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.
Moreau, F; Romani, R
1982-11-01
Mitochondria from avocado (Persea americana Mill, var. Fuerte and Hass) can be rapidly prepared at every stage of ripening using differential centrifugation and self-generated Percoll gradients. The procedure