Buoyant densities of phototrophic sulfur bacteria and cyanobacteria
Guerrero, R.
1985-01-01
The buoyant densities of bacterial cells are greatly influenced by the accumulation of intracellular reserve material. The buoyant density of phototrophic bacteria that are planktonic is of particular interest, since these organisms must remain in the photic zone of the water column for optimal growth. Separation of cells by their buoyant density may also be of use in separating and identifying organisms from a natural population. The bacteria used were obtained from pure cultures, enrichments, or samples taken directly from the environment.
Density Driven Removal of Sediment from a Buoyant Muddy Plume
Rouhnia, M.; Strom, K.
2014-12-01
Experiments were conducted to study the effect of settling driven instabilities on sediment removal from hypopycnal plumes. Traditional approaches scale removal rates with particle settling velocity however, it has been suggested that the removal from buoyant suspensions happens at higher rates. The enhancement of removal is likely due to gravitational instabilities, such as fingering, at two-fluid interface. Previous studies have all sought to suppress flocculation, and no simple model exists to predict the removal rates under the effect of such instabilities. This study examines whether or not flocculation hampers instability formation and presents a simple removal rate model accounting for gravitational instabilities. A buoyant suspension of flocculated Kaolinite overlying a base of clear saltwater was investigated in a laboratory tank. Concentration was continuously measured in both layers with a pair of OBS sensors, and interface was monitored with digital cameras. Snapshots from the video were used to measure finger velocity. Samples of flocculated particles at the interface were extracted to retrieve floc size data using a floc camera. Flocculation did not stop creation of settling-driven fingers. A simple cylinder-based force balance model was capable of predicting finger velocity. Analogy of fingering process of fine grained suspensions to thermal plume formation and the concept of Grashof number enabled us to model finger spacing as a function of initial concentration. Finally, from geometry, the effective cross-sectional area was correlated to finger spacing. Reformulating the outward flux expression was done by substitution of finger velocity, rather than particle settling velocity, and finger area instead of total area. A box model along with the proposed outward flux was used to predict the SSC in buoyant layer. The model quantifies removal flux based on the initial SSC and is in good agreement with the experimental data.
A change in a single gene of Salmonella typhimurium can dramatically change its buoyant density.
Baldwin, W W; Kirkish, M A; Koch, A L
1994-01-01
The growth rates and buoyant densities of a Salmonella typhimurium mutant, TL126 (proB74A+), with enhanced osmotolerance caused by proline overproduction were measured and compared with the growth rates and buoyant densities of an isogenic (wild-type) strain, TL128 (proB+ A+), with normal control of proline production. Growth rates were determined in a rich medium (Luria broth) with added NaCl to produce various osmotic strengths ranging from 300 to 2,000 mosM. At low concentrations of NaCl, ...
Evidence for osmoregulation of cell growth and buoyant density in Escherichia coli.
Baldwin, W W; Kubitschek, H. E.
1984-01-01
The buoyant density of cells of Escherichia coli B/r NC32 increased with the osmolarity of the growth medium. Growth rate and its variability were also dependent upon the osmolarity of the medium. Maximum growth rates and minimum variability of these rates were obtained in Luria broth by addition of NaCl to a concentration of about 0.23 M.
Energy Technology Data Exchange (ETDEWEB)
El-Amin, M.F.; Kanayama, H. [Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)
2009-02-15
In this paper, the integral method is used to derive a complete set of results and expressions for selected physical turbulent properties of a non-buoyant jet or momentum-dominated buoyant jet regime of small-scale hydrogen leakage. Several quantities of interest, including the cross-stream velocity, Reynolds stress, velocity-concentration correlation (radial flux), dominant turbulent kinetic energy production term, turbulent eddy viscosity and turbulent eddy diffusivity are obtained. In addition, the turbulent Schmidt number is estimated and the normalized jet-feed material density and the normalized momentum flux density are correlated. Throughout this paper, experimental results from Schefer et al. [Schefer RW, Houf WG, Williams TC. Investigation of small-scale unintended releases of hydrogen: momentum-dominated regime. Int J Hydrogen Energy 2008;33(21):6373-84] and other works for the momentum-dominated jet resulting from small-scale hydrogen leakage are used in the integral method. For a non-buoyant jet or momentum-dominated regime of a buoyant jet, both the centerline velocity and centerline concentration are proportional with z{sup -1}. The effects of buoyancy-generated momentum are assumed to be small, and the Reynolds number is sufficient for fully developed turbulent flow. The hydrogen-air momentum-dominated regime or non-buoyant jet is compared with the air-air jet as an example of non-buoyant jets. Good agreement was found between the current results and experimental results from the literature. In addition, the turbulent Schmidt number was shown to depend solely on the ratio of the momentum spread rate to the material spread rate. (author)
Protoplast water content of bacterial spores determined by buoyant density sedimentation.
Lindsay, J A; Beaman, T C; Gerhardt, P
1985-01-01
Protoplast wet densities (1.315 to 1.400 g/ml), determined by buoyant density sedimentation in Metrizamide gradients, were correlated inversely with the protoplast water contents (26.4 to 55.0 g of water/100 g of wet protoplast) of nine diverse types of pure lysozyme-sensitive dormant bacterial spores. The correlation equation provided a precise method for obtaining the protoplast water contents of other spore types with small impure samples and indicated that the average protoplast dry densi...
Theoretical analysis and semianalytical solutions for a turbulent buoyant hydrogen-air jet
El-Amin, M.F.
2012-01-01
Semianalytical solutions are developed for turbulent hydrogen-air plume. We derived analytical expressions for plume centerline variables (radius, velocity, and density deficit) in terms of a single universal function, called plume function. By combining the obtained analytical expressions of centerline variables with empirical Gaussian expressions of the mean variables, we obtain semianalytical expressions for mean quantities of hydrogen-air plume (velocity, density deficit, and mass fraction).
Theoretical Analysis and Semianalytical Solutions for a Turbulent Buoyant Hydrogen-Air Jet
El-Amin, M. F.; Shuyu Sun; Amgad Salama
2012-01-01
Semianalytical solutions are developed for turbulent hydrogen-air plume. We derived analytical expressions for plume centerline variables (radius, velocity, and density deficit) in terms of a single universal function, called plume function. By combining the obtained analytical expressions of centerline variables with empirical Gaussian expressions of the mean variables, we obtain semianalytical expressions for mean quantities of hydrogen-air plume (velocity, density deficit, and mass fraction).
Unsteady turbulent buoyant plumes
Woodhouse, Mark J; Hogg, Andrew J
2015-01-01
We model the unsteady evolution of turbulent buoyant plumes following temporal changes to the source conditions. The integral model is derived from radial integration of the governing equations expressing the conservation of mass, axial momentum and buoyancy. The non-uniform radial profiles of the axial velocity and density deficit in the plume are explicitly described by shape factors in the integral equations; the commonly-assumed top-hat profiles lead to shape factors equal to unity. The resultant model is hyperbolic when the momentum shape factor, determined from the radial profile of the mean axial velocity, differs from unity. The solutions of the model when source conditions are maintained at constant values retain the form of the well-established steady plume solutions. We demonstrate that the inclusion of a momentum shape factor that differs from unity leads to a well-posed integral model. Therefore, our model does not exhibit the mathematical pathologies that appear in previously proposed unsteady i...
Harvey, R.W.; Metge, D.W.; Kinner, N.; Mayberry, N.
1997-01-01
Buoyant densities were determined for groundwater bacteria and microflagellates (protozoa) from a sandy aquifer (Cape Cod, MA) using two methods: (1) density-gradient centrifugation (DGC) and (2) Stoke's law approximations using sedimentation rates observed during natural-gradient injection and recovery tests. The dwarf (average cell size, 0.3 ??m), unattached bacteria inhabiting a pristine zone just beneath the water table and a majority (~80%) of the morphologically diverse community of free- living bacteria inhabiting a 5-km-long plume of organically-contaminated groundwater had DGC-determined buoyant densities <1.019 g/cm3 before culturing. In the aquifer, sinking rates for the uncultured 2-??m size class of contaminant plume bacteria were comparable to that of the bromide tracer (1.9 x 10-3 M), also suggesting a low buoyant density. Culturing groundwater bacteria resulted in larger (0.8-1.3 ??m), less neutrally- buoyant (1.043-1.081 g/cm3) cells with potential sedimentation rates up to 64-fold higher than those predicted for the uncultured populations. Although sedimentation generally could be neglected in predicting subsurface transport for the community of free-living groundwater bacteria, it appeared to be important for the cultured isolates, at least until they readapt to aquifer conditions. Culturing-induced alterations in size of the contaminant-plume microflagellates (2-3 ??m) were ameliorated by using a lower nutrient, acidic (pH 5) porous growth medium. Buoyant densities of the cultured microflagellates were low, i.e., 1.024-1.034 g/cm3 (using the DGC assay) and 1.017-1.039 g/cm3 (estimated from in-situ sedimentation rates), suggesting good potential for subsurface transport under favorable conditions.
Evidence that platelet buoyant density, but not size, correlates with platelet age in man
International Nuclear Information System (INIS)
Following infusion of 51Cr-labeled autologous platelets into normal subjects, high-density (HD) and low-density (LD) platelet cohorts were isolated by prolonged centrifugation in isosmotic arabino-galactan (Stractan). Specific radio-activity of LD platelets declined rapidly post-infusion (T1/2 . 1.5 days), but specific radioactivity of HD platelets remained constant or increased over a 3--4-day period and gradually declined for 6--7 days thereafter. These differences were exaggerated when platelet cohorts enriched in LD or HD cells by slow centrifugation in high-density albumin were labeled and transfused. Mean survival of a platelet cohort enriched with HD cells was significantly (P less than 0.02) shorter (7.73 days) than that of a cohort enriched with LD cells (9.33) days). In normal subjects treated with aspirin, capacity for thromboxane synthesis was regained more rapidly (P less than 0.05) in LD than in HD platelets. HD and LD platelets differed only slightly in mean volume (HD platelets . 7.57 mu3, LD platelets . 6.87 mu3, 0.05 less than P less than 0.01). We believe the most logical interpretation of these findings is that under normal conditions in man, newly formed platelets are less dense on the average than total platelets and become more dense as they age in the circulation. Thus, specific radioactivity of LD platelets declines rapidly as these platelets move into a more dense compartment and are replaced by newly formed, unlabelled cells; specific radioactivity of HD platelets remains constant or increases as labelled platelets enter this compartment in numbers equal to or greater than the number leaving it at the end of their life span. The similarity in mean volumes of LD and HD platelets suggests that platelet size is unrelated to platelet age under normal conditions
Buoyant Norbury's vortex rings
Blyth, Mark; Rodriguez-Rodriguez, Javier; Salman, Hayder
2014-11-01
Norbury's vortices are a one-parameter family of axisymmetric vortex rings that are exact solutions to the Euler equations. Due to their relative simplicity, they are extensively used to model the behavior of real vortex rings found in experiments and in Nature. In this work, we extend the original formulation of the problem to include buoyancy effects for the case where the fluid that lies within the vortex has a different density to that of the ambient. In this modified formulation, buoyancy effects enter the problem through the baroclinic term of the vorticity equation. This permits an efficient numerical solution of the governing equation of motion in terms of a vortex contour method that tracks the evolution of the boundary of the vortex. Finally, we compare our numerical results with the theoretical analysis of the short-time evolution of a buoyant vortex. Funded by the Spanish Ministry of Economy and Competitiveness through grant DPI2011-28356-C03-02 and by the London Mathematical Society.
Non-Boussinesq turbulent buoyant jet of a low-density gas leaks into high-density ambient
El-Amin, Mohamed
2010-12-01
In this article, we study the problem of low-density gas jet injected into high-density ambient numerically which is important in applications such as fuel injection and leaks. It is assumed that the local rate of entrainment is consisted of two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. The integral models of the mass, momentum and concentration fluxes are obtained and transformed to a set of ordinary differential equations using some similarity transformations. The resulting system is solved to determine the centerline quantities which are used to get the mean axial velocity, mean concentration and mean density of the jet. Therefore, the centerline and mean quantities are used together with the governing equation to determine some important turbulent quantities such as, cross-stream velocity, Reynolds stress, velocity- concentration correlation, turbulent eddy viscosity and turbulent eddy diffusivity. Throughout this paper the developed model is verified by comparing the present results with experimental results and jet/plume theory from the literature. © 2010 Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Pivovarov, M.A.; Zhang, H.; Ramakev, D.E.; Tatem, P.A.; Williams, F.W. (George Washington Univ., Washington, DC (United States). Dept. of Chemistry)
1993-02-01
This paper considers the applicability of different versions of the k-[epsilon] hypothesis of turbulence for flame modeling. Utilizing similarity solutions, the authors find that the k-[epsilon] hypothesis gives a finite radius for a weak axisymmetric plume above the heat source. The radius of this plume is defined as an eigenvalue of the boundary value problem with unknown boundary. Solving this problem with an adjusted set of parameters from the standard version of the k-[epsilon] hypothesis gives excellent agreement with experimental data for center line and radial profiles of the mean and turbulent quantities, and also for the radius of the plume and entrainment level. In contrast, the standard set of parameters, widely utilized in flame modeling, gives inaccurate predictions. Specifically, this set of parameters yields underestimates of the radius of the plume and the entrainment level. Since this same trend has been extensively observed in flame modeling, the authors conclude that the standard set of parameters for the k-[epsilon] hypothesis is inadequate, and that this is the main reason for the shortcomings of previous numerical models.
International Nuclear Information System (INIS)
The analysis on a density stratification layer consisting of multiple gases in the reactor containment vessel is important for the safety assessment of sever accidents. The Japan Atomic Energy Agency (JAEA) has started the project on the containment thermal hydraulics. We carried out Computational Fluid Dynamics (CFD) analyses in order to investigate the erosion of the density stratification layer by a vertical buoyant jet under this project. We used the Reynolds averaged numerical simulation (RANS) and Large eddy simulation (LES) models to analyze the erosion of a density stratification layer by a vertical buoyant jet in a small vessel which represents a containment vessel. This numerical study calculates the turbulent mixing of a two-component (air and helium) gas mixture. The turbulence models used for the RANS analyses are two types of k-ε models. The first model is the low Reynolds number k-ε model developed by Launder and Sharma. The second model is revised from the first model in order to accurately consider the turbulent production and damping in a stratification layer. The results have indicated that both the RANS and LES models simulate almost the same behavior of the erosion of the density stratification layer. While the erosion rate calculated by the low-Re k-ε model was faster than that of the LES model, the modified k-ε model could calculate the erosion rate similar to the LES result. (author)
Vasel-Be-Hagh, Ahmadreza; Carriveau, Rupp; Ting, David S-K; Turner, John Stewart
2015-10-01
Extending from the model proposed by Vasel-Be-Hagh et al. [J. Fluid Mech. 769, 522 (2015)], a perturbation analysis is performed to modify Turner's radius by taking into account the viscous effect. The modified radius includes two terms; the zeroth-order solution representing the effect of buoyancy, and the first-order perturbation correction describing the influence of viscosity. The zeroth-order solution is explicit Turner's radius; the first-order perturbation modification, however, includes the drag coefficient, which is unknown and of interest. Fitting the photographically measured radius into the modified equation yields the time history of the drag coefficient of the corresponding buoyant vortex ring. To give further clarification, the proposed model is applied to calculate the drag coefficient of a buoyant vortex ring at a Bond number of approximately 85; a similar procedure can be applied at other Bond numbers. PMID:26565349
Vasel-Be-Hagh, Ahmadreza; Carriveau, Rupp; Ting, David S.-K.; Turner, John Stewart
2015-10-01
Extending from the model proposed by Vasel-Be-Hagh et al. [J. Fluid Mech. 769, 522 (2015), 10.1017/jfm.2015.126], a perturbation analysis is performed to modify Turner's radius by taking into account the viscous effect. The modified radius includes two terms; the zeroth-order solution representing the effect of buoyancy, and the first-order perturbation correction describing the influence of viscosity. The zeroth-order solution is explicit Turner's radius; the first-order perturbation modification, however, includes the drag coefficient, which is unknown and of interest. Fitting the photographically measured radius into the modified equation yields the time history of the drag coefficient of the corresponding buoyant vortex ring. To give further clarification, the proposed model is applied to calculate the drag coefficient of a buoyant vortex ring at a Bond number of approximately 85; a similar procedure can be applied at other Bond numbers.
Turbulent Buoyant Jets in Flowing Ambients
DEFF Research Database (Denmark)
Chen, Hai-Bo; Larsen, Torben; Petersen, Ole
1991-01-01
The mean behaviour of horizontal turbulent buoyant jets in co-flowing currents is investigated experimentally and numerically, in terms of jet trajectory, dilution and centerline density deficit and velocity decay. It is demonstrated in the paper that the laboratory data on the jet trajectory...... of turbulent buoyant jet in the presence of arnbient current and provide a ready tool for the purpose of sea outfall design....
Turbulent buoyant jets and plumes
Rodi, Wolfgang
The Science & Applications of Heat and Mass Transfer: Reports, Reviews, & Computer Programs, Volume 6: Turbulent Buoyant Jets and Plumes focuses on the formation, properties, characteristics, and reactions of turbulent jets and plumes. The selection first offers information on the mechanics of turbulent buoyant jets and plumes and turbulent buoyant jets in shallow fluid layers. Discussions focus on submerged buoyant jets into shallow fluid, horizontal surface or interface jets into shallow layers, fundamental considerations, and turbulent buoyant jets (forced plumes). The manuscript then exami
NUMERICAL PREDICTION OF LINE BUOYANT JETS IN CROSS FLOWS
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The k-ε turbulence model was used to establish the mathematicalmodel of two-dimensional line buoyant jets in crossflow. The hybrid finite analytic method and staggered grid were applied to the calculation of line buoyant jets. Only receiving water with uniform density is considered. The distribution of velocity, temperature and turbulent kinetic energy were analyzed, and the variation of the maximum velocity was given. The effect of velocity ratio and densimetric Froude number on line buoyant jets was considered.
Energy Technology Data Exchange (ETDEWEB)
Abe, Satoshi, E-mail: abe.satoshi@jaea.go.jp; Ishigaki, Masahiro; Sibamoto, Yasuteru; Yonomoto, Taisuke
2015-08-15
Highlights: . • The third international benchmark exercise (IBE-3) focused on density stratification erosion by a vertical buoyant jet in the reactor containment vessel. • Two types turbulence model modification were applied in order to accurately simulate the turbulence helium transportation in the density stratification. • The analysis result in case with turbulence model modification is good agreement with the experimental data. • There is a major difference of turbulence helium–mass transportation between in case with and without the turbulence model modification. - Abstract: Density stratification in the reactor containment vessel is an important phenomenon on an issue of hydrogen safety. The Japan Atomic Energy Agency (JAEA) has started the ROSA-SA project on containment thermal hydraulics. As a part of the activity, we participated in the third international CFD benchmark exercise (IBE-3) focused on density stratification erosion by a vertical buoyant jet in containment vessel. This paper shows our approach for the IBE-3, focusing on the turbulence transport phenomena in eroding the density stratification and introducing modified turbulence models for improvement of the CFD analyses. For this analysis, we modified the CFD code OpenFOAM by using two turbulence models; the Kato and Launder modification to estimate turbulent kinetic energy production around a stagnation point, and the Katsuki model to consider turbulence damping in density stratification. As a result, the modified code predicted well the experimental data. The importance of turbulence transport modeling is also discussed using the calculation results.
International Nuclear Information System (INIS)
Highlights: . • The third international benchmark exercise (IBE-3) focused on density stratification erosion by a vertical buoyant jet in the reactor containment vessel. • Two types turbulence model modification were applied in order to accurately simulate the turbulence helium transportation in the density stratification. • The analysis result in case with turbulence model modification is good agreement with the experimental data. • There is a major difference of turbulence helium–mass transportation between in case with and without the turbulence model modification. - Abstract: Density stratification in the reactor containment vessel is an important phenomenon on an issue of hydrogen safety. The Japan Atomic Energy Agency (JAEA) has started the ROSA-SA project on containment thermal hydraulics. As a part of the activity, we participated in the third international CFD benchmark exercise (IBE-3) focused on density stratification erosion by a vertical buoyant jet in containment vessel. This paper shows our approach for the IBE-3, focusing on the turbulence transport phenomena in eroding the density stratification and introducing modified turbulence models for improvement of the CFD analyses. For this analysis, we modified the CFD code OpenFOAM by using two turbulence models; the Kato and Launder modification to estimate turbulent kinetic energy production around a stagnation point, and the Katsuki model to consider turbulence damping in density stratification. As a result, the modified code predicted well the experimental data. The importance of turbulence transport modeling is also discussed using the calculation results
Density of aqueous solutions of CO2
Energy Technology Data Exchange (ETDEWEB)
Garcia, Julio E.
2001-10-10
In this report, we present a numerical representation for the partial molar volume of CO2 in water and the calculation of the corresponding aqueous solution density. The motivation behind this work is related to the importance of having accurate representations for aqueous phase properties in the numerical simulation of carbon dioxide disposal into aquifers as well as in geothermal applications. According to reported experimental data the density of aqueous solutions of CO2 can be as much as 2-3% higher than pure water density. This density variation might produce an influence on the groundwater flow regime. For instance, in geologic sequestration of CO2, convective transport mixing might occur when, several years after injection of carbon dioxide has stopped, the CO2-rich gas phase is concentrated at the top of the formation, just below an overlaying caprock. In this particular case the heavier CO2 saturated water will flow downward and will be replaced by water with a lesser CO2 content.
Analytical Solution for Stellar Density in Globular Clusters
Indian Academy of Sciences (India)
M. A. Sharaf; A. M. Sendi
2011-09-01
In this paper, four parameters analytical solution will be established for the stellar density function in globular clusters. The solution could be used for any arbitrary order of outward decrease of the cluster’s density.
Negatively buoyant starting jets
Marugán-Cruz, C.; Rodríguez-Rodríguez, Javier; Martínez-Bazán, C.
2009-01-01
The initial development of negatively buoyant jets has been investigated experimentally and numerically, focusing on the role played by gravity in the evolution of the leading vortex ring. Under the experimental conditions considered in this work, the densimetric Froude number, Fr= ρjU²j/[(ρ₀ − ρj) gD] , which represents the ratio between the jet momentum and the buoyancy forces, emerges as the most relevant parameter characterizing the dynamics of the flow. Two different flow regimes h...
Dynamics of buoyant bubbles in clusters of galaxies
Pavlovski, Georgi; Pope, Edward C D
2007-01-01
We present a phenomenological model of the dynamics of buoyant bubbles in the atmosphere of a cluster of galaxies. The derived equations describe velocity, size, mass, temperature and density of the buoyant bubbles as functions of time based on several simple approximations. The constructed model is then used to interpret results of a numerical experiment of heating of the cluster core with buoyant bubbles in a hydrodynamical approximation (i.e. in the absence of magnetic fields, viscosity, and thermal diffusion). Based on the model parameters we discuss possible limitations of the numerical treatment of the problem, and highlight the main physical processes that govern the dynamics of bubbles in the intracluster medium.
Viscosity and density tables of sodium chloride solutions
Energy Technology Data Exchange (ETDEWEB)
Fair, J.A.; Ozbek, H. (comps.)
1977-04-01
A file is presented containing tabulated data extracted from the scientific literature on the density and viscosity of aqueous sodium chloride solutions. Also included is a bibliography of the properties of aqueous sodium chloride solutions. (MHR)
Turbulence Statistics of a Buoyant Jet in a Stratified Environment
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
Static solutions in general relativity with infinite central density
Flammer, Philip David
2016-01-01
This paper presents full general relativistic simulations of uniformly rotating polytropes. A logarithm is taken of the radial coordinate, which enables the study of more static solutions than previously possible. In particular, static solutions out to the limit of infinite central energy density are found for a range of adiabatic exponents. The analytic behavior for large central energy density near the origin is determined by solving Einstein's equations in spherical symmetry assuming the pressure is proportional to the energy; this agrees well with the numerical results. The allowed space of static solutions, which extends from zero central energy density to infinity, is bounded at low adiabatic exponents as gravity loses its ability to bind the matter (the radius and mass go to infinity). The stability of the solution space is studied in the case of spherical symmetry. In addition to the usual region of stability bounded by low central energy densities, we find two other separate possible regions of stabi...
Energy Technology Data Exchange (ETDEWEB)
Bomfimsilva, Carlos; Jorge, Joao Paulo Carrijo; Schmid, Dominique; Gomes, Rodrigo Klim [INTECSEA, Sao Paulo, SP (Brazil); Lima, Alexander Piraja [GDK, Salvador, BA (Brazil)
2009-12-19
Worldwide shipments of plastic pipes are forecasted to increase 5.2% per year since 2008, being commonly used for water supply and sewage disposal. The HDPE (High Density Polyethylene) pipes have been applied recently to deliver potable water and fire fighting water for the main pier of the LNG system in Guanabara Bay, Rio de Janeiro. The system contains three sizes of pipe outside diameter, 110 mm and 160 mm for water supply, and 500 mm for the fire fighting system. The main design challenges of the pipeline system included providing on-bottom stability, a suitable installation procedure and a proper riser design. The on-bottom stability calculations, which are quite different from the conventional steel pipelines, were developed by designing concrete blocks to be assembled on the pipeline in a required spacing to assure long term stability, knowing that plastic pipes are buoyant even in flooded conditions. The installation procedure was developed considering the lay down methodology based on surface towing technique. The riser was designed to be installed together with additional steel support structure to allow the entire underwater system to have the same plastic pipe specification up to the surface. This paper presents the main challenges that were faced during the design of the HDPE pipelines for the LNG system in Guanabara Bay, addressing the solutions and recommendations adopted for the plastic underwater pipeline system.
A solution density model for hanford waste treatment plant supernatants
International Nuclear Information System (INIS)
The density of nuclear waste solution is used as a process control parameter in the Hanford Waste Treatment Plant pretreatment process and is crucial to tank utilization evaluations. The supernatants, however, have many different dissolved sodium salts, including nitrate, nitrite, carbonate, sulfate, phosphate, hydroxide, and aluminate. The large concentrations and diversity of salts in the waste has made the predictions of solution densities difficult historically. The purpose of this study is to determine if a new model of multi-component electrolyte solution densities, recently published in the literature, is effective at predicting the density of nuclear waste supernatants. A statistically designed set of solution densities containing the most prevalent electrolytes in Hanford tank waste was used for model validation. The densities of the simulants were calculated by the model and compared to the experimentally determined densities. The average model error was just 0.1%. These results indicate that the model can be used to accurately predict the density of nuclear waste processed at the Hanford Waste Treatment Plant. (authors)
Mixing by turbulent buoyant jets in slender containers
Energy Technology Data Exchange (ETDEWEB)
Voropayev, S.I., E-mail: s.voropayev@nd.edu [Environmental Fluid Dynamics Laboratories, Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, 117851 (Russian Federation); Nath, C.; Fernando, H.J.S. [Environmental Fluid Dynamics Laboratories, Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States)
2012-10-01
A turbulent buoyant jet injected vertically into a slender cylinder containing a stratified fluid is investigated experimentally. The working fluid is water, and salt is used to change its density to obtain either a positively or negatively buoyant jet. The interest is the vertical density distribution in container and its dependence on time and other parameters. For each case (lighter or heavier jet) the experimental data could be collapsed into a ‘universal’ time dependent behavior, when properly non-dimensionalized. A theoretical model is advanced to explain the results. Possible applications include refilling of crude oil into U.S. strategic petroleum reserves caverns. -- Highlights: ► We addresses a critical issue on refill of Strategic Petroleum Reserves. ► We conduct experiments on negatively/positively buoyant turbulent jets in long cavern. ► Basing on results of experiments we developed theoretical model for refill operations.
Laboratory Study of Dispersion of Buoyant Surface Plumes
DEFF Research Database (Denmark)
Petersen, Ole; Larsen, Torben
1990-01-01
A laboratory a study on surface dispersion of buoyant plumes in open channel turbulence in made, where the buoyancy is due to both salinity and heat. The measured parameters are the downstream derivative of a plume width and height, which are integral-characteristics of the distributions of density......-differences. Other methods as infra-red sensing are used for visualizing purpose. The results are used to calibrate an integral model of the dispersion. Conclusions are that the dispersion of a buoyant surface plume can be treated the superposition of a buoyancy induced stretching and turbulent diffusion, reduced in...
Densities concentrations of aqueous of uranyl nitrate solutions
International Nuclear Information System (INIS)
The ratio density-concentration of aqueous uranyl nitrate solutions expressed as U3O8 grams/liter, U grams/liter and hexahydrate uranyl nitrate weight percent at different temperatures, are established. Experimental values are graphically correlated and compared whit some published data. (Author) 2 refs
EFFECTIVE POROSITY IMPLIES EFFECTIVE BULK DENSITY IN SORBING SOLUTE TRANSPORT
Energy Technology Data Exchange (ETDEWEB)
Flach, G.
2012-02-27
The concept of an effective porosity is widely used in solute transport modeling to account for the presence of a fraction of the medium that effectively does not influence solute migration, apart from taking up space. This non-participating volume or ineffective porosity plays the same role as the gas phase in single-phase liquid unsaturated transport: it increases pore velocity, which is useful towards reproducing observed solute travel times. The prevalent use of the effective porosity concept is reflected by its prominent inclusion in popular texts, e.g., de Marsily (1986), Fetter (1988, 1993) and Zheng and Bennett (2002). The purpose of this commentary is to point out that proper application of the concept for sorbing solutes requires more than simply reducing porosity while leaving other material properties unchanged. More specifically, effective porosity implies the corresponding need for an effective bulk density in a conventional single-porosity model. The reason is that the designated non-participating volume is composed of both solid and fluid phases, both of which must be neglected for consistency. Said another way, if solute does not enter the ineffective porosity then it also cannot contact the adjoining solid. Conceptually neglecting the fluid portion of the non-participating volume leads to a lower (effective) porosity. Likewise, discarding the solid portion of the non-participating volume inherently leads to a lower or effective bulk density. In the author's experience, practitioners virtually never adjust bulk density when adopting the effective porosity approach.
Buoyant Nanoparticles: Implications for Nano-Biointeractions in Cellular Studies.
Watson, C Y; DeLoid, G M; Pal, A; Demokritou, P
2016-06-01
In the safety and efficacy assessment of novel nanomaterials, the role of nanoparticle (NP) kinetics in in vitro studies is often ignored although it has significant implications in dosimetry, hazard ranking, and nanomedicine efficacy. It is demonstrated here that certain nanoparticles are buoyant due to low effective densities of their formed agglomerates in culture media, which alters particle transport and deposition, dose-response relationships, and underestimates toxicity and bioactivity. To investigate this phenomenon, this study determines the size distribution, effective density, and assesses fate and transport for a test buoyant NP (polypropylene). To enable accurate dose-response assessment, an inverted 96-well cell culture platform is developed in which adherent cells are incubated above the buoyant particle suspension. The effect of buoyancy is assessed by comparing dose-toxicity responses in human macrophages after 24 h incubation in conventional and inverted culture systems. In the conventional culture system, no adverse effects are observed at any NP concentration tested (up to 250 μg mL(-1) ), whereas dose-dependent decreases in viability and increases in reactive oxygen species are observed in the inverted system. This work sheds light on an unknown issue that plays a significant role in vitro hazard screening and proposes a standardized methodology for buoyant NP assessments. PMID:27135209
Buoyant currents arrested by convective dissolution
MacMinn, Christopher W.; Juanes, Ruben
2013-05-01
When carbon dioxide (CO2) dissolves into water, the density of water increases. This seemingly insubstantial phenomenon has profound implications for geologic carbon sequestration. Here we show, by means of laboratory experiments with analog fluids, that the up-slope migration of a buoyant current of CO2 is arrested by the convective dissolution that ensues from a fingering instability at the moving CO2-groundwater interface. We consider the effectiveness of convective dissolution as a large-scale trapping mechanism in sloping aquifers, and we show that a small amount of slope is beneficial compared to the horizontal case. We study the development and coarsening of the fingering instability along the migrating current and predict the maximum migration distance of the current with a simple sharp-interface model. We show that convective dissolution exerts a powerful control on CO2 plume dynamics and, as a result, on the potential of geologic carbon sequestration.
Anharmonic densities of states: A general dynamics-based solution
Jellinek, Julius; Aleinikava, Darya
2016-06-01
Density of states is a fundamental physical characteristic that lies at the foundation of statistical mechanics and theoretical constructs that derive from them (e.g., kinetic rate theories, phase diagrams, and others). Even though most real physical systems are anharmonic, the vibrational density of states is customarily treated within the harmonic approximation, or with some partial, often limited, account for anharmonicity. The reason for this is that the problem of anharmonic densities of states stubbornly resisted a general and exact, yet convenient and straightforward in applications, solution. Here we formulate such a solution within both classical and quantum mechanics. It is based on actual dynamical behavior of systems as a function of energy and as observed, or monitored, on a chosen time scale, short or long. As a consequence, the resulting anharmonic densities of states are fully dynamically informed and, in general, time-dependent. As such, they lay the ground for formulation of new statistical mechanical frameworks that incorporate time and are ergodic, by construction, with respect to actual dynamical behavior of systems.
Fast Density Inversion Solution for Full Tensor Gravity Gradiometry Data
Hou, Zhenlong; Wei, Xiaohui; Huang, Danian
2016-02-01
We modify the classical preconditioned conjugate gradient method for full tensor gravity gradiometry data. The resulting parallelized algorithm is implemented on a cluster to achieve rapid density inversions for various scenarios, overcoming the problems of computation time and memory requirements caused by too many iterations. The proposed approach is mainly based on parallel programming using the Message Passing Interface, supplemented by Open Multi-Processing. Our implementation is efficient and scalable, enabling its use with large-scale data. We consider two synthetic models and real survey data from Vinton Dome, US, and demonstrate that our solutions are reliable and feasible.
Solvent density mode instability in non-polar solutions
Indian Academy of Sciences (India)
Susmita Kar; Ranjit Biswas; J Chakrabarti
2008-08-01
We analyse the origin of the multiple long time scales associated with the long time decay observed in non-polar solvation dynamics by linear stability analysis of solvent density modes where the effects of compressibility and solvent structure are systematically incorporated. The coupling of the solute–solvent interactions at both ground and excited states of the solute with the compressibility and solvent structure is found to have important effects on the time scales. The present theory suggests that the relatively longer time constant is controlled by the solvent compressibility, while the solvent structure at the nearest-neighbour length scale dominates the shorter time constant.
International Nuclear Information System (INIS)
In order to calculate criticality parameters of nuclear fuel solution systems, number density of nuclides are needed and they are generally estimated from density equations. Most of the relations allowing the calculation of the density of aqueous solutions containing the electrolytes HNO3-UO2(NO3)2-Pu(NO3)4, usually called 'nitrate dilution laws' are strictly empirical. They are obtained from a fit of assumed polynomial expressions on experimental density data. Out of their interpolation range, such mathematical expressions show discrepancies between calculated and experimental data appearing in the high concentrations range. In this study, a physico-chemical approach based on the isopiestic mixtures rule is suggested. The behaviour followed by these mixtures was first observed in 1936 by Zdanovskii and expressed as: 'Binary solutions (i.e. one electrolyte in water) having a same water activity are mixed without variation of this water activity value'. With regards to this behaviour, a set of basic thermodynamic expressions has been pointed out by Ryazanov and Vdovenko in 1965 concerning enthalpy, entropy, volume of mixtures, activity and osmotic coefficient of the components. In particular, a very simple relation for the density is obtained from the volume mixture expression depending on only two physico-chemical variables: i) concentration of each component in the mixture and in their respectively binary solutions having the same water activity as the mixture and ii), density of each component respectively in the binary solution having the same water activity as the mixture. Therefore, the calculation needs the knowledge of binary data (water activity, density and concentration) of each component at the same temperature as the mixture. Such experimental data are largely published in the literature and are available for nitric acid and uranyl nitrate. Nevertheless, nitric acid binary data show large discrepancies between the authors and need to be revised. In the
An Experimental Investigation on Inclined Negatively Buoyant Jets
Bashitialshaaer, Raed; Larson, Magnus; Persson, Kenneth M.
2012-01-01
An experimental study was performed to investigate the behavior of inclined negatively buoyant jets. Such jets arise when brine is discharged from desalination plants. A turbulent jet with a specific salinity was discharged through a circular nozzle at an angle to the horizontal into a tank with fresh water and the spatial evolution of the jet was recorded. Four different initial jet parameters were changed, namely the nozzle diameter, the initial jet inclination, the jet density and the flow...
Hydrodynamic modeling of towed buoyant submarine antenna's in multidirectional seas.
Geiger, Sam R.
2000-01-01
A finite difference computer model is developed to simulate the exposure statistics of a radio frequency buoyant antenna as it is towed in a three-dimensional random seaway. The model allows the user to prescribe antenna properties (length, diameter, density, etc.), sea conditions (significant wave height, development of sea), tow angle, and tow speed. The model then simulates the antenna-sea interaction for the desired duration to collect statistics relating to antenna performance. The model...
Compressibility effects in some buoyant flows
Energy Technology Data Exchange (ETDEWEB)
Gauthier, S; Lafay, M-A; Lombard, V; Boudesocque-Dubois, C; Clarisse, J-M; Le Creurer, B [CEA, DIF, F-91297 Arpajon Cedex (France)], E-mail: Serge.Gauthier@cea.fr
2008-12-15
Compressibility effects in buoyant flows are studied on three examples: the classical Rayleigh-Taylor instability (RTI) for compressible miscible flows, the ablation front instability and the thermal convection of Rayleigh-Benard. The linear analysis of the classical RTI for viscous flows is performed and the opposite effects of stratification and compressibility on the growth rate are pointed out. Some investigations in the nonlinear regime have also been carried out and show that the trend observed in the linear regime usually holds. On the other hand, a 2D simulation, started from rest and pursued until the return toward mechanical equilibrium of the mixing exhibits a typical compressibility effect, an acoustic wave, damped by the physical viscosity. The ablation front instability is detailed on the 'laser imprint' problem of direct drive irradiation. The linear stability analysis is performed on an unsteady mean flow given by the self-similar solutions of gas dynamics equations with nonlinear heat conduction. Compressibility effects are studied through the Kovasznay modes. It appears that maximum amplitudes are achieved for zero wave number, and complex wave-like structures are observed. Analogy with the large-scale instability, which occurs in compressible thermal convection, is suggested. These results have been obtained with an autoadaptive dynamical multidomain Chebyshev method.
Modified density equation for aqueous solution with plutonium(IV) and nitric acid
International Nuclear Information System (INIS)
In order to calculate criticality parameters for solution systems, the number densities of nuclides are needed and usually calculated by use of density equations. For the system of aqueous solution with Pu(IV) and nitric acid, Maimoni's equation based on Hofstetters' density data was often used, but its reliability was not thoroughly examined. The author, therefore, derived a modified density equation by regression analysis for Hofstetters' data, adding the authors' density data of aqueous solution with nitric acid. Comparison between both equations showed that the modified density equation gives more reliable densities in the wide range of temperature and concentration. (author)
Wind influence on a coastal buoyant outflow
Whitney, Michael M.; Garvine, Richard W.
2005-03-01
This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (∣Ws∣ 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.
Classification and prediction of buoyant surface discharges
International Nuclear Information System (INIS)
This paper reports on effluents that are often discharged into riverine, estuarine, and costal waters at or near the surface of the receiving water body. Although government regulations generally limit or prohibit surface discharges containing industrial or municipal pollutants, several exceptions exist, such as the discharge of heated water from power plants, and the discharge of effluent from combined sewer overflows. Past efforts to predict the dilution and geometric characteristics of buoyant surface flows have relied on integral modelling techniques involving the solution of a series of differential equations. Although these models have proven successful in predicting simple surface flows, they are extremely limited in applicability due to their inability to account for boundary interaction, strong buoyancy, and recirculating. The proposed method is a two step process involving: classification of the flow depending on the most significant discharge and ambient characteristics, and quantitative prediction of flow through use of simple analytical expressions applied to limited regions within the flow. Classification of the flow is used to distinguish between the great variety of flow patterns that exist under widely differing ambient and discharge conditions. Mathematical prediction of dilution and geometric parameters of the flow (width, depth and centerline trajectory) requires the use of length scales to delineate subregions within the flow. Analytical expressions based on perturbation solutions of the governing equations are applied to each subregion. Although the proposed methodology could be done in any of several frameworks, the authors have chose that of a computer expert system which provides a practical engineering tool for both design and regulatory use
Dilution of Buoyant Surface Plumes
DEFF Research Database (Denmark)
Larsen, Torben; Petersen, Ole
The purpose of present work is to establish a quantitative description of a surface plume which is valid for the range of density differences occurring in relation to sewage outfalls.......The purpose of present work is to establish a quantitative description of a surface plume which is valid for the range of density differences occurring in relation to sewage outfalls....
Duer, W. C.; And Others
1977-01-01
Discusses comparisons of packing densities derived from known molar volume data of liquids and solutions. Suggests further studies for using assemblies of spheres as models for simple liquids and solutions. (MLH)
Singh Aurora, Tarlok
2013-04-01
In introductory physics, students verify Archimedes' principle by immersing an object in water in a container, with a side-spout to collect the displaced water, resulting in a large uncertainty, due to surface tension. A modified procedure was introduced, in which a plastic bucket is suspended from a force sensor, and an object hangs underneath the bucket. The object is immersed in water in a glass beaker (without any side spout), and the weight loss is measured with a computer-controlled force sensor. Instead of collecting the water displaced by the object, tap water was added to the bucket to compensate for the weight loss, and the Archimedes' principle was verified within less than a percent. With this apparatus, buoyant force was easily studied as a function of volume of displaced water; as well as a function of density of saline solution. By graphing buoyant force as a function of volume (or density of liquid), value of g was obtained from slope. Apparatus and sources of error will be discussed.
Experimental investigations in turbulent buoyant jets of sodium
International Nuclear Information System (INIS)
Axisymmetric, turbulent buoyant jets are investigated in the sodium test section TEFLU. The character of the flow is divided into three regimes depending on the densimetric Froude number: the pure jet, the buoyant jet in the transition regime and the pure plume. By means of a temperature compensated Miniature Permanentmagnet Flowmeter Probe the mean velocity, mean temperature and intensity of temperature fluctuations are measured simultaneously at axial distances between 3 and 40 initial jet diameters from the orifice. The functional principle of the Miniature Permanentmagnet Flowmeter Probe which allows velocity measurements to be made in the presence of a temperature gradient is described in detail. For all three regimes both the decay laws of the quantities measured along the axis of the containment pipe and the radial profiles are indicated and discussed. With the help of the radial profiles of the mean quantities the axial development of the half-width radii and the axial development of the momentum, buoyancy and volume fluxes are calculated. In addition, the time history of the temperature fluctuations is recorded at several radial positions. The data are analysed according to characteristic values of statistical signal analysis such as minimum value, maximum value, skewness, flatness and according to characteristic functions such as probability density function, autopower spectrum density and autocorrelation function. The experimental results for the axisymmetric, turbulent buoyant jets of sodium are compared with experimental results from the literature and with fluids of molecular Prandtl numbers greater than or equal to 0.7. The basic differences betwen the experimental results obtained for water and for sodium are outlined. Statements are formulated which allow thermo- and fluiddynamic diffusion processes to be transferred from water to sodium. (orig.)
Ions in solution: Density Corrected Density Functional Theory (DC-DFT)
Kim, Min-Cheol; Burke, Kieron
2014-01-01
Standard density functional approximations often give questionable results for odd-electron radical complexes, with the error typically attributed to self-interaction. In density corrected density functional theory (DC-DFT), certain classes of density functional theory calculations are significantly improved by using densities more accurate than the self-consistent densities. We discuss how to identify such cases, and how DC-DFT applies more generally. To illustrate, we calculate potential energy surfaces of HO$\\cdot$Cl$^-$ and HO$\\cdot$H$_2$O complexes using various common approximate functionals, with and without this density correction. Commonly used approximations yield wrongly shaped surfaces and/or incorrect minima when calculated self consistently, while yielding almost identical shapes and minima when density corrected. This improvement is retained even in the presence of implicit solvent.
Infrared Sensing of Buoyant Surface Plumes
DEFF Research Database (Denmark)
Petersen, Ole; Larsen, Torben
1988-01-01
This paper is concerned with laboratory experiments on buoyant surface plumes where heat is the source of buoyancy. Temperature distributions were measured at the water surface using infra-red sensing, and inside the waterbody a computer based measurement system was applied. The plume is described...
46 CFR 160.010-3 - Inflatable buoyant apparatus.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Inflatable buoyant apparatus. 160.010-3 Section 160.010-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Buoyant Apparatus for Merchant Vessels § 160.010-3 Inflatable buoyant apparatus. (a)...
46 CFR 160.010-6 - Capacity of buoyant apparatus.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Capacity of buoyant apparatus. 160.010-6 Section 160.010-6 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Buoyant Apparatus for Merchant Vessels § 160.010-6 Capacity of buoyant apparatus. (a)...
Spatial DNS of flow transition of a rectangular buoyant reacting free-jet*
Jiang, X.; Luo, K. H.
2001-10-01
This paper describes a spatial direct numerical simulation (DNS) of the flow transition of a buoyant diffusion flame established on a rectangular nozzle with an aspect ratio of 2:1. Combustion is represented by a one-step finite-rate Arrhenius chemistry. Without applying external perturbations, large vortical structures develop naturally in the flow field due to buoyancy effects. The vortex dynamics of the rectangular buoyant reacting jet has been analysed. The interaction between density gradients and gravity initiates the flow vorticity in the cross-streamwise directions. The streamwise vorticity is mainly generated by the vortex stretching. Downstream of the reacting jet, a more disorganized flow regime characterized by small scales has been observed, following the breakdown of the large vortical structures due to three-dimensional vortex interactions. Analysis of the energy spectra shows that the spatially developing reacting jet has a tendency of transition to turbulence under the effects of combustion-induced buoyancy. Buoyancy effects are found to be very important to the formation, development, interaction and breakdown of vortices. In contrast with the relaminarization effects of chemical exothermicity on non-buoyant jet diffusion flames via volumetric expansion and viscous damping, the tendency towards transition to turbulence in buoyant reacting jets is greatly enhanced by the overwhelming buoyancy effects. Calculations of the mean flow property show that the rectangular buoyant reacting jet has a higher entrainment rate than its non-reacting counterpart.
Simulated Annealing of Two Electron Density Solution Systems
Neto, Mario de Oliveira; Alonso, Ronaldo Luiz; Leite, Fabio Lima; Jr, Osvaldo N. Oliveira; Polikarpov, Igor; Mascarenhas, Yvonne Primerano
2008-01-01
Many structural studies have been performed with a combination of SAXS and simulated annealing to reconstruct three dimensional models. Simulated annealing is suitable for the study of monodisperse, diluted and two-electron densities systems. In this chapter we showed how the simulated annealing procedure can be used to minimize the discrepancy between two functions: the simulated intensity and the experimental one-dimensional SAXS curve. The goal was to find the most probable form for a prot...
Settling of almost neutrally buoyant particles in homogeneous isotropic turbulence
van Hinsberg, Michel; Clercx, Herman; Toschi, Federico
2015-11-01
Settling of particles in a turbulent flow occurs in various industrial and natural phenomena, examples are clouds and waste water treatment. It is well known that turbulence can enhance the settling velocity of particles. Many studies have been done, numerically and experimentally to investigate this behavior for the case of ``heavy'' particles, with particle to fluid density ratios above 100. Here we investigate the case of almost neutrally buoyant particles, i.e. density ratios between 1 and 100. In the case of light particles the Maxey-Riley equations cannot be simplified to only the Stokes drag and gravity force as pressure gradient, added mass and Basset history force are important as well. We investigate the influence of these forces on the settling velocity of particles and show that the extra forces can both increase or decrease the settling velocity, depending on the combination of the Stokes number and gravity applied.
Investigations of a turbulent buoyant sodium jet
International Nuclear Information System (INIS)
The paper describes an experimental investigation of a turbulent buoyant sodium jet which was discharging into a slowly moving ambient. Measurements of mean velocity, mean temperature and temperature fluctuations were made using a miniature permanent magnet flowmeter probe for a range of conditions encompassing forced convection jets, buoyant jets and plumes. The geometrical arrangement departed from that for a classical free jet in that the jet emerged into a confined co-flow but the essential characteristics of free jet behaviour were observed. The decay of axial velocity was broadly the same as for fluid of higher Prandtl number. The decay of mean temperature differences and temperature fluctuations were different from that for fluids of higher Prandtl number due to the importance of molecular diffusion in heat transport. (author)
ROUNDED FLOWING STATES OF OBSTRUCTED BUOYANT JET
Institute of Scientific and Technical Information of China (English)
HUAI Wen-xin; FANG Shen-guang
2006-01-01
The mutual relationships of three effective factors, the diameter D/d (d is the diameter of exit) of obstructed plate, exit densimetric Froude number and the distance H/d of the plate from jet orifice for obstructed buoyant jet in static ambient, are analyzed to explain normal and abnormal rounded flowing (reverberated and bifurcated flowing).The critical Froude numbers for obstructed buoyant jets with H/d=2, 4, 6, 8 which distinguished normal and abnormal flowing pattern are obtained. Normal rounded flowing is found only for a plate under a special value of H/d. A fitted formula of critical Froude numbers with H/d and D/d is presented to distinguish rounded flowing types. The occurring of reverberated or bifurcated flowing in abnormal rounded flow is analyzed. Based on the results of obstructed buoyant jets with D/d=1, normal rounded flowing occurred only for all conditions and axial dilution behind the plate under different H/D is obtained.
Ruxu Lian; Lan Huang; Jian Liu
2012-01-01
We consider the exterior problem and the initial boundary value problem for the spherically symmetric isentropic compressible Navier-Stokes equations with density-dependent viscosity coefficient in this paper. For regular initial density, we show that there exists a unique global strong solution to the exterior problem or the initial boundary value problem, respectively. In particular, the strong solution tends to the equilibrium state as $t\\to +\\infty $ .
Institute of Scientific and Technical Information of China (English)
LI Zhi-Bing; WANG Wei-Liang
2006-01-01
We derive the analytic solution of induced electrostatic potential along single wall carbon nanotubes. Under the hypothesis of constant density of states in the charge-neutral level, we are able to obtain the linear density of excess charge in an external Geld parallel to the tube axis.
Li, Zhibing; Wang, Weiliang
2006-01-01
We derived the analytic solution of induced electrostatic potential along single wall carbon nanotubes. Under the hypothesis of constant density of states in the charge-neutral level, we are able to obtain the linear density of excess charge in an external field parallel to the tube axis.
46 CFR 108.697 - Buoyant work vests.
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Buoyant work vests. 108.697 Section 108.697 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Miscellaneous Equipment § 108.697 Buoyant work vests. (a) Each buoyant work vest on a unit must be approved under Subpart 160.053 or...
Analytical solutions of the problem of violent explosions in a plasma of varying density
International Nuclear Information System (INIS)
Analytical solutions of the non-linear problem of violent explosions in a plasma of varying density under power law have been obtained. A critical law for a medium of decreasing density from the source of explosion is determined for which the problem admits a very simple solution but beyond this critical line analytical solutions admit another discontinuity automatically occuring inside a blast wave region. It is assumed that a disturbance caused by violent explosion due to sudden release of immense amount of energy is expanding very rapidly and is headed by a strong MHD shock wave. It is found that the discontinuity appearing inside a blast wave region causes a violation of continuum theory in the physical plane and consequently a cavity is formed. Analytical solutions predict that just before a discontinuity appears, the gas pressure falls to zero and the solution breaks down and can not be extended further. (Auth.)
Probing Ionic Liquid Aqueous Solutions Using Temperature of Maximum Density Isotope Effects
Directory of Open Access Journals (Sweden)
Mohammad Tariq
2013-03-01
Full Text Available This work is a new development of an extensive research program that is investigating for the first time shifts in the temperature of maximum density (TMD of aqueous solutions caused by ionic liquid solutes. In the present case we have compared the shifts caused by three ionic liquid solutes with a common cation—1-ethyl-3-methylimidazolium coupled with acetate, ethylsulfate and tetracyanoborate anions—in normal and deuterated water solutions. The observed differences are discussed in terms of the nature of the corresponding anion-water interactions.
International Nuclear Information System (INIS)
A general method was developed for estimating the volumetric energy efficiency of pressure retarded osmosis via pressure-volume analysis of a membrane process. The resulting model requires only the osmotic pressure, π, and mass fraction, w, of water in the concentrated and dilute feed solutions to estimate the maximum achievable specific energy density, uu, as a function of operating pressure. The model is independent of any membrane or module properties. This method utilizes equilibrium analysis to specify the volumetric mixing fraction of concentrated and dilute solution as a function of operating pressure, and provides results for the total volumetric energy density of similar order to more complex models for the mixing of seawater and riverwater. Within the framework of this analysis, the total volumetric energy density is maximized, for an idealized case, when the operating pressure is π(1+√w-1), which is lower than the maximum power density operating pressure, Δπ/2, derived elsewhere, and is a function of the solute osmotic pressure at a given mass fraction. It was also found that a minimum 1.45 kmol of ideal solute is required to produce 1 kWh of energy while a system operating at "maximum power density operating pressure" requires at least 2.9 kmol. Utilizing this methodology, it is possible to examine the effects of volumetric solution cost, operation of a module at various pressure, and operation of a constant pressure module with various feed.
Energy Technology Data Exchange (ETDEWEB)
Reimund, Kevin K. [Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemical and Biomolecular Engineering; McCutcheon, Jeffrey R. [Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemical and Biomolecular Engineering; Wilson, Aaron D. [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-08-01
A general method was developed for estimating the volumetric energy efficiency of pressure retarded osmosis via pressure-volume analysis of a membrane process. The resulting model requires only the osmotic pressure, π, and mass fraction, w, of water in the concentrated and dilute feed solutions to estimate the maximum achievable specific energy density, uu, as a function of operating pressure. The model is independent of any membrane or module properties. This method utilizes equilibrium analysis to specify the volumetric mixing fraction of concentrated and dilute solution as a function of operating pressure, and provides results for the total volumetric energy density of similar order to more complex models for the mixing of seawater and riverwater. Within the framework of this analysis, the total volumetric energy density is maximized, for an idealized case, when the operating pressure is π/(1+√w⁻¹), which is lower than the maximum power density operating pressure, Δπ/2, derived elsewhere, and is a function of the solute osmotic pressure at a given mass fraction. It was also found that a minimum 1.45 kmol of ideal solute is required to produce 1 kWh of energy while a system operating at “maximum power density operating pressure” requires at least 2.9 kmol. Utilizing this methodology, it is possible to examine the effects of volumetric solution cost, operation of a module at various pressure, and operation of a constant pressure module with various feed.
Do finite size neutrally buoyant particles cluster?
Fiabane, Lionel; Pinton, Jean-Francois; Monchaux, Romain; Cartellier, Alain; Bourgoin, Mickael
2012-01-01
We investigate the preferential concentration of particles which are neutrally buoyant but with a diameter significantly larger than the dissipation scale of the carrier flow. Such particles are known not to behave as flow tracers (Qureshi et al., Phys. Re. Lett. 2007) but whether they do cluster or not remains an open question. For this purpose, we take advantage of a new turbulence generating apparatus, the Lagrangian Exploration Module which produces homogeneous and isotropic turbulence in a closed water flow. The flow is seeded with neutrally buoyant particles with diameter 700\\mum, corresponding to 4.4 to 17 times the turbulent dissipation scale when the rotation frequency of the impellers driving the flow goes from 2 Hz to 12 Hz, and spanning a range of Stokes numbers from 1.6 to 24.2. The spatial structuration of these inclusions is then investigated by a Voronoi tesselation analysis, as recently proposed by Monchaux et al. (Phys. Fluids 2010), from images of particle concentration field taken in a las...
Buoyant jet and two-phase jet-plume modeling for application to large water pools
Energy Technology Data Exchange (ETDEWEB)
Norman, Timothy L. [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States); Westinghouse Nuclear, Madison, PA 15663 (United States); Revankar, Shripad T., E-mail: shripad@ecn.purdue.ed [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States); Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-780 (Korea, Republic of)
2011-05-15
Highlights: A two-phase jet-plume model was developed to predict pool thermal response, pool surface temperature and consequently the pool cover gas pressure in enclosed spaces such as nuclear reactor wetwell. The jet-plume half-width, centerline velocity and temperature along the axis defining the plume's trajectory were solved as variables along the path. The pool surface temperature prediction is comparable to experimental data within 0.5 {sup o}C. - Abstract: Models of a single-phase liquid-into-liquid buoyant jet and a two-phase vapor-into-liquid turbulent jet-plume injected in horizontal orientation were developed for analyzing the dynamics of the mixing characteristics and thermal response for shallow submergence of the source in large pools. These models were developed from the Reynolds averaged Navier-Stokes equations in the cylindrical system for steady axisymmetric flow and incorporated the integral plume theory. The bases for the general assumptions such as self-similarity and use of Gaussian profiles to represent the velocity field across the effluent cross-section are examined. Subroutines were developed to reproduce the governing differential equations formulated from the continuity, momentum and conservation of buoyancy or energy equations which treats the jet-plume's half-width, velocity and temperature as variables and seek solutions of these variables along the jet-plume trajectory. Information on empirical closure relations obtained from experimental data such as the coefficient-of-entrainment, bubble slip velocity, momentum amplification factor, and plume spread-ratios for buoyancy and density-defect which are available for adiabatic cases were applied to the case of steam-into-water. Solutions were obtained without cross-flow in a linearly stratified ambient and then with cross-flow in a homogeneously mixed ambient for the single-phase formulation that represents a complete condensation scenario of a buoyant jet. The model was
Rudnicki, M. D.; Elderfield, H.
1993-07-01
The kinetics of iron particle formation in the neutrally buoyant plume above the TAG vent field (26 degrees N, Mid-Atlantic Ridge) have been calculated from submersible-collected CTD data within the initial 150 m of plume rise. Results show that particles form by a two-stage process: about half the iron in the high temperature vent fluid is removed as sulfides within a few seconds of venting and the remainder is removed by Fe 2+ oxidation. The pseudo-first-order rate constant for the second process has been calculated ( k1 = 0.329min -1, similar to literature values for seawater) and gives a halflife time for Fe 2+ in solution of 2.1 minutes. The kinetics of iron particle formation have been used in a conceptual model of the chemistry of the TAG plume. The average dilution at which iron oxyhydroxide particles form, E¯ Fe, is ˜ 570 from which element/Fe ratios of particles at the top of the buoyant plume have been predicted. Oxyanion/Fe ratios can be chiefly accounted for by coprecipitation for Cr (71%), V (67%), As (45%) and P (42%) but Mo (0.1%) and U (0.02%) show anomalously low coprecipitation. Th/Fe and REE/Fe ratios are greater than can be accounted for by coprecipitation, demonstrating that scavenging occurs in the buoyant plume for these elements. 98% of the Th uptake and 15-75% of the REE uptake is by scavenging. Scavenging rate constants are 3.1 * 10 -6 (nmol/kg) -1 s -1 for Th and 1.4-33* 10 -8 (nmol/kg) -1 s -1 for the REE. A scavenging model has been fitted to trace metal data previously reported for neutrally buoyant hydrothermal plume particulate samples collected above the TAG vent field. The model is based on the assumption that there is a characteristic t1/2 for the dilution of the neutrally buoyant plume and this value has been calculated, by comparing 228Th and 230Th with 234Th isotope data, as fourty-one days (λ p = 0.0170 day -1). Scavenging rate constants are 2* 10 -9 (nmol/kg) -1 s -1 for Th and 3.5-16*10 -11 (nmol/kg) -1 s -1 for the REE
Rajamane, N. P.; Nataraja, M. C.; Jeyalakshmi, R.; Nithiyanantham, S.
2016-02-01
Geopolymer concrete is zero-Portland cement concrete containing alumino-silicate based inorganic polymer as binder. The polymer is obtained by chemical activation of alumina and silica bearing materials, blast furnace slag by highly alkaline solutions such as hydroxide and silicates of alkali metals. Sodium hydroxide solutions of different concentrations are commonly used in making GPC mixes. Often, it is seen that sodium hydroxide solution of very high concentration is diluted with water to obtain SHS of desired concentration. While doing so it was observed that the solute particles of NaOH in SHS tend to occupy lower volumes as the degree of dilution increases. This aspect is discussed in this paper. The observed phenomenon needs to be understood while formulating the GPC mixes since this influences considerably the relationship between concentration and density of SHS. This paper suggests an empirical formula to relate density of SHS directly to concentration expressed by w/w.
Borrero-Echeverry, Daniel
2016-01-01
We show that aqueous solutions of ammonium thiocyanate (NH4SCN) can be used to match the index of refraction of several transparent materials commonly used in experiments, while maintaining low viscosity and density compared to other common refractive index-matching liquids. We present empirical models for estimating the index of refraction, density, and kinematic viscosity of these solutions as a function of temperature and concentration. Finally, we summarize some of the chemical compatibility of ammonium thiocyanate with materials commonly used in apparatus.
46 CFR 131.870 - Life floats and buoyant apparatus.
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Life floats and buoyant apparatus. 131.870 Section 131.870 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.870 Life floats and buoyant apparatus. (a) The name of the vessel must be plainly...
Similarity consideration of the buoyant jet resulting from hydrogen leakage
Energy Technology Data Exchange (ETDEWEB)
El-Amin, M.F.; Kanayama, H. [Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)
2009-07-15
In this paper, the similarity form is developed of a hydrogen-air buoyant jet 'forced plume' resulting from an unignited small-scale hydrogen leakage in the air. As the domain temperature is assumed to be constant and therefore the density of the mixture is a function of the concentration only, the hydrogen-air mixture is assumed to be of a linear mixing type. The rate of entrainment is assumed to be a function of the plume centerline velocity and the ratio of the mean plume and ambient densities. The local rate of entrainment may be considered to be consisted of two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. Consequently, the entrainment coefficient is taken as a variable not constant. The density will be considered as a variable in all terms of the equations of continuity, momentum and concentration. The integral models of the mass, momentum and concentration fluxes are obtained. Non-dimensional transformations known as similarity transformations and used to transform the integral model to a set of ordinary differential equations called similarity equations which are solved numerically. Under various values of Froude number, the hydrogen centerline mass fraction, jet width and centerline velocity are introduced and compared with published experimental results for a slow leak vertical hydrogen jet. (author)
Subgrid Scale Modeling for Large Eddy Simulation of Buoyant Turbulent Flows
Ghaisas, Niranjan Shrinivas
2013-01-01
Buoyancy effects due to small density differences commonly exist in turbulent fluid flows occurring in nature and in engineering applications. The large eddy simulation (LES) technique, which is being increasingly used for simulating buoyant turbulent flows, requires accurate modeling of the subgrid sclae (SGS) momentum and buoyancy fluxes. This thesis presents a series of LES and direct numerical simulation (DNS) studies towards a priori and a posteriori evaluation of existing SGS models, an...
Numerical solution for Nagumo's equation for the electron density in photorefractive materials
Magaña, Fernando
2005-03-01
We study the distribution of the electron density in a photorefractive material, using a set of nonlinear partial differential equations, that describes the physical response of photorefractive systems under inhomogeneous ilumination based on the band transport model, proposed by Kukhtarev et al. (Ferroelectrics, vol. 22, 949 (1979)). Assuming that the electron density only depends of x coordinate and taking a constant external electric field E in the same x coordinate we find that the electron density obeys a Nagumo's equation whose solution is soliton type.
Deosarkar, S. D.; Kalyankar, T. M.
2013-06-01
Density, viscosity and refractive index of aqueous solutions of metoprolol succinate of different concentrations (0.005-0.05 mol dm-3) were measured at 38°C. Apparent molar volume of resultant solutions were calculated and fitted to the Masson's equation and apparent molar volume at infinite dilution was determined graphically. Viscosity data of solutions has been fitted to the Jone-Dole equation and viscosity A- and B-coefficients were determined graphically. Physicochemical data obtained were discussed in terms of molecular interactions.
Turbulence attenuation by large neutrally buoyant particles
Cisse, Mamadou; Gibert, Mathieu; Bodenschatz, Eberhard; Bec, Jeremie
2015-01-01
Turbulence modulation by inertial-range-size, neutrally-buoyant particles is investigated experimentally in a von K\\'arm\\'an flow. Increasing the particle volume fraction $\\Phi_\\mathrm{v}$, maintaining constant impellers Reynolds number attenuates the fluid turbulence. The inertial-range energy transfer rate decreases as $\\propto\\Phi_\\mathrm{v}^{2/3}$, suggesting that only particles located on a surface affect the flow. Small-scale turbulent properties, such as structure functions or acceleration distribution, are unchanged. Finally, measurements hint at the existence of a transition between two different regimes occurring when the average distance between large particles is of the order of the thickness of their boundary layers.
Simulations of Buoyant Bubbles in Galaxy Clusters
Brüggen, M
2003-01-01
It is generally argued that most clusters of galaxies host cooling flows in which radiative cooling in the centre causes a slow inflow. However, recent observations by Chandra and XMM conflict with the predicted cooling flow rates. Here we report highly resolved hydrodynamic simulations which show that buoyant bubbles can offset the cooling in the inner regions of clusters and can significantly delay the deposition of cold gas. The subsonic rise of bubbles uplifts colder material from the central regions of the cluster. This colder material appears as bright rims around the bubbles. The bubbles themselves appear as depressions in the X-ray surface brightness as observed in a growing number of clusters.
Directory of Open Access Journals (Sweden)
D. K. Narvilkar
1979-07-01
Full Text Available In the present paper, the equations of internal ballistics of composite charge consisting of N component charge with quadratic form are solved. Largange density approximation and hydrodynamic flow behaviour, have been assumed and the solutions are obtained for the composite charge for these assumptions.
Directory of Open Access Journals (Sweden)
D. K. Narvilkar
1977-10-01
Full Text Available This paper gives the solution of the equations of internal ballistics of a gun by taking the exact form of density of the propellent gases obtained on the basis of lagrange approximation. A general quadratic form functions is used.
Effect of current density on distribution coefficient of solute at solid-liquid interface
Institute of Scientific and Technical Information of China (English)
常国威; 王自东; 吴春京; 胡汉起
2003-01-01
When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interfaceenergy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between thedistribution of solute at solid-liquid interface and current density was established, and the effect of current on thedistribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and theradius of curvature at the dendritic tip was discussed. The results show that as the current density increases, thedistribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm2 , thelatter varies significantly.
Boutelier, D.; Cruden, A.; Saumur, B.
2016-05-01
Analogue models often require that materials with specific physical properties be engineered to satisfy scaling conditions. To achieve this goal we investigate the rheology of aqueous solutions of Natrosol 250 HH, a rheology modifier employed in various industries to thicken viscous solutions. We report the rheological properties as functions of the concentration and temperature and discuss the advantages and limitations of these materials in view of their use in analogue modelling experiments. The solutions are linear visco-elastic for low stresses (or strain-rates), becoming shear-thinning for larger stresses. For the typically slow analogue experiments of tectonics, the solutions can be considered linear visco-elastic with a Maxwell relaxation time much smaller than the characteristic observation time. This simplification is even more appropriate when the solutions are employed at temperatures higher than 20 °C, since the solutions then display a behaviour that is more viscous, less elastic at the same shear-rate, while the Newtonian viscosity reduces and the shear-rate limit between Newtonian and shear-thinning behaviours increases. The Newtonian viscosity is shown to increase non-linearly with concentration and decrease non-linearly with temperature. With concentrations between 0 and 3% and temperature between 20 and 40 °C, the viscosity varied between 10-1 and 4000 Pa s, while the density remained close to the density of water. Natrosol 250 HH thus offers the possibility to control the viscosity of a solution without significantly affecting the density, thereby facilitating the design and setup of analogue experiments.
A modeling of buoyant gas plume migration
Energy Technology Data Exchange (ETDEWEB)
Silin, D.; Patzek, T.; Benson, S.M.
2008-12-01
This work is motivated by the growing interest in injecting carbon dioxide into deep geological formations as a means of avoiding its atmospheric emissions and consequent global warming. Ideally, the injected greenhouse gas stays in the injection zone for a geologic time, eventually dissolves in the formation brine and remains trapped by mineralization. However, one of the potential problems associated with the geologic method of sequestration is that naturally present or inadvertently created conduits in the cap rock may result in a gas leakage from primary storage. Even in a supercritical state, the carbon dioxide viscosity and density are lower than those of the formation brine. Buoyancy tends to drive the leaked CO{sub 2} plume upward. Theoretical and experimental studies of buoyancy-driven supercritical CO{sub 2} flow, including estimation of time scales associated with plume evolution and migration, are critical for developing technology, monitoring policy, and regulations for safe carbon dioxide geologic sequestration. In this study, we obtain simple estimates of vertical plume propagation velocity taking into account the density and viscosity contrast between CO{sub 2} and brine. We describe buoyancy-driven countercurrent flow of two immiscible phases by a Buckley-Leverett type model. The model predicts that a plume of supercritical carbon dioxide in a homogeneous water-saturated porous medium does not migrate upward like a bubble in bulk water. Rather, it spreads upward until it reaches a seal or until it becomes immobile. A simple formula requiring no complex numerical calculations describes the velocity of plume propagation. This solution is a simplification of a more comprehensive theory of countercurrent plume migration (Silin et al., 2007). In a layered reservoir, the simplified solution predicts a slower plume front propagation relative to a homogeneous formation with the same harmonic mean permeability. In contrast, the model yields much higher
Genetic search for an optimal power flow solution from a high density cluster
Energy Technology Data Exchange (ETDEWEB)
Amarnath, R.V. [Hi-Tech College of Engineering and Technology, Hyderabad (India); Ramana, N.V. [JNTU College of Engineering, Jagityala (India)
2008-07-01
This paper proposed a novel method to solve optimal power flow (OPF) problems. The method is based on a genetic algorithm (GA) search from a High Density Cluster (GAHDC). The algorithm of the proposed method includes 3 stages, notably (1) a suboptimal solution is obtained via a conventional analytical method, (2) a high density cluster, which consists of other suboptimal data points from the first stage, is formed using a density-based cluster algorithm, and (3) a genetic algorithm based search is carried out for the exact optimal solution from a low population sized, high density cluster. The final optimal solution thoroughly satisfies the well defined fitness function. A standard IEEE 30-bus test system was considered for the simulation study. Numerical results were presented and compared with the results of other approaches. It was concluded that although there is not much difference in numerical values, the proposed method has the advantage of minimal computational effort and reduced CPU time. As such, the method would be suitable for online applications such as the present Optimal Power Flow problem. 24 refs., 2 tabs., 4 figs.
Iterative solutions to the steady-state density matrix for optomechanical systems.
Nation, P D; Johansson, J R; Blencowe, M P; Rimberg, A J
2015-01-01
We present a sparse matrix permutation from graph theory that gives stable incomplete lower-upper preconditioners necessary for iterative solutions to the steady-state density matrix for quantum optomechanical systems. This reordering is efficient, adding little overhead to the computation, and results in a marked reduction in both memory and runtime requirements compared to other solution methods, with performance gains increasing with system size. Either of these benchmarks can be tuned via the preconditioner accuracy and solution tolerance. This reordering optimizes the condition number of the approximate inverse and is the only method found to be stable at large Hilbert space dimensions. This allows for steady-state solutions to otherwise intractable quantum optomechanical systems. PMID:25679739
Iterative solutions to the steady state density matrix for optomechanical systems
Nation, P D; Blencowe, M P; Rimberg, A J
2014-01-01
We present a sparse matrix permutation from graph theory that gives stable incomplete Lower-Upper (LU) preconditioners necessary for iterative solutions to the steady state density matrix for quantum optomechanical systems. This reordering is efficient, adding little overhead to the computation, and results in a marked reduction in both memory and runtime requirements compared to other solution methods, with performance gains increasing with system size. Either of these benchmarks can be tuned via the preconditioner accuracy and solution tolerance. This reordering optimizes the condition number of the approximate inverse, and is the only method found to be stable at large Hilbert space dimensions. This allows for steady state solutions to otherwise intractable quantum optomechanical systems.
The shape and behaviour of a horizontal buoyant jet adjacent to a surface
Burridge, Henry; Hunt, Gary
2015-11-01
We investigate the incompressible turbulent buoyant jet formed when fluid is steadily ejected horizontally from a circular source into a quiescent environment of uniform density. As our primary focus, we introduce a horizontal boundary. For sufficiently large source-boundary separations, the buoyant jet is `free' to rise under the action of the buoyancy force. For smaller source-boundary separations, the jet attaches and `clings' to the boundary before, further downstream, pulling away from the boundary. Based on measurements of saline jets in freshwater we deduce the conditions required for a jet to cling. We present data for the variation in volume flux, flow envelope and centreline for both `clinging' and `free' jets. For source Froude numbers fr0 >= 12 the data collapses when scaled, identifying universal behaviours for both clinging jets and for free jets. The support and funding from Dyson Technology Ltd is gratefully acknowledged.
Wake-driven dynamics of finite-sized buoyant spheres in turbulence
Mathai, Varghese; Brons, Jon; Sun, Chao; Lohse, Detlef
2015-01-01
Particles suspended in turbulent flows are affected by the turbulence, and at the same time act back on the flow. The resulting coupling can give rise to rich variability in their dynamics. Here we report experimental results from an investigation on finite-sized buoyant spheres in turbulence. We find that even a marginal reduction in the particle's density from that of the fluid can result in strong modification of its dynamics. In contrast to classical spatial filtering arguments and predictions of particle models, we find that the particle acceleration variance increases with size. We trace this reversed trend back to the growing contribution from wake-induced forces, unaccounted for in current particle models in turbulence. Our findings highlight the need for improved multi-physics based models that account for particle wake effects for a faithful representation of buoyant sphere dynamics in turbulence.
Wake-Driven Dynamics of Finite-Sized Buoyant Spheres in Turbulence.
Mathai, Varghese; Prakash, Vivek N; Brons, Jon; Sun, Chao; Lohse, Detlef
2015-09-18
Particles suspended in turbulent flows are affected by the turbulence and at the same time act back on the flow. The resulting coupling can give rise to rich variability in their dynamics. Here we report experimental results from an investigation of finite-sized buoyant spheres in turbulence. We find that even a marginal reduction in the particle's density from that of the fluid can result in strong modification of its dynamics. In contrast to classical spatial filtering arguments and predictions of particle models, we find that the particle acceleration variance increases with size. We trace this reversed trend back to the growing contribution from wake-induced forces, unaccounted for in current particle models in turbulence. Our findings highlight the need for improved multiphysics based models that account for particle wake effects for a faithful representation of buoyant-sphere dynamics in turbulence. PMID:26430995
Buoyant Bubbles and the Disturbed Cool Core of Abell 133
Randall, Scott W.; Clarke, T.; Nulsen, P.; Owers, M.; Sarazin, C.; Forman, W.; Jones, C.; Murray, S.
2010-03-01
X-ray cavities, often filled with radio-emitting plasma, are routinely observed in the intracluster medium of clusters of galaxies. These cavities, or "bubbles", are evacuated by jets from central AGN and subsequently rise buoyantly, playing a vital role in the "AGN feedback" model now commonly evoked to explain the balance between heating and radiative cooling in cluster cores. As the bubbles rise, they can displace cool central gas, promoting mixing and the redistribution of metals. I will show a few examples of buoyant bubbles, then argue that the peculiar morphology of the Abell 133 is due to buoyant lifting of cool central gas by a radio-filled bubble.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
To analyze the effect of basic variable on failure probability in reliability analysis,a moment-independent importance measure of the basic random variable is proposed,and its properties are analyzed and verified.Based on this work,the importance measure of the basic variable on the failure probability is compared with that on the distribution density of the response.By use of the probability density evolution method,a solution is established to solve two importance measures,which can efficiently avoid the difficulty in solving the importance measures.Some numerical examples and engineering examples are used to demonstrate the proposed importance measure on the failure probability and that on the distribution density of the response.The results show that the proposed importance measure can effectively describe the effect of the basic variable on the failure probability from the distribution density of the basic variable.Additionally,the results show that the established solution on the probability density evolution is efficient for the importance measures.
Some Exact Self-Similar Solutions to a Density-Dependent Reaction-Diffusion Model
Ngamsaad, Waipot
2012-01-01
In this paper, we investigated a density-dependent reaction-diffusion equation, $u_t = (u^{m})_{xx} + u - u^{m}$. This equation is known as the extension of the Fisher or Kolmogoroff-Petrovsky-Piscounoff equation which is widely used in the population dynamics, combustion theory and plasma physics. By employing the suitable transformation, this equation was mapped to the anomalous diffusion equation where the nonlinear reaction term was eliminated. Due to its simpler form, some exact self-similar solutions with the compact support have been obtained. The solutions, evolving from an initial state, converge to the usual traveling wave at a certain transition time. Hence, it is quite clear the connection between self-similar solution and the traveling wave solution from these results. Moreover, the solutions were found in the manner that either propagates to the right or propagates to the left. Furthermore, the two solutions form a symmetric solution, expanding in both directions. The application on the spatiote...
Intravaia, F; Messina, Andrea
2003-01-01
An original method to exactly solve the non-Markovian Master Equation describing the interaction of a single harmonic oscillator with a quantum environment in the weak coupling limit is reported. By using a superoperatorial approach we succeed in deriving the operatorial solution for the density matrix of the system. Our method is independent of the physical properties of the environment. We show the usefulness of our solution deriving explicit expressions for the dissipative time evolution of some observables of physical interest for the system, such as, for example, its mean energy.
Li, Jinkai
2016-01-01
In this paper, we consider the initial-boundary value problem to the nonhomogeneous incompressible Navier-Stokes equations. Local strong solutions are established, for any initial data $(\\rho_0, u_0)\\in (W^{1,\\gamma} \\cap L^\\infty)\\times H_{0,\\sigma}^1$, with $\\gamma>1$, and if $\\gamma\\geq2$, then the strong solution is unique. The initial density is allowed to be nonnegative, and in particular, the initial vacuum is allowed. The assumption on the initial data is weaker than the previous wide...
CONSEQUENCES OF NON-LINEAR DENSITY EFFECTS ON BUOYANCY AND PLUME BEHAVIOR
Aquatic plumes, as turbulent streams, grow by entraining ambient water. Buoyant plumes rise and dense ones sink, but, non-linear kinetic effects can reverse the buoyant force in mid-phenomenon. The class of nascent-density plumes begin as buoyant, upwardly accelerating plumes tha...
On polynomial solutions to Fokker–Planck and sinked density evolution equations
International Nuclear Information System (INIS)
We analytically solve for the time dependent solutions of various density evolution models. With specific forms of the diffusion, drift and sink coefficients, the eigenfunctions can be expressed in terms of hypergeometric functions. We obtain the relevant discrete and continuous spectra for the eigenfunctions. With non-zero sink terms the discrete spectra eigenfunctions are generalizations of well known orthogonal polynomials: the so-called associated-Laguerre, Bessel, Fisher–Snedecor and Romanovski functions. We use MacRobert’s proof to obtain closed form expressions for the continuous normalization of the Romanovski density function. Finally, we apply our results to obtain the analytical solutions associated with the Bertalanffy–Richards–Langevin equation. (paper)
Ohsaku, T; Yamaki, D; Yamaguchi, K
2002-01-01
For studying the group theoretical classification of the solutions of the density functional theory in relativistic framework, we propose quantum electrodynamical density-matrix functional theory (QED-DMFT). QED-DMFT gives the energy as a functional of a local one-body $4\\times4$ matrix $Q(x)\\equiv -$, where $\\psi$ and $\\bar{\\psi}$ are 4-component Dirac field and its Dirac conjugate, respectively. We examine some characters of QED-DMFT. After these preparations, by using Q(x), we classify the solutions of QED-DMFT under O(3) rotation, time reversal and spatial inversion. The behavior of Q(x) under nonrelativistic and ultrarelativistic limits are also presented. Finally, we give plans for several extensions and applications of QED-DMFT.
Size-dependent error of the density functional theory ionization potential in vacuum and solution
International Nuclear Information System (INIS)
Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. In vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional
Size-dependent error of the density functional theory ionization potential in vacuum and solution
Energy Technology Data Exchange (ETDEWEB)
Sosa Vazquez, Xochitl A.; Isborn, Christine M., E-mail: cisborn@ucmerced.edu [Chemistry and Chemical Biology, School of Natural Sciences, University of California, Merced, 5200 North Lake Road, Merced, California 95343 (United States)
2015-12-28
Density functional theory is often the method of choice for modeling the energetics of large molecules and including explicit solvation effects. It is preferable to use a method that treats systems of different sizes and with different amounts of explicit solvent on equal footing. However, recent work suggests that approximate density functional theory has a size-dependent error in the computation of the ionization potential. We here investigate the lack of size-intensivity of the ionization potential computed with approximate density functionals in vacuum and solution. We show that local and semi-local approximations to exchange do not yield a constant ionization potential for an increasing number of identical isolated molecules in vacuum. Instead, as the number of molecules increases, the total energy required to ionize the system decreases. Rather surprisingly, we find that this is still the case in solution, whether using a polarizable continuum model or with explicit solvent that breaks the degeneracy of each solute, and we find that explicit solvent in the calculation can exacerbate the size-dependent delocalization error. We demonstrate that increasing the amount of exact exchange changes the character of the polarization of the solvent molecules; for small amounts of exact exchange the solvent molecules contribute a fraction of their electron density to the ionized electron, but for larger amounts of exact exchange they properly polarize in response to the cationic solute. In vacuum and explicit solvent, the ionization potential can be made size-intensive by optimally tuning a long-range corrected hybrid functional.
The Multiphase Buoyant Plume Solution of the Dusty Gas Model
Cerminara, Matteo
2015-01-01
Starting from the balance equations of mass, momentum and energy we formulate an integral 1D model for a poly-disperse mixture injected in the atmosphere. We write all the equations, either in their most general formulation or in the more simplified, taking particular care in considering all the underlying hypothesis in order to make clear when it is possible and appropriate to use them. Moreover, we put all the equations in a non-dimensional form, making explicit all the dimensionless parameters that drive the dynamics of these phenomena. In particular, we find parameters to measure: the goodness of the Boussinesq approximation, the injected mass flow, the column stability and his eventual collapse, and the importance of the atmospheric stratification, the initial kinetic energy and the gravitational potential energy. We show that setting to zero some of these parameters, it is possible to recover some of the existing jet and plume models for single-phase flows. Moreover, we write a simplified set of equatio...
Polar-solvation classical density-functional theory for electrolyte aqueous solutions near a wall
Warshavsky, Vadim; Marucho, Marcelo
2016-04-01
A precise description of the structural and dielectric properties of liquid water is critical to understanding the physicochemical properties of solutes in electrolyte solutions. In this article, a mixture of ionic and dipolar hard spheres is considered to account for water crowding and polarization effects on ionic electrical double layers near a uniformly charged hard wall. As a unique feature, solvent hard spheres carrying a dipole at their centers were used to model water molecules at experimentally known concentration, molecule size, and dipolar moment. The equilibrium ionic and dipole density profiles of this electrolyte aqueous model were calculated using a polar-solvation classical density-functional theory (PSCDFT). These profiles were used to calculate the charge density distribution, water polarization, dielectric permittivity function, and mean electric potential profiles as well as differential capacitance, excess adsorptions, and wall-fluid surface tension. These results were compared with those corresponding to the pure dipolar model and unpolar primitive solvent model of electrolyte aqueous solutions to understand the role that water crowding and polarization effects play on the structural and thermodynamic properties of these systems. Overall, PSCDFT predictions are in agreement with available experimental data.
International Nuclear Information System (INIS)
In this paper, we analyze two semiconductor optical amplifier (SOA) structures, traveling-wave and reflective, with the active region made of the bulk material. The model is based on the stationary traveling-wave equations for forward and backward propagating photon densities of the signal and the amplified spontaneous emission, along with the stationary carrier rate equation. We start by introducing linear approximation of the carrier density spatial distribution, which enables us to find solutions for the photon densities in a closed analytical form. An analytical approach ensures a low computational resource occupation and an easy analysis of the parameters influencing the SOA’s response. The comparison of the analytical and numerical results shows high agreement for a wide range of the input optical powers and bias currents. (paper)
An Experimental Investigation on Inclined Negatively Buoyant Jets
Directory of Open Access Journals (Sweden)
Raed Bashitialshaaer
2012-09-01
Full Text Available An experimental study was performed to investigate the behavior of inclined negatively buoyant jets. Such jets arise when brine is discharged from desalination plants. A turbulent jet with a specific salinity was discharged through a circular nozzle at an angle to the horizontal into a tank with fresh water and the spatial evolution of the jet was recorded. Four different initial jet parameters were changed, namely the nozzle diameter, the initial jet inclination, the jet density and the flow rate. Five geometric quantities describing the jet trajectory that are useful in the design of brine discharge systems were determined. Dimensional analysis demonstrated that the geometric jet quantities studied, if normalized with the jet exit diameter, could be related to the densimetric Froude number. Analysis of the collected data showed that this was the case for a Froude number less than 100, whereas for larger values of the Froude number the scatter in the data increased significantly. As has been observed in some previous investigations, the slope of the best-fit straight line through the data points was a function of the initial jet angle (θ, where the slope increased with θ for the maximum levels (Y_{m} studied, but had a more complex behavior for horizontal distances.
The Centaurus A Northern Middle Lobe as a Buoyant Bubble
Saxton, C J; Bicknell, G V; Saxton, Curtis J.; Sutherland, Ralph S.; Bicknell, Geoffrey V.
2001-01-01
We model the northern middle radio lobe of Centaurus A (NGC 5128) as a buoyant bubble of plasma deposited by an intermittently active jet. The extent of the rise of the bubble and its morphology imply that the ratio of its density to that of the surrounding ISM is less than 10^{-2}, consistent with our knowledge of extragalactic jets and minimal entrainment into the precursor radio lobe. Using the morphology of the lobe to date the beginning of its rise through the atmosphere of Centaurus A, we conclude that the bubble has been rising for approximately 140Myr. This time scale is consistent with that proposed by Quillen et al. (1993) for the settling of post-merger gas into the presently observed large scale disk in NGC 5128, suggesting a strong connection between the delayed re-establishment of radio emission and the merger of NGC 5128 with a small gas-rich galaxy. This suggests a connection, for radio galaxies in general, between mergers and the delayed onset of radio emission. In our model, the elongated X-...
Mass transport by buoyant bubbles in galaxy clusters
Pope, Edward C D; Pavlovski, Georgi; Bower, Richard G; Dotter, Aaron; Victoria, University of; Southampton, University of; Durham, University of
2010-01-01
We investigate the effect of three important processes by which AGN-blown bubbles transport material: drift, wake transport and entrainment. The first of these, drift, occurs because a buoyant bubble pushes aside the adjacent material, giving rise to a net upward displacement of the fluid behind the bubble. For a spherical bubble, the mass of upwardly displaced material is roughly equal to half the mass displaced by the bubble, and should be ~ 10^{7-9} solar masses depending on the local ICM and bubble parameters. We show that in classical cool core clusters, the upward displacement by drift may be a key process in explaining the presence of filaments behind bubbles. A bubble also carries a parcel of material in a region at its rear, known as the wake. The mass of the wake is comparable to the drift mass and increases the average density of the bubble, trapping it closer to the cluster centre and reducing the amount of heating it can do during its ascent. Moreover, material dropping out of the wake will also ...
Density and activity of perrhenic acid aqueous solutions at T = 298.15 K
International Nuclear Information System (INIS)
Highlights: • Water activity and osmolality measurements on highly concentrated perrhenic acid binary solutions have been carried out. • The study led to a new expression of the stoichiometric activity coefficient γ±vs. m. • The parameters of the two most frequently referenced Pitzer and specific interaction theory models have been determined. • The partial molar volume has been calculated. • The density law of the binary solution as a function of its concentration has been determined. - Abstract: Published isopiestic molalities for aqueous HReO4 solutions at T = 298.15 K are completed. Binary data (variation of the osmotic coefficient and activity coefficient of the electrolyte in solution in the water) at T = 298.15 K for perrhenic acid HReO4 are determined by direct water activity and osmolality measurements. The variation of the osmotic coefficient of this acid in water is represented mathematically according to a model recommended by the National Institute of Standards and Technology and according to the specific interaction theory. The data are also used to evaluate the parameters of the standard three-parameters of Pitzer’s ion-interaction model, along with the parameters of Archer’s four-parameter extended ion-interaction model, to higher molalities than previously advised. Experimental thermodynamic data are well represented by these models. Density variations at T = 298.15 K are also established and used to express the activity coefficient values on both the molar and molal concentration scales
Soliton solutions of an improved quark mass density-dependent model at finite temperature
International Nuclear Information System (INIS)
The improved quark mass density-dependent model (IQMDD) based on soliton bag model is studied at finite temperature. Applying the finite temperature field theory, the effective potential of the IQMDD model and the bag constant B(T) have been calculated at different temperatures. It is shown that there is a critical temperature TC≅110 MeV. We also calculate the soliton solutions of the IQMDD model at finite temperature. It turns out that when TC, there is a bag constant B(T) and the soliton solutions are stable. However, when T>TC the bag constant B(T)=0 and there is no soliton solution, therefore, the confinement of quarks are removed quickly
International Nuclear Information System (INIS)
Highlights: • We study flow structure in highly buoyant jet with inflow. • Three-dimensional velocity field is measured by scanning stereo PIV. • We examine flow structure by three-dimensional POD analysis. • Magnitude and scale of velocity fluctuation in POD mode is discussed. • Role of cross-flow across longitudinal structure is reported. - Abstract: The flow characteristics and the structure of highly buoyant jet of low density fluid issuing into a stagnant surrounding of high density fluid is studied by scanning stereo PIV combined with proper orthogonal decomposition (POD) analysis. The experiment is carried out at Froude number of 0.3 and Reynolds number of 200, which satisfies the inflow condition due to the unstable density gradient near the nozzle exit. An increase in the maximum mean velocity occurs and the vertical velocity fluctuation is highly amplified near the nozzle exit, which suggests the influence of inflow due to the unstable density gradient. The POD analysis indicates that the vertical velocity fluctuation is the major source of fluctuating energy contributing to the development of the highly buoyant jet. The examination of the POD modes show that the longitudinal structure of the vertical velocity fluctuation is generated along the jet axis having the opposite sign of velocity fluctuation on both sides of the jet axis. The vertical scale of the POD mode decreases with increasing the mode number and results in the frequent appearance of cross-flow across the buoyant jet. The reconstruction flow from the POD modes indicates that the vortex structure is caused by the highly sheared layer between the upward and downward velocity and the inflow is induced by the vortex structure. The magnitude of the vortex structure seems to be weakened with an increase in the distance from the nozzle and the buoyant jet approaches to an asymptotic state in the further downstream
Peterson, Karen I.
2008-01-01
The experiment developed in this article addresses the concept of equipment calibration for reducing systematic error. It also suggests simple student-prepared sucrose solutions for which accurate densities are known, but not readily available to students. Densities are measured with simple glassware that has been calibrated using the density of…
Csörgö, T; Csanad, M
2007-01-01
A new class of accelerating, exact, explicit and simple solutions of relativistic hydrodynamics is presented. Since these new solutions yield a finite rapidity distribution, they lead to an advanced estimate of the initial energy density and life-time of high energy heavy ion reactions. Accelerating solutions are also given for spherical expansions in arbitrary number of spatial dimensions.
Mass transport by buoyant bubbles in galaxy clusters
Pope, Edward C. D.; Babul, Arif; Pavlovski, Georgi; Bower, Richard G.; Dotter, Aaron
2010-08-01
We investigate the effect of three important processes by which active galactic nuclei (AGN)-blown bubbles transport material: drift, wake transport and entrainment. The first of these, drift, occurs because a buoyant bubble pushes aside the adjacent material, giving rise to a net upward displacement of the fluid behind the bubble. For a spherical bubble, the mass of upwardly displaced material is roughly equal to half the mass displaced by the bubble and should be ~ 107-9 Msolar depending on the local intracluster medium (ICM) and bubble parameters. We show that in classical cool-core clusters, the upward displacement by drift may be a key process in explaining the presence of filaments behind bubbles. A bubble also carries a parcel of material in a region at its rear, known as the wake. The mass of the wake is comparable to the drift mass and increases the average density of the bubble, trapping it closer to the cluster centre and reducing the amount of heating it can do during its ascent. Moreover, material dropping out of the wake will also contribute to the trailing filaments. Mass transport by the bubble wake can effectively prevent the buildup of cool material in the central galaxy, even if AGN heating does not balance ICM cooling. Finally, we consider entrainment, the process by which ambient material is incorporated into the bubble. Studies of observed bubbles show that they subtend an opening angle much larger than predicted by simple adiabatic expansion. We show that bubbles that entrain ambient material as they rise will expand faster than the adiabatic prediction; however, the entrainment rate required to explain the observed opening angle is large enough that the density contrast between the bubble and its surroundings would disappear rapidly. We therefore conclude that entrainment is unlikely to be a dominant mass transport process. Additionally, this also suggests that the bubble surface is much more stable against instabilities that promote
International Nuclear Information System (INIS)
A three-parameter equation, describing with a high accuracy the density and reduced (molar, specific) volumes (V) of individual substances and solutions in any aggregate state as the function of temperature and pressure, is suggested. By the equation differentiation analytic expressions for actual coefficient of isobaric thermal expansion and coefficient of isothermal compression of substances and solutions are obtained. The calculated and table values of the coefficients for water under atmospheric pressure and temperatures of 283-353K are compared. Applicability of the equation V(T, p) is illustrated using concrete examples, i.e. Th, U, Pu, uranium fluorides and nitrates, TBP and other substances, essential for the practice of extraction reprocessing of irradiated fuel and other processes of nuclear fuel cycle
Morrison, Benjamin C.; Borrero-Echeverry, Daniel
2015-11-01
Index-matching fluids play an important role in many fluid dynamics experiments, particularly those involving particle tracking, as they can be used to minimize errors due to distortion from the refraction of light across interfaces of the apparatus. Common index-matching fluids, such as sodium iodide solutions or mineral oils, often have densities or viscosities very different from those of water. This can make them undesirable for use as a working fluid when using commercially available tracer particles or at high Reynolds numbers. A solution of ammonium thiocyanate (NH4SCN) can be used for index-matching common materials such as borosilicate glass and acrylic, and has material properties similar to those of water (ν ~ 1 . 6 cSt and ρ ~ 1 . 1 g/cc). We present an empirical model for predicting the refractive index of aqueous NH4SCN solutions as a function of temperature and NH4SCN concentration that allows experimenters to develop refractive index matching solutions for various common materials. This work was supported by the National Science Foundation (CBET-0853691) and by the James Borders Physics Student Fellowship at Reed College.
Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
Nelson, Nicholas J; Brun, A Sacha; Miesch, Mark S; Toomre, Juri
2012-01-01
Our global 3D simulations of convection and dynamo action in a Sun-like star reveal that persistent wreaths of strong magnetism can be built within the bulk of the convention zone. Here we examine the characteristics of buoyant magnetic structures that are self-consistently created by dynamo action and turbulent convective motions in a simulation with solar stratification but rotating at three times the current solar rate. These buoyant loops originate within sections of the magnetic wreaths in which turbulent flows amplify the fields to much larger values than is possible through laminar processes. These amplified portions can rise through the convective layer by a combination of magnetic buoyancy and advection by convective giant cells, forming buoyant loops. We measure statistical trends in the polarity, twist, and tilt of these loops. Loops are shown to preferentially arise in longitudinal patches somewhat reminiscent of active longitudes in the Sun, although broader in extent. We show that the strength o...
Densities and solubilities of Glycylglycine and Glycyl-L-Alanine in Aqueous Electrolyte Solutions
DEFF Research Database (Denmark)
Breil, Martin Peter; Mollerup, Jørgen; Rudolph, E. Susanne J.;
2004-01-01
higher salt concentrations in NaCl and Na2SO4, and in (NH4)(2)SO4 the solubility is almost constant. The densities of the solutions have been determined experimentally, and the volume expansions by dissolving salt and dipeptide in water have been calculated. (C) 2003 Elsevier B.V. All rights reserved....... 1.74 and 4.78 mol/kg of water, respectively. The solubility of glycylglycine in salt solutions of NaCl, Na2SO4, and (NH4)(2)SO4 show a moderate salting-in effect. The solubility of glycyl-L-alanine show a minor or no salting-in effect at low salt concentrations and a moderate salting-out effect at......Solubilities of glycylglycine and glycyl-L-alanine in aqueous electrolyte solutions containing 0-6 molal NaCl, 0-1 molal Na2SO4, and 0-1 molal (NH4)(2)SO4, have been determined experimentally at 298.15 K and atmospheric pressure. The solubility of glycylglycine and glycyl-L-alanine in pure water is...
Thompson, Alex J; Eniola-Adefeso, Omolola
2015-07-01
For vascular-targeting carrier (VTC) systems to be effective, carriers must be able to localize and adhere to the vascular wall at the target site. Research suggests that neutrally buoyant nanoparticles are limited by their inability to localize to the endothelium, making them sub-optimal as carriers. This study examines whether particle density can be exploited to improve the targeting (localization and adhesion) efficiency of nanospheres to the vasculature. Silica spheres with 500 nm diameter, which have a density roughly twice that of blood, exhibit improved adhesion to inflamed endothelium in an in vitro model of human vasculature compared to neutrally buoyant polystyrene spheres of the same size. Silica spheres also display better near-wall localization in the presence of red blood cells than they do in pure buffer, likely resulting in the observed improvement in adhesion. Titania spheres (4 times more dense than blood) adhere at levels higher than polystyrene, but only in conditions when gravity or centrifugal force acts in the direction of adhesion. In light of the wide array of materials proposed for use as carrier systems for drug delivery and diagnostics, particle density may be a useful tool for improving the targeting of diseased tissues. PMID:25870170
On the near field behavior of inclined negatively buoyant jets
Directory of Open Access Journals (Sweden)
Besalduch L.A.
2014-03-01
Full Text Available We have performed an experimental campaign in the laboratory on the near field behavior of inclined negatively buoyant jets, issuing from a circular sharp-edged orifice, in order to investigate the symmetry properties of this phenomenon. The velocity measurements were obtained via a non intrusive image analysis technique, namely Feature Tracking Velocimetry. We present here both first and second order statistics, showing that the asymmetry of inclined negatively buoyant jets cannot be considered only a far field feature of this phenomenon, as it arises very close to the release point.
Horizontal H 2-air turbulent buoyant jet resulting from hydrogen leakage
El-Amin, Mohamed
2012-02-01
The current article is devoted to introducing mathematical and physical analyses with numerical investigation of a buoyant jet resulting from hydrogen leakage in air from a horizontal round source. H 2-air jet is an example of the non-Boussinesq buoyant jet in which a low-density gas jet is injected/leak into a high-density ambient. The density of the mixture is a function of the concentration only, the binary gas mixture is assumed to be of a linear mixing type and the rate of entrainment is assumed to be a function of the plume centerline velocity and the ratio of the mean plume and ambient densities. On the other hand, the local rate of entrainment consists of two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. The top-hat profile assumption is used to obtain the mean centerline velocity, width, density and concentration of the H 2-air horizontal jet in addition to kinematic relations which govern the jet trajectories. A set of ordinary differential equations is obtained and solved numerically using Runge-Kutta method. In the second step, the mean axial velocity, mean concentration and mean density of the jet are obtained based on Gaussian model. Finally, several quantities of interest, including the cross-stream velocity, Reynolds stress, velocity-concentration correlation (radial flux), turbulent eddy viscosity and turbulent eddy diffusivity, are obtained by solving the governing partial differential equations. Additionally, the turbulent Schmidt number is estimated and the normalized jet-feed material density and the normalized momentum flux density are correlated. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Accuracy of wind tunnel modeling of buoyant plume rise around buildings
International Nuclear Information System (INIS)
Dispersion modeling of buoyant exhausts in the vicinity of building clusters, such as from boilers, incinerators, and diesel generators, is often conducted using wind tunnel modeling. The receptors of interest are usually air intakes within the building clusters. Exact wind tunnel modeling of buoyant plume rise requires stack exhaust Froude number scaling between model simulations and the full scale, along with undistorted exit densities and ratios of exit velocity to approach wind speed. The Froude number requirements constrains the air speed in the tunnel to be lower than 0.5 m/s for typical geometric scale reductions. Such low air speeds can make the air flow around the buildings Reynolds number dependent, an undesirable result. Distortions of exhaust density ratios and of exit diameters have been suggested in the past to maintain higher tunnel speeds. Davidson has presented an analytical plume rise equation which combines the 1/3 and 2/3 exponent laws for momentum-dominated and buoyancy-dominated plume rise. The analytical model was reported to compare well with water flume data. Davidson also recommends that the equation can be used to predict the errors in modeled plume rise when various wind tunnel modeling schemes are used to avoid the Froude number modeling requirement. This paper extends the work of Davidson by comparing the analytical equation to several wind tunnel and field plume rise databases. The analytical equation is then used to examine wind tunnel modeling schemes for two types of buoyant exhausts commonly modeled near buildings: emergency diesel generators and boilers
International Nuclear Information System (INIS)
Suspension of buoyant drops at low and moderate areal fractions is studied at non-zero Reynolds numbers in simple shear flow. The flow is studied as a function of the Capillary number, the Reynolds number, the Froude number and the density ratio. It is found that the effective viscosity decreases with Capillary number. The normal stress difference increases with Capillary number. The effective viscosity and normal stress difference also depend on the Reynolds number. At a relatively low area fraction (ϕ = 0.22 ) the normal stress difference decreases with Froude number and becomes negative at large Froude numbers. At a moderate areal fraction (ϕ = 0.44 ) the behavior of the suspension is similar to the relatively low areal fraction, except that the normal stress difference is always positive. Also, the flow weakly depends on the Froude number at moderate areal fraction. The density distribution of buoyant drops across the channel is non-uniform. (paper)
Energy Technology Data Exchange (ETDEWEB)
Goodarzi, S; Mortazavi, S, E-mail: s.goodarzi@me.iut.ac.ir, E-mail: saeedm@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)
2013-08-01
Suspension of buoyant drops at low and moderate areal fractions is studied at non-zero Reynolds numbers in simple shear flow. The flow is studied as a function of the Capillary number, the Reynolds number, the Froude number and the density ratio. It is found that the effective viscosity decreases with Capillary number. The normal stress difference increases with Capillary number. The effective viscosity and normal stress difference also depend on the Reynolds number. At a relatively low area fraction (#Greek Phi Symbol# = 0.22 ) the normal stress difference decreases with Froude number and becomes negative at large Froude numbers. At a moderate areal fraction (#Greek Phi Symbol# = 0.44 ) the behavior of the suspension is similar to the relatively low areal fraction, except that the normal stress difference is always positive. Also, the flow weakly depends on the Froude number at moderate areal fraction. The density distribution of buoyant drops across the channel is non-uniform. (paper)
Directory of Open Access Journals (Sweden)
Chen Mingtao
2011-01-01
Full Text Available Abstract This article is concerned with global strong solutions of the micro-polar, compressible flow with density-dependent viscosity coefficients in one-dimensional bounded intervals. The important point in this article is that the initial density may vanish in an open subset.
International Nuclear Information System (INIS)
We study the pressureless Navier–Stokes–Poisson equations with density-dependent viscosity. With the extension of the blowup solutions for the Euler–Poisson equations, the analytical blowup solutions, in radial symmetry, in RN (N ≥ 2) are constructed
Jacob, Shery; Nair, Anroop B; Patil, Pandurang N
2011-01-01
An inert hydrophobic buoyant coated–core was developed as floating drug delivery system (FDDS) for sustained release of cisapride using direct compression technology. Core contained low density, porous ethyl cellulose, which was coated with an impermeable, insoluble hydrophobic coating polymer such as rosin. It was further seal coated with low viscosity hydroxypropyl methyl cellulose (HPMC E15) to minimize moisture permeation and better adhesion with an outer drug layer. It was found that sta...
International Nuclear Information System (INIS)
Current-sheet formation near a hyperbolic magnetic neutral line in the MHD model is investigated. In this model, the magnetic field lines are swept by the plasma flow toward the X-point. Effects of density-variation of the plasma are included. An exact analytic solution is given. This solution exhibits a finite-time singularity that is peculiar to the variable-density plasma case and this finite-time singularity occurs when there is a plasma density build-up near the magnetic neutral line
MSW Solutions to the Solar Neutrino Problem in Presence of Noisy Matter Density Fluctuations
Bykov, A A; Peña-Garay, C; Popov, V Yu; Semikoz, V B
2000-01-01
We study the effect of random matter density fluctuations in the sun on resonant neutrino conversion in matter by solving numerically the evolution equation for the neutrino system including the full effect of the random matter density fluctuations of given amplitude and correlation length. In order to establish the possible effect on the MSW solutions to the solar neutrino problem we perform a global analysis of all the existing observables including the measured total rates as well as the Super-Kamiokande measurement on the time dependence of the event rates during the day and night and the recoil electron energy spectrum. We find the effects of random noise to be larger for small mixing angles and they are mostly important for correlation lengths in the range few 100 km $\\lesssim L_0\\lesssim$ few 1000 km. They can be understood as due to a parametric resonance occuring when the phase acquired by the oscillating neutrino state on one fluctuation length L_0 is a multiple of 2$\\pi$. We find that this resonant...
PREDICTION OF CHARACTERISTICS FOR VERTICAL ROUND NEGATIVE BUOYANT JETS IN HOMOGENEOUS AMBIENT
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The k-ε turbulence model is used to establish a mathematicalmodel of a vertical round jet with negative buoyancy in a static homogeneous ambient. The hybrid finite analytic method, with a non-uniform staggered grid, is used to calculate the whole flow field. The variations of centerline velocity, density and turbulent kinetic energy along the axial line for a given exit densimetric Froude number are found to converge to single curves under the unified scaling law derived by Chen and Rodi. The profiles of mean velocities, mean density difference and the half-width of negative buoyant jets for velocity and density are given. The calculation confirmed that the maximum height of rise is proportional to M03/4B0-1/2 ,where M0 and B0 are the momentum flux and the buoyancy flux at the source, respectively.
Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
Nelson, Nicholas J.; Brown, Benjamin P.; Sacha Brun, A.; Miesch, Mark S.; Toomre, Juri
2014-02-01
Our global 3D simulations of convection and dynamo action in a Sun-like star reveal that persistent wreaths of strong magnetism can be built within the bulk of the convention zone. Here we examine the characteristics of buoyant magnetic structures that are self-consistently created by dynamo action and turbulent convective motions in a simulation with solar stratification but rotating at three times the current solar rate. These buoyant loops originate within sections of the magnetic wreaths in which turbulent flows amplify the fields to much higher values than is possible through laminar processes. These amplified portions can rise through the convective layer by a combination of magnetic buoyancy and advection by convective giant cells, forming buoyant loops. We measure statistical trends in the polarity, twist, and tilt of these loops. Loops are shown to preferentially arise in longitudinal patches somewhat reminiscent of active longitudes in the Sun, although broader in extent. We show that the strength of the axisymmetric toroidal field is not a good predictor of the production rate for buoyant loops or the amount of magnetic flux in the loops that are produced.
Surface Intermediate Zone of Submerged Turbulent Buoyant Jet in Current
DEFF Research Database (Denmark)
Chen, H. B.; Larsen, Torben
1995-01-01
This paper deals with the intermediate zone between the jet and plume stages of a submerged buoyant discharge from sea outfall in current. The stability criteria, plume width and height after the intermediate zone and the dilution within the intermediate region have been studied theoretically...
46 CFR 160.010-5 - Buoyant apparatus with plastic foam buoyancy.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Buoyant apparatus with plastic foam buoyancy. 160.010-5 Section 160.010-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Buoyant Apparatus for Merchant Vessels § 160.010-5 Buoyant apparatus...
Small dense LDL is more susceptible to glycation than more buoyant LDL in Type 2 diabetes.
Younis, Nahla N; Soran, Handrean; Pemberton, Philip; Charlton-Menys, Valentine; Elseweidy, Mohamed M; Durrington, Paul N
2013-03-01
Glycation of apoB (apolipoprotein B) of LDL (low-density lipoprotein) increases its atherogenicity. Concentrations of both serum glyc-apoB (glycated apoB) and SD-LDL (small dense LDL) (syn LDL3; D=1.044-1.063 g/ml) are increased in diabetes and are closely correlated. We studied whether SD-LDL is more susceptible to glycation in vitro than more buoyant LDL in statin- and non-statin-treated Type 2 diabetes mellitus. Serum SD-LDL apoB and glyc-apoB on statins was 20±2 (means±S.D.) and 3.6±0.41 compared with 47±3 and 5.89±0.68 mg/dl in those not receiving statins (P<0.001 and <0.01, respectively). There was a dose-dependent increase in glycation on incubation of LDL subfractions with glucose, which was accompanied by an increase in LPO (lipid peroxide) and electrophoretic mobility and a decrease in free amino groups. SD-LDL was more susceptible to these changes than more buoyant LDL. Both SD-LDL and more buoyant LDL from statin-treated patients were less susceptible to glycation. There were fewer free amino groups on LDL subfractions from statin-treated patients, which may contribute to this resistance. In conclusion, greater susceptibility of SD-LDL to glycation is likely to contribute to the raised levels of circulating glyc-apoB in diabetes. Statins are associated with lower levels of both SD-LDL and glyc-apoB. PMID:22985435
Near field characteristics of buoyant helium plumes
Indian Academy of Sciences (India)
Kuchimanchi K Bharadwaj; Debopam Das; Pavan K Sharma
2015-05-01
Puffing and entrainment characteristics of helium plumes emanating out into ambient air from a circular orifice are investigated in the present study. Velocity and density fields are measured across a diametric plane using Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) respectively in phase resolved manner. Experiments are performed in Froude numbers range 0.2–0.4 and for Reynolds numbers 58–248. Puffing frequency measurements reveal that the plume puffing frequencies are insensitive to the plume exit conditions, since the instability is buoyancy driven. The frequencies obtained in the present case are in agreement with frequencies obtained by Cetegen & Kasper (1996) for plumes originating from circular nozzles of various L/D ratios. Velocity and density measurements reveal that toroidal vortex formed during a puffing cycle entrains ambient air as it traverses downstream and this periodic engulfment governs the entrainment mechanism in pulsating plumes. The obtained velocity and density fields are used to calculate mass entrainment rates. It is revealed that though the flow is unsteady, the contribution of unsteady term in mass conservation to entrainment is negligible, and it becomes zero over a puff cycle. Finally, an empirical relation for variation of mass entrainment with height has been proposed, in which the non-dimensional mass entrainment is found to follow a power law with the non-dimensional height.
Simulations of Buoyant Plumes in Solar Prominences
Hurlburt, Neal
2012-01-01
Observations of solar prominences reveal a complex, dynamic flow field within them. The flow field within quiescent prominences is characterized by long ``threads'' and dark ``bubbles'' that fall and rise (respectively) in a thin sheet. The flow field in active prominences display more helical motions that travel along the axis of the prominence. We explore the possible dynamics of both of these with the aid of 2.5D MHD simulations. Our model, compressible plasma possesses density and temperature gradients and resides in magnetic field configurations that mimc those of a solar prominence. We present results of various configurations and discuss the nonlinear behavior of the resulting dynamics.
Simulations of Buoyant Plumes in Solar Prominences
Hurlburt, N.; Berger, T.
2012-08-01
Observations of solar prominences reveal a complex, dynamic flow field within them. The flow field within quiescent prominences is characterized by long "threads" and dark "bubbles" that fall and rise (respectively) in a thin sheet. The flow field in active prominences display more helical motions that travel along the axis of the prominence. We explore the possible dynamics of both of these with the aid of 2.5D MHD simulations. Our model, compressible plasma possesses density and temperature gradients and resides in magnetic field configurations that mimc those of a solar prominence. We present results of various configurations and discuss the nonlinear behavior of the resulting dynamics.
