a gamma distributed population) and its further extensions is proposed. Closed-form expressions for corresponding distributions of the predicted number of the patients randomized in different regions are derived. In the case of two treatments, the properties of the total imbalance in the number of patients on treatment arms caused by using centre-stratified randomization are investigated and for a large number of centres a normal approximation of imbalance is proved. The impact of imbalance on the power of the study is considered. It is shown that the loss of statistical power is practically negligible and can be compensated by a minor increase in sample size. The influence of patient dropout is also investigated. The impact of randomization on predicted drug supply overage is discussed. Copyright © 2010 John Wiley & Sons, Ltd.

  4. An experimental study on quenching of a radially stratified heated porous bed

    International Nuclear Information System (INIS)

    Nayak, Arun K.; Sehgal, Bal Raj; Stepanyan, Armen V.

    2006-01-01

    The quenching characteristics of a volumetrically-heated particulate bed composed of radially stratified sand layers were investigated experimentally in the POMECO facility. The sand bed simulates the corium particulate debris bed which is formed when the molten corium released from the vessel fragments in water and deposits on the cavity floor during a postulated severe accident in a light water reactor (LWR). The electrically-heated bed was quenched by water from a water column established over top of it, and later also with water coming from its bottom, which was circulating from the water overlayer through downcomers. A series of experiments were conducted to reveal the effects of the size of downcomers, and their locations in the bed, on the quenching characteristics of the radially stratified debris beds. The downcomers were found to significantly increase the bed quenching rate. To simulate the non-condensable gases generated during the MCCI, air and argon were injected from the bottom of the bed at different flow rates. The effects of gas flow rate and its properties on the quenching behaviour were observed. The results indicate that the non-condensable gas flows reduce the quenching rate significantly. The gas properties also affect the quenching characteristics

  5. Characterizing the performance of an affordable, multichannel conductivity probe for density measurements in stratified flows

    Science.gov (United States)

    Subramanian, Balaji; Carminati, Marco; Luzzatto-Fegiz, Paolo

    2017-11-01

    In stratified flows, conductivity (combined with temperature) is often used to measure density. The conductivity probes typically used can resolve very fine spatial scales, but on the downside they are fragile, expensive, sensitive to environmental noise and have only single channel capability. Recently a low-cost, robust, arduino-based probe called Conduino was developed, which can be valuable in a wide range of applications where resolving extremely small spatial scales is not needed. This probe uses micro-USB connectors as actual conductivity sensors with a custom designed electronic board for simultaneous acquisition from multiple probes, with conductivity resolution comparable to commercially available PME conductivity probe. A detailed assessment of performance of this Conduino probe is described here. To establish time response and sensitivity as a function of electrode geometry, we build a variety of shapes for different kinds of applications, with tip spacing ranging from 0.5-2.5 mm, and with electrode length ranging from 2.3-6 mm. We set up a two-layer density profile and traverse it rapidly, yielding a time response comparable to PME. The Conduino's multi-channel capability is used to operate probe arrays, which helps to construct density fields in stratified flows.

  6. Risk Factors for Emergency Department Short Time Readmission in Stratified Population

    Directory of Open Access Journals (Sweden)

    Ariadna Besga

    2015-01-01

    Full Text Available Background. Emergency department (ED readmissions are considered an indicator of healthcare quality that is particularly relevant in older adults. The primary objective of this study was to identify key factors for predicting patients returning to the ED within 30 days of being discharged. Methods. We analysed patients who attended our ED in June 2014, stratified into four groups based on the Kaiser pyramid. We collected data on more than 100 variables per case including demographic and clinical characteristics and drug treatments. We identified the variables with the highest discriminating power to predict ED readmission and constructed classifiers using machine learning methods to provide predictions. Results. Classifier performance distinguishing between patients who were and were not readmitted (within 30 days, in terms of average accuracy (AC. The variables with the greatest discriminating power were age, comorbidity, reasons for consultation, social factors, and drug treatments. Conclusions. It is possible to predict readmissions in stratified groups with high accuracy and to identify the most important factors influencing the event. Therefore, it will be possible to develop interventions to improve the quality of care provided to ED patients.

  7. Cross-cultural adaptation of the STRATIFY tool in detecting and predicting risk of falling.

    Science.gov (United States)

    Enríquez de Luna-Rodríguez, Margarita; Aranda-Gallardo, Marta; Canca-Sánchez, José Carlos; Vazquez-Blanco, M José; Moya-Suárez, Ana Belén; Morales-Asencio, José Miguel

    To adapt to Spanish language the STRATIFY tool for clinical use in the Spanish-speaking World. A multicenter, 2 care settings cross-sectional study cultural adaptation study in acute care hospitals and nursing homes was performed in Andalusia during 2014. The adaptation process was divided into 4 stages: translation, back-translation, equivalence between the 2 back-translations and piloting of the Spanish version, thus obtaining the final version. The validity of appearance, content validity and the time required to complete the scale were taken into account. For analysis, the median, central tendency and dispersion of scores, the interquartile range, and the interquartile deviation for the possible variability in responses it was calculated. Content validity measured by content validity index reached a profit of 1. For the validity aspect the clarity and comprehensibility of the questions were taken into account. Of the 5 questions of the instrument, 2 had a small disagreement solved with the introduction of an explanatory phrase to achieve conceptual equivalence. Median both questions were equal or superior to 5. The average time for completion of the scale was less than 3 minutes. The process of adaptation to Spanish of STRATIFY has led to a semantic version and culturally equivalent to the original for easy filling and understanding for use in the Spanish-speaking world. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.

  8. Multi-Instrument Observations of Prolonged Stratified Wind Layers at Iqaluit, Nunavut

    Science.gov (United States)

    Mariani, Zen; Dehghan, Armin; Gascon, Gabrielle; Joe, Paul; Hudak, David; Strawbridge, Kevin; Corriveau, Julien

    2018-02-01

    Data collected between October 2015 and May 2016 at Environment and Climate Change Canada's Iqaluit research site (64°N, 69°W) have revealed a high frequency (40% of all days for which observations were available) of stratified wind layer events that occur from near the surface up to about 7.2 km above sea level. These stratified wind layers are clearly visible as wind shifts (90 to 180°) with height in range-height indicator scans from the Doppler lidar and Ka-band radar and in wind direction profiles from the Doppler lidar and radiosonde. During these events, the vertical structure of the flow appears to be a stack of 4 to 10 layers ranging in vertical width from 0.1 to 4.4 km. The stratification events that were observed occurred predominantly (81%) during light precipitation and lasted up to 27.5 h. The integrated measurement platforms at Iqaluit permitted continuous observations of the evolution of stratification events in different meteorological conditions.

  9. Fixed-location hydroacoustic monitoring designs for estimating fish passage using stratified random and systematic sampling

    International Nuclear Information System (INIS)

    Skalski, J.R.; Hoffman, A.; Ransom, B.H.; Steig, T.W.

    1993-01-01

    Five alternate sampling designs are compared using 15 d of 24-h continuous hydroacoustic data to identify the most favorable approach to fixed-location hydroacoustic monitoring of salmonid outmigrants. Four alternative aproaches to systematic sampling are compared among themselves and with stratified random sampling (STRS). Stratifying systematic sampling (STSYS) on a daily basis is found to reduce sampling error in multiday monitoring studies. Although sampling precision was predictable with varying levels of effort in STRS, neither magnitude nor direction of change in precision was predictable when effort was varied in systematic sampling (SYS). Furthermore, modifying systematic sampling to include replicated (e.g., nested) sampling (RSYS) is further shown to provide unbiased point and variance estimates as does STRS. Numerous short sampling intervals (e.g., 12 samples of 1-min duration per hour) must be monitored hourly using RSYS to provide efficient, unbiased point and interval estimates. For equal levels of effort, STRS outperformed all variations of SYS examined. Parametric approaches to confidence interval estimates are found to be superior to nonparametric interval estimates (i.e., bootstrap and jackknife) in estimating total fish passage. 10 refs., 1 fig., 8 tabs

  10. [Study of spatial stratified sampling strategy of Oncomelania hupensis snail survey based on plant abundance].

    Science.gov (United States)

    Xun-Ping, W; An, Z

    2017-07-27

    Objective To optimize and simplify the survey method of Oncomelania hupensis snails in marshland endemic regions of schistosomiasis, so as to improve the precision, efficiency and economy of the snail survey. Methods A snail sampling strategy (Spatial Sampling Scenario of Oncomelania based on Plant Abundance, SOPA) which took the plant abundance as auxiliary variable was explored and an experimental study in a 50 m×50 m plot in a marshland in the Poyang Lake region was performed. Firstly, the push broom surveyed data was stratified into 5 layers by the plant abundance data; then, the required numbers of optimal sampling points of each layer through Hammond McCullagh equation were calculated; thirdly, every sample point in the line with the Multiple Directional Interpolation (MDI) placement scheme was pinpointed; and finally, the comparison study among the outcomes of the spatial random sampling strategy, the traditional systematic sampling method, the spatial stratified sampling method, Sandwich spatial sampling and inference and SOPA was performed. Results The method (SOPA) proposed in this study had the minimal absolute error of 0.213 8; and the traditional systematic sampling method had the largest estimate, and the absolute error was 0.924 4. Conclusion The snail sampling strategy (SOPA) proposed in this study obtains the higher estimation accuracy than the other four methods.

  11. Experimental investigation and CFD simulation of horizontal stratified two-phase flow phenomena

    International Nuclear Information System (INIS)

    Vallee, Christophe; Hoehne, Thomas; Prasser, Horst-Michael; Suehnel, Tobias

    2008-01-01

    For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Dresden-Rossendorf (FZD). The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronised with the high-speed camera system. CFD post-test simulations of stratified flows were performed using the code ANSYS CFX. The Euler-Euler two fluid model with the free surface option was applied on grids of minimum 4 x 10 5 control volumes. The turbulence was modelled separately for each phase using the k-ω-based shear stress transport (SST) turbulence model. The results compare very well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow

  12. Experimental investigation and CFD simulation of horizontal stratified two-phase flow phenomena

    International Nuclear Information System (INIS)

    Vallee, Christophe; Hohne, Thomas; Prasser, Horst-Michael; Suhnel, Tobias

    2007-01-01

    For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Rossendorf. The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronized with the high-speed camera system. CFD post test simulations of stratified flows were performed using the code ANSYS CFX. The Euler- Euler two fluid model with the free surface option was applied on grids of minimum 4.10 5 control volumes. The turbulence was modelled separately for each phase using the k-ω based shear stress transport (SST) turbulence model. The results compare very well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow. (authors)

  13. Experimental investigation and CFD simulation of horizontal stratified two-phase flow phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Vallee, Christophe [Forschungszentrum Dresden-Rossendorf e.V., Dresden (Germany)], E-mail: c.vallee@fzd.de; Hoehne, Thomas; Prasser, Horst-Michael; Suehnel, Tobias [Forschungszentrum Dresden-Rossendorf e.V., Dresden (Germany)

    2008-03-15

    For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Dresden-Rossendorf (FZD). The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronised with the high-speed camera system. CFD post-test simulations of stratified flows were performed using the code ANSYS CFX. The Euler-Euler two fluid model with the free surface option was applied on grids of minimum 4 x 10{sup 5} control volumes. The turbulence was modelled separately for each phase using the k-{omega}-based shear stress transport (SST) turbulence model. The results compare very well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow.

  14. Mixing process of a binary gas in a density stratified layer

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Tetsuaki [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment

    1997-09-01

    This study is to investigate the effect of natural convection on the mixing process by molecular diffusion in a vertical stratified layer of a binary fluid. There are many experimental and analytical studies on natural convection in the vertical fluid layer. However, there are few studies on natural convection with molecular diffusion in the vertical stratified layer of a binary gas. Experimental study has been performed on the combined phenomena of molecular diffusion and natural convection in a binary gas system to investigate the mixing process of the binary gas in a vertical slot consisting of one side heated and the other side cooled. The range of Rayleigh number based on the slot width was about 0 < Ra{sub d} < 7.5 x 10{sup 4}. The density change of the gas mixture and the temperature distribution in the slot was obtained and the mixing process when the heavier gas ingress into the vertical slot filled with the lighter gas from the bottom side of the slot was discussed. The experimental results showed that the mixing process due to molecular diffusion was affected significantly by the natural convection induced by the slightly temperature difference between both vertical walls even if a density difference by the binary gas is larger than that by the temperature difference. (author). 81 refs.

  15. A Case Study of Offshore Advection of Boundary Layer Rolls over a Stably Stratified Sea Surface

    Directory of Open Access Journals (Sweden)

    Nina Svensson

    2017-01-01

    Full Text Available Streaky structures of narrow (8-9 km high wind belts have been observed from SAR images above the Baltic Sea during stably stratified conditions with offshore winds from the southern parts of Sweden. Case studies using the WRF model and in situ aircraft observations indicate that the streaks originate from boundary layer rolls generated over the convective air above Swedish mainland, also supported by visual satellite images showing the typical signature cloud streets. The simulations indicate that the rolls are advected and maintained at least 30–80 km off the coast, in agreement with the streaks observed by the SAR images. During evening when the convective conditions over land diminish, the streaky structures over the sea are still seen in the horizontal wind field; however, the vertical component is close to zero. Thus advected feature from a land surface can affect the wind field considerably for long times and over large areas in coastal regions. Although boundary layer rolls are a well-studied feature, no previous study has presented results concerning their persistence during situations with advection to a strongly stratified boundary layer. Such conditions are commonly encountered during spring in coastal regions at high latitudes.

  16. LES of stratified-wavy flows using novel near-interface treatment

    Science.gov (United States)

    Karnik, Aditya; Kahouadji, Lyes; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Matar, Omar K.

    2017-11-01

    The pressure drop in horizontal stratified wavy flows is influenced by interfacial shear stress. The near-interface behavior of the lighter phase is akin to that near a moving wall. We employ a front-tracking code, Blue, to simulate and capture the near-interface behaviour of both phases. Blue uses a modified Smagorinsky LES model incorporating a novel near-interface treatment for the sub-grid viscosity, which is influenced by damping due to the wall-like interface, and enhancement of the turbulent kinetic energy (TKE) due to the interfacial waves. Simulations are carried out for both air-water and oil-water stratified configurations to demonstrate the applicability of the present method. The mean velocities and tangential Reynolds stresses are compared with experiments for both configurations. At the higher Re, the waves penetrate well into the buffer region of the boundary layer above the interface thus altering its dynamics. Previous attempts to capture the secondary structures associated with such flows using RANS or standard LES methodologies have been unsuccessful. The ability of the present method to reproduce these structures is due to the correct estimation of the near-interface TKE governing energy transfer from the normal to tangential directions. EPSRC, UK, MEMPHIS program Grant (EP/K003976/1), RAEng Research Chair (OKM).

  17. Monitoring oil persistence on beaches : SCAT versus stratified random sampling designs

    International Nuclear Information System (INIS)

    Short, J.W.; Lindeberg, M.R.; Harris, P.M.; Maselko, J.M.; Pella, J.J.; Rice, S.D.

    2003-01-01

    In the event of a coastal oil spill, shoreline clean-up assessment teams (SCAT) commonly rely on visual inspection of the entire affected area to monitor the persistence of the oil on beaches. Occasionally, pits are excavated to evaluate the persistence of subsurface oil. This approach is practical for directing clean-up efforts directly following a spill. However, sampling of the 1989 Exxon Valdez oil spill in Prince William Sound 12 years later has shown that visual inspection combined with pit excavation does not offer estimates of contaminated beach area of stranded oil volumes. This information is needed to statistically evaluate the significance of change with time. Assumptions regarding the correlation of visually-evident surface oil and cryptic subsurface oil are usually not evaluated as part of the SCAT mandate. Stratified random sampling can avoid such problems and could produce precise estimates of oiled area and volume that allow for statistical assessment of major temporal trends and the extent of the impact. The 2001 sampling of the shoreline of Prince William Sound showed that 15 per cent of surface oil occurrences were associated with subsurface oil. This study demonstrates the usefulness of the stratified random sampling method and shows how sampling design parameters impact statistical outcome. Power analysis based on the study results, indicate that optimum power is derived when unnecessary stratification is avoided. It was emphasized that sampling effort should be balanced between choosing sufficient beaches for sampling and the intensity of sampling

  18. Transition of Gas-Liquid Stratified Flow in Oil Transport Pipes

    Directory of Open Access Journals (Sweden)

    D. Lakehal

    2011-12-01

    Full Text Available Large-Scale Simulation results of the transition of a gas-liquid stratified flow to slug flow regime in circular 3D oil transport pipes under turbulent flow conditions expressed. Free surface flow in the pipe is treated using the Level Set method. Turbulence is approached via the LES and VLES methodologies extended to interfacial two-phase flows. It is shown that only with the Level Set method the flow transition can be accurately predicted, better than with the two-fluid phase-average model. The transition from stratified to slug flow is found to be subsequent to the merging of the secondary wave modes created by the action of gas shear (short waves with the first wave mode (high amplitude long wave. The model is capable of predicting global flow features like the onset of slugging and slug speed. In the second test case, the model predicts different kinds of slugs, the so-called operating slugs formed upstream that fill entirely the pipe with water slugs of length scales of the order of 2-4 D, and lower size (1-1.5 D disturbance slugs, featuring lower hold-up (0.8-0.9. The model predicts well the frequency of slugs. The simulations revealed important parameter effects on the results, such as two-dimensionality, pipe length, and water holdup.

  19. Evaluation of a Stratified National Breast Screening Program in the United Kingdom : An Early Model-Based Cost-Effectiveness Analysis

    NARCIS (Netherlands)

    Gray, Ewan; Donten, Anna; Karssemeijer, Nico; van Gils, Carla; Evans, D. Gareth R.; Astley, Sue; Payne, Katherine

    Objectives: To identify the incremental costs and consequences of stratified national breast screening programs (stratified NBSPs) and drivers of relative cost-effectiveness. Methods: A decision-analytic model (discrete event simulation) was conceptualized to represent four stratified NBSPs (risk 1,

  20. Evaluation of a Stratified National Breast Screening Program in the United Kingdom: An Early Model-Based Cost-Effectiveness Analysis

    NARCIS (Netherlands)

    Gray, E.; Donten, A.; Karssemeijer, N.; Gils, C. van; Evans, D.G.; Astley, S.; Payne, K.

    2017-01-01

    OBJECTIVES: To identify the incremental costs and consequences of stratified national breast screening programs (stratified NBSPs) and drivers of relative cost-effectiveness. METHODS: A decision-analytic model (discrete event simulation) was conceptualized to represent four stratified NBSPs (risk 1,

  1. Fluvial modulation of hydrodynamics and salt transport in a highly stratified estuary

    Directory of Open Access Journals (Sweden)

    Carla de Abreu D'Aquino

    2010-06-01

    Full Text Available An oceanographic campaign was conducted in the Araranguá river estuary during the period from May 11th to 13th of 2006 in order to produce a first hydrographic characterization of this system. The campaign was carried out during the spring tide period, and coincidentally after an intense rain event in the region which produced a peak in river discharge. Water level, currents and salinity time series were recorded hourly during a 50-hour period, at a site nearly 7 km upstream from the estuarine mouth. Two longitudinal distributions of salinity along the estuary were also recorded. The hydrographic data time-series were used to compute the advective salt flux in order to investigate the changes in the transport terms as a function of the change in discharge. The results showed that the estuarine structure was strongly modulated by the river discharge. The drop in water level of about 0.5 m during the first 24 hours was directly related to the ebb phase of the river flood. The water column was highly stratified throughout the period, therefore the stratification increased during the last 24 hours. The currents were stronger, ebbing and uni-directional at the beginning and became weaker and bidirectional as the water level went down, assuming a tidal pattern. The total salt transport in the first 25 hours was of -13.6 kg.m-1.s-1 (seawards, decreasing to 3 Kg.m-1.s-1 during the last 25 hours (landwards. It was also noticeable that the pH in the estuary, recorded together with the salinity, was around 5, showing that the water quality in the estuary is affected by the coal mining activity in the hydrographic basin.Uma campanha oceanográfica foi realizada no estuário do rio Araranguá durante o período de 11 e 13 de maio de 2006, objetivando fazer uma primeira caracterização hidrográfica do sistema. A campanha foi realizada em condição de maré de sizígia, e coincidentemente após um evento de chuvas intensas na região que produziu um pico

  2. Investigation and mitigation of condensation induced water hammer by stratified flow experiments

    Science.gov (United States)

    Kadakia, Hiral J.

    This research primarily focuses on the possibility of using stratified flow in preventing an occurrence of condensation induced water hammer (CIWH) in horizontal pipe involving steam and subcooled water. A two-phase flow loop simulating the passive safety systems of an advanced light water reactor was constructed and a series of stratified flow experiments were carried out involving a system of subcooled water, saturated water, and steam. Special instruments were designed to measure steam flow rate and subcooled liquid velocity. These experiments showed that when flow field conditions meet certain criteria CIWH does occur. Flow conditions used in experiments were typically observed in passive safety systems of an advanced light water cooled reactor. This research summarizes a) literature research and other experimental data that signify an occurrence of CIWH, b) experiments in an effort to show an occurrence of CIWH and the ability to prevent CIWH, c) qualitative and quantitative results to underline the mechanism of CIWH, d) experiments that show CIWH can be prevented under certain conditions, and e) guidelines for the safe operating conditions. Based on initial experiment results it was observed that Bernoulli's effect can play an important role in wave formation and instability. A separate effect table top experiment was constructed with plexi-glass. A series of entrance effect tests and stratified experiments were carried out with different fluids to study wave formation and wave bridging. Special test series experiments were carried out to investigate the presence of a saturated layer. The effect of subcooled water and steam flow on wedge length and depth were recorded. These experiments helped create a model which calculates wedge and depth of wedge for a given condition of steam and subcooled water. A very good comparison between the experiment results and the model was obtained. These experiments also showed that the presence of saturated layer can mitigate

  3. Plutonium inventories for stabilization and stabilized materials

    Energy Technology Data Exchange (ETDEWEB)

    Williams, A.K.

    1996-05-01

    The objective of the breakout session was to identify characteristics of materials containing plutonium, the need to stabilize these materials for storage, and plans to accomplish the stabilization activities. All current stabilization activities are driven by the Defense Nuclear Facilities Safety Board Recommendation 94-1 (May 26, 1994) and by the recently completed Plutonium ES&H Vulnerability Assessment (DOE-EH-0415). The Implementation Plan for accomplishing stabilization of plutonium-bearing residues in response to the Recommendation and the Assessment was published by DOE on February 28, 1995. This Implementation Plan (IP) commits to stabilizing problem materials within 3 years, and stabilizing all other materials within 8 years. The IP identifies approximately 20 metric tons of plutonium requiring stabilization and/or repackaging. A further breakdown shows this material to consist of 8.5 metric tons of plutonium metal and alloys, 5.5 metric tons of plutonium as oxide, and 6 metric tons of plutonium as residues. Stabilization of the metal and oxide categories containing greater than 50 weight percent plutonium is covered by DOE Standard {open_quotes}Criteria for Safe Storage of Plutonium Metals and Oxides{close_quotes} December, 1994 (DOE-STD-3013-94). This standard establishes criteria for safe storage of stabilized plutonium metals and oxides for up to 50 years. Each of the DOE sites and contractors with large plutonium inventories has either started or is preparing to start stabilization activities to meet these criteria.

  4. Trapped particle stability for the kinetic stabilizer

    Science.gov (United States)

    Berk, H. L.; Pratt, J.

    2011-08-01

    A kinetically stabilized axially symmetric tandem mirror (KSTM) uses the momentum flux of low-energy, unconfined particles that sample only the outer end-regions of the mirror plugs, where large favourable field-line curvature exists. The window of operation is determined for achieving magnetohydrodynamic (MHD) stability with tolerable energy drain from the kinetic stabilizer. Then MHD stable systems are analysed for stability of the trapped particle mode. This mode is characterized by the detachment of the central-cell plasma from the kinetic-stabilizer region without inducing field-line bending. Stability of the trapped particle mode is sensitive to the electron connection between the stabilizer and the end plug. It is found that the stability condition for the trapped particle mode is more constraining than the stability condition for the MHD mode, and it is challenging to satisfy the required power constraint. Furthermore, a severe power drain may arise from the necessary connection of low-energy electrons in the kinetic stabilizer to the central region.

  5. A mechanically enhanced hybrid nano-stratified barrier with a defect suppression mechanism for highly reliable flexible OLEDs.

    Science.gov (United States)

    Jeong, Eun Gyo; Kwon, Seonil; Han, Jun Hee; Im, Hyeon-Gyun; Bae, Byeong-Soo; Choi, Kyung Cheol

    2017-05-18

    Understanding the mechanical behaviors of encapsulation barriers under bending stress is important when fabricating flexible organic light-emitting diodes (FOLEDs). The enhanced mechanical characteristics of a nano-stratified barrier were analyzed based on a defect suppression mechanism, and then experimentally demonstrated. Following the Griffith model, naturally-occurring cracks, which were caused by Zn etching at the interface of the nano-stratified structure, can curb the propagation of defects. Cross-section images after bending tests provided remarkable evidence to support the existence of a defect suppression mechanism. Many visible cracks were found in a single Al 2 O 3 layer, but not in the nano-stratified structure, due to the mechanism. The nano-stratified structure also enhanced the barrier's physical properties by changing the crystalline phase of ZnO. In addition, experimental results demonstrated the effect of the mechanism in various ways. The nano-stratified barrier maintained a low water vapor transmission rate after 1000 iterations of a 1 cm bending radius test. Using this mechanically enhanced hybrid nano-stratified barrier, FOLEDs were successfully encapsulated without losing mechanical or electrical performance. Finally, comparative lifetime measurements were conducted to determine reliability. After 2000 hours of constant current driving and 1000 iterations with a 1 cm bending radius, the FOLEDs retained 52.37% of their initial luminance, which is comparable to glass-lid encapsulation, with 55.96% retention. Herein, we report a mechanically enhanced encapsulation technology for FOLEDs using a nano-stratified structure with a defect suppression mechanism.

  6. Sensitivity and inversion of full seismic waveforms in stratified porous medium; Sensibilite et inversion de formes d'ondes completes en milieu poreux stratifie

    Energy Technology Data Exchange (ETDEWEB)

    Barros, L. de

    2007-12-15

    Characterization of porous media parameters, and particularly the porosity, permeability and fluid properties are very useful in many applications (hydrologic, natural hazards or oil industry). The aim of my research is to evaluate the possibility to determine these properties from the full seismic wave fields. First, I am interested in the useful parameters and the specific properties of the seismic waves in the poro-elastic theory, often called Biot (1956) theory. I then compute seismic waves propagation in fluid saturated stratified porous media with a reflectivity method coupled with the discrete wavenumber integration method. I first used this modeling to study the possibilities to determine the carbon dioxide concentration and localization thanks to the reflected P-waves in the case of the deep geological storage of Sleipner (North Sea). The sensitivity of the seismic response to the poro-elastic parameters are then generalized by the analytical computation of the Frechet derivatives which are expressed in terms of the Green's functions of the unperturbed medium. The numerical tests show that the porosity and the consolidation are the main parameters to invert. The sensitivity operators are then introduced in a inversion algorithm based on iterative modeling of the full waveform. The classical algorithm of generalized least-square inverse problem is solved by the quasi-Newton technique (Tarantola, 1984). The inversion of synthetic data show that we can invert for the porosity and the fluid and solid parameters (densities and mechanical modulus, or volume rate of fluid and mineral) can be correctly rebuilt if the other parameters are well known. However, the strong seismic coupling of the porous parameters leads to difficulties to invert simultaneously for several parameters. One way to get round these difficulties is to use additional information and invert for one single parameter for the fluid properties (saturating rate) or for the lithology. An other

  7. Doubly stratified MHD tangent hyperbolic nanofluid flow due to permeable stretched cylinder

    Science.gov (United States)

    Nagendramma, V.; Leelarathnam, A.; Raju, C. S. K.; Shehzad, S. A.; Hussain, T.

    2018-06-01

    An investigation is exhibited to analyze the presence of heat source and sink in doubly stratified MHD incompressible tangent hyperbolic fluid due to stretching of cylinder embedded in porous space under nanoparticles. To develop the mathematical model of tangent hyperbolic nanofluid, movement of Brownian and thermophoretic are accounted. The established equations of continuity, momentum, thermal and solutal boundary layers are reassembled into sets of non-linear expressions. These assembled expressions are executed with the help of Runge-Kutta scheme with MATLAB. The impacts of sundry parameters are illustrated graphically and the engineering interest physical quantities like skin friction, Nusselt and Sherwood number are examined by computing numerical values. It is clear that the power-law index parameter and curvature parameter shows favorable effect on momentum boundary layer thickness whereas Weissennberg number reveals inimical influence.

  8. Interactive Fuzzy Goal Programming approach in multi-response stratified sample surveys

    Directory of Open Access Journals (Sweden)

    Gupta Neha

    2016-01-01

    Full Text Available In this paper, we applied an Interactive Fuzzy Goal Programming (IFGP approach with linear, exponential and hyperbolic membership functions, which focuses on maximizing the minimum membership values to determine the preferred compromise solution for the multi-response stratified surveys problem, formulated as a Multi- Objective Non Linear Programming Problem (MONLPP, and by linearizing the nonlinear objective functions at their individual optimum solution, the problem is approximated to an Integer Linear Programming Problem (ILPP. A numerical example based on real data is given, and comparison with some existing allocations viz. Cochran’s compromise allocation, Chatterjee’s compromise allocation and Khowaja’s compromise allocation is made to demonstrate the utility of the approach.

  9. REFLECT: a program to integrate the wave equation through a plane stratified plasma

    International Nuclear Information System (INIS)

    Greene, J.W.

    1975-01-01

    A program was developed to integrate the wave equation through a plane stratified plasma with a general density distribution. The reflection and transmission of a plane wave are computed as a function of the angle of incidence. The polarization of the electric vector is assumed to be perpendicular to the plane of incidence. The model for absorption by classical inverse bremsstrahlung avoids the improper extrapolation of underdense formulae that are singular at the plasma critical surface. Surprisingly good agreement with the geometric-optics analysis of a linear layer was found. The system of ordinary differential equations is integrated by the variable-step, variable-order Adams method in the Lawrence Livermore Laboratory Gear package. Parametric studies of the absorption are summarized, and some possibilities for further development of the code are discussed. (auth)

  10. A Case Study on Stratified Settlement and Rebound Characteristics due to Dewatering in Shanghai Subway Station

    Directory of Open Access Journals (Sweden)

    Jianxiu Wang

    2013-01-01

    Full Text Available Based on the Yishan Metro Station Project of Shanghai Metro Line number 9, a centrifugal model test was conducted to investigate the behavior of stratified settlement and rebound (SSR of Shanghai soft clay caused by dewatering in deep subway station pit. The soil model was composed of three layers, and the dewatering process was simulated by self-invention of decompressing devise. The results indicate that SSR occurs when the decompression was carried out, and only negative rebound was found in sandy clay, but both positive and negative rebound occurred in the silty clay, and the absolute value of rebound in sandy clay was larger than in silty clay, and the mechanism of SSR was discussed with mechanical sandwich model, and it was found that the load and cohesive force of different soils was the main source of different responses when decompressed.

  11. A case study on stratified settlement and rebound characteristics due to dewatering in Shanghai subway station.

    Science.gov (United States)

    Wang, Jianxiu; Huang, Tianrong; Sui, Dongchang

    2013-01-01

    Based on the Yishan Metro Station Project of Shanghai Metro Line number 9, a centrifugal model test was conducted to investigate the behavior of stratified settlement and rebound (SSR) of Shanghai soft clay caused by dewatering in deep subway station pit. The soil model was composed of three layers, and the dewatering process was simulated by self-invention of decompressing devise. The results indicate that SSR occurs when the decompression was carried out, and only negative rebound was found in sandy clay, but both positive and negative rebound occurred in the silty clay, and the absolute value of rebound in sandy clay was larger than in silty clay, and the mechanism of SSR was discussed with mechanical sandwich model, and it was found that the load and cohesive force of different soils was the main source of different responses when decompressed.

  12. Free convective flow of a stratified fluid through a porous medium bounded by a vertical plane

    Directory of Open Access Journals (Sweden)

    H. K. Mondal

    1994-01-01

    Full Text Available Steady two-dimensional free convection flow of a thermally stratified viscous fluid through a highly porous medium bounded by a vertical plane surface of varying temperature, is considered. Analytical expressions for the velocity, temperature and the rate of heat transfer are obtained by perturbation method. Velocity distribution and rate of heat transfer for different values of parameters are shown in graphs. Velocity distribution is also obtained for certain values of the parameters by integrating the coupled differential equations by Runge-Kutta method and compared with the analytical solution. The chief concern of the paper is to study the effect of equilibrium temperature gradient on the velocity and the rate of heat transfer.

  13. A Fast MHD Code for Gravitationally Stratified Media using Graphical Processing Units: SMAUG

    Science.gov (United States)

    Griffiths, M. K.; Fedun, V.; Erdélyi, R.

    2015-03-01

    Parallelization techniques have been exploited most successfully by the gaming/graphics industry with the adoption of graphical processing units (GPUs), possessing hundreds of processor cores. The opportunity has been recognized by the computational sciences and engineering communities, who have recently harnessed successfully the numerical performance of GPUs. For example, parallel magnetohydrodynamic (MHD) algorithms are important for numerical modelling of highly inhomogeneous solar, astrophysical and geophysical plasmas. Here, we describe the implementation of SMAUG, the Sheffield Magnetohydrodynamics Algorithm Using GPUs. SMAUG is a 1-3D MHD code capable of modelling magnetized and gravitationally stratified plasma. The objective of this paper is to present the numerical methods and techniques used for porting the code to this novel and highly parallel compute architecture. The methods employed are justified by the performance benchmarks and validation results demonstrating that the code successfully simulates the physics for a range of test scenarios including a full 3D realistic model of wave propagation in the solar atmosphere.

  14. Stable evaluation of Green's functions in cylindrically stratified regions with uniaxial anisotropic layers

    Science.gov (United States)

    Moon, H.; Donderici, B.; Teixeira, F. L.

    2016-11-01

    We present a robust algorithm for the computation of electromagnetic fields radiated by point sources (Hertzian dipoles) in cylindrically stratified media where each layer may exhibit material properties (permittivity, permeability, and conductivity) with uniaxial anisotropy. Analytical expressions are obtained based on the spectral representation of the tensor Green's function based on cylindrical Bessel and Hankel eigenfunctions, and extended for layered uniaxial media. Due to the poor scaling of these eigenfunctions for extreme arguments and/or orders, direct numerical evaluation of such expressions can produce numerical instability, i.e., underflow, overflow, and/or round-off errors under finite precision arithmetic. To circumvent these problems, we develop a numerically stable formulation through suitable rescaling of various expressions involved in the computational chain, to yield a robust algorithm for all parameter ranges. Numerical results are presented to illustrate the robustness of the formulation including cases of practical interest.

  15. Mixing in thermally stratified nonlinear spin-up with uniform boundary fluxes

    International Nuclear Information System (INIS)

    Baghdasarian, Meline; Pacheco-Vega, Arturo; Pacheco, J. Rafael; Verzicco, Roberto

    2014-01-01

    Studies of stratified spin-up experiments in enclosed cylinders have reported the presence of small pockets of well-mixed fluids but quantitative measurements of the mixedness of the fluid has been lacking. Previous numerical simulations have not addressed these measurements. Here we present numerical simulations that explain how the combined effect of spin-up and thermal boundary conditions enhances or hinders mixing of a fluid in a cylinder. The energy of the system is characterized by splitting the potential energy into diabatic and adiabatic components, and measurements of efficiency of mixing are based on both, the ratio of dissipation of available potential energy to forcing and variance of temperature. The numerical simulations of the Navier–Stokes equations for the problem with different sets of thermal boundary conditions at the horizontal walls helped shed some light on the physical mechanisms of mixing, for which a clear explanation was absent

  16. Mobilifilum chasei: morphology and ecology of a spirochete from an intertidal stratified microbial mat community

    Science.gov (United States)

    Margulis, L.; Hinkle, G.; Stolz, J.; Craft, F.; Esteve, I.; Guerrero, R.

    1990-01-01

    Spirochetes were found in the lower anoxiphototrophic layer of a stratified microbial mat (North Pond, Laguna Figueroa, Baja California, Mexico). Ultra-structural analysis of thin sections of field samples revealed spirochetes approximately 0.25 micrometer in diameter with 10 or more periplasmic flagella, leading to the interpretation that these spirochetes bear 10 flagellar insertions on each end. Morphometric study showed these free-living spirochetes greatly resemble certain symbiotic ones, i.e., Borrelia and certain termite spirochetes, the transverse sections of which are presented here. The ultrastructure of this spirochete also resembles Hollandina and Diplocalyx (spirochetes symbiotic in arthropods) more than it does Spirochaeta, the well known genus of mud-dwelling spirochetes. The new spirochete was detected in mat material collected both in 1985 and in 1987. Unique morphology (i.e., conspicuous outer coat of inner membrane, large number of periplasmic flagella) and ecology prompt us to name a new free-living spirochete.

  17. Stable evaluation of Green's functions in cylindrically stratified regions with uniaxial anisotropic layers

    Energy Technology Data Exchange (ETDEWEB)

    Moon, H., E-mail: haksu.moon@gmail.com [ElectroScience Laboratory, The Ohio State University, Columbus, OH 43212 (United States); Donderici, B., E-mail: burkay.donderici@halliburton.com [Sensor Physics & Technology, Halliburton Energy Services, Houston, TX 77032 (United States); Teixeira, F.L., E-mail: teixeira@ece.osu.edu [ElectroScience Laboratory, The Ohio State University, Columbus, OH 43212 (United States)

    2016-11-15

    We present a robust algorithm for the computation of electromagnetic fields radiated by point sources (Hertzian dipoles) in cylindrically stratified media where each layer may exhibit material properties (permittivity, permeability, and conductivity) with uniaxial anisotropy. Analytical expressions are obtained based on the spectral representation of the tensor Green's function based on cylindrical Bessel and Hankel eigenfunctions, and extended for layered uniaxial media. Due to the poor scaling of these eigenfunctions for extreme arguments and/or orders, direct numerical evaluation of such expressions can produce numerical instability, i.e., underflow, overflow, and/or round-off errors under finite precision arithmetic. To circumvent these problems, we develop a numerically stable formulation through suitable rescaling of various expressions involved in the computational chain, to yield a robust algorithm for all parameter ranges. Numerical results are presented to illustrate the robustness of the formulation including cases of practical interest.

  18. Piezoelectricity induced defect modes for shear waves in a periodically stratified supperlattice

    Science.gov (United States)

    Piliposyan, Davit

    2018-01-01

    Properties of shear waves in a piezoelectric stratified periodic structure with a defect layer are studied for a superlattice with identical piezoelectric materials in a unit cell. Due to the electro-mechanical coupling in piezoelectric materials the structure exhibits defect modes in the superlattice with full transmission peaks both for full contact and electrically shorted interfaces. The results show an existence of one or two transmission peaks depending on the interfacial conditions. In the long wavelength region where coupling between electro-magnetic and elastic waves creates frequency band gaps the defect layer introduces one or two defect modes transmitting both electro-magnetic and elastic energies. Other parameters affecting the defect modes are the thickness of the defect layer, differences in refractive indexes and the magnitude of the angle of the incident wave. The results of the paper may be useful in the design of narrow band filters or multi-channel piezoelectric filters.

  19. 'Stratified Contraception': Emergency Contraceptive Pills and Women's Differential Experiences in Contemporary India.

    Science.gov (United States)

    Sheoran, Nayantara

    2015-01-01

    Available without prescriptions in India since 2005, emergency contraceptive pills (ECPs) and their advertisements have provided women with increased contraceptive options and a vocabulary to talk about their reproductive lives. I draw on long-term fieldwork with women in urban India about ECPs, demonstrating a new form of 'stratified contraception' enabled by these pills and their advertisements. I posit that there are within India spaces that replicate the luxuries and privileges of the global North. These material conditions, I suggest, are replicated when it comes to contraception as there are hubs of women consumers of contraception and contraceptive advertising that participate in an 'imagined cosmopolitanism' within the global South in close proximity to 'contraceptive ghettos.' Moving beyond simplistic binaries, I outline three major stratifications along which women experience this medical technology and outline the implications for women and their contraceptive choices when notions of northern privilege exist in the 'South.'

  20. Numerical study on interaction of local air cooler with stratified hydrogen cloud in a large vessel

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Z. [Atomic Energy of Canada Limited, Chalk River Laboratories, ON K0J 1J0 (Canada); Andreani, M. [Laboratory for Thermal-Hydraulics, Paul Scherrer Institut, 5232 Villigen (Switzerland)

    2012-07-01

    Within the framework of the ERCOSAM project, planning calculations are performed to examine sensitivity parameters that can affect the break-up (erosion) of a helium layer by mitigation devices (i.e., cooler, spray, or Passive Autocatalytic Recombiner - PAR). This paper reports the GOTHIC analysis results for the cooler tests to be performed in the PANDA facility. The cooler elevation and geometry, helium layer thickness, steam distribution in the vessel, and the vessel geometry (inter-connected multi-compartments versus a single volume) on the erosion process as well as the cooling capacity are studied. This analysis is valuable because only a limited number of conditions will be examined in the planned experiments. The study provides a useful understanding of the interaction of a cooler with a stratified atmosphere. (authors)

  1. Mixing in thermally stratified nonlinear spin-up with uniform boundary fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Baghdasarian, Meline; Pacheco-Vega, Arturo [Department of Mechanical Engineering, California State University, Los Angeles, Los Angeles, California 90032 (United States); Pacheco, J. Rafael, E-mail: rpacheco@asu.edu [SAP Americas Inc., Scottsdale, Arizona 85251 (United States); School of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona 85287 (United States); Environmental Fluid Dynamics Laboratories, Department of Civil Engineering and Geological Sciences, The University of Notre Dame, South Bend, Indiana 46556 (United States); Verzicco, Roberto [Dipartimento di Ingegneria Meccanica, Universita di Roma “Tor Vergata”, Via del Politecnico 1, 00133, Roma (Italy); PoF, University of Twente, 7500 AE Enschede (Netherlands)

    2014-09-15

    Studies of stratified spin-up experiments in enclosed cylinders have reported the presence of small pockets of well-mixed fluids but quantitative measurements of the mixedness of the fluid has been lacking. Previous numerical simulations have not addressed these measurements. Here we present numerical simulations that explain how the combined effect of spin-up and thermal boundary conditions enhances or hinders mixing of a fluid in a cylinder. The energy of the system is characterized by splitting the potential energy into diabatic and adiabatic components, and measurements of efficiency of mixing are based on both, the ratio of dissipation of available potential energy to forcing and variance of temperature. The numerical simulations of the Navier–Stokes equations for the problem with different sets of thermal boundary conditions at the horizontal walls helped shed some light on the physical mechanisms of mixing, for which a clear explanation was absent.

  2. First detection of mycobacteria in African rodents and insectivores, using stratified pool screening

    DEFF Research Database (Denmark)

    Durnez, L.; Eddyani, M.; Mgode, G. F.

    2007-01-01

    With the rising number of patients with human immunodeficiency virus (HIV)/AIDS in developing countries, the control of mycobacteria is of growing importance. Previous studies have shown that rodents and insectivores are carriers of mycobacteria. However, it is not clear how widespread mycobacteria...... spp.) were isolated from C. gambianus, Mastomys natalensis, and C. hirta. This study is the first to report findings of mycobacteria in African rodents and insectivores and the first in mycobacterial ecology to estimate the prevalence of mycobacteria after stratified pool screening. The fact...... that small mammals in urban areas carry more mycobacteria than those in the fields and that potentially pathogenic mycobacteria were isolated identifies a risk for other animals and humans, especially HIV/AIDS patients, that have a weakened immune system. ...

  3. Stratified steady and unsteady two-phase flows between two parallel plates

    International Nuclear Information System (INIS)

    Sim, Woo Gun

    2006-01-01

    To understand fluid dynamic forces acting on a structure subjected to two-phase flow, it is essential to get detailed information about the characteristics of two-phase flow. Stratified steady and unsteady two-phase flows between two parallel plates have been studied to investigate the general characteristics of the flow related to flow-induced vibration. Based on the spectral collocation method, a numerical approach has been developed for the unsteady two-phase flow. The method is validated by comparing numerical result to analytical one given for a simple harmonic two-phase flow. The flow parameters for the steady two-phase flow, such as void fraction and two-phase frictional multiplier, are evaluated. The dynamic characteristics of the unsteady two-phase flow, including the void fraction effect on the complex unsteady pressure, are illustrated

  4. Propagation of electromagnetic waves in stratified media with nonlinearity in both dielectric and magnetic responses.

    Science.gov (United States)

    Kim, Kihong; Phung, D K; Rotermund, F; Lim, H

    2008-01-21

    We develop a generalized version of the invariant imbedding method, which allows us to solve the electromagnetic wave equations in arbitrarily inhomogeneous stratified media where both the dielectric permittivity and magnetic permeability depend on the strengths of the electric and magnetic fields, in a numerically accurate and efficient manner. We apply our method to a uniform nonlinear slab and find that in the presence of strong external radiation, an initially uniform medium of positive refractive index can spontaneously change into a highly inhomogeneous medium where regions of positive or negative refractive index as well as metallic regions appear. We also study the wave transmission properties of periodic nonlinear media and the influence of nonlinearity on the mode conversion phenomena in inhomogeneous plasmas. We argue that our theory is very useful in the study of the optical properties of a variety of nonlinear media including nonlinear negative index media fabricated using wires and split-ring resonators.

  5. Redox stratified biofilms to support completely autotrophic nitrogen removal: Principles and results

    DEFF Research Database (Denmark)

    Pellicer i Nàcher, Carles; Smets, Barth F.

    liquid. If operated properly, MABRs yield compact and homogeneous redox-stratified biofilms capable of hosting side-by-side aerobic and anaerobic microbial communities. We have recently demonstrated that completely autotrophic nitrogen removal is feasible in MABRs at nitrogen removal rates as high as 5......After 10 years of pilot and full-scale studies, completely autotrophic nitrogen via coupled aerobic and anaerobic ammonium oxidation is now firmly established in the wastewater treatment community. The reasons for the popularization of the technology are numerous, but the most attractive....... The continuous and sustained inoculation of metabolically active anaerobic oxidizing bacteria from a biofilm reactor placed in the recirculation line of our MABRs showed to shorten considerably the onset of autotrophic nitrogen removal. However, the main hurdle keeping MABRs from attaining high removal...

  6. Upscaling of Two-Phase Immiscible Flows in Communicating Stratified Reservoirs

    DEFF Research Database (Denmark)

    Zhang, Xuan; Shapiro, Alexander; Stenby, Erling Halfdan

    2011-01-01

    A semi-analytical method for upscaling two-phase immiscible flows in heterogeneous porous media is described. This method is developed for stratified reservoirs with perfect communication between layers (the case of vertical equilibrium), in a viscous dominant regime, where the effects of capillary...... forces and gravity may be neglected. The method is discussed on the example of its basic application: waterflooding in petroleum reservoirs. We apply asymptotic analysis to a system of two-dimensional (2D) mass conservation equations for incompressible fluids. For high anisotropy ratios, the pressure...... and piston-like displacement, and it presumes non-zero exchange between layers. The method generalizes also the study of Yortsos (Transp Porous Media 18:107–129, 1995), taking into account in a more consistent way the interactions between the layers....

  7. Alfven wave resonances and flow induced by nonlinear Alfven waves in a stratified atmosphere

    International Nuclear Information System (INIS)

    Stark, B. A.; Musielak, Z. E.; Suess, S. T.

    1996-01-01

    A nonlinear, time-dependent, ideal MHD code has been developed and used to compute the flow induced by nonlinear Alfven waves propagating in an isothermal, stratified, plane-parallel atmosphere. The code is based on characteristic equations solved in a Lagrangian frame. Results show that resonance behavior of Alfven waves exists in the presence of a continuous density gradient and that the waves with periods corresponding to resonant peaks exert considerably more force on the medium than off-resonance periods. If only off-peak periods are considered, the relationship between the wave period and induced longitudinal velocity shows that short period WKB waves push more on the background medium than longer period, non-WKB, waves. The results also show the development of the longitudinal waves induced by finite amplitude Alfven waves. Wave energy transferred to the longitudinal mode may provide a source of localized heating

  8. Fuel-air mixing and distribution in a direct-injection stratified-charge rotary engine

    Science.gov (United States)

    Abraham, J.; Bracco, F. V.

    1989-01-01

    A three-dimensional model for flows and combustion in reciprocating and rotary engines is applied to a direct-injection stratified-charge rotary engine to identify the main parameters that control its burning rate. It is concluded that the orientation of the six sprays of the main injector with respect to the air stream is important to enhance vaporization and the production of flammable mixture. In particular, no spray should be in the wake of any other spray. It was predicted that if such a condition is respected, the indicated efficiency would increase by some 6 percent at higher loads and 2 percent at lower loads. The computations led to the design of a new injector tip that has since yielded slightly better efficiency gains than predicted.

  9. Performance of a supercharged direct-injection stratified-charge rotary combustion engine

    Science.gov (United States)

    Bartrand, Timothy A.; Willis, Edward A.

    1990-01-01

    A zero-dimensional thermodynamic performance computer model for direct-injection stratified-charge rotary combustion engines was modified and run for a single rotor supercharged engine. Operating conditions for the computer runs were a single boost pressure and a matrix of speeds, loads and engine materials. A representative engine map is presented showing the predicted range of efficient operation. After discussion of the engine map, a number of engine features are analyzed individually. These features are: heat transfer and the influence insulating materials have on engine performance and exhaust energy; intake manifold pressure oscillations and interactions with the combustion chamber; and performance losses and seal friction. Finally, code running times and convergence data are presented.

  10. A study of a direct-injection stratified-charge rotary engine for motor vehicle application

    Science.gov (United States)

    Kagawa, Ryoji; Okazaki, Syunki; Somyo, Nobuhiro; Akagi, Yuji

    1993-03-01

    A study of a direct-injection stratified-charge system (DISC), as applied to a rotary engine (RE) for motor vehicle usage, was undertaken. The goals of this study were improved fuel consumption and reduced exhaust emissions. These goals were thought feasible due to the high thermal efficiency associated with the DISC-RE. This was the first application of this technology to a motor vehicle engine. Stable ignition and ideal stratification systems were developed by means of numerical calculations, air-fuel mixture measurements, and actual engine tests. The use of DISC resulted in significantly improved fuel consumption and reduced exhaust emissions. The use of an exhaust gas recirculating system was studied and found to be beneficial in NOx reduction.

  11. Stratified systems without organic solvent - new extraction type of macro- and microquantities of metal ions

    International Nuclear Information System (INIS)

    Dyogtev, M.I.; Alikina, E.N.; Popova, O.N.; Amindjanov, A.A.

    2012-01-01

    This article describes the results of studies on solubility in four component systems: di anti pyril methane-benzoic (salicylic) acid-HCl-H 2 O, hexyl di anti pyril methane-benzoic (salicylic) acid-HCl-H 2 O at 298 and 323 K. It is defined that stable stratification appears by addition of hydrochloric acid in the concentration range of 3.0-4.9 wt.% HCl. At substitution of di anti pyril methane on hexyl di anti pyril methane the wide range of stratification in the cut of hexyl di anti pyril methane-benzoic (salicylic) acid - 5 wt.% HCl is observes. The possibility of using of stratified systems for quantitative extraction of copper, cadmium, iron, thallium and tin is proposed.

  12. Condensation heat transfer coefficient in horizontal stratified cocurrent flow of steam and cold water

    International Nuclear Information System (INIS)

    Kim, Kap; Kim, Hho Jung

    1986-01-01

    Some studies on direct-contact condensation in cocurrent stratified flow of steam and subcooled water were reviewed. Several approaches have been performed to develop the condensation heat transfer coefficient relationship. The local Nusselt number is correlated in terms of the local water Reynolds and Prandtl numbers as well as the steam Froude number. In addition, a turbulence-centered model, developed principally for gas absorption in several geometries, is modified by using calculated interfacial parameters for the turbulent velocity and length scales. These approaches result in a fairly good agreement with the data, whereas, the turbulence-centered model is here recommended since it is based on the turbulent properties which may be closely related to the condensation phenomena. (Author)

  13. Tests of the TRAC code against known analytical solutions for stratified flow

    International Nuclear Information System (INIS)

    Black, P.S.; Leslie, D.C.; Hewitt, G.F.

    1987-01-01

    The area averaged equations for gas-liquid flow are briefly summarized and related, for the specific case of stratified flow, to the shallow water equations commonly used in hydraulics. These equations are then compared to the equations used in TRAC-PF/MOD1 and are shown to differ in their treatment of the gravity head terms. A modification of the TRAC code is therefore necessary to bring it into line with established shallow water theory. The corrected form of the code was compared with a number of specific cases, each of which throws further light on the code behavior. The following areas are discussed in the paper: (1) the dam break problem; (2) Kelvin-Helmholtz instability; (3) counter-current flow; and (4) slug flow. It is concluded that detailed comparisons of the code with known analytic solutions and with a number of the more complex phenomenological experiments can give useful insights into its behavior

  14. Analytical Simulation of Flow and Heat Transfer of Two-Phase Nanofluid (Stratified Flow Regime

    Directory of Open Access Journals (Sweden)

    Mohammad Abbasi

    2014-01-01

    Full Text Available Nanofluids have evoked immense interest from researchers all around the globe due to their numerous potential benefits and applications in important fields such as cooling electronic parts, cooling car engines and nuclear reactors. An analytical study of fluid flow of in-tube stratified regime of two-phase nanofluid has been carried out for CuO, Al2O2, TiO3, and Au as applied nanoparticles in water as the base liquid. Liquid film thickness, convective heat transfer coefficient, and dryout length have been calculated. Among the considered nano particles, Al2O3 and TiO2 because of providing more amounts of heat transfer along with longer lengths of dryout found as the most appropriate nanoparticles to achieve cooling objectives.

  15. Management of kidney cancer in Asia: resource-stratified guidelines from the Asian Oncology Summit 2012.

    Science.gov (United States)

    Chiong, Edmund; Tay, Miah Hiang; Tan, Min Han; Kumar, Santosh; Sim, Hong Gee; Teh, Bin Tean; Umbas, Rainy; Chau, Noan Minh

    2012-11-01

    Treatment of renal-cell carcinoma has progressed over the past decade, in terms of surgical and systemic therapy. Current treatment guidelines are based on clinical evidence, but do not take into account resource limitations among different countries. These limitations, which include financial and logistical challenges and lack of skilled health-care professionals, have the greatest effect in low-income countries. This consolidated statement gives treatment recommendations for renal-cell carcinoma that are based on clinical evidence and stratified according to extent of resource availability. The statement was formulated by a panel of urologists, medical oncologists, and clinical oncologists from Asian countries, at a consensus session on kidney cancer that was held as part of the 2012 Asian Oncology Summit in Singapore. Resource levels are defined according to a four-tier system (basic, limited, enhanced, and maximum), and treatment recommendations are specified based on availability of financial, skill, and logistical resources. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Stratifying Tropical Fires by Land Cover: Insights into Amazonian Fires, Aerosol Loading, and Regional Deforestation

    Science.gov (United States)

    TenHoeve, J. E.; Remer, L. A.; Jacobson, M. Z.

    2010-01-01

    This study analyzes changes in the number of fires detected on forest, grass, and transition lands during the 2002-2009 biomass burning seasons using fire detection data and co-located land cover classifications from the Moderate Resolution Imaging Spectroradiometer (MODIS). We find that the total number of detected fires correlates well with MODIS mean aerosol optical depth (AOD) from year to year, in accord with other studies. However, we also show that the ratio of forest to savanna fires varies substantially from year to year. Forest fires have trended downward, on average, since the beginning of 2006 despite a modest increase in 2007. Our study suggests that high particulate matter loading detected in 2007 was likely due to a large number of savanna/agricultural fires that year. Finally, we illustrate that the correlation between annual Brazilian deforestation estimates and MODIS fires is considerably higher when fires are stratified by MODIS-derived land cover classifications.

  17. An algorithm for solving the optical problem for stratified anisotropic media

    Energy Technology Data Exchange (ETDEWEB)

    Palto, S P [Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 117333 (Russian Federation)

    2001-04-01

    An algorithm for solving the Maxwell equations for propagation of light through anisotropic stratified media is considered. The algorithm uses the Berreman matrices of order 4 x 4. In contrast to the numerical methods suggested by Berreman, the new method is exact. The Sylvester theorem for calculating functions of a matrix and the Laguerre method for determining eigenvalues provide the basis for an algorithm with an efficiency comparable to that of the algorithms based on analytic solutions, which exist only in the case of uniaxial media. The method suggested in this paper allows for the analysis of complex optical systems where the effects of biaxiality, magnetic anisotropy, and optical activity play an important role.

  18. Expression of GLUT1 in stratified squamous epithelia and oral carcinoma from humans and rats

    DEFF Research Database (Denmark)

    Voldstedlund, M; Dabelsteen, Erik

    1997-01-01

    mucosa from rat and man, and a human oral carcinoma by indirect immunofluorescence microscopy. The results showed that GLUT1 was expressed in the basal and parabasal layers of the different stratified squamous epithelia, with some variations between keratinized and non-keratinized subtypes. GLUT1...... was also expressed in ductal- and myoepithelial cells of minor salivary glands and perineural sheath located in the lamina propra, and furthermore in the cells of an oral carcinoma. GLUT4 was not expressed in any of the tissues examined. This distribution of GLUT1 does not fit with the idea of GLUT1......Most cells express facilitative glucose transporters. Four isoforms (GLUT1-4) transporting D-glucose across the plasma membrane show a specific tissue distribution, which is the basis for tissue-specific patterns in glucose metabolism. GLUT1 is expressed at high levels in tissue barriers...

  19. Model-Based Prediction of Pulsed Eddy Current Testing Signals from Stratified Conductive Structures

    International Nuclear Information System (INIS)

    Zhang, Jian Hai; Song, Sung Jin; Kim, Woong Ji; Kim, Hak Joon; Chung, Jong Duk

    2011-01-01

    Excitation and propagation of electromagnetic field of a cylindrical coil above an arbitrary number of conductive plates for pulsed eddy current testing(PECT) are very complex problems due to their complicated physical properties. In this paper, analytical modeling of PECT is established by Fourier series based on truncated region eigenfunction expansion(TREE) method for a single air-cored coil above stratified conductive structures(SCS) to investigate their integrity. From the presented expression of PECT, the coil impedance due to SCS is calculated based on analytical approach using the generalized reflection coefficient in series form. Then the multilayered structures manufactured by non-ferromagnetic (STS301L) and ferromagnetic materials (SS400) are investigated by the developed PECT model. Good prediction of analytical model of PECT not only contributes to the development of an efficient solver but also can be applied to optimize the conditions of experimental setup in PECT

  20. An experimental investigation of stratified two-phase pipe flow at small inclinations

    Energy Technology Data Exchange (ETDEWEB)

    Espedal, Mikal

    1998-12-31

    The prediction of stratified flow is important for several industrial applications. Stratified flow experiments were carefully performed in order to investigate the performance of a typical model which uses wall friction factors based on single phase pipe flow as described above. The test facility has a 18.5 m long and 60 mm i.d. (L/D=300) acrylic test section which can be inclined between -10 {sup o} and +10 {sup o}. The liquid holdup was measured by using fast closing valves and the pressure gradients by using three differential pressure transducers. Interfacial waves were measured by thin wire conductance probes mounted in a plane perpendicular to the main flow. The experiments were performed using water and air at atmospheric pressure. The selected test section inclinations were between -3 {sup o} and +0.5 {sup o} to the horizontal plane. A large number of experiments were performed for different combinations of air and water flow rates and the rates were limited to avoid slug flow and stratified flow with liquid droplets. The pressure gradient and the liquid holdup were measured. In addition the wave probes were used to find the wave heights and the wave power spectra. The results show that the predicted pressure gradient using the standard models is approximately 30% lower than the measured value when large amplitude waves are present. When the flow is driven by the interfacial force the test section inclination has minor influence on the deviation between predicted and measured pressure gradients. Similar trends are apparent in data from the literature, although they seem to have gone unnoticed. For several data sets large spread in the predictions are observed when the model described above was used. Gas wall shear stress experiments indicate that the main cause of the deviation between measured and predicted pressure gradient and holdup resides in the modelling of the liquid wall friction term. Measurements of the liquid wall shear stress distribution

  1. A 3D spectral anelastic hydrodynamic code for shearing, stratified flows

    Science.gov (United States)

    Barranco, Joseph A.; Marcus, Philip S.

    2006-11-01

    We have developed a three-dimensional (3D) spectral hydrodynamic code to study vortex dynamics in rotating, shearing, stratified systems (e.g., the atmosphere of gas giant planets, protoplanetary disks around newly forming protostars). The time-independent background state is stably stratified in the vertical direction and has a unidirectional linear shear flow aligned with one horizontal axis. Superposed on this background state is an unsteady, subsonic flow that is evolved with the Euler equations subject to the anelastic approximation to filter acoustic phenomena. A Fourier Fourier basis in a set of quasi-Lagrangian coordinates that advect with the background shear is used for spectral expansions in the two horizontal directions. For the vertical direction, two different sets of basis functions have been implemented: (1) Chebyshev polynomials on a truncated, finite domain, and (2) rational Chebyshev functions on an infinite domain. Use of this latter set is equivalent to transforming the infinite domain to a finite one with a cotangent mapping, and using cosine and sine expansions in the mapped coordinate. The nonlinear advection terms are time-integrated explicitly, the pressure/enthalpy terms are integrated semi-implicitly, and the Coriolis force and buoyancy terms are treated semi-analytically. We show that internal gravity waves can be damped by adding new terms to the Euler equations. The code exhibits excellent parallel performance with the message passing interface (MPI). As a demonstration of the code, we simulate the merger of two 3D vortices in the midplane of a protoplanetary disk.

  2. Model test on partial expansion in stratified subsidence during foundation pit dewatering

    Science.gov (United States)

    Wang, Jianxiu; Deng, Yansheng; Ma, Ruiqiang; Liu, Xiaotian; Guo, Qingfeng; Liu, Shaoli; Shao, Yule; Wu, Linbo; Zhou, Jie; Yang, Tianliang; Wang, Hanmei; Huang, Xinlei

    2018-02-01

    Partial expansion was observed in stratified subsidence during foundation pit dewatering. However, the phenomenon was suspected to be an error because the compression of layers is known to occur when subsidence occurs. A slice of the subsidence cone induced by drawdown was selected as the prototype. Model tests were performed to investigate the phenomenon. The underlying confined aquifer was generated as a movable rigid plate with a hinge at one end. The overlying layers were simulated with remolded materials collected from a construction site. Model tests performed under the conceptual model indicated that partial expansion occurred in stratified settlements under coordination deformation and consolidation conditions. During foundation pit dewatering, rapid drawdown resulted in rapid subsidence in the dewatered confined aquifer. The rapidly subsiding confined aquifer top was the bottom deformation boundary of the overlying layers. Non-coordination deformation was observed at the top and bottom of the subsiding overlying layers. The subsidence of overlying layers was larger at the bottom than at the top. The layers expanded and became thicker. The phenomenon was verified using numerical simulation method based on finite difference method. Compared with numerical simulation results, the boundary effect of the physical tests was obvious in the observation point close to the movable endpoint. The tensile stress of the overlying soil layers induced by the underlying settlement of dewatered confined aquifer contributed to the expansion phenomenon. The partial expansion of overlying soil layers was defined as inversed rebound. The inversed rebound was induced by inversed coordination deformation. Compression was induced by the consolidation in the overlying soil layers because of drainage. Partial expansion occurred when the expansion exceeded the compression. Considering the inversed rebound, traditional layer-wise summation method for calculating subsidence should be

  3. Invited Review. Combustion instability in spray-guided stratified-charge engines. A review

    Energy Technology Data Exchange (ETDEWEB)

    Fansler, Todd D. [Univ. of Wisconsin, Madison, WI (United States); Reuss, D. L. [Univ. of Michigan, Ann Arbor, MI (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sick, V. [Univ. of Michigan, Ann Arbor, MI (United States); Dahms, R. N. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2015-02-02

    Our article reviews systematic research on combustion instabilities (principally rare, random misfires and partial burns) in spray-guided stratified-charge (SGSC) engines operated at part load with highly stratified fuel -air -residual mixtures. Results from high-speed optical imaging diagnostics and numerical simulation provide a conceptual framework and quantify the sensitivity of ignition and flame propagation to strong, cyclically varying temporal and spatial gradients in the flow field and in the fuel -air -residual distribution. For SGSC engines using multi-hole injectors, spark stretching and locally rich ignition are beneficial. Moreover, combustion instability is dominated by convective flow fluctuations that impede motion of the spark or flame kernel toward the bulk of the fuel, coupled with low flame speeds due to locally lean mixtures surrounding the kernel. In SGSC engines using outwardly opening piezo-electric injectors, ignition and early flame growth are strongly influenced by the spray's characteristic recirculation vortex. For both injection systems, the spray and the intake/compression-generated flow field influence each other. Factors underlying the benefits of multi-pulse injection are identified. Finally, some unresolved questions include (1) the extent to which piezo-SGSC misfires are caused by failure to form a flame kernel rather than by flame-kernel extinction (as in multi-hole SGSC engines); (2) the relative contributions of partially premixed flame propagation and mixing-controlled combustion under the exceptionally late-injection conditions that permit SGSC operation on E85-like fuels with very low NOx and soot emissions; and (3) the effects of flow-field variability on later combustion, where fuel-air-residual mixing within the piston bowl becomes important.

  4. Phenomenology of two-dimensional stably stratified turbulence under large-scale forcing

    KAUST Repository

    Kumar, Abhishek; Verma, Mahendra K.; Sukhatme, Jai

    2017-01-01

    In this paper, we characterise the scaling of energy spectra, and the interscale transfer of energy and enstrophy, for strongly, moderately and weakly stably stratified two-dimensional (2D) turbulence, restricted in a vertical plane, under large-scale random forcing. In the strongly stratified case, a large-scale vertically sheared horizontal flow (VSHF) coexists with small scale turbulence. The VSHF consists of internal gravity waves and the turbulent flow has a kinetic energy (KE) spectrum that follows an approximate k−3 scaling with zero KE flux and a robust positive enstrophy flux. The spectrum of the turbulent potential energy (PE) also approximately follows a k−3 power-law and its flux is directed to small scales. For moderate stratification, there is no VSHF and the KE of the turbulent flow exhibits Bolgiano–Obukhov scaling that transitions from a shallow k−11/5 form at large scales, to a steeper approximate k−3 scaling at small scales. The entire range of scales shows a strong forward enstrophy flux, and interestingly, large (small) scales show an inverse (forward) KE flux. The PE flux in this regime is directed to small scales, and the PE spectrum is characterised by an approximate k−1.64 scaling. Finally, for weak stratification, KE is transferred upscale and its spectrum closely follows a k−2.5 scaling, while PE exhibits a forward transfer and its spectrum shows an approximate k−1.6 power-law. For all stratification strengths, the total energy always flows from large to small scales and almost all the spectral indicies are well explained by accounting for the scale-dependent nature of the corresponding flux.

  5. Phenomenology of two-dimensional stably stratified turbulence under large-scale forcing

    KAUST Repository

    Kumar, Abhishek

    2017-01-11

    In this paper, we characterise the scaling of energy spectra, and the interscale transfer of energy and enstrophy, for strongly, moderately and weakly stably stratified two-dimensional (2D) turbulence, restricted in a vertical plane, under large-scale random forcing. In the strongly stratified case, a large-scale vertically sheared horizontal flow (VSHF) coexists with small scale turbulence. The VSHF consists of internal gravity waves and the turbulent flow has a kinetic energy (KE) spectrum that follows an approximate k−3 scaling with zero KE flux and a robust positive enstrophy flux. The spectrum of the turbulent potential energy (PE) also approximately follows a k−3 power-law and its flux is directed to small scales. For moderate stratification, there is no VSHF and the KE of the turbulent flow exhibits Bolgiano–Obukhov scaling that transitions from a shallow k−11/5 form at large scales, to a steeper approximate k−3 scaling at small scales. The entire range of scales shows a strong forward enstrophy flux, and interestingly, large (small) scales show an inverse (forward) KE flux. The PE flux in this regime is directed to small scales, and the PE spectrum is characterised by an approximate k−1.64 scaling. Finally, for weak stratification, KE is transferred upscale and its spectrum closely follows a k−2.5 scaling, while PE exhibits a forward transfer and its spectrum shows an approximate k−1.6 power-law. For all stratification strengths, the total energy always flows from large to small scales and almost all the spectral indicies are well explained by accounting for the scale-dependent nature of the corresponding flux.

  6. Experimental investigation and physical description of stratified flow in horizontal channels

    International Nuclear Information System (INIS)

    Staebler, T.

    2007-05-01

    The interaction between a liquid film and turbulent gas flows plays an important role in many technical applications (e.g. in hydraulic engineering, process engineering and nuclear engineering). The local kinematic and turbulent time-averaged flow quantities for counter-current stratified flows (supercritical and subcritical flows with and without flow reversal) have been measured for the first time. Therefore, the method of Particle Image Velocimetry was applied. By using fluorescent particles in combination with an optical filter it was possible to determine the flow quantities of the liquid phase up to the free surface. Additionally, the gaseous phase was investigated by using the scattering of light of conventional particles. With a further measurement technique the void fraction distribution along the channel height has been determined. For this purpose, a single-tip conductivity probe was developed. Furthermore, water delivery rates and pressure losses along the test section were measured over a wide range of parameters. The measurements also revealed new details on the hysteresis effect after the occurrence of flow reversal. The experimental findings were used to develop and validate a statistical model in which the liquid phase is considered to be an agglomeration of interacting particles. The statistical consideration of the particle interactions delivers a differential equation which can be used to predict the local void fraction distribution with the local turbulent kinematic energies of the liquid phase. Beyond that, an additional statistical description is presented in which the probability density functions of the local void fraction are described by beta-functions. Both theoretical approaches can be used for numerical modelling whereas the statistical model can be used to describe the phase interactions and the statistical description to describe the turbulent fluctuations of the local void fraction. Thus, this work has made available all necessary

  7. Data splitting for artificial neural networks using SOM-based stratified sampling.

    Science.gov (United States)

    May, R J; Maier, H R; Dandy, G C

    2010-03-01

    Data splitting is an important consideration during artificial neural network (ANN) development where hold-out cross-validation is commonly employed to ensure generalization. Even for a moderate sample size, the sampling methodology used for data splitting can have a significant effect on the quality of the subsets used for training, testing and validating an ANN. Poor data splitting can result in inaccurate and highly variable model performance; however, the choice of sampling methodology is rarely given due consideration by ANN modellers. Increased confidence in the sampling is of paramount importance, since the hold-out sampling is generally performed only once during ANN development. This paper considers the variability in the quality of subsets that are obtained using different data splitting approaches. A novel approach to stratified sampling, based on Neyman sampling of the self-organizing map (SOM), is developed, with several guidelines identified for setting the SOM size and sample allocation in order to minimize the bias and variance in the datasets. Using an example ANN function approximation task, the SOM-based approach is evaluated in comparison to random sampling, DUPLEX, systematic stratified sampling, and trial-and-error sampling to minimize the statistical differences between data sets. Of these approaches, DUPLEX is found to provide benchmark performance with good model performance, with no variability. The results show that the SOM-based approach also reliably generates high-quality samples and can therefore be used with greater confidence than other approaches, especially in the case of non-uniform datasets, with the benefit of scalability to perform data splitting on large datasets. Copyright 2009 Elsevier Ltd. All rights reserved.

  8. Experimental study of stratified jet by simultaneous measurements of velocity and density fields

    Science.gov (United States)

    Xu, Duo; Chen, Jun

    2012-07-01

    Stratified flows with small density difference commonly exist in geophysical and engineering applications, which often involve interaction of turbulence and buoyancy effect. A combined particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) system is developed to measure the velocity and density fields in a dense jet discharged horizontally into a tank filled with light fluid. The illumination of PIV particles and excitation of PLIF dye are achieved by a dual-head pulsed Nd:YAG laser and two CCD cameras with a set of optical filters. The procedure for matching refractive indexes of two fluids and calibration of the combined system are presented, as well as a quantitative analysis of the measurement uncertainties. The flow structures and mixing dynamics within the central vertical plane are studied by examining the averaged parameters, turbulent kinetic energy budget, and modeling of momentum flux and buoyancy flux. At downstream, profiles of velocity and density display strong asymmetry with respect to its center. This is attributed to the fact that stable stratification reduces mixing and unstable stratification enhances mixing. In stable stratification region, most of turbulence production is consumed by mean-flow convection, whereas in unstable stratification region, turbulence production is nearly balanced by viscous dissipation. Experimental data also indicate that at downstream locations, mixing length model performs better in mixing zone of stable stratification regions, whereas in other regions, eddy viscosity/diffusivity models with static model coefficients represent effectively momentum and buoyancy flux terms. The measured turbulent Prandtl number displays strong spatial variation in the stratified jet.

  9. Modified STOP-Bang Tool for Stratifying Obstructive Sleep Apnea Risk in Adolescent Children.

    Directory of Open Access Journals (Sweden)

    Daniel Combs

    Full Text Available Obstructive sleep apnea (OSA is prevalent in children and diagnostic polysomnography is costly and not readily available in all areas. We developed a pediatric modification of a commonly used adult clinical prediction tool for stratifying the risk of OSA and the need for polysomnography.A total of 312 children (age 9-17 years from phase 2 of the Tucson Children's Assessment of Sleep Apnea cohort study, with complete anthropomorphic data, parent questionnaires, and home polysomnograms were included. An adolescent modification of STOP-Bang (teen STOP-Bang was developed and included snoring, tired, observed apnea, blood pressure ≥ 95th percentile, BMI > 95th percentile, academic problems, neck circumference >95th percentile for age, and male gender. An apnea-hypopnea index ≥ 1.5 events/hour was considered diagnostic of OSA.Receiver Operator Characteristic (ROC curves for parent-reported STOP-Bang scores were generated for teenage and pre-teen children. A STOP-Bang score of < 3 in teenagers was associated with a negative predictive value of 0.96. ROC curves were also generated based upon child-reported sexual maturity rating (SMR; n = 291. The ability of teen STOP-Bang to discriminate the presence or absence of OSA as measured by the AUC for children with SMR ≥ 4 (0.83; 95%CI 0.71-0.95 was better than children with SMR < 4 (0.63; 95%CI 0.46-0.81; p = 0.048.In community dwelling adolescents, teen STOP-Bang may be useful in stratifying the risk of OSA.

  10. Implications of the modelling of stratified hot water storage tanks in the simulation of CHP plants

    Energy Technology Data Exchange (ETDEWEB)

    Campos Celador, A., E-mail: alvaro.campos@ehu.es [ENEDI Research Group-University of the Basque Country, Departamento de Maquinas y Motores Termicos, E.T.S.I. de Bilbao Alameda de Urquijo, s/n 48013 Bilbao, Bizkaia (Spain); Odriozola, M.; Sala, J.M. [ENEDI Research Group-University of the Basque Country, Departamento de Maquinas y Motores Termicos, E.T.S.I. de Bilbao Alameda de Urquijo, s/n 48013 Bilbao, Bizkaia (Spain)

    2011-08-15

    Highlights: {yields} Three different modelling approaches for simulation of hot water tanks are presented. {yields} The three models are simulated within a residential cogeneration plant. {yields} Small differences in the results are found by an energy and exergy analysis. {yields} Big differences between the results are found by an advanced exergy analysis. {yields} Results on the feasibility study are explained by the advanced exergy analysis. - Abstract: This paper considers the effect that different hot water storage tank modelling approaches have on the global simulation of residential CHP plants as well as their impact on their economic feasibility. While a simplified assessment of the heat storage is usually considered in the feasibility studies of CHP plants in buildings, this paper deals with three different levels of modelling of the hot water tank: actual stratified model, ideal stratified model and fully mixed model. These three approaches are presented and comparatively evaluated under the same case of study, a cogeneration plant with thermal storage meeting the loads of an urbanisation located in the Bilbao metropolitan area (Spain). The case of study is simulated by TRNSYS for each one of the three modelling cases and the so obtained annual results are analysed from both a First and Second-Law-based viewpoint. While the global energy and exergy efficiencies of the plant for the three modelling cases agree quite well, important differences are found between the economic results of the feasibility study. These results can be predicted by means of an advanced exergy analysis of the storage tank considering the endogenous and exogenous exergy destruction terms caused by the hot water storage tank.

  11. Simultaneous reduction of NOx and smoke using stratified charge compression ignition; Sojo kongoki no asshuku chakka ni yoru NOx smoke no doji teige

    Energy Technology Data Exchange (ETDEWEB)

    Hashizume, T.; Miyamoto, T.; Akagawa, H. [New ACE Institute Co. Ltd., Ibaraki (Japan); Tsujimura, K. [Chiba Institute of Technology, Chiba (Japan)

    2000-12-25

    Simultaneous reduction of NO{sub x} and smoke under high load conditions could be obtained by MULDIC (MULtiple stage DIesel Combustion) where mixture was made stratified before ignition. In this investigation of the basic characteristics of MULDIC, gaseous fuels (DME, Propane) were charged into the intake air which led to the creation of homogeneous lean mixture, and liquid fuel was injected into the cylinder and made rich mixture. The results of the engine test showed that NO{sub x} emissions could be reduced to less than 100 ppm and smoke emissions were also maintained 0 FSN even at higher loads. Moreover, homogeneous rich mixture test results showed that low smoke combustion could be obtained under equivalence ratio of 1.6. In MULDIC, increasing the ignition delay period of injected fuel, soot formation rate was decreased, because over rich region was avoided. (author)

  12. Furfural stability in various conditions

    OpenAIRE

    Oreiro Muzas, Olaya

    2011-01-01

    The topic of this thesis is the study of the furfural stability to determine the influence of some conditions in furfural degradation. The aim of the study is to decrease furfural degradation and thus improve furfural yield in furfural production. The thesis consists of a literature review and laboratory experiments. Attention has been paid to the furfural description and properties as well as the background of the research and traditional methods to produce furfural. In the experiments, w...

  13. Proposed catalog of the neuroanatomy and the stratified anatomy for the 361 acupuncture points of 14 channels.

    Science.gov (United States)

    Chapple, Will

    2013-10-01

    In spite of the extensive research on acupuncture mechanisms, no comprehensive and systematic peer-reviewed reference list of the stratified anatomical and the neuroanatomical features of all 361 acupuncture points exists. This study creates a reference list of the neuroanatomy and the stratified anatomy for each of the 361 acupuncture points on the 14 classical channels and for 34 extra points. Each acupuncture point was individually assessed to relate the point's location to anatomical and neuroanatomical features. The design of the catalogue is intended to be useful for any style of acupuncture or Oriental medicine treatment modality. The stratified anatomy was divided into shallow, intermediate and deep insertion. A separate stratified anatomy was presented for different needle angles and directions. The following are identified for each point: additional specifications for point location, the stratified anatomy, motor innervation, cutaneous nerve and sensory innervation, dermatomes, Langer's lines, and somatotopic organization in the primary sensory and motor cortices. Acupuncture points for each muscle, dermatome and myotome are also reported. This reference list can aid clinicians, practitioners and researchers in furthering the understanding and accurate practice of acupuncture. Additional research on the anatomical variability around acupuncture points, the frequency of needle contact with an anatomical structure in a clinical setting, and conformational imaging should be done to verify this catalogue. Copyright © 2013. Published by Elsevier B.V.

  14. Homogeneous and Stratified Liquid-Liquid Flow Effect of a Viscosity Reducer: I. Comparison in parallel plates for heavy crude

    Directory of Open Access Journals (Sweden)

    E. J. Suarez-Dominguez

    2016-12-01

    Full Text Available Production of heavy crude oil in Mexico, and worldwide, is increasing which has led to the application of different methods to reduce viscosity or to enhance transport through stratified flow to continue using the existing infrastructures. In this context, injecting a viscosity improver that does not mix completely with the crude, establishes a liquid-liquid stratified flow. On the basis of a parallel plates model, comparing the increase of flow that occurs in the one-phase case which assumes a complete mixture between the crude and the viscosity improver against another stratified liquid-liquid (no mixing between the oil and compared improver; it was found that in both cases there is a flow increase for the same pressure drop with a maximum for the case in which the flow improver is between the plates and the crude.

  15. A study on the instability criterion for the stratified flow in horizontal pipe at cocurrent flow conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sung, Chang Kyung [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

    1997-12-31

    This paper presents a theoretical approach of the instability criterion from stratified to nonstratified flow in horizontal pipe at cocurrent flow conditions. The new theoretical instability criterion for the stratified and nonstratified flow transition in horizontal pipe has been developed by hyperbolic equations in two-phase flow. Critical flow condition criterion and onset of slugging at cocurrent flow condition correspond to zero and imaginary characteristics which occur when the hyperbolicity of a stratified two-phase flow is broken, respectively. Through comparison between results predicted by the present flow is broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al. [1] experimental data of pipes, it is shown that they are in good agreement with data. 4 refs., 2 figs. (Author)

  16. A study on the instability criterion for the stratified flow in horizontal pipe at cocurrent flow conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sung, Chang Kyung [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

    1998-12-31

    This paper presents a theoretical approach of the instability criterion from stratified to nonstratified flow in horizontal pipe at cocurrent flow conditions. The new theoretical instability criterion for the stratified and nonstratified flow transition in horizontal pipe has been developed by hyperbolic equations in two-phase flow. Critical flow condition criterion and onset of slugging at cocurrent flow condition correspond to zero and imaginary characteristics which occur when the hyperbolicity of a stratified two-phase flow is broken, respectively. Through comparison between results predicted by the present flow is broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al. [1] experimental data of pipes, it is shown that they are in good agreement with data. 4 refs., 2 figs. (Author)

  17. Experimental investigation of droplet separation in a horizontal counter-current air/water stratified flow

    International Nuclear Information System (INIS)

    Gabriel, Stephan Gerhard

    2015-01-01

    A stratified counter-current two-phase gas/liquid flow can occur in various technical systems. In the past investigations have mainly been motivated by the possible occurrence of these flows in accident scenarios of nuclear light water-reactors and in numerous applications in process engineering. However, the precise forecast of flow parameters, is still challenging, for instance due to their strong dependency on the geometric boundary conditions. A new approach which uses CFD methods (Computational Fluid Dynamics) promises a better understanding of the flow phenomena and simultaneously a higher scalability of the findings. RANS methods (Reynolds Averaged Navier Stokes) are preferred in order to compute industrial processes and geometries. A very deep understanding of the flow behavior and equation systems based on real physics are necessary preconditions to develop the equation system for a reliable RANS approach with predictive power. Therefore, local highly resolved, experimental data is needed in order to provide and validate the required turbulence and phase interaction models. The central objective of this work is to provide the data needed for the code development for these unsteady, turbulent and three-dimensional flows. Experiments were carried out at the WENKA facility (Water Entrainment Channel Karlsruhe) at the Karlsruhe Institute of Technology (KIT). The work consists of a detailed description of the test-facility including a new bended channel, the measurement techniques and the experimental results. The characterization of the new channel was done by flow maps. A high-speed imaging study gives an impression of the occurring flow regimes, and different flow phenomena like droplet separation. The velocity distributions as well as various turbulence values were investigated by particle image velocimetry (PIV). In the liquid phase fluorescent tracer-particles were used to suppress optical reflections from the phase surface (fluorescent PIV, FPIV

  18. Spectral transfer functions of body waves propagating through a stratified medium. Part 1: Basic theory by means of matrix propagators

    International Nuclear Information System (INIS)

    Macia, R.; Correig, A.M.

    1987-01-01

    Seismic wave propagation is described by a second order differential equation for medium displacement. By Fourier transforming with respect to time and space, wave equation transforms into a system of first order linear differential equations for the Fourier transform of displacement and stress. This system of differential equations is solved by means of Matrix Propagator and applied to the propagation of body waves in stratified media. The matrix propagators corresponding to P-SV and SH waves in homogeneous medium are found as an intermediate step to obtain the spectral response of body waves propagating through a stratified medium with homogeneous layers. (author) 14 refs

  19. Stability of interfacial waves in two-phase flows

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W S [Ontario Hydro, Toronto, ON (Canada)

    1996-12-31

    The influence of the interfacial pressure and the flow distribution in the one-dimensional two-fluid model on the stability problems of interfacial waves is discussed. With a proper formulation of the interfacial pressure, the following two-phase phenomena can be predicted from the stability and stationary criteria of the interfacial waves: onset of slug flow, stationary hydraulic jump in a stratified flow, flooding in a vertical pipe, and the critical void fraction of a bubbly flow. It can be concluded that the interfacial pressure plays an important role in the interfacial wave propagation of the two-fluid model. The flow distribution parameter may enhance the flow stability range, but only plays a minor role in the two-phase characteristics. (author). 20 refs., 3 tabs., 4 figs.

  20. Prediction of stably stratified homogeneous shear flows with second-order turbulence models

    International Nuclear Information System (INIS)

    Pereira, J C F; Rocha, J M P

    2010-01-01

    The present study investigated the role of pressure-correlation second-order turbulence modelling schemes on the predicted behaviour of stably stratified homogeneous vertical-sheared turbulence. The pressure-correlation terms were modelled with a nonlinear formulation (Craft 1991), which was compared with a linear pressure-strain model and the 'isotropization of production' model for the pressure-scalar correlation. Two additional modelling issues were investigated: the influence of the buoyancy term in the kinetic energy dissipation rate equation and the time scale in the thermal production term in the scalar variance dissipation equation. The predicted effects of increasing the Richardson number on turbulence characteristics were compared against a comprehensive set of direct numerical simulation databases. The linear models provide a broadly satisfactory description of the major effects of the Richardson number on stratified shear flow. The buoyancy term in the dissipation equation of the turbulent kinetic energy generates excessively low levels of dissipation. For moderate and large Richardson numbers, the term yields unrealistic linear oscillations in the shear and buoyancy production terms, and therefore should be dropped in this flow (or at least their coefficient c ε3 should be substantially reduced from its standard value). The mechanical dissipation time scale provides marginal improvements in comparison to the scalar time scale in the production. The observed inaccuracy of the linear model in predicting the magnitude of the effects on the velocity anisotropy was demonstrated to be attributed mainly to the defective behaviour of the pressure-correlation model, especially for stronger stratification. The turbulence closure embodying a nonlinear formulation for the pressure-correlations and specific versions of the dissipation equations failed to predict the tendency of the flow to anisotropy with increasing stratification. By isolating the effects of the

  1. Monoplane 3D-2D registration of cerebral angiograms based on multi-objective stratified optimization

    Science.gov (United States)

    Aksoy, T.; Špiclin, Ž.; Pernuš, F.; Unal, G.

    2017-12-01

    Registration of 3D pre-interventional to 2D intra-interventional medical images has an increasingly important role in surgical planning, navigation and treatment, because it enables the physician to co-locate depth information given by pre-interventional 3D images with the live information in intra-interventional 2D images such as x-ray. Most tasks during image-guided interventions are carried out under a monoplane x-ray, which is a highly ill-posed problem for state-of-the-art 3D to 2D registration methods. To address the problem of rigid 3D-2D monoplane registration we propose a novel multi-objective stratified parameter optimization, wherein a small set of high-magnitude intensity gradients are matched between the 3D and 2D images. The stratified parameter optimization matches rotation templates to depth templates, first sampled from projected 3D gradients and second from the 2D image gradients, so as to recover 3D rigid-body rotations and out-of-plane translation. The objective for matching was the gradient magnitude correlation coefficient, which is invariant to in-plane translation. The in-plane translations are then found by locating the maximum of the gradient phase correlation between the best matching pair of rotation and depth templates. On twenty pairs of 3D and 2D images of ten patients undergoing cerebral endovascular image-guided intervention the 3D to monoplane 2D registration experiments were setup with a rather high range of initial mean target registration error from 0 to 100 mm. The proposed method effectively reduced the registration error to below 2 mm, which was further refined by a fast iterative method and resulted in a high final registration accuracy (0.40 mm) and high success rate (> 96%). Taking into account a fast execution time below 10 s, the observed performance of the proposed method shows a high potential for application into clinical image-guidance systems.

  2. Hydrogeology and water quality of the Nanticoke Creek stratified-drift aquifer, near Endicott, New York

    Science.gov (United States)

    Kreitinger, Elizabeth A.; Kappel, William M.

    2014-01-01

    The Village of Endicott, New York, is seeking an alternate source of public drinking water with the potential to supplement their current supply, which requires treatment due to legacy contamination. The southerly-draining Nanticoke Creek valley, located north of the village, was identified as a potential water source and the local stratified-drift (valley fill) aquifer was investigated to determine its hydrogeologic and water-quality characteristics. Nanticoke Creek and its aquifer extend from the hamlet of Glen Aubrey, N.Y., to the village of Endicott, a distance of about 15 miles, where it joins the Susquehanna River and its aquifer. The glacial sediments that comprise the stratified-drift aquifer vary in thickness and are generally underlain by glacial till over Devonian-aged shale and siltstone. Groundwater is more plentiful in the northern part of the aquifer where sand and gravel deposits are generally more permeable than in the southern part of the aquifer where less-permeable unconsolidated deposits are found. Generally there is enough groundwater to supply most homeowner wells and in some cases, supply small public-water systems such as schools, mobile-home parks, and small commercial/industrial facilities. The aquifer is recharged by precipitation, runoff, and tributary streams. Most tributary streams flowing across alluvial deposits lose water to the aquifer as they flow off of their bedrock-lined channels and into the more permeable alluvial deposits at the edges of the valley. The quality of both surface water and groundwater is generally good. Some water wells do have water-quality issues related to natural constituents (manganese and iron) and several homeowners noted either the smell and (or) taste of hydrogen sulfide in their drinking water. Dissolved methane concentrations from five drinking-water wells were well below the potentially explosive value of 28 milligrams per liter. Samples from surface and groundwater met nearly all State and Federal

  3. A Clinical Prediction Algorithm to Stratify Pediatric Musculoskeletal Infection by Severity

    Science.gov (United States)

    Benvenuti, Michael A; An, Thomas J; Mignemi, Megan E; Martus, Jeffrey E; Mencio, Gregory A; Lovejoy, Stephen A; Thomsen, Isaac P; Schoenecker, Jonathan G; Williams, Derek J

    2016-01-01

    Objective There are currently no algorithms for early stratification of pediatric musculoskeletal infection (MSKI) severity that are applicable to all types of tissue involvement. In this study, the authors sought to develop a clinical prediction algorithm that accurately stratifies infection severity based on clinical and laboratory data at presentation to the emergency department. Methods An IRB-approved retrospective review was conducted to identify patients aged 0–18 who presented to the pediatric emergency department at a tertiary care children’s hospital with concern for acute MSKI over a five-year period (2008–2013). Qualifying records were reviewed to obtain clinical and laboratory data and to classify in-hospital outcomes using a three-tiered severity stratification system. Ordinal regression was used to estimate risk for each outcome. Candidate predictors included age, temperature, respiratory rate, heart rate, C-reactive protein, and peripheral white blood cell count. We fit fully specified (all predictors) and reduced models (retaining predictors with a p-value ≤ 0.2). Discriminatory power of the models was assessed using the concordance (c)-index. Results Of the 273 identified children, 191 (70%) met inclusion criteria. Median age was 5.8 years. Outcomes included 47 (25%) children with inflammation only, 41 (21%) with local infection, and 103 (54%) with disseminated infection. Both the full and reduced models accurately demonstrated excellent performance (full model c-index 0.83, 95% CI [0.79–0.88]; reduced model 0.83, 95% CI [0.78–0.87]). Model fit was also similar, indicating preference for the reduced model. Variables in this model included C-reactive protein, pulse, temperature, and an interaction term for pulse and temperature. The odds of a more severe outcome increased by 30% for every 10-unit increase in C-reactive protein. Conclusions Clinical and laboratory data obtained in the emergency department may be used to accurately

  4. Heat and mass transfer in the stratified flow with ECCS injection

    International Nuclear Information System (INIS)

    Strubelj, L.; Tiselj, I.

    2007-01-01

    One of the most important problems in the light-water nuclear thermal-hydraulics is behaviour of the cold emergency core cooling water injected from the top or from the bottom into the horizontal section of the cold leg near the reactor vessel during the loss of coolant accident. The stratified flows appear where cold water is injected in partially or fully uncovered horizontal cold leg. The hot steam condenses on cold water surface what is also called direct contact condensation. Direct contact condensation and condensation induced water-hammer in a horizontal pipe were experimentally investigated at PMK-2 test facility of the Hungarian Atomic Energy Research Institute KFKI. The cold water is injected through small pipe into lower horizontal part of the section, and then water fills the vertical pipeline and floods the horizontal test section of the pipeline of the PMK-2 integral test facility. As liquid water floods the horizontal part of the pipeline, the counter current horizontally stratified flow is being observed. During the flooding of the pipeline, the steam-liquid interface area increases and therefore the steam condensation rate and the steam velocity also increase and can lead to bubble entrapment. Water level at one cross-section and four local void fraction and temperature at the top of horizontal test pipeline was measured and compared with simulation. Condensed steam increases the water temperature that is why the local temperature measurements are the most important information, from which condensation rate can be estimated, since mass of condensed steam was not measured. Numerical simulation of the experiment with thermal phase change is presented. Surface renewal concept with small eddies is used for calculation of condensation heat transfer coefficient. Two simulations were performed: simulation of whole experimental domain (lower horizontal, vertical and test horizontal pipeline) and simplified simulation of only upper horizontal test section

  5. Experimental investigation on the droplet entrainment from interfacial waves in air-water horizontal stratified flow

    International Nuclear Information System (INIS)

    Bae, Byeong Geon; Yun, Byong Jo; Kim, Kyoung Du

    2014-01-01

    It was mainly due to the fact that droplet entrainment affects the Peak Cladding Temperature (PCT) of the nuclear fuel rod in the Postulated accident conditions of NPP. Recently, droplet entrainment in the horizontally arranged primary piping system for the NPP is of interest because it affects directly the steam binding phenomena in the steam generators. Pan and Hanratty correlation is the only applicable one for the droplet entrainment rate model for horizontal flow. Moreover, there are no efforts for the model development on the basis of the droplet entrainment principal and physics phenomena. More recently, Korea Atomic Energy Research Institute (KAERI) proposed a new mechanistic droplet generation model applicable in the horizontal pipe for the SPACE code. However, constitutive relations in this new model require three model coefficients which have not yet been decided. The purpose of present work is determining three model coefficients by visualization experiment. For these model coefficients, the major physical parameters regarding the interfacial disturbance wave should be measured in this experiments. There are the wave slope, liquid fraction, wave hypotenuse length, wave velocity, wave frequency, and wavelength in the major physical parameters. The experiment was conducted at an air water horizontal rectangular channel with the PIV system. In this study, the experimental conditions were stratified-way flow during the droplet generation. Three coefficients were determined based on several data related to the interfacial wave. Additionally, we manufactured the parallel wire conductance probe to measure the fluctuating water level over time, and compared the wave height measured by the parallel wire conductance probe and image processing from images taken by high speed camera. Experimental investigation was performed for droplet entrainment from phase interface wave in an air-water stratified flow. In the experiments, we measured major physical parameters

  6. Implications of Stably Stratified Atmospheric Boundary Layer Turbulence on the Near-Wake Structure of Wind Turbines

    Directory of Open Access Journals (Sweden)

    Kiran Bhaganagar

    2014-09-01

    Full Text Available Turbulence structure in the wake behind a full-scale horizontal-axis wind turbine under the influence of real-time atmospheric inflow conditions has been investigated using actuator-line-model based large-eddy-simulations. Precursor atmospheric boundary layer (ABL simulations have been performed to obtain mean and turbulence states of the atmosphere under stable stratification subjected to two different cooling rates. Wind turbine simulations have revealed that, in addition to wind shear and ABL turbulence, height-varying wind angle and low-level jets are ABL metrics that influence the structure of the turbine wake. Increasing stability results in shallower boundary layers with stronger wind shear, steeper vertical wind angle gradients, lower turbulence, and suppressed vertical motions. A turbulent mixing layer forms downstream of the wind turbines, the strength and size of which decreases with increasing stability. Height dependent wind angle and turbulence are the ABL metrics influencing the lateral wake expansion. Further, ABL metrics strongly impact the evolution of tip and root vortices formed behind the rotor. Two factors play an important role in wake meandering: tip vortex merging due to the mutual inductance form of instability and the corresponding instability of the turbulent mixing layer.

  7. Stability of Dolos Slopes

    DEFF Research Database (Denmark)

    Brorsen, Michael; Burcharth, Hans F.; Larsen, Torben

    The stability of dolos armour blocks against wave attack has been investigated in wave model studies.......The stability of dolos armour blocks against wave attack has been investigated in wave model studies....

  8. Stability of parallel flows

    CERN Document Server

    Betchov, R

    2012-01-01

    Stability of Parallel Flows provides information pertinent to hydrodynamical stability. This book explores the stability problems that occur in various fields, including electronics, mechanics, oceanography, administration, economics, as well as naval and aeronautical engineering. Organized into two parts encompassing 10 chapters, this book starts with an overview of the general equations of a two-dimensional incompressible flow. This text then explores the stability of a laminar boundary layer and presents the equation of the inviscid approximation. Other chapters present the general equation

  9. Regulation of two loblolly pine (Pinus taeda L.) isocitrate lyase genes in megagametophytes of mature and stratified seeds and during postgerminative growth.

    Science.gov (United States)

    Mullen, R T; Gifford, D J

    1997-03-01

    Two full-length cDNAs encoding the glyoxysomal enzyme isocitrate lyase (ICL) were isolated from a lambda ZAP cDNA library prepared from megagametophyte mRNAs extracted from seeds imbibed at 30 degrees C for 8 days. The cDNAs, designated Ptbs ICL 8 and Ptbs ICL 12, have open reading frames of 1740 and 1719 bp, with deduced amino acid sequences of 580 and 573 residues, respectively. The predicted amino acid sequences of Ptbs ICL 8 and Ptbs ICL 12 exhibit a 79% identity with each other, and have a greater than 75% identity with ICLs from various angiosperm species. The C-termini of Ptbs ICL 8 and Ptbs ICL 12 terminate with the tripeptide Ser-Arg-Met and Ala-Arg-Met, respectively, both being conserved variants of the type 1 peroxisomal targeting signal. RNA blot and slot analysis revealed that Ptbs ICL 8 and Ptbs ICL 12 mRNAs were present at low levels in the megagametophyte of the mature and stratified seeds, and that the level of both transcripts increased markedly upon seed germination. Protein blot analysis indicated that the steady-state level of ICL was low in the mature and stratified seed, then increased rapidly upon seed germination, peaking at around 8-10 days after imbibition (DAI). Changes in the level of ICL activity in cell-free extracts was similar to the steady-state protein content with the exception that ICL activity was not detected in megagametophyte extracts of mature or stratified seeds. From 10-12 DAI when the megagametophyte tissue senesced, ICL activity decreased rapidly to near undetectable levels. In contrast, steady-state levels of ICL protein and mRNA remained relatively constant during megagametophyte senescence. In vivo synthesis of ICL protein was measured to shed light on these differences. ICL immunoselected from [(35)S]-methionine labelled proteins indicated that ICL was synthesized at very low levels during megagametophyte senescence. Together, the results show that loblolly pine ICL gene expression is complex. While temporal

  10. Dynamic measurement of liquid film thickness in stratified flow by using ultrasonic echo technique

    International Nuclear Information System (INIS)

    Serizawa, A.; Nagane, K.; Kamei, T.; Kawara, Z.; Ebisu, T.; Torikoshi, K.

    2004-01-01

    We developed a technique to measure time-dependent local film thickness in stratified air-water flow over a horizontal plate by using a time of flight of ultrasonic transmission. The ultrasonic echoes reflected at the liquid/air interfaces are detected by a conventional ultrasonic instrumentation, and the signals are analyzed by a personal computer after being digitalized by an A/D converter to give the time of flight for the ultrasonic waves to run over a distance of twice of the film thickness. A 3.8 mm diameter probe type ultrasonic transducer was used in the present work which transmits and receives 10 MHz frequency ultrasonic waves. The estimated spatial resolution with this arrangement is 0.075 mm in film thickness for water. The time resolution, which depends on both the A/D converter and the memory capacity was up to several tens Hz. We also discussed the sensitivity of the method to the inclination angle of the interfaces. (author)

  11. Modélisation macroscopique des milieux stratifiés conducteurs

    Science.gov (United States)

    Matagne, E.; Conard, J. Ph.

    1997-11-01

    Many laminated structures are recognised in Electrotechnics : magnetic cores, flat conductors windings, slotted surfaces... These structures exhibit macroscopic properties, as magnetic than electric ones. This paper shows how these characteristics can be obtained by homogenisation. It deals with linear materials but taking into account the effect of eddy currents, as well on the macroscopic magnetic permeability as on the macroscopic electric conductivity, which become then complex numbers. An example of use of the macroscopic properties is provided. On peut identifier en électrotechnique de nombreuses structures stratifiées: noyaux magnétiques, bobinages formés de conducteurs plats, surfaces encochées... Ces structures présentent des propriétés macroscopiques tant magnétiques qu'électriques. Cet article montre comment ces caractéristiques peuvent être obtenues par homogénéisation. Il se limite au cas de matériaux linéaires mais en prenant en compte l'effet des courants de Foucault aussi bien sur la perméabilité magnétique macroscopique que sur la conductivité électrique macroscopique, grandeurs qui deviennent alors des nombres complexes. Un exemple d'utilisation des caractéristiques macroscopiques est fourni.

  12. Gambling problems in the family – A stratified probability sample study of prevalence and reported consequences

    Directory of Open Access Journals (Sweden)

    Øren Anita

    2008-12-01

    Full Text Available Abstract Background Prior studies on the impact of problem gambling in the family mainly include help-seeking populations with small numbers of participants. The objective of the present stratified probability sample study was to explore the epidemiology of problem gambling in the family in the general population. Methods Men and women 16–74 years-old randomly selected from the Norwegian national population database received an invitation to participate in this postal questionnaire study. The response rate was 36.1% (3,483/9,638. Given the lack of validated criteria, two survey questions ("Have you ever noticed that a close relative spent more and more money on gambling?" and "Have you ever experienced that a close relative lied to you about how much he/she gambles?" were extrapolated from the Lie/Bet Screen for pathological gambling. Respondents answering "yes" to both questions were defined as Concerned Significant Others (CSOs. Results Overall, 2.0% of the study population was defined as CSOs. Young age, female gender, and divorced marital status were factors positively associated with being a CSO. CSOs often reported to have experienced conflicts in the family related to gambling, worsening of the family's financial situation, and impaired mental and physical health. Conclusion Problematic gambling behaviour not only affects the gambling individual but also has a strong impact on the quality of life of family members.

  13. Results of a systematic literature review of treatment modalities for jugulotympanic paraganglioma, stratified per Fisch class.

    Science.gov (United States)

    Jansen, T T G; Timmers, H J L M; Marres, H A M; Kaanders, J H A M; Kunst, H P M

    2018-04-01

    Key for successful jugulotympanic paraganglioma management is a personalised approach aiming for the best practice for each individual patient. To this end, a systematic review is performed, evaluating the local control and complication rates for the different treatment modalities stratified by the broadly accepted Fisch classification. A systematic literature review according to the PRISMA statement was performed. A detailed overview of individual treatment outcomes per Fisch class is provided. Local control, cranial nerve damage, complications, function recovery. Eighteen studies were selected, resembling 83 patients treated with radiotherapy and 299 with surgery. Excellent local control was found post-surgery for class A and B tumours, and risk of cranial nerve damage was class C1-4 tumours, local control was 80%-95% post-surgery (84% post-radiotherapy), and cranial nerve damage was found in 71%-76% (none post-radiotherapy; P class. For class C1-4De/Di tumours, local control was 38%-86% (98% post-radiotherapy; P class. For class A and B tumours, surgery is a suitable treatment option. For class C and D tumours, radiotherapy results in lower complication rates and similar or better local control rates when compared to the surgical group. © 2017 John Wiley & Sons Ltd.

  14. Characterization and modeling of turbidity density plume induced into stratified reservoir by flood runoffs.

    Science.gov (United States)

    Chung, S W; Lee, H S

    2009-01-01

    In monsoon climate area, turbidity flows typically induced by flood runoffs cause numerous environmental impacts such as impairment of fish habitat and river attraction, and degradation of water supply efficiency. This study was aimed to characterize the physical dynamics of turbidity plume induced into a stratified reservoir using field monitoring and numerical simulations, and to assess the effect of different withdrawal scenarios on the control of downstream water quality. Three different turbidity models (RUN1, RUN2, RUN3) were developed based on a two-dimensional laterally averaged hydrodynamic and transport model, and validated against field data. RUN1 assumed constant settling velocity of suspended sediment, while RUN2 estimated the settling velocity as a function of particle size, density, and water temperature to consider vertical stratification. RUN3 included a lumped first-order turbidity attenuation rate taking into account the effects of particles aggregation and degradable organic particles. RUN3 showed best performance in replicating the observed variations of in-reservoir and release turbidity. Numerical experiments implemented to assess the effectiveness of different withdrawal depths showed that the alterations of withdrawal depth can modify the pathway and flow regimes of the turbidity plume, but its effect on the control of release water quality could be trivial.

  15. Interfacial friction factors for air-water co-current stratified flow in inclined channels

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Ki Yong; No, Hee Cheon [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1997-12-31

    The interfacial shear stress is experimentally investigated for co-current air-water stratified flow in inclined rectangular channels having a length of 1854mm, width of 120 mm and height of 40mm at almost atmospheric pressure. Experiments are carried out in several inclinations from 0 deg up to 10 deg. The local film thickness and the wave height are measured at three locations, i.e., L/H = 8,23, and 40. According to the inclination angle, the experimental data are categorized into two groups; nearly horizontal data group (0 deg {<=} {theta} {<=} 0.7 deg), and inclined channel data group (0.7 deg {<=} {theta} {<=} 10 deg ). Experimental observations for nearly horizontal data group show that the flow is not fully developed due to the water level gradient and the hydraulic jump within the channel. For the inclined channel data group, a dimensionless wave height, {Delta}h/h, is empirically correlated in terms of Re{sub G} and h/H. A modified root-mean-square wave height is proposed to consider the effects of the interfacial and wave propagation velocities. It is found that an equivalent roughness has a linear relationship with the modified root-mean-square wave height and its relationship is independent of the inclination. 10 refs., 6 figs., 1 tab. (Author)

  16. Numerical Simulations of Upstream Propagating Solitary Waves and Wave Breaking In A Stratified Fjord

    Science.gov (United States)

    Stastna, M.; Peltier, W. R.

    In this talk we will discuss ongoing numerical modeling of the flow of a stratified fluid over large scale topography motivated by observations in Knight Inlet, a fjord in British Columbia, Canada. After briefly surveying the work done on the topic in the past we will discuss our latest set of simulations in which we have observed the gener- ation and breaking of three different types of nonlinear internal waves in the lee of the sill topography. The first type of wave observed is a large lee wave in the weakly strat- ified main portion of the water column, The second is an upward propagating internal wave forced by topography that breaks in the strong, near-surface pycnocline. The third is a train of upstream propagating solitary waves that, in certain circumstances, form as breaking waves consisting of a nearly solitary wave envelope and a highly unsteady core near the surface. Time premitting, we will comment on the implications of these results for our long term goal of quantifying tidally driven mixing in Knight Inlet.

  17. Study of volume fractions on biphasic stratified regime using gamma ray

    Energy Technology Data Exchange (ETDEWEB)

    Salgado, William L.; Brandão, Luis E.B., E-mail: william.otero@hotmail.com, E-mail: brandao@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2017-07-01

    In the oil industries, interconnected pipelines are used to carry large quantities of petroleum and its byproducts. This modal has an advantage because they are more economical, eliminate a need for stocks and, in addition, great safety in operation minimizing a possibility of loss or theft when transported another way. In many cases, especially in the petrochemical industry, the same pipeline is used to carry more than one type of product. They are called poliduct. In the operation of a poliduct there is a sequence of products to be transported and during the exchange of the product, there are still fractions of the previous product and this generates contamination. It is therefore important to identify precisely this region in order to reduce the costs of reprocessing and treatment of discarded products. In this way, this work presents a methodology to evaluate the sensitivity of the gamma densitometry technique in a study of the calculation of volume fractions in biphasic systems, submitted to the stratified flow regime. Using computational simulations using the Monte Carlo Method with the MCNPX code measurement geometry was proposed that presented a higher sensitivity for the calculation of volume fractions. The relevant technical data to perform a simulation of the scintillator detectors were based on information obtained from the gammagraphy technique. The study had a theoretical validation through analytical equations, and the results show that it is possible to identify volume fractions equivalent to 3%. (author)

  18. Light-Dependent Aerobic Methane Oxidation Reduces Methane Emissions from Seasonally Stratified Lakes

    Science.gov (United States)

    Oswald, Kirsten; Milucka, Jana; Brand, Andreas; Littmann, Sten; Wehrli, Bernhard; Kuypers, Marcel M. M.; Schubert, Carsten J.

    2015-01-01

    Lakes are a natural source of methane to the atmosphere and contribute significantly to total emissions compared to the oceans. Controls on methane emissions from lake surfaces, particularly biotic processes within anoxic hypolimnia, are only partially understood. Here we investigated biological methane oxidation in the water column of the seasonally stratified Lake Rotsee. A zone of methane oxidation extending from the oxic/anoxic interface into anoxic waters was identified by chemical profiling of oxygen, methane and δ13C of methane. Incubation experiments with 13C-methane yielded highest oxidation rates within the oxycline, and comparable rates were measured in anoxic waters. Despite predominantly anoxic conditions within the zone of methane oxidation, known groups of anaerobic methanotrophic archaea were conspicuously absent. Instead, aerobic gammaproteobacterial methanotrophs were identified as the active methane oxidizers. In addition, continuous oxidation and maximum rates always occurred under light conditions. These findings, along with the detection of chlorophyll a, suggest that aerobic methane oxidation is tightly coupled to light-dependent photosynthetic oxygen production both at the oxycline and in the anoxic bottom layer. It is likely that this interaction between oxygenic phototrophs and aerobic methanotrophs represents a widespread mechanism by which methane is oxidized in lake water, thus diminishing its release into the atmosphere. PMID:26193458

  19. Community structure of benthic macroinvertebrates inhabiting a highly stratified Mediterranean estuary

    Directory of Open Access Journals (Sweden)

    Alfonso Nebra

    2011-04-01

    Full Text Available The community composition and spatial distribution of benthic macroinvertebrates were studied along the Ebro estuary, a highly stratified estuary located in the NE Iberian Peninsula. During the last decade the oligotrophication process occurring in the lower Ebro River and its estuary has allowed a complex benthic macroinvertebrate community to become established; these results contrast with the poor community found there in the early nineties. A total of 214 taxa were identified, and polychaetes dominated the community both in abundance and species richness. The results showed spatial differences in the structure and composition of macroinvertebrates, which suggests that there are two distinct communities along the estuary. Each community was found in a specific stretch (upper and lower estuary in function of the presence of the salt wedge. The macrobenthos of the upper estuary was dominated by freshwater taxa, but some euryhaline species were also found. The lower estuary showed a marine community typical of shallow Mediterranean environments. The transition between these two communities fits an ecotone model. The highest abundances, richness and diversities were recorded at the lower estuarine stations, especially those closer to the river mouth, whereas the lowest values corresponded to the stations adjacent to the tip of the salt wedge.

  20. Resolution of thermal striping issue downstream of a horizontal pipe elbow in stratified pipe flow

    International Nuclear Information System (INIS)

    Kuzay, T.M.; Kasza, K.E.

    1985-01-01

    A thermally stratified pipe flow produced by a thermal transient when passing through a horizontal elbow as a result of secondary flow gives rise to large thermal fluctuations on the inner curvature wall of the downstream piping. These fluctuations were measured in a specially instrumented horizontal pipe and elbow system on a test set-up using water in the Mixing Components Technology Facility (MCTF) at Argonne National Laboratory (ANL). This study is part of a larger program which is studying the influence of thermal buoyancy on general reactor component performance. This paper discusses the influence of pipe flow generated thermal oscillations on the thermal stresses induced in the pipe walls. The instrumentation was concentrated around the exit plane of the 90 0 sweep elbow, since prior tests had indicated that the largest thermal fluctuations would occur within about one hydraulic diameter downstream of the elbow exit. The thermocouples were located along the inner curvature of the piping and measured the near surface fluid temperature. The test matrix involved thermal downramps under turbulent flow conditions

  1. Resolution of thermal striping issue downstream of a horizontal pipe elbow in stratified pipe flow. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Kuzay, T.M.; Kasza, K.E.

    1985-01-01

    A thermally stratified pipe flow produced by a thermal transient when passing through a horizontal elbow as a result of secondary flow gives rise to large thermal fluctuations on the inner curvature wall of the downstream piping. These fluctuations were measured in a specially instrumented horizontal pipe and elbow system on a test set-up using water in the Mixing Components Technology Facility (MCTF) at Argonne National Laboratory (ANL). This study is part of a larger program which is studying the influence of thermal buoyancy on general reactor component performance. This paper discusses the influence of pipe flow generated thermal oscillations on the thermal stresses induced in the pipe walls. The instrumentation was concentrated around the exit plane of the 90/sup 0/ sweep elbow, since prior tests had indicated that the largest thermal fluctuations would occur within about one hydraulic diameter downstream of the elbow exit. The thermocouples were located along the inner curvature of the piping and measured the near surface fluid temperature. The test matrix involved thermal downramps under turbulent flow conditions.

  2. Health service accreditation as a predictor of clinical and organisational performance: a blinded, random, stratified study.

    Science.gov (United States)

    Braithwaite, Jeffrey; Greenfield, David; Westbrook, Johanna; Pawsey, Marjorie; Westbrook, Mary; Gibberd, Robert; Naylor, Justine; Nathan, Sally; Robinson, Maureen; Runciman, Bill; Jackson, Margaret; Travaglia, Joanne; Johnston, Brian; Yen, Desmond; McDonald, Heather; Low, Lena; Redman, Sally; Johnson, Betty; Corbett, Angus; Hennessy, Darlene; Clark, John; Lancaster, Judie

    2010-02-01

    Despite the widespread use of accreditation in many countries, and prevailing beliefs that accreditation is associated with variables contributing to clinical care and organisational outcomes, little systematic research has been conducted to examine its validity as a predictor of healthcare performance. To determine whether accreditation performance is associated with self-reported clinical performance and independent ratings of four aspects of organisational performance. Independent blinded assessment of these variables in a random, stratified sample of health service organisations. Acute care: large, medium and small health-service organisations in Australia. Study participants Nineteen health service organisations employing 16 448 staff treating 321 289 inpatients and 1 971 087 non-inpatient services annually, representing approximately 5% of the Australian acute care health system. Correlations of accreditation performance with organisational culture, organisational climate, consumer involvement, leadership and clinical performance. Results Accreditation performance was significantly positively correlated with organisational culture (rho=0.618, p=0.005) and leadership (rho=0.616, p=0.005). There was a trend between accreditation and clinical performance (rho=0.450, p=0.080). Accreditation was unrelated to organisational climate (rho=0.378, p=0.110) and consumer involvement (rho=0.215, p=0.377). Accreditation results predict leadership behaviours and cultural characteristics of healthcare organisations but not organisational climate or consumer participation, and a positive trend between accreditation and clinical performance is noted.

  3. Shocks and currents in stratified atmospheres with a magnetic null point

    Science.gov (United States)

    Tarr, Lucas A.; Linton, Mark

    2017-08-01

    We use the resistive MHD code LARE (Arber et al 2001) to inject a compressive MHD wavepacket into a stratified atmosphere that has a single magnetic null point, as recently described in Tarr et al 2017. The 2.5D simulation represents a slice through a small ephemeral region or area of plage. The strong gradients in field strength and connectivity related to the presence of the null produce substantially different dynamics compared to the more slowly varying fields typically used in simple sunspot models. The wave-null interaction produces a fast mode shock that collapses the null into a current sheet and generates a set of outward propagating (from the null) slow mode shocks confined to field lines near each separatrix. A combination of oscillatory reconnection and shock dissipation ultimately raise the plasma's internal energy at the null and along each separatrix by 25-50% above the background. The resulting pressure gradients must be balanced by Lorentz forces, so that the final state has contact discontinuities along each separatrix and a persistent current at the null. The simulation demonstrates that fast and slow mode waves localize currents to the topologically important locations of the field, just as their Alfvenic counterparts do, and also illustrates the necessity of treating waves and reconnection as coupled phenomena.

  4. Interfacial friction factors for air-water co-current stratified flow in inclined channels

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Ki Yong; No, Hee Cheon [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1998-12-31

    The interfacial shear stress is experimentally investigated for co-current air-water stratified flow in inclined rectangular channels having a length of 1854mm, width of 120 mm and height of 40mm at almost atmospheric pressure. Experiments are carried out in several inclinations from 0 deg up to 10 deg. The local film thickness and the wave height are measured at three locations, i.e., L/H = 8,23, and 40. According to the inclination angle, the experimental data are categorized into two groups; nearly horizontal data group (0 deg {<=} {theta} {<=} 0.7 deg), and inclined channel data group (0.7 deg {<=} {theta} {<=} 10 deg ). Experimental observations for nearly horizontal data group show that the flow is not fully developed due to the water level gradient and the hydraulic jump within the channel. For the inclined channel data group, a dimensionless wave height, {Delta}h/h, is empirically correlated in terms of Re{sub G} and h/H. A modified root-mean-square wave height is proposed to consider the effects of the interfacial and wave propagation velocities. It is found that an equivalent roughness has a linear relationship with the modified root-mean-square wave height and its relationship is independent of the inclination. 10 refs., 6 figs., 1 tab. (Author)

  5. Estimation of gas wall shear stress in horizontal stratified gas-liquid pipe flow

    International Nuclear Information System (INIS)

    Newton, C.H.; Behnia, M.

    1996-01-01

    Two-phase pipe flows occur in many industrial applications, such as condensers and evaporators, chemical processing equipment, nuclear reactors, and oil pipelines. A variety of basic mechanistic flow models for predicting the pressure gradient and liquid loading characteristics of these types of flows to assist in design calculations has emerged over the past two decades, especially for the stratified and slug flow regimes. These models generally rely on a number of basic assumptions and empirical closure equations. Possibly the most notable of these relates to the evaluation of interfacial shear stresses. However, one of the most important yet least discussed assumptions used in most of these models is that the phase wall shear stresses can be accurately estimated from correlations developed for single-phase pipe flows. The object of this article is to present measurements of gas wall shear up to locations in close proximity to the gas-liquid interface for a variety of interface conditions in developed flow, and to determine the effects of the interface on average gas wall friction factors. In this context the interface may be smooth, rippled or wavy

  6. Influence of Propulsion Type on the Stratified Near Wake of an Axisymmetric Self-Propelled Body

    Directory of Open Access Journals (Sweden)

    Matthew C. Jones

    2018-05-01

    Full Text Available To better understand the influence of swirl on the thermally-stratified near wake of a self-propelled axisymmetric vehicle, three propulsor schemes were considered: a single propeller, contra-rotating propellers (CRP, and a zero-swirl, uniform-velocity jet. The propellers were modeled using an Actuator-Line model in an unsteady Reynolds-Averaged Navier–Stokes simulation, where the Reynolds number is R e L = 3.1 × 10 8 using the freestream velocity and body length. The authors previously showed good comparison to experimental data with this approach. Visualization of vortical structures shows the helical paths of blade-tip vortices from the single propeller as well as the complicated vortical interaction between contra-rotating blades. Comparison of instantaneous and time-averaged fields shows that temporally stationary fields emerge by half of a body length downstream. Circumferentially-averaged axial velocity profiles show similarities between the single propeller and CRP in contrast to the jet configuration. Swirl velocity of the CRP, however, was attenuated in comparison to that of the single propeller case. Mixed-patch contour maps illustrate the unique temperature distribution of each configuration as a consequence of their respective swirl profiles. Finally, kinetic and potential energy is integrated along downstream axial planes to reveal key differences between the configurations. The CRP configuration creates less potential energy by reducing swirl that would otherwise persist in the near wake of a single-propeller wake.

  7. Dual discharge from a stratified two-phase region through side orifices oriented horizontally

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, I G; Soliman, H M; Sims, G E [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Mechanical Engineering; Kowalski, J E [Atomic Energy of Canada Ltd., Pinawa, MB (Canada). Whiteshell Labs.

    1996-12-31

    Experimental data are presented for the mass flow rate and quality of two-phase (air-water) discharge from a stratified region through two side orifices (6.35 mm i.d.) with their parallel centre lines located in a horizontal plane. These data correspond to different values of the interface level between the onsets of gas and liquid entrainments for test-section pressures of 316 and 517 kPa, test-section-to-separators pressure difference ranging from 40 to 235 kPa, orifice separating distance to diameter ratio ranging from 1.5 to 8 and different hydraulic resistances of the lines connecting the test section to the separators. Influences of these independent variables on the deviation between the present results (of mass flow rate and quality) and those corresponding to a single discharge are presented and discussed. Normalized plots are presented showing that the present data of dual discharge and those of a single discharge can be collapsed for the whole test range when specific definition for the dimensionless height of the interface and mass flow rate are used. Excellent agreement is demonstrated between single-discharge correlations and the present data using these dimensionless quantities. (author). 12 refs., 1 tab., 16 figs.

  8. Psychosocial Distress in Bladder Cancer Stratified by Gender, Age, Treatment, and Tumour Stage.

    Science.gov (United States)

    Draeger, Désirée Louise; Sievert, Karl-Dietrich; Hakenberg, Oliver W

    2018-05-14

    Cancer patients have to cope with anxieties -concerning their prognosis, potential recurrence/progression, and treatment-associated sequelae. Stress-related psychosocial factors influence survival and disease-related mortality in cancer patients. Despite improvements in diagnosis and treatment, bladder cancer (BC) remains characterized by high rates of recurrence and progression. We screened -pre-therapeutically the stress level of BC patients stratified by gender, disease state, treatment, and other factors by -self-administered validated questionnaires to integrate them into psychosocial support as needed. A cross-sectional analysis of distress and need of psychosocial care was done in 301 patients undergoing treatment for BC by 2 questionnaires (Distress Thermometer [DT] and Hornheider Screening Instrument). Of the 301 patients, 230 patients underwent transurethral resection for a first -diagnosis, 63 for recurrent disease, 37 had progressive disease, and 25 had advanced metastatic disease and eventually died of BC. The mean stress level in all patients was 4.6. Twenty-eight percent of the patients expressed a need for psychosocial support. In patients with progressive disease, significantly higher stress scores were seen as well as a higher need of psychosocial care (5.4 and 41%). The median DT-level of 4.6 indicates moderate psychosocial stress in BC patients. From a stress level of 5, the recommendations of a psycho-oncological supervision are pronounced, so that our study showed that early systematic evaluation of psychosocial needs in BC patients is important. © 2018 S. Karger AG, Basel.

  9. Biogenic mixing induced by intermediate Reynolds number swimming in stratified fluids

    Science.gov (United States)

    Wang, Shiyan; Ardekani, Arezoo M.

    2015-01-01

    We study fully resolved motion of interacting swimmers in density stratified fluids using an archetypal swimming model called “squirmer”. The intermediate Reynolds number regime is particularly important, because the vast majority of organisms in the aphotic ocean (i.e. regions that are 200 m beneath the sea surface) are small (mm-cm) and their motion is governed by the balance of inertial and viscous forces. Our study shows that the mixing efficiency and the diapycnal eddy diffusivity, a measure of vertical mass flux, within a suspension of squirmers increases with Reynolds number. The mixing efficiency is in the range of O(0.0001–0.04) when the swimming Reynolds number is in the range of O(0.1–100). The values of diapycnal eddy diffusivity and Cox number are two orders of magnitude larger for vertically swimming cells compared to horizontally swimming cells. For a suspension of squirmers in a decaying isotropic turbulence, we find that the diapycnal eddy diffusivity enhances due to the strong viscous dissipation generated by squirmers as well as the interaction of squirmers with the background turbulence. PMID:26628288

  10. Modeling the Thickness of Perennial Ice Covers on Stratified Lakes of the Taylor Valley, Antarctica

    Science.gov (United States)

    Obryk, M. K.; Doran, P. T.; Hicks, J. A.; McKay, C. P.; Priscu, J. C.

    2016-01-01

    A one-dimensional ice cover model was developed to predict and constrain drivers of long term ice thickness trends in chemically stratified lakes of Taylor Valley, Antarctica. The model is driven by surface radiative heat fluxes and heat fluxes from the underlying water column. The model successfully reproduced 16 years (between 1996 and 2012) of ice thickness changes for west lobe of Lake Bonney (average ice thickness = 3.53 m; RMSE = 0.09 m, n = 118) and Lake Fryxell (average ice thickness = 4.22 m; RMSE = 0.21 m, n = 128). Long-term ice thickness trends require coupling with the thermal structure of the water column. The heat stored within the temperature maximum of lakes exceeding a liquid water column depth of 20 m can either impede or facilitate ice thickness change depending on the predominant climatic trend (temperature cooling or warming). As such, shallow (< 20 m deep water columns) perennially ice-covered lakes without deep temperature maxima are more sensitive indicators of climate change. The long-term ice thickness trends are a result of surface energy flux and heat flux from the deep temperature maximum in the water column, the latter of which results from absorbed solar radiation.

  11. Study of volume fractions on biphasic stratified regime using gamma ray

    International Nuclear Information System (INIS)

    Salgado, William L.; Brandão, Luis E.B.

    2017-01-01

    In the oil industries, interconnected pipelines are used to carry large quantities of petroleum and its byproducts. This modal has an advantage because they are more economical, eliminate a need for stocks and, in addition, great safety in operation minimizing a possibility of loss or theft when transported another way. In many cases, especially in the petrochemical industry, the same pipeline is used to carry more than one type of product. They are called poliduct. In the operation of a poliduct there is a sequence of products to be transported and during the exchange of the product, there are still fractions of the previous product and this generates contamination. It is therefore important to identify precisely this region in order to reduce the costs of reprocessing and treatment of discarded products. In this way, this work presents a methodology to evaluate the sensitivity of the gamma densitometry technique in a study of the calculation of volume fractions in biphasic systems, submitted to the stratified flow regime. Using computational simulations using the Monte Carlo Method with the MCNPX code measurement geometry was proposed that presented a higher sensitivity for the calculation of volume fractions. The relevant technical data to perform a simulation of the scintillator detectors were based on information obtained from the gammagraphy technique. The study had a theoretical validation through analytical equations, and the results show that it is possible to identify volume fractions equivalent to 3%. (author)

  12. Turbulent transport across an interface between dry and humid air in a stratified environment

    Science.gov (United States)

    Gallana, Luca; de Santi, Francesca; di Savino, Silvio; Iovieno, Michele; Ricchiardone, Renzo; Tordella, Daniela

    2014-11-01

    The transport of energy and water vapor across a thin layer which separates two decaying isotropic turbulent flows with different kinetic energy and humidity is considered. The interface is placed in a shearless stratified environment in temporal decay. This system reproduces a few aspects of small scale turbulent transport across a dry air/moist air interface in an atmospheric like context. In our incompressible DNS at Reλ = 250 , Boussinesq's approximation is used for momentum and energy transport while the vapor is modeled as a passive scalar (Kumar, Schumacher & Shaw 2014). We investigated different stratification levels with an initial Fr between 0.8 and 8 in presence of a kinetic energy ratio equal to 7. As the buoyancy term becomes of the same order of the inertial ones, a spatial redistribution of kinetic energy, dissipation and vapor concentration is observed. This eventually leads to the onset of a well of kinetic energy in the low energy side of the mixing layer which blocks the entrainment of dry air. Results are discussed and compared with laboratory and numerical experiments. A posteriori estimates of the eventual compression/expansion of fluid particles inside the interfacial mixing layer are given (Nance & Durran 1994).

  13. Using the Internet to Support Exercise and Diet: A Stratified Norwegian Survey.

    Science.gov (United States)

    Wangberg, Silje C; Sørensen, Tove; Andreassen, Hege K

    2015-08-26

    Internet is used for a variety of health related purposes. Use differs and has differential effects on health according to socioeconomic status. We investigated to what extent the Norwegian population use the Internet to support exercise and diet, what kind of services they use, and whether there are social disparities in use. We expected to find differences according to educational attainment. In November 2013 we surveyed a stratified sample of 2196 persons drawn from a Web panel of about 50,000 Norwegians over 15 years of age. The questionnaire included questions about using the Internet, including social network sites (SNS), or mobile apps in relation to exercise or diet, as well as background information about education, body image, and health. The survey email was opened by 1187 respondents (54%). Of these, 89 did not click on the survey hyperlink (declined to participate), while another 70 did not complete the survey. The final sample size is thus 1028 (87% response rate). Compared to the Norwegian census the sample had a slight under-representation of respondents under the age of 30 and with low education. The data was weighted accordingly before analyses. Sixty-nine percent of women and 53% of men had read about exercise or diet on the Internet (χ(2)= 25.6, Psocial disparities in health, and continue to monitor population use. For Internet- and mobile-based interventions to support health behaviors, this study provides information relevant to tailoring of delivery media and components to user.

  14. Dual discharge from a stratified two-phase region through side orifices oriented horizontally

    International Nuclear Information System (INIS)

    Hassan, I.G.; Soliman, H.M.; Sims, G.E.; Kowalski, J.E.

    1995-01-01

    Experimental data are presented for the mass flow rate and quality of two-phase (air-water) discharge from a stratified region through two side orifices (6.35 mm i.d.) with their parallel centre lines located in a horizontal plane. These data correspond to different values of the interface level between the onsets of gas and liquid entrainments for test-section pressures of 316 and 517 kPa, test-section-to-separators pressure difference ranging from 40 to 235 kPa, orifice separating distance to diameter ratio ranging from 1.5 to 8 and different hydraulic resistances of the lines connecting the test section to the separators. Influences of these independent variables on the deviation between the present results (of mass flow rate and quality) and those corresponding to a single discharge are presented and discussed. Normalized plots are presented showing that the present data of dual discharge and those of a single discharge can be collapsed for the whole test range when specific definition for the dimensionless height of the interface and mass flow rate are used. Excellent agreement is demonstrated between single-discharge correlations and the present data using these dimensionless quantities. (author). 12 refs., 1 tab., 16 figs

  15. Situating stigma in stratified reproduction: Abortion stigma and miscarriage stigma as barriers to reproductive healthcare.

    Science.gov (United States)

    Bommaraju, Aalap; Kavanaugh, Megan L; Hou, Melody Y; Bessett, Danielle

    2016-12-01

    To examine whether race and reported history of abortion are associated with abortion stigma and miscarriage stigma, both independently and comparatively. Self-administered surveys with 306 new mothers in Boston and Cincinnati, United States. Abortion stigma perception (ASP); miscarriage stigma perception (MSP); and comparative stigma perception (CSP: abortion stigma perception net of miscarriage stigma perception). Regardless of whether or not they reported having an abortion, white women perceived abortion (ASP) to be more stigmatizing than Black and Latina women. Perceptions of miscarriage stigma (MSP), on the other hand, were dependent on reporting an abortion. Among those who reported an abortion, Black women perceived more stigma from miscarriage than white women, but these responses were flipped for women who did not report abortion. Reporting abortion also influenced our comparative measure (CSP). Among those who did report an abortion, white women perceived more stigma from abortion than miscarriage, while Black and Latina women perceived more stigma from miscarriage than abortion. By measuring abortion stigma in comparison to miscarriage stigma, we can reach a more nuanced understanding of how perceptions of reproductive stigmas are stratified by race and reported reproductive history. Clinicians should be aware that reproductive stigmas do not similarly affect all groups. Stigma from specific reproductive outcomes is more or less salient dependent upon a woman's social position and lived experience. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Fast and Accurate Prediction of Stratified Steel Temperature During Holding Period of Ladle

    Science.gov (United States)

    Deodhar, Anirudh; Singh, Umesh; Shukla, Rishabh; Gautham, B. P.; Singh, Amarendra K.

    2017-04-01

    Thermal stratification of liquid steel in a ladle during the holding period and the teeming operation has a direct bearing on the superheat available at the caster and hence on the caster set points such as casting speed and cooling rates. The changes in the caster set points are typically carried out based on temperature measurements at the end of tundish outlet. Thermal prediction models provide advance knowledge of the influence of process and design parameters on the steel temperature at various stages. Therefore, they can be used in making accurate decisions about the caster set points in real time. However, this requires both fast and accurate thermal prediction models. In this work, we develop a surrogate model for the prediction of thermal stratification using data extracted from a set of computational fluid dynamics (CFD) simulations, pre-determined using design of experiments technique. Regression method is used for training the predictor. The model predicts the stratified temperature profile instantaneously, for a given set of process parameters such as initial steel temperature, refractory heat content, slag thickness, and holding time. More than 96 pct of the predicted values are within an error range of ±5 K (±5 °C), when compared against corresponding CFD results. Considering its accuracy and computational efficiency, the model can be extended for thermal control of casting operations. This work also sets a benchmark for developing similar thermal models for downstream processes such as tundish and caster.

  17. Vorticity generation and evolution in shock-accelerated density-stratified interfaces

    International Nuclear Information System (INIS)

    Yang, X.; Chern, I.; Zabusky, N.J.; Samtaney, R.; Hawley, J.F.

    1992-01-01

    The results of direct numerical simulations of inviscid planar shock-accelerated density-stratified interfaces in two dimensions are presented and compared with shock tube experiments of Haas [(private communication, 1988)] and Sturtevant [in Shock Tubes and Waves, edited by H. Gronig (VCH, Berlin, 1987), p. 89] . Heavy-to-light (''slow/fast or s/f) and light-to-heavy (''fast/slow,'' or f/s) gas interfaces are examined and early-time impulsive vorticity deposition and the evolution of coherent vortex structures are emphasized and quantified. The present second-order Godunov scheme yields excellent agreement with shock-polar analyses at early time. A more physical vortex interpretation explains the commonly used (i.e., linear paradigm) designations of ''unstable'' and ''stable'' for the f/s and s/f interfaces, respectively. The later time events are Rayleigh--Taylor like and can be described in terms of the evolution of a vortex layer (large-scale translation and rotation): asymmetric tip vortex ''roll-up'' and ''binding;'' layer ''instability;'' convective mixing; and baroclinic vorticity generation from secondary shock--interface interactions

  18. Modelling of ground penetrating radar data in stratified media using the reflectivity technique

    International Nuclear Information System (INIS)

    Sena, Armando R; Sen, Mrinal K; Stoffa, Paul L

    2008-01-01

    Horizontally layered media are often encountered in shallow exploration geophysics. Ground penetrating radar (GPR) data in these environments can be modelled by techniques that are more efficient than finite difference (FD) or finite element (FE) schemes because the lateral homogeneity of the media allows us to reduce the dependence on the horizontal spatial variables through Fourier transforms on these coordinates. We adapt and implement the invariant embedding or reflectivity technique used to model elastic waves in layered media to model GPR data. The results obtained with the reflectivity and FDTD modelling techniques are in excellent agreement and the effects of the air–soil interface on the radiation pattern are correctly taken into account by the reflectivity technique. Comparison with real wide-angle GPR data shows that the reflectivity technique can satisfactorily reproduce the real GPR data. These results and the computationally efficient characteristics of the reflectivity technique (compared to FD or FE) demonstrate its usefulness in interpretation and possible model-based inversion schemes of GPR data in stratified media

  19. Regressed relations for forced convection heat transfer in a direct injection stratified charge rotary engine

    Science.gov (United States)

    Lee, Chi M.; Schock, Harold J.

    1988-01-01

    Currently, the heat transfer equation used in the rotary combustion engine (RCE) simulation model is taken from piston engine studies. These relations have been empirically developed by the experimental input coming from piston engines whose geometry differs considerably from that of the RCE. The objective of this work was to derive equations to estimate heat transfer coefficients in the combustion chamber of an RCE. This was accomplished by making detailed temperature and pressure measurements in a direct injection stratified charge (DISC) RCE under a range of conditions. For each specific measurement point, the local gas velocity was assumed equal to the local rotor tip speed. Local physical properties of the fluids were then calculated. Two types of correlation equations were derived and are described in this paper. The first correlation expresses the Nusselt number as a function of the Prandtl number, Reynolds number, and characteristic temperature ratio; the second correlation expresses the forced convection heat transfer coefficient as a function of fluid temperature, pressure and velocity.

  20. Two Rotor Stratified Charge Rotary Engine (SCRE) Engine System Technology Evaluation

    Science.gov (United States)

    Hoffman, T.; Mack, J.; Mount, R.

    1994-01-01

    This report summarizes results of an evaluation of technology enablement component technologies as integrated into a two rotor Stratified Charge Rotary Engine (SCRE). The work constitutes a demonstration of two rotor engine system technology, utilizing upgraded and refined component technologies derived from prior NASA Contracts NAS3-25945, NAS3-24628 and NAS-23056. Technical objectives included definition of, procurement and assembly of an advanced two rotor core aircraft engine, operation with Jet-A fuel at Take-Off rating of 340 BHP (254kW) and operation at a maximum cruise condition of 255 BHP (190kW), 75% cruise. A fuel consumption objective of 0.435 LBS/BHP-Hr (265 GRS/kW-Hr) was identified for the maximum cruise condition. A critical technology component item, a high speed, unit injector fuel injection system with electronic control was defined, procured and tested in conjunction with this effort. The two rotor engine configuration established herein defines an affordable, advanced, Jet-A fuel capability core engine (not including reduction gear, propeller shaft and some aircraft accessories) for General Aviation of the mid-1990's and beyond.

  1. Employment status, inflation and suicidal behaviour: an analysis of a stratified sample in Italy.

    Science.gov (United States)

    Solano, Paola; Pizzorno, Enrico; Gallina, Anna M; Mattei, Chiara; Gabrielli, Filippo; Kayman, Joshua

    2012-09-01

    There is abundant empirical evidence of a surplus risk of suicide among the unemployed, although few studies have investigated the influence of economic downturns on suicidal behaviours in an employment status-stratified sample. We investigated how economic inflation affected suicidal behaviours according to employment status in Italy from 2001 to 2008. Data concerning economically active people were provided by the Italian Institute for Statistical Analysis and by the International Monetary Fund. The association between inflation and completed versus attempted suicide with respect to employment status was investigated in every year and quarter-year of the study time frame. We considered three occupational categories: employed, unemployed who were previously employed and unemployed who had never worked. The unemployed are at higher suicide risk than the employed. Among the PE, a significant association between inflation and suicide attempt was found, whereas no association was reported concerning completed suicides. No association was found between completed and attempted suicides among the employed, the NE and inflation. Completed suicide in females is significantly associated with unemployment in every quarter-year. The reported vulnerability to suicidal behaviours among the PE as inflation rises underlines the need of effective support strategies for both genders in times of economic downturns.

  2. CFD Code Validation against Stratified Air-Water Flow Experimental Data

    Directory of Open Access Journals (Sweden)

    F. Terzuoli

    2008-01-01

    Full Text Available Pressurized thermal shock (PTS modelling has been identified as one of the most important industrial needs related to nuclear reactor safety. A severe PTS scenario limiting the reactor pressure vessel (RPV lifetime is the cold water emergency core cooling (ECC injection into the cold leg during a loss of coolant accident (LOCA. Since it represents a big challenge for numerical simulations, this scenario was selected within the European Platform for Nuclear Reactor Simulations (NURESIM Integrated Project as a reference two-phase problem for computational fluid dynamics (CFDs code validation. This paper presents a CFD analysis of a stratified air-water flow experimental investigation performed at the Institut de Mécanique des Fluides de Toulouse in 1985, which shares some common physical features with the ECC injection in PWR cold leg. Numerical simulations have been carried out with two commercial codes (Fluent and Ansys CFX, and a research code (NEPTUNE CFD. The aim of this work, carried out at the University of Pisa within the NURESIM IP, is to validate the free surface flow model implemented in the codes against experimental data, and to perform code-to-code benchmarking. Obtained results suggest the relevance of three-dimensional effects and stress the importance of a suitable interface drag modelling.

  3. Large Eddy Simulation of Unstably Stratified Turbulent Flow over Urban-Like Building Arrays

    Directory of Open Access Journals (Sweden)

    Bobin Wang

    2013-01-01

    Full Text Available Thermal instability induced by solar radiation is the most common condition of urban atmosphere in daytime. Compared to researches under neutral conditions, only a few numerical works studied the unstable urban boundary layer and the effect of buoyancy force is unclear. In this paper, unstably stratified turbulent boundary layer flow over three-dimensional urban-like building arrays with ground heating is simulated. Large eddy simulation is applied to capture main turbulence structures and the effect of buoyancy force on turbulence can be investigated. Lagrangian dynamic subgrid scale model is used for complex flow together with a wall function, taking into account the large pressure gradient near buildings. The numerical model and method are verified with the results measured in wind tunnel experiment. The simulated results satisfy well with the experiment in mean velocity and temperature, as well as turbulent intensities. Mean flow structure inside canopy layer varies with thermal instability, while no large secondary vortex is observed. Turbulent intensities are enhanced, as buoyancy force contributes to the production of turbulent kinetic energy.

  4. CFD Code Validation against Stratified Air-Water Flow Experimental Data

    International Nuclear Information System (INIS)

    Terzuoli, F.; Galassi, M.C.; Mazzini, D.; D'Auria, F.

    2008-01-01

    Pressurized thermal shock (PTS) modelling has been identified as one of the most important industrial needs related to nuclear reactor safety. A severe PTS scenario limiting the reactor pressure vessel (RPV) lifetime is the cold water emergency core cooling (ECC) injection into the cold leg during a loss of coolant accident (LOCA). Since it represents a big challenge for numerical simulations, this scenario was selected within the European Platform for Nuclear Reactor Simulations (NURESIM) Integrated Project as a reference two-phase problem for computational fluid dynamics (CFDs) code validation. This paper presents a CFD analysis of a stratified air-water flow experimental investigation performed at the Institut de Mecanique des Fluides de Toulouse in 1985, which shares some common physical features with the ECC injection in PWR cold leg. Numerical simulations have been carried out with two commercial codes (Fluent and Ansys CFX), and a research code (NEPTUNE CFD). The aim of this work, carried out at the University of Pisa within the NURESIM IP, is to validate the free surface flow model implemented in the codes against experimental data, and to perform code-to-code benchmarking. Obtained results suggest the relevance of three-dimensional effects and stress the importance of a suitable interface drag modelling

  5. Manganese and iron geochemistry in sediments underlying the redox-stratified Fayetteville Green Lake

    Science.gov (United States)

    Herndon, Elizabeth M.; Havig, Jeff R.; Singer, David M.; McCormick, Michael L.; Kump, Lee R.

    2018-06-01

    Manganese and iron are redox-sensitive elements that yield clues about biogeochemistry and redox conditions both in modern environments and in the geologic past. Here, we investigated Mn and Fe-bearing minerals preserved in basin sediments underlying Fayetteville Green Lake, a redox-stratified lake that serves as a geochemical analogue for Paleoproterozoic oceans. Synchrotron-source microprobe techniques (μXRF, μXANES, and μXRD) and bulk geochemical analyses were used to examine the microscale distribution and speciation of Mn, Fe, and S as a function of depth in the top 48 cm of anoxic lake sediments. Manganese was primarily associated with calcite grains as a manganese-rich carbonate that precipitated in the chemocline of the water column and settled through the euxinic basin to collect in lake sediments. Iron was preserved in framboidal iron sulfides that precipitated in euxinic bottom waters and underwent transformation to pyrite and marcasite in the sediments. Previous studies attribute the formation of manganese-rich carbonates to the diagenetic alteration of manganese oxides deposited in basins underlying oxygenated water. Our study challenges this paradigm by providing evidence that Mn-bearing carbonates form in the water column and accumulate in sediments below anoxic waters. Consequently, manganoan carbonates preserved in the rock record do not necessarily denote the presence of oxygenated bottom waters in ocean basins.

  6. Bioenergetic evaluation of diel vertical migration by bull trout (Salvelinus confluentus) in a thermally stratified reservoir

    Science.gov (United States)

    Eckmann, Madeleine; Dunham, Jason B.; Connor, Edward J.; Welch, Carmen A.

    2018-01-01

    Many species living in deeper lentic ecosystems exhibit daily movements that cycle through the water column, generally referred to as diel vertical migration (DVM). In this study, we applied bioenergetics modelling to evaluate growth as a hypothesis to explain DVM by bull trout (Salvelinus confluentus) in a thermally stratified reservoir (Ross Lake, WA, USA) during the peak of thermal stratification in July and August. Bioenergetics model parameters were derived from observed vertical distributions of temperature, prey and bull trout. Field sampling confirmed that bull trout prey almost exclusively on recently introduced redside shiner (Richardsonius balteatus). Model predictions revealed that deeper (>25 m) DVMs commonly exhibited by bull trout during peak thermal stratification cannot be explained by maximising growth. Survival, another common explanation for DVM, may have influenced bull trout depth use, but observations suggest there may be additional drivers of DVM. We propose these deeper summertime excursions may be partly explained by an alternative hypothesis: the importance of colder water for gametogenesis. In Ross Lake, reliance of bull trout on warm water prey (redside shiner) for consumption and growth poses a potential trade-off with the need for colder water for gametogenesis.

  7. New radiocarbon dates from the Bapot-1 site in Saipan and Neolithic dispersal by stratified diffusion

    International Nuclear Information System (INIS)

    Clark, G.; Petchey, F.; Winter, O.; Carson, M.; O'Day, P.

    2010-01-01

    The colonisation of the Mariana Islands in Western Micronesia is likely to represent an early ocean dispersal of more than 2000 km. Establishing the date of human arrival in the archipelago is important for modelling Neolithic expansion in Island Southeast Asia and the Pacific, particularly the role of long-distance dispersals. This paper presents new 14 C results and a ΔR estimate from the Bapot-1 site on Saipan Island, which indicate human arrival at ca. 3400-3200 cal. BP. Archaeological chronologies of long-distance dispersal to Western Micronesia and the Lapita expansion (Bismarcks to Samoa) show that the Neolithic dispersal rate was increasing during the period ca. 3400-2900 cal. BP. The range-versus-time relationship is similar to stratified diffusion whereby a period of relatively slow expansion is succeeded by long-distance movement. An increase in new colonies created by long-distance migrants results in accelerating range expansion. (author). Refs., 6 figs., 2 tabs.

  8. Using impedance cardiography with postural change to stratify patients with hypertension.

    Science.gov (United States)

    DeMarzo, Arthur P

    2011-06-01

    Early detection of cardiovascular disease in patients with hypertension could initiate appropriate treatment to control blood pressure and prevent the progression of cardiovascular disease. The goal of this study was to show how impedance cardiography waveform analysis with postural change can be used to detect subclinical cardiovascular disease in patients with high blood pressure. Patients with high blood pressure had impedance cardiography data obtained in two positions, standing upright and supine. In 50 adults, impedance cardiography indicated that all patients had abnormal data, with 44 (88%) having multiple abnormalities. Impedance cardiography showed 32 (64%) had ventricular dysfunction, 48 (96%) had vascular load abnormalities, 34 (68%) had hemodynamic abnormalities, 2 (4%) had hypovolemia, and 3 (6%) had hypervolemia. Hypertensive patients have diverse cardiovascular abnormalities that can be quantified by impedance cardiography. By stratifying patients with ventricular, vascular, and hemodynamic abnormalities, treatment could be customized based on the abnormal underlying mechanisms with the potential to rapidly control blood pressure, prevent progression of cardiovascular disease, and possibly reverse remodeling.

  9. Mathematical modeling of two phase stratified flow in a microchannel with curved interface

    Science.gov (United States)

    Dandekar, Rajat; Picardo, Jason R.; Pushpavanam, S.

    2017-11-01

    Stratified or layered two-phase flows are encountered in several applications of microchannels, such as solvent extraction. Assuming steady, unidirectional creeping flow, it is possible to solve the Stokes equations by the method of eigenfunctions, provided the interface is flat and meets the wall with a 90 degree contact angle. However, in reality the contact angle depends on the pair of liquids and the material of the channel, and differs significantly from 90 degrees in many practical cases. For unidirectional flow, this implies that the interface is a circular arc (of constant curvature). We solve this problem within the framework of eigenfunctions, using the procedure developed by Shankar. We consider two distinct cases: (a) the interface meets the wall with the equilibrium contact angle; (b) the interface is pinned by surface treatment of the walls, so that the flow rates determine the apparent contact angle. We show that the contact angle appreciably affects the velocity profile and the volume fractions of the liquids, while limiting the range of flow rates that can be sustained without the interface touching the top/bottom walls. Non-intuitively, we find that the pressure drop is reduced when the more viscous liquid wets the wall.

  10. Characterisation of the suspended particulate matter in a stratified estuarine environment employing complementary techniques

    Science.gov (United States)

    Thomas, Luis P.; Marino, Beatriz M.; Szupiany, Ricardo N.; Gallo, Marcos N.

    2017-09-01

    The ability to predict the sediment and nutrient circulation within estuarine waters is of significant economic and ecological importance. In these complex systems, flocculation is a dynamically active process that is directly affected by the prevalent environmental conditions. Consequently, the floc properties continuously change, which greatly complicates the characterisation of the suspended particle matter (SPM). In the present study, three different techniques are combined in a stratified estuary under quiet weather conditions and with a low river discharge to search for a solution to this problem. The challenge is to obtain the concentration, size and flux of suspended elements through selected cross-sections using the method based on the simultaneous backscatter records of 1200 and 600 kHz ADCPs, isokinetic sampling data and LISST-25X measurements. The two-ADCP method is highly effective for determining the SPM size distributions in a non-intrusive way. The isokinetic sampling and the LISST-25X diffractometer offer point measurements at specific depths, which are especially useful for calibrating the ADCP backscatter intensity as a function of the SPM concentration and size, and providing complementary information on the sites where acoustic records are not available. Limitations and potentials of the techniques applied are discussed.

  11. Zooplankton structure and vertical migration: Using acoustics and biomass to compare stratified and mixed fjord systems

    Science.gov (United States)

    Díaz-Astudillo, Macarena; Cáceres, Mario A.; Landaeta, Mauricio F.

    2017-09-01

    The patterns of abundance, composition, biomass and vertical migration of zooplankton in short-time scales (ADCP device mounted on the hull of a ship were used to obtain vertical profiles of current velocity data and intensity of the backscattered acoustic signal, which was used to study the migratory strategies and to relate the echo intensity with zooplankton biomass. Repeated vertical profiles of temperature, salinity and density were obtained with a CTD instrument to describe the density patterns during both experiments. Zooplankton were sampled every 3 h using a Bongo net to determine abundance, composition and biomass. Migrations were diel in the stratified station, semi-diel in the mixed station, and controlled by light in both locations, with large and significant differences in zooplankton abundance and biomass between day and night samples. No migration pattern associated with the effect of tides was found. The depth of maximum backscatter strength showed differences of approximately 30 m between stations and was deeper in the mixed station. The relation between mean volume backscattering strength (dB) computed from echo intensity and log10 of total dry weight (mg m-3) of zooplankton biomass was moderate but significant in both locations. Biomass estimated from biological samples was higher in the mixed station and determined by euphausiids. Copepods were the most abundant group in both stations. Acoustic methods were a useful technique to understand the detailed patterns of migratory strategies of zooplankton and to help estimate zooplankton biomass and abundance in the inner waters of southern Chile.

  12. Stratified Mucin-Producing Intraepithelial Lesion of the Cervix: Subtle Features Not to Be Missed.

    Science.gov (United States)

    Schwock, Joerg; Ko, Hyang Mi; Dubé, Valérie; Rouzbahman, Marjan; Cesari, Matthew; Ghorab, Zeina; Geddie, William R

    2016-01-01

    Stratified mucin-producing intraepithelial lesion (SMILE) is an uncommon premalignant lesion of the uterine cervix. A detailed examination of preinvasive SMILE cases including a comparison of the cytologic features with usual-type adenocarcinoma in situ (AIS) and human papillomavirus (HPV) genotyping was performed. Excisions and preceding Papanicolaou (Pap) tests were retrieved from the files of 2 tertiary care centers. Histologic review estimated the lesional SMILE proportion. Pap tests were reviewed and assessed for architectural, cellular and background features. Cobas® HPV test was performed. 13 cases were identified. Mean/median patient age was 35/33 years (range 23-51 years). Concurrent high-grade squamous intraepithelial lesion was found in 10/13 (77%) and AIS in 8/13 (62%) cases. In 6 cases, SMILE was dominant (≥50%) and represented in 5/6 corresponding Pap tests. Cytology interpretations differed more often in the SMILE-dominant group (p < 0.05). SMILE and AIS had overlapping features. Feathering and prominent nucleoli were absent in SMILE. HPV DNA was detected in all 12 cases tested. HPV 18 was most common (7/12). Excisions with positive/suspicious margins were reported in 5/6 SMILE-dominant versus 3/7 nondominant cases. SMILE is best considered as an AIS variant for cytologic, etiologic and management purposes. Cytologic features overlap with AIS, but are more subtle and easily missed. HPV testing may play a role in facilitating SMILE detection. © 2016 S. Karger AG, Basel.

  13. Internal wave mode resonant triads in an arbitrarly stratified finite-depth ocean with background rotation

    Science.gov (United States)

    Varma, Dheeraj; Mathur, Manikandan

    2017-11-01

    Internal tides generated by barotropic tides on bottom topography or the spatially compact near-inertial mixed layer currents excited by surface winds can be conveniently represented in the linear regime as a superposition of vertical modes at a given frequency in an arbitrarily stratified ocean of finite depth. Considering modes (m , n) at a frequency ω in the primary wave field, we derive the weakly nonlinear solution, which contains a secondary wave at 2 ω that diverges when it forms a resonant triad with the primary waves. In nonuniform stratifications, resonant triads are shown to occur when the horizontal component of the classical RTI criterion k->1 +k->2 +k->3 = 0 is satisfied along with a non-orthogonality criterion. In nonuniform stratifications with a pycnocline, infinitely more pairs of primary wave modes (m , n) result in RTI when compared to a uniform stratification. Further, two nearby high modes at around the near-inertial frequency often form a resonant triad with a low mode at 2 ω , reminiscent of the features of PSI near the critical latitude. The theoretical framework is then adapted to investigate RTI in two different scenarios: low-mode internal tide scattering over topography, and internal wave beams incident on a pycnocline. The authors thank the Ministry of Earth Sciences, Government of India for financial support under the Monsoon Mission Grant MM/2014/IND-002.

  14. Vulvovaginal-gingival Lichen Planus: Association with Lichen Planopilaris and Stratified Epithelium-specific Antinuclear Antibodies.

    Science.gov (United States)

    Olszewska, Malgorzata; Banka-Wrona, Agnieszka; Skrok, Anna; Rakowska, Adriana; Górska, Renata; Solomon, Lynn W; Rudnicka, Lidia

    2016-01-01

    Vulvovaginal-gingival lichen planus (VVG-LP) consists of a triad of symptoms: vulval, vaginal and gingival lichen planus lesions. The aim of this study was to analyse the prevalence of lesions in various anatomical locations in patients with VVG-LP. The study included 126 consecutive patients with lichen planus. Sixteen (12.7%) patients fulfilled the criteria of VVG-LP. In 12/16 (75%) patients with VVG-LP scalp lesions were also observed. Stratified epithelium-specific antinuclear antibodies (SES-ANA) and anti-ΔNp.3α antibodies were detected in 10/16 (75%) patients with VVG-LP and in 15/110 (13.6%) patients with other forms of lichen planus (p lichen planopilaris. The new entity may be termed "vulvovaginal-gingival-pilar lichen planus" and our study indicates that SES-ANA is a marker of this type of lichen planus with extensive, severe and refractory-to-therapy involvement of the mucous membranes, skin and scalp.

  15. Onset condition of the off take from the stratified region to the branch with arbitrary direction

    International Nuclear Information System (INIS)

    Lee, Jae Young; Choo, Kyo Seong; Kim, Man Woong

    2004-01-01

    Two phase discharge from a stratified region through single or multiple branches has been studied considerably in the past two decades. The flow distribution in the header-feeder system of CANDU(Canada Deuterium and Uranium) reactors during accident scenario is one of good examples of these applications. Recently, the passive safety feature for PWR(Pressurized Water Reactor) introduce the concept of DVI(Direct Vessel Injection) for the emergency core make up. The expected water sweep out phenomena needs careful models including the curvature effect of down comer shell and the multi branches. It has been generally accepted that the onset condition of the off take follows the 2.5 power law, but recently, Lee et al. discussed that the experimental data produced large scattering to the 2.5 power law. Also, the effect of branch angle on the onset point of off take remains still as an unsolved problem. Hwang et al produced the CANDU specific branch angles of 0, +-90, +-36, +-72. The experimental results showed severe deviation from the 2.5 power law and needs mechanistic understanding on these phenomena. In the present paper, we try to develop a general model of onset point including the branch orientation

  16. Characterising the structure of quasi-periodic mixing events in stratified turbulent Taylor-Couette flow

    Science.gov (United States)

    Singh, Kanwar Nain; Partridge, Jamie; Dalziel, Stuart; Caulfield, C. P.; Mathematical Underpinnings of Stratified Turbulence (MUST) Team

    2017-11-01

    We present results from experiments conducted to study mixing in a two-layer stably-stratified turbulent Taylor-Couette flow. It has previously been observed that there is a quasi-periodic mixing event located at the interface separating the layers. We observe, through conductivity probe measurements, that the power of the mixing event in the frequency spectrum of the density data at the interface is higher when measured near the inner cylinder than in the middle of the annular gap. This is consistent with Oglethorpe's (2014) hypothesis that the mixing structure is triggered near the inner cylinder, and then advects and decays or disperses radially. We also observe that at Ri =g/'Ro (RiΩi)2 7 , where Ri, Ro are the inner and outer cylinder radius, respectively, g ' the reduced gravity characterising the density jump between the layers and Ωi is the rotation rate of the inner cylinder, the power drops significantly at all radial locations, which is reminiscent of the onset of the enhanced flux regime as observed by Oglethorpe et al. (2013). We perform experiments to characterise the spatial extent and dynamics of this mixing structure using particle image velocimetry (PIV) giving further insights into this important mixing process. EPSRC programme Grant EP/K034529/1 & SGPC-CCT Scholarship.

  17. Velocity distribution around a sphere descending in a salt-stratified water

    Science.gov (United States)

    Hanazaki, Hideshi; Akiyama, Shinsaku; Okino, Shinya

    2017-11-01

    When a sphere descends at constant speed in a salt-stratified water, a thin and high-speed jet is often generated above the sphere. The phenomenon has first been observed by shadowgraph and then has been investigated numerically. In this study, a systematic measurement by particle image velocimetry (PIV) has been performed for a wide range of Froude number Fr and Reynolds number Re , to actually observe the numerically simulated velocity distributions and confirm the accuracy of the numerical simulations for a very high Schmidt (Prandtl) number of Sc =(Pr =) 700 . The results show that the radius of the jet is proportional to both Fr 1 / 2 and Re - 1 / 2 , meaning that it is proportional to √{ Fr / Re } (when F < 1). The boundary layer on the sphere surface has a thickness comparable to the jet radius, and it is also proportional to √{ Fr / Re }. These results are in agreement with the recent numerical simulations and a simple dimensional analysis. Typical diverging internal-wave patterns, whose vertical wavelength has been predicted to be proportional to Fr , could also be observed.

  18. Succession of Bacterial Communities in a Seasonally Stratified Lake with an Anoxic and Sulfidic Hypolimnion

    Directory of Open Access Journals (Sweden)

    Muhe Diao

    2017-12-01

    Full Text Available Although bacteria play key roles in aquatic food webs and biogeochemical cycles, information on the seasonal succession of bacterial communities in lakes is still far from complete. Here, we report results of an integrative study on the successional trajectories of bacterial communities in a seasonally stratified lake with an anoxic hypolimnion. The bacterial community composition of epilimnion, metalimnion, and hypolimnion diverged during summer stratification and converged when the lake was mixed. In contrast, bacterial communities in the sediment remained relatively stable over the year. Phototrophic Cyanobacteria and heterotrophic Actinobacteria, Alphaproteobacteria and Planktomycetes were abundant in the aerobic epilimnion, Gammaproteobacteria (mainly Chromatiaceae dominated in the metalimnion, and Chlorobi, Betaproteobacteria, Deltaproteobacteria, and Firmicutes were abundant in the anoxic sulfidic hypolimnion. Anoxic but nonsulfidic conditions expanded to the surface layer during fall turnover, when the epilimnion, metalimnion and upper hypolimnion mixed. During this period, phototrophic sulfur bacteria (Chromatiaceae and Chlorobi disappeared, Polynucleobacter (Betaproteobacteria and Methylobacter (Gammaproteobacteria spread out from the former meta- and hypolimnion to the surface layer, and Epsilonproteobacteria dominated in the bottom water layer. Cyanobacteria and Planktomycetes regained dominance in early spring, after the oxygen concentration was restored by winter mixing. In total, these results show large spatio-temporal changes in bacterial community composition, especially during transitions from oxic to anoxic and from sulfidic to nonsulfidic conditions.

  19. Brachytherapy dose-volume histogram computations using optimized stratified sampling methods

    International Nuclear Information System (INIS)

    Karouzakis, K.; Lahanas, M.; Milickovic, N.; Giannouli, S.; Baltas, D.; Zamboglou, N.

    2002-01-01

    A stratified sampling method for the efficient repeated computation of dose-volume histograms (DVHs) in brachytherapy is presented as used for anatomy based brachytherapy optimization methods. The aim of the method is to reduce the number of sampling points required for the calculation of DVHs for the body and the PTV. From the DVHs are derived the quantities such as Conformity Index COIN and COIN integrals. This is achieved by using partial uniform distributed sampling points with a density in each region obtained from a survey of the gradients or the variance of the dose distribution in these regions. The shape of the sampling regions is adapted to the patient anatomy and the shape and size of the implant. For the application of this method a single preprocessing step is necessary which requires only a few seconds. Ten clinical implants were used to study the appropriate number of sampling points, given a required accuracy for quantities such as cumulative DVHs, COIN indices and COIN integrals. We found that DVHs of very large tissue volumes surrounding the PTV, and also COIN distributions, can be obtained using a factor of 5-10 times smaller the number of sampling points in comparison with uniform distributed points

  20. A Powerful Approach to Estimating Annotation-Stratified Genetic Covariance via GWAS Summary Statistics.

    Science.gov (United States)

    Lu, Qiongshi; Li, Boyang; Ou, Derek; Erlendsdottir, Margret; Powles, Ryan L; Jiang, Tony; Hu, Yiming; Chang, David; Jin, Chentian; Dai, Wei; He, Qidu; Liu, Zefeng; Mukherjee, Shubhabrata; Crane, Paul K; Zhao, Hongyu

    2017-12-07

    Despite the success of large-scale genome-wide association studies (GWASs) on complex traits, our understanding of their genetic architecture is far from complete. Jointly modeling multiple traits' genetic profiles has provided insights into the shared genetic basis of many complex traits. However, large-scale inference sets a high bar for both statistical power and biological interpretability. Here we introduce a principled framework to estimate annotation-stratified genetic covariance between traits using GWAS summary statistics. Through theoretical and numerical analyses, we demonstrate that our method provides accurate covariance estimates, thereby enabling researchers to dissect both the shared and distinct genetic architecture across traits to better understand their etiologies. Among 50 complex traits with publicly accessible GWAS summary statistics (N total ≈ 4.5 million), we identified more than 170 pairs with statistically significant genetic covariance. In particular, we found strong genetic covariance between late-onset Alzheimer disease (LOAD) and amyotrophic lateral sclerosis (ALS), two major neurodegenerative diseases, in single-nucleotide polymorphisms (SNPs) with high minor allele frequencies and in SNPs located in the predicted functional genome. Joint analysis of LOAD, ALS, and other traits highlights LOAD's correlation with cognitive traits and hints at an autoimmune component for ALS. Copyright © 2017 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  1. The motions and wave fields produced by an ellipse moving through a stratified fluid

    Science.gov (United States)

    Hurlen, Erik Curtis

    Solid-fluid interactions are ubiquitous in nature, from leaves falling from trees to fish swimming in the ocean. This dissertation examines a certain class of these interactions, namely asymmetric objects moving through stratified fluids. In the first part, the equations of motion are derived and subsequently solved for a displaced neutrally buoyant ellipse of varying aspect ratio. This is accomplished by using a spectral numerical algorithm, although in certain specific cases the equations can also be solved analytically using Laplace transform techniques. Experiments are conducted to which these analytical and numerical results are compared. General quantitative agreement is observed between the two sets of data. The discrepancies which are observed are consistent with both previous research and expectation. In the second part, the focus is shifted from the solid to the fluid, as the primary concern is now the wave field produced by these moving bodies. The spectral method developed in the first part is easily adapted to this second situation, in which the drag forces on the solid are also easily extracted. The results from this section are compared to previous results, and match very well. The results are then expanded to cases which have not been previously studied.

  2. Transport of particles, drops, and small organisms in density stratified fluids

    Science.gov (United States)

    Ardekani, Arezoo M.; Doostmohammadi, Amin; Desai, Nikhil

    2017-10-01

    Sedimenting particles and motile organisms are ubiquitously found in oceans and lakes, where density stratification naturally occurs due to temperature or salinity gradients. We explore the effects of stratification on the fundamental hydrodynamics of settling particles, rising drops, and small organisms. The results of our direct numerical simulations of the sedimentation of particles show that the presence of vertical density gradients in the water column can substantially affect the settling dynamics of a particle, interaction between a pair of particles, and settling rates and microstructure of suspension of particles. We show that elongation of particles affects both the settling orientation and the settling rate of particles in stratified fluids, which will have direct consequences on the vertical flux of particulate matter and carbon flux in the ocean. We further demonstrate an unexpected effect of buoyancy, potentially affecting a broad range of processes at pycnoclines in oceans and lakes. In particular, stratification has a major effect on the flow field, energy expenditure, and nutrient uptake of small organisms. In addition, the role of stratification in pattern formation of bioconvection plumes of algal cells and in biogenic mixing is investigated. In particular, the numerical approach allows for considering the effects of background turbulence and hydrodynamic perturbations produced by swimming organisms, shedding light on the contribution of organisms in the mixing process in aqueous environments.

  3. The BWR Stability Issue

    International Nuclear Information System (INIS)

    D'Auria, F.

    2008-01-01

    The purpose of this paper is to supply general information about Boiling Water Reactor (BWR) stability. The main concerned topics are: phenomenological aspects, experimental database, modelling features and capabilities, numerical models, three-dimensional modelling, BWR system performance during stability, stability monitoring and licensing aspects.

  4. Specialization of mutualistic interaction networks decreases toward tropical latitudes

    DEFF Research Database (Denmark)

    Schleuning, M.; Fründ, J.; Klein, A.-M.

    2012-01-01

    that current conditions have a stronger effect on biotic specialization than historical community stability. Biotic specialization decreased with increasing local and regional plant diversity. This suggests that high specialization of mutualistic interactions is a response of pollinators and seed dispersers......] or differences in plant diversity [10, 11]. Thus, the direction of the latitudinal specialization gradient remains contentious. With an unprecedented global data set, we investigated how biotic specialization between plants and animal pollinators or seed dispersers is associated with latitude, past...... and contemporary climate, and plant diversity. We show that in contrast to expectation, biotic specialization of mutualistic networks is significantly lower at tropical than at temperate latitudes. Specialization was more closely related to contemporary climate than to past climate stability, suggesting...

  5. On the stability of a cold-core eddy in the presence of convection: hydrostatic versus non-hydrostatic modeling

    NARCIS (Netherlands)

    Molemaker, M.J.; Dijkstra, H.A.

    1998-01-01

    Geostrophic eddies in a stratified liquid are susceptable to baroclinic instabilities.In this paper,we consider these instabilities when such an eddy is simultaneously cooled homoge- neously from above.As a linear stability analysis shows,the developing convection modi ?es the background

  6. An extension of theoretical analysis for the onset of slugging criterion in horizontal stratified air-water countercurrent flow

    International Nuclear Information System (INIS)

    Lee, Byung Ryung

    1997-02-01

    This paper presents an experimental and theoretical investigation of interfacial friction factor, wave height and transition criterion from wavy to slug flow in a long horizontal air-water countercurrent stratified flow condition. A series of experiments have been conducted in adiabatic countercurrent stratified flow with the round pipe and rectangular duct test section to develop the interfacial friction factor and the criterion of onset of slugging in horizontal air-water countercurrent stratified flow. An adiabatic semi-empirical correlation for interfacial friction factor has been developed based on the surface roughness concept. A comparison of the measured data in this study and of other investigators with the predictions of the present correlation shows that the agreement is within ±30% error, and that the present correlation is applicable to a broader range of water flow rate than the correlations of previous investigators. The theories which can calculate the wave height and criteria of onset of slug flow in a stratified wavy flow regime have been developed based on the concept of total energy conservation and also wave theory. This theoretical criteria agree better with the measured data than the other criteria available in the literature, but the criteria range about 92∼107% of the measured data. An empirical formula for the criterion has been also developed and compared with the formula in the literatures. Comparison between the measured data and the predictions of the present theory shows that the agreement is within ±8%

  7. International Symposium on Stratified Flows (4th) Held in Grenoble, France on June 29-July 2, 1994. Volume 3

    Science.gov (United States)

    1994-10-10

    support plant and animal life . The ocean is stably stratified, which acts to inhibit vertical mixing. Munk (1966) has show that a basin-averaged...fall int a range specified batwoexi L,., wid Lr.+Ad. For each individual profile which contains uiversions , r𔃽q.2 can be used to obtain the empirical

  8. Two-phase pressurized thermal shock investigations using a 3D two-fluid modeling of stratified flow with condensation

    International Nuclear Information System (INIS)

    Yao, W.; Coste, P.; Bestion, D.; Boucker, M.

    2003-01-01

    In this paper, a local 3D two-fluid model for a turbulent stratified flow with/without condensation, which can be used to predict two-phase pressurized thermal shock, is presented. A modified turbulent K- model is proposed with turbulence production induced by interfacial friction. A model of interfacial friction based on a interfacial sublayer concept and three interfacial heat transfer models, namely, a model based on the small eddies controlled surface renewal concept (HDM, Hughes and Duffey, 1991), a model based on the asymptotic behavior of the Eddy Viscosity (EVM), and a model based on the Interfacial Sublayer concept (ISM) are implemented into a preliminary version of the NEPTUNE code based on the 3D module of the CATHARE code. As a first step to apply the above models to predict the two-phase thermal shock, the models are evaluated by comparison of calculated profiles with several experiments: a turbulent air-water stratified flow without interfacial heat transfer; a turbulent steam-water stratified flow with condensation; turbulence induced by the impact of a water jet in a water pool. The prediction results agree well with the experimental data. In addition, the comparison of three interfacial heat transfer models shows that EVM and ISM gave better prediction results while HDM highly overestimated the interfacial heat transfers compared to the experimental data of a steam water stratified flow

  9. Physiotherapists' views of implementing a stratified treatment approach for patients with low back pain in Germany: a qualitative study

    NARCIS (Netherlands)

    Karstens, S.; Kuithan, P.; Joos, S.; Hill, J.C.; Wensing, M.; Steinhauser, J.; Krug, K.; Szecsenyi, J.

    2018-01-01

    BACKGROUND: The STarT-Back-Approach (STarT: Subgroups for Targeted Treatment) was developed in the UK and has demonstrated clinical and cost effectiveness. Based on the results of a brief questionnaire, patients with low back pain are stratified into three treatment groups. Since the organisation of

  10. Implementing risk-stratified screening for common cancers: a review of potential ethical, legal and social issues.

    Science.gov (United States)

    Hall, A E; Chowdhury, S; Hallowell, N; Pashayan, N; Dent, T; Pharoah, P; Burton, H

    2014-06-01

    The identification of common genetic variants associated with common cancers including breast, prostate and ovarian cancers would allow population stratification by genotype to effectively target screening and treatment. As scientific, clinical and economic evidence mounts there will be increasing pressure for risk-stratified screening programmes to be implemented. This paper reviews some of the main ethical, legal and social issues (ELSI) raised by the introduction of genotyping into risk-stratified screening programmes, in terms of Beauchamp and Childress's four principles of biomedical ethics--respect for autonomy, non-maleficence, beneficence and justice. Two alternative approaches to data collection, storage, communication and consent are used to exemplify the ELSI issues that are likely to be raised. Ultimately, the provision of risk-stratified screening using genotyping raises fundamental questions about respective roles of individuals, healthcare providers and the state in organizing or mandating such programmes, and the principles, which underpin their provision, particularly the requirement for distributive justice. The scope and breadth of these issues suggest that ELSI relating to risk-stratified screening will become increasingly important for policy-makers, healthcare professionals and a wide diversity of stakeholders. © The Author 2013. Published by Oxford University Press on behalf of Faculty of Public Health.

  11. Impressions of the turbulence variability in a weakly stratified, flat-bottom deep-sea ‘boundary layer’

    NARCIS (Netherlands)

    van Haren, H.

    2015-01-01

    The character of turbulent overturns in a weakly stratified deep-sea is investigated in some detail using 144 high-resolution temperature sensors at 0.7 m intervals, starting 5 m above the bottom. A 9-day, 1 Hz sampled record from the 912 m depth flat-bottom (<0.5% bottom-slope) mooring site in the

  12. Feedback stabilization initiative

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-06-01

    Much progress has been made in attaining high confinement regimes in magnetic confinement devices. These operating modes tend to be transient, however, due to the onset of MHD instabilities, and their stabilization is critical for improved performance at steady state. This report describes the Feedback Stabilization Initiative (FSI), a broad-based, multi-institutional effort to develop and implement methods for raising the achievable plasma betas through active MHD feedback stabilization. A key element in this proposed effort is the Feedback Stabilization Experiment (FSX), a medium-sized, national facility that would be specifically dedicated to demonstrating beta improvement in reactor relevant plasmas by using a variety of MHD feedback stabilization schemes.

  13. Feedback stabilization initiative

    International Nuclear Information System (INIS)

    1997-06-01

    Much progress has been made in attaining high confinement regimes in magnetic confinement devices. These operating modes tend to be transient, however, due to the onset of MHD instabilities, and their stabilization is critical for improved performance at steady state. This report describes the Feedback Stabilization Initiative (FSI), a broad-based, multi-institutional effort to develop and implement methods for raising the achievable plasma betas through active MHD feedback stabilization. A key element in this proposed effort is the Feedback Stabilization Experiment (FSX), a medium-sized, national facility that would be specifically dedicated to demonstrating beta improvement in reactor relevant plasmas by using a variety of MHD feedback stabilization schemes

  14. RCRA facility stabilization initiative

    International Nuclear Information System (INIS)

    1995-02-01

    The RCRA Facility Stabilization Initiative was developed as a means of implementing the Corrective Action Program's management goals recommended by the RIS for stabilizing actual or imminent releases from solid waste management units that threaten human health and the environment. The overall goal of stabilization is to, as situations warrant, control or abate threats to human health and/or the environment from releases at RCRA facilities, and/or to prevent or minimize the further spread of contamination while long-term remedies are pursued. The Stabilization initiative is a management philosophy and should not be confused with stabilization technologies

  15. CONSIDERATIONS REGARDING FINANCIAL STABILITY

    Directory of Open Access Journals (Sweden)

    MERCEA PATRICIA AMALIA

    2018-02-01

    target digital coin concepts, use in distributed real-time payment systems of blockchain technologology, artificial intelligence, and information security. However, a large number of economists admit that the current crisis has emphasized the overcoming of the limits of (mainstream economics and its implications in the field of financial regulation and the sphere of monetary policy that should focus not only on price stability, but also on financial stability. In other words, the banks, the financial institutions must be obliged to hold a minimal countercyclical capital and mandatory reserves that should be large enough to cope with the turmoil generated by the decrease of the asset prices and the liquidity risk. In macroprudential policy, the “shadow banking system” (investment banks, hedge funds, private equity funds must also be included.Last but not least, the central banks have to cooperate with the other categories of systemic risk managers: Financial Stability Oversight Council-FSOC (USA, European Systemic Risk Board-ESRB (EU, Financial Policy Committee-FPC (Great Britain, National Committee for Financial Stability-CNSF (Romania.

  16. A stratified two-stage sampling design for digital soil mapping in a Mediterranean basin

    Science.gov (United States)

    Blaschek, Michael; Duttmann, Rainer

    2015-04-01

    The quality of environmental modelling results often depends on reliable soil information. In order to obtain soil data in an efficient manner, several sampling strategies are at hand depending on the level of prior knowledge and the overall objective of the planned survey. This study focuses on the collection of soil samples considering available continuous secondary information in an undulating, 16 km²-sized river catchment near Ussana in southern Sardinia (Italy). A design-based, stratified, two-stage sampling design has been applied aiming at the spatial prediction of soil property values at individual locations. The stratification based on quantiles from density functions of two land-surface parameters - topographic wetness index and potential incoming solar radiation - derived from a digital elevation model. Combined with four main geological units, the applied procedure led to 30 different classes in the given test site. Up to six polygons of each available class were selected randomly excluding those areas smaller than 1ha to avoid incorrect location of the points in the field. Further exclusion rules were applied before polygon selection masking out roads and buildings using a 20m buffer. The selection procedure was repeated ten times and the set of polygons with the best geographical spread were chosen. Finally, exact point locations were selected randomly from inside the chosen polygon features. A second selection based on the same stratification and following the same methodology (selecting one polygon instead of six) was made in order to create an appropriate validation set. Supplementary samples were obtained during a second survey focusing on polygons that have either not been considered during the first phase at all or were not adequately represented with respect to feature size. In total, both field campaigns produced an interpolation set of 156 samples and a validation set of 41 points. The selection of sample point locations has been done using

  17. Experimental Validation of Stratified Flow Phenomena, Graphite Oxidation, and Mitigation Strategies of Air Ingress Accidents

    Energy Technology Data Exchange (ETDEWEB)

    Chang Ho Oh; Eung Soo Kim; Hee Cheon No; Nam Zin Cho

    2008-12-01

    The US Department of Energy is performing research and development (R&D) that focuses on key phenomena that are important during challenging scenarios that may occur in the Next Generation Nuclear Plant (NGNP) Program / GEN-IV Very High Temperature Reactor (VHTR). Phenomena identification and ranking studies (PIRT) to date have identified the air ingress event, following on the heels of a VHTR depressurization, as very important (Schultz et al., 2006). Consequently, the development of advanced air ingress-related models and verification and validation (V&V) are very high priority for the NGNP program. Following a loss of coolant and system depressurization, air will enter the core through the break. Air ingress leads to oxidation of the in-core graphite structure and fuel. The oxidation will accelerate heat-up of the bottom reflector and the reactor core and will cause the release of fission products eventually. The potential collapse of the bottom reflector because of burn-off and the release of CO lead to serious safety problems. For estimation of the proper safety margin we need experimental data and tools, including accurate multi-dimensional thermal-hydraulic and reactor physics models, a burn-off model, and a fracture model. We also need to develop effective strategies to mitigate the effects of oxidation. The results from this research will provide crucial inputs to the INL NGNP/VHTR Methods R&D project. This project is focused on (a) analytical and experimental study of air ingress caused by density-driven, stratified, countercurrent flow, (b) advanced graphite oxidation experiments, (c) experimental study of burn-off in the bottom reflector, (d) structural tests of the burnt-off bottom reflector, (e) implementation of advanced models developed during the previous tasks into the GAMMA code, (f) full air ingress and oxidation mitigation analyses, (g) development of core neutronic models, (h) coupling of the core neutronic and thermal hydraulic models, and (i

  18. Binder materials for the cathodes applied to self-stratifying membraneless microbial fuel cell.

    Science.gov (United States)

    Walter, Xavier Alexis; Greenman, John; Ieropoulos, Ioannis

    2018-04-19

    The recently developed self-stratifying membraneless microbial fuel cell (SSM-MFC) has been shown as a promising concept for urine treatment. The first prototypes employed cathodes made of activated carbon (AC) and polytetrafluoroethylene (PTFE) mixture. Here, we explored the possibility to substitute PTFE with either polyvinyl-alcohol (PVA) or PlastiDip (CPD; i.e. synthetic rubber) as binder for AC-based cathode in SSM-MFC. Sintered activated carbon (SAC) was also tested due to its ease of manufacturing and the fact that no stainless steel collector is needed. Results indicate that the SSM-MFC having PTFE cathodes were the most powerful measuring 1617 μW (11 W·m -3 or 101 mW·m -2 ). SSM-MFC with PVA and CPD as binders were producing on average the same level of power (1226 ± 90 μW), which was 24% less than the SSM-MFC having PTFE-based cathodes. When balancing the power by the cost and environmental impact, results clearly show that PVA was the best alternative. Power wise, the SAC cathodes were shown being the less performing (≈1070 μW). Nonetheless, the lower power of SAC was balanced by its inexpensiveness. Overall results indicate that (i) PTFE is yet the best binder to employ, and (ii) SAC and PVA-based cathodes are promising alternatives that would benefit from further improvements. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  19. AN INVESTIGATION OF TIME LAG MAPS USING THREE-DIMENSIONAL SIMULATIONS OF HIGHLY STRATIFIED HEATING

    Energy Technology Data Exchange (ETDEWEB)

    Winebarger, Amy R. [NASA Marshall Space Flight Center, ZP 13, Huntsville, AL 35812 (United States); Lionello, Roberto; Downs, Cooper; Mikić, Zoran; Linker, Jon [Predictive Science, Inc., 9990 Mesa Rim Rd., Ste. 170, San Diego, CA 92121-2910 (United States); Mok, Yung, E-mail: amy.r.winebarger@nasa.gov, E-mail: lionel@predsci.com, E-mail: cdowns@predsci.com, E-mail: mikicz@predsci.com, E-mail: linkerj@predsci.com, E-mail: ymok@uci.edu [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)

    2016-11-10

    The location and frequency of coronal energy release provide a significant constraint on the coronal heating mechanism. The evolution of the intensity observed in coronal structures found from time lag analysis of Atmospheric Imaging Assembly (AIA) data has been used to argue that heating must occur sporadically. Recently, we have demonstrated that quasi-steady, highly stratified (footpoint) heating can produce results qualitatively consistent with the evolution of observed coronal structures. The goals of this paper are to demonstrate that time lag analysis of 3D simulations of footpoint heating are qualitatively consistent with time lag analysis of observations and to use the 3D simulations to further understand whether time lag analysis is a useful tool in defining the evolution of coronal structures. We find the time lag maps generated from simulated data are consistent with the observed time lag maps. We next investigate several example points. In some cases, the calculated time lag reflects the evolution of a unique loop along the line of sight, though there may be additional evolving structures along the line of sight. We confirm that using the multi-peak AIA channels can produce time lags that are difficult to interpret. We suggest using a different high temperature channel, such as an X-ray channel. Finally, we find that multiple evolving structures along the line of sight can produce time lags that do not represent the physical properties of any structure along the line of sight, although the cross-correlation coefficient of the lightcurves is high. Considering the projected geometry of the loops may reduce some of the line-of-sight confusion.

  20. Distinct Clinicopathological Patterns of Mismatch Repair Status in Colorectal Cancer Stratified by KRAS Mutations.

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    Wenbin Li

    Full Text Available In sporadic colorectal cancer (CRC, the BRAFV600E mutation is associated with deficient mismatch repair (MMR status and inversely associated with to KRAS mutations. In contrast to deficient MMR (dMMR CRC, data on the presence of KRAS oncogenic mutations in proficient MMR (pMMR CRC and their relationship with tumor progression are scarce. We therefore examined the MMR status in combination with KRAS mutations in 913 Chinese patients and correlated the findings obtained with clinical and pathological features. The MMR status was determined based on detection of MLH1, MSH2, MSH6 and PMS2 expression. KRAS mutation and dMMR status were detected in 36.9% and 7.5% of cases, respectively. Four subtypes were determined by MMR and KRAS mutation status: KRAS (+/pMMR (34.0%, KRAS (+/dMMR (2.9%, KRAS (-/pMMR (58.5% and KRAS (-/dMMR (4.6%. A higher percentage of pMMR tumors with KRAS mutation were most likely to be female (49.0%, proximal located (45.5%, a mucinous histology (38.4%, and to have increased lymph node metastasis (60.3%, compared with pMMR tumors without BRAFV600E and KRAS mutations (36.0%, 29.3%, 29.4% and 50.7%, respectively; all P < 0.01. To the contrary, compared with those with KRAS(-/dMMR tumors, patients with KRAS(+/dMMR tumors demonstrated no statistically significant differences in gender, tumor location, pT depth of invasion, lymph node metastasis, pTNM stage, and histologic grade. This study revealed that specific epidemiologic and clinicopathologic characteristics are associated with MMR status stratified by KRAS mutation. Knowledge of MMR and KRAS mutation status may enhance molecular pathologic staging of CRC patients and metastatic progression in CRC can be estimated based on the combination of these biomarkers.