Integral models for buoyant plume calculations
International Nuclear Information System (INIS)
Integral models have been proven to be successful and inexpensive tools for the solution of a variety of jet-type environmental flow problems. In the Sonderforschungsbereich 80, a family of integral models has been developed for several applications as, e.g., the mixing of waste water and cooling water plumes discharged into lakes and coastal waters for the dispersion of pollutants and heat emitted by chimneys, cooling towers and urban heat islands into the atmosphere. The common features of these integral models are discussed. Finally, the quality of model results is demonstrated by comparing predictions with experimental data. (orig.)
Institute of Scientific and Technical Information of China (English)
Chen Xiao-Gang; Guo Zhi-Ping; Song Jin-Bao
2008-01-01
In the present paper,the random interfacial waves in N-layer density-stratified fluids moving at different steady uniform speeds are researched by using an expansion technique,and the second-order asymptotic solutions of the random displacements of the density interfaces and the associated velocity potentials in N-layer fluid are presented based on the small amplitude wave theory.The obtained results indicate that the wave-wave second-order nonlinear interactions of the wave components and the second-order nonlinear interactions between the waves and currents are described.As expected,the solutions include those derived by Chen(2006)as a special case where the steady uniform currents of the N-layer fluids are taken as zero,and the solutions also reduce to those obtained by Song(2005)for second-order solutions for random interracial waves with steady uniform currents if N=2.
Electronic state density distributions in TiC-VC and TiC-TiN solid solutions
International Nuclear Information System (INIS)
Using the earlier obtained calculation results of the TiC, VC and TiN band structure the state density histograms of the TiCsub(x)Nsub(1-x) and Tisub(x)Vsub(1-x)C solid solutions are constructed. The different character of the state density variation at the Fermi level with different solid solutions of the TiC-VC and TiC-TiN systems is established, and nonapplicability of the ''hard band'' model for description of their physical properties is shown
Beauty of lotus is more than skin deep: highly buoyant superhydrophobic films.
Choi, Yuri; Brugarolas, Teresa; Kang, Sung-Min; Park, Bum Jun; Kim, Byeong-Su; Lee, Chang-Soo; Lee, Daeyeon
2014-05-28
We develop highly buoyant superhydrophobic films that mimic the three-dimensional structure of lotus leaves. The high buoyancy of these structure stems from mechanically robust bubbles that significantly reduce the density of the superhydrophobic films. These highly buoyant superhydrophobic films stay afloat on water surface while carrying a load that is more than 200 times their own weight. In addition to imparting high buoyancy, the incorporation of robust hydrophilic bubbles enables the formation of free-standing structures that mimic the water-collection properties of Namib Desert beetle. We believe the incorporation of robust bubbles is a general method that opens up numerous possibilities in imparting high buoyancy to different structures that needs to stay afloat on water surfaces and can potentially be used for the fabrication of lightweight materials. (Image on the upper left reproduced with permission from Yong, J.; Yang, Q.; Chen, F.; Zhang, D.; Du, G.; Si, J.; Yun, F.; Hou, X. A Bioinspired Planar Superhydrophobic Microboat. J. Micromech. Microeng. 2014, 24, 035006). PMID:24801001
Wang, Weike; Xu, Xin
2016-06-01
In this paper, the Cauchy problem for the nonisentropic Euler-Maxwell system with a nonconstant background density is studied. The global existence of classical solution is constructed in three space dimensions provided the initial perturbation is sufficiently small. The proof is mainly based on classical energy estimate and the techniques of symmetrizer. And the time decay of the solution is also established by combining the decay estimate of the Green's function with some time-weighted estimate.
Analysis of a turbulent buoyant confined jet modeled using realizable k-ε model
El-Amin, Mohamed
2010-06-13
Through this paper, analyses of components of the unheated/heated turbulent confined jet are introduced and some models to describe them are developed. Turbulence realizable k-ε model is used to model the turbulence of this problem. Numerical simulations of 2D axisymmetric vertical hot water confined jet into a cylindrical tank have been done. Solutions are obtained for unsteady flow while velocity, pressure, temperature and turbulence distributions inside the water tank are analyzed. For seeking verification, an experiment was conducted for measuring of the temperature of the same system, and comparison between the measured and simulated temperature shows a good agreement. Using the simulated results, some models are developed to describe axial velocity, centerline velocity, radial velocity, dynamic pressure, mass flux, momentum flux and buoyancy flux for both unheated (non-buoyant) and heated (buoyant) jet. Finally, the dynamics of the heated jet in terms of the plume function which is a universal quantity and the source parameter are studied and therefore the maximum velocity can be predicted theoretically. © 2010 Springer-Verlag.
Institute of Scientific and Technical Information of China (English)
Chen Xiao-Gang; Guo Zhi-Ping; Song Jin-Bao; He Xiao-Dong; Guo Jun-Ming; Bao Shu-Hong; Cui Wei
2009-01-01
Interfacial internal waves in a three-layer density-stratified fluid are investigated using a singular perturbation method, and third-order asymptotic solutions of the velocity potentials and third-order Stokes wave solutions of the associated elevations of the interracial waves are presented based on the small amplitude wave theory. As expected, the third-order solutions describe the third-order nonlinear modification and the third-order nonlinear interactions between the interracial waves. The wave velocity depends on not only the wave number and the depth of each layer but also on the wave amplitude.
International Nuclear Information System (INIS)
In this paper, we investigate the analytical solutions of the compressible Navier-Stokes equations with dependent-density viscosity. By using the characteristic method, we successfully obtain a class of drifting solutions with elliptic symmetry for the Navier-Stokes model wherein the velocity components are governed by a generalized Emden dynamical system. In particular, when the viscosity variables are taken the same as Yuen [M. W. Yuen, “Analytical solutions to the Navier-Stokes equations,” J. Math. Phys. 49, 113102 (2008)], our solutions constitute a generalization of that obtained by Yuen. Interestingly, numerical simulations show that the analytical solutions can be used to explain the drifting phenomena of the propagation wave like Tsunamis in oceans
Energy Technology Data Exchange (ETDEWEB)
An, Hongli, E-mail: kaixinguoan@163.com [College of Science, Nanjing Agricultural University, Nanjing 210095 (China); Yuen, Manwai, E-mail: nevetsyuen@hotmail.com [Department of Mathematics and Information Technology, The Hong Kong Institute of Education, 10 Po Ling Road, Tai Po, New Territories (Hong Kong)
2014-05-15
In this paper, we investigate the analytical solutions of the compressible Navier-Stokes equations with dependent-density viscosity. By using the characteristic method, we successfully obtain a class of drifting solutions with elliptic symmetry for the Navier-Stokes model wherein the velocity components are governed by a generalized Emden dynamical system. In particular, when the viscosity variables are taken the same as Yuen [M. W. Yuen, “Analytical solutions to the Navier-Stokes equations,” J. Math. Phys. 49, 113102 (2008)], our solutions constitute a generalization of that obtained by Yuen. Interestingly, numerical simulations show that the analytical solutions can be used to explain the drifting phenomena of the propagation wave like Tsunamis in oceans.
Sawale, R. T.; Deosarkar, S. D.; Kalyankar, T. M.
2015-07-01
Density ( ρ), viscosity ( η) and refractive index ( n D) of an antiemetic drug metoclopramide (4-amino-5-chloro- N-(2-(diethylamino)ethyl)-2-methoxybenzamide hydrochloride) solutions containing amino acids (glycine, D-alanine, L-cystine and L-histidine) were measured in the concentration range 0.01-0.17 mol/dm3 at 303.15 K. The apparent molar volume (φv) of this drug in aqueous amino acid solutions was calculated from the density data and fitted to the Massons relation, and the partial molar volume φ{v/0} of the drug was determined graphically. The partial molar volumes of transfer (Δtrφ{v/0}) of drug at infinite dilution from pure water to aqueous amino acid solutions were calculated and interpreted in terms of different interactions between the drug and amino acids.
Video Image Analysis of Turbulent Buoyant Jets Using a Novel Laboratory Apparatus
Crone, T. J.; Colgan, R. E.; Ferencevych, P. G.
2012-12-01
Turbulent buoyant jets play an important role in the transport of heat and mass in a variety of environmental settings on Earth. Naturally occurring examples include the discharges from high-temperature seafloor hydrothermal vents and from some types of subaerial volcanic eruptions. Anthropogenic examples include flows from industrial smokestacks and the flow from the damaged well after the Deepwater Horizon oil leak of 2010. Motivated by a desire to find non-invasive methods for measuring the volumetric flow rates of turbulent buoyant jets, we have constructed a laboratory apparatus that can generate these types of flows with easily adjustable nozzle velocities and fluid densities. The jet fluid comprises a variable mixture of nitrogen and carbon dioxide gas, which can be injected at any angle with respect to the vertical into the quiescent surrounding air. To make the flow visible we seed the jet fluid with a water fog generated by an array of piezoelectric diaphragms oscillating at ultrasonic frequencies. The system can generate jets that have initial densities ranging from approximately 2-48% greater than the ambient air. We obtain independent estimates of the volumetric flow rates using well-calibrated rotameters, and collect video image sequences for analysis at frame rates up to 120 frames per second using a machine vision camera. We are using this apparatus to investigate several outstanding problems related to the physics of these flows and their analysis using video imagery. First, we are working to better constrain several theoretical parameters that describe the trajectory of these flows when their initial velocities are not parallel to the buoyancy force. The ultimate goal of this effort is to develop well-calibrated methods for establishing volumetric flow rates using trajectory analysis. Second, we are working to refine optical plume velocimetry (OPV), a non-invasive technique for estimating flow rates using temporal cross-correlation of image
Long-term tracking of neutrally buoyant tracer particles in two-dimensional fluid flows
Pervez, M. S.; Solomon, T. H.
1994-07-01
An experimental technique has been developed to produce and to track neutrally buoyant particles in a two-dimensional fluid flow. The key aspect of the technique is the ability to track particles for extended intervals (over an hour), which is essential for quantitative studies of transport and mixing. The approach is composed of two stages. In the first stage, digital image processing hardware partially processes the images, reducing the data rate to 50 kbyte/s (typically) and allowing several hours of data to be stored on a conventional computer disk. In the second stage, programs extract particle trajectories from the reduced data. The approach is tested in an experiment on planetary-type flows in a rotating annulus. In an appendix, a technique is discussed for fabricating wax or crayon particles with arbitrary density.
The stability of buoyant bubbles in the atmospheres of galaxy clusters
Kaiser, C R; Pope, E C D; Fangohr, H
2005-01-01
The buoyant rise of hot plasma bubbles inflated by AGN outflows in galaxy clusters can heat the cluster gas and thereby compensate radiative energy losses of this material. Numerical simulations of this effect often show the complete disruption of the bubbles followed by the mixing of the bubble material with the surrounding cluster gas due to fluid instabilities on the bubble surface. This prediction is inconsistent with the observations of apparently coherent bubble structures in clusters. We derive a general description in the linear regime of the growth of instabilities on the surface between two fluids under the influence of a gravitational field, viscosity, surface tension provided by a magnetic field and relative motion of the two fluids with respect to each other. We demonstrate that Kelvin-Helmholtz instabilities are always suppressed, if the fluids are viscous. They are also suppressed in the inviscid case for fluids of very different mass densities. We show that the effects of shear viscosity as we...
Measurements of Accelerations of Large Neutrally-buoyant Particles in Intense Turbulence
Brown, Rachel D; Voth, Greg A
2009-01-01
We measure acceleration statistics of neutrally buoyant spherical particles with diameter 0.4 , clearly resolve the transition from the tracer like behavior of small particles to the much smaller accelerations of large particles. For d>5 eta, decreases with diameter as d^{-2/3} in agreement with inertial range scaling arguments. A model relating to the pressure structure functions matches the transition from small to large particle behavior if the particles respond to pressure differences over (1.7 +- 0.3) d. A model relating to the fluid acceleration averaged over the particle diameter predicts the transition with no free parameters, but does not show clean inertial range scaling in the size range studied. Consistent with earlier work, we find that the scaled acceleration probability density function shows very little dependence on particle size.
Experiments on the fragmentation of a buoyant liquid volume in another liquid
Landeau, Maylis; Olson, Peter
2014-01-01
We present experiments on the instability and fragmentation of volumes of heavier liquid released into lighter immiscible liquids. We focus on the regime defined by small Ohnesorge numbers, density ratios of order one, and variable Weber numbers. The observed stages in the fragmentation process include deformation of the released fluid by either Rayleigh-Taylor instability or vortex ring roll-up and destabilization, formation of filamentary structures, capillary instability, and drop formation. At low and intermediate Weber numbers, a wide variety of fragmentation regimes is identified. Those regimes depend on early deformations, which mainly result from a competition between the growth of Rayleigh-Taylor instabilities and the roll-up of a vortex ring. At high Weber numbers, turbulent vortex ring formation is observed. We have adapted the standard theory of turbulent entrainment to buoyant vortex rings with initial momentum. We find consistency between this theory and our experiments, indicating that the conc...
Effect of Side Wind on the Directional Stability and Aerodynamics of a Hybrid Buoyant Aircraft
Directory of Open Access Journals (Sweden)
Haque Anwar U
2016-01-01
Full Text Available Directional stability characteristics explain the capabilities of a hybrid buoyant aircraft’s performance against the side wind, which induces flow separation that is chaotic in nature and may lead to oscillations of the aerodynamic surfaces. A numerical study is carried out to estimate the effect of side wind. The boundary conditions for the computational domain are set to velocity inlet and pressure outlet. Due to the incompressible flow at the cruise velocity, the density is taken to be constant. For these steady state simulations, the time is discretized in first order implicit and the SIMPLE scheme is employed for pressure velocity coupling alongwith k-ω SST model. Based on the results obtained so far, it is concluded that voluminous hybrid lifting fuselage is the major cause of directional.
Ion-water wires in imidazolium-based ionic liquid/water solutions induce unique trends in density.
Ghoshdastidar, Debostuti; Senapati, Sanjib
2016-03-28
Ionic liquid/water binary mixtures are rapidly gaining popularity as solvents for dissolution of cellulose, nucleobases, and other poorly water-soluble biomolecules. Hence, several studies have focused on measuring the thermophysical properties of these versatile mixtures. Among these, 1-ethyl-3-methylimidazolium ([emim]) cation-based ILs containing different anions exhibit unique density behaviours upon addition of water. While [emim][acetate]/water binary mixtures display an unusual rise in density with the addition of low-to-moderate amounts of water, those containing the [trifluoroacetate] ([Tfa]) anion display a sluggish decrease in density. The density of [emim][tetrafluoroborate] ([emim][BF4])/water mixtures, on the other hand, declines rapidly in close accordance with the experimental reports. Here, we unravel the structural basis underlying this unique density behavior of [emim]-based IL/water mixtures using all-atom molecular dynamics (MD) simulations. The results revealed that the distinct nature of anion-water hydrogen bonded networks in the three systems was a key in modulating the observed unique density behaviour. Vast expanses of uninterrupted anion-water-anion H-bonded stretches, denoted here as anion-water wires, induced significant structuring in [emim][Ac]/water mixtures that resulted in the density rise. Conversely, the presence of intermittent large water clusters disintegrated the anion-water wires in [emim][Tfa]/water and [emim][BF4]/water mixtures to cause a monotonic density decrease. The differential nanostructuring affected the dynamics of the solutions proportionately, with the H-bond making and breaking dynamics found to be greatly retarded in [emim][Ac]/water mixtures, while it exhibited a faster relaxation in the other two binary solutions. PMID:26911708
Experimental insights on the development of buoyant plumes injected into a porous media
Lyu, Xiaoying; Woods, Andrew W.
2016-01-01
We describe a series of new laboratory experiments which examine the rise of a two-dimensional buoyancy-driven plume of freshwater through a porous layer initially saturated with aqueous saline solution. Measurements show that the plume head accounts for a constant fraction of about 0.7 of the buoyancy supplied at the source and that it grows as it rises through the porous layer. However, the morphology of the plume head becomes increasingly complex as the ratio of the injection speed to the buoyancy rise speed increases, with the fluid spreading laterally and developing localized buoyant fingers which intermingle with the ambient fluid. Behind the plume head, a tail of nearly constant width develops providing a pathway from the source to the plume head. These starting plume dynamics may be relevant for buoyancy-driven contaminant dispersal and also for the convection which develops during CO2 sequestration as CO2 dissolves into aquifer water.
Magnetic Cycles and Buoyant Loops in Convective Dynamos
Nelson, Nicholas J.
2013-01-01
Solar-type stars display a rich spectrum of magnetic activity. Seeking to explore convective dynamo action in solar-like stars with the anelastic spherical harmonic (ASH) code, we have carried out a series of global 3-D MHD simulations. Here we report on the dynamo mechanisms realized in a series of numerical models of a sun-like star which explore the effects of decreasing diffusion. While these models nominally rotate at three times the current solar rate (3Ω), the results may be more widely applicable as both these simulations and the solar convection zone achieve similar levels of rotationally constrained convection. Previous simulations at 3Ω have shown that convective dynamos can build persistent wreath-like structures of strong toroidal magnetic field in the convection zone (Brown et al. 2010). Here we find that magnetic reversals and cycles can be realized at 3Ω by decreasing the explicit diffusion and thereby making the resolved flows more turbulent. In these more turbulent models, diffusive processes no longer play a primary role in the key dynamical balances which maintain differential rotation and generate the global-scale wreaths. With reduced resistive diffusion of magnetic fields, the axisymmetric poloidal fields can no longer achieve a steady state and this triggers reversals in global magnetic polarity. Additionally, the enhanced levels of turbulence lead to greater intermittency in the toroidal magnetic wreaths, which can create buoyant magnetic loops that rise from the deep interior to the upper regions of our simulated domain. Turbulence-enabled magnetic buoyancy in our most turbulent simulation yields large numbers of buoyant loops, enabling us to examine the distribution of the characteristics of buoyant magnetic loops, such as twist, tilt angle, and relation to axisymmetric fields. These models provide a pathway towards linking convective dynamo models and the emergence of magnetic flux in the Sun and sun-like stars.
Densities of L-Glutamic Acid HCl Drug in Aqueous NaCl and KCl Solutions at Different Temperatures
Ryshetti, Suresh; Raghuram, Noothi; Rani, Emmadi Jayanthi; Tangeda, Savitha Jyostna
2016-04-01
Densities (ρ ) of (0.01 to 0.07) {mol}{\\cdot } {kg}^{-1} L-Glutamic acid HCl (L-HCl) drug in water, and in aqueous NaCl and KCl (0.5 and 1.0) {mol}{\\cdot } {kg}^{-1} solutions have been reported as a function of temperature at T = (298.15, 303.15, 308.15, and 313.15) K and atmospheric pressure. The accurate density (ρ ) values are used to estimate the various parameters such as the apparent molar volume (V_{2,{\\upphi }}), the partial molar volume (V2^{∞}), the isobaric thermal expansion coefficient (α 2), the partial molar expansion (E2^{∞}), and Hepler's constant (partial 2V2^{∞}/partial T2)P. The Cosphere overlap model is used to understand the solute-solvent interactions in a ternary mixture (L-HCl drug + NaCl or KCl + water). Hepler's constant (partial 2V2^{∞}/partial T2)_P is utilized to interpret the structure-making or -breaking ability of L-HCl drug in aqueous NaCl and KCl solutions, and the results are inferred that L-HCl drug acts as a structure maker, i.e., kosmotrope in aqueous NaCl solutions and performs as a structure breaker, i.e., chaotrope in aqueous KCl solutions.
Iasiello, Marcello; Vafai, Kambiz; Andreozzi, Assunta; Bianco, Nicola
2016-01-25
An analytical solution for Low-Density Lipoprotein transport through an arterial wall under hyperthermia conditions is established in this work. A four-layer model is used to characterize the arterial wall. Transport governing equations are obtained as a combination between Staverman-Kedem-Katchalsky membrane equations and volume-averaged porous media equations. Temperature and solute transport fields are coupled by means of Ludwig-Soret effect. Results are in excellent agreement with numerical and analytical literature data under isothermal conditions, and with numerical literature data for the hyperthermia case. Effects of hypertension combined with hyperthermia, are also analyzed in this work. PMID:26806687
Energy Technology Data Exchange (ETDEWEB)
Teodorescu, Razvan [Los Alamos National Laboratory; Lee, S - Y [MONTREAL, CANADA; Wiegmann, P [UNIV OF CHICAGO
2008-01-01
We investigate the hydrodynamics of a Hele-Shaw flow as the free boundary evolves from smooth initial conditions into a generic cusp singularity (of local geometry type x{sup 3} {approx} y{sup 2}), and then into a density shock wave. This novel solution preserves the integrability of the dynamics and, unlike all the weak solutions proposed previously, is not underdetermined. The evolution of the shock is such that the net vorticity remains zero, as before the critical time, and the shock can be interpreted as a singular line distribution of fluid deficit.
Dynamics of finite size neutrally buoyant particles in isotropic turbulence
Energy Technology Data Exchange (ETDEWEB)
Elhimer, M; Jean, A; Praud, O; Bazile, R; Marchal, M; Couteau, G, E-mail: elhimer@imft.fr [Universite de Toulouse, INPT, UPS, IMFT - Institut de Mecanique des Fluides de Toulouse, Allee Camille Soula, F-31400 Toulouse (France); CNRS, IMFT, F-31400 Toulouse (France)
2011-12-22
The dynamics of neutrally buoyant particles suspended in a turbulent flow is investigated experimentally, with particles having diameters larger than the Kolmogorov length scale. To that purpose, a turbulence generator have been constructed and the resulting flow characterized. The fluid was then seeded with polystyrene particles of diameter about 1 mm and their velocity measured separately and simultaneously with the surrounding fluid. Comparison of the velocities statistics between the two phases shows no appreciable discrepancy. However, simultaneous velocity measurement shows that particles may move in different direction from the underlying flow.
Self-concentrating buoyant glass microbubbles for high sensitivity immunoassays.
Juang, Duane S; Hsu, Chia-Hsien
2016-02-01
Here, we report the novel application of a material with self-concentrating properties for enhancing the sensitivity of immunoassays. Termed as glass microbubbles, they are antibody functionalized buoyant hollow glass microspheres that simultaneously float and concentrate into a dense monolayer when dispensed in a liquid droplet. This self-concentrating charactaristic of the microbubbles allow for autonomous signal localization, which translates to a higher sensitivity compared to other microparticle-based immunoassays. We then demonstrated a "microbubble array" platform consisting of the glass microbubbles floating in a microfluidic liquid hemisphere array for performing multiplex immunoassays. PMID:26620967
Buoyant triacylglycerol-filled green algae and methods therefor
Energy Technology Data Exchange (ETDEWEB)
Goodenough, Ursula; Goodson, Carrie
2015-04-14
Cultures of Chlamydomonas are disclosed comprising greater than 340 mg/l triacylglycerols (TAG). The cultures can include buoyant Chlamydomonas. Methods of forming the cultures are also disclosed. In some embodiments, these methods comprise providing Chlamydomonas growing in log phase in a first culture medium comprising a nitrogen source and acetate, replacing the first culture medium with a second medium comprising acetate but no nitrogen source, and subsequently supplementing the second medium with additional acetate. In some embodiments, a culture can comprise at least 1,300 mg/l triacyglycerols. In some embodiments, cultures can be used to produce a biofuel such as biodiesel.
Entrainment and mixing in vertical buoyant light-gas plumes
International Nuclear Information System (INIS)
A simple model is developed to determine the entrainment coefficient and the spread of a light-gas plume in a quiescent atmosphere. Experiments performed with low-velocity saltwater/freshwater and helium-in-air jets indicate that buoyant gas plumes spread significantly faster than thermal plumes. The calculated effluent concentrations are in excellent agreement with those measured when an entrainment coefficient of 0.15 is used in the plume equations. This is significantly higher than the entrainment coefficients of 0.075 to 0.093 reported for thermal plumes
International Nuclear Information System (INIS)
A study has been made of anodic dissolution of rhenium using potentiodynamic dissolution curves for a rotating disk electrode made of vacuum-melted rhenium. Dissolution of rhenium at 23 deg starts at potentials of approximately + 0.2 V for alkaline solutions (NaOH) and at potentials of approximately +0.1 V for neutral solutions (2N NaCl and NaNO3). No limitation of the process rate is observed during dissolution in neutral solutions unlike dissolution in alkalies for which a limiting current strength is characteristic
Luo, Tao; Xin, Zhouping; Zeng, Huihui
2015-01-01
The nonlinear asymptotic stability of Lane-Emden solutions is proved in this paper for spherically symmetric motions of viscous gaseous stars with the density dependent shear and bulk viscosities which vanish at the vacuum, when the adiabatic exponent $\\gamma$ lies in the stability regime $(4/3, 2)$, by establishing the global-in-time regularity uniformly up to the vacuum boundary for the vacuum free boundary problem of the compressible Navier-Stokes-Poisson systems with spherical symmetry, w...
Evolution of the buoyant bubbles in M87
Churazov, E; Kaiser, C R; Böhringer, H; Forman, W R
2000-01-01
The morphology of the X-ray and radio emitting features in the central 50 kpc region around the galaxy M87 strongly suggests that buoyant bubbles of cosmic rays (inflated by an earlier nuclear active phase of the galaxy) are slowly rising through the cooling gas. In the absence of strong surface tension, an intrinsic property of initially spherical bubbles is their transformation into tori as they rise through an external medium. Such structures can be identified in the radio images of the halo of M87. During their rise the bubbles uplift relatively cool X-ray emitting ambient gas from the central regions of the cooling flow to larger distances. This gas is colder than the ambient gas and has a higher volume emissivity. As a result, rising "radio" bubbles may be trailed by elongated X-ray features as indeed is observed in M87. We performed simple hydrodynamical simulations in order to qualitatively illustrate the evolution of the buoyant bubbles in the M87 environment.
Steady thermocapillary-buoyant convection in a shallow annular pool.Part 2: Two immiscible fluids
Institute of Scientific and Technical Information of China (English)
You-Rong Li; Shuang-Cheng Wang; Chun-Mei Wu
2011-01-01
This work is devoted to the study of steady thermocapillary-buoyant convection in a system of two horizontal superimposed immiscible liquid layers filling a lateral heated thin annular pool.The governing equations are solved using an asymptotic theory for the aspect ratios e → 0.Asymptotic solutions of the velocity and temperature fields are obtained in the core region away from the cylinder walls.In order to validate the asymptotic solutions,numerical simulations are also carried out and the results are compared to each other.It is found that the present asymptotic solutions are valid in most of the core region.And the applicability of the obtained asymptotic solutions decreases with the increase of the aspect ratio and the thickness ratio of the two layers.For a system of gallium arsenide (lower layer) and boron oxide (upper layer),the buoyancy slightly weakens the thermocapillary convection in the upper layer and strengthens it in the lower layer.
Sebestíková, L
2013-09-01
Buoyantly unstable 3D chemical fronts were seen traveling through an iodate-arsenous acid reaction solution. The experiments were performed in channel reactors with rectangular cross sections, where the top of the reaction solution was in contact with air. A concave or convex meniscus was pinned to reactor lateral walls. Influence of the meniscus shape on front development was investigated. For the concave meniscus, an asymptotic shape of fronts holding negative curvature was observed. On the other hand, fronts propagating in the solution with the convex meniscus kept only positive curvature. Those fronts were also a bit faster than fronts propagating in the solution with the concave meniscus. A relation between the meniscus shape, flow distribution, velocity, and shape is discussed. PMID:24125360
Non-Boussinesq turbulent buoyant jet resulting from hydrogen leakage in air
Energy Technology Data Exchange (ETDEWEB)
El-Amin, M.F. [Department of Mechanical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)
2009-09-15
This paper is devoted to introduce a numerical investigation of a vertical axisymmetric non-Boussinesq buoyant jet resulting from hydrogen leakage in air as an example of injecting a low-density gas jet into high-density ambient. As the domain temperature is assumed to be constant and therefore the density of the mixture is a function of the concentration only, the binary gas mixture is assumed to be of a linear mixing type. Also, it is assumed that the rate of entrainment to be a function of the plume centerline velocity and the ratio of the mean plume and ambient densities. On the other hand, the local rate of entrainment may be considered to be consisted from two components; one is the component of entrainment due to jet momentum while the other is the component of entrainment due to buoyancy. Firstly, the integral models of the mass, momentum and concentration fluxes are obtained and transformed to a set of ordinary differential equations using some non-dimensional transformations known as similarity transformations. The given ordinary differential system is integrated numerically and the mean centerline mass fraction, jet width and mean centerline velocity are obtained. In the second step, the mean axial velocity, mean concentration and mean density of the jet are obtained. Finally in the third step of this article, several quantities of interest, including the cross-stream velocity, Reynolds stress, velocity-concentration correlation (radial flux), turbulent eddy viscosity and turbulent eddy diffusivity, are obtained. In addition, the turbulent Schmidt number is estimated and the normalized jet-feed material density and the normalized momentum flux density are correlated. (author)
46 CFR 131.865 - Inflatable liferafts and inflatable buoyant apparatus.
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Inflatable liferafts and inflatable buoyant apparatus. 131.865 Section 131.865 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.865 Inflatable liferafts and inflatable buoyant apparatus....
46 CFR 160.010-4 - General requirements for buoyant apparatus.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false General requirements for buoyant apparatus. 160.010-4 Section 160.010-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Buoyant Apparatus for Merchant Vessels § 160.010-4 General requirements...
International Nuclear Information System (INIS)
A series of approximations are usually made in deriving integral model equations for the dispersion of a round turbulent buoyant jet into a stagnant neutrally-stratified ambient fluid. The magnitudes of differences in model predictions caused by making four of these approximations are calculated as a function of the initial densimetric Froude number and the initial relative density difference. The four approximations studied are (1) the Boussinesq approximation, (2) the use of a common Gaussian width for both mean axial velocity and mean temperature (or concentration) excess, (3) the neglect of fluctuation-correlation terms, and (4) the assumption of a linear relationship between excess density and excess temperature (or concentration). The four approximations are studied singly and then cumulatively as the predictions of the two models, one with and one without all approximations, are compared to seven low Froude number data cases. Results show that the Boussinesq approximation produces percentage differences in predictions which are about half of the initial relative density difference expressed in percentage. Use of a common Gaussian width for velocity and temperature produces differences from 6% to 30% depending on the entrainment assumption used. Fluctuation correlation effects rarely exceed 8%. Lastly, at Froude numbers below about 10 the correct nonlinear equation of state must often be used for heated waste jets to acheive accurate results, and the correct air equation of state may also be needed for low Froude number heated air jets, depending on the initial diameter and velocity
Optimal unambiguous state discrimination of two density matrices: A second class of exact solutions
L"utkenhaus, P R N
2007-01-01
We consider the Unambiguous State Discrimination (USD) of two mixed quantum states. We study the rank and the spectrum of the elements of an optimal USD measurement. This naturally leads to a partial fourth reduction theorem. This theorem shows that either the failure probability equals its overall lower bound given in term of the fidelity or a two dimensional subspace can be split off from the original Hilbert space. We then use this partial reduction theorem to derive the optimal solution for any two Geometrically Uniform (GU) states $\\rho_0$ and $\\rho_1=U\\rho_0 U^\\dagger$, $U^2={\\openone}$, in a four dimensional Hilbert space. This represents a second class of analytical solutions for USD problems that cannot be reduced to some pure state cases. We apply our result to answer two questions that are relevant in implementations of the Bennett and Brassard 1984 quantum key distribution protocol using weak coherent states.
Turbulent buoyant confined jet with variable source temperature
El-Amin, M F; Sun, S
2013-01-01
In this work, experimental and numerical investigations are considered for confined buoyant turbulent jet with varying inlet temperatures. Results of the experimental work and numerical simulations for the problem under consideration are presented. Four cases of different variable inlet temperatures and different flow rates are considered. The realizable k-epsilon turbulence model is used to model the turbulent flow. Comparisons show good agreements between simulated and measured results. The results indicate that temperatures along the vertical axis vary, generally, in nonlinear fashion as opposed to the approximately linear variation that was observed for the constant inlet temperature that was done in a previous work. Furthermore, thermal stratification exits particularly closer to the entrance region. Further away from the entrance region the variation in temperatures becomes relatively smaller. The stratification is observed since the start of the experiment and continues during whole time. Numerical exp...
Flow behaviour of negatively buoyant jets in immiscible ambient fluid
Energy Technology Data Exchange (ETDEWEB)
Geyer, A. [CIMNE International Center for Numerical Models in Engineering, Barcelona (Spain); CSIC, Institute of Earth Sciences Jaume Almera, Barcelona (Spain); Phillips, J.C. [University of Bristol, Department of Earth Sciences, Bristol (United Kingdom); Mier-Torrecilla, M.; Idelsohn, S.R.; Onate, E. [CIMNE International Center for Numerical Models in Engineering, Barcelona (Spain)
2012-01-15
In this paper we investigate experimentally the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid. Experiments are carried out by injecting a jet of dyed fresh water through a nozzle in the base of a cylindrical tank containing rapeseed oil. The fountain inlet flow rate and nozzle diameter were varied to cover a wide range of Richardson Ri (8 x 10{sup -4}
Numerical simulations of buoyant reactive jets with sidewall effects
Institute of Scientific and Technical Information of China (English)
ZHANG Heping; JIANG Xi; WANG Wei; YANG Yun; XU Liang; FAN Weicheng
2004-01-01
The near field dynamics of buoyant reactive jets with adjacent sidewalls is investigated by time-dependent three-dimensional direct simulations. The physical problem is a fuel jet issuing vertically into an oxidant ambient environment in a corner configuration with sidewall boundaries. Simulation results are presented for two cases with different jet nozzle geometries: a corner-round reactive jet and a corner-square reactive jet with the same cross-sectional area on the nozzle plane. Buoyancy-induced large vortical structures evolve spatially in the flow field and transition to turbulence occurs downstream. Calculation of the mean flow properties shows that entrainment of the corner-round jet is stronger than that of the corner-square jet due to the stronger vortex deformation in the corner-round case.
NATO Advanced Study Institute on Buoyant Convection in Geophysical Flows
Fedorovich, E; Viegas, D; Wyngaard, J
1998-01-01
Studies of convection in geophysical flows constitute an advanced and rapidly developing area of research that is relevant to problems of the natural environment. During the last decade, significant progress has been achieved in the field as a result of both experimental studies and numerical modelling. This led to the principal revision of the widely held view on buoyancy-driven turbulent flows comprising an organised mean component with superimposed chaotic turbulence. An intermediate type of motion, represented by coherent structures, has been found to play a key role in geophysical boundary layers and in larger scale atmospheric and hydrospheric circulations driven by buoyant forcing. New aspects of the interaction between convective motions and rotation have recently been discovered and investigated. Extensive experimental data have also been collected on the role of convection in cloud dynamics and microphysics. New theoretical concepts and approaches have been outlined regarding scaling and parameteriz...
Sampling and analysis of particles from buoyant hydrothermal plumes
Mottl, Michael J.
The objective of our studies has been to identify the chemical processes that occur in the buoyant part of hydrothermal plumes and to evaluate their role in determining the ultimate fate of the hydrothermal input to the oceans. Our first such effort is described by Mottl and McConachy [1990]. Because the buoyant plume is a small feature that contains very large physical and chemical gradients, we have sampled it from manned submersibles. We have used two different samplers, both manufactured by General Oceanics in Miami: the Go-Flo bottle and the Chopstick sampler. Four Go-Flo bottles of 1.7 L capacity can readily be mounted on most submersibles, vertically and in a forward position in sight of the pilot's viewport and video cameras, without interfering with other operations on a dive. On Alvin they have typically been mounted on the outside starboard edge of the basket. On Turtle they were mounted on the outside edge of the port manipulator. We chose Go-Flo rather than Niskin bottles because the latter are prone to spillage when the rods attached to the end caps are bumped against an object such as the seafloor, as often happens on a submersible dive. Go-Flo bottles are also more easily rigged for pressure filtration than are Niskins. The main disadvantage of Go-Flo bottles vs. Niskins for this application is the internal silicone rubber ring that holds the ball valves in place on each end of the Go-Flo. This ring tends to trap large particles that are then difficult to dislodge and collect. The rings are also difficult to clean between dives.
International Nuclear Information System (INIS)
A mechanism capable to provide a natural solution to two major cosmological problems, i.e. the cosmic acceleration and the coincidence problem, is proposed. A specific brane-bulk energy exchange mechanism produces a total dark pressure, arising when adding all normal to the brane negative pressures in the interior of galactic core black holes. This astrophysically produced negative dark pressure explains cosmic acceleration and why the dark energy today is of the same order to the matter density for a wide range of the involved parameters. An exciting result of the analysis is that the recent rise of the galactic core black hole mass density causes the recent passage from cosmic deceleration to acceleration. Finally, it is worth mentioning that this work corrects a wide spread fallacy among brane cosmologists, i.e. that escaping gravitons result in positive dark pressure. (orig.)
International Nuclear Information System (INIS)
Highlights: ► Density of amino acid salt and amine amino acid salt. ► Viscosity of amino acid salt and amine amino acid salt. ► Henry’s law constant/N2O solubility of amino acid salt and amine amino acid salt. ► Schumpe model. Correlations for density, viscosity, and N2O solubility. - Abstract: Physicochemical properties of aqueous amino acid salt (AAS), potassium salt of sarcosine (KSAR) and aqueous amine amino acid salt (AAAS), 3-(methylamino)propylamine/sarcosine (SARMAPA) have been studied. Densities of KSAR were measured for sarcosine mole fraction 0.02 to 0.25 for temperature range 298.15 K to 353.15 K, the viscosities were measured for 0.02 to 0.10 mole fraction sarcosine (293.15 K to 343.15 K) while the N2O solubilities were measured from 0.02 to 0.10 mole fraction sarcosine solutions (298.15 K to 363.15 K). Densities of SARMAPA were measured for sarcosine mole fraction 0.02 to 0.23 for temperature range (298.15 K to 353.15 K), viscosities were measured for 0.02 to 0.16 mole fraction sarcosine (293.15 K to 343.15 K) while the N2O solubilities were measured from 0.02 to 0.16 mole fraction sarcosine solutions (298.15 K to 343.15 K). Experimental results were correlated well with empirical correlations and N2O solubility results for KSAR were predicted adequately by a Schumpe model. The solubilities of N2O in AAS and AAAS are significantly lower than values for amines. The solubilities vary as: amine > AAAS > AAS.
Energy Technology Data Exchange (ETDEWEB)
Tiilikainen, J; Bosund, V; Mattila, M; Hakkarainen, T; Sormunen, J; Lipsanen, H [Micro and Nanosciences Laboratory, Helsinki University of Technology, Micronova, PO Box 3500, FI-02015 TKK (Finland)
2007-07-21
Nonunique solutions of the x-ray reflectivity (XRR) curve fitting problem were studied by modelling layer structures with neural networks and designing a fitness function to handle the nonidealities of measurements. Modelled atomic-layer-deposited aluminium oxide film structures were used in the simulations to calculate XRR curves based on Parratt's formalism. This approach reduced the dimensionality of the parameter space and allowed the use of fitness landscapes in the study of nonunique solutions. Fitness landscapes, where the height in a map represents the fitness value as a function of the process parameters, revealed tracks where the local fitness optima lie. The tracks were projected on the physical parameter space thus allowing the construction of the crosserror equation between weakly determined parameters, i.e. between the mass density and the surface roughness of a layer. The equation gives the minimum error for the other parameters which is a consequence of the nonuniqueness of the solution if noise is present. Furthermore, the existence of a possible unique solution in a certain parameter range was found to be dependent on the layer thickness and the signal-to-noise ratio.
International Nuclear Information System (INIS)
Nonunique solutions of the x-ray reflectivity (XRR) curve fitting problem were studied by modelling layer structures with neural networks and designing a fitness function to handle the nonidealities of measurements. Modelled atomic-layer-deposited aluminium oxide film structures were used in the simulations to calculate XRR curves based on Parratt's formalism. This approach reduced the dimensionality of the parameter space and allowed the use of fitness landscapes in the study of nonunique solutions. Fitness landscapes, where the height in a map represents the fitness value as a function of the process parameters, revealed tracks where the local fitness optima lie. The tracks were projected on the physical parameter space thus allowing the construction of the crosserror equation between weakly determined parameters, i.e. between the mass density and the surface roughness of a layer. The equation gives the minimum error for the other parameters which is a consequence of the nonuniqueness of the solution if noise is present. Furthermore, the existence of a possible unique solution in a certain parameter range was found to be dependent on the layer thickness and the signal-to-noise ratio
The study on density change of carbon dioxide seawater solution at high pressure and low temperature
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It has been widely considered that the global warming, induced by the increasing concentration of carbon dioxide and other greenhouse gases in the atmosphere, is an environmental task affecting the world economic development. In order to mitigate the concentration of CO2 in the atmosphere, the sequestration of carbon dioxide into the ocean had been investigated theoretically and experimentally over the last 10 years. In addition to ocean dynamics, ocean geological, and biological information on large space and long time scales, the physical-chemistry properties of seawater-carbon dioxide system at high pressure (P>5.0 MPa) and lower temperature (274.15 K3, which is approximately same with that of carbon dioxide freshwater solution, the slope of which is 0.275 g/cm3
International Nuclear Information System (INIS)
The investigation of the scattering of lower-hybrid waves by density fluctuations arising from drift waves in tokamaks is distinguished by the presence in the wave equation of a large, random, derivative-coupling term. The propagation of the lower-hybrid waves is well represented by a radiative transfer equation when the scale size of the density fluctuations is small compared to the overall plasma size. The radiative transfer equation is solved in two limits: first, the forward scattering limit, where the scale size of density fluctuations is large compared to the lower-hybrid perpendicular wavelength, and second, the large-angle scattering limit, where this inequality is reversed. The most important features of these solutions are well represented by analytical formulas derived by simple arguments. Based on conventional estimates for density fluctuations arising from drift waves and a parabolic density profile, the optical depth tau for scattering through a significant angle, is given by tauroughly-equal(2/N2/sub parallel/) (#betta#/sub p/i0/#betta#)2 (m/sub e/c2/2T/sub i/)/sup 1/2/ [c/α(Ω/sub i/Ω/sub e/)/sup 1/2/ ], where #betta#/sub p/i0 is the central ion plasma frequency and T/sub i/ denotes the ion temperature near the edge of the plasma. Most of the scattering occurs near the surface. The transmission through the scattering region scales as tau-1 and the emerging intensity has an angular spectrum proportional to cos theta, where sin theta = k/sub perpendicular/xB/sub p//(k/sub perpendicular/B/sub p/), and B/sub p/ is the poloidal field
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Studies of a roll-front uranium deposit in Shirley Basin Wyoming indicate that preliminary evaluation of the reserve potential of an ore body is possible with less drilling than currently practiced in industry. Estimating ore reserves from sparse drilling is difficult because most reserve calculation techniques do not give the accuracy of the estimate. A study of several deposits with a variety of drilling densities shows that geostatistics consistently provides a method of assessing the accuracy of an ore reserve estimate. Geostatistics provides the geologist with an additional descriptive technique - one which is valuable in the economic assessment of a uranium deposit. Closely spaced drilling on past properties provides both geological and geometric insight into the occurrence of uranium in roll-front type deposits. Just as the geological insight assists in locating new ore bodies and siting preferential drill locations, the geometric insight can be applied mathematically to evaluate the accuracy of a new ore reserve estimate. By expressing the geometry in numerical terms, geostatistics extracts important geological characteristics and uses this information to aid in describing the unknown characteristics of a property. (author)
Dutta, Urmi; Baruah, Amiya; Mandal, Nibir
2016-04-01
Diapiric structure owing to gravity instabilities, triggered by density inversion in the rock sequences, is a unique geodynamic manifestation. High-density layers that rest upon low-density layers tend to sink, forcing the latter to squeeze up in the form of domal shapes, called buoyant diapirs. Using two-layer viscous model experiments, we investigated the effects of source-layer tilt (β) in controlling the ascent behaviour of buoyant diapirs initiated by a Rayleigh-Taylor instability. Results from our laboratory experiments, performed with a buoyant viscous layer (PDMS; density: 965.0 kg/m3) underlying a denser fluid (water; density: 998.2 kg/m3) suggest that the diapir shape is highly sensitive to β. The results suggest that diapirs growing from a tilted source layer ascend with contrasting lateral spreading rates in the up and down slope directions, resulting in axi-asymmetric geometry. Conversely, diapirs initiated from a horizontal source layer always maintain axi- symmetric shape as they grow. Interestingly, diapir heads retain a circular outline on the horizontal top surface irrespective of their degree of symmetry. However, for the axi-asymmetric cases, the upwelling axis is shifted more in the up-slope direction, i.e. away from the centre of this circular geometry. We show a spectrum of the axi-symmetric to -asymmetric geometrical transitions as a function of the source-layer tilt (β). For large β (> 4o), the diapirs become unstable, and their stems undergo a continuous drift in the upslope direction during their vertical growth. Whilst, several studies have shown the development of axi-asymmetric diapirs, the underlain flow kinematics in the viscous layers as a function of source layer tilt leading to such shape transition remains unclear. With this objective we ran computational fluid dynamic (CFD) simulations, by employing the volume of fluid (VOF) method, to investigate the role of underlying dynamics for axi-asymmetric diapiric growth. This study
Energy density of marine pelagic fish eggs
DEFF Research Database (Denmark)
Riis-Vestergaard, J.
2002-01-01
Analysis of the literature on pelagic fish eggs enabled generalizations to be made of their energy densities, because the property of being buoyant in sea water appears to constrain the proximate composition of the eggs and thus to minimize interspecific variation. An energy density of 1.34 J mul...
Shapes of Buoyant and Nonbuoyant Methane Laminar Jet Diffusion Flames
Sunderland, Peter B.; Yuan, Zeng-Guang; Urban, David L.
1997-01-01
Laminar gas jet diffusion flames represent a fundamental combustion configuration. Their study has contributed to numerous advances in combustion, including the development of analytical and computational combustion tools. Laminar jet flames are pertinent also to turbulent flames by use of the laminar flamelet concept. Investigations into the shapes of noncoflowing microgravity laminar jet diffusion flames have primarily been pursued in the NASA Lewis 2.2-second drop tower, by Cochran and coworkers and by Bahadori and coworkers. These studies were generally conducted at atmospheric pressure; they involved soot-containing flames and reported luminosity lengths and widths instead of the flame-sheet dimensions which are of Greater value to theory evaluation and development. The seminal model of laminar diffusion flames is that of Burke and Schumann, who solved the conservation of momentum equation for a jet flame in a coflowing ambient by assuming the velocity of fuel, oxidizer and products to be constant throughout. Roper and coworkers improved upon this model by allowing for axial variations of velocity and found flame shape to be independent of coflow velocity. Roper's suggestion that flame height should be independent of gravity level is not supported by past or present observations. Other models have been presented by Klajn and Oppenheim, Markstein and De Ris, Villermaux and Durox, and Li et al. The common result of all these models (except in the buoyant regime) is that flame height is proportional to fuel mass flowrate, with flame width proving much more difficult to predict. Most existing flame models have been compared with shapes of flames containing soot, which is known to obscure the weak blue emission of flame sheets. The present work involves measurements of laminar gas jet diffusion flame shapes. Flame images have been obtained for buoyant and nonbuoyant methane flames burning in quiescent air at various fuel flow-rates, burner diameters and ambient
Factors affecting the density of Brassica napus seeds
Young, L.; Jalink, H.; Denkert, R.; Reaney , M
2006-01-01
Brassica napus seed is composed of low density oil (0.92 g.cm(-3)) and higher density solids (1.3-1.45 g.cm(-3)). Seed buoyant density may potentially be used to determine seed oil content and to separate seeds with different oil contents, however, we have found that seeds with the lowest buoyant density had lower than expected oil contents. It is proposed that the low oil content observed in the lowest density seed is a function of air gaps or pockets within the seed coat with sufficient vol...
Highly buoyant bent-over plumes in a boundary layer
Tohidi, Ali; Kaye, Nigel B.
2016-04-01
Highly buoyant plumes, such as wildfire plumes, in low to moderate wind speeds have initial trajectories that are steeper than many industrial waste plumes. They will rise further into the atmosphere before bending significantly. In such cases the plume's trajectory will be influenced by the vertical variation in horizontal velocity of the atmospheric boundary layer. This paper examined the behavior of a plume in an unstratified environment with a power-law ambient velocity profile. Examination of previously published experimental measurements of plume trajectory show that inclusion of the boundary layer velocity profile in the plume model often provides better predictions of the plume trajectory compared to algebraic expressions developed for uniform flow plumes. However, there are many cases in which uniform velocity profile algebraic expressions are as good as boundary layer models. It is shown that it is only important to model the role of the atmospheric boundary layer velocity profile in cases where either the momentum length (square root of source momentum flux divided by the reference wind speed) or buoyancy length (buoyancy flux divided by the reference wind speed cubed) is significantly greater than the plume release height within the boundary layer. This criteria is rarely met with industrial waste plumes, but it is important in modeling wildfire plumes.
Role of buoyant flame dynamics in wildfire spread.
Finney, Mark A; Cohen, Jack D; Forthofer, Jason M; McAllister, Sara S; Gollner, Michael J; Gorham, Daniel J; Saito, Kozo; Akafuah, Nelson K; Adam, Brittany A; English, Justin D
2015-08-11
Large wildfires of increasing frequency and severity threaten local populations and natural resources and contribute carbon emissions into the earth-climate system. Although wildfires have been researched and modeled for decades, no verifiable physical theory of spread is available to form the basis for the precise predictions needed to manage fires more effectively and reduce their environmental, economic, ecological, and climate impacts. Here, we report new experiments conducted at multiple scales that appear to reveal how wildfire spread derives from the tight coupling between flame dynamics induced by buoyancy and fine-particle response to convection. Convective cooling of the fine-sized fuel particles in wildland vegetation is observed to efficiently offset heating by thermal radiation until convective heating by contact with flames and hot gasses occurs. The structure and intermittency of flames that ignite fuel particles were found to correlate with instabilities induced by the strong buoyancy of the flame zone itself. Discovery that ignition in wildfires is critically dependent on nonsteady flame convection governed by buoyant and inertial interaction advances both theory and the physical basis for practical modeling. PMID:26183227
Buoyant dispersal of CO2 during geological storage
Hesse, M. A.; Woods, A. W.
2010-01-01
Carbon capture and storage is currently the only technology that may allow significant reductions in CO2 emissions from large point sources. Seismic images of geological CO2 storage show the rise of CO2 is influenced by horizontal shales. The buoyant CO2 spreads beneath impermeable barriers until a gap allows its upward migration. The large number and small scale of these barriers makes the prediction of the CO2 migration path and hence the magnitude of CO2 trapping very challenging. We show that steady buoyancy dominated flows in complex geometries can be modeled as a cascade of flux partitioning events. This approach allows the analysis of two-dimensional plume dispersal from a horizontal injection well. We show that the plume spreads laterally with height y above the source according to (y/h)1/2 L, where L is the width of the shales and h is their vertical separation. The fluid volume below successive shale layers, and therefore the magnitude of trapped CO2, increase as (y/h)5/4 above the source, so that every additional layer of barriers traps more CO2 than the one below. Upscaling small scale flow barriers by reducing the vertical permeability, common in numerical simulations of CO2 storage, does not capture the dispersion and trapping of the CO2 plume by the flow barriers.
Buoyant Magnetic Flux Ropes and Convection: Evolution Prior to Emergence
Dorch, S. B. F.
2003-10-01
We have performed detailed numerical 3-d simulations of the interaction of buoyantly ascending twisted magnetic flux ropes and solar-like stratified convection (with surface cells similar to solar supergranules in size). Results are presented for three different cases -- corresponding to different amounts of initial field line twist -- that represents fundamentally different types of instabilities: the magnetic Rayleigh-Taylor instability in which case the flux rope disrupts and network patches are formed at surface cell boundaries; the kink instability that has been proposed as a mechanism for forming tightly packed δ-type spots; a stable flux rope where neither of the former instabilities arise, and the behavior of which is similar to classical text book flux tubes, except from a flux-loss due to the advective action of the convective flows. The simulations thus support the idea that the magnetic flux observed at the surface in bipolar regions are smaller, ceteris paribus, than that of the dynamo generated flux ropes near the bottom of the convection zone. Please note that this material is also available as an online htmladdnormallink{web-talk}{http://www.astro.su.se/ dorch/talks/01_CS12/}
The vertical distribution of buoyant plastics at sea
Directory of Open Access Journals (Sweden)
J. Reisser
2014-11-01
Full Text Available Millimeter-sized plastics are numerically abundant and widespread across the world's ocean surface. These buoyant macroscopic particles can be mixed within the upper water column due to turbulent transport. Models indicate that the largest decrease in their concentration occurs within the first few meters of water, where subsurface observations are very scarce. By using a new type of multi-level trawl at 12 sites within the North Atlantic accumulation zone, we measured concentrations and physical properties of plastics from the air–seawater interface to a depth of 5 m, at 0.5 m intervals. Our results show that plastic concentrations drop exponentially with water depth, but decay rates decrease with increasing Beaufort scale. Furthermore, smaller pieces presented lower rise velocities and were more susceptible to vertical transport. This resulted in higher depth decays of plastic mass concentration (mg m−3 than numerical concentration (pieces m−3. Further multi-level sampling of plastics will improve our ability to predict at-sea plastic load, size distribution, drifting pattern, and impact on marine species and habitats.
Entrainment and mixing in vertical buoyant light-gas plumes
International Nuclear Information System (INIS)
Hydrogen has great potential as a future fuel because of its nearly pollution-free combustion. However, it is highly diffusive and can easily leak through joints, cracks and defective valves if care is not taken. Accidental release of hydrogen into surrounding air and its subsequent mixing are of concern in evaluating the safe transport of hydrogen in buildings through piping. Hydrogen release into air is of importance in nuclear reactor safety analysis also. During certain postulated accidents in nuclear reactors, hydrogen may be produced by high temperature metal-steam reactions and released into the containment building. A simple model is developed to determine the entrainment coefficient and the spread of a light-gas plume in a quiescent atmosphere. Experiments performed with low velocity salt water/fresh-water and helium-in-air jets indicate that buoyant gas plumes spread significantly faster than thermal plumes. The calculated effluent concentrations are in excellent agreement with those measured when an entrainment coefficient of 0.15 is used in the plume equations. This is significantly higher than the entrainment coefficients of 0.075 to 0.093 reported for thermal plumes
Baluja, Shipra; Vaishnani, K. P.
2013-08-01
Density, ultrasonic velocity and viscosity of some Schiff bases of 4-aminophenol have been measured in dimethyl sulfoxide solutions over a wide range of concentration at 308.15 K. From these experimental data, some acoustical parameters have been evaluated, which helps in understanding the molecular interactions occurring in these solutions.
NUMERICAL STUDY ON THE STABILITY AND MIXING OF VERTICAL ROUNE BUOYANT JET IN SHALLOW WATER
Institute of Scientific and Technical Information of China (English)
曾玉红; 槐文信
2005-01-01
The k-epsilon model was applied to establish the mathematical model of vertical round buoyant jet discharging into confined depth, and it was solved using the Hybrid Finite Analytic Method ( HFAM ). The numerical predictions demonstrate two generic flow patterns for different jet discharge and environmental parameters: ( i ) a stable buoyant flow discharge with the mixed fluid leaving the near-field warm in a surface warm water layer;( ii ) an unstable buoyant flow discharge with recirculation and re-entrainment of warm water in the near field. Furthermore, the mixing characters of vertical round buoyant jet were numerically predicted. Both the stability criterion and numerical predictions of bulk dilutions are in excellent agreement with Lee and Jirka ' s experiments and theory.
The Melt Segregation During Ascent of Buoyant Diapirs in Subduction Zones
Zhang, N.; Behn, M. D.; Parmentier, E. M.; Kincaid, C. R.
2014-12-01
Cold, low-density diapirs arising from hydrated mantle and/or subducted sediments on the top of subducting slabs may transport key chemical signatures from the slab to the shallow source region for arc magmas. These chemical signatures are strongly influenced by melting of this buoyant material during its ascent. However, to date there have been relatively few quantitative models to constrain melting and melt segregation in an ascending diapir, as well as the induced geochemical signature. Here, we use a two-phase Darcy-Stokes-energy model to investigate thermal evolution, melting, and melt segregation in buoyant diapirs as they ascend through the mantle wedge. Using a simplified 2-D axi-symmetric circular geometry we investigate diapir evolution in three scenarios with increasing complexity. First, we consider a case without melting in which the thermal evolution of the diapir is controlled solely by thermal diffusion during ascent. Our results show that for most cases (e.g., diapir radius ≤ 3.7 km and diapir generation depths of ~ 75 km) thermal diffusion times are smaller than the ascent time—implying that the diapir will thermal equilibrate with the mantle wedge. Secondly, we parameterize melting within the diapir, but without melt segregation, and add the effect of latent heat to the thermal evolution of the diapir. Latent heat significantly buffers heating of the diapir. For the diapir with radius ~3.7 km, the heating from the outside is slowed down ~30%. Finally, we include melt segregation within the diapir in the model. Melting initiates at the boundaries of the diapir as the cold interior warms in response to thermal equilibration with the hot mantle wedge. This forms a high porosity, high permeability rim around the margin of the diapir. As the diapir continues to warm and ascend, new melts migrate into this rim and are focused upward, accumulating at the top of the diapir. The rim thus acts like an annulus melt channel isolating the central part of
Guevara, Carlos; Graf, Thomas
2013-04-01
Subsurface water systems are endangered due to salt water intrusion in coastal aquifers, leachate infiltration from waste disposal sites and salt transport in agricultural sites. This leads to the situation where more dense fluid overlies a less dense fluid creating a density gradient. Under certain conditions this density gradient produces instabilities in form dense plume fingers that move downwards. This free convection increases solute transport over large distances and shorter times. In cases where a significantly larger density gradient exists, the effect of free convection on transport is non-negligible. The assumption of a constant density distribution in space and time is no longer valid. Therefore variable-density flow must be considered. The flow equation and the transport equation govern the numerical modeling of variable-density flow and solute transport. Computer simulation programs mathematically describe variable-density flow using the Oberbeck-Boussinesq Approximation (OBA). Three levels of simplifications can de considered, which are denoted by OB1, OB2 and OB3. OB1 is the usually applied simplification where variable density is taken into account in the hydraulic potential. In OB2 variable density is considered in the flow equation and in OB3 variable density is additionally considered in the transport equation. Using the results from a laboratory-scale experiment of variable-density flow and solute transport (Simmons et al., Transp. Porous Medium, 2002) it is investigated which level of mathematical accuracy is required to represent the physical experiment the most accurate. Differences between the physical and mathematical model are evaluated using qualitative indicators (e.g. mass fluxes, Nusselt number). Results show that OB1 is required for small density gradients and OB3 is required for large density gradients.
Wave-induced mixing and transport of buoyant particles: application to the Statfjord A oil spill
Directory of Open Access Journals (Sweden)
M. Drivdal
2014-12-01
Full Text Available This study focuses on how wave–current and wave–turbulence interactions modify the transport of buoyant particles in the ocean. Here the particles can represent oil droplets, plastic particles, or plankton such as fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM, modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production, as well as the stronger veering by the Coriolis–Stokes force, affects the drift of the particles. The energy and momentum fluxes, as well as the Stokes drift, depend on the directional wave spectrum obtained from a wave model. As a first test, the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (i.e., classical Ekman theory. Secondly, the model is applied to a case in which we investigate the oil drift after an oil spill off the west coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by oil-drift models. In this case, using wind and wave forcing from the ERA Interim archive it is shown that the wave effects are important for the resultant drift and have the potential to improve drift forecasting.
Wave induced mixing and transport of buoyant particles: application to the Statfjord A oil spill
Drivdal, M.; Broström, G.; Christensen, K. H.
2014-05-01
The modelling of wave-current and wave-turbulence interactions have received much attention in recent years. In this study the focus is on how these wave effects modify the transport of particles in the ocean. Here the particles are buoyant tracers that can represent oil droplets, plastic particles or plankton, for example fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production as well as the stronger veering by the Coriolis-Stokes force affect the drift of the particles. The energy and momentum fluxes as well as the Stokes drift depend on the directional wave spectrum that can be obtained from a wave model or from observations. As a first test the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (e.g. classical Ekman theory). Secondly the model is applied to a case where we investigate the oil drift after an offshore oil spill outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by empirical models. With wind and wave forcing from the ERA Interim archive, it is shown that the wave effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.
Wave-induced mixing and transport of buoyant particles: application to the Statfjord A oil spill
Drivdal, M.; Broström, G.; Christensen, K. H.
2014-12-01
This study focuses on how wave-current and wave-turbulence interactions modify the transport of buoyant particles in the ocean. Here the particles can represent oil droplets, plastic particles, or plankton such as fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production, as well as the stronger veering by the Coriolis-Stokes force, affects the drift of the particles. The energy and momentum fluxes, as well as the Stokes drift, depend on the directional wave spectrum obtained from a wave model. As a first test, the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (i.e., classical Ekman theory). Secondly, the model is applied to a case in which we investigate the oil drift after an oil spill off the west coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by oil-drift models. In this case, using wind and wave forcing from the ERA Interim archive it is shown that the wave effects are important for the resultant drift and have the potential to improve drift forecasting.
Wave induced mixing and transport of buoyant particles: application to the Statfjord A oil spill
Directory of Open Access Journals (Sweden)
M. Drivdal
2014-05-01
Full Text Available The modelling of wave-current and wave-turbulence interactions have received much attention in recent years. In this study the focus is on how these wave effects modify the transport of particles in the ocean. Here the particles are buoyant tracers that can represent oil droplets, plastic particles or plankton, for example fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM, modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production as well as the stronger veering by the Coriolis–Stokes force affect the drift of the particles. The energy and momentum fluxes as well as the Stokes drift depend on the directional wave spectrum that can be obtained from a wave model or from observations. As a first test the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (e.g. classical Ekman theory. Secondly the model is applied to a case where we investigate the oil drift after an offshore oil spill outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by empirical models. With wind and wave forcing from the ERA Interim archive, it is shown that the wave effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.
Energy Technology Data Exchange (ETDEWEB)
Blandford, Edward D., E-mail: edb@unm.edu [Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131-0001 (United States); Peterson, Per F. [Department of Nuclear Engineering, University of California, Berkeley, CA 94720-1730 (United States)
2013-09-15
Highlights: • We develop a novel buoyantly-driven shutdown rod concept for a FHR. • Shutdown rod system can be actively or passively activated during transients. • Response of the rod was computationally simulated and experimentally validated. • Initial results indicate rod could provide effective transient reactivity control. -- Abstract: This paper presents a novel buoyantly-driven shutdown rod concept for use in Fluoride salt-cooled High-temperature Reactors (FHRs). The baseline design considered here is a 900 MWth modular version of the FHR class called the Pebble Bed Advanced High-Temperature Reactor (PB-AHTR) that uses pebble fuel. Due to the high volumetric heat capacity of the primary coolant, the FHRs operate with a high power density core with a similar average coolant temperature as in modular helium reactors. The reactivity control system for the baseline PB-AHTR uses a novel buoyantly-driven shutdown rod system that can be actively or passively activated during reactor transients. In addition to a traditional active insertion mechanism, the new shutdown rod system is designed to also operate passively, fulfilling the role of a reserve shutdown system. The physical response of the shutdown rod was simulated both computationally and experimentally, using scaling arguments where applicable, with an emphasis on key phenomena identified by a preliminary Phenomena Identification and Ranking Table (PIRT) study. This paper presents results from both the pre-predicted simulation and experimental validation efforts.
International Nuclear Information System (INIS)
Highlights: • We develop a novel buoyantly-driven shutdown rod concept for a FHR. • Shutdown rod system can be actively or passively activated during transients. • Response of the rod was computationally simulated and experimentally validated. • Initial results indicate rod could provide effective transient reactivity control. -- Abstract: This paper presents a novel buoyantly-driven shutdown rod concept for use in Fluoride salt-cooled High-temperature Reactors (FHRs). The baseline design considered here is a 900 MWth modular version of the FHR class called the Pebble Bed Advanced High-Temperature Reactor (PB-AHTR) that uses pebble fuel. Due to the high volumetric heat capacity of the primary coolant, the FHRs operate with a high power density core with a similar average coolant temperature as in modular helium reactors. The reactivity control system for the baseline PB-AHTR uses a novel buoyantly-driven shutdown rod system that can be actively or passively activated during reactor transients. In addition to a traditional active insertion mechanism, the new shutdown rod system is designed to also operate passively, fulfilling the role of a reserve shutdown system. The physical response of the shutdown rod was simulated both computationally and experimentally, using scaling arguments where applicable, with an emphasis on key phenomena identified by a preliminary Phenomena Identification and Ranking Table (PIRT) study. This paper presents results from both the pre-predicted simulation and experimental validation efforts
Kobayashi, Hirokazu; Kusada, Kohei; Kitagawa, Hiroshi
2015-06-16
Currently 118 known elements are represented in the periodic table. Of these 118 elements, only about 80 elements are stable, nonradioactive, and widely available for our society. From the viewpoint of the "elements strategy", we need to make full use of the 80 elements to bring out their latent ability and create innovative materials. Furthermore, there is a strong demand that the use of rare or toxic elements be reduced or replaced while their important properties are retained. Advanced science and technology could create higher-performance materials even while replacing or reducing minor or harmful elements through the combination of more abundant elements. The properties of elements are correlated directly with their electronic states. In a solid, the magnitude of the density of states (DOS) at the Fermi level affects the physical and chemical properties. In the present age, more attention has been paid to improving the properties of materials by means of alloying elements. In particular, the solid-solution-type alloy is advantageous because the properties can be continuously controlled by tuning the compositions and/or combinations of the constituent elements. However, the majority of bulk alloys are of the phase-separated type under ambient conditions, where constituent elements are immiscible with each other. To overcome the challenge of the bulk-phase metallurgical aspects, we have focused on the nanosize effect and developed methods involving "nonequilibrium synthesis" or "a process of hydrogen absorption/desorption". We propose a new concept of "density-of-states engineering" for the design of materials having the most desirable and suitable properties by means of "interelement fusion". In this Account, we describe novel solid-solution alloys of Pd-Pt, Ag-Rh, and Pd-Ru systems in which the constituent elements are immiscible in the bulk state. The homogeneous solid-solution alloys of Pd and Pt were created from Pd core/Pt shell nanoparticles using a
Modelling thermal radiation and soot formation in buoyant diffusion flames
International Nuclear Information System (INIS)
The radiative heat transfer plays an important role in fire problems since it is the dominant mode of heat transfer between flames and surroundings. It controls the pyrolysis, and therefore the heat release rate, and the growth rate of the fire. In the present work a numerical study of buoyant diffusion flames is carried out, with the main objective of modelling the thermal radiative transfer and the soot formation/destruction processes. In a first step, different radiative property models were tested in benchmark configurations. It was found that the FSCK coupled with the Modest and Riazzi mixing scheme was the best compromise in terms of accuracy and computational requirements, and was a good candidate to be implemented in CFD codes dealing with fire problems. In a second step, a semi-empirical soot model, considering acetylene and benzene as precursor species for soot nucleation, was validated in laminar co flow diffusion flames over a wide range of hydrocarbons (C1-C3) and conditions. In addition, the optically-thin approximation was found to produce large discrepancies in the upper part of these small laminar flames. Reliable predictions of soot volume fractions require the use of an advanced radiation model. Then the FSCK and the semi-empirical soot model were applied to simulate laboratory-scale and intermediate-scale pool fires of methane and propane. Predicted flame structures as well as the radiant heat flux transferred to the surroundings were found to be in good agreement with the available experimental data. Finally, the interaction between radiation and turbulence was quantified. (author)
Persistence of Strain in Buoyant and Nonbuoyant Turbulent Nonpremixed Flames
Boratav, O.; Elghobashi, S.; Zhong, R.
1997-11-01
The effects of chemical reaction and buoyancy on the persistence of strain are studied in three different flows: i) Nonbuoyant flame, ii) Buoyant flame with gravity perpendicular to the initial fuel-oxidant interface (horizontal flame) and iii) Same as (ii), but gravity is parallel to the initial interface (vertical flame). The magnitude of the rate of strain S_ij relative to vorticity ω is measured by the angle ψ = tan-1(2 S_ijS_ij/ω \\cdot ω). Three mixture fraction, F, regions of distinct ψ characteristics are identified: 1) F>F_st, 2) Fflames, regions and (2) are vorticity-dominated due to the large baroclinic vorticity production, i.e. ψ arrow 0, resulting in shifting the pdf's of the ω-strain eigendirection more towards the β direction than the α. In region (3), the vorticity production is negligible for all three flows and at all times, thus resulting in the persistence of strain dominance over vorticity, i.e. ψ ≈ π/2, enforcing the alignment of ω with the α eigendirection. Consequently, the nabla F transport equation shows that nabla F will be located in the β-γ plane near F_st. Since |γ| > |β|, the largest straining of nabla F will be mostly along the direction of the most compressive strain direction γ near F_st as observed in all three cases. Our DNS results show that in reacting flows, the peak scalar dissipation ɛF will be near F_st regardless of the presence of buoyancy.
Numerical simulation of turbulent buoyant flows in horizontal channels
International Nuclear Information System (INIS)
A numerical method is presented, to calculate the three-dimensional, time-dependent large scale structure of turbulent buoyant flows. The subject of the study is the Rayleigh-Benard-convection with air (Pr=0.71, Ra=2.5 106, 107) and sodium (Pr=0.006, Ra=8.4 104, 2.5 105, 106, 107) and a fluid layer with water and an internal heat source (Pr=7.0, RaI=1.5 1010) at moderate and high Rayleigh-numbers. The goal of the work is both, the analysis of structures of instantaneous as well as the statistical analysis of spatially and/or time averaged data, to give a contribution to the investigation of the characteristics of turbulent natural convection mainly in fluids with small Prandtl-numbers. The large eddy simulation of natural convection requires the development of appropriate momentum and heat subgrid scale models and the formulation of new boundary conditions. The used energy-length-models in the computer code TURBIT are extended methodically by modification of the characteristic length scales of the sub scale turbulence. The reduction or the increase of the sub scale turbulence correlations, caused by the influence of solid boundaries or the stratification, is considered. In the same way the new boundary conditions for the diffusive terms of the conservation equations are seen to be necessary, when the thermal or in the case of liquid metals the more critical hydrodynamic boundary layer is resolved insufficiently or not at all. The extended and new methods, models and boundary conditions, which enabled the realization of the planned simulations, are presented. (orig.)
Supergranulation as the Sun's largest buoyantly driven mode of convection
Cossette, Jean-Francois; Rast, Mark
2016-05-01
Solar supergranulation has been characterized as horizontally divergent flow motions having a typical scale of 32 Mm using Doppler imaging, granule tracking and helioseismology. Unlike granules, the size of which is comparable to both the thickness of the radiative boundary layer and local scale height at the photosphere, supergranules do not appear to correspond to any particular length scale of the flow. Possible explanations ranging from convection theories involving Helium ionization to spatial correlation or self-organization of granular flows have been proposed as physical mechanisms to explain solar supergranulation. However, its existence remains largely a mystery. Remarkably, horizontal velocity power spectra obtained from Doppler imaging and correlation tracking of flow features at the solar surface reveal the presence of peaks corresponding to granular and supergranular scales, followed by a monotonic decrease in power at scales larger than supergranulation, which suggests that large-scale modes in the deep layers of the convection zone may be suppressed. Using 3D anelastic simulations of solar convection we investigate whether supergranulation may reflect the largest buoyantly driven mode of convection inside the Sun. Results show that the amount of kinetic energy contained in the largest flow scales relative to that associated with supergranular motions is a function of the depth of the transition from a convectively unstable to convectively stable mean stratification inside the simulation. This suggests that the observed monotonic decrease in power at scales larger than supergranulation may be explained by rapid cooling in the subphotospheric layers and an essentially isentropic solar interior, wherein convective driving is effectively suppressed.
Sasaki, Koichi; Ishigame, Hiroaki; Nishiyama, Shusuke
2015-01-01
This paper reports the density distributions of OH, Na, water vapor and water mist in atmospheric-pressure dc helium glow plasmas in contact with NaCl solution. The densities of OH, Na and H2O had different spatial distributions, while the Na density had a similar distribution to mist, suggesting that mist is the source of Na in the gas phase. When the flow rate of helium toward the electrolyte surface was increased, the distributions of all the species densities concentrated in the neighbori...
Lv, Boqiang; Shi, Xiaoding; Zhong, Xin
2015-01-01
We are concerned with the Cauchy problem of the two-dimensional (2D) nonhomogeneous incompressible Navier-Stokes equations with vacuum as far-field density. It is proved that if the initial density decays not too slow at infinity, the 2D Cauchy problem of the density-dependent Navier-Stokes equations on the whole space $\\mathbb{R}^2$ admits a unique global strong solution. Note that the initial data can be arbitrarily large and the initial density can contain vacuum states and even have compa...
Elmahdy, Mahdy M; Drechsler, Astrid; Uhlmann, Petra; Stamm, Manfred
2016-06-01
In previous studies, the authors found that end-grafted layers of the weak polybase poly(2-vinylpyridine) (P2VP) in aqueous solutions do not only swell and collapse if the pH value and salt concentration are varied but also exhibit a pH- and salinity-dependent adhesion to microsized silica spheres. For a better understanding of these effects, in situ force measurements using the AFM colloidal probe technique were applied to end-grafted P2VP layers of different grafting densities in NaCl solutions at pH 2.5. Although a mushroom-to-brush transition could be seen in the dry state, the layers were in the brush regime in aqueous solutions at all NaCl concentrations and grafting densities. We observed an increase of the brush height with increasing grafting density and a salinity-dependent collapse and reswelling of the brushes. The adhesion between the P2VP layer and a silica sphere depended on both grafting density and salinity. At low salt concentrations, the adhesion reached its highest value at the intermediate grafting density and disappeared with denser brushes. Maximum adhesion was obtained for high NaCl concentrations and the lowest grafting density. From a detailed analysis of the experiments, we gained insight into chain stretching and density profiles under complex ionic conditions and into the mechanism of adhesion of polyelectrolytes to solid surfaces. PMID:27172173
International Nuclear Information System (INIS)
Highlights: • Apparent and partial molar volumes of aqueous AAILs at T = (293.15 to 313.15) K. • Isothermal and adiabatic compressibilities of AAILs in aqueous solution at T = 298.15 K. • Method for direct estimation of hydration numbers due to electrostriction is given. • Internal pressure and hydration numbers for AAILs at T = 298.15 K. • Results obtained demonstrate kosmotropic behavior of AAILs. - Abstract: Amino acid ionic liquids (AAILs) have huge potential in the field of protein chemistry, enzymatic reactions, templates for synthetic study etc. which is due to their distinctive properties like unique acid-base characteristics, tunable hydrophobicity, hydrogen bonding ability and strong hydration effects. To explore the field of bio-ionic liquids for its real life applications and sustainable technology development, it is essential to have better understanding of these newly researched liquid salts in life’s most chosen medium, i.e. in aqueous medium, through study of their physicochemical properties in aqueous solutions. In this context, we are reporting herewith measurements and analysis of volumetric properties in the temperature range of (293.15 to 313.25) K and acoustic properties at 298.15 K in the concentration range of (0.05 to 0.5) mol · kg−1 for aqueous solutions of 1-butyl-3-methylimidazolium [Bmim] based amino acid ionic liquids, prepared from glycine, L-alanine, L-valine, L-leucine and L-isoleucine. The experimental density and sound speed data were used to obtain apparent, partial and limiting molar volumes as well as isentropic and isothermal compressibility properties. These data have been further used to understand electrostriction as well as concentration dependence of internal pressure. The hydration numbers for AAILs in aqueous medium were estimated from compressibility data using Passynski method and the estimated ionic hydration numbers are compared with those obtained using activity data. The results are explained in
International Nuclear Information System (INIS)
Highlights: ► Molecular recognition properties of metal bis-porphyrins at high concentration. ► The formation of the complex causes the disruption of the aggregates. ► High sensitivity for the optical detection of low amount of amino acids. ► Potential applications as a selective molecular sensor of amino acids. - Abstract: Small angle X-ray measurements on concentrated solutions of Cobalt-bis-porphyrins showed, at all the investigated concentration values, the presence of small aggregates which possess a sphere-like shape with a homogeneous electron density distribution. Such an aggregation, however, is proven not to affect the binding properties of the molecules with amino acids. Indeed, the Cobalt ion of the bis-porphyrins are available for coordinating the nitrogen atom of the amino acid to form a stable complex, as indicated by UV–vis and circular dichroism spectroscopy. The ability of these uncharged water-soluble bis-porphyrins to act as molecular sensors of amino acids in a wide concentration range takes great relevance in biosensing applications for which high concentration might be required.
Energy Technology Data Exchange (ETDEWEB)
Deeney, F A; O' Leary, J P [Physics Department, National University of Ireland, Cork, Republic of Ireland (Ireland)], E-mail: f.a.deeney@ucc.ie
2008-09-15
The connection between quantum zero point fluctuations and a density maximum in water and in liquid He{sup 4} has recently been established. Here we present a description of a simple and rapid method of determining the temperatures at which maximum densities in water and aqueous solutions occur. The technique is such as to allow experiments to be carried out in one session of an undergraduate laboratory thereby introducing students to the concept of quantum zero point energy.
Guru, Pravat Ranjan; Nayak, Amit Kumar; Sahu, Rajendra Kumar
2013-04-01
The current investigation deals with the development and optimization of oil-entrapped sterculia gum-alginate buoyant beads containing aceclofenac by ionotropic emulsion-gelation technique using 3(2) factorial design. The effect of polymer to drug ratio and sodium alginate to sterculia gum ratio on the drug entrapment efficiency (%), and cumulative drug release after 7 h (%) was optimized. The optimized oil-entrapped sterculia gum-alginate buoyant beads containing aceclofenac (F-O) showed drug entrapment efficiency of 90.92±2.34%, cumulative drug release of 41.65±3.97% after 7 h in simulated gastric fluid (pH 1.2), and well buoyancy over 8 h in simulated gastric fluid (pH 1.2) with 5.20 min buoyant lag-time. The in vitro drug release from these buoyant beads followed Korsmeyer-Peppas model (R(2)=0.9866-0.9995) with anomalous (non-Fickian) diffusion drug release mechanism. These new sterculia gum-alginate buoyant beads containing aceclofenac were also characterized using SEM, FTIR, and P-XRD analysis. PMID:23334180
Energy Technology Data Exchange (ETDEWEB)
Cao, Siqin [The HKUST Shenzhen Research Institute, Shenzhen (China); Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Sheong, Fu Kit [Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Huang, Xuhui, E-mail: xuhuihuang@ust.hk [The HKUST Shenzhen Research Institute, Shenzhen (China); Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Division of Biomedical Engineering, Center of Systems Biology and Human Health, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)
2015-08-07
Reference interaction site model (RISM) has recently become a popular approach in the study of thermodynamical and structural properties of the solvent around macromolecules. On the other hand, it was widely suggested that there exists water density depletion around large hydrophobic solutes (>1 nm), and this may pose a great challenge to the RISM theory. In this paper, we develop a new analytical theory, the Reference Interaction Site Model with Hydrophobicity induced density Inhomogeneity (RISM-HI), to compute solvent radial distribution function (RDF) around large hydrophobic solute in water as well as its mixture with other polyatomic organic solvents. To achieve this, we have explicitly considered the density inhomogeneity at the solute-solvent interface using the framework of the Yvon-Born-Green hierarchy, and the RISM theory is used to obtain the solute-solvent pair correlation. In order to efficiently solve the relevant equations while maintaining reasonable accuracy, we have also developed a new closure called the D2 closure. With this new theory, the solvent RDFs around a large hydrophobic particle in water and different water-acetonitrile mixtures could be computed, which agree well with the results of the molecular dynamics simulations. Furthermore, we show that our RISM-HI theory can also efficiently compute the solvation free energy of solute with a wide range of hydrophobicity in various water-acetonitrile solvent mixtures with a reasonable accuracy. We anticipate that our theory could be widely applied to compute the thermodynamic and structural properties for the solvation of hydrophobic solute.
International Nuclear Information System (INIS)
Reference interaction site model (RISM) has recently become a popular approach in the study of thermodynamical and structural properties of the solvent around macromolecules. On the other hand, it was widely suggested that there exists water density depletion around large hydrophobic solutes (>1 nm), and this may pose a great challenge to the RISM theory. In this paper, we develop a new analytical theory, the Reference Interaction Site Model with Hydrophobicity induced density Inhomogeneity (RISM-HI), to compute solvent radial distribution function (RDF) around large hydrophobic solute in water as well as its mixture with other polyatomic organic solvents. To achieve this, we have explicitly considered the density inhomogeneity at the solute-solvent interface using the framework of the Yvon-Born-Green hierarchy, and the RISM theory is used to obtain the solute-solvent pair correlation. In order to efficiently solve the relevant equations while maintaining reasonable accuracy, we have also developed a new closure called the D2 closure. With this new theory, the solvent RDFs around a large hydrophobic particle in water and different water-acetonitrile mixtures could be computed, which agree well with the results of the molecular dynamics simulations. Furthermore, we show that our RISM-HI theory can also efficiently compute the solvation free energy of solute with a wide range of hydrophobicity in various water-acetonitrile solvent mixtures with a reasonable accuracy. We anticipate that our theory could be widely applied to compute the thermodynamic and structural properties for the solvation of hydrophobic solute
Powering of cool filaments in cluster cores by buoyant bubbles - I. Qualitative model
Churazov, E.; Ruszkowski, M.; Schekochihin, A.
2013-11-01
Cool-core clusters (e.g. Perseus or M87) often possess a network of bright gaseous filaments, observed in radio, infrared, optical and X-ray bands. We propose that these filaments are powered by the reconnection of the magnetic field in the wakes of buoyant bubbles. Active galactic nucleus (AGN)-inflated bubbles of relativistic plasma rise buoyantly in the cluster atmosphere, stretching and amplifying the field in the wake to values of β = 8πPgas/B2 ˜ 1. The field lines in the wake have opposite directions and are forced together as the bubble motion stretches the filament. This setup bears strong similarity to the coronal loops on the Sun or to the Earth's magnetotail. The reconnection process naturally explains both the required level of local dissipation rate in filaments and the overall luminosity of filaments. The original source of power for the filaments is the potential energy of buoyant bubbles, inflated by the central AGN.
Powering of cool filaments in cluster cores by buoyant bubbles. I. Qualitative model
Churazov, E; Schekochihin, A
2013-01-01
Cool-core clusters (e.g., Perseus or M87) often possess a network of bright gaseous filaments, observed in radio, IR, optical and X-ray bands. We propose that these filaments are powered by the reconnection of the magnetic field in the wakes of buoyant bubbles. AGN-inflated bubbles of relativistic plasma rise buoyantly in the cluster atmosphere, stretching and amplifying the field in the wake to values of $\\beta =8\\pi P_{gas}/B^2\\sim 1$. The field lines in the wake have opposite directions and are forced together as the bubble motion stretches the filament. This setup bears strong similarity to the coronal loops on the Sun or the Earth magneto-tail. The reconnection process naturally explains both the required level of local dissipation rate in filaments and the overall luminosity of filaments. The original source of power for the filaments is the potential energy of buoyant bubbles, inflated by the central AGN.
Perturbation and stability analyses of nonlinear buoyant flow in mushy layers
Energy Technology Data Exchange (ETDEWEB)
Okhuysen, B S [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Riahi, D N, E-mail: driahi@utpa.ed [Department of Mathematics, 1201 West University Drive, University of Texas-Pan American, Edinburg, TX 78541-2999 (United States)
2010-10-15
We consider the problem of weakly nonlinear buoyant flow and its stability in horizontal dendrite layers, often referred to as mushy layers, during solidification of binary alloys. A mushy layer is a layer that is formed adjacent to the solidification front and is composed of both solid dendrites and melt. Understanding the convective flow driven by the buoyancy force within the mushy layer is known to be important for proper production of high-quality solidified alloy. In the present study, no restriction is imposed on the thickness of the mushy layer, and a number of simplifying assumptions made in previous related nonlinear analyses are lifted here in order to determine the results on the basis of a more realistic model. Using perturbation and stability analyses and some numerical approaches, we determine the steady stable solutions to the weakly nonlinear problem under a certain range of the parameter values where such analyses are valid. The relevant parameters for the present problem are the Rayleigh number representing the buoyancy, the Stefan number representing the latent heat of solidification, a concentration ratio parameter representing the composition of the solid dendrites in the mushy layer, and the far-field temperature parameter. We found, in particular, that depending on the range of parameter values, stable convective flow is possible in the form of subcritical or supercritical down-hexagons, with down-flow at the cells' centers and up-flow at the cells' boundaries, and subcritical or supercritical up-hexagons, with up-flow at the cells' centers and down-flow at the cells' boundaries, supercritical rectangles, supercritical squares and supercritical rolls.
Willige, van R.W.G.; Linssen, J.P.H.; Legger, A.; Voragen, A.G.J.
2003-01-01
The influence of flavour absorption by low-density polyethylene (LDPE), polycarbonate (PC) and polyethylene terephthalate (PET) on taste perception of a model solution containing seven flavour compounds and orange juice in glass bottles was studied with and without pieces of the respective plastic f
Note: Buoyant-force assisted liquid membrane electrochemical etching for nano-tip preparation.
Zeng, Yongbin; Wang, Yufeng; Wu, Xiujuan; Xu, Kun; Qu, Ningsong
2014-12-01
A liquid membrane electrochemical etching process for preparing nano-tips is proposed by the introduction of buoyant force to the lower tip, in which the lower portion of the anodic wire is immersed into a floating layer. A mathematical model of this method is derived. Both calculation and experimental results demonstrate that the introduction of buoyant force can significantly decrease the tip radius. The lubricating oil and deionized water floating layers were tested for the processing of nano-tips. Further, high-aspect-ratio nano-electrodes were prepared by applying a relative vertical movement to the anodic wire. PMID:25554341
STABILITY AND MIXING CHARACTER FOR BUOYANT JETS IN QUIESCENT SHALLOW WATER
Institute of Scientific and Technical Information of China (English)
ZENG Yu-hong
2005-01-01
The near field stability and mixing characteristics of buoyant jets produced by thermal diffuse in quiescent shallow water are investigated numerically to predict under what combinations of discharge and ambient characteristics the near field will be stable or unstable.Analyses for different discharging types show that the discharge stability is purely dependent on the near-field behavior of the jets, or the dynamic interaction of the buoyant jet region, the surface impingement region and the internal hydraulic jump region, and is independent of the far-field geometry of the receiving water.The stability criterion is a function of the relative submerged depth, and source densimetric Froude number.
Directory of Open Access Journals (Sweden)
Sindt CW
2012-03-01
Full Text Available Christine W Sindt1, Trudy K Grout1, D Brice Critser1, Jami R Kern2, David L Meadows21University of Iowa Hospitals and Clinics, Iowa City, IA; 2Alcon Research Ltd, Fort Worth, TX, USABackground: The purpose of this study was to assess whether differences in central corneal dendritic immune cell densities associated with combinations of soft contact lenses and lens care solutions could be detected by in vivo confocal microscopy.Methods: Participants were adults naïve to contact lens wear (n = 10 or who wore soft contact lenses habitually on a daily-wear schedule (n = 38 or on a study-assigned schedule for 30 days with daily disposable silicone hydrogel lenses (n = 15. Central corneas were scanned using an in vivo confocal microscope. Cell densities were compared among groups by demographic parameters, lens materials, and lens care solutions (polyhexamethylene biguanide [PHMB], polyquaternium-1 and myristamidopropyl dimethylamine [PQ/MAPD], peroxide, or blister pack solution [for daily disposable lenses].Results: Among lens wearers, no associations were observed between immune cell densities and age, gender, or years of lens-wearing experience. Mean cell density was significantly lower (P < 0.01 in nonwearers (29 ± 23 cells/mm2, n = 10 than in lens wearers (64 ± 71 cells/mm2, n = 53. Mean cell density was lower (P = 0.21 with traditional polymer lenses (47 ± 44 cells/mm2, n = 12 than with silicone hydrogel lenses (69 ± 77 cells/mm2, n = 41. Lowest to highest mean density of immune cells among lens wearers was as follows: PQ/MAPD solution (49 ± 28 cells/mm2, blister pack solution (63 ± 81 cells/mm2, PHMB solution (66 ± 44 cells/mm2, and peroxide solution (85 ± 112 cells/mm2.Conclusion: In this pilot study, in vivo confocal microscopy was useful for detecting an elevated immune response associated with soft contact lenses, and for identifying lens-related and solution-related immune responses that merit further research.Keywords: Clear Care
Stec, Marcin; Tatarczuk, Adam; Spiewak, Dariusz; Wilk, Andrzej
2014-01-01
The densities of aqueous mixtures of aminoethylethanolamine (CAS #000111-41-1) were measured over the entire compositional range at temperatures of 283.15-343.15 K. The results of these measurements were used to calculate excess molar volumes and isobaric thermal expansion coefficients, and partial molar and apparent molar volumes and excess isobaric thermal expansion coefficients were subsequently derived. The excess molar volumes were correlated as a function of the mole fraction using the Redlich-Kister equation. Temperature dependences of the Redlich-Kister coefficients are also presented. The partial molar volumes at infinite dilution of AEEA in water were determined using two different methods. In addition, the solution density was correlated using a Joubian-Acree model. Aqueous solutions of AEEA exhibit similar properties to the aqueous solutions of other alkanolamines (like monoethanolamine) used in acid gas sweetening. PMID:24899753
Novel solution-soaking method for adding dopants to YBa2Cu3O7-x to achieve higher sintered densities
International Nuclear Information System (INIS)
YBa2Cu3O7-x was doped with various metal ions by a new technique in which a pellet (after binder burnout) was soaked in a solution containing the appropriate ions and then dried. The sintered density of the treated pellets depended on the dopant in the solution,and in many cases it was much higher than that obtained for pure YBa2Cu3O7-x (93% to 96% as compared with 85% to 90%). A study of the microstructure revealed that, in those cases where higher sintered densities were obtained, the grain size was much smaller. The grain morphology, however, did not change. It is likely that the high concentration of dopant adsorbed on the grain surface during solution soaking enhanced the rate of sintering
The aim of this research program is to improve our knowledge and predictive capability of buoyant plume dispersion in the convective boundary layer (CBL) with emphasis on the mean (C) and root-mean-square (?c) concentration fields. The CBL turbulence leads to large random fluc...
46 CFR 117.137 - Stowage of life floats and buoyant apparatus.
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Stowage of life floats and buoyant apparatus. 117.137 Section 117.137 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING MORE THAN 150 PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS LIFESAVING EQUIPMENT AND ARRANGEMENTS...
Energy Technology Data Exchange (ETDEWEB)
Brown, Richard S.; Pflugrath, Brett D.; Carlson, Thomas J.; Deng, Zhiqun
2012-02-03
On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing through hydroturbines experience a rapid decrease in pressure as they pass by the turbine blade and the severity of this decompression can be highly variable. This rapid decrease in pressure can result in injuries such as swim bladder rupture, exophthalmia, and emboli and hemorrhaging in the fins and tissues. However, recent research indicates that the presence of a telemetry tag (acoustic, radio, inductive) implanted inside the coelom of a juvenile salmon increases the likelihood that the fish will be injured or die during turbine passage. Thus, previous research conducted using telemetry tags implanted into the coelom of fish may have been inaccurate. Thus, a new technique is needed to provide unbiased estimates of survival through turbines. This research provides an evaluation of the effectiveness of a neutrally buoyant externally attached acoustic transmitter. Both nontagged fish and fish tagged with a neutrally buoyant external transmitter were exposed to a range of rapid decompressions simulating turbine passage. Juvenile Chinook salmon tagged with a neutrally buoyant externally attached acoustic transmitter did not receive a higher degree of barotrauma than their nontagged counterparts. We suggest that future research include field-based comparisons of survival and behavior among fish tagged with a neutrally buoyant external transmitter and those internally implanted with transmitters.
46 CFR 180.137 - Stowage of life floats and buoyant apparatus.
2010-10-01
... 46 Shipping 7 2010-10-01 2010-10-01 false Stowage of life floats and buoyant apparatus. 180.137 Section 180.137 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) LIFESAVING EQUIPMENT AND ARRANGEMENTS Survival Craft Arrangements and Equipment § 180.137 Stowage of life floats...
Sumi, Tomonari; Maruyama, Yutaka; Mitsutake, Ayori; Koga, Kenichiro
2016-06-01
In the conventional classical density functional theory (DFT) for simple fluids, an ideal gas is usually chosen as the reference system because there is a one-to-one correspondence between the external field and the density distribution function, and the exact intrinsic free-energy functional is available for the ideal gas. In this case, the second-order density functional Taylor series expansion of the excess intrinsic free-energy functional provides the hypernetted-chain (HNC) approximation. Recently, it has been shown that the HNC approximation significantly overestimates the solvation free energy (SFE) for an infinitely dilute Lennard-Jones (LJ) solution, especially when the solute particles are several times larger than the solvent particles [T. Miyata and J. Thapa, Chem. Phys. Lett. 604, 122 (2014)]. In the present study, we propose a reference-modified density functional theory as a systematic approach to improve the SFE functional as well as the pair distribution functions. The second-order density functional Taylor series expansion for the excess part of the intrinsic free-energy functional in which a hard-sphere fluid is introduced as the reference system instead of an ideal gas is applied to the LJ pure and infinitely dilute solution systems and is proved to remarkably improve the drawbacks of the HNC approximation. Furthermore, the third-order density functional expansion approximation in which a factorization approximation is applied to the triplet direct correlation function is examined for the LJ systems. We also show that the third-order contribution can yield further refinements for both the pair distribution function and the excess chemical potential for the pure LJ liquids.
International Nuclear Information System (INIS)
Highlights: ► Di- and tri-glycine in aqueous PEG400 solutions were investigated thermodynamically. ► Density and ultrasound speed of glycine oligomer-PEG400-water systems were measured. ► Apparent molar volumes and isentropic compressions were calculated. ► Apparent molar isobaric expansions were derived. ► Results were interpreted in terms of water–glycine oligomer-PEG400 interactions. -- Abstract: Density and ultrasound speed were measured accurately for diglycine + water, triglycine + water, diglycine + water-polyethylene glycol 400 (PEG400) and triglycine + water-PEG400 solutions at T = (293.15, 298.15, 303.15 and 308.15) K. The results were used in evaluating thermodynamic properties as apparent molar volumes (VØ) and apparent molar isentropic compressions (KSΦ) of diglycine and triglycine in water and in PEG400 solutions. Infinite dilution values of these parameters, VoØ, and KoSΦ, were obtained from their plots as a function of molality by extrapolation and have been utilized in obtaining transfer volumes and transfer compressions at infinite dilution. All transfer volumes and transfer compressions were found to increase with increasing molality of PEG400. Apparent molar isobaric expansions were derived from the temperature dependence of VØ values at infinite dilution and at finite concentrations. All the results were interpreted in terms of solute (diglycine or triglycine) and co-solute (PEG400) and solvent (H2O) interactions
Fan, Jianke; Zhao, Dapeng; Dong, Dongdong
2016-02-01
We determined P-wave tomographic images by inverting a large number of arrival-time data from 2749 local earthquakes and 1462 teleseismic events, which are used to depict the three-dimensional morphology of the subducted Eurasian Plate along the northern segment of the Manila Trench. Dramatic changes in the dip angle of the subducted Eurasian Plate are revealed from the north to the south, being consistent with the partial subduction of a buoyant plateau beneath the Luzon Arc. Slab tears may exist along the edges of the buoyant plateau within the subducted plate induced by the plateau subduction, and the subducted lithosphere may be absent at depths greater than 250 km at ˜19°N and ˜21°N. The subducted buoyant plateau is possibly oriented toward NW-SE, and the subducted plate at ˜21°N is slightly steeper than that at ˜19°N. These results may explain why the western and eastern volcanic chains in the Luzon Arc are separated by ˜50 km at ˜18°N, whereas they converge into a single volcanic chain northward, which may be related to the oblique subduction along the Manila Trench caused by the northwestern movement of the Philippine Sea Plate. A low-velocity zone is revealed at depths of 20-200 km beneath the Manila Accretionary Prism at ˜22°N, suggesting that the subduction along the Manila Trench may stop there and the collision develops northward. The Taiwan Orogeny may originate directly from the subduction of the buoyant plateau, because the initial time of the Taiwan Orogeny is coincident with that of the buoyant plateau subduction.
Influence of cooling on dynamics of buoyant jet
Goncharov, V P
2016-01-01
The Rayleigh--Taylor instability which is responsible for the occurrence of narrow upward jets are studied in the scope of the nonhydrostatic model with horizontally--nonuniform density and the Newtonian cooling. As analysis shows, the total hierarchy of instabilities in this model consists of three regimes -- collapse, algebraic instability, and inertial motion. Realization of these stages, mutual transitions and interference depend on a ratio between two characteristic time scales -- collapse time and cooling time.
International Nuclear Information System (INIS)
This paper provides for various cases of 235U enrichment or Pu isotopic vectors, and different reflectors, new minimum critical values of uranyl nitrate and plutonium nitrate solutions (H+=0) obtained by the standard IRSN calculation route and the new isopiestic density laws. Comparisons are also made with other more accurate routes showing that the standard one's results are most often conservative and usable for criticality safety assessments. (author)
Mamyrbekova, A. K.
2013-03-01
Physicochemical properties (density, dynamic viscosity, refraction index) of the DMSO-Cu(NO3)2 · 3H2O system are studied in the concentration range of 0.01-2 M at 298 K. The refraction index of a solution of copper(II) nitrate in dimethylsulfoxide (DMSO) is measured at 288-318 K. The excess and partial molar volumes of the solvent and dissolved substance are calculated analytically.
Adiabatic density surface, neutral density surface, potential density surface, and mixing path
Institute of Scientific and Technical Information of China (English)
HUANG Rui-xin
2014-01-01
In this paper, adiabatic density surface, neutral density surface and potential density surface are compared. The adiabatic density surface is defined as the surface on which a water parcellcan move adiabatically, without changing its potential temperature and salinity. For a water parcelltaken at a given station and pressure level, the corresponding adiabatic density surface can be determined through simple calculations. This family of surface is neutrally buoyant in the world ocean, and different from other surfaces that are not truly neutrally buoyant. In order to explore mixing path in the ocean, a mixing ratio m is introduced, which is defined as the portion of potential temperature and salinity of a water parcellthat has exchanged with the environment during a segment of migration in the ocean. Two extreme situations of mixing path in the ocean are m=0 (no mixing), which is represented by the adiabatic density curve, and m=1, where the original information is completely lost through mixing. The latter is represented by the neutral density curve. The reality lies in between, namely, 0
International Nuclear Information System (INIS)
Highlights: • The densities, refractive indices, and viscosities of aqueous DES solutions were measured. • DES are made from N,N-diethylethanol ammonium chloride + glycerol or ethylene glycol. • The temperature studied was (298.15 to 343.15) K. • The measured data were reported as functions of temperature and composition. • The measured data were represented satisfactorily by the applied correlations. -- Abstract: In this work, we report new experimental data on density, ρ, refractive index, nD, and viscosity, η, of two deep eutectic solvents, N,N-diethylethanol ammonium chloride–glycerol (DEACG) and N,N-diethylethanol ammonium chloride–ethylene glycol (DEACEG), and their aqueous solutions, over the complete composition range, at temperatures from (298.15 to 343.15) K. Densities and viscosities were measured using the vibrating tube and the falling ball techniques, respectively, while the refractive index at the sodium D line was measured using an automatic refractometer. We aimed to represent the measured properties as a function of temperature and composition, and correlated them using the Redlich–Kister-type equation, for density, a polynomial function, for refractive index, and the Vogel–Fulcher–Tammann (VFT) equation, for viscosity
Morphology of flows and buoyant bubbles in the Virgo cluster
Pavlovski, Georgi; Pope, Edward C D; Fangohr, Hans
2007-01-01
There is growing evidence that the active galactic nuclei (AGN) associated with the central elliptical galaxy in clusters of galaxies are playing an important role in the evolution of the intracluster medium (ICM) and clusters themselves. We use high resolution three-dimensional simulations to study the interaction of the cavities created by AGN outflows (bubbles) with the ambient ICM. The gravitational potential of the cluster is modelled using the observed temperature and density profiles of the Virgo cluster. We demonstrate the importance of the hydrodynamical Kutta-Zhukovsky forces associated with the vortex ring structure of the bubbles, and discuss possible effects of diffusive processes on their evolution.
Institute of Scientific and Technical Information of China (English)
ZHANG Baoqiang; CHEN Guoping; GUO Qintao
2012-01-01
An improved method using kernel density estimation (KDE) and confidence level is presented for model validation with small samples.Decision making is a challenging problem because of input uncertainty and only small samples can be used due to the high costs of experimental measurements.However,model validation provides more confidence for decision makers when improving prediction accuracy at the same time.The confidence level method is introduced and the optimum sample variance is determined using a new method in kernel density estimation to increase the credibility of model validation.As a numerical example,the static frame model validation challenge problem presented by Sandia National Laboratories has been chosen.The optimum bandwidth is selected in kernel density estimation in order to build the probability model based on the calibration data.The model assessment is achieved using validation and accreditation experimental data respectively based on the probability model.Finally,the target structure prediction is performed using validated model,which are consistent with the results obtained by other researchers.The results demonstrate that the method using the improved confidence level and kernel density estimation is an effective approach to solve the model validation problem with small samples.
Czech Academy of Sciences Publication Activity Database
Fleischer, F.; Weber, T.; Deloudi, S.; Palatinus, Lukáš; Steurer, W.
2010-01-01
Roč. 43, - (2010), s. 89-100. ISSN 0021-8898 Institutional research plan: CEZ:AV0Z10100521 Keywords : phase retrieval * charge flipping * low-density elimination Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.794, year: 2010
The Heads and Tails of Buoyant Autocatalytic Balls
Rogers, Michael C
2012-01-01
Buoyancy produced by autocatalytic reaction fronts can produce fluid flows that advect the front position, giving rise to interesting feedback between chemical and hydrodynamic effects. In a large diameter, extended cylinder that is relatively free of boundary constraints, localized initiation of an iodate-arsenous acid (IAA) reaction front on the bottom boundary generates a rising autocatalytic plume. Such plumes have several differences from their non-reactive counterparts. Using numerical simulation, we have found that if reaction is initiated using a spherical ball of product solution well above the bottom boundary, the subsequent flow can evolve much like an autocatalytic plume: the ball develops a reacting head and tail that is akin to the head and conduit of an autocatalytic plume, except that the tail is disconnected from the boundary. In the limit of large initial autocatalytic balls, however, growth of a reacting tail is suppressed and the resemblance to plumes disappears. Conversely, very small bal...
International Nuclear Information System (INIS)
Two hypotheses for the dissolution of SiO2 in ionic solutions are investigated via ab initio molecular dynamics (AIMD) simulations. The hypotheses are (1) that the presence of ions induces orientations in H2O molecules at the surface, which favor proton transfer to bridging oxygen (BO) atoms, and (2) the presence of ions induces stronger H-bonding between terminal hydroxyl (TH) groups and BO atoms, allowing proton transfer. It is found that the model structures produced by density functional theory simulations do not support the former hypothesis and are more consistent with the latter. (paper)
Generating buoyant magnetic flux ropes in solar-like convective dynamos
Nelson, Nicholas J
2014-01-01
Our Sun exhibits strong convective dynamo action which results in magnetic flux bundles emerging through the stellar surface as magnetic spots. Global-scale dynamo action is believed to generate large-scale magnetic structures in the deep solar interior through the interplay of convection, rotation, and shear. Portions of these large-scale magnetic structures are then believed to rise through the convective layer, forming magnetic loops which then pierce the photosphere as sunspot pairs. Previous global simulations of 3D MHD convection in rotating spherical shells have demonstrated mechanisms whereby large-scale magnetic wreaths can be generated in the bulk of the convection zone. Our recent simulations have achieved sufficiently high levels of turbulence to permit portions of these wreaths to become magnetically buoyant and rise through the simulated convective layer through a combination of magnetic buoyancy and advection by convective giant cells. These buoyant magnetic loops are created in the bulk of the...
Characteristics of flammable, buoyant hydrogen plumes rising from open vertical containers
Energy Technology Data Exchange (ETDEWEB)
Fardisi, S.; Karim, Ghazi A. [University of Calgary, Mechanical and Manufacturing Engineering Department, 2500 University Drive, NW, Calgary, Alberta (Canada)
2009-08-15
The dynamics of the dispersion of a fixed mass of the highly buoyant hydrogen when exposed to overlaying atmosphere with a negligible pressure difference from open vertical cylindrical enclosures are examined. Features of the rapid formation and dispersion of flammable mixtures both inside and immediate outside of the enclosure and their corresponding propagation rates were examined using a 3-D CFD model. For the cases considered, the puffs of the fuel-air mixture appear to produce lean flammable boundaries that move mainly at a near constant rate for much of the time. A similar simulation that used an axis-symmetrical 2-D model tended to under-predict the dynamics of the lean and rich mixture boundaries. Hydrogen plume characteristics were compared with that of the less buoyant methane and helium release. Unlike methane, helium propagation rate was found fairly close to that of hydrogen. (author)
Buoyant Magnetic Loops in a Global Dynamo Simulation of a Young Sun
Nelson, Nicholas J; Brun, Allan Sacha; Miesch, Mark S; Toomre, Juri
2011-01-01
The current dynamo paradigm for the Sun and sun-like stars places the generation site for strong toroidal magnetic structures deep in the solar interior. Sunspots and star-spots on sun-like stars are believed to arise when sections of these magnetic structures become buoyantly unstable and rise from the deep interior to the photosphere. Here we present the first 3-D global magnetohydrodynamic (MHD) simulation in which turbulent convection, stratification, and rotation combine to yield a dynamo that self-consistently generates buoyant magnetic loops. We simulate stellar convection and dynamo action in a spherical shell with solar stratification, but rotating three times faster than the current solar rate. Strong wreaths of toroidal magnetic field are realized by dynamo action in the convection zone. By turning to a dynamic Smagorinsky model for subgrid-scale turbulence, we here attain considerably reduced diffusion in our simulation. This permits the regions of strongest magnetic field in these wreaths to rise...
Influence of viscosity contrast on buoyantly unstable miscible fluids in porous media
Pramanik, Satyajit; Mishra, Manoranjan
2015-01-01
The influence of viscosity contrast on buoyantly unstable miscible fluids in a porous medium is investigated through a linear stability analysis (LSA) as well as direct numerical simulations (DNS). The linear stability method implemented in this paper is based on an initial value approach, which helps to capture the onset of instability more accurately than the quasi-steady state analysis. In the absence of displacement, we show that viscosity contrast delays the onset of instability in buoyantly unstable miscible fluids. Further, it is observed that suitably choosing the viscosity contrast and injection velocity a gravitationally unstable miscible interface can be stabilized completely. Through LSA we draw a phase diagram, which shows three distinct stability regions in a parameter space spanned by the displacement velocity and the viscosity contrast. DNS are performed corresponding to parameters from each regime and the results obtained are in accordance with the linear stability results. Moreover, the conv...
Canepa, Edward S.
2012-09-01
This article presents a new mixed integer programming formulation of the traffic density estimation problem in highways modeled by the Lighthill Whitham Richards equation. We first present an equivalent formulation of the problem using an Hamilton-Jacobi equation. Then, using a semi-analytic formula, we show that the model constraints resulting from the Hamilton-Jacobi equation result in linear constraints, albeit with unknown integers. We then pose the problem of estimating the density at the initial time given incomplete and inaccurate traffic data as a Mixed Integer Program. We then present a numerical implementation of the method using experimental flow and probe data obtained during Mobile Century experiment. © 2012 IEEE.
Gennaro, A M; Luquita, A; Rasia, M
1996-01-01
The hypothesis that the internal viscosity of erythrocytes is governed by the intracellular hemoglobin (Hb) concentration is examined. Here viscosity is determined by labeling of the cytoplasmic reduced glutathione with the spin label maleimido-Tempo. Erythrocyte populations with different Hb concentrations in isosmotic conditions were obtained through incomplete lysis, followed by cell resealing, and discontinuous density gradient separation. This procedure maintains normal cell shape and vo...
Gravity-driven thin-film flow with negatively buoyant particles
Mavromoustaki, A.; David, P; Hill, S.; Latterman, P.; Rosenthal, W.; Mata, M; Bertozzi, A. L.
2011-01-01
This arXiv article describes the fluid dynamics video on `Gravity-driven thin-film flow with negatively buoyant particles', presented at the 64th Annual Meeting of the APS Division of Fluid Dynamics in Baltimore, MD in November 2011. The video shows three different experiments where a thin film of silicone oil laden with particles, is allowed to flow down an incline under the action of gravity. The videos were recorded at the UCLA Applied Math Laboratory.
Burguete, J; Mukolobwiez, N.; Daviaud, F.; Garnier, N.; Chiffaudel, A.
2001-01-01
We report experiments on buoyant-thermocapillary instabilities in differentially heated liquid layers. The results are obtained for a fluid of Prandtl number 10 in a rectangular geometry with different aspect ratios. Depending on the height of liquid and on the aspect ratios, the two-dimensional basic flow destabilizes into oblique traveling waves or longitudinal stationary rolls, respectively, for small and large fluid heights. Temperature measurements and space–time recordings r...
Laser Soot-Scattering Imaging of a Large Buoyant Diffusion Flame
Miake-Lye, Richard C.; Toner, Stephen J.
1987-01-01
A novel diagnostic technique, which makes use of laser light scattered by soot particles, was used in an effort to identify the flame sheets within a natural gas diffusion flame. Soot particles, inherently created and consumed in the flame, were used as the scattering medium, which obviated the need for externally supplied seed material. Since no foreign material was added to the flame, the current technique can be considered truly nonintrusive. The soot distribution within a large buoyant...
Buoyant balaenids: the ups and downs of buoyancy in right whales.
Nowacek, D. P.; Johnson, M P; Tyack, P.L.; Shorter, K. A.; McLellan, W. A.; Pabst, D.A.
2001-01-01
A variety of marine mammal species have been shown to conserve energy by using negative buoyancy to power prolonged descent glides during dives. A new non-invasive tag attached to North Atlantic right whales recorded swim stroke from changes in pitch angle derived from a three-axis accelerometer. These results show that right whales are positively buoyant near the surface, a finding that has significant implications for both energetics and management. Some of the most powerful fluke strokes o...
Monupal, Suthar, B.
2016-05-01
The ultrasonic velocities, compressibility and bulk modulus of binary mixtures of aqueous solution of isopropyl alcohol with mustard oil have been measured at different concentrations at room temperature. The results are varied with the concentration in such a way i.e. ultrasonic velocity and Bulk Modulus is decreases with the increase in concentration and compressibility is increases with the increase in concentration of aqueous isopropyl alcohol. It is due to molecular interactions present in the mixtures.
Energy Technology Data Exchange (ETDEWEB)
Gao, Jiao [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631 (China); Hu, Yongjun, E-mail: yjhu@scnu.edu.cn [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631 (China); Li, Shaoxin, E-mail: lishaox@163.com [School of Information Engineering, Guangdong Medical College, Dongguan 523808 (China); Zhang, Yanjiao [School of Basic Medicine, Guangdong Medical College, Dongguan 523808 (China); Chen, Xue [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631 (China)
2013-01-02
Highlights: Black-Right-Pointing-Pointer The tautomeric equlibrium and behavior of creatinine in aqueous solutions have been firstly studied by means of Raman spectroscopy and theoretical calculations (DFT). Black-Right-Pointing-Pointer As 7 water molecules are gradually aggregated around the creatinine, theoretical results show an excellent accordance with the experimental spectrum. Black-Right-Pointing-Pointer Analysis of molecular electrostatic potential (MEP) for creatinine (two tautomers and one protonated form) could explain why typical experimental Raman spectra with different pH values have obvious discrepancies at the electrical level. -- Abstract: The Raman spectral studies of creatinine with pH dependence were performed to explore the effects of pH values on the Raman spectroscopy of creatinine. Firstly, we calculated vibrational spectra by DFT to derive the equilibrium geometries and protonated form of creatinine. Comparing simulated and observed Raman spectra of creatinine in aqueous solution at pH 2, it is found the theoretical predicted spectra agree well with those of the experiment while seven water molecules are aggregated around the creatinine. Additionally, the tautomeric equilibrium of creatinine in aqueous solutions was studied and two tautomers are found to coexist by comparing its experimental and calculated Raman spectra. A water dimer being used to solvate creatinine would make the thermodynamic energy favor convert from the imino tautomer to the amino tautomer. Besides, the molecular electrostatic potential (MEP) analysis of the creatinine further confirms their discrepancies of typical experimental Raman spectra at different pH values.
Institute of Scientific and Technical Information of China (English)
HUAI Wen-xin; FANG Shen-guang; DAI Hui-chao
2006-01-01
Some experiments were made for the buoyant jet from a square orifice with a square disc placed on it in static ambient and concentration along the axis in self-similar area behind disc was measured. And at the same time a three-dimensional mathematical model was established to simulate the whole flowing under different conditions. All the results predicted by the numerical calculation were substantiated by the experiments.The results were compared with experiential formula for obstructed round buoyant vertical jets in static ambient and it was found that the two concentration distributions had good accordance. Star shape of temperature isolines on cross-sections in the near areas from the disc was found and it was a very special figure for obstructed square buoyant vertical jets with a square disc. The shape will transform to concentric circles gradually alike to the round buoyant vertical jet in self-similar area with increasing of the distance from the disc.
Development of an explicit algebraic turbulence model for buoyant flows – Part 1: DNS analysis
International Nuclear Information System (INIS)
Highlights: • DNS analysis of channel flow for forced, mixed and natural convection regime. • Examination of algebraic turbulenc model main features with buoyancy. • Investigation of the weak equilibrium assumption for buoyant flows. • Assessment of the redistribution term model for EARSM with buoyancy effect. • Assessment of the pressure scrambling term model for EAHFM. -- Abstract: An analysis of DNS databases of vertical plane channel flow for forced, mixed and natural convection is proposed. This analysis aims to assess the main features needed to develop an algebraic model for buoyant flows. First, the weak equilibrium assumption, at the root of algebraic models, is investigated. This hypothesis is shown to fail near the velocity maximum and close to the walls but remains valid otherwise, whatever the convection regime. The models for the redistribution term and the pressure scrambling term are then analyzed on the same configurations. A linear form of the Speziale et al. (1991) model is retained for the redistribution term. No model for the pressure scrambling term is fully satisfactory; nevertheless some models are recommended. The buoyant contributions to the pressure term are investigated. Finally, the generalized gradient diffusion hypothesis, which could be used to model the turbulent heat fluxes in order to avoid the coupling with the Reynolds stresses, is shown to be inaccurate
Buoyant Magnetic Loops in a Global Dynamo Simulation of a Young Sun
Nelson, Nicholas J.; Brown, Benjamin P.; Brun, Allan Sacha; Miesch, Mark S.; Toomre, Juri
2011-10-01
The current dynamo paradigm for the Sun and Sun-like stars places the generation site for strong toroidal magnetic structures deep in the solar interior. Sunspots and starspots on Sun-like stars are believed to arise when sections of these magnetic structures become buoyantly unstable and rise from the deep interior to the photosphere. Here, we present the first three-dimensional global magnetohydrodynamic (MHD) simulation in which turbulent convection, stratification, and rotation combine to yield a dynamo that self-consistently generates buoyant magnetic loops. We simulate stellar convection and dynamo action in a spherical shell with solar stratification, but rotating three times faster than the current solar rate. Strong wreaths of toroidal magnetic field are realized by dynamo action in the convection zone. By turning to a dynamic Smagorinsky model for subgrid-scale turbulence, we here attain considerably reduced diffusion in our simulation. This permits the regions of strongest magnetic field in these wreaths to rise toward the top of the convection zone via a combination of magnetic buoyancy instabilities and advection by convective giant cells. Such a global simulation yielding buoyant loops represents a significant step forward in combining numerical models of dynamo action and flux emergence.
Numerical Study of A Round Buoyant Jet Under the Effect of JONSWAP Random Waves
Institute of Scientific and Technical Information of China (English)
CHEN Yong-ping; LI Chi-wai; ZHANG Chang-kuan; XU Zhen-shan
2012-01-01
This paper presents a numerical study on the hydrodynamic behaviours of a round buoyant jet under the effect of JONSWAP random waves.A three-dimensional large eddy simulation (LES) model is developed to simulate the buoyant jet in a stagnant ambient and JONSWAP random waves.By comparison of velocity and concentration fields,it is found that the buoyant jet exhibits faster decay of centedine velocity,wider lateral spreading and larger initial dilution under the wave effect,indicating that wave dynamics improves the jet entrainment and mixing in the near field,and subsequently mitigate the jet impacts in the far field.The effect of buoyancy force on the jet behaviours in the random waves is also numerically investigated.The results show that the wave effect on the jet entrainment and mixing is considerably weakened under the existence of buoyancy force,resulting in a slower decay rate of centerline velocity and a narrower jet width for the jet with initial buoyancy.
Tripathi, G.; Singh, S
2010-01-01
"n "nBackground and the purpose of the study: A gastroretentive pH sensitive system has been a frontier approach to release the drug in controlled manner in stomach and duodenum. The aim of this study was to develop buoyant beads of gellan based, wherein, the oil was entrapped, blended with hydroxypropyl methyl cellulose or carbopol 934 in order to evaluate its potential for targeted sustained delivery of clarithromycin in the gastric region. "nMethods: Buoyant beads ...
Hofmann, Hilmar; Peeters, Frank
2013-01-01
Optical (fluorescence) and acoustic in-situ techniques were tested in their ability to measure the spatial and temporal distribution of plankton in freshwater ecosystems with special emphasis on the harmful and buoyant cyanobacterium P. rubescens. Fluorescence was measured with the multi-spectral FluoroProbe (Moldaenke FluoroProbe, MFP) and a Seapoint Chlorophyll Fluorometer (SCF). In-situ measurements of the acoustic backscatter strength (ABS) were conducted with three different acoustic devices covering multiple acoustic frequencies (614 kHz ADCP, 2 MHz ADP, and 6 MHz ADV). The MFP provides a fast and reliable technique to measure fluorescence at different wavelengths in situ, which allows discriminating between P. rubescens and other phytoplankton species. All three acoustic devices are sensitive to P. rubescens even if other scatterers, e.g., zooplankton or suspended sediment, are present in the water column, because P. rubescens containing gas vesicles has a strong density difference and hence acoustic contrast to the ambient water and other scatterers. After calibration, the combination of optical and acoustical measurements not only allows qualitative and quantitative observation of P. rubescens, but also distinction between P. rubescens, other phytoplankton, and zooplankton. As the measuring devices can sample in situ at high rates they enable assessment of plankton distributions at high temporal (minutes) and spatial (decimeters) resolution or covering large temporal (seasonal) and spatial (basin scale) scales. PMID:24303028
Directory of Open Access Journals (Sweden)
Hilmar Hofmann
Full Text Available Optical (fluorescence and acoustic in-situ techniques were tested in their ability to measure the spatial and temporal distribution of plankton in freshwater ecosystems with special emphasis on the harmful and buoyant cyanobacterium P. rubescens. Fluorescence was measured with the multi-spectral FluoroProbe (Moldaenke FluoroProbe, MFP and a Seapoint Chlorophyll Fluorometer (SCF. In-situ measurements of the acoustic backscatter strength (ABS were conducted with three different acoustic devices covering multiple acoustic frequencies (614 kHz ADCP, 2 MHz ADP, and 6 MHz ADV. The MFP provides a fast and reliable technique to measure fluorescence at different wavelengths in situ, which allows discriminating between P. rubescens and other phytoplankton species. All three acoustic devices are sensitive to P. rubescens even if other scatterers, e.g., zooplankton or suspended sediment, are present in the water column, because P. rubescens containing gas vesicles has a strong density difference and hence acoustic contrast to the ambient water and other scatterers. After calibration, the combination of optical and acoustical measurements not only allows qualitative and quantitative observation of P. rubescens, but also distinction between P. rubescens, other phytoplankton, and zooplankton. As the measuring devices can sample in situ at high rates they enable assessment of plankton distributions at high temporal (minutes and spatial (decimeters resolution or covering large temporal (seasonal and spatial (basin scale scales.
Energy Technology Data Exchange (ETDEWEB)
Din, Alif [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, 44000 Islamabad (Pakistan)
2013-09-15
The exact theoretical expressions involved in the formation of sheath in front of an electron emitting electrode immersed in a low-density plasma have been derived. The potential profile in the sheath region has been calculated for subcritical, critical, and supercritical emissions. The potential profiles of critical and supercritical emissions reveals that we must take into account a small, instead of zero, electric field at the sheath edge to satisfy the boundary conditions used to integrate the Poisson's equation. The I-V curves for critical emission shows that only high values of plasma-electron to emitted-electron temperature ratio can meet the floating potential of the emissive electrode. A one-dimensional fluid like model is assumed for ions, while the electron species are treated as kinetic. The distribution of emitted-electron from the electrode is assumed to be half Maxwellian. The plasma-electron enters the sheath region at sheath edge with half Maxwellian velocity distribution, while the reflected ones have cut-off velocity distribution due to the absorption of super thermal electrons by the electrode. The effect of varying emitted-electron current on the sheath structure has been studied with the help of a parameter G (the ratio of emitted-electron to plasma-electron densities)
Energy Technology Data Exchange (ETDEWEB)
Suri, Rominder P.S. [Villanova Center for the Environment, Department of Civil and Environmental Engineering, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085-4263 (United States)]. E-mail: rominder.suri@villanova.edu; Nayak, Mohan [Villanova Center for the Environment, Department of Civil and Environmental Engineering, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085-4263 (United States); Devaiah, Uthappa [Villanova Center for the Environment, Department of Civil and Environmental Engineering, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085-4263 (United States); Helmig, Edward [Wyeth Pharmaceuticals, Frazer, PA 19355 (United States)
2007-07-31
There are many reports documenting the adverse effects, such as feminization of fish, of estrogen hormones in the environment. One of the major sources of these compounds is from municipal wastewater effluents. The biological processes at municipal wastewater treatment plants cannot completely remove these compounds. This paper discusses the use of ultrasound to destroy estrogen compounds in water. The study examines the effect of ultrasound power density and power intensity on the destruction of various estrogen compounds which include: 17{alpha}-estradiol, 17{beta}-estradiol, estrone, estriol, equilin, 17{alpha}-dihydroequilin, 17{alpha}-ethinyl estradiol and norgestrel. These tests were conducted in single component batch and flow through reactors using 0.6, 2 and 4 kW ultrasound sources. The sonolysis process produced 80-90% destruction of individual estrogens at initial concentration of 10 {mu}g/L within 40-60 min of contact time. First order rate constants for the individual compounds under different conditions are presented. The estrogen degradation rates increase with increase in power intensity. However, the energy efficiency of the reactor was higher at lower power density. The 4 kW ultrasound reactor was more energy efficient compared to the 0.6 and 2 kW sonicators.
Kristyan, Sandor
2013-11-01
Using orbital-free framework, a simple numerical optimization of the density functional for ground state electronic energy is described for any type of functional approximation, demonstrated via the example of linear combinations of homogeneous functionals of the density. The numerical recipe is given and analyzed for solution: Originating from the linear dependence of nuclear-electron attraction functional on one-electron density ( V ne[ ρ 0( r 1)] = -ΣA = 1,…,MZA∫ ρ 0( r 1)rA1 -1d r 1), and a quadratic LCAO approximation for ρ 0, the optimization can be done with iterative use of lin-solver. This quadratic approximation, as simplest educated choice for ρ 0, is compared and analyzed algebraically to the HF-SCF one in the Appendices. We call the attention that the introduction of a self-consistent field optimization of non-linear density functional is a new element in this part of the related, general theory.
Numerical studies of pulsating buoyant plume in isothermal and non isothermal situations
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A computational study has been carried out for predicting the behaviour of buoyant plume in isothermal and non isothermal configuration. General simulation objectives of any buoyant flow simulation are macroscopic in nature and deals with the grass data in respect of buoyancy induced scalar transport. However, the accuracy of predicting such macroscopic parameters is a strong function of several other microscopic parameters which govern the overall macroscopic behaviour. Some of the microscopic parameters for analysis could be buoyancy induced stable/unstable flows, relative plume behaviour, baroclinic velocity distribution etc. Only the CFD based flow modelling approach is capable of calculating several of these aspects. LES based modelling scores over the conventional RANS based computational modelling. The primary objective of the present study was to model buoyant plume simulation of different types in order to explore the details regarding plume and flow structure, instabilities and puffing behaviour. One of the influencing parameters on the overall plume behaviour is the buoyancy resolution index i.e. fineness of chosen grid in relation to the buoyancy intensity and other hydrodynamic parameters. The grid sensitivity studies have been carried out to find out the optimum value grid size by way of buoyant pool fire simulations. Comparative simulation has also been made for a square and round pool fire and it was found that for engineering simulations equivalent area square pool modeling is sufficient. Using the optimum value of grid size and square pool shape simulations have been carried out for different value of fire intensity. The flame puffing frequency as calculated by the reported correlation was compared against the computationally observed puffing frequency and the agreement was generally found to be excellent. Besides these results the comparisons of predicted peak flames temperatures data for various case studies with the available experimental data
Qiblawey, Hazim; Arshad, Mohammad; Easa, Ahmed; Atilhan, Mert
2014-01-01
Viscosities and densities of ternary systems of CaCl2–NaCl–water were measured in the range of T = (293.15 to 323.15) K at 5 K intervals and up to 4.5 mol·kg–1. Two equations based on the Exponential and Goldsack and Franchetto models were applied to correlate the experimental viscosity data as a function of concentration and temperature. The optimized parameters showed that the presence of CaCl2 had a prevailing effect on the viscosity of the ternary solutions than NaCl. The dependency of th...
Sindt CW; Grout TK; Critser DB; Kern JR; Meadows DL
2012-01-01
Christine W Sindt1, Trudy K Grout1, D Brice Critser1, Jami R Kern2, David L Meadows21University of Iowa Hospitals and Clinics, Iowa City, IA; 2Alcon Research Ltd, Fort Worth, TX, USABackground: The purpose of this study was to assess whether differences in central corneal dendritic immune cell densities associated with combinations of soft contact lenses and lens care solutions could be detected by in vivo confocal microscopy.Methods: Participants were adults naïve to contact lens we...
International Nuclear Information System (INIS)
Numerous and stiff coupled rate equations describing ionic charge-state distribution and the level populations is solved rapidly by using quasi-static state approximation. The physical meaning of the matrices (E**m)-1 and Tg defined in the paper is discussed and was used to given ideas on ionic charge-state distribution and the level populations. The Ne/Te objective region for 3d5/2-2P3/2 transitions in H-like C recombination X-ray lasers is obtained. The conclusion that ion abundance υs electron density at an electron temperature may have two peaks is derived. Z-scaling law is also obtained. Finally, the effect of auto-ionization and dielectronic capture process and whether the ionic charge-state distribution fits the binomial distribution are inspected
Zhao, Zuofeng; Angell, C Austen
2016-02-01
The striking increases in response functions observed during supercooling of pure water have been the source of much interest and controversy. Imminent divergences of compressibility etc. unfortunately cannot be confirmed due to pre-emption by ice crystallization. Crystallization can be repressed by addition of second components, but these usually destroy the anomalies of interest. Here we study systems in which protic ionic liquid second components dissolve ideally in water, and ice formation is avoided without destroying the anomalies. We observe a major heat capacity spike during cooling, which is reversed during heating, and is apparently of first order. It occurs just before the glassy state is reached and is preceded by water-like density anomalies. We propose that it is the much-discussed liquid-liquid transition previously hidden by crystallization. Fast cooling should allow the important fluctuations/structures to be preserved in the glassy state for leisurely investigation. PMID:26756943
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Density and viscosity measurements, over a wide range of concentration and temperature, were implied to investigate the effect of hydrophilic block length on the micellar properties of the aqueous solution of E/sub 40/ B/sub 80/ and E/sub 120/. diblock copolymers. Here E represents an oxyethylene, -[CH/C/sub 2/H/sub 5/CH/sub 2/O]- unit while B an oxybutylene, -[CH(C/sub 2/H/sub 5/)CH/sub 2/O]- unit and the subscripts denote the number-average block length. To calculate the intrinsic viscosities and solute-solvent interaction parameter viscosity measurements were made. Besides that the hydration value of micelle plus shape factor, u of aggregates were evaluated by combining the results of density and viscosity. The effects of varying E-block length and temperature on all calculated parameters were elucidated. Values calculated for shape factor, u were responsive to non spheroidal shape of aggregates and become more elongated with increasing the E-block length. (author)
Truflandier, Lionel A; Autschbach, Jochen
2010-03-17
Ab initio molecular dynamics (aiMD) simulations based on density functional theory (DFT) were performed on a set of five anionic platinum complexes in aqueous solution. (195)Pt nuclear magnetic shielding constants were computed with DFT as averages over the aiMD trajectories, using the two-component relativistic zeroth-order regular approximation (ZORA) in order to treat relativistic effects on the Pt shielding tensors. The chemical shifts obtained from the aiMD averages are in good agreement with experimental data. For Pt(II) and Pt(IV) halide complexes we found an intermediate solvent shell interacting with the complexes that causes pronounced solvent effects on the Pt chemical shifts. For these complexes, the magnitude of solvent effects on the Pt shielding constant can be correlated with the surface charge density. For square-planar Pt complexes the aiMD simulations also clearly demonstrate the influence of closely coordinated non-equatorial water molecules on the Pt chemical shift, relating the structure of the solution around the complex to the solvent effects on the metal NMR chemical shift. For the complex [Pt(CN)(4)](2-), the solvent effects on the Pt shielding constant are surprisingly small. PMID:20166712
International Nuclear Information System (INIS)
A special block osmometer has been constructed and applied to a systematic study of poly (vinyl alcohol and vinyl sulphate ester) (PVS) sodium salts in dilute and moderately concentrated salt free aqueous solutions. In order to avoid surely ionic contamination all parts of the equipment that can contact with the polyelectrolyte solutions were made of different kinds of plastics and glass. The pressure range spans from (50 to 1.3 . 105) Pa. The measuring system was found to be appropriate for determination of the molar mass of water soluble polymers, too. Above a certain analytical density of dissociable groups (ADDG) an ion size dependent transition was observed on the reduced osmotic pressure vs. concentration curves. The analysis of the osmotic pressure data has clearly revealed that the dependence of the degree of dissociation on ADDG calculated at zero polyelectrolyte concentration contradicts to 'ion condensation' theory. With increasing polyelectrolyte concentration the degree of dissociation decreased rather steeply but at very low concentrations sharp maximums appeared due either to the change in conformation of these charged macromolecules, or formation of dynamic clusters induced by salting out of neutral parts of the macromolecules by the ionized groups. The applicability of the scaling concept as well as the many possible ways of characterization of non-ideality of polyelectrolyte solutions will be discussed in detail.
Venturi, D.; Karniadakis, G. E.
2012-08-01
By using functional integral methods we determine new evolution equations satisfied by the joint response-excitation probability density function (PDF) associated with the stochastic solution to first-order nonlinear partial differential equations (PDEs). The theory is presented for both fully nonlinear and for quasilinear scalar PDEs subject to random boundary conditions, random initial conditions or random forcing terms. Particular applications are discussed for the classical linear and nonlinear advection equations and for the advection-reaction equation. By using a Fourier-Galerkin spectral method we obtain numerical solutions of the proposed response-excitation PDF equations. These numerical solutions are compared against those obtained by using more conventional statistical approaches such as probabilistic collocation and multi-element probabilistic collocation methods. It is found that the response-excitation approach yields accurate predictions of the statistical properties of the system. In addition, it allows to directly ascertain the tails of probabilistic distributions, thus facilitating the assessment of rare events and associated risks. The computational cost of the response-excitation method is order magnitudes smaller than the one of more conventional statistical approaches if the PDE is subject to high-dimensional random boundary or initial conditions. The question of high-dimensionality for evolution equations involving multidimensional joint response-excitation PDFs is also addressed.
International Nuclear Information System (INIS)
By using functional integral methods we determine new evolution equations satisfied by the joint response-excitation probability density function (PDF) associated with the stochastic solution to first-order nonlinear partial differential equations (PDEs). The theory is presented for both fully nonlinear and for quasilinear scalar PDEs subject to random boundary conditions, random initial conditions or random forcing terms. Particular applications are discussed for the classical linear and nonlinear advection equations and for the advection–reaction equation. By using a Fourier–Galerkin spectral method we obtain numerical solutions of the proposed response-excitation PDF equations. These numerical solutions are compared against those obtained by using more conventional statistical approaches such as probabilistic collocation and multi-element probabilistic collocation methods. It is found that the response-excitation approach yields accurate predictions of the statistical properties of the system. In addition, it allows to directly ascertain the tails of probabilistic distributions, thus facilitating the assessment of rare events and associated risks. The computational cost of the response-excitation method is order magnitudes smaller than the one of more conventional statistical approaches if the PDE is subject to high-dimensional random boundary or initial conditions. The question of high-dimensionality for evolution equations involving multidimensional joint response-excitation PDFs is also addressed.
Energy density of marine pelagic fish eggs
DEFF Research Database (Denmark)
Riis-Vestergaard, J.
2002-01-01
Analysis of the literature on pelagic fish eggs enabled generalizations to be made of their energy densities, because the property of being buoyant in sea water appears to constrain the proximate composition of the eggs and thus to minimize interspecific variation. An energy density of 1.34 J mul......(-1) of total egg volume is derived for most species spawning eggs without visible oil globules. The energy density of eggs with oil globules is predicted by (σ) over cap = 1.34 + 40.61 x (J mul(-1)) where x is the fractional volume of the oil globule. (C) 2002 The Fisheries Society of the British...
A numerical study of the motion of a neutrally buoyant cylinder in two dimensional shear flow
Pan, Tsorng-Whay; Chen, Shih-Di; Chu, Chin-Chou; Chang, Chien-Cheng
2012-01-01
In this paper, we investigate the motion of a neutrally buoyant cylinder of circular or elliptic shape in two dimensional shear flow of a Newtonian fluid by direct numerical simulation. The numerical results are validated by comparisons with existing theoretical, experimental and numerical results, including a power law of the normalized angular speed versus the particle Reynolds number. The centerline between two walls is an expected equilibrium position of the cylinder mass center in shear flow. When placing the particle away from the centerline initially, it migrates toward another equilibrium position for higher Reynolds numbers due to the interplay between the slip velocity, the Magnus force, and the wall repulsion force.
Three-Dimensional Magnetohydrodynamic Simulations of Buoyant Bubbles in Galaxy Clusters
O'Neill, Sean M.; De Young, David S.; Jones, Thomas W.
2009-12-01
We present the results of numerical models of bubble dynamics and morphology in magnetized galaxy cluster environments. Our set of simulations follows the evolution of initially spherical bubbles that rise buoyantly through the intracluster medium. As a result of commonly used initial conditions, such bubbles quickly develop into a toroidal shape that is stable against fragmentation in the absence of magnetic forces. The inclusion of even modest ambient magnetic fields, however, substantially affects such structures, and we discuss how bubble evolution depends upon ambient field strength and geometry.
Mushroom-Shaped Structures as Tracers of Buoyant Flow in the Galactic Disk
D'Avillez, M A; Avillez, Miguel A. de; Low, Mordecai-Mark Mac
2001-01-01
Recent HI emission observations of the Southern Galactic hemisphere have revealed a mushroom-like structure extending from z=-70 to -450 pc, composed of a stem and a cap. Similar structures occur in three-dimensional simulations of a dynamic galactic disk driven by isolated and clustered supernovae. Using these simulations, we show that hot gas in the Galactic disk that is not evacuated through chimneys expands into the cooler gas of the thick disk, forming mushroom-shaped structures. This new class of objects traces buoyant flow of hot gas into the thick disk.
AEROSTATIC AND AERODYNAMIC MODULES OF A HYBRID BUOYANT AIRCRAFT: AN ANALYTICAL APPROACH
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Anwar Ul Haque
2015-05-01
Full Text Available An analytical approach is essential for the estimation of the requirements of aerodynamic and aerostatic lift for a hybrid buoyant aircraft. Such aircrafts have two different modules to balance the weight of aircraft; aerostatic module and aerodynamic module. Both these modules are to be treated separately for estimation of the mass budget of propulsion systems and required power. In the present work, existing relationships of aircraft and airship are reviewed for its further application for these modules. Limitations of such relationships are also disussed and it is precieved that it will provide a strating point for better understanding of design anatomy of such aircraft.
International Nuclear Information System (INIS)
HfO2 is a neutron absorber and has been mechanically mixed with UO2 in nuclear fuel in order to control the core power distribution. During nuclear fission, the temperature at the center of the fuel pellet can reach above 1300 K, where hafnium may substitute uranium and form the binary solid solution of UO2–HfO2. UO2 adopts the cubic fluorite structure, but HfO2 can occur in monoclinic, tetragonal, and cubic structures. The distribution of Hf and U ions in the UO2–HfO2 binary and its atomic structure influence the thermal conductivity and melting point of the fuel. However, experimental data on the UO2–HfO2 binary are limited. Therefore, the enthalpies of mixing of the UO2–HfO2 binary with three different structures were calculated in this study using density functional theory and subsequent Monte Carlo simulations. The free energy of mixing was obtained from thermodynamic integration of the enthalpy of mixing over temperature. From the ΔG of mixing, a phase diagram of the binary was obtained. The calculated UO2–HfO2 binary forms extensive solid solution across the entire compositional range, but there are a variety of possible exsolution phenomena associated with the different HfO2 polymorphs. As the structure of the HfO2 end member adopts lower symmetry and becomes less similar to cubic UO2, the miscibility gap of the phase diagram expands, accompanied by an increase in cell volume by 7–10% as the structure transforms from cubic to monoclinic. Close to the UO2 end member, which is relevant to the nuclear fuel, the isometric uranium-rich solid solutions exsolve as the fuel cools, and there is a tendency to form the monoclinic hafnium-rich phase in the matrix of the isometric, uranium-rich solid solution phase
Justino, Licínia L G; Ramos, M Luísa; Abreu, Paulo E; Carvalho, Rui A; Sobral, Abilio J F N; Scherf, Ullrich; Burrows, Hugh D
2009-09-01
Relationships have been obtained between intermonomer torsional angle and NMR chemical shifts ((1)H and (13)C) for isolated chains of two of the most important poly(9,9-dialkylfluorenes), poly[9,9-bis(2-ethylhexyl)fluorene-2,7-diyl] (PF2/6) and the copolymer poly(9,9-dioctylfluorene-co-[2,1,3]benzothiadiazole-4,7-diyl) (F8BT), using DFT calculations. The correlations provide a model for NMR spectral data interpretation and the basis for analysis of conformational changes in poly(9,9-dialkylfluorene-2,7-diyl)s. The correlations obtained for PF2/6 indicate that the (13)C chemical shifts of the aromatic carbons close to the intermonomer connection (C1, C2, and C3) have minimum values at planar conformations (0 degrees and 180 degrees ) and maximum values at 90 degrees conformations. In contrast, the (1)H chemical shifts of the corresponding aromatic ortho protons (Ha and Hb) are greatest for planar conformations, and the minimum values are seen for 90 degrees conformations. For the F8BT copolymer, similar relationships are observed for the (1)H (Ha, Hb, and Hc) aromatic shifts. Considering the aromatic carbons of F8BT, the behavior of C2, C4, C5, and C6 is similar to that found for the PF2/6 carbons. However, C1 and C3 of the fluorene moiety behave differently with varying torsion angle. These are in close proximity to the fluorene-benzothiadiazole linkage and are markedly affected by interactions with the thiadiazole unit such that delta(C1) is a maximum for 180 degrees and a minimum for 0 degrees , whereas delta(C3) is a maximum for 0 degrees and minimum for 180 degrees. We have studied the (1)H and (13)C spectra of the two polymers at temperatures between -50 degrees C and +65 degrees C. The observed changes to higher or lower frequency in the aromatic resonances were analyzed using these theoretical relationships. Fluorescence studies on PF2/6 in chloroform solution suggest there are no significant interchain interactions under these conditions. This is supported
Voss, Clifford I.; Provost, A.M.
2002-01-01
SUTRA (Saturated-Unsaturated Transport) is a computer program that simulates fluid movement and the transport of either energy or dissolved substances in a subsurface environment. This upgraded version of SUTRA adds the capability for three-dimensional simulation to the former code (Voss, 1984), which allowed only two-dimensional simulation. The code employs a two- or three-dimensional finite-element and finite-difference method to approximate the governing equations that describe the two interdependent processes that are simulated: 1) fluid density-dependent saturated or unsaturated ground-water flow; and 2) either (a) transport of a solute in the ground water, in which the solute may be subject to: equilibrium adsorption on the porous matrix, and both first-order and zero-order production or decay; or (b) transport of thermal energy in the ground water and solid matrix of the aquifer. SUTRA may also be used to simulate simpler subsets of the above processes. A flow-direction-dependent dispersion process for anisotropic media is also provided by the code and is introduced in this report. As the primary calculated result, SUTRA provides fluid pressures and either solute concentrations or temperatures, as they vary with time, everywhere in the simulated subsurface system. SUTRA flow simulation may be employed for two-dimensional (2D) areal, cross sectional and three-dimensional (3D) modeling of saturated ground-water flow systems, and for cross sectional and 3D modeling of unsaturated zone flow. Solute-transport simulation using SUTRA may be employed to model natural or man-induced chemical-species transport including processes of solute sorption, production, and decay. For example, it may be applied to analyze ground-water contaminant transport problems and aquifer restoration designs. In addition, solute-transport simulation with SUTRA may be used for modeling of variable-density leachate movement, and for cross sectional modeling of saltwater intrusion in
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The densities of Di- (2-ethylhexyl) phosphoric acid containing organic solutions of n-dodecane as well as 0.2M TBP/n-dodecane were measured at several concentration and temperature levels and results were correlated. Coefficients of density equations of authors were estimated and excellent agreements were observed between experimental and predicted values. Contributions to organic densities are being incorporated in the indigenously developed computer code SIMPCATR for computer simulation of solvent extraction flow sheets. (author)
Directory of Open Access Journals (Sweden)
Ho-Jun Lee
2015-01-01
Full Text Available The recent development of dielectric microsphere lithography has been able to open up new means of performing simple and easy patterning on the semiconductor surfaces. Here, we report uniform and high-density arrays of microspheres using a solution-based spin-coating method. The arrays of microspheres were used for etching mask to form the arrays of III-nitride microrods. By regrowing GaN layer on the microrod structures, high-quality GaN layer was achieved in terms of surface morphology as well as XRD characterization. To apply the advantages such as improved crystal quality and light extraction enhancement, light-emitting diodes (LEDs were grown and then fabricated. The regrown LEDs with microspheres showed much improved optical output power and forward voltage characteristics in the same current injection. Therefore, we believe that this approach is quite useful for the development of high efficiency LEDs for future lighting.
Formation of lower continental crust by relamination of buoyant arc lavas and plutons
Kelemen, Peter B.; Behn, Mark D.
2016-03-01
The formation of the Earth's continents is enigmatic. Volcanic arc magmas generated above subduction zones have geochemical compositions that are similar to continental crust, implying that arc magmatic processes played a central role in generating continental crust. Yet the deep crust within volcanic arcs has a very different composition from crust at similar depths beneath the continents. It is therefore unclear how arc crust is transformed into continental crust. The densest parts of arc lower crust may delaminate and become recycled into the underlying mantle. Here we show, however, that even after delamination, arc lower crust still has significantly different trace element contents from continental lower crust. We suggest that it is not delamination that determines the composition of continental crust, but relamination. In our conceptual model, buoyant magmatic rocks generated at arcs are subducted. Then, upon heating at depth, they ascend and are relaminated at the base of the overlying crust. A review of the average compositions of buoyant magmatic rocks -- lavas and plutons -- sampled from the Aleutians, Izu-Bonin-Marianas, Kohistan and Talkeetna arcs reveals that they fall within the range of estimated major and trace elements in lower continental crust. Relamination may thus provide an efficient process for generating lower continental crust.
Characterization of Buoyant Fluorescent Particles for Field Observations of Water Flows
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Flavia Tauro
2010-12-01
Full Text Available In this paper, the feasibility of off-the-shelf buoyant fluorescent microspheres as particle tracers in turbid water flows is investigated. Microspheres’ fluorescence intensity is experimentally measured and detected in placid aqueous suspensions of increasing concentrations of clay to simulate typical conditions occurring in natural drainage networks. Experiments are conducted in a broad range of clay concentrations and particle immersion depths by using photoconductive cells and image-based sensing technologies. Results obtained with both methodologies exhibit comparable trends and show that the considered particles are fairly detectable in critically turbid water flows. Further information on performance and integration of the studied microspheres in low-cost measurement instrumentation for field observations is obtained through experiments conducted in a custom built miniature water channel. This experimental characterization provides a first assessment of the feasibility of commercially available buoyant fluorescent beads in the analysis of high turbidity surface water flows. The proposed technology may serve as a minimally invasive sensing system for hazardous events, such as pollutant diffusion in natural streams and flash flooding due to extreme rainfall.
Laboratory experiments on the interaction between inclined negatively buoyant jets and regular waves
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Ferrari Simone
2015-01-01
Full Text Available In this paper we present the results from a series of laboratory experiments on inclined negatively buoyant jets released in a receiving environment with waves. This simulates the case, typical of many practical applications, of the sea discharge of fluids denser than the receiving environment, as in the case of the brine from a desalination plant. The experiments were performed employing a Light Induced Fluorescence (LIF technique, in order to measure the concentration fields. Both the jet and the wave motion features were varied, in order to simulate a typical discharge into the Mediterranean Sea. Reference discharges in a stagnant environment were performed as well. The jet behaviour was analyzed from a statistical point of view, both considering the global phenomenon and its single phases. The influence of the wave motion on the inclined negatively buoyant jet geometry and dilution turns out to be a combined action of a split into two branches of the jet and a rotation. Their combined action decreases the jet maximum height and the impact distance, and is the main cause for the higher dilution reached in a wavy environment.
Saltwater intrusion at a buoyant jet discharge in a fringing reef lagoon
Parra, S. M.; Marino-Tapia, I.; Enriquez, C.; Valle-Levinson, A.
2013-05-01
The influence of tides and waves on turbulent kinetic energy (TKE) from a buoyant jet discharge in a fringing reef lagoon was observed with measurements obtained throughout an 11-day period in July 2011. Tidal variations within the lagoon modulated TKE levels, temperature, and salinity at the buoyant jet. During neap and low tides, TKE values were predominantly >0.015 m2/s2. During neap tides, TKE at the jet was greater than during spring tides, meaning that larger tidal oscillations inhibited TKE production at the jet. When the water surface over the jet remained >0.02 m above the mean, TKE was suppressed to intrusion into the aquifer. This demonstrates the sensitivity of the jet discharge to fortnightly tides, despite the small tidal range (intrusion into the aquifer caused by the spring tide oscillations. Therefore, increased sea levels, as illustrated here by the combination of incident waves, wave set-up and fortnightly tidal oscillations, is expected to threaten delicate aquifer conditions and vital water resources for coastal communities worldwide.
Residence times of neutrally-buoyant matter such as larvae, sewage or nutrients on coral reefs
Black, Kerry P.; Gay, Stephen L.; Andrews, John C.
1990-12-01
Coral reef flushing times at an individual reef scale are specified and a general formula to determine these times is developed. The formula is confirmed by comparison with residence times predicted by numerical small-scale reef models, including those from a 4 month unsteady current simulation of John Brewer Reef on Australia's Great Barrier Reef. The method proves to be a satisfactory alternative to the numerical modelling. When neutrally-buoyant material around a reef is removed by the currents, the concentrations decay exponentially. The decay rate depends primarily on free stream current and reef dimensions. Secondary factors are the tidal excursion, shelf depth, lagoon size and residual current in the lee of the reef. These factors, when combined into a decay coefficient, specify the rate of loss of neutrally-buoyant material (e.g. some larvae, pollutants and sewage) from a coral reef and its surrounds. The analytical formula can be used to predict the flushing rates or the percentage of material still remaining on a reef after a selected time interval. We demonstrate that material can remain on or near typical reefs in common weather conditions for several weeks.
International Nuclear Information System (INIS)
In this work, Pa(V) mono-cations have been studied in liquid water by means of density functional theory (DFT) based molecular dynamic simulations (CPMD) and compared with their U(VI) isoelectronic counterparts to understand the peculiar chemical behavior of Pa(V) in aqueous solution. Four different Pa(V) monocationic isomers appear to be stable in liquid water from our simulations: [PaO2(H2O)5]+(aq), [Pa(OH)4(H2O)2]+(aq), [PaO(OH)2(H2O)4]+(aq), and [Pa(OH)4(H2O)3]+(aq). On the other hand, in the case of U(VI) only the uranyl, [UO2(H2O)5]2+(aq), is stable. The other species containing hydroxyl groups replacing one or two oxo bonds are readily converted to uranyl. The Pa-OH bond is stable, while it is suddenly broken in U-OH. This makes possible the formation of a broad variety of Pa(V) species in water and participates to its unique chemical behavior in aqueous solution. Further, the two actinyl oxo-cations in water are different in the ability of the oxygen atoms to form stable and extended H-bond networks for Pa(V) contrary to U(VI). In particular, prot-actinyl is found to have between 2 and 3 hydrogen bonds per oxygen atom while uranyl has between zero and one. (authors)
Laboratory flow experiments for visualizing carbon dioxide-induced, density-driven brine convection
Energy Technology Data Exchange (ETDEWEB)
Kneafsey, T.; Pruess, K.
2009-09-01
Injection of carbon dioxide (CO{sub 2}) into saline aquifers confined by low-permeability cap rock will result in a layer of CO{sub 2} overlying the brine. Dissolution of CO{sub 2} into the brine increases the brine density, resulting in an unstable situation in which more-dense brine overlies less-dense brine. This gravitational instability could give rise to density-driven convection of the fluid, which is a favorable process of practical interest for CO{sub 2} storage security because it accelerates the transfer of buoyant CO{sub 2} into the aqueous phase, where it is no longer subject to an upward buoyant drive. Laboratory flow visualization tests in transparent Hele-Shaw cells have been performed to elucidate the processes and rates of this CO{sub 2} solute-driven convection (CSC). Upon introduction of CO{sub 2} into the system, a layer of CO{sub 2}-laden brine forms at the CO{sub 2}-water interface. Subsequently, small convective fingers form, which coalesce, broaden, and penetrate into the test cell. Images and time-series data of finger lengths and wavelengths are presented. Observed CO{sub 2} uptake of the convection system indicates that the CO{sub 2} dissolution rate is approximately constant for each test and is far greater than expected for a diffusion-only scenario. Numerical simulations of our system show good agreement with the experiments for onset time of convection and advancement of convective fingers. There are differences as well, the most prominent being the absence of cell-scale convection in the numerical simulations. This cell-scale convection observed in the experiments is probably initiated by a small temperature gradient induced by the cell illumination.
Emission, Structure and Optical Properties of Overfire Soot from Buoyant Turbulent Diffusion Flames
Koylu, Umit Ozgur
The present study investigated soot and carbon monoxide emissions, and evaluated the optical properties of soot, in the overfire region of buoyant turbulent diffusion flames burning in still air. Soot and carbon monoxide emissions, and the corresponding correlation between these emissions, were studied experimentally. The optical properties of soot were investigated both experimentally and theoretically. The experiments involved gas (acetylene, propylene, ethylene, propane, methane) and liquid (toluene, benzene, n-heptane, iso-propanol, ethanol, methanol) fuels. The investigation was limited to the fuel-lean (overfire) region of buoyant turbulent diffusion flames burning in still air. Measurements included flame heights, characteristic flame residence times, carbon monoxide and soot concentrations, mixture fractions, ex-situ soot structure parameters (primary particle sizes, number of primary particles in aggregates, fractal dimensions), and in-situ optical cross sections (differential scattering, total scattering, and absorption) of soot in the overfire region of buoyant turbulent diffusion flames, emphasizing conditions in the long residence time regime where these properties are independent of position in the overfire region and flame residence time. The predictions of optical cross sections for polydisperse aggregates were based on Rayleigh-Debye-Gans theory for fractal aggregates; the predictions of this theory were evaluated by combining the TEM structure and the light scattering/extinction measurements. Carbon monoxide concentrations and mixture fractions were correlated in the overfire region of gas- and liquid -fueled turbulent diffusion flames. Soot volume fraction state relationships were observed for liquid fuels, supporting earlier observations for gas fuels. A strong correlation between carbon monoxide and soot concentrations was established in the fuel-lean region of both gas- and liquid-fueled turbulent diffusion flames. The structure and emission
Buoyant Response of the Tank 241-SY-101 Crust to Transfer and Back-Dilution
International Nuclear Information System (INIS)
The mixer pump installed in Hanford Tank 241-SY-101 (SY-101) in July 1993 has prevented the large buoyant displacement gas release events (BD GRE) it has historically exhibited. But the absence of periodic disruption from GREs and the action of mixing have allowed the crust to grow. The accelerated gas retention has resulted in over 30 inches of waste level growth and the flammable gas volume stored in the crust has become a hazard. To remediate gas retention in the crust and the potential for buoyant displacement gas releases from below the crust, SY-101 will be diluted in the fall of 1999 to dissolve a large fraction of the solids in the tank. The plan is to transfer waste out and back-dilute with water in several steps of about 100,000 gallons each. Back-dilution water may be added at the transfer pump inlet, the base of the mixer pump, and on top of the crust. The mixer pump will continue to be required to prevent formation of a deep nonconnective layer and resumption of BD GREs. Therefore, it is vital to ensure that the transfer and back-dilution processes do not significantly degrade the pump's effectiveness. Part of the strategy to avoid mixer pump degradation is to keep the base of the crust layer well above the pump inlet, which is 236 inches above the tank bottom. The maximum transfer for which an equal back-dilution is possible without sinking the crust is 90 kgal if water is injected at the 96-inch transfer pump inlet and 120 kgal for injection at the 9-inch mixer pump burrowing ring. To keep the crust base above the lowest observed elevation of 295 inches, transfer and back-dilution must be limited to 143 kgal and 80 kgal, respectively, for the 96-inch back-dilution and 175 kgal with a 112 kgal back-dilution using the 9-inch back-dilution elevation. These limits can be avoided by adding water to the top of the crust to dissolve the negatively buoyant layers. If 20 kgal of water is placed on top of the crust and the rest of the back-dilution is placed
Buoyant Response of the Tank 241-SY-101 Crust to Transfer and Back-Dilution
Energy Technology Data Exchange (ETDEWEB)
CW Stewart
1999-11-08
The mixer pump installed in Hanford Tank 241-SY-101 (SY-101) in July 1993 has prevented the large buoyant displacement gas release events (BD GRE) it has historically exhibited. But the absence of periodic disruption from GREs and the action of mixing have allowed the crust to grow. The accelerated gas retention has resulted in over 30 inches of waste level growth and the flammable gas volume stored in the crust has become a hazard. To remediate gas retention in the crust and the potential for buoyant displacement gas releases from below the crust, SY-101 will be diluted in the fall of 1999 to dissolve a large fraction of the solids in the tank. The plan is to transfer waste out and back-dilute with water in several steps of about 100,000 gallons each. Back-dilution water may be added at the transfer pump inlet, the base of the mixer pump, and on top of the crust. The mixer pump will continue to be required to prevent formation of a deep nonconnective layer and resumption of BD GREs. Therefore, it is vital to ensure that the transfer and back-dilution processes do not significantly degrade the pump's effectiveness. Part of the strategy to avoid mixer pump degradation is to keep the base of the crust layer well above the pump inlet, which is 236 inches above the tank bottom. The maximum transfer for which an equal back-dilution is possible without sinking the crust is 90 kgal if water is injected at the 96-inch transfer pump inlet and 120 kgal for injection at the 9-inch mixer pump burrowing ring. To keep the crust base above the lowest observed elevation of 295 inches, transfer and back-dilution must be limited to 143 kgal and 80 kgal, respectively, for the 96-inch back-dilution and 175 kgal with a 112 kgal back-dilution using the 9-inch back-dilution elevation. These limits can be avoided by adding water to the top of the crust to dissolve the negatively buoyant layers. If 20 kgal of water is placed on top of the crust and the rest of the back-dilution is
Shukla, Manoj K.; Leszczynski, Jerzy
2010-11-01
A comprehensive analysis of the performance of the TD-DFT method using different density functionals including recently developed medium and long-range correlation corrected density functionals have been carried out for lower-lying electronic singlet valence transitions of nucleic acid bases and the Watson-Crick base pairs in the gas phase and in the water solution. The standard 6-311++G(d,p) basis set was used. Ground state geometries of bases and base pairs were optimized at the M05-2X/6-311++G(d,p) level. The nature of potential energy surfaces (PES) was ascertained through the harmonic vibrational frequency analysis; all geometries were found to be minima at the respective PES. Electronic singlet vertical transition energies were also computed at the CC2/def2-TZVP level in the gas phase. The effect of state-specific water solvation on TD-DFT computed transition energies was considered using the PCM model. For the isolated bases the performance of the B3LYP functional was generally found to be superior among all functionals, but it measurably fails for charge-transfer states in the base pairs. The CC2/def2-TZVP computed transition energies were also revealed to be inferior compared with B3LYP results for the isolated bases. The performance of the ωB97XD, CAM-B3LYP and BMK functionals were found to be similar and comparable with the CC2 results for the isolated bases. However, for the Watson-Crick adenine-thymine and guanine-cytosine base pairs the performance of the ωB97XD functional was found to be the best among all the studied functionals in the present work in predicting the locally excited transitions as well as charge transfer states.
Egorov, Sergei A; Milchev, Andrey; Virnau, Peter; Binder, Kurt
2016-06-14
Semiflexible polymers in solution are studied for a wide range of both contour length L and persistence length lp as a function of monomer concentration under good solvent conditions. Both density-functional theory (DFT) and molecular dynamics (MD) simulation methods are used, and a very good agreement between both techniques is observed for rather stiff polymers. Evidence for a new mechanism of order parameter fluctuations in the nematic phase is presented, namely collective deformations of bundles of wormlike chains twisted around each other, and the typical wavelengths and amplitudes of these modes are estimated. These long wavelength fluctuations cause a reduction of the order parameter in comparison with the DFT prediction. It is also found that DFT becomes unreliable for rather flexible polymers in predicting that the transition from the isotropic (I)-phase to the nematic (N)-phase still exists at very high monomer concentrations (which in reality does not occur). However, under conditions when DFT is accurate, it provides reliable predictions also for the width of the I-N two-phase coexistence region, which are difficult to obtain from MD in spite of the use of very large systems (up to 500 000 monomers) by means of graphics processing units (GPU). For short and not very stiff chains, a pre-transitional chain stretching is found in the isotropic phase near the I-N-transition, not predicted by theories. A comparison with theoretical predictions by Khokhlov-Semenov, Odijk, and Chen reveals that the scaled transition densities are not simply functions of L/lp only, as these theories predict, but depend on d/lp (where d is the chain diameter) as well. Chain properties in the nematically ordered phase are compared to those of chains confined in tubes, and the deflection length concept is tested. Eventually, some consequences for the interpretation of experiments are spelled out. PMID:27249320
Wind tunnel model experiments on a buoyant emission from a building
International Nuclear Information System (INIS)
The report describes wind tunnel model experiments of a preliminary nature on a leak of buoyant gas from the face of a building, the intention being to reproduce some facets of one kind of catastrophic reactor failure. The measurements covered heat release rates of 1 to 100 MW over a windspeed range of 1 to 10 ms-1. Measurements were made of ground level concentrations of the released gas downwind of the building, together with a limited number of vertical concentration measurements. Results of the experiments showed that ground level concentrations were mainly determined by plume buoyancy; the point of emission on the building, or even the presence of the building having only a secondary effect. (author)
Lorenz, Ralph D.; Sotzen, Kristin S.
2014-01-01
Objective. Landers on Mars and Titan may have warm surfaces as a result of solar heating or the carriage of radioisotope power sources. This warmth can perturb downwind meteorological measurements, but cannot be modeled as a simple aerodynamic wake because buoyant forces can be significant. Methods. We use an analytic model from the industrial aerodynamics literature on smoke dispersion from fires and smokestacks to evaluate the plume trajectories. Computational Fluid Dynamics (CFD) simulations are also performed for a Titan lander. Results. CFD yields results similar to the analytic model. (Albeit with a possibly weaker dependence on windspeed than the classic model.) We apply the models to evaluate the probability of immersion of instrumentation in plumes from the Mars Science Laboratory (MSL) Curiosity and for a Titan lander under various wind scenarios. Conclusions. Lander perturbations can be easily calculated. Practice implications. None.
Under-Liquid Self-Assembly of Submerged Buoyant Polymer Particles.
Multanen, Victor; Pogreb, Roman; Bormashenko, Yelena; Shulzinger, Evgeny; Whyman, Gene; Frenkel, Mark; Bormashenko, Edward
2016-06-14
The self-assembly of submerged cold-plasma-treated polyethylene beads (PBs) is reported. The plasma-treated immersed millimetrically sized PBs formed well-ordered 2D quasicrystalline structures. The submerged floating of "light" (buoyant) PBs is possible because of the energy gain achieved by the wetting of the high-energy plasma-treated polymer surface prevailing over the energy loss due to the upward climb of the liquid over the beads. The capillary "immersion" attraction force is responsible for the observed self-assembly. The observed 2D quasicrystalline structures demonstrate "dislocations" and "point defects". The mechanical vibration of self-assembled rafts built of PBs leads to the healing of point defects. The immersion capillary lateral force governs the self-assembly, whereas the elastic force is responsible for the repulsion of polymer beads. PMID:27193509
Three-dimensional Magnetohydrodynamic Simulations of Buoyant Bubbles in Galaxy Clusters
O'Neill, S M; Jones, T W
2009-01-01
We report results of 3D MHD simulations of the dynamics of buoyant bubbles in magnetized galaxy cluster media. The simulations are three dimensional extensions of two dimensional calculations reported by Jones & De Young (2005). Initially spherical bubbles and briefly inflated spherical bubbles all with radii a few times smaller than the intracluster medium (ICM) scale height were followed as they rose through several ICM scale heights. Such bubbles quickly evolve into a toroidal form that, in the absence of magnetic influences, is stable against fragmentation in our simulations. This ring formation results from (commonly used) initial conditions that cause ICM material below the bubbles to drive upwards through the bubble, creating a vortex ring; that is, hydrostatic bubbles develop into "smoke rings", if they are initially not very much smaller or very much larger than the ICM scale height. Even modest ICM magnetic fields with beta = P_gas/P_mag ~ 10^3 can influence the dynamics of the bubbles, provided...
Buoyant Bubbles in Intracluster Gas: Effects of Magnetic Fields and Anisotropic Viscosity
Dong, Ruobing
2009-01-01
Recent observations by Chandra and XMM-Newton indicate there are complex structures at the cores of galaxy clusters, such as cavities and filaments. One plausible model for the formation of such structures is the interaction of radio jets with the intracluster medium (ICM). To investigate this idea, we use three-dimensional magnetohydrodynamic simulations including anisotropic (Braginskii) viscosity to study the effect of magnetic fields on the evolution and morphology of buoyant bubbles in the ICM. We investigate a range of different initial magnetic field geometries and strengths, and study the resulting x-ray surface brightness distribution for comparison to observed clusters. Magnetic tension forces and viscous transport along field lines tend to suppress instabilities parallel, but not perpendicular, to field lines. Thus, the evolution of the bubble depends strongly on the initial field geometry. We find toroidal field loops initially confined to the interior of the bubble are best able reproduce the obs...
Finite-size effects in the dynamics of neutrally buoyant particles in turbulent flow
Homann, Holger
2009-01-01
The dynamics of neutrally buoyant particles transported by a turbulent flow is investigated for spherical particles with radii of the order of the Kolmogorov dissipative scale or larger. The pseudo-penalisation spectral method that has been proposed by Pasquetti et al. (2008) is adapted to integrate numerically the simultaneous dynamics of the particle and of the fluid. Such a method gives a unique handle on the limit of validity of point-particle approximations, which are generally used in applicative situations. Analytical predictions based on such models are compared to result of very well resolved direct numerical simulations. Evidence is obtained that Faxen corrections give dominant finite-size corrections to velocity and acceleration fluctuations for particle diameters up to four times the Kolmogorov scale. The dynamics of particles with larger diameters is dominated by inertial-range physics, and is consistent with predictions obtained from dimensional analysis.
Dynamics of single rising bubbles in neutrally buoyant liquid-solid suspensions.
Hooshyar, Nasim; van Ommen, J Ruud; Hamersma, Peter J; Sundaresan, Sankaran; Mudde, Robert F
2013-06-14
We experimentally investigate the effect of particles on the dynamics of a gas bubble rising in a liquid-solid suspension while the particles are equally sized and neutrally buoyant. Using the Stokes number as a universal scale, we show that when a bubble rises through a suspension characterized by a low Stokes number (in our case, small particles), it will hardly collide with the particles and will experience the suspension as a pseudoclear liquid. On the other hand, when the Stokes number is high (large particles), the high particle inertia leads to direct collisions with the bubble. In that case, Newton's collision rule applies, and direct exchange of momentum and energy between the bubble and the particles occurs. We present a simple theory that describes the underlying mechanism determining the terminal bubble velocity. PMID:25165930
Translational and rotational dynamics of a large buoyant sphere in turbulence
Mathai, Varghese; van der Poel, Erwin P; Sun, Chao
2016-01-01
We report experimental measurements of the translational and rotational dynamics of a large buoyant sphere in isotropic turbulence. We introduce an efficient method to simultaneously determine the position and (absolute) orientation of a spherical body from visual observation. The method employs a minimization algorithm to obtain the orientation from the 2D projection of a specific pattern drawn onto the surface of the sphere. This has the advantages that it does not require a database of reference images, is easily scalable using parallel processing, and enables accurate absolute orientation reference. Analysis of the sphere's translational dynamics reveals clear differences between the streamwise and transverse directions. The translational auto-correlations and PDFs provide evidence for periodicity in the particle's dynamics even under turbulent conditions. The angular autocorrelations show weak periodicity. The angular accelerations exhibit wide tails, however without a directional dependence.
Biferale, Luca; Verzicco, Roberto
2014-01-01
Small droplets in turbulent flows can undergo highly variable deformations and orientational dynamics. For neutrally buoyant droplets smaller than the Kolmogorov scale, the dominant effects from the surrounding turbulent flow arise through Lagrangian time histories of the velocity gradient tensor. Here we study the evolution of representative droplets using a model that includes rotation and stretching effects from the surrounding fluid, and restoration effects from surface tension including a constant droplet volume constraint, while assuming that the droplets maintain an ellipsoidal shape. The model is combined with Lagrangian time histories of the velocity gradient tensor extracted from DNS of turbulence to obtain simulated droplet evolutions. These are used to characterize the size, shape and orientation statistics of small droplets in turbulence. A critical capillary number, $Ca_c$ is identified associated with unbounded growth of one or two of the droplet's semi-axes. Exploiting analogies with dynamics ...
Flow instability of buoyant-Marangoni convection in the LEC GaAs melt
Institute of Scientific and Technical Information of China (English)
CHEN ShuXian; LI MingWei
2008-01-01
Flow transitions and instabilities have significant effects on the quality of the crystals. The flow and heat transfer in the LEC GaAs melt are numerically studied by a time-dependent and three-dimensional turbulent flow model. The effects of the change of the buoyancy and Marangoni force on the flow state are analyzed by changing the temperature difference between the crystal and the crucible walls. The results show that the flow will transform from axisymmetric steady flow to non-axisymmetric oscillatory flow when the temperature difference exceeds the critical value, and that the mechanism of the transition is attributed to the Marangoni instability. The critical temperature differences for the flow transitions corresponding to different melt depth H are numerically predicted. Several important characteristics of the non-axisymmetric buoyant-Marangoni convection are numerically observed and compared with that of the non-axisymmetric mixed convection coupled with crystal rotation.
Caserta, A; Salusti, E
2016-01-01
In this paper we propose the application of a new model of transients of pore pressure p and solute density \\r{ho} in geologic porous media. This model is rooted in the non-linear waves theory, the focus of which is advection and effect of large pressure jumps on strain (due to large p in a non-linear version of the Hooke law). It strictly relates p and \\r{ho} evolving under the effect of a strong external stress. As a result, the presence of quick and sharp transients in low permeability rocks is unveiled, i.e. the non-linear Burgers solitons. We therefore propose that the actual transport process in porous rocks for large signals is not the linear diffusion, but could be governed by solitons. A test of an eventual presence of solitons in a rock is here proposed, and then applied to Pierre Shale, Bearpaw Shale, Boom Clay and Oznam-Mugu silt and clay. A quick analysis showing the presence of solitons for nuclear waste disposal and salty water intrusions is also analyzed. Finally, in a kind of "theoretical exp...
Lian, Zhipeng; Yan, Qingfeng; Gao, Taotao; Ding, Jie; Lv, Qianrui; Ning, Chuangang; Li, Qiang; Sun, Jia-Lin
2016-08-01
Single crystal reflects the intrinsic physical properties of a material, and single crystals with high-crystalline quality are highly desired for the acquisition of high-performance devices. We found that large single crystals of perovskite CH3NH3PbI3(Cl) could be grown rapidly from chlorine-containing solutions. Within 5 days, CH3NH3PbI3(Cl) single crystal as large as 20 mm × 18 mm × 6 mm was harvested. As a most important index to evaluate the crystalline quality, the full width at half-maximum (fwhm) in the high-resolution X-ray rocking curve (HR-XRC) of as-grown CH3NH3PbI3(Cl) single crystal was measured as 20 arcsec, which is far superior to so far reported CH3NH3PbI3 single crystals (∼1338 arcsec). The unparalleled crystalline quality delivered a low trap-state density of down to 7.6 × 10(8) cm(-3), high carrier mobility of 167 ± 35 cm(2) V(-1) s(-1), and long transient photovoltaic carrier lifetime of 449 ± 76 μs. The improvement in the crystalline quality, together with the rapid growth rate and excellent carrier transport property, provides state-of-the-art single crystalline hybrid perovskite materials for high-performance optoelectronic devices. PMID:27458057
Dehghani, Mehdi; Behjat, Abbas; Tajabadi, Fariba; Taghavinia, Nima
2015-03-01
Planar superstrate CuInS2 (CIS) solar cell devices are fabricated using totally solution-processed deposition methods. These Cd-free devices are structured by FTO/TiO2/In2S3/CIS/carbon, where TiO2 and In2S3 are deposited by spray pyrolysis, and a CIS film is deposited using spin-coating followed by annealing at 250 °C. The pasted carbon layer is utilized as the anode. No further sulfurization or selenization is employed. The Cu/In ratio in the ink is found as a critical factor affecting the morphology and crystallinity of the film as well as the photovoltaic performance of the device. An optimum Cu/In = 1.05 results in large-grain films with sharp diffraction peaks and, subsequently, optimal series resistance and shunt conductance. It is also found that the chloride-based ink results in CIS films with considerably reduced metastable phases, compared to the conventional acetate-based inks. A current density of 23.6 mA cm-2 is obtained for the best devices, leading to a conversion efficiency of 4.1%.
Hancock, Robert D; Bartolotti, Libero J
2005-10-01
A prediction of the formation constants (log K1) for complexes of metal ions with a single NH3 ligand in aqueous solution, using quantum mechanical calculations, is reported. DeltaG values at 298 K in the gas phase for eq 1 (DeltaG(DFT)) were calculated for 34 metal ions using density functional theory (DFT), with the expectation that these would correlate with the free energy of complex formation in aqueous solution (DeltaG(aq)). [M(H2O)6]n+(g) + NH(3)(g) = [M(H2O)5NH3]n+(g) + H2O(g) (eq 1). The DeltaG(aq) values include the effects of complex changes in solvation on complex formation, which are not included in eq 1. It was anticipated that such changes in solvation would be constant or vary systematically with changes in the log K(1) value for different metal ions; therefore, simple correlations between DeltaG(DFT) and DeltaG(aq) were sought. The bulk of the log K1(NH3) values used to calculate DeltaG(aq) were not experimental, but estimated previously (Hancock 1978, 1980) from a variety of empirical correlations. Separate linear correlations between DeltaG(DFT) and DeltaG(aq) for metal ions of different charges (M2+, M3+, and M4+) were found. In plots of DeltaG(DFT) versus DeltaG(aq), the slopes ranged from 2.201 for M2+ ions down to 1.076 for M4+ ions, with intercepts increasing from M2+ to M4+ ions. Two separate correlations occurred for the M3+ ions, which appeared to correspond to small metal ions with a coordination number (CN) of 6 and to large metal ions with a higher CN in the vicinity of 7-9. The good correlation coefficients (R) in the range of 0.97-0.99 for all these separate correlations suggest that the approach used here may be the basis for future predictions of aqueous phase chemistry that would otherwise be experimentally inaccessible. Thus, the log K1(NH3) value for the transuranic Lr3+, which has a half-life of 3.6 h in its most stable isotope, is predicted to be 1.46. These calculations should also lead to a greater insight into the factors
International Nuclear Information System (INIS)
Highlights: • A vortex is generated when the buoyant jet impinges the opposite wall linearly. • The vortex height “Zb” is nearly equal to the edge of the temperature gradient layer. • Empirical formulas were proposed between Zb and the buoyant jet’s length scale lM. • A 1D model for simulating temperature distribution was proposed. • The performance of the model was verified by comparing the unsteady test results. -- Abstract: The hot water storage tank (for stratified thermal storage) with a heat pump draws a lot of attention nowadays due to its high performance. In Japan, reheating of the bath is commonly used, and as this mode, the jet injects horizontally at the middle of the tank, so the temperature distribution of the tank changes complexly with time. Hence a model is needed to simulate this phenomenon, precisely. Additionally, in the process of designing a hot water storage system, it is necessary to simulate temperature distribution quickly, since a test run itself is a time consuming process. In this study, visualization experiments were performed using tracer particles and thermo-sensitive liquid crystals. Experiments were also carried out to find the unsteady temperature distribution in a tank when the positively or negatively buoyant jet was injected horizontally in the middle of the tank whose size is limited and has an influence from the opposite wall. If the momentum effect of the buoyant jet is stronger than that of buoyancy, the buoyant jet impinge against the opposite wall of the tank, and a vortex was observed near the opposite wall. Empirical formulas were proposed to predict the height of the vortex “Zb” under various conditions, such as the momentum and the buoyancy of the buoyant jet, and the Prandtl number of the tank water. Furthermore, the 3D-CFD was carried out to supplement the 3D behavior of the inner tank fluid. A one dimensional model, “uniformly distributed injection model”, for simulating temperature
Blandamer, MJ; Buurma, NJ; Engberts, JBFN; Reis, JCR; Buurma, Niklaas J.; Reis, João C.R.
2003-01-01
At temperatures above and below the temperature of maximum density, TMD, for water at ambient pressure, pairs of temperatures exist at which the molar volumes of water are equal. First-order rate constants for the pH-independent hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution at pairs of
2D and 3D numerical models on compositionally buoyant diapirs in the mantle wedge
Hasenclever, Jörg; Morgan, Jason Phipps; Hort, Matthias; Rüpke, Lars H.
2011-11-01
We present 2D and 3D numerical model calculations that focus on the physics of compositionally buoyant diapirs rising within a mantle wedge corner flow. Compositional buoyancy is assumed to arise from slab dehydration during which water-rich volatiles enter the mantle wedge and form a wet, less dense boundary layer on top of the slab. Slab dehydration is prescribed to occur in the 80-180 km deep slab interval, and the water transport is treated as a diffusion-like process. In this study, the mantle's rheology is modeled as being isoviscous for the benefit of easier-to-interpret feedbacks between water migration and buoyant viscous flow of the mantle. We use a simple subduction geometry that does not change during the numerical calculation. In a large set of 2D calculations we have identified that five different flow regimes can form, in which the position, number, and formation time of the diapirs vary as a function of four parameters: subduction angle, subduction rate, water diffusivity (mobility), and mantle viscosity. Using the same numerical method and numerical resolution we also conducted a suite of 3D calculations for 16 selected parameter combinations. Comparing the 2D and 3D results for the same model parameters reveals that the 2D models can only give limited insights into the inherently 3D problem of mantle wedge diapirism. While often correctly predicting the position and onset time of the first diapir(s), the 2D models fail to capture the dynamics of diapir ascent as well as the formation of secondary diapirs that result from boundary layer perturbations caused by previous diapirs. Of greatest importance for physically correct results is the numerical resolution in the region where diapirs nucleate, which must be high enough to accurately capture the growth of the thin wet boundary layer on top of the slab and, subsequently, the formation, morphology, and ascent of diapirs. Here 2D models can be very useful to quantify the required resolution, which we
Niehaus, Justin; Ferkul, Paul V.; Gokoglu, Suleyman; Ruff, Gary
2015-01-01
Flammability experiments on silicone samples were conducted in anticipation of the Spacecraft Fire Experiment (Saffire). The sample geometry was chosen to match the NASA 6001 Test 1 specification, namely 5 cm wide by 30 cm tall. Four thicknesses of silicone (0.25, 0.36, 0.61 and 1.00 mm) were examined. Tests included traditional upward buoyant flame spread using Test 1 procedures, downward opposed flow flame spread, horizontal and angled flame spread, forced flow upward and downward flame spread. In addition to these configurations, upward and downward tests were also conducted in a chamber with varying oxygen concentrations. In the upward buoyant flame spread tests, the flame generally did not burn the entire sample. As thickness was increased, the flame spread distance decreased before flame extinguishment. For the thickest sample, ignition could not be achieved. In the downward tests, the two thinnest samples permitted the flame to burn the entire sample, but the spread rate was lower compared to the corresponding upward values. The other two thicknesses could not be ignited in the downward configuration. The increased flammability for downward spreading flames relative to upward ones is uncommon. The two thinnest samples also burned completely in the horizontal configuration, as well as at angles up to 75 degrees from the horizontal. The upward and downward flammability behavior was compared in atmospheres of varying oxygen concentration to determine a maximum oxygen concentration for each configuration. Upward tests in air with an added forced flow were more flammable. Complementary analyses using SEM and TGA techniques suggest the importance of the silica layer formed on the burned sample surface. As silicone burns upward, silica deposits downstream •If the silicone is ignited in the downward configuration, it burns the entire length of the sample •Burning upward at an angle increases the burn length in some cases possibly due to less silica deposition
Experimental Studies for the characterization of the mixing processes in negative buoyant jets
Directory of Open Access Journals (Sweden)
Querzoli G.
2013-04-01
Full Text Available A negatively buoyant jet (NBJ corresponds to the physical phenomenon that develops when a fluid is discharged upwards into a lighter environment or downwards into a heavier receptor fluid. In a NBJ the flow is initially driven mostly by the momentum, so it basically behaves as a simple jet released withthe same angle, while far from the outlet the buoyancy prevails, bending the jet axis down and making it similar to a plume. The coexistence in the same phenomenon of both the characteristics of simple jets and plumes makes the NBJs a phenomenon still not entirely explained but, considering also the numerous practical applications, very interesting to study. Here some of the experimental results are presented. The laboratory experiment were obtained on a model simulating a typical sea discharge of brine from desalination plants: a pipe laid down on the sea bottom, with orifices on its lateral wall, releasing brine (heavier than the sea water with a certain angle to the horizontal, in order to increase the jet path before sinking to the seafloor. A non-intrusive image analysis technique, namely Feature Tracking Velocimetry, is applied to measure velocity fields, with the aim at understanding the influence of some non-dimensional parameters driving the phenomenon (e.g. Reynolds number, release angle on the structure of the NBJ and of the turbulence.
An EOF analysis of HF Doppler radar current measurements of the Chesapeake Bay buoyant outflow
Marmorino, G. O.; Shay, L. K.; Haus, B. K.; Handler, R. A.; Graber, H. C.; Horne, M. P.
1999-02-01
Surface currents measured by HF Doppler radar as part of a study of the Chesapeake Bay outflow plume are examined using a 'real-vector' empirical orthogonal function (EOF) analysis (Kaihatu et al., 1998). Based on about 23 days of nearly continuous data, the analysis shows that the first three EOF modes, judged to be the only significant modes, account for 76% of the variance in the data set. The buoyant outflow occurs primarily in the mean flow field. The first EOF mode is dominated by wind forcing and the second mode by across-shelf semi-diurnal tidal forcing. The third mode exhibits a large-scale horizontal shear and contains a curved region of weak relative flow which appears to delineate the offshore edge of the plume; also, the third-mode response varies over the spring-neap cycle, suggesting a modulation of the outflow plume by a tidal residual eddy. The analysis therefore has provided a useful, exploratory examination of this dataset of surface currents.
Trace Metal and Sulfur Dynamics in the First Meter of Buoyant Hydrothermal Vent Plumes
Findlay, A.; Gartman, A.; Shaw, T. J.; Luther, G. W., III
2014-12-01
The speciation and reactivity of metals and metal sulfides within the buoyant plume is critical to determining the ultimate fate of metals emitted from hydrothermal vents. The concentration, size fractionation, and partitioning of trace metals (Fe, Mn, Cu, Co, Zn, Cd, Pb) were determined within the first meter of the rising plume at three vent fields (TAG, Snakepit, and Rainbow) along the Mid-Atlantic Ridge. At Rainbow, total Fe concentrations exceed total sulfide concentrations by an order of magnitude, whereas at the other two sites, total Fe and total sulfide concentrations are nearly equal. At all three sites, Mn and Fe are primarily in the filtered (zinc is correlated with unfiltered cadmium and lead. At Rainbow, unfiltered zinc, cadmium and lead are correlated, but unfiltered copper and cobalt are not, indicating precipitation dynamics at Rainbow are different than those at TAG and Snakepit due to bulk geochemical differences, including a higher iron to sulfide ratio. A sequential HCl/HNO3 leaching method was used to distinguish metals present in pyrite and chalcopyrite in both unfiltered and filtered samples. Significant portions of unfiltered Cu and Co were extracted in HNO3, whereas unfiltered Zn, Cd, and Pb were extracted in HCl. Up to 95 % of filtered Cu, Co, and Zn, up to 80% Cd, and up to 60 % Pb are only extractable in HNO3, indicating that a significant portion of metals < 0.2 μm are incorporated into a recalcitrant fraction such as nanoparticulate pyrite or chalcopyrite.
The negatively buoyant turbulent wall jet: performance of alternative options in RANS modelling
International Nuclear Information System (INIS)
The paper describes the application of different levels of turbulence closure and near-wall treatment to the computation of a 2D downward-directed wall jet that encounters a slow, upward-moving flow. The working fluid is water and the two streams may be at the same temperature or the wall-jet fluid may be hotter, leading to significant buoyant effects. The distance of penetration of the wall jet is found to be highly dependent on the turbulence model employed. It is established first that the new analytical wall function (AWF) developed by the authors [Int. J. Heat Fluid Flow 23 (2002) 148] leads to flow predictions in close agreement with a so-called 'low-Reynolds-number' treatment where computations extend all the way to the wall. However, for some test cases, both sets of calculations (employing an eddy-viscosity model) indicate too great a penetration of the wall-jet into the opposing stream. The use of the AWF in conjunction with a second-moment closure, particularly one which satisfies the two-component-limit, gives generally closer agreement
Magnetic Cycles and Buoyant Magnetic Structures in a Rapidly Rotating Sun
Nelson, Nicholas J.; Brown, B. P.; Brun, S.; Miesch, M. S.; Toomre, J.
2011-01-01
Observations of sun-like stars rotating faster than our current sun show that they exhibit solar-like magnetic cycles and features, such as star spots. Using global 3-D simulations to study the coupling of large-scale convection, rotation, and magnetism in a younger sun, we have probed the effects of more rapid rotation on stellar dynamos and the nature of magnetic cycles. Our anelastic spherical harmonics (ASH) code allows study of the convective envelope, occupying the outer 30% by radius of a sun-like star. Major MHD simulations carried out at three times the current solar rotation rate reveal magnetic dynamo action that can produce wreaths of strong toroidal magnetic field at low latitudes, often with opposite polarity in the two hemispheres. The presence of the wreaths is quite surprising, for they arise as quite persistent global structures amidst the vigorous and turbulent convection. We have recently explored behavior in systems with considerably lower diffusivities, achieved with a dynamic Smagorinsky treatment of unresolved turbulence. The lower levels of diffusion create magnetic wreaths that undergo prominent variations in field strength, even exhibiting global magnetic cycles that involve polarity reversals. Additionally, during the cycle maximum, when magnetic energies and mean magnetic fields peak, the wreaths possess buoyant magnetic structures that rise coherently through much of the convective envelope via a combination of advection by convective upflows and magnetic buoyancy. We explore aspects of these rising magnetic structures and the evolving global dynamo action which produces them.
A corrected vortex blob method for 3D thermal buoyant flows
Energy Technology Data Exchange (ETDEWEB)
Golia, Carmine; Buonomo, Bernardo; Viviani, Antonio [Seconda Universita di Napoli (SUN), Dipartimento di Ingegneria Aerospaziale e Meccanica (DIAM), via Roma 29, 81031 Aversa (Italy)
2008-11-15
This work explores novel ideas to improve the accuracy of integral approximation to differential operators (divergence, gradient and Laplacian) in the simulation of 3D thermal buoyant flows with meshless Lagrangian Blobs methods. Basically, we investigate and develop an integral discretization of the differential operators of the field equations, by using convolutions of truncated 3D-Taylor series expansions with a kernel function defined on a compact support around the blob centre of a given particle. This allows to overtake: circle the irregular distribution of cells in the compact support around the given blob, circle the deficiency of cells in the compact support due to the presence of a boundary cutting the compact support of nearby blobs. The accuracy and the order of approximation of such discretizations are determined in regular and randomly distorted grids of various sizes, and compared with the widely used particle strength exchange formulations. The analysis of the effects of using the new formulations to solve problems at realistic values of the Grashof number demonstrates the validity and the benefits of the novel findings. (author)
An inkjet-printed buoyant 3-D lagrangian sensor for real-time flood monitoring
Farooqui, Muhammad Fahad
2014-06-01
A 3-D (cube-shaped) Lagrangian sensor, inkjet printed on a paper substrate, is presented for the first time. The sensor comprises a transmitter chip with a microcontroller completely embedded in the cube, along with a $1.5 \\\\lambda 0 dipole that is uniquely implemented on all the faces of the cube to achieve a near isotropic radiation pattern. The sensor has been designed to operate both in the air as well as water (half immersed) for real-time flood monitoring. The sensor weighs 1.8 gm and measures 13 mm$\\\\,\\\\times\\\\,$ 13 mm$\\\\,\\\\times\\\\,$ 13 mm, and each side of the cube corresponds to only $0.1 \\\\lambda 0 (at 2.4 GHz). The printed circuit board is also inkjet-printed on paper substrate to make the sensor light weight and buoyant. Issues related to the bending of inkjet-printed tracks and integration of the transmitter chip in the cube are discussed. The Lagrangian sensor is designed to operate in a wireless sensor network and field tests have confirmed that it can communicate up to a distance of 100 m while in the air and up to 50 m while half immersed in water. © 1963-2012 IEEE.
Isolation of rare tumor cells from blood cells with buoyant immuno-microbubbles.
Directory of Open Access Journals (Sweden)
Guixin Shi
Full Text Available Circulating tumor cells (CTCs are exfoliated at various stages of cancer, and could provide invaluable information for the diagnosis and prognosis of cancers. There is an urgent need for the development of cost-efficient and scalable technologies for rare CTC enrichment from blood. Here we report a novel method for isolation of rare tumor cells from excess of blood cells using gas-filled buoyant immuno-microbubbles (MBs. MBs were prepared by emulsification of perfluorocarbon gas in phospholipids and decorated with anti-epithelial cell adhesion molecule (EpCAM antibody. EpCAM-targeted MBs efficiently (85% and rapidly (within 15 minutes bound to various epithelial tumor cells suspended in cell medium. EpCAM-targeted MBs efficiently (88% isolated frequent tumor cells that were spiked at 100,000 cells/ml into plasma-depleted blood. Anti-EpCAM MBs efficiently (>77% isolated rare mouse breast 4T1, human prostate PC-3 and pancreatic cancer BxPC-3 cells spiked into 1, 3 and 7 ml (respectively of plasma-depleted blood. Using EpCAM targeted MBs CTCs from metastatic cancer patients were isolated, suggesting that this technique could be developed into a valuable clinical tool for isolation, enumeration and analysis of rare cells.
Turbulent channel flow of dense suspensions of neutrally-buoyant spheres
Picano, F; Brandt, L
2014-01-01
Dense particle suspensions are widely encountered in many applications and in environmental flows. While many previous studies investigate their rheological properties in laminar flows, little is known on the behaviour of these suspensions in the turbulent/inertial regime. The present study aims to fill this gap by investigating the turbulent flow of a Newtonian fluid laden with solid neutrally-buoyant spheres at relatively high volume fractions in a plane channel. An Immersed Boundary Method has been used to account for the dispersed phase performing Direct Numerical Simulation in the range of volume fractions $\\Phi=0-0.2$. The results show that the mean velocity profiles are significantly altered by the presence of a solid phase with a decrease of the von K\\'arm\\'an constant in the log-law. The overall drag is found to increase with the volume fraction, more than one would expect just considering the increase of the system viscosity due to the presence of the particles. At the highest volume fraction here i...
Numerical simulation and analysis of confined turbulent buoyant jet with variable source
El-Amin, Mohamed
2016-01-23
In this work, experimental and numerical investigations are undertaken for confined buoyant turbulent jet with varying inlet temperatures. Results of the experimental work and numerical simulations for the problem under consideration are presented. Four cases of different variable inlet temperatures and different flow rates are considered. The realizable k-ɛ turbulence model is used to model the turbulent flow. Comparisons show good agreements between simulated and measured results. The average deviation of the simulated temperature by realizable k-ɛ turbulent model and the measured temperature is within 2%. The results indicate that temperatures along the vertical axis vary, generally, in nonlinear fashion as opposed to the approximately linear variation that was observed for the constant inlet temperature that was done in a previous work. Furthermore, thermal stratification exits, particularly closer to the entrance region. Further away from the entrance region the variation in temperatures becomes relatively smaller. The stratification is observed since the start of the experiment and continues during the whole course. Numerical experiments for constant, monotone increasing and monotone decreasing of inlet temperature are done to show its effect on the buoyancy force in terms of Richardson number.
Numerical simulation of 2D buoyant jets in ice-covered and temperature-stratified water
Gu, Ruochuan
A two-dimensional (2D) unsteady simulation model is applied to the problem of a submerged warm water discharge into a stratified lake or reservoir with an ice cover. Numerical simulations and analyses are conducted to gain insight into large-scale convective recirculation and flow processes in a cold waterbody induced by a buoyant jet. Jet behaviors under various discharge temperatures are captured by directly modeling flow and thermal fields. Flow structures and processes are described by the simulated spatial and temporal distributions of velocity and temperature in various regions: deflection, recirculation, attachment, and impingement. Some peculiar hydrothermal and dynamic features, e.g. reversal of buoyancy due to the dilution of a warm jet by entraining cold ambient water, are identified and examined. Simulation results show that buoyancy is the most important factor controlling jet behavior and mixing processes. The inflow boundary is treated as a liquid wall from which the jet is offset. Similarity and difference in effects of boundaries perpendicular and parallel to flow, and of buoyancy on jet attachment and impingement, are discussed. Symmetric flow configuration is used to de-emphasize the Coanda effect caused by offset.
International Nuclear Information System (INIS)
Highlights: • We assess the coolant mixing in the RPV downcomer and the core lower plenum under buoyant asymmetric conditions. • We evaluate the capabilities of the thermal-hydralic system computer codes to simulate such phenomenon. • We considered the PKL2-ROCOM T1.1 and T2.1 experimental tests. • We used the 3D features of the CATHARE thermal-hydraulic system code to simulate the experiments. • Acceptable prediction of the buoyant mixing in the downcomer is obtained. - Abstract: Coolant mixing in the reactor vessel of a pressurized water reactor constitutes a key parameter for predicting the core behaviour under abnormal asymmetric cooling conditions. This issue was recently investigated within the experimental framework of the OECD/PKL-2 project. The aim was twofold: to assess the coolant mixing in the vessel downcomer and the core lower plenum under buoyant asymmetric cooling loops, as well as to evaluate the capabilities of computer codes in simulating such phenomenon. It is commonly known that CFD codes are applied for this objective using millions of nodes and large computer resources. However, thermal-hydraulic system codes having the 3D vessel models could also be considered for such purpose. Indeed, these codes benefit from large validation background, require less computational resources and include 3D capabilities that are up to now not fully exploited. In this framework the CATHARE 3D models are assessed against two asymmetrical buoyant mixing experimental tests performed at the ROCOM facility. The outcomes of the current study show good prediction potentialities of the 3D thermal-hydraulic system codes. However their applicability to NPP scale has to be further investigated experimentally and analytically as well
Energy Technology Data Exchange (ETDEWEB)
Bousbia Salah, Anis, E-mail: anis.bousbiasalah@belv.be; Vlassenbroeck, Jacques
2013-12-15
Highlights: • We assess the coolant mixing in the RPV downcomer and the core lower plenum under buoyant asymmetric conditions. • We evaluate the capabilities of the thermal-hydralic system computer codes to simulate such phenomenon. • We considered the PKL2-ROCOM T1.1 and T2.1 experimental tests. • We used the 3D features of the CATHARE thermal-hydraulic system code to simulate the experiments. • Acceptable prediction of the buoyant mixing in the downcomer is obtained. - Abstract: Coolant mixing in the reactor vessel of a pressurized water reactor constitutes a key parameter for predicting the core behaviour under abnormal asymmetric cooling conditions. This issue was recently investigated within the experimental framework of the OECD/PKL-2 project. The aim was twofold: to assess the coolant mixing in the vessel downcomer and the core lower plenum under buoyant asymmetric cooling loops, as well as to evaluate the capabilities of computer codes in simulating such phenomenon. It is commonly known that CFD codes are applied for this objective using millions of nodes and large computer resources. However, thermal-hydraulic system codes having the 3D vessel models could also be considered for such purpose. Indeed, these codes benefit from large validation background, require less computational resources and include 3D capabilities that are up to now not fully exploited. In this framework the CATHARE 3D models are assessed against two asymmetrical buoyant mixing experimental tests performed at the ROCOM facility. The outcomes of the current study show good prediction potentialities of the 3D thermal-hydraulic system codes. However their applicability to NPP scale has to be further investigated experimentally and analytically as well.
Huang, Shih-Lin; Pan, Tsorng-Whay; Chang, Chien-Cheng; Chu, Chin-Chou
2014-01-01
In this paper, we investigate the motion of a neutrally buoyant cylinder of an elliptic shape freely moving in two dimensional shear flow by direct numerical simulation. An elliptic shape cylinder in shear flow, when initially being placed at the middle between two walls, either keeps rotating or has a stationary inclination angle depending on the particle Reynolds number $Re=G_r r_a^2/\
Mauro, Marco; Battaglia, Raffaele; Ferrini, Gianluca; Puglisi, Roberto; Balduzzi, Donatella; Galli, Andrea
2014-03-01
Flow cytometry is to date the only commercially viable technique for sex preselection of mammalian spermatozoa, measuring the different DNA content in X- and Y-chromosome bearing spermatozoa. Here we present experimental evidence of a measurable difference between bovine spermatozoa bearing X- and Y-chromosomes based on their buoyant mass. Single cells of two populations of flow-cytometrically sorted spermatozoa were analyzed by means of a micromechanical resonator, consisting of a suspended doubly-clamped microcapillary. Spermatozoa buoyant mass is related to the transitory variation in vibration phase lag, caused by the passage through the sensitive area of a single sperm cell suspended in a fluid. Data analysis shows two well-separated distributions and provides evidence of the sensor capabilities to detect the buoyant mass of single cells with such accuracy to distinguish X- and Y-chromosome bearing spermatozoa. These preliminary results suggest the possibility to develop an intriguing technique alternative to flow cytometry in the field of sperm sorting. PMID:24419052
Fraser, Ceridwen I; Zuccarello, Giuseppe C; Spencer, Hamish G; Salvatore, Laura C; Garcia, Gabriella R; Waters, Jonathan M
2013-01-01
Marine biologists and biogeographers have long been puzzled by apparently non-dispersive coastal taxa that nonetheless have extensive transoceanic distributions. We here carried out a broad-scale phylogeographic study to test whether two widespread Southern Hemisphere species of non-buoyant littoral macroalgae are capable of long-distance dispersal. Samples were collected from along the coasts of southern Chile, New Zealand and several subAntarctic islands, with the focus on high latitude populations in the path of the Antarctic Circumpolar Current or West Wind Drift. We targeted two widespread littoral macroalgal species: the brown alga Adenocystisutricularis (Ectocarpales, Heterokontophyta) and the red alga Bostrychiaintricata (Ceramiales, Rhodophyta). Phylogenetic analyses were performed using partial mitochondrial (COI), chloroplast (rbcL) and ribosomal nuclear (LSU / 28S) DNA sequence data. Numerous deeply-divergent clades were resolved across all markers in each of the target species, but close phylogenetic relationships - even shared haplotypes - were observed among some populations separated by large oceanic distances. Despite not being particularly buoyant, both Adenocystisutricularis and Bostrychiaintricata thus show genetic signatures of recent dispersal across vast oceanic distances, presumably by attachment to floating substrata such as wood or buoyant macroalgae. PMID:23894421
Energy Technology Data Exchange (ETDEWEB)
Janak, Jill M.; Brown, Richard S.; Colotelo, Alison HA; Pflugrath, Brett D.; Stephenson, John R.; Deng, Zhiqun; Carlson, Thomas J.; Seaburg, Adam
2012-08-01
The presence of an externally attached telemetry tag is often associated with the potential for impaired swimming performance (i.e., snags and drag) as well as increased susceptibility to predation, specifically for smaller fish. The effects on swimming performance due to the presence of a neutrally buoyant externally attached acoustic transmitter were examined by comparing critical swimming speeds (Ucrit) for juvenile Chinook salmon tagged with two different neutrally buoyant external transmitters (Type A and B), nontagged individuals, and those surgically implanted with the current JSATS acoustic transmitter. Fish tagged with the Type A and B designs had lower Ucrit when compared to nontagged individuals. However, there was no difference in Ucrit among fish tagged with Type A or B designs compared to those with surgically implanted tags. Further testing was then conducted to determine if predator avoidance ability was affected due to the presence of Type A tags when compared to nontagged fish. No difference was detected in the number of tagged and nontagged fish consumed by rainbow trout throughout the predation trials. The results of this study support the further testing on the efficacy of a neutrally buoyant externally attached telemetry tag for survival studies involving juvenile salmonids passing through hydro turbines.
International Nuclear Information System (INIS)
Highlights: ► Study of aqueous solutions of vitamins B1.HCl and B6.HCl at different temperatures has been presented. ► These are important vitamins. ► Different interactions among solute and solvents have been investigated. ► The results are interpreted in terms of water structure making and breaking effects due to cations. -- Abstract: The experimental values of density (ρ), speed of sound (u), absolute viscosity (η) and refractive index (nD) properties are reported for aqueous solutions of thiamine hydrochloride (vitamin B1.HCl) and pyridoxine hydrochloride (vitamin B6.HCl) within the concentration range (0.01 to 0.55) mol ⋅ kg−1 at three different temperatures, viz. T/K = 278.15, 288.15, and 298.15. Using experimental data, different derived parameters such as the apparent molar volume of solute (ϕV), isentropic compressibility of solution (βS), apparent molar isentropic compressibility of solute (ϕKS) and relative viscosity of solution (ηr) have been computed. The limiting values of apparent molar volume (ϕV0) and apparent molar isentropic compressibility (ϕKS0) have been obtained. The limiting apparent molar expansivity (ϕE0) of solute, coefficient of thermal expansion (α∗) and hydration numbers (nh) of above vitamins in the aqueous medium have also been estimated. The experimental values of relative viscosity are used to calculate the Jones–Dole equation viscosity A and B coefficients for the hydrochlorides. The temperature coefficients of B i.e. (dB/dT) for these solutes have been used to study water structure making and breaking effects due to cations. Further, a discussion is made on the basis of solute–solute and solute–solvent interactions
Buoyant Turbulent Kinetic Energy Production in Steep-Slope Katabatic Flow
Oldroyd, Holly J.; Pardyjak, Eric R.; Higgins, Chad W.; Parlange, Marc B.
2016-07-01
We develop several critical concepts that should be considered when interpreting, modelling and designing future experiments for flows over sloping terrain. Vertical buoyancy fluxes in katabatic flows can be positive and a source of turbulent kinetic energy (TKE) despite the statically stable, thermal stratification that drives these flows. This phenomenon occurs when the ratio of along-slope to slope-normal kinematic heat fluxes is greater than the cotangent of the slope angle, suggesting a critical value of slope-angle steepness found in earlier studies. We provide field-data-based evidence that the along-slope heat flux may dominate the variables in this inequality, and therefore in generating buoyant TKE production or suppression over a steep slope. These data show the along-slope heat flux can be more variable and significantly larger in magnitude than the slope-normal component. The gradient Richardson number does not include the effects of the along-slope buoyancy; furthermore, none of the canonical stability parameters can properly reflect the TKE redistribution from turbulent transport divergence and the sink of TKE in cases of counter-gradient momentum fluxes, which we frequently observe near the peak of the katabatic jet. In such cases, canonical stability parameters inadequately represent the physical mechanisms associated with stability. These results have broad implications related to accurately modelling turbulence and surface exchanges over sloping terrain and illustrate the need to more thoroughly investigate the along-slope heat flux and its drivers, the meaning and definitions of stability, and the effects of non-local turbulent transport.
Woodson, C.B.; Washburn, L.; Barth, J.A.; Hoover, D.J.; Kirincich, A.R.; McManus, M.A.; Ryan, J.P.; Tyburczy, J.
2009-01-01
During the upwelling season in central California, northwesterly winds along the coast produce a strong upwelling jet that originates at Point A??o Nuevo and flows southward across the mouth of Monterey Bay. A convergent front with a mean temperature change of 3.77 ?? 0.29??C develops between the warm interior waters and the cold offshore upwelling jet. To examine the forcing mechanisms driving the location and movement of the upwelling shadow front and its effects on biological communities in northern Monterey Bay, oceanographic conditions were monitored using cross-shelf mooring arrays, drifters, and hydrographic surveys along a 20 km stretch of coast extending northwestward from Santa Cruz, California, during the upwelling season of 2007 (May-September). The alongshore location of the upwelling shadow front at the northern edge of the bay was driven by: regional wind forcing, through an alongshore pressure gradient; buoyancy forces due to the temperature change across the front; and local wind forcing (the diurnal sea breeze). The upwelling shadow front behaved as a surface-trapped buoyant current, which is superimposed on a poleward barotropic current, moving up and down the coast up to several kilometers each day. We surmise that the front is advected poleward by a preexisting northward barotropic current of 0.10 m s-1 that arises due to an alongshore pressure gradient caused by focused upwelling at Point A??o Nuevo. The frontal circulation (onshore surface currents) breaks the typical two-dimensional wind-driven, cross-shelf circulation (offshore surface currents) and introduces another way for water, and the material it contains (e.g., pollutants, larvae), to go across the shelf toward shore.Copyright 2009 by the American Geophysical Union.
Woutersen, Sander; Zhao, Zuofeng; Angell, C Austen
2016-01-01
The striking anomalies in physical properties of supercooled water that were discovered in the 1960-70s, remain incompletely understood and so provide both a source of controversy amongst theoreticians, and a stimulus to experimentalists and simulators to find new ways of penetrating the "crystallization curtain" that effectively shields the problem from solution. Recently a new door on the problem was opened by showing that, in ideal solutions, made using ionic liquid solutes, water anomalies are not destroyed as earlier found for common salt and most molecular solutes, but instead are enhanced to the point of precipitating an apparently first order liquid-liquid transition. The evidence was a spike in apparent heat capacity during cooling that could be fully reversed during reheating before any sign of ice crystallization appeared. Here, we use decoupled-oscillator infrared spectroscopy to define the structural character of this phenomenon using similar down and upscan rates as in the calorimetric study. Th...
Institute of Scientific and Technical Information of China (English)
黄振健; 黄旭光; 陈基焕; 谢金玲
2011-01-01
A novel determination of solution density based on fiber refractive index sensing principle is first proved and studied in this paper. This method is suitable for the determination of solution density with known solute. Refractive indices of the NaCl and KNO3 solutions with different concentrations at constant temperature (20 ℃) were measured respectively by applying this method. The linear relationship between refractive index and solution density is found. So solution dersity can be determined if the refractive index is measured. Densities of NaCl and KNO3 solutions are determined by this method,and the results are in good agreement with the theory. Measurement precision is at the order of 10-3 g/ml.The effect of temperature and the stability test are further studied,and the results are very good.%提出了一种新颖的基于光纤折射率传感原理的溶液密度测定方法.适用于已知溶液中溶质成分时密度的测量.分别测定了 NaCl和KNO3溶液在恒定温度(20℃)下不同浓度时的折射率,与溶液的密度进行对比研究发现.溶液折射率与密度成线性关系,只要测得溶液的折射率就能测定溶液的密度.应用本方法对NaCl和KNO3溶液分别进行密度测量,实验结果与理论十分吻合,测量精度可达到10-5g/ml量级.在不同温度下,用本方法对NaCI和KNO3溶液进行密度测量,实验结果与文献值一致,证实了本方法对测试环境的适用性强.对本方法进行了稳定性测试,效果良好.
Institute of Scientific and Technical Information of China (English)
Ding Fa-Zhu; Gu Hong-Wei; Zhang Teng; Dai Shao-Tao; Xiao Li-Ye
2011-01-01
This paper studies the effect of oxygen partial pressure on the fabrication of YBa2Cu3O7-x films on (00/) LaAlO3 substrates by metalorganic deposition using trifluoroacetates (TFA-MOD). As the oxygen partial pressure increases to 1500 Pa, a great increase in the superconducting properties is observed at high magnetic fields parallel to the YBCO c axis. The cross-sectional transmission electron microscope images show that a high density of stacking faults in the size range of 10-15 nm may act as flux pinning centres to enhance the critical current density of the YBCO films
Holographic Magnetisation Density Waves
Donos, Aristomenis
2016-01-01
We numerically construct asymptotically $AdS$ black brane solutions of $D=4$ Einstein theory coupled to a scalar and two $U(1)$ gauge fields. The solutions are holographically dual to $d=3$ CFTs in a constant external magnetic field along one of the $U(1)$'s. Below a critical temperature the system's magnetisation density becomes inhomogeneous, leading to spontaneous formation of current density waves. We find that the transition can be of second order and that the solutions which minimise the free energy locally in the parameter space of solutions have averaged stressed tensor of a perfect fluid.
International Nuclear Information System (INIS)
To safety and permanently store high-level nuclear waste, the potential Yucca Mountain repository system must mitigate the release and transport of radionuclides for tens of thousands of years. In the failure scenario of greatest concern, water would contact a waste package, accelerate its failure rate, and eventually transport radionuclides to the water table. Our analyses have demonstrated that the only significant source of liquid water is fracture flow from: (1) natural infiltration, (2) condensate drainage generated under boiling conditions, and (3) condensate drainage generated under sub-boiling conditions. The first source of liquid water arises from the ambient system; the second and third sources are generated by repository heat. Buoyant, gas-phase flow, occurring either on a sub-repository scale or on a mountain scale, may play an important role in generating the second and third sources of liquid water. By considering a wide range in bulk permeability of the fractured rock, we identify a threshold bulk permeability at which buoyant, gas-phase convection begins to dominate hydrological behavior. At 10 times this threshold, convection begins to dominate thermal behavior. These effects can dominate moisture movement in the unsaturated zone on the order of 100,000 yr. We find that the development of a large above-boiling zone suppresses the effects of buoyant vapor flow. Zones of sharply contrasting bulk permeability also influence condensate generation and drainage. Of particular concern are conditions that focus vapor flow and condensate drainage, which could result in persistent refluxing at the repository, causing water to drip onto waste packages. These effects can occur under both sub-boiling and boiling conditions Long-term in situ heater tests are required to diagnose the potential for major repository-heat- driven sources of fractures flow
International Nuclear Information System (INIS)
This paper studies the effect of oxygen partial pressure on the fabrication of YBa2Cu3O7−x films on (00l) LaAlO3 substrates by metalorganic deposition using trifluoroacetates (TFA-MOD). As the oxygen partial pressure increases to 1500 Pa, a great increase in the superconducting properties is observed at high magnetic fields parallel to the YBCO c axis. The cross-sectional transmission electron microscope images show that a high density of stacking faults in the size range of 10–15 nm may act as flux pinning centres to enhance the critical current density of the YBCO films (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Voss, C.I.
1984-01-01
SUTRA (Saturated-Unsaturated Transport) is a computer program which can be used to simulate the movement of fluid and the transport of either energy or dissolved substances in a subsurface environment. The model employs a two-dimensional hybrid finite-element and integrated-finite-difference method to approximate the governing equations that describe the two interdependent processes that are simulated by SUTRA: (1) fluid density-dependent saturated or unsaturated groundwater flow, and either (2a) transport of a solute in the groundwater, in which the solute may be subject to: equilibrium adsorption on the porous matrix, and both first-order and zero-order production or decay, or, (2b) transport of thermal energy in the groundwater and solid matrix of the aquifer. SUTRA provides, as the primary calculated results, fluid pressures and either solute concentrations or temperatures, as they vary with time, everywhere in the simulated subsurface system. SUTRA may also be used to simulate simpler subsets of the above process. SUTRA may be employed for areal and cross-sectional models of saturated groundwater flow systems, and for cross-sectional models of unsaturated zone flow. Solute transport simulation using SUTRA may be used to simulate natural or man-induced chemical transport, solute sorption, production and decay. SUTRA may be used for simulation of variable density leachate movement, and for cross-sectional simulation of salt-water intrusion in aquifers at near-well or regional scales, with either dispersed or relatively sharp transition zones between fresh water and salt water. SUTRA energy transport simulation may be employed to model thermal regimes in aquifers, subsurface heat conduction, aquifer thermal energy storage systems, geothermal reservoirs, thermal pollution of aquifers, and natural hydrogeologic convection systems. (USGS)
Velamati, Ratna Kishore; Vivek, M; Goutham, K; Sreekanth, G R; Dharmarajan, Santosh; Goel, Mukesh
2015-11-01
Air pollution is one of the major global hazards and industries have been one of its major contributors. This paper primarily focuses on analyzing the dispersion characteristics of buoyant plumes of the pollutant released from a multi-flue vertical stack into a variable temperature gradient atmosphere (α) in a constant-velocity cross wind using two stack configurations-inline and parallel. The study is conducted for different Froude numbers, Fr = 12.64, 9.55, and 8.27. The atmospheric temperature gradients considered for the study are 0, +1, +1.5, and +2 K/100 m. The numerical study is done using the commercial computational fluid dynamics (CFD) code FLUENT. The effects of stack configuration, α, and Fr on the plume characteristics are presented. It is observed that the plume rises higher and disperses over a larger area with the inline configuration due to better mixing and shielding effect. With higher α, it is seen that the plume rises initially and then descends due to variation of the buoyant force. The plume rise initially is strongly influenced by the momentum of the jet, and as it moves downstream, it is influenced by the cooling rate of the plume. Furthermore, the plume rises higher and disperses over a larger area with a decrease in Fr. PMID:26099599
Wang, Wei; Zhai, Jianping; Li, Qin
2015-04-15
In this work, Ag(+) and Ag(0) were absorbed onto the surface of 3-mercaptopropyltriethoxysilane modified fly ash cenospheres (FACs) in two Ag activation processes. The activation methods, avoiding traditional surface sensitization by SnCl2, successfully initiated electroless copper particles deposition for the preparation of buoyant Cu-FAC and CuAg-FAC composites. The CuAg-FAC had a much more uniform morphology than the Cu-FAC. The catalytic performance of the Cu-FAC and CuAg-FAC was examined by the reduction of Orange IV azo dye with the presence of NaBH4. 98.4% of Orange IV was rapidly reduced within 25 min by the CuAg-FAC, whereas 76.4% of Orange IV was removed by the Cu-FAC. The results reveal that the degradation processes matched well with the pseudo-first-order kinetics model, and rate constants of 0.057 and 0.186 min(-1) were obtained for the Cu-FAC and CuAg-FAC, respectively. Moreover, two other dyes of Orange II and Reactive Black 5 were also efficiently reduced by the CuAg-FAC which could be easily recycled and stably reused at least four times. These buoyant metal-coated FAC composites would be very useful in various catalytic reductions. PMID:25585281
Uma, B; Radhakrishnan, R; Eckmann, D M; Ayyaswamy, P S
2013-01-01
A hybrid scheme based on Markovian fluctuating hydrodynamics of the fluid and a non-Markovian Langevin dynamics with the Ornstein-Uhlenbeck noise perturbing the translational and rotational equations of motion of a nanoparticle is employed to study the thermal motion of a nearly neutrally buoyant nanoparticle in an incompressible Newtonian fluid medium. A direct numerical simulation adopting an arbitrary Lagrangian-Eulerian based finite element method is employed in simulating the thermal motion of the particle suspended in the fluid contained in a cylindrical vessel. The instantaneous flow around the particle and the particle motion are fully resolved. The numerical results show that (a) the calculated temperature of the nearly neutrally buoyant Brownian particle in a quiescent fluid satisfies the equipartition theorem; (b) the translational and rotational decay of the velocity autocorrelation functions result in algebraic tails, over long time; (c) the translational and rotational mean square displacements of the particle obeys Stokes-Einstein and Stokes-Einstein-Debye relations, respectively; and (d) the parallel and perpendicular diffusivities of the particle closer to the wall are consistent with the analytical results, where available. The study has important implications for designing nanocarriers for targeted drug delivery. PMID:23814315
Dorch, S B F
2006-01-01
Context: The context of this paper is buoyant toroidal magnetic flux ropes, which is a part of flux tube dynamo theory and the framework of solar-like magnetic activity. Aims: The aim is to investigate how twisted magnetic flux ropes interact with a simple magnetized stellar model envelope--a magnetic "convection zone"--especially to examine how the twisted magnetic field component of a flux rope interacts with a poloidal magnetic field in the convection zone. Method: Both the flux ropes and the atmosphere are modelled as idealized 2.5-dimensional concepts using high resolution numerical magneto-hydrodynamic (MHD) simulations. Results: It is illustrated that twisted toroidal magnetic flux ropes can interact with a poloidal magnetic field in the atmosphere to cause a change in both the buoyant rise dynamics and the flux rope's geometrical shape. The details of these changes depend primarily on the polarity and strength of the atmospheric field relative to the field strength of the flux rope. It is suggested th...
Densities of liquids and vapors in boiling NaCl-H2O solutions: a PVTx summary from 300° to 500°C
Bischoff, James L.
1991-01-01
Experimental data for densities of liquids and vapors on the two-phase surface of the system NaCl-H2O were compiled and evaluated to provide a complete summary between 300° and 500°C. The results are added to a previously published PTx summary compiled in the same manner to provide a PVTx summary of the present state of knowledge. Results are in table form of use to the understanding of two-phase behaviour in boiling hydrothermal systems and to theoretical modeling of this important system.
Deosarkar, S. D.; Ghatbandhe, A. S.
2014-01-01
Molecular interactions and structural fittings in binary ethylene glycol + ethanol (EGE, x EG = 0.4111-0.0418) and ethylene glycol + water (EGW, x EG = 0.1771-0.0133) mixtures were studied through the measurement of densities (ρ), viscosities (η), and refractive indices ( n D ) at 303.15 K. Excess viscosities (η E ), molar volumes ( V m ), excess molar volumes ( V {/m E }), and molar retractions ( R M ) of the both binary systems were computed from measured properties. The measured and computed properties have been used to understand the molecular interactions in unlike solvents and structural fittings in these binary mixtures.
Energy Technology Data Exchange (ETDEWEB)
Ramamohan, T R; Madhukar, K [CSIR Centre for Mathematical Modelling and Computer Simulation (C-MMACS), Council of Scientific and Industrial Research, Wind Tunnel Road, Bangalore-560 037 (India); Shivakumara, I S, E-mail: trr@cmmacs.ernet.in, E-mail: shivakumarais@gmail.com, E-mail: k.madhukara@gmail.com [UGC Centre for Advanced Studies in Fluid Mechanics, Department of Mathematics, Bangalore University, Bangalore-560 001 (India)
2011-08-15
We study the effects of both convective and unsteady inertia on the dynamics and rheology of a dilute suspension of periodically forced neutrally buoyant spherical particles, at low Reynolds numbers, in a quiescent Newtonian fluid. The inclusion of inertia results in additional terms in the equation governing the dynamics of the particle that represent a fading memory of the entire history of the particle motion. The inclusion of convective inertia in the low Reynolds number limit makes the memory term nonlinear. Several tests were performed to show that the results presented in this paper are physically reasonable and correct. A perturbation analysis of the problem yields strong evidence that the results of our simulations are correct. It is observed that there is a preferred direction in this system which manifests itself in the properties of the solution. This preferred direction is identified as the direction of the initial motion of the particle. We present here results on the behavior of various parameters with respect to Reynolds numbers and the amplitude of the periodic force. These include phase-space plots between particle displacement and particle velocity and the variation of a rheological parameter, namely a 'normal stress' with respect to Reynolds number and the amplitude of the periodic force. We believe that our results may be technologically important since the rheological parameter depends strongly on controllable parameters such as the Reynolds number and the amplitude of the periodic force. Further, this system is one of the simplest systems whose rheology shows non-Newtonian behavior, such as the presence of a normal stress. In addition, this system represents a physically realizable system for experimentally testing the frameworks developed to calculate the collective behavior of systems of oscillators with memory.
International Nuclear Information System (INIS)
We study the effects of both convective and unsteady inertia on the dynamics and rheology of a dilute suspension of periodically forced neutrally buoyant spherical particles, at low Reynolds numbers, in a quiescent Newtonian fluid. The inclusion of inertia results in additional terms in the equation governing the dynamics of the particle that represent a fading memory of the entire history of the particle motion. The inclusion of convective inertia in the low Reynolds number limit makes the memory term nonlinear. Several tests were performed to show that the results presented in this paper are physically reasonable and correct. A perturbation analysis of the problem yields strong evidence that the results of our simulations are correct. It is observed that there is a preferred direction in this system which manifests itself in the properties of the solution. This preferred direction is identified as the direction of the initial motion of the particle. We present here results on the behavior of various parameters with respect to Reynolds numbers and the amplitude of the periodic force. These include phase-space plots between particle displacement and particle velocity and the variation of a rheological parameter, namely a 'normal stress' with respect to Reynolds number and the amplitude of the periodic force. We believe that our results may be technologically important since the rheological parameter depends strongly on controllable parameters such as the Reynolds number and the amplitude of the periodic force. Further, this system is one of the simplest systems whose rheology shows non-Newtonian behavior, such as the presence of a normal stress. In addition, this system represents a physically realizable system for experimentally testing the frameworks developed to calculate the collective behavior of systems of oscillators with memory.
Peřestý, Vít; Holder, Robert; Lexa, Ondrej; Racek, Martin; Jeřábek, Petr
2014-05-01
Recent tectonic models for the Variscan evolution of the Bohemian Massif emphasize the role of Rayleigh-Taylor instability for the 355-340 Ma evolution of the Moldanubian domain. This model is based on the presence of weak, low-density felsic material tectonically underplating a high-density mafic layer and its subsequent gravity-driven overturn. However, earlier phases of the Variscan orogeny concerning the emplacement of felsic low-density material to the base of the upper plate are so far poorly documented. We contribute to this problem by deciphering of polyphase early-Variscan (~375 Ma) deformation and metamorphism close to the main Variscan suture. Detailed structural, pseudosection and microstructural analyses combined with LASS monazite dating were carried out in metapelites along the western margin of the upper plate represented by the Teplá Crystalline Complex (TCC). This region is represented by a ~25 km wide deformation zone with E-W metamorphic gradients associated with two distinct early-Variscan events (~380-375 and ~375-370 Ma). The first compressional event produced a vertical NNE-SSW trending fabric and a continuous and prograde Barrovian metamorphic sequence ranging from biotite to kyanite zones at a field geotherm of 20 to 25 °C/km. Subsequently, a gently SE dipping normal shear-zone associated with retrogression develops along the base of the TCC. This sub-horizontal fabric shows normal metamorphic zonation ranging from sillimanite, biotite to chlorite zones and indicates vertical shortening related to unroofing of high pressure metabasites of the underlying Mariánské-Lázně Complex. The first metamorphic fabric is interpreted to result from early thickening of the upper plate during continental underthrusting of Saxothuringian continent (380 to 375 Ma) while the second deformation and metamorphism (~370 Ma) reflects vertical shortening produced by buoyant uplift of accreted Saxothuringian felsic crust. This event is the unique yet
Monteiro, Andréa M.; Jardini, Maria A. N.; Giampaoli, Viviana; Alves, Sarah; Figueiredo Neto, Antônio M.; Gidlund, Magnus
2012-11-01
The Z-Scan (ZS) technique in the thermal regime has been used to measure the nonlinear optical response of low-density lipoprotein (LDL). The ZS technique is carried out in LDL from 40 patients with chronic periodontitis before and after three, six, and 12 months of periodontal treatment. Clinical parameters such as probing depths, bleeding on probing, total and differential white blood cells counts, lipid profiles, cytokine levels, and antibodies against oxidized LDL are also determined and compared over time. Before the treatment, the ZS experimental results reveal that the LDL particles of these patients are heavily modified. Only after 12 months of the periodontal treatment, the ZS results obtained reveal behavioral characteristics of healthy particles. This conclusion is also supported by complementary laboratorial analysis showing that the periodontal treatment induces systemic changes in several inflammatory markers.
Tsuchiya, Koji; Uchida, Katsumi; Kaminosono, Yoshiya; Shimizu, Kazushi; Ishii, Tadahiro; Yajima, Hirofumi
2013-03-01
The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) prevents their potential applications in high-resolution field-effect transistors, nanoscale sensors, and conductive films. In the present study, we demonstrate the development of a new selective-separation procedure for collecting semiconducting single-walled carbon nanotubes (s-SWNTs) with a high purity from as-synthesized SWNTs individually dispersed with mixed dispersing agents consisting of carboxymethylcellulose (CMC) and sodium dodecyl sulfate (SDS) in water using density gradient ultracentrifugation (DGU). Ultraviolet-visible-near infrared (UV-vis-NIR) absorption, resonance Raman, and NIR photoluminescence spectroscopies revealed that the s-SWNTs were enriched to a purity of more than 97%, and that the recovery was approximately 40% through the DGU treatment. This separation strategy is expected to impact the application fields using s-SWNTs.
Khaled, K. F.
2010-09-01
The effects of thiourea derivatives, namely N-methyl thiourea (MTU), N-propyl thiourea (PTU) and N-allyl thiourea (ATU) on the corrosion behaviour of iron in 1.0 M solution of HNO 3 have been investigated in relation to the concentration of thiourea derivatives. The experimental data obtained using the techniques of weight loss, Tafel polarization and electrochemical impedance spectroscopy, EIS. The results showed that these compounds revealed a good corrosion inhibition, (ATU) being the most efficient and (MTU) the least. Computational studies have been used to find the most stable adsorption sites for thiourea derivatives. This information help to gain further insight about corrosion system, such as the most likely point of attack for corrosion on iron (1 1 0), the most stable site for thiourea derivatives adsorption and the binding energy of the adsorbed layer. The efficiency order of the inhibitors obtained by experimental results was verified by theoretical analysis.
Institute of Scientific and Technical Information of China (English)
Maryam Irani; Hanafi Ismail; Zulkifli Ahmad; Maohong Fan
2015-01-01
The purpose of this work is to remove Pb(Ⅱ) from the aqueous solution using a type of hydrogel composite.A hydrogel composite consisting of waste linear low density polyethylene,acrylic acid,starch,and organo-montmorillonite was prepared through emulsion polymerization method.Fourier transform infrared spectroscopy (FTIR),Solid carbon nuclear magnetic resonance spectroscopy (CNMR)),silicon-29 nuclear magnetic resonance spectroscopy (Si NMR)),and X-ray diffraction spectroscope ((XRD) were applied to characterize the hydrogel composite.The hydrogel composite was then employed as an adsorbent for the removal of Pb(Ⅱ) from the aqueous solution.The Pb(Ⅱ)-loaded hydrogel composite was characterized using Fourier transform infrared spectroscopy (FTIR)),scanning electron microscopy (SEM)),and X-ray photoelectron spectroscopy ((XPS)).From XPS results,it was found that the carboxyl and hydroxyl groups of the hydrogel composite participated in the removal of Pb(Ⅱ).Kinetic studies indicated that the adsorption of Pb(Ⅱ)followed the pseudo-second-order equation.It was also found that the Langmuir model described the adsorption isotherm better than the Freundlich isotherm.The maximum removal capacity of the hydrogel composite for Pb(Ⅱ) ions was 430 mg/g.Thus,the waste linear low-density polyethylene-g-poly (acrylic acid)-co-starch/organo-montmorillonite hydrogel composite could be a promising Pb(Ⅱ) adsorbent.
Investigation of High-Energy-Density Lithium Battery with Aqueous Electrolyte Solution%高比能水体系锂电池研究
Institute of Scientific and Technical Information of China (English)
刘兴江; 杨同欢; 桑林; 丁飞
2012-01-01
实现水溶液锂电池的关键技术是如何保护金属锂电极不与水反应。提出了一种保护金属锂电极,其不仅在有机电解液体系稳定而且在水溶液中也可稳定工作,这种锂电极可以用于水体系锂电池。该研究制备了双层锂离子电解质保护的金属锂电极,其外层采用的LAGP（Li1＋x＋yAlxGe2-x SiyP3-yO12）玻璃陶瓷电解质相对于包括水溶液等电解液是稳定的,该玻璃陶瓷电解质的电导率达到0.57 mS cm^-1。通过交流阻抗评估发现不同电解质间的界面阻抗是水体系锂电池内阻的主要来源。最终采用双层保护金属锂电极制备的水体系锂空气电池和锂水电池可以稳定工作。%The key technology for aqueous lithium battery is protecting lithium from water.A protected lithium electrode which is stable not only in organic electrolyte but also in aqueous solutions and which can be used in aqueous lithium battery is proposed.The double layer Li-ion conductive electrolyte protected lithium electrode has been prepared.The front layer of LAGP（Li1＋x＋y AlxGe2-x SiyP3-yO12） glass-ceramic with ionic conductivity of 0.57 mS cm^-1 which is stable to electrolyte including aqueous solution.It is found that the impedance of interface of LAGP/liquid electrolyte is the major one for aqueous lithium battery.Finally,Li-Air battery and Li-Water battery have been assembled,and the two types of aqueous lithium battery are capable of work by using double layer protected lithium electrode.
Zonoozi, Akram Hasani; Kroupa, Pavel
2016-01-01
The observed mass-to-light ($M/L$) ratios of a large sample of GCs in M31 show an inverse trend with metallicity compared to what is expected from Simple Stellar Population (SSP) models with an invariant canonical stellar IMF, in the sense that the observed $M/L$ ratios decrease with increasing metallicity. We show that incorporating the effect of dynamical evolution the SSP models with a canonical IMF can not explain the decreasing $M/L$ ratios with increasing metallicity for the M31 GCs. The recently derived top-heavy IMF as a function of metallicity and embedded cluster density is proposed to explain the lower than expected $M/L$ ratios of metal-rich GCs. We find that the SSP models with a top-heavy IMF, retaining a metallicity- and cluster mass- dependent fraction of the remnants within the clusters, and taking standard dynamical evolution into account can successfully explain the observed $M/L-[Fe/H]$ relation of M31 GCs. Thus we propose that the kinematical data of GCs can be used to constrain the top-h...
The trapping and escape of buoyant vortex rings in sharply stratified fluids
Camassa, R; McLaughlin, R; Mertens, K; Monbureau, E; Nenon, D; Smith, C; Viotti, C; White, B
2011-01-01
In this fluid dynamics video we study the dynamics of miscible vortex rings falling in ambient strongly (near two-layer) stratified fluid. Experiments and direct numerical simulations using the variable density Navier-Stokes (VARDEN) solver are presented and compared. Critical phenomena are identified depending upon the key parameters of the experiment (fluid and ring densities, upper layer vortex travel distance, etc) in which the descending dense vortex ring may experience complete trapping, partial trapping, or fissioning into a cascade of smaller vortices. The interaction of the vortex ring with the upper layer fluids leads to viscous entrainment which alters the effective buoyancy of the ring. Upon impinging on a density transition, the entrained fluid imparts different dynamics as it attempts to regain equilibrium leading to the critical behaviors.
International Nuclear Information System (INIS)
The rate of TiO2-photocatalyzed oxidation of crude oils spilled on aqueous 0.5 M NaCA was determined by measuring the rate of O2 uptake. The photocatalyst was attached to 100-μm-diameter fly-ash-derived buoyant cenospheres. Partial hydrophobic coating of the cenospheres assured their retention at the air-oil interface. The rate depended on the near-UV (broad band, 365-nm peak) irradiance below 25W m-2, but varied only mildly with irradiance in the 25-45 W m-2 range. It increased upon wave motion imitating agitation of the liquid, and upon increase of the cenosphere:oil mass ratio. It varied only mildly for different crudes. From the measured rates, cleanup times as short as 5-10 days were estimated
Shi, Lingling; Pan, Tsorng-Whay; Glowinski, Roland
2013-01-01
Two motions of oscillation and vacillating breathing (swing) of a red blood cell have been observed in bounded Poiseuille flows (Phys. Rev. E 85, 16307 (2012)). To understand such motions, we have studied the oscillating motion of a neutrally buoyant rigid particle of the same shape in Poiseuille flow in a narrow channel and obtained that the crucial point is to have the particle interacting with Poiseuille flow with its mass center moving up and down in the channel central region. Since the mass center of the cell migrates toward the channel central region, its oscillating motion of the inclination angle is similar to the aforementioned motion as long as the cell keeps the shape of long body. But as the up-and-down oscillation of the cell mass center damps out, the oscillating motion of the inclination angle also damps out and the cell inclination angle approaches to a fixed angle.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The RNG к-ε model considering the buoyancy effect,which is solved by the hybrid finite analytic method,is used to simulate the mixture of the horizontal round thermal buoyant jet in compound open channel flow.The mixing features near the spout and flowing characteristic of the secondary currents are studied by numerical simulation.Meanwhile,(1) the distribution of the measured isovels for stream-wise velocity,(2) secondary currents,(3) the distribution of the measured isovels for temperature of typical cross-section near the spout,were obtained by the three-dimensional Micro ADV and the Temperature measuring device.Compared with experimental data,the RNG к-εmodel based on buoyancy effect can preferably simulate the jet which performs the bifurcation phenomenon,jet reattachment (Conada effect) and beach secondary currents phenomenon with the effect of ambient flow,buoyancy,and secondary currents of compound section and so on.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests. 160.060-3a Section 160.060-3a Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for...
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests. 160.052-3a Section 160.052-3a Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for...
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests. 160.047-3a Section 160.047-3a Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Specification for...
Directory of Open Access Journals (Sweden)
G Tripathi
2010-12-01
Full Text Available "n "nBackground and the purpose of the study: A gastroretentive pH sensitive system has been a frontier approach to release the drug in controlled manner in stomach and duodenum. The aim of this study was to develop buoyant beads of gellan based, wherein, the oil was entrapped, blended with hydroxypropyl methyl cellulose or carbopol 934 in order to evaluate its potential for targeted sustained delivery of clarithromycin in the gastric region. "nMethods: Buoyant beads of gellan was developed by inotropic gelation technique using calcium carbonate as gas forming agent and the drug polymer dispersion was emulsified with mineral oil. The oil was entrapped and blended with hydroxypropyl methyl cellulose or carbopol 934. The developed beads were evaluated in terms of diameter, % floating, encapsulation efficiency, In vitro drug release, In vivo gastric residence efficacy and clarithromycine concentration in the mucosa of the experimental animal model. "nResults: The scanning electron microscope photograph indicated that the prepared beads were spherical in shape and buoyancy, encapsulation efficiency and drug content obtained from all batches were satisfactory. Particle size and percentage buoyancy of the gel beads increased by raising the concentration of calcium carbonate. The formulation exhibited sustained release profile and was best fitted in the Peppas model with n < 0.45. Subsequent coating of microbeads exhibited zero-order sustained pattern of the drug release up to 8 hrs. Batch B4 showed comparatively better residence and the drug concentration in the gastric mucosa of the treated animals. Conclusion:The result provides evidence that the prepared optimized formulation may be used effectively for pH sensitive gastric targeted antibiotic such as clarithromycin.
Directory of Open Access Journals (Sweden)
Richard S Brown
Full Text Available Turbine-passed fish are exposed to rapid decreases in pressure which can cause barotrauma. The presence of an implanted telemetry tag increases the likelihood of injury or death from exposure to pressure changes, thus potentially biasing studies evaluating survival of turbine-passed fish. Therefore, a neutrally buoyant externally attached tag was developed to eliminate this bias in turbine passage studies. This new tag was designed not to add excess mass in water or take up space in the coelom, having an effective tag burden of zero with the goal of reducing pressure related biases to turbine survival studies. To determine if this new tag affects fish performance or susceptibility to predation, it was evaluated in the field relative to internally implanted acoustic transmitters (JSATS; Juvenile Salmon Acoustic Telemetry System used widely for survival studies of juvenile salmonids. Survival and travel time through the study reach was compared between fish with either tag type in an area of high predation in the Snake and Columbia rivers, Washington. An additional group of fish affixed with neutrally-buoyant dummy external tags were implanted with passive integrated transponder (PIT tags and recovered further downstream to assess external tag retention and injury. There were no significant differences in survival to the first detection site, 12 river kilometers (rkm downstream of release. Travel times were also similar between groups. Conversely, externally-tagged fish had reduced survival (or elevated tag loss to the second detection site, 65 rkm downstream. In addition, the retention study revealed that tag loss was first observed in fish recaptured approximately 9 days after release. Results suggest that this new tag may be viable for short term (<8 days single-dam turbine-passage studies and under these situations, may alleviate the turbine passage-related bias encountered when using internal tags, however further research is needed to
International Nuclear Information System (INIS)
percent of direct measured density values. The average percent error observed in particle densities was 4.8, 8.2, and 25.8 percent for S1D3 (high-density soda-lime glass), S3D4 (zirconia), and S1D2 (soda-lime glass) beads, respectively. The maximum measured particle density error observed was 14.5, 21.0, and 58.4, for S1D3, S3D4, and S1D2 beads, respectively. Multiple sources of error can exist that contribute to inaccurate estimates of particle density using the PSVS approach. Two significant influences observed were thermal convective currents in the settling column fluid and non-spherical (irregular) particle shapes in the standard test materials. Experimental results using buoyant beads suggest thermal convective currents can influence the movement of settling particles as much as 4 mm/s. These thermal convective currents are clearly a significant concern for smaller and less-dense particles/agglomerates which have terminal velocities of the same magnitude. Significant effort went into the design and fabrication of a thermal control system for the PSVS settling column. However, small temperature variations (<0.3 deg. C) are difficult to prevent and measure accurately. Therefore, although designing the thermal control system was necessary, it is not considered the only solution to minimize error due to thermal convective currents. The use of small diameter (10 to 27 μm) polyethylene buoyant beads (in low concentrations) during actual settling experiments may be necessary to provide insight into particle-particle interactions and fluid velocity correction factors to account for potential influences from thermal convective currents. Future testing will incorporate the buoyant beads into the analysis technique when the suspension fluid is chemically compatible. The use of the Newton's law to calculate particle/agglomerate densities assumes spherical particle shapes. As the actual particle/agglomerates diverge from spherical, the margin of error increases. The selection
Numerical simulation of the 3D behavior of thermal buoyant airflows in pentahedral spaces
Energy Technology Data Exchange (ETDEWEB)
Ridouane, El Hassan [Department of Mechanical Engineering, University of Vermont, 33 Colchester Avenue, 201 Votey Building, Burlington, VT 05405 (United States)], E-mail: eridouan@uvm.edu; Campo, Antonio [Department of Mechanical Engineering, University of Vermont, 33 Colchester Avenue, 201 Votey Building, Burlington, VT 05405 (United States)
2008-10-15
A numerical study of three-dimensional natural convection in an attic space with heated horizontal base and cooled upper walls is presented. Every previous study pertinent to this subject as of today has assumed that the flow in attics is two-dimensional and restricted to triangular cavities. This problem is examined for fixed aspect ratios holding width to height of 2 and depth to height of 3.33 and Rayleigh numbers ranging from 10{sup 4} to 8 x 10{sup 5}. The coupled system of conservation equations, subject to the proper boundary conditions, along with the equation of state assuming the air behaves as a perfect gas are solved with the finite volume method. In the conservation equations, the second-order-accurate QUICK scheme was used for the discretization of the convective terms and the SIMPLE scheme for the pressure-velocity coupling. It is categorically found that the flow in the attic is 3D. From the physics of the problem, two steady-state solutions are possible. The symmetrical solution prevails for relatively low Rayleigh numbers. However, as the Ra is gradually increased, a transition occurs at a critical value Ra{sub C}. Above this value of Ra{sub C}, an asymmetrical solution exhibiting a pitchfork bifurcation arises and eventually becomes steady. Results are presented detailing the occurrence of the pitchfork bifurcation and the resulting flow patterns are described.
Energy Technology Data Exchange (ETDEWEB)
Murphy, M. W. [DESY (Deutsches Elektronen-Synchrotron), FS-PEX, Notkestrasse 85, 22607 Hamburg (Germany); Yiu, Y. M., E-mail: yyiu@uwo.ca; Sham, T. K. [Department of Chemistry, University of Western Ontario, London, ON N6A5B7 (Canada); Ward, M. J. [Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, NY 14853 (United States); Liu, L. [Institute of Functional Nano and Soft Materials (FUNSOM) and Soochow University-Western University Center for Synchrotron Radiation Research, Soochow University, Suzhou, Jiangsu, 215123 (China); Hu, Y. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK S7N2V3 (Canada); Zapien, J. A. [Center Of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China); Liu, Yingkai [Institute of Physics and Electronic Information, Yunnan Normal University, Kunming, Yunnan, 650500 (China)
2014-11-21
The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS{sub x}Se{sub 1−x} solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.
U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...
Energy Technology Data Exchange (ETDEWEB)
Palacios, E. [Universidad Politecnica de Madrid (Spain). Departamento de Mecanica Industrial; Nogueira, J.; Rodriguez, P.A.; Lecuona, A. [Universidad Carlos III de Madrid (Spain). Departamento de Ingenieria Termica y de Fluidos
2009-02-15
This work presents and characterizes the existence of two different regimes in the spreading and break-up of liquid flat-fan sheets when discharging in low-density atmospheres. The motivation of the study is the improvement on the absorption phenomena of lithium bromide aqueous solution when discharging in a 600-1,500 Pa water vapor environment. This corresponds to the absorber conditions in current absorption closed-cycle cooling machines. Despite this, the dimensionless characterization obtained has universal validity. The conditions that define the change in the break-up regime, the dimensionless sheet break-up length and the break-up time are given as a function of the parameters involved. Digital particle tracking velocimetry (PTV) has been applied to measure the velocity field and additional visualization techniques have been used to further characterize the break-up process. The experiments verify the existence of critical gas-to-liquid density and viscosity ratios below which gas to liquid interaction becomes negligible. The article also offers expressions that define their values as a function of the other dimensionless parameters. (orig.)
DEFF Research Database (Denmark)
Garnett, E S; Webber, C E; Coates, G;
1977-01-01
The density of a defined volume of the human lung can be measured in vivo by a new noninvasive technique. A beam of gamma-rays is directed at the lung and, by measuring the scattered gamma-rays, lung density is calculated. The density in the lower lobe of the right lung in normal man during quiet...
International Nuclear Information System (INIS)
The corrosion inhibition properties of a new class of oxadiazole derivatives, namely 3,5-bis(n-pyridyl)-1,2,4-oxadiazoles (n-DPOX) for C38 carbon steel corrosion in 1 M HCl medium were analysed by electrochemical impedance spectroscopy (EIS). An adequate structural model of the interface was used and the values of the corresponding parameters were calculated and discussed. The experimental results showed that these compounds are excellent inhibitors for the C38 steel corrosion in acid solution and that the protection efficiency increased with increasing the inhibitors concentration. Electrochemical impedance data demonstrate that the addition of the n-DPOX derivatives in the corrosive solution decreases the charge capacitance and simultaneously increases the function of the charge/discharge of the interface, facilitating the formation of an adsorbed layer over the steel surface. Adsorption of these inhibitors on the steel surface obeys to the Langmuir adsorption isotherm. X-ray photoelectron spectroscopy (XPS) and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal hydrochloric solution by n-DPOX is due to the formation of a chemisorbed film on the steel surface. Quantum chemical calculations using the Density Functional Theory (DFT) and the Quantitative Structure Activity Relationship (QSAR) approach were performed on n-DPOX derivatives to determine the relationship between molecular structure and their inhibition efficiencies. The results of the quantum chemical calculations and experimental inhibition efficiency were subjected to correlation analysis and indicate that their inhibition effect is closely related to EHOMO, ELUMO, and dipole moment (μ).
Energy Technology Data Exchange (ETDEWEB)
Outirite, Moha; Lagrenee, Michel; Lebrini, Mounim [Unite de Catalyse et de Chimie du Solide, UMR-CNRS 8181, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France); Traisnel, Michel; Jama, Charafeddine [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF UMR-CNRS 8008, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France); Vezin, Herve [Laboratoire de Chimie Organique et Macromoleculaire, UMR-CNRS 8009, USTL Bat C4, F-59655 Villeneuve d' Ascq Cedex (France); Bentiss, Fouad, E-mail: fbentiss@enscl.f [Laboratoire de Chimie de Coordination et d' Analytique, Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco)
2010-02-01
The corrosion inhibition properties of a new class of oxadiazole derivatives, namely 3,5-bis(n-pyridyl)-1,2,4-oxadiazoles (n-DPOX) for C38 carbon steel corrosion in 1 M HCl medium were analysed by electrochemical impedance spectroscopy (EIS). An adequate structural model of the interface was used and the values of the corresponding parameters were calculated and discussed. The experimental results showed that these compounds are excellent inhibitors for the C38 steel corrosion in acid solution and that the protection efficiency increased with increasing the inhibitors concentration. Electrochemical impedance data demonstrate that the addition of the n-DPOX derivatives in the corrosive solution decreases the charge capacitance and simultaneously increases the function of the charge/discharge of the interface, facilitating the formation of an adsorbed layer over the steel surface. Adsorption of these inhibitors on the steel surface obeys to the Langmuir adsorption isotherm. X-ray photoelectron spectroscopy (XPS) and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal hydrochloric solution by n-DPOX is due to the formation of a chemisorbed film on the steel surface. Quantum chemical calculations using the Density Functional Theory (DFT) and the Quantitative Structure Activity Relationship (QSAR) approach were performed on n-DPOX derivatives to determine the relationship between molecular structure and their inhibition efficiencies. The results of the quantum chemical calculations and experimental inhibition efficiency were subjected to correlation analysis and indicate that their inhibition effect is closely related to E{sub HOMO}, E{sub LUMO}, and dipole moment (mu).
Reactive solute transport in variable density
Sáinz García, Álvaro M.
2009-01-01
A pesar del gran avance que ha vivido la modelaci on del transporte reactivo en las ultimas d ecadas, s olo unos pocos estudios han abordado el problema del transporte reactivo en un ujo con densidad variable. En este trabajo se han desarrollado dos aproximaciones num ericas capaces de simular los procesos complejos comprendidos en este problema: decoupled conser- vative salinity (DCS), que no tiene en cuenta el efecto de las reacciones qu micas en el ujo y time lagged r...
An experimental study on the formation of negatively-buoyant vortex rings
Wu, Jeff X.; Hunt, Gary R.
2015-11-01
Experiments to examine the formation of dense saline vortex rings projected vertically upwards into a quiescent freshwater environment were conducted. The setup was designed to dispense a cylindrical column of source fluid with aspect ratio L / D (the length L of dispensed saline column to the nozzle diameter D) over a pre-set time interval. In an effort to execute an impulsive start and finish, a controlled flow circulation driven by a gear pump was developed to approximate a top-hat profile of source exit velocity versus time. Our measurements focus on describing the evolving morphology of the vortex rings with time and with source conditions (L / D and source Froude number). Our results reveal distinct formation regimes and our estimates of time required for formation as a function of density difference confirm predictions from previously published numerical simulations. The volume-based approach we adopt provides potentially a new angle for investigating the physics of these flows.
Directory of Open Access Journals (Sweden)
Haque Anwar U
2016-01-01
Full Text Available Dorsal fin is used in swimming animals like shark for the generation of thrust as well as to meet the requirement of the lateral stability. In the case of aircraft, rudders are normally used for the said requirement. In the present work, this nature inspired idea is explored for its application to neutralize the unavoidable asymmetric thrust produced by the twin engines of a hybrid buoyant aircraft. First, the estimation of asymmetric thrust is obtained with the help of analytical techniques for maximum thrust condition at 4 degree angle of attack. The moment generated by it is utilized for the sizing of a dorsal fin which looks similar to a tapered wing and is placed aft of the center of gravity. Wind tunnel testing at subsonic speed is carried out to explore the design features of this rotatable dorsal fin. It is found that a small rotation of 5 degree can generate the required moment. However, such rotation requires a complete pneumatic/electro-mechanical system and an alternative of it is to use a cambered airfoil for the dorsal fin installed at fixed location. Such a flow controlling device can also be used as an antenna mast, which is commonly installed out the fuselage of the aircraft for communication purposes. Moreover, by incorporating this technique, a pilot doesn’t have to put an extra effort to make the aircraft stable in the presence of side wind.
International Nuclear Information System (INIS)
We have introduced a new and elaborate approach to understand the impact of grid resolution and subgrid chemistry assumption on the grid-model prediction of species concentrations for a system with highly non-homogeneous chemistry - a reactive buoyant plume immediately downwind of the stack in a convective boundary layer. The Parcel-Grid approach plume was used to describe both the air parcel turbulent transport and chemistry. This approach allows an identical transport process for all simulations. It also allows a description of subgrid chemistry. The ambient and plume parcel transport follows the description of Luhar and Britter (Atmos. Environ, 23 (1989) 1911, 26A (1992) 1283). The chemistry follows that of the Carbon-Bond mechanism. Three different grid sizes were considered: fine, medium and coarse, together with three different subgrid chemistry assumptions: micro-scale or individual parcel, tagged-parcel (plume and ambient parcels treated separately), and untagged-parcel (plume and ambient parcels treated indiscriminately). Reducing the subgrid information is not necessarily similar to increasing the model grid size. In our example, increasing the grid size leads to a reduction in the suppression of ozone in the presence of a high-NOx stack plume, and a reduction in the effectiveness of the NOx-inhibition effect. On the other hand, reducing the subgrid information (by using the untagged-parcel assumption) leads to an increase in ozone reduction and an enhancement of the NOx-inhibition effect insofar as the ozone extremum is concerned. (author)
Fraser, Ceridwen I; Waters, Jonathan M
2013-02-01
The parasitic phaeophycean endophyte Herpodiscus durvillaeae (Lindauer) G. R. South has previously only been recorded from New Zealand, in association with a single host species, Durvillaea antarctica (Chamisso) Hariot (southern bull-kelp). Here we use DNA sequence data from plastid and nuclear markers (chloroplast rbcL, ribosomal LSU, and a nuclear pseudogene copy of COI) to test for the presence of H. durvillaeae beyond the New Zealand region, and on host species other than D. antarctica. Analyses of samples from the Falkland Islands confirm the first record of H. durvillaeae from the Atlantic Ocean. We report that Falkland Islands H. durvillaeae are genetically indistinguishable from samples of this species from New Zealand's sub-Antarctic Campbell Island, suggesting recent dispersal of the parasite across the Pacific Ocean, presumably by rafting with its buoyant macroalgal host. We also here record H. durvillaeae from New Zealand endemics Durvillaea poha Fraser et al. and D. willana Lindauer. PMID:27008401
Multi-parametric Study of Rising 3D Buoyant Flux Tubes in an Adiabatic Stratification Using AMR
Martínez-Sykora, Juan; Moreno-Insertis, Fernando; Cheung, Mark C. M.
2015-11-01
We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, magnetohydrodynamic simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vorticity in the main body of the tube of opposite sign on the opposite sides of the apex. This is a consequence of the inhomogeneity of the azimuthal component of the field on the flux surfaces. The lift force associated with this global vorticity makes the flanks of the tube move away from their initial vertical plane in an antisymmetric fashion. The trajectories have an oscillatory motion superimposed, due to the shedding of vortex rolls to the wake, which creates a Von Karman street.
Rosen, T; Nordmark, A; Aidun, C K; Lundell, F; Mehlig, B
2015-01-01
We numerically analyse the rotation of a neutrally buoyant spheroid in a shear flow at small shear Reynolds number. Using direct numerical stability analysis of the coupled nonlinear particle-flow problem we compute the linear stability of the log-rolling orbit at small shear Reynolds number, ${\\rm Re}_a$. As ${\\rm Re}_a \\to 0$ and as the box size of the system tends to infinity we find good agreement between the numerical results and earlier analytical predictions valid to linear order in ${\\rm Re}_a$ for the case of an unbounded shear. The numerical stability analysis indicates that there are corrections to the analytical result of order ${\\rm Re}_a^{3/2}$. We also compare the analytical results to results of lattice-Boltzmann simulations to analyse the stability of the tumbling orbit at shear Reynolds numbers of order unity. Theory for an unbounded system at infinitesimal shear Reynolds number predicts a bifurcation of the tumbling orbit at aspect ratio $\\lambda_{\\rm c} \\approx 0.137$ below which tumbling ...
Jones, K E; Pierce, S E
2016-03-01
Ecological diversification into new environments presents new mechanical challenges for locomotion. An extreme example of this is the transition from a terrestrial to an aquatic lifestyle. Here, we examine the implications of life in a neutrally buoyant environment on adaptations of the axial skeleton to evolutionary increases in body size. On land, mammals must use their thoracolumbar vertebral column for body support against gravity and thus exhibit increasing stabilization of the trunk as body size increases. Conversely, in water, the role of the axial skeleton in body support is reduced, and, in aquatic mammals, the vertebral column functions primarily in locomotion. Therefore, we hypothesize that the allometric stabilization associated with increasing body size in terrestrial mammals will be minimized in secondarily aquatic mammals. We test this by comparing the scaling exponent (slope) of vertebral measures from 57 terrestrial species (23 felids, 34 bovids) to 23 semi-aquatic species (pinnipeds), using phylogenetically corrected regressions. Terrestrial taxa meet predictions of allometric stabilization, with posterior vertebral column (lumbar region) shortening, increased vertebral height compared to width, and shorter, more disc-shaped centra. In contrast, pinniped vertebral proportions (e.g. length, width, height) scale with isometry, and in some cases, centra even become more spool-shaped with increasing size, suggesting increased flexibility. Our results demonstrate that evolution of a secondarily aquatic lifestyle has modified the mechanical constraints associated with evolutionary increases in body size, relative to terrestrial taxa. PMID:26679743
Rosén, T; Einarsson, J; Nordmark, A; Aidun, C K; Lundell, F; Mehlig, B
2015-12-01
We numerically analyze the rotation of a neutrally buoyant spheroid in a shear flow at small shear Reynolds number. Using direct numerical stability analysis of the coupled nonlinear particle-flow problem, we compute the linear stability of the log-rolling orbit at small shear Reynolds number Re(a). As Re(a)→0 and as the box size of the system tends to infinity, we find good agreement between the numerical results and earlier analytical predictions valid to linear order in Re(a) for the case of an unbounded shear. The numerical stability analysis indicates that there are substantial finite-size corrections to the analytical results obtained for the unbounded system. We also compare the analytical results to results of lattice Boltzmann simulations to analyze the stability of the tumbling orbit at shear Reynolds numbers of order unity. Theory for an unbounded system at infinitesimal shear Reynolds number predicts a bifurcation of the tumbling orbit at aspect ratio λ(c)≈0.137 below which tumbling is stable (as well as log rolling). The simulation results show a bifurcation line in the λ-Re(a) plane that reaches λ≈0.1275 at the smallest shear Reynolds number (Re(a)=1) at which we could simulate with the lattice Boltzmann code, in qualitative agreement with the analytical results. PMID:26764819
Multi-Parametric Study of Rising 3D Buoyant Flux Tubes in an Adiabatic Stratification Using AMR
Martinez-Sykora, Juan; Cheung, Mark C M
2015-01-01
We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, MHD simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vortic...
Haque, Anwar U.; Asrar, Waqar; Omar, Ashraf A.; Sulaeman, Erwin; J. S Ali, Mohamed
2016-03-01
Dorsal fin is used in swimming animals like shark for the generation of thrust as well as to meet the requirement of the lateral stability. In the case of aircraft, rudders are normally used for the said requirement. In the present work, this nature inspired idea is explored for its application to neutralize the unavoidable asymmetric thrust produced by the twin engines of a hybrid buoyant aircraft. First, the estimation of asymmetric thrust is obtained with the help of analytical techniques for maximum thrust condition at 4 degree angle of attack. The moment generated by it is utilized for the sizing of a dorsal fin which looks similar to a tapered wing and is placed aft of the center of gravity. Wind tunnel testing at subsonic speed is carried out to explore the design features of this rotatable dorsal fin. It is found that a small rotation of 5 degree can generate the required moment. However, such rotation requires a complete pneumatic/electro-mechanical system and an alternative of it is to use a cambered airfoil for the dorsal fin installed at fixed location. Such a flow controlling device can also be used as an antenna mast, which is commonly installed out the fuselage of the aircraft for communication purposes. Moreover, by incorporating this technique, a pilot doesn't have to put an extra effort to make the aircraft stable in the presence of side wind.
International Nuclear Information System (INIS)
The benefits of using codes with 3-D capabilities to address safety issues of LWRs will be applicable to both the current generation of nuclear reactors as well to future ALWRs. The phenomena governing the containment response in case of some postulated severe accident scenarios include gas (air, hydrogen, steam) stratification in the containment, gas distribution between containment compartments, wall condensation, etc. These phenomena are driven by buoyant high momentum injection (jets) and/or low momentum injection (plumes). For instance, mixing in the immediate vicinity of the postulated line break is mainly dominated by very high velocity efflux, while low-momentum flows are responsible for most of the transport processes within the containment. A project named SETH is currently in progress under the auspices of 15 OECD countries, with the aim of creating an experimental database suitable to assess the 3-D code capabilities in analyzing key-physical phenomena relevant for LWR safety analysis. This paper describes some results of two SETH tests, performed in the PANDA facility (located at PSI in Switzerland), focusing on plumes flowing near a containment wall. The plumes are generated by injecting a constant amount of steam in one of two interconnected vessels initially filled with air. In one of the two tests the temperature of the injected steam and the initial containment wall and fluid temperatures allowed for condensation during the test. (authors)
Giacomini, Raffaella; Gottschling, Andreas; Haefke, Christian; White, Halbert
2002-01-01
We derive a new family of probability densities that have the property of closed-form integrability. This flexible family finds a variety of applications, of which we illustrate density forecasting from models of the AR-ARCH class for U.S. inflation. We find that the hypernormal distribution for the model's disturbances leads to better density forecasts than the ones produced under the assumption that the disturbances are Normal or Student's t.
Direct numerical simulation of transitional and turbulent buoyant planar jet flames
Mehravaran, K.; Jaberi, F. A.
2004-12-01
The effects of gravity on the physical and compositional structures of transitional and turbulent diffusion flames are studied via analysis of the data generated by direct numerical simulation of a planar jet flame at various gravity conditions. A fully compressible, high-order compact, finite-difference computational scheme is used together with a global kinetics model for chemical reaction. The results of our nonreacting turbulent jet simulations are in good agreement with the available experimental data. The results of our reacting jet simulations are also consistent with previous findings and indicate that in the absence of gravity, combustion damps the flow instability, and hence reduces "turbulence production" and jet growth. However, in the "finite-gravity" conditions, combustion generated density variations may promote turbulence and enhance both the mixing and the combustion through buoyancy effects. Our results also indicate that the gravity effects on a transitional/turbulent jet flame is not limited to large-scale flame flickering, and there is a significant impact on small-scale turbulence and mixing as well. Furthermore, the analysis of compositional flame structures suggests that the finite-rate chemistry effects are more significant in finite-gravity conditions than in zero-gravity.
Directory of Open Access Journals (Sweden)
B. Gera
2012-03-01
Full Text Available An interesting transport phenomenon is observed through openings between two compartments separated by a thin, vented, horizontal partition such as those between containment internals in nuclear power systems, in industrial installations in event of fire, passive cooling of heated structures and in natural building ventilation. A heavier fluid located on the top of a lighter fluid and separated by a horizontal vent constitutes a gravitationally unstable system. Horizontal vents produce flow, which are unstable with irregular oscillatory behavior. The objective of the present work was to simulate such type of flow across a circular opening in horizontal partition in presence of buoyancy force. Unsteady, axisymmetric Navier-Stokes equations have been solved with Finite Volume Method. The equations were solved using the in-house CFD code based upon the well-established pressure-based finite volume methodology. In terms of temporal differencing second order accurate Crank-Nicolson scheme was used. Interpolation to cell faces for the convective terms was performed using a third order QUICK scheme, second order central differencing was used for the viscous terms. Pressure-velocity coupling was based on the SIMPLE procedure. The upper chamber was filled with salt water and the lower chamber with fresh water, creating a density differential between the two chambers. Opposing forces at the interface created a gravitationally unstable system, and an oscillating exchange of fluid developed. Three different cases for vent length to diameter ratio (L/D 0.008, 0.0376 and 0.106 from a reported experiment were examined. The pulsation frequencies and their decay with time have been determined. The flow coefficients were computed and compared with experimental results.
Pore-Scale Modeling of Reactive-Multiphase-Buoyant Flow for Carbon Capture and Storage
Anwar, S.; Cunningham, J. A.; Trotz, M.; Thomas, M. W.; Stewart, M.
2010-12-01
Physical and geochemical processes at multiple scales are yet to be understood for the storage of carbon dioxide (CO2) in aquifers and the concomitant mitigation of CO2 concentration in the atmosphere. In deep saline aquifers, the pores in the potential aquifers for CO2 storage are initially filled with saline water (brine). The entrapment of brine in pores after injection of CO2 is controlled by capillary forces and by the inertial force driving CO2 inside the carbonate aquifer. The entrapped/residual brine will be a site for geochemical reactions which could alter the pore network and/or the permeability of the formation. Therefore, the pore-scale understanding of displacement of resident brine by CO2 is critical to evaluate the storage efficiency of carbonate aquifers and to quantify any dissolution or precipitation of minerals (e.g., gypsum, calcite, dolomite). In this project, we have developed a multiphase flow model, based on the lattice Boltzmann equation, that can describe pore-scale displacement of brine by invading CO2. The multiphase flow model is applied to three different pore networks saturated with brine. The amount of brine trapped after invasion of the domain by CO2 is strongly dependent on the pore network. We also examine the effects of CO2 density and viscosity (which depend on formation temperature and pressure) on the amount of entrapped brine. Only by resolving the flow at the pore scale can we predict the residual brine saturation and other parameters which control CO2 sequestration in deep saline aquifers. Future work will focus on coupling the pore-scale multiphase flow model to a chemistry model to predict mineral dissolution and precipitation.
Densities, Spectral Densities and Modality
Davies, PL Laurie; Kovac, A.
2002-01-01
This paper considers the problem of specifying a simple approximating density function for a given data set (x1,…,xn). Simplicity is measured by the number of modes but several different definitions of approximation are introduced. The taut string method is used to control the numbers of modes and to produce candidate approximating densities. Refinements are introduced that improve the local adaptivity of the procedures and the method is extended to spectral densities.
Choudhuri, Jyoti Roy; Chandra, Amalendu
2014-11-21
We have presented a first principles simulation study of the structural and dynamical properties of a liquid-vapor interfacial system of a concentrated (5.3 M) aqueous NaCl solution. We have used ab initio molecular dynamics to examine the structural and dynamical properties of the bulk and interfacial regions. The structural aspects of the system that have been considered here include the inhomogeneous density profiles of ions and water molecules, hydrogen bond distributions, orientational profiles, and also vibrational frequency distributions in the bulk and interfacial regions. It is found that the sodium ions are mostly located in the interior, while the chloride anions occupy a significant portion of the interface of the slab. The water dipoles at the interface prefer to orient parallel to the surface. The dynamical aspects of the interfaces are investigated in terms of diffusion, orientational relaxation, hydrogen bond dynamics, and vibrational spectral diffusion. The results of the interfacial dynamics are compared with those of the corresponding bulk region. It is observed that the interfacial molecules exhibit faster diffusion and orientational relaxation with respect to the bulk. However, the interfacial molecules are found to have longer hydrogen bond lifetimes than those of the bulk. We have also investigated the correlations of hydrogen bond relaxation with the vibrational frequency fluctuations of interfacial water molecules. PMID:25416903
International Nuclear Information System (INIS)
In this paper, the hydrodynamic interaction between two identical neutrally buoyant smooth spheres freely moving at negligible Reynolds numbers in an unbounded wide gap Couette flow is investigated by three dimensional boundary element method (BEM) simulations. Such information is fundamental to the macroscopic characterization of suspension flows. The numerical results show that the hydrodynamic interaction of the sphere-pair causes both spheres to experience repulsive cross-streamline displacements, which are in opposite directions, when the trailing sphere is approaching the leading one. These cross-streamline displacements reach their maxima when the sphere-pair is at their closest center-to-center distance due to the strongest hydrodynamic interaction at this instant. After that, the initially trailing sphere becomes the leading one, and the sphere-pair begins to separate, causing the hydrodynamic interaction to decrease gradually and the spheres to return to their individual initial streamlines. The center of gravity of the sphere-pair in this non-linear shear field experiences a preferential cross-streamline migration in the plane of shear when they meet, firstly moving from regions of higher shear rates towards those of lower ones before the meeting and then experiencing a 'reverse migration', that is, moving from regions of low shear rates to those of higher ones, after the meeting, which is not presented in a linear shear field such as in a simple shear flow. There is also a cross-streamline migration of the center of gravity of the sphere-pair in the plane of vorticity, but this migration does not have a preferential direction. All these results suggest that the non-linearity of the shear field is responsible for the preferential cross-streamline displacement and the particle migration in concentrated suspensions undergoing inhomogeneous shearing. In addition, the hydrodynamic interaction between the sphere-pair has also been quantified under various
Garay, Mauricio
2012-01-01
Arithmetic class are closed subsets of the euclidean space which generalise arithmetical conditions encoutered in dynamical systems, such as diophantine conditions or Bruno type conditions. I prove density estimates for such sets using Dani-Kleinbock-Margulis techniques.
DEFF Research Database (Denmark)
Olsen, Jógvan Magnus Haugaard; Steinmann, Casper; Ruud, Kenneth;
2015-01-01
We present a new QM/QM/MM-based model for calculating molecular properties and excited states of solute-solvent systems. We denote this new approach the polarizable density embedding (PDE) model and it represents an extension of our previously developed polarizable embedding (PE) strategy. The PDE...... model is a focused computational approach in which a core region of the system studied is represented by a quantum-chemical method, whereas the environment is divided into two other regions: an inner and an outer region. Molecules belonging to the inner region are described by their exact densities...
Hydrodynamic Equations for Microscopic Phase Densities
Gerasimenko, V. I.; Shtyk, V. O.; Zagorodny, A. G.
2009-01-01
The evolution equations for the generalized microscopic phase densities are introduced. The evolution equations of average values of microscopic phase densities are derived and a solution of the initial-value problem of the obtained hydrodynamic type hierarchy is constructed.
... Density Exam/Testing › Low Bone Density Low Bone Density Low bone density is when your bone density ... people with normal bone density. Detecting Low Bone Density A bone density test will determine whether you ...
Effective density and viscosity of a suspension
International Nuclear Information System (INIS)
This paper presents results of a series of experiments on the settling velocity of spheres in two-component solid--liquid suspensions. Both sedimenting and fluidized suspensions are considered. Particular emphasis has been given to the effective values of the density and viscosity of the mixture which allow us to describe slow settling of a test sphere using the Francis modification of the Stokes formula for the settling of a single sphere in a Newtonian fluid with wall effects. Our experimental results show that values of the effective density and viscosity are close to the average density of the mixture and to the viscosity of the mixture predicted by a correlation suggested by Thomas when the test particles are of the same size as the suspended particles, or larger, but not too much smaller. The signature of the failure of the concept of effective fluid properties is traced to an increase of the variance of the experimental results and is not associated merely with a different than average value of the density; in particular, none of our results are well described by the use of the fluid density in the expression for the buoyant force. We also studied the settling of spheres in fluidized suspensions at high Reynolds numbers. The Barnea and Mizrahi model for the expansion of uniformly fluidized beds was modified in two different ways to describe the settling of particles in the fluidized suspensions. It is not possible to describe the modified drag laws with an effective Newtonian theory if for no other reason than the effective densities which enter into buoyancy are not in principle those which control inertia. The modified drag law is in agreement with experiments in sedimentation columns. Coarse agreement between the predicted and measured drag is found in the fluidized suspension even when the test and the fluidized particles are the same size
Mille, Matthieu
2000-01-01
In this paper, the author adopt a time-geography approach to examine the temporal variation of urban density by analysing spatial load changes at different times of the day at the communal and community level. The evolution of means of transport coupled with the abandon of the notion of direct proximity to the urban dwelling place provide the basis for this new approach to the study of urban densities. The shift towards spatial specialisation within cities has lead to radical changes in the f...
Energy Technology Data Exchange (ETDEWEB)
Bittencourt, Guilherme Rodrigues [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil). PIBIC; Castro, Leonardo Curvello de; Pereira, Walsan W.; Patrao, Karla C. de Souza; Fonseca, Evaldo S. da; Dantas, Maria Leticia [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI). Lab. de Neutrons
2009-07-01
The bath of a manganese sulfate (BMS) is a system for absolute standardization of the neutron sources. This work establishes a functional relationship based on semi-empirical methods for the theoretical prediction of physical density values, concentration and rate between the hydrogen and manganese atoms presents in the solution of the BMS
Seidl, Michael; Gori-Giorgi, Paola; Savin, Andreas
2007-01-01
We reformulate the strong-interaction limit of electronic density functional theory in terms of a classical problem with a degenerate minimum. This allows us to clarify many aspects of this limit, and to write a general solution, which is explicitly calculated for spherical densities. We then compare our results with previous approximate solutions and discuss the implications for density functional theory.
Havill, C. D.
1974-01-01
The uses of lighter-than-air vehicles are examined in the present day transportation environment. Conventional dirigibles were found to indicate an undesirable economic risk due to their low speeds and to uncertainties concerning their operational use. Semi-buoyant hybrid vehicles are suggested as an alternative which does not have many of the inferior characteristics of conventional dirigibles. Economic and performance estimates for hybrid vehicles indicate that they are competitive with other transportation systems in many applications, and unique in their ability to perform some highly desirable emergency missions.
Energy Technology Data Exchange (ETDEWEB)
Fardisi, S. [University of Calgary, Calgary, T2N 1N4 (Canada); Karim, Ghazi A., E-mail: karim@ucalgary.ca [University of Calgary, Calgary, T2N 1N4 (Canada)
2009-08-15
The dynamics of the dispersion of a fixed mass of the buoyant fuel, methane, when exposed with a negligible pressure difference to overlaying air within vertical cylindrical enclosures open to the atmosphere is investigated. Features of the formation and dispersion of flammable mixtures created by the gas dissipation were examined using a 3D CFD model. For the cases considered, the lean-flammable mixture boundary appears to travel mainly at a near constant rate while the rich limit front shows a more chaotic behaviour. The corresponding simulation using an axis-symmetrical 2D model tended to under-predict the dynamics of the lean and rich boundaries, for the cases considered.
International Nuclear Information System (INIS)
The dynamics of the dispersion of a fixed mass of the buoyant fuel, methane, when exposed with a negligible pressure difference to overlaying air within vertical cylindrical enclosures open to the atmosphere is investigated. Features of the formation and dispersion of flammable mixtures created by the gas dissipation were examined using a 3D CFD model. For the cases considered, the lean-flammable mixture boundary appears to travel mainly at a near constant rate while the rich limit front shows a more chaotic behaviour. The corresponding simulation using an axis-symmetrical 2D model tended to under-predict the dynamics of the lean and rich boundaries, for the cases considered.
Energy Technology Data Exchange (ETDEWEB)
Wells, Beric E.; Meyer, Perry A.; Chen, Guang
2000-04-10
Tank 241-SY-101 is a double-shell radioactive waste storage tank containing waste that, before recent transfer and water back-dilution operations, was capable of retaining gas and producing flammable buoyant displacement gas release events (BD GREs). A BD GRE occurs when a portion of the nonconvective layer waste retains enough gas to become buoyant, rises to the waste surface, breaks up, and releases some of the stored gas. Installing the mixer pump in 1993 successfully mitigated gas retention in the settled solids layer in SY-101 and has prevented BD GREs. Gas retention in the floating drust layer and the corresponding accelerated waste level growth made it necessary to begin waste removal and back-dilution with water in December 1999. During these operations, some of the SY-101 mixed slurry layer is removed and transferred into Tank 241-SY-102. There was some concern that adding the SY-101 waste into SY-102 could create a waste configuration in SY-102 capable of BD GREs. This report updates and extends earlier assessments of the potential for BD GRE conditions in SY-102 after waste is transferred from SY-101. We determined that, under the given assumptions, no possibility of BD GREs exists in SY-102 from the SY-101 waste being added during from December 1999 through March 2000.
International Nuclear Information System (INIS)
The HGSYSTEM/UF6 model was developed for use in preparing Safety Analysis Reports (SARs) by estimating the consequences of possible accidental releases of UF6 to the atmosphere at the gaseous diffusion plants (GDPs) located in Portsmouth, Ohio, and Paducah, Kentucky. Although the latter report carries a 1996 date, the work that is described was completed in late 1994. When that report was written, the primary release scenarios of interest were thought to be gas pipeline and liquid tank ruptures over open terrain away from the influence of buildings. However, upon further analysis of possible release scenarios, the developers of the SARs decided it was necessary to also consider accidental releases within buildings. Consequently, during the fall and winter of 1995-96, modules were added to HGSYSTEM/UF6 to account for flow and dispersion around buildings. The original HGSYSTEM/UF6 model also contained a preliminary method for accounting for the possible lift-off of ground-based buoyant plumes. An improved model and a new set of wind tunnel data for buoyant plumes trapped in building recirculation cavities have become available that appear to be useful for revising the lift-off algorithm and modifying it for use in recirculation cavities. This improved lift-off model has been incorporated in the updated modules for dispersion around buildings
Energy Technology Data Exchange (ETDEWEB)
Habibi, K.; Amiri, S.; Ashjaee, M. [Tehran Univ., Tehran (Iran, Islamic Republic of). Dept. of Mechanical Engineering, Laser Diagnostics Lab
2009-07-01
A study was conducted to investigate the flow properties and heat transfer behaviour of laminar and turbulent jet flows, with particular focus on the effect of impingement of a laminar slot jet on a vertical isothermal flat plate and the simultaneous interaction of the jet flow and natural buoyant regime. The thermal field was visualized using an experimental approach, while a Mach-Zehnder interferometer was used to obtain the local convective heat transfer coefficient. The planar jet was mounted parallel to the plate surface. The study took into account the variations of jet Reynolds numbers (Re) as well as the nozzle vertical distance from the leading edge of the plate. The jet strength was restricted to relatively low-Reynolds numbers in this study in order to observe the interaction between buoyancy driven flow and the impinging jet. It was concluded that low-speed jet flows could lead to mixed convection regimes. The jet path deviated as it interacted with buoyant flow. In such a flow, a minimum zone for heat transfer coefficient was followed by a peak in a position beyond the jet center. Reattachment occurred for larger Reynolds numbers. Therefore, in cases where heat transfer is a concern, a low-speed jet can enhance the effect above the impingement zone and reduce the effect at the bottom of the impingement zone. 9 refs., 1 tab., 10 figs.
International Nuclear Information System (INIS)
In support of tank waste safety programs, visualization tests were performed in the 1/12-scale tank facility, using a low-viscosity simulant. The primary objective of the tests was to obtain video records of the transient jet-sludge interaction. The intent is that these videos will provide useful qualitative data for comparison with model predictions. Two tests were initially planned: mixing interface visualization (MIV) and buoyant particle release (BPR). Completion of the buoyant particle release test was set aside in order to complete additional MIV tests. Rheological measurements were made on simulant samples before testing, and the simulant was found to exhibit thixotropic behavior. Shear vane measurements were also made on an in-situ analog of the 1/12-scale tank simulant. Simulant shear strength has been observed to be time dependent. The primary objective of obtaining video records of jet-sludge interaction was satisfied, and the records yielded jet location information which may be of use in completing model comparisons. The modeling effort is not part of this task, but this report also discusses test specific instrumentation, visualization techniques, and shear vane instrumentation which would enable improved characterization of jet-sludge interaction and simulant characteristics
Density matrix form of Gross-Pitaevskii equation
Chernega, V. N.; Man'ko, O. V.; Man'ko, V. I.
2014-01-01
We consider the generalized pure state density matrix which depends on di?erent time moments. The evolution equation for this density matrix is obtained in case where the density matrix corresponds to the solutions of Gross-Pitaevskii equation.
Degenerate Density Perturbation Theory
Palenik, Mark C
2016-01-01
Fractional occupation numbers can be used in density functional theory to create a symmetric Kohn-Sham potential, resulting in orbitals with degenerate eigenvalues. We develop the corresponding perturbation theory and apply it to a system of $N_d$ degenerate electrons in a harmonic oscillator potential. The order-by-order expansions of both the fractional occupation numbers and unitary transformations within the degenerate subspace are determined by the requirement that a differentiable map exists connecting the initial and perturbed states. Using the X$\\alpha$ exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first through third-order energies as a function of $\\alpha$, with and without a self-interaction correction. The fact that the XC Hessian is not positive definite plays an important role in the behavior of the occupation numbers.
Density distribution in Earth.
Press, F
1968-06-14
Earth models selected by a Monte Carlo procedure were tested against geophysical data; 5 million models were examined and six have passed all tests. Common features of successful models are an increased core radius and a chemically inhomogeneous core consistent with Fe-Ni alloy (20 to 50 percent Fe) for the solid portion and Fe-Si alloy (15 to 25 percent Fe) for the fluid core. The inhomogeneous mantle is consistent with an increase in the FeO:FeO + MgO ratio by a factor of 2 in the deep mantle. The transition zone is a region of not only phase change but also composition change; this condition would inhibit mantlewide convection. The upper-mantle solutions show large fluctuations in density; this state implies insufficient constraint on solutions for this region, or lateral variations in mantle composition ranging from pyrolite to eclogite. PMID:17818740
Energy Technology Data Exchange (ETDEWEB)
Elvsen, Per-Aake; Sandberg, Mats [Division of Indoor Environment, Centre for Built Environment, KTH Research School, University of Gaevle, 801 76 Gaevle (Sweden)
2009-01-15
The instantaneous velocity field and temperature field were measured and the airflow patterns visualised close to a diffuser for displacement ventilation. Since the low-velocity diffuser was located above the floor and the inlet air temperature was below the room temperature, the flow was governed by both momentum and buoyancy forces. The data were recorded with whole-field measuring techniques, particle streak velocimetry (PSV), particle image velocimetry (PIV) and infrared thermography (IR), in conjunction with a low thermal mass screen. The environment is very complex, supply of buoyant air with a commercial supply terminal with 20 nozzles pointing in different directions, which makes it difficult to use point-measuring techniques or computational fluid dynamics (CFD). The aim was twofold: (a) to explore what kind of information can be derived from whole-field measurement techniques in this context and (b) to investigate the trajectory of the flow discharged into the room and the entrainment of the flow. (author)
Fardisi, S; Karim, Ghazi A
2009-08-15
The dynamics of the dispersion of a fixed mass of the buoyant fuel, methane, when exposed with a negligible pressure difference to overlaying air within vertical cylindrical enclosures open to the atmosphere is investigated. Features of the formation and dispersion of flammable mixtures created by the gas dissipation were examined using a 3D CFD model. For the cases considered, the lean-flammable mixture boundary appears to travel mainly at a near constant rate while the rich limit front shows a more chaotic behaviour. The corresponding simulation using an axis-symmetrical 2D model tended to under-predict the dynamics of the lean and rich boundaries, for the cases considered. PMID:19237243
International Nuclear Information System (INIS)
Tank 241-SY-101 (SY-101) is a double-shell, radioactive waste storage tank with waste that, before the recent transfer and water back-dilution operations, was capable of retaining gas and producing buoyant displacement (BD) gas release events (GREs). Some BD GREs caused gas concentrations in the tank headspace to exceed the lower flammability limit (LFL). A BD GRE occurs when a portion of the nonconvective layer retains enough gas to become buoyant, rises to the waste surface, breaks up, and releases some of its stored gas. The installation of a mixer pump in 1993 successfully mitigated gas retention in the settled solids layer in SY-101 and has since prevented BD GREs. However, operation of the mixer pump over the years caused gas retention in the floating crust layer and a corresponding accelerated waste level growth. The accelerating crust growth trend observed in 1997--98 led to initiation of sequences of waste removal and water back-dilutions in December 1999. Waste is removed from the mixed slurry layer in Tank SY-101 and transferred into Tank 241-Sy-102 (SY-102). Water is then added back to dissolve soluble solids that retain gas. The initial transfer of 89,500 gallons of SY-101 waste, diluted in-line at 0.94:1 by volume with water, to SY-102 was conducted in December 1999. The second transfer of 230,000 gallons of original SY-101 waste, diluted approximately 0.9:1, was completed in January 2000, and the third transfer of 205,500 gallons of original SY-101 waste diluted at 0.9:1 was completed in March 2000
Wetting phenomena in electrolyte solutions
Ibagon, Ingrid
2014-01-01
The present study analyzes wetting phenomena in electrolyte solutions. They are investigated by means of classical density functional theory. First, the wetting of a charged substrate by an electrolyte solution is studied with emphasis on the influence of the substrate charge density and of the ionic strength on the wetting transition temperature and on the order of the wetting transition. The corresponding models consist of solvent particles, anions, and cations. Two mean field approaches ar...
Numerical Simulation of Density Current Evolution in a Diverging Channel
Directory of Open Access Journals (Sweden)
Mitra Javan
2012-01-01
Full Text Available When a buoyant inflow of higher density enters a reservoir, it sinks below the ambient water and forms an underflow. Downstream of the plunge point, the flow becomes progressively diluted due to the fluid entrainment. This study seeks to explore the ability of 2D width-averaged unsteady Reynolds-averaged Navier-Stokes (RANS simulation approach for resolving density currents in an inclined diverging channel. 2D width-averaged unsteady RANS equations closed by a buoyancy-modified − turbulence model are integrated in time with a second-order fractional step approach coupled with a direct implicit method and discretized in space on a staggered mesh using a second-order accurate finite volume approach incorporating a high-resolution semi-Lagrangian technique for the convective terms. A series of 2D width-averaged unsteady simulations is carried out for density currents. Comparisons with the experimental measurements and the other numerical simulations show that the predictions of velocity and density field are with reasonable accuracy.
Contamination of dental radiographic solutions.
Tamburus, J R; Pardini, L C; Watanabe, P C
1995-01-01
Thirteen groups of periapical radiographic films were evaluated to determine and compare within and between groups the effects of contamination of the fixer solution with developing solution during radiographic processing. An aluminum penetrometer was used as the radiographic object to produce different optical densities. The images were compared using radiographic density and contrast as parameters. There were significant differences between the control groups and the groups processed with a contaminated fixer solution. No statistically significant differences were observed in the intragroup comparisons. PMID:8688649
Institute of Scientific and Technical Information of China (English)
O.G.Martynenko; V.N.Korovkin
1992-01-01
An algebraic model of turbulence,involving buyancy forces,is used for calculating velocity and temperature fields in plane turbulent vertical jets in a non-homogeneous stagnant medium,A new approach to the solution of the governing system of partial differential differental equations (Continuity ,Conservation of momentum,heat (buoyancy),turbulent kinetic energy,dissipation rate and mean quadratic temperature fluctuation)is suggested which is based on the intrduction of mathematical variables.Comparison is made between the results of the present calculations with experimental and numerical data of ther authors.
Solute transport in a well under slow-purge and no-purge conditions
Plummer, M. A.; Britt, S. L.; Martin-Hayden, J. M.
2010-12-01
Non-purge sampling techniques, such as diffusion bags and in-situ sealed samplers, offer reliable and cost-effective groundwater monitoring methods that are a step closer to the goal of real-time monitoring without pumping or sample collection. Non-purge methods are, however, not yet completely accepted because questions remain about how solute concentrations in an unpurged well relate to concentrations in the adjacent formation. To answer questions about how undisturbed well water samples compare to formation concentrations, and to provide the information necessary to interpret results from non-purge monitoring systems, we have conducted a variety of physical experiments and numerical simulations of flow and transport in and through monitoring wells under low-flow and ambient flow conditions. Previous studies of flow and transport in wells used a Darcy’s law - based continuity equation for flow, which is often justified under the strong, forced-convection flow caused by pumping or large vertical hydraulic potential gradients. In our study, we focus on systems with weakly forced convection, where density-driven free convection may be of similar strength. We therefore solved Darcy’s law for porous media domains and the Navier Stokes equations for flow in the well, and coupled solution of the flow equations to that of solute transport. To illustrate expected in-well transport behavior under low-flow conditions, we present results of three particular studies: (1) time-dependent effluent concentrations from a well purged at low-flow pumping rates, (2) solute-driven density effects in a well under ambient horizontal flow and (3) temperature-driven mixing in a shallow well subject to seasonal temperature variations. Results of the first study illustrate that assumptions about the nature of in-well flow have a significant impact on effluent concentration curves even during pumping, with Poiseuille-type flow producing more rapid removal of concentration differences
International Nuclear Information System (INIS)
Reviewed in this statement are methods of preparing solutions to be used in laboratory experiments to examine technical issues related to the safe disposal of nuclear waste from power generation. Each approach currently used to prepare solutions has advantages and any one approach may be preferred over the others in particular situations, depending upon the goals of the experimental program. These advantages are highlighted herein for three approaches to solution preparation that are currently used most in studies of nuclear waste disposal. Discussion of the disadvantages of each approach is presented to help a user select a preparation method for his particular studies. Also presented in this statement are general observations regarding solution preparation. These observations are used as examples of the types of concerns that need to be addressed regarding solution preparation. As shown by these examples, prior to experimentation or chemical analyses, laboratory techniques based on scientific knowledge of solutions can be applied to solutions, often resulting in great improvement in the usefulness of results
Energy Technology Data Exchange (ETDEWEB)
Boulanger, Joan [Gas Turbine Laboratory, Institute for Aerospace Research, Ottawa, Ontario (Canada)
2010-04-15
At very low Froude number, buoyancy instabilities of round laminar jet diffusion flames disappear (except for small tip oscillations referred to as flickering) and those flames look stable and smooth. This study examines the contributions of the different phenomena in the flow dynamics that may explain this effect. It is observed that, at ultra-low Froude/Reynolds numbers, the material influenced by buoyancy is the plume of the flame and not the flame itself (reaction zone) that is short. Therefore, the vorticity creation zone does not profit from the reaction neighbourhood promoting a sharp gradient of density. Expansion and stretch are also important as they push vorticity creation terms more inside the flame and closer to the burner rim compared to moderate Froude flames. In these latter, the vorticity is continuously created around the flame reaction zone, along its developed height and closer to the vertical direction (in average). (author)
Synthesizing Chaotic Maps with Prescribed Invariant Densities
Rogers, Alan; Shorten, Robert; Heffernan, Daniel M.
2004-01-01
The Inverse Frobenius-Perron problem (IFPP) concerns the creation of discrete chaotic mappings with arbitrary invariant densities. In this note, we present a new and elegant solution to the IFPP, based on positive matrix theory. Our method allows chaotic maps with arbitrary piecewise-constant invariant densities, and with arbitrary mixing properties, to be synthesized.
Recovering phase density distribution from line density
International Nuclear Information System (INIS)
We present an algorithm to recover the longitudinal density distribution of the particles in a stationary bunch, from the experimentally obtained line density. This algorithm can be used as an alternative to the analytical theory
Structure and density of basaltic melts at mantle conditions from first-principles simulations
Bajgain, Suraj; Ghosh, Dipta B.; Karki, Bijaya B.
2015-10-01
The origin and stability of deep-mantle melts, and the magmatic processes at different times of Earth's history are controlled by the physical properties of constituent silicate liquids. Here we report density functional theory-based simulations of model basalt, hydrous model basalt and near-MORB to assess the effects of iron and water on the melt structure and density, respectively. Our results suggest that as pressure increases, all types of coordination between major cations and anions strongly increase, and the water speciation changes from isolated species to extended forms. These structural changes are responsible for rapid initial melt densification on compression thereby making these basaltic melts possibly buoyantly stable at one or more depths. Our finding that the melt-water system is ideal (nearly zero volume of mixing) and miscible (negative enthalpy of mixing) over most of the mantle conditions strengthens the idea of potential water enrichment of deep-mantle melts and early magma ocean.
Energy Technology Data Exchange (ETDEWEB)
Zboray, Robert, E-mail: robert.zboray@psi.c [Nuclear Energy and Safety Research Department, Laboratory for Thermal-hydraulics, Paul Scherrer Institute (Switzerland); Paladino, Domenico [Nuclear Energy and Safety Research Department, Laboratory for Thermal-hydraulics, Paul Scherrer Institute (Switzerland)
2010-10-15
In the frame of the OECD SETH project twenty-four experiments have been carried out on basic gas transport and mixing phenomena in the large-scale, multi-compartment PANDA facility. The experiments consist of several series based on the flow configuration driving the gas transport including plume and jet injection of saturated or superheated steam. A variety of test configurations with well-defined initial and boundary conditions have been investigated, including the parametric effects of the geometry of the injection, the composition and velocity of the injected mixture, the initial ambient composition, the vent location and the initial temperatures. The tests have been designed to be used for the validation of computer codes that are capable of analyzing the thermalhydraulic safety of the containment of light water reactors (LWRs). The results obtained form an extensive database especially valuable for the assessment of the capabilities of three-dimensional simulation tools. The present work reports on a specific test series of the aforementioned experimental program, the so-called Free-Plume Series featuring vertical injection of buoyant steam driving the gas transport. The experimental data is presented showing its quality and the trends in the experiments are analyzed. The phenomena whose prediction might be challenging for codes are emphasized. After the expiration of the confidentiality period, the experimental data is now available for the broad scientific community to be used for code validation purposes.
Fluid flow from a low to a higher density liquid
Weinberg, F.
1984-12-01
The penetration of liquid from a low density brine solution into a higher density solution below it has been measured as a function of vertical flow velocity and the density difference of the two solutions. The flow velocity was produced by a horizontal disc rotating in the low density liquid. The results show the penetration distance and penetration rate are dependent on flow velocity and in particular are very sensitive to small changes in the density difference between the two liquids. The observations are considered in relation to liquid penetration into dendritic arrays, and fluid flow in the pool of ingots and continuously cast steel billets, during solidification.
Andrews, Benjamin J.; Manga, Michael
2012-05-01
Laboratory density currents comprising warm talc powder turbulently suspended in air simulate many aspects of dilute pyroclastic density currents (PDCs) and demonstrate links between bulk current behavior, sedimentation, and turbulent structures. The densimetric and thermal Richardson, Froude, Stokes, and settling numbers match those of natural PDCs as does the ratio of thermal to kinetic energy density. The experimental currents have lower bulk Reynolds numbers than natural PDCs, but the experiments are fully turbulent. Consequently, the experiments are dynamically similar to the dilute portions of some natural currents. In general, currents traverse the floor of the experimental tank, sedimenting particles and turbulently entraining, heating, and thermally expanding air until all particle sediments or the currents become buoyant and lift off to form coignimbrite plumes. When plumes form, currents often undergo local flow reversals. Current runout distance and liftoff position decrease with increasing densimetric Richardson number and thermal energy density. As those parameters increase, total sedimentation decreases such that > 50% of initial current mass commonly fractionates into the plumes, in agreement with some observations of recent volcanic eruptions. Sedimentation profiles are best described by an entraining sedimentation model rather than the exponential fit resulting from non-entraining box models. Time series analysis shows that sedimentation is not a constant rate process in the experiments, but rather occurs as series of sedimentation-erosion couplets that propagate across the tank floor tracking current motion and behavior. During buoyant liftoff, sedimentation beneath the rising plumes often becomes less organized. Auto-correlation analysis of time series of particle concentration is used to characterize the turbulent structures of the currents and indicates that currents quickly partition into a slow-moving upper portion and faster, more
Molecular Density Functional Theory of Water
Jeanmairet, Guillaume; Vuilleumier, Rodolphe; Borgis, Daniel; 10.1021/jz301956b
2013-01-01
Three dimensional implementations of liquid state theories offer an efficient alternative to computer simulations for the atomic-level description of aqueous solutions in complex environments. In this context, we present a (classical) molecular density functional theory (MDFT) of water that is derived from first principles and is based on two classical density fields, a scalar one, the particle density, and a vectorial one, the multipolar polarization density. Its implementation requires as input the partial charge distribution of a water molecule and three measurable bulk properties, namely the structure factor and the k-dependent longitudinal and transverse dielectric constants. It has to be complemented by a solute-solvent three-body term that reinforces tetrahedral order at short range. The approach is shown to provide the correct three-dimensional microscopic solvation profile around various molecular solutes, possibly possessing H-bonding sites, at a computer cost two-three orders of magnitude lower tha...
Wetting in electrolyte solutions.
Ibagon, Ingrid; Bier, Markus; Dietrich, S
2013-06-01
Wetting of a charged substrate by an electrolyte solution is investigated by means of classical density functional theory applied to a lattice model. Within the present model the pure, i.e., salt-free solvent, for which all interactions are of the nearest-neighbor type only, exhibits a second-order wetting transition for all strengths of the substrate-particle and the particle-particle interactions for which the wetting transition temperature is nonzero. The influences of the substrate charge density and of the ionic strength on the wetting transition temperature and on the order of the wetting transition are studied. If the substrate is neutral, the addition of salt to the solvent changes neither the order nor the transition temperature of the wetting transition of the system. If the surface charge is nonzero, upon adding salt this continuous wetting transition changes to first-order within the wide range of substrate surface charge densities and ionic strengths studied here. As the substrate surface charge density is increased, at fixed ionic strength, the wetting transition temperature decreases and the prewetting line associated with the first-order wetting transition becomes longer. This decrease of the wetting transition temperature upon increasing the surface charge density becomes more pronounced by decreasing the ionic strength. PMID:23758391
Energy Technology Data Exchange (ETDEWEB)
Vagner, G.R.; Garaev, A.S.; Guzenko, L.P.; Khaber, N.V.; Kruglitskii, N.N.; Kurochkin, B.M.; Shumilov, V.A.
1981-03-23
Proposed is a plugging solution which contains cement, hydrophilic biosilica, polymer, and water, and which is distinguished by the fact that in order to increase the strength properties of the stone with simultaneous increase in its resistance to the effect of corrosive bed water under conditions of normal temperatures, as hydrophilic biosilica the solution contains carboxy aerosil or aminoethoxy aerosil, and as a polymer, carboxylate divinyl styrene latex and it also contains sodium with the following ingredient ratio, wt %: 63.47-66.08% cement, 0.66-1.28% carboxylate divinyl styrene latex, 1.26-1.32% sodium chloride, 0.22-0.36% carboxy aerosil or aminoethoxy aerosil, and the rest water. The plugging solution is distinguished by the fact that carboxy aerosil or aminoethoxy aerosil have a specific surface of 50-300 m/g.
Energy Technology Data Exchange (ETDEWEB)
Sharipov, A.U.; Polyakov, V.N.; Yangirova, I.Z.
1982-06-10
Proposed is a plugging solution containing cement, modified methyl cellulose, and water. In order to decrease the viscosity in time with the preservation of filtration and strength properties of the solution and stone, it also contains wastes of the production of 4,4-dimethyl dioxane-1,3 with following ratio of components, mass%: 66.0-67.0% cement; 0.07-0.15 modified methyl cellulose, 0.13-0.33% wastes from the production of 4,4-dimethyl dioxane-1,3, and the rest water.
On the Methodology of Nematode Extraction from Field Samples: Density Flotation Techniques
Viglierchio, David R.; Yamashita, Tom T.
1983-01-01
Density flotation has been frequently used for the extraction of nematodes from field samples. Density flotation curves for four nematode species and five solutes have been prepared. The curves confirm that flotation was governed by several factors: solute density, solute osmotic activity, and physiological properties of the nematode species. Nematode viability and function can be adversely affected by improper selection of solute for density extraction of nematodes; nevertheless, some nemato...
Directory of Open Access Journals (Sweden)
Reza A Zoroofi
2007-08-01
Full Text Available Medal Electronic (ME Engineering Company provides high quality systems, software and services in medical image management, processing and visualization. We assist health care professionals to improve and extend the efficiency of their practices with cost effective solutions. ME is the developer of several medical software including MEDAL-PACS, 3D-Sonosoft, Analytical-Electrophoresis, CBONE and Rhino-Plus. ME is also the exclusive distributor of PACSPLUS in Iran. PACSPLUS is an international, standard, scalable and enterprise PACS solution. PACSPLUS is of ISO, CE and FDA-510 approvals. It is now operational in more than 1000 clinical environment throughout the globe. We discuss about the key features of PACSPLUS system for dealing with real world challenge in PACS as well as the PACS solu-tions needed to fulfill the demands of the clinicians in Iran. Our experience in developing high-end medical software confirms our capability in providing the PACSPLUS as an ultimate PACS solution in Iran.
Geoghegan, Michael W
2005-01-01
Podcasting is the art of recording radio show style audio tracks, then distributing them to listeners on the Web via podcasting software such as iPodder. From downloading podcasts to producing a track for fun or profit, ""Podcast Solutions"" covers the entire world of podcasting with insight, humor, and the unmatched wisdom of experience.
Generalized density functional theory for effective potentials
International Nuclear Information System (INIS)
We demonstrate the existence of different density functionals that retain selected properties of the many-body ground state in the non-interacting density functional solution. We focus on diffusion Monte Carlo applications that require trial wave functions with Fermion optimal nodes. The theory can be extended and used to understand current practices in several electronic structure methods [GW-BSE,CI,EPM] within a generalized density functional framework. The theory justifies and stimulates the search of optimal empirical density functionals and effective potentials but also cautions on the limits of their applicability. The theoretical concepts are tested against a near-analytic model that can be solved to numerical precision
Energy Technology Data Exchange (ETDEWEB)
Veronica E. Wannberg, Gustavious Williams, Patrick Sawyer, and Richard Venedam
2010-09-01
Aunique field dataset from a series of low–wind speed experiments, modeling efforts using three commonly used models to replicate these releases, and statistical analysis of how well these models were able to predict the plume concentrations is presented. The experiment was designed to generate a dataset to describe the behavior of gaseous plumes under low-wind conditions and the ability of current, commonly used models to predict these movements. The dataset documents the release and transport of three gases: ammonia (buoyant), ethylene (neutral), and propylene (dense) in low–wind speed (diffusion) conditions. Release rates ranged from 1 to 20 kg h21. Ammonia and ethylene had five 5-min releases each to represent puff releases and five 20-min releases each to represent plume releases. Propylene had five 5-min puffs, six 20-min plumes, and a single 30-min plume. Thirty-two separate releases ranging from 6 to 47 min were conducted, of which only 30 releases generated useful data. The data collected included release rates, atmospheric concentrations to 100 m from the release point, and local meteorological conditions. The diagnostics included nine meteorological stations on 100-m centers and 36 photoionization detectors in a radial pattern. Three current stateof- the-practice models, Aerial locations of Hazardous Atmospheres (ALOHA), Emergency Prediction Information code (EPIcode), and Second-Order Closure Integrated Puff (SCIPUFF), were used to try to duplicate the measured field results. Low wind speeds are difficult to model, and all of the models had difficulty replicating the field measurements. However, the work does show that these models, if used correctly, are conservative (overpredict concentrations) and can be used for safety and emergency planning.
Laboratory Density Functionals
Giraud, B. G.
2007-01-01
We compare several definitions of the density of a self-bound system, such as a nucleus, in relation with its center-of-mass zero-point motion. A trivial deconvolution relates the internal density to the density defined in the laboratory frame. This result is useful for the practical definition of density functionals.
Hill, Colin
2010-01-01
Recently we reported a role for compatible solute uptake in mediating bile tolerance and increased gastrointestinal persistence in the foodborne pathogen Listeria monocytogenes.1 Herein, we review the evolution in our understanding of how these low molecular weight molecules contribute to growth and survival of the pathogen both inside and outside the body, and how this stress survival mechanism may ultimately be used to target and kill the pathogen. PMID:21326913
Radiographic solution contamination.
Hardman, P K; Tilmon, M F; Taylor, T S
1987-06-01
Contamination of processor solutions adversely affects the image quality of radiographic films. The purpose of this study was to determine the amount of developer or fixer contaminant that was necessary to produce a significant densitometric change in the base plus fog, speed, or contrast optical density readings for panoramic film. Significant differences in base plus fog (after 16 mL of fixer contaminant was added to developer), speed index (after 4 mL), and contrast index (after 8 mL) were observed in comparison with control values. PMID:3473399
Energy Technology Data Exchange (ETDEWEB)
Rosales, Mauricio F. [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
1987-12-31
This article is based in the electromagnetic modeling presented in the first part. Here are only considered the magnetic systems or electric systems in closed regions with moving or axial symmetry, whose total current density or total electric load density is known. The algorithms that have been implanted in the software CLIIE-2D of the Instituto de Investigaciones Electricas (IIE) are developed in order to obtain numerical solutions for these problems. The basic systems of algebraic equations are obtained by means of the application of the Galerkin method in the discreteness of the finite element with first order triangular elements. [Espanol] Este articulo se basa en la modelacion electromagnetica presentada en la primera parte. Aqui solo se consideran sistemas magneticos o sistemas electricos en regiones cerradas con simetria translacional o axial, cuya densidad de corriente total o densidad de carga electrica total es conocida. Se desarrollan los algoritmos que se han implantado en el programa de computo CLIIE-2D, del Instituto de Investigaciones Electricas (IIE) con el fin de obtener soluciones numericas para estos problemas. Los sistemas basicos de ecuaciones algebraicas se obtienen mediante la aplicacion del metodo de Galerkin en la discretizacion de elemento finito con elementos triangulares de primer orden.
DEFF Research Database (Denmark)
Efeoglu, Arkin; Møller, Charles; Serie, Michel
2013-01-01
environment. The solution prototype that is composed from blending product and service prototype has particular impacts on the dualism of DSR’s “Build” and “Evaluate”. Since the mix between product and service prototyping can be varied, there is a demand for a more agile and iterative framework. Van de Ven......’s research framework seems to fit this purpose. Van de Ven allows for an iterative research approach to problem solving with flexible starting point. The research activity is the result between the iteration of two dimensions. This framework focuses on the natural evaluation, particularly on ex...
2012-01-01
Multilingual Solutions ofrecera capacitación a los agentes de Contact y Call centers de Bogotá con dominio de una segunda lengua. La capacitación consiste en mejorar las falencias comunicativas que se presentan en empresas de este tipo, y así optimizar los servicios de estas compañías por medio de mejoras en el servicio prestado por sus agentes; siendo estas las características que la hacen diferente de las demás empresas prestadoras de servicios de capacitación. Con base a los estudios reali...
Calculation of criticality parameters for uranium and/or plutonium nitrate solutions, 1
International Nuclear Information System (INIS)
For the purpose of computing criticality parameters of the solutions with uranium and plutonium, the atomic number density was formulated and programmed in the computer. The amount of solvent in the solution was calculated from solute concentration and density of the solution. The numerical expression of the solution density was based on the literature data for aqueous nitrate solution, and on theoretical consideration for 30% TBP-n. dodecane solution. The calculated values of solution density were discussed compared with that in ARH-600, the criticality handbook in the United States. (author)
Induced gravity from curvature density preserving diffeomorphisms
Oda, Ichiro
2016-08-01
We construct not only an induced gravity model with restricted diffeomorphisms, that is, transverse diffeomorphisms that preserve the curvature density, but also with full diffeomorphisms. By solving the equations of motion, it turns out that these models produce Einstein's equations with a certain Newton constant in addition to the constraint for the curvature density. In the limit of the infinite Newton constant, the models give rise to induced gravity. Moreover, we discuss cosmological solutions on the basis of the gravitational models at hand.
U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...
Density fluctuations of polymers in disordered media
Energy Technology Data Exchange (ETDEWEB)
Deutsch, Joshua M.; Olvera de la Cruz, Monica
2011-03-02
We study self-avoiding random walks in an environment where sites are excluded randomly, in two and three dimensions. For a single polymer chain, we study the statistics of the time averaged monomer density and show that these are well described by multifractal statistics. This is true even far from the percolation transition of the disordered medium. We investigate solutions of chains in a disordered environment and show that the statistics cease to be multifractal beyond the screening length of the solution.
Francis X. Diebold; Todd A. Gunther; Anthony S. Tay
1997-01-01
The authors propose methods for evaluating and improving density forecasts. They focus primarily on methods that are applicable regardless of the particular user's loss function, though they take explicit account of the relationships between density forecasts, action choices, and the corresponding expected loss throughout. They illustrate the methods with a detailed series of examples, and they discuss extensions to improving and combining suboptimal density forecasts, multistep-ahead density...
Chun, Tiejun; Zhu, Deqing; Pan, Jian; He, Zhen
2014-06-01
Recovery of alumina from magnetic separation tailings of red mud has been investigated by Na2CO3 solution leaching. X-ray diffraction (XRD) results show that most of the alumina is present as 12CaO·7Al2O3 and CaO·Al2O3 in the magnetic separation tailings. The shrinking core model was employed to describe the leaching kinetics. The results show that the calculated activation energy of 8.31 kJ/mol is characteristic for an internal diffusion-controlled process. The kinetic equation can be used to describe the leaching process. The effects of Na2CO3 concentration, liquid-to-solid ratio, and particle size on recovery of Al2O3 were examined.
Communities of solutions in single solution clusters of a random K -satisfiability formula
Zhou, Haijun; Ma, Hui
2009-12-01
The solution space of a K -satisfiability (K-SAT) formula is a collection of solution clusters, each of which contains all the solutions that are mutually reachable through a sequence of single-spin flips. Knowledge of the statistical property of solution clusters is valuable for a complete understanding of the solution space structure and the computational complexity of the random K-SAT problem. This paper explores single solution clusters of random 3- and 4-SAT formulas through unbiased and biased random-walk processes and the replica-symmetric cavity method of statistical physics. We find that the giant connected component of the solution space has already formed many different communities when the constraint density of the formula is still lower than the solution space clustering transition point. Solutions of the same community are more similar with each other and more densely connected with each other than with the other solutions. The entropy density of a solution community is calculated using belief propagation and is found to be different for different communities of the same cluster. When the constraint density is beyond the clustering transition point, the same behavior is observed for the solution clusters reached by several stochastic search algorithms. Taking together, the results of this work suggest a refined picture on the evolution of the solution space structure of the random K-SAT problem; they may also be helpful for designing heuristic algorithms.
Exact and almost exact solution to Vlasov-Maxwell system
International Nuclear Information System (INIS)
Exact and almost exact solutions to the Vlasov-Maxwell systems describing a variety of plasma configurations with density, temperature and current gradients, are presented. Possible consequences of these solutions are also discussed. 6 refs., 8 figs
Dispersal and air entrainment in unconfined dilute pyroclastic density currents
Andrews, Benjamin J.
2014-09-01
Unconfined scaled laboratory experiments show that 3D structures control the behavior of dilute pyroclastic density currents (PDCs) during and after liftoff. Experiments comprise heated and ambient temperature 20 μm talc powder turbulently suspended in air to form density currents within an unobstructed 8.5 × 6 × 2.6-m chamber. Comparisons of Richardson, thermal Richardson, Froude, Stokes, and settling numbers and buoyant thermal to kinetic energy densities show good agreement between experimental currents and dilute PDCs. The experimental Reynolds numbers are lower than those of PDCs, but the experiments are fully turbulent; thus, the large-scale dynamics are similar between the two systems. High-frequency, simultaneous observation in three orthogonal planes shows that the currents behave very differently than previous 2D (i.e., confined) currents. Specifically, whereas ambient temperature currents show radial dispersal patterns, buoyancy reversal, and liftoff of heated currents focuses dispersal along narrow axes beneath the rising plumes. The aspect ratios, defined as the current length divided by a characteristic width, are typically 2.5-3.5 in heated currents and 1.5-2.5 in ambient temperature currents, reflecting differences in dispersal between the two types of currents. Mechanisms of air entrainment differ greatly between the two currents: entrainment occurs primarily behind the heads and through the upper margins of ambient temperature currents, but heated currents entrain air through their lateral margins. That lateral entrainment is much more efficient than the vertical entrainment, >0.5 compared to ˜0.1, where entrainment is defined as the ratio of cross-stream to streamwise velocity. These experiments suggest that generation of coignimbrite plumes should focus PDCs along narrow transport axes, resulting in elongate rather than radial deposits.
Probability densities and Lévy densities
DEFF Research Database (Denmark)
Barndorff-Nielsen, Ole Eiler
For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated.......For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated....
Incompressible flows with piecewise constant density
Danchin, Raphaël
2012-01-01
We investigate the incompressible Navier-Stokes equations with variable density. The aim is to prove existence and uniqueness results in the case of discontinuous ini- tial density. In dimension n = 2, 3, assuming only that the initial density is bounded and bounded away from zero, and that the initial velocity is smooth enough, we get the local-in-time existence of unique solutions. Uniqueness holds in any dimension and for a wider class of velocity fields. Let us emphasize that all those results are true for piecewise constant densities with arbitrarily large jumps. Global results are established in dimension two if the density is close enough to a positive constant, and in n-dimension if, in addition, the initial velocity is small. The Lagrangian formula- tion for describing the flow plays a key role in the analysis that is proposed in the present paper.
Morris, Simon Conway
2004-11-01
Life's Solution builds a persuasive case for the predictability of evolutionary outcomes. The case rests on a remarkable compilation of examples of convergent evolution, in which two or more lineages have independently evolved similar structures and functions. The examples range from the aerodynamics of hovering moths and hummingbirds to the use of silk by spiders and some insects to capture prey. Going against the grain of Darwinian orthodoxy, this book is a must read for anyone grappling with the meaning of evolution and our place in the Universe. Simon Conway Morris is the Ad Hominen Professor in the Earth Science Department at the University of Cambridge and a Fellow of St. John's College and the Royal Society. His research focuses on the study of constraints on evolution, and the historical processes that lead to the emergence of complexity, especially with respect to the construction of the major animal body parts in the Cambrian explosion. Previous books include The Crucible of Creation (Getty Center for Education in the Arts, 1999) and co-author of Solnhofen (Cambridge, 1990). Hb ISBN (2003) 0-521-82704-3
Lithium-Based High Energy Density Flow Batteries
Bugga, Ratnakumar V. (Inventor); West, William C. (Inventor); Kindler, Andrew (Inventor); Smart, Marshall C. (Inventor)
2014-01-01
Systems and methods in accordance with embodiments of the invention implement a lithium-based high energy density flow battery. In one embodiment, a lithium-based high energy density flow battery includes a first anodic conductive solution that includes a lithium polyaromatic hydrocarbon complex dissolved in a solvent, a second cathodic conductive solution that includes a cathodic complex dissolved in a solvent, a solid lithium ion conductor disposed so as to separate the first solution from the second solution, such that the first conductive solution, the second conductive solution, and the solid lithium ionic conductor define a circuit, where when the circuit is closed, lithium from the lithium polyaromatic hydrocarbon complex in the first conductive solution dissociates from the lithium polyaromatic hydrocarbon complex, migrates through the solid lithium ionic conductor, and associates with the cathodic complex of the second conductive solution, and a current is generated.
The role of adequate reference materials in density measurements in hemodialysis
International Nuclear Information System (INIS)
In hemodialysis, oscillation-type density meters are used to measure the density of the acid component of the dialysate solutions used in the treatment of kidney patients. An incorrect density determination of this solution used in hemodialysis treatments can cause several and adverse events to patients. Therefore, despite the Fresenius Medical Care (FME) tight control of the density meters calibration results, this study shows the benefits of mimic the matrix usually measured to produce suitable reference materials for the density meter calibrations
Quasiperiodic packing densities
International Nuclear Information System (INIS)
The problem of the packing density on quasiperiodic lattices is discussed in a systematic way using projection techniques. For compact domains a direct construction is presented using a Voronoi construction on a quasilattice in perpendicular space defined by the forbidden volume of the packed objects. A generalized inflation law, valid for arbitrary shapes of the acceptance domain using the properties of linear mappings of the hyperlattice on itself which commute with the symmetry group, is used to show that the packing densities and the whole structure of the projected quasilattice are periodic under scale transformations. We find the optimal compact acceptance domains and packing densities for several icosahedral problems. For the packing of spheres on the primitive lattice, an icosahedron and the truncated triacontahedron give equal densities but different quasilattices. For the packing of icosahedra one finds only the second lattice and a very high density. For the fcc and bcc lattices the maximum density acceptance domain is a triacontahedron and the densities are considerably lower. The results of Henley for including correlations to increase the density are reformulated in terms of a graph problem in perpendicular space. Including only the graphs equivalent to his, we find the same packing density for the two primitive and for the fcc lattice. It is shown that a generalization leads to an interesting and very complex problem in graph theory which we are unable to solve
Anisotropic dynamic mass density for fluidsolid composites
Wu, Ying
2012-10-01
By taking the low frequency limit of multiple-scattering theory, we obtain the dynamic effective mass density of fluidsolid composites with a two-dimensional rectangular lattice structure. The anisotropic mass density can be described by an angle-dependent dipole solution, to the leading-order of solid concentration. The angular dependence vanishes for the square lattice, but at high solid concentrations there is a structure-dependent factor that contributes to the leading-order solution. In all cases, Woods formula is found to be accurately valid for the effective bulk modulus, independent of the structures. Numerical evaluations from the solutions are shown to be in excellent agreement with finite-element simulations. © 2012 Elsevier B.V.
Institute of Scientific and Technical Information of China (English)
曹轲; 任凤章; 王天军; 刘治军; 田保红; 李武会
2012-01-01
四阶Runge-Kutta法是工程计算中常用的一种求解微分方程的数值计算方法,具有精度高,易收敛等优点.本文在Feynman等人计算方法的基础上,用经典的四阶Runge-Kutta法来求解Thomas-Fermi-Dirac (TFD)方程,进一步提高原计算方法的计算精度.利用该方法求出了元素Cu的TFD方程数值解并计算出一些常见元素在Wigner-Seitz半径处的电子密度.%Fourth order Runge-Kutta method is commonly used to solve the differential equations in engineering due to its high precision and easy convergence. In this paper, based on the Feynman et al.'s calculated method, the classical fourth order Runge-Kutta method was applied to solve the Thomas-Fermi-Dirac (TFD) equation and more accurate results have been obtained. Using this method, the numerical solution of the TFD equation for the element Cu was solved, and the electron density values of some common elements at the Wigner-Seitz radius were calculated.
Institute of Scientific and Technical Information of China (English)
冯跟胜; 党金春; 等
1995-01-01
A method used for on line determining the change of wheat density with a automatic watering machine in a lqarge flour mill has been studied.The results show that the higher distinguishing ability is obtained when using 241Am as a γ-ray source for measuring the wheat density than using 137Cs.
International Nuclear Information System (INIS)
The performance of approximations to the Hohenberg-Kohn-Sham density functionals is tested by comparing with essentially exact results for light atoms (the He isoelectronic series, Be, and Ne). The approximation schemes considered here are the effective gradient schemes due to Langreth and Mehl (LM), and the -modified weighted density- (MWD) approximation due to Gunnarsson and Jones. Compared to the local-density (LD) approximation the LM schemes give markedly better exchange-correlation energies and a certain improvement of density profiles, effective potentials, and orbital eigenvalues. The MWD scheme gives improvements for the exchange-correlation energies but not for the densities, potentials, or eigenvalues. The sensitivity of the MWD scheme with respect to the model pair correlation used, as well as some additional approximations used in practical applications of the MWD scheme, are also analysed. (author)
Learning Grasp Affordance Densities
DEFF Research Database (Denmark)
Detry, Renaud; Kraft, Dirk; Kroemer, Oliver;
2011-01-01
records their outcomes. When a satisfactory number of grasp data is available, an importance-sampling algorithm turns these into a grasp density. We evaluate our method in a largely autonomous learning experiment run on three objects of distinct shapes. The experiment shows how learning increases success......We address the issue of learning and representing object grasp affordance models. We model grasp affordances with continuous probability density functions (grasp densities) which link object-relative grasp poses to their success probability. The underlying function representation is nonparametric...... and relies on kernel density estimation to provide a continuous model. Grasp densities are learned and refined from exploration, by letting a robot “play” with an object in a sequence of graspand-drop actions: The robot uses visual cues to generate a set of grasp hypotheses; it then executes these and...
Solute-vacancy binding in aluminum
International Nuclear Information System (INIS)
Previous efforts to understand solute-vacancy binding in aluminum alloys have been hampered by a scarcity of reliable, quantitative experimental measurements. Here, we report a large database of solute-vacancy binding energies determined from first-principles density functional calculations. The calculated binding energies agree well with accurate measurements where available, and provide an accurate predictor of solute-vacancy binding in other systems. We find: (i) some common solutes in commercial Al alloys (e.g., Cu and Mg) possess either very weak (Cu), or even repulsive (Mg), binding energies. Hence, we assert that some previously reported large binding energies for these solutes are erroneous. (ii) Large binding energies are found for Sn, Cd and In, confirming the proposed mechanism for the reduced natural aging in Al-Cu alloys containing microalloying additions of these solutes. (iii) In addition, we predict that similar reduction in natural aging should occur with additions of Si, Ge and Au. (iv) Even larger binding energies are found for other solutes (e.g., Pb, Bi, Sr, Ba), but these solutes possess essentially no solubility in Al. (v) We have explored the physical effects controlling solute-vacancy binding in Al. We find that there is a strong correlation between binding energy and solute size, with larger solute atoms possessing a stronger binding with vacancies. (vi) Most transition-metal 3d solutes do not bind strongly with vacancies, and some are even energetically strongly repelled from vacancies, particularly for the early 3d solutes, Ti and V
Inner magnetosphere plasma densities
International Nuclear Information System (INIS)
The radio plasma imager (RPI) on the IMAGE satellite performs radio sounding in the magnetosphere, transmitting coded signals stepping through the frequency range of interest and receiving the returned echoes. The measurements provide the echo amplitude as a function of frequency and echo delay time on a so-called plasmagram. A newly developed algorithm inverts THE echo traces on a plasmagram to electron density spatial distributions. Based on these observed density distributions, an empirical model is constructed to describe the two-dimensional density distribution in the inner magnetosphere. (author)
Electronic states density and solution volume of hydrogen solution in SiC alloys
International Nuclear Information System (INIS)
The new reactor concepts are characterized by higher efficiency, better utilization of nuclear fuel and nuclear waste minimization. This approach means that this will be to enter a new and deep structural analysis of materials with a tensile strength significantly higher than those currently used radiation. To achieve high performance parameters, continuous research and testing of new materials will be needed. In this paper we concentrate on the analysis of SiC alloys, because due to their unique properties, this alloy can be used in high temperature conditions, where the silicon, semiconductor material of choice does not work (author)
... Paula FJA, Black DM, Rosen CJ. Osteoporosis and bone biology.In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology . 13th ed. Philadelphia, ... Bone-density testing interval and transition to osteoporosis in ...
BMD test; Bone density test; Bone densitometry; DEXA scan; DXA; Dual-energy x-ray absorptiometry; p-DEXA; Osteoporosis-BMD ... need to undress. This scan is the best test to predict your risk of fractures. Peripheral DEXA ( ...
... Density Clues to Emerging Drug-Resistant Malaria Molecular Effects of Social Stress Connect with Us Subscribe to get NIH Research Matters by email RSS Feed Facebook Email us Mailing Address: NIH Research Matters Bldg. ...
Nuclear level density predictions
Bucurescu Dorel; von Egidy Till
2015-01-01
Simple formulas depending only on nuclear masses were previously proposed for the parameters of the Back-Shifted Fermi Gas (BSFG) model and of the Constant Temperature (CT) model of the nuclear level density, respectively. They are now applied for the prediction of the level density parameters of all nuclei with available masses. Both masses from the new 2012 mass table and from different models are considered and the predictions are discussed in connection with nuclear regions most affected ...
Vranjes, J.; Kono, M
2015-01-01
Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindric configuration. This is of practical importance for drift wave instability in various plasmas, and in partic...
ADN* Density log estimation Using Rockcell*
International Nuclear Information System (INIS)
This work is intended to inform on the possibilities of estimating good density data in zones associated with sliding in a reservoir with ADN* tool with or without ADOS in string in cases where repeat sections were not done, possibly due to hole stability or directional concerns. This procedure has been equally used to obtain a better density data in corkscrew holes. Density data (ROBB) was recomputed using neural network in RockCell* to estimate the density over zones of interest. RockCell* is a Schlumberger software that has neural network functionally which can be used to estimate missing logs using the combination of the responses of other log curves and intervals that are not affected by sliding. In this work, an interval was selected and within this interval twelve litho zones were defined using the unsupervised neural network. From this a training set was selected based on intervals of very good log responses outside the sliding zones. This training set was used to train and run the neural network for a specific lithostratigraphic interval. The results matched the known good density curve. Then after this, an estimation of the density curve was done using the supervised neural network. The output from this estimation matched very closely in the good portions of the log, thus providing some density measurements in the sliding zone. This methodology provides a scientific solution to missing data during the process of Formation evaluation
Anisotropic static solutions in modelling highly compact bodies
Indian Academy of Sciences (India)
M Chaisi; S D Maharaj
2006-03-01
Einstein field equations for static anisotropic spheres are solved and exact interior solutions obtained. This paper extends earlier treatments to include anisotropic models which accommodate a wider variety of physically viable energy densities. Two classes of solutions are possible. The first class contains the limiting case ∝ -2 for the energy density which arises in many astrophysical applications. In the second class the singularity at the centre of the star is not present in the energy density
Density Waves in Layered Systems with Fermionic Polarmolecules
DEFF Research Database (Denmark)
Zinner, Nikolaj Thomas; Bruun, Georg
A layered system of two-dimensional planes containing fermionic polar molecules can potentially realize a number of exotic quantum many-body states. Among the predictions, are density-wave instabilities driven by the anisotropic part of the dipole-dipole interaction in a single layer. However, in...... typical multilayer setups it is reasonable to expect that the onset and properties of a density-wave are modified by adjacent layers. Here we show that this is indeed the case. For multiple layers the critical strength for the density-wave instability decreases with the number of layers. The effect...... depends on density and is more pronounced in the low density regime. The lowest solution of the instability corresponds to the density waves in the different layers being in-phase, whereas higher solutions have one or several adjacent layers that are out of phase. The parameter regime needed to explore...
Conserved Densities of the Black-Scholes Equation
Institute of Scientific and Technical Information of China (English)
QIN Mao-Chang; MEI Feng-Xiang; SHANG Mei
2005-01-01
@@ A class of new conserved densities of the Black-Scholes equation are constructed by using the multiplier that is derived from the result of divergence expression annihilation under the full Euler operator.The method does not depend on the symmetries of the Black-Scholes equation.These conserved densities can be expressed by solutions of the classical heat equation.
Limiting current density and water dissociation in bipolar membranes
Strathmann, H.; Krol, J.J.; Rapp, H.-J.; Eigenberger, G.
1997-01-01
The behaviour of bipolar membranes in NaCl and Na2SO4 solutions is discussed. The membranes are characterized in terms of their limiting current densities. Below the limiting current density the electric current is carried by salt ions migrating from the transition region between the anion and the c
Bayes Methods for a Symmetric Unimodal Density and its Mode
Brunner, Lawrence J.; Lo, Albert Y.
1989-01-01
Bayes solutions for i.i.d. sampling from a decreasing density on the half line and for i.i.d. sampling from a symmetric unimodal density with an unknown mode are given. Posterior quantities are obtained as finite sums; Monte Carlo methods based on sampling finite Markov chains are developed for their evaluation.
Density fluctuations of polymers in disordered media.
Deutsch, J M; de la Cruz, M Olvera
2011-03-01
We study self-avoiding random walks in an environment where sites are excluded randomly, in two and three dimensions. For a single polymer chain, we study the statistics of the time averaged monomer density and show that these are well described by multifractal statistics. This is true even far from the percolation transition of the disordered medium. We investigate solutions of chains in a disordered environment and show that the statistics cease to be multifractal beyond the screening length of the solution. PMID:21517516
2001-01-01
In this note we introduce an egalitarian solution, called the dual egalitarian solution, that is the natural counterpart of the egalitarian solution of Dutta and Ray (1989). We prove, among others, that for a convex game the egalitarian solution coincides with the dual egalitarian solution for its dual concave game.
Klijn, F.; Slikker, M.; Tijs, S.H.
2000-01-01
In this note we introduce an egalitarian solution, called the dual egalitarian solution, that is the natural counterpart of the egalitarian solution of Dutta and Ray (1989).We prove, among others, that for a convex game the egalitarian solution coincides with the dual egalitarian solution for its dual concave game.
Directory of Open Access Journals (Sweden)
Stone J.R.
2013-12-01
Full Text Available The microscopic composition and properties of matter at super-saturation densities have been the subject of intense investigation for decades. The scarcity of experimental and observational data has led to the necessary reliance on theoretical models. There remains great uncertainty in these models which, of necessity, have to go beyond the over-simple assumption that high density matter consists only of nucleons and leptons. Heavy strange baryons, mesons and quark matter in different forms and phases have to be included to fulfil basic requirements of fundamental laws of physics. In this contribution latest developments in construction of the Equation of State (EoS of high-density matter at zero and finite temperature assuming different composition of matter will be discussed. Critical comparison of model EoS with available experimental data from heavy ion collisions and observations on neutron stars, including gravitational mass, radii and cooling patterns and data on X-ray burst sources and low mass X-ray binaries are made. Fundamental differences between the EoS of low-density, high temperature matter, such as is created in heavy ion collisions and of high-density, low temperature compact objects is discussed.
Demonstration of de novo synthesis of enzymes by density labelling with stable isotopes
International Nuclear Information System (INIS)
The technique of in vivo density labelling of proteins with H218O and 2H2O has been used to investigate hormonal regulation and developmental expression of enzymes in plant cells. Buoyant density data obtained from isopycnic equilibrium centrifugation demonstrated that the cytokinine-induced nitrate reductase activity and the gibberellic acid-induced phosphatase activity in isolated embryos of Agrostemma githago are activities of enzymes synthesized de novo. The increase in alanine-specific aminopeptidase in germinating A. githago seeds is not due to de novo synthesis but to the release of preformed enzyme. On the basis of this result it is possible to apply the enzyme aminopeptidase as an internal density standard in equilibrium centrifugation. Density labelling experiments on proteins in pea cotyledons have been used to study the change in the activity of acid phosphatase, alanine-specific aminopeptidase, and peroxidase during germination. The activities of these enzymes increase in cotyledons of Pisum sativum. Density labelling by 18O and 2H demonstrates de novo synthesis of these three enzymes. The differential time course of enzyme induction shows the advantage of using H218O as labelling substance in cases when the enzyme was synthesized immediately at the beginning of germination. At this stage of development the amino-acid pool available for synthesis is formed principally by means of hydrolysis of storage proteins. The incorporation of 2H into the new proteins takes place in a measurable amount at a stage of growth in which the amino acids are also synthesized de novo. The enzyme acid phosphatase of pea cotyledons was chosen to demonstrate the possibility of using the density labelling technique to detect protein turnover. (author)
Stone, J R
2013-01-01
The microscopic composition and properties of matter at super-saturation densities have been the subject of intense investigation for decades. The scarcity of experimental and observational data has lead to the necessary reliance on theoretical models. However, there remains great uncertainty in these models, which, of necessity, have to go beyond the over-simple assumption that high density matter consists only of nucleons and leptons. Heavy strange baryons, mesons and quark matter in different forms and phases have to be included to fulfil basic requirements of fundamental laws of physics. In this review the latest developments in construction of the Equation of State (EoS) of high-density matter at zero and finite temperature assuming different composition of the matter are surveyed. Critical comparison of model EoS with available observational data on neutron stars, including gravitational masses, radii and cooling patterns is presented. The effect of changing rotational frequency on the composition of ne...
Density Distribution Sunflower Plots
Dupont, William D.; W. Dale Plummer Jr.
2003-01-01
Density distribution sunflower plots are used to display high-density bivariate data. They are useful for data where a conventional scatter plot is difficult to read due to overstriking of the plot symbol. The x-y plane is subdivided into a lattice of regular hexagonal bins of width w specified by the user. The user also specifies the values of l, d, and k that affect the plot as follows. Individual observations are plotted when there are less than l observations per bin as in a conventio...
International Nuclear Information System (INIS)
In next-to-leading order quantum chromodynamics, gluon-gluon interactions dominate the production of bottom quarks at hadron collider energies, and gluon-quark interactions control inclusive prompt photon production at large transverse momentum in pp collisions at fixed-target energies. Using such data, in conjunction with data from deep inelastic lepton scattering, we determine a new gluon density whose shape differs substantially from that derived from previous fits of data. The new set of parton densities provides a good fit to bottom quark, prompt photon, and deep inelastic data, including the most recent NMC and CCFR results
International Nuclear Information System (INIS)
Experimental data show that the number of nuclear states increases rapidly with increasing excitation energy. The properties of highly excited nuclei are important for many nuclear reactions, mainly those that go via processes of the compound nucleus type. In this case, it is sufficient to know the statistical properties of the nuclear levels. First of them is the function of nuclear levels density. Several theoretical models which describe the level density are presented. The statistical mechanics and a quantum mechanics formalisms as well as semi-empirical results are analysed and discussed. (Author)
Multivariate density estimation theory, practice, and visualization
Scott, David W
1992-01-01
Written to convey an intuitive feel for both theory and practice, its main objective is to illustrate what a powerful tool density estimation can be when used not only with univariate and bivariate data but also in the higher dimensions of trivariate and quadrivariate information. Major concepts are presented in the context of a histogram in order to simplify the treatment of advanced estimators. Features 12 four-color plates, numerous graphic illustrations as well as a multitude of problems and solutions
Nuclear energy density optimization: Large deformations
Kortelainen, M.; McDonnell, J.; W. Nazarewicz; Reinhard, P. -G.; Sarich, J.; Schunck, N.; Stoitsov, M. V.; Wild, S. M.
2011-01-01
A new Skyrme-like energy density suitable for studies of strongly elongated nuclei has been determined in the framework of the Hartree-Fock-Bogoliubov theory using the recently developed model-based, derivative-free optimization algorithm POUNDerS. A sensitivity analysis at the optimal solution has revealed the importance of states at large deformations in driving the parameterization of the functional. The good agreement with experimental data on masses and separation energies, achieved with...
Solvation force between tethered polyelectrolyte layers. A density functional approach
Directory of Open Access Journals (Sweden)
O. Pizio
2012-10-01
Full Text Available We use a version of the density functional theory to study the solvation force between two plates modified with a tethered layer of chains. The chains are built of tangentially jointed charged spherical segments. The plates are immersed in an electrolyte solution that involves cations, anions and solvent molecules. The latter molecules are modelled as hard spheres. We study the dependence of the solvation force and the structure of chains and of solute molecules on the grafting density, length of chains, architecture of the chains and on concentration of the solute.
Force Density Balance inside the Hydrogen Atom
Himpsel, F J
2015-01-01
Motivated by the long-debated question about the internal stability of the electron, the force densities acting on the charge density of the 1s electron in the H atom are investigated. The problem is mapped onto the canonical formalism for a classical Dirac field coupled to the electric field of an external point charge. An explicit calculation shows that the attractive Coulomb force density is balanced exactly at every point in space by the repulsive confinement force density. The latter requires evaluating the divergence of the stress tensor for the 1s solution of the Dirac equation. Such a local force balance goes beyond the global stability criteria that are usually given for the H atom. This concept is extended to the internal stability of any charged particle by investigating the force densities acting on its surrounding vacuum polarization. At large distances one has to consider only the charge density of virtual electrons and positrons, induced by a point charge in the vacuum of quantum electrodynamic...
Combining Step Gradients and Linear Gradients in Density.
Kumar, Ashok A; Walz, Jenna A; Gonidec, Mathieu; Mace, Charles R; Whitesides, George M
2015-06-16
Combining aqueous multiphase systems (AMPS) and magnetic levitation (MagLev) provides a method to produce hybrid gradients in apparent density. AMPS—solutions of different polymers, salts, or surfactants that spontaneously separate into immiscible but predominantly aqueous phases—offer thermodynamically stable steps in density that can be tuned by the concentration of solutes. MagLev—the levitation of diamagnetic objects in a paramagnetic fluid within a magnetic field gradient—can be arranged to provide a near-linear gradient in effective density where the height of a levitating object above the surface of the magnet corresponds to its density; the strength of the gradient in effective density can be tuned by the choice of paramagnetic salt and its concentrations and by the strength and gradient in the magnetic field. Including paramagnetic salts (e.g., MnSO4 or MnCl2) in AMPS, and placing them in a magnetic field gradient, enables their use as media for MagLev. The potential to create large steps in density with AMPS allows separations of objects across a range of densities. The gradients produced by MagLev provide resolution over a continuous range of densities. By combining these approaches, mixtures of objects with large differences in density can be separated and analyzed simultaneously. Using MagLev to add an effective gradient in density also enables tuning the range of densities captured at an interface of an AMPS by simply changing the position of the container in the magnetic field. Further, by creating AMPS in which phases have different concentrations of paramagnetic ions, the phases can provide different resolutions in density. These results suggest that combining steps in density with gradients in density can enable new classes of separations based on density. PMID:25978093
Single-solution Random 3-SAT Instances
Znidaric, Marko
2005-01-01
We study a class of random 3-SAT instances having exactly one solution. The properties of this ensemble considerably differ from those of a random 3-SAT ensemble. It is numerically shown that the running time of several complete and stochastic local search algorithms monotonically increases as the clause density is decreased. Therefore, there is no easy-hard-easy pattern of hardness as for standard random 3-SAT ensemble. Furthermore, the running time for short single-solution formulas increas...
International Nuclear Information System (INIS)
In an attempt to optimise maintenance dredging in the port of Rotterdam a system which includes a radiation backscatter density gauge has been developed. The method described is fully operational with measurements being taken at 60 to 70 fixed sites daily. Advantages and disadvantages of the system are examined. (U.K.)
DEFF Research Database (Denmark)
Christensen, Ole; Heil, Christopher; Deng, Baiqiao
1999-01-01
Beurling densities of Lambda = boolean ORk=1r Lambda(k) satisfy D- (Lambda) greater than or equal to 1 and D+(Lambda) < infinity. This extends recent work of Ramanathan and Steger. Additionally, we prove the conjecture that no collection boolean ORk=1r {g(k)(x - a)}(a is an element of Gamma k) of pure...
Partition density functional theory
Nafziger, Jonathan
Partition density functional theory (PDFT) is a method for dividing a molecular electronic structure calculation into fragment calculations. The molecular density and energy corresponding to Kohn Sham density-functional theory (KS-DFT) may be exactly recovered from these fragments. Each fragment acts as an isolated system except for the influence of a global one-body 'partition' potential which deforms the fragment densities. In this work, the developments of PDFT are put into the context of other fragment-based density functional methods. We developed three numerical implementations of PDFT: One within the NWChem computational chemistry package using basis sets, and the other two developed from scratch using real-space grids. It is shown that all three of these programs can exactly reproduce a KS-DFT calculation via fragment calculations. The first of our in-house codes handles non-interacting electrons in arbitrary one-dimensional potentials with any number of fragments. This code is used to explore how the exact partition potential changes for different partitionings of the same system and also to study features which determine which systems yield non-integer PDFT occupations and which systems are locked into integer PDFT occupations. The second in-house code, CADMium, performs real-space calculations of diatomic molecules. Features of the exact partition potential are studied for a variety of cases and an analytical formula determining singularities in the partition potential is derived. We introduce an approximation for the non-additive kinetic energy and show how this quantity can be computed exactly. Finally a PDFT functional is developed to address the issues of static correlation and delocalization errors in approximations within DFT. The functional is applied to the dissociation of H2 + and H2.
Exact Solutions for Compact Objects in General Relativity
Raghoonundun, Ambrish M
2016-01-01
Seven new solutions to the interior static and spherically symmetric Einstein's field equations (EFE) are found and investigated. These new solutions are a generalisation of the quadratic density fall-off profile of the Tolman VII solution. The generalisation involves the addition of anisotropic pressures and electric charge to the density profile. Of these new solutions three are found to obey all the necessary conditions of physical acceptability, including linear stability under radial perturbations, and causality of the speed of pressure waves inside the object. Additionally an equation of state can be found for all the physically viable solutions. The generalised pulsation equation for interior solutions to the EFE that include both electric charge and pressure anisotropy is derived and used to determine the stability of the solutions. However the pulsation equation found is general and can be used for all new solutions that contain these ingredients.
Hadronic property at finite density
Takaishi, Tetsuya
2004-01-01
We report on three topics on finite density simulations: (i) the derivative method for hadronic quantities, (ii) phase fluctuations in the vicinity of the critical temperature and (iii) the density of states method at finite isospin density.
Density Adaptive Parallel Clustering
La Rocca, Marcello
2014-01-01
In this paper we are going to introduce a new nearest neighbours based approach to clustering, and compare it with previous solutions; the resulting algorithm, which takes inspiration from both DBscan and minimum spanning tree approaches, is deterministic but proves simpler, faster and doesnt require to set in advance a value for k, the number of clusters.
Observables for identity-based tachyon vacuum solutions
International Nuclear Information System (INIS)
We consider a modified KBc algebra in bosonic open string field theory expanded around identity-based scalar solutions. By use of the algebra, classical solutions on the background are constructed and observables for them, including energy densities and gauge-invariant overlaps, are calculable. These results are applied to evaluate observables analytically for both the identity-based trivial pure gauge solution and the identity-based tachyon vacuum solution
Local existence of solution to free boundary value problem for compressible Navier-Stokes equations
Liu, Jian
2015-01-01
This paper is concerned with the free boundary value problem for multi-dimensional Navier-Stokes equations with density-dependent viscosity where the flow density vanishes continuously across the free boundary. A local (in time) existence of weak solution is established, in particular, the density is positive and the solution is regular away from the free boundary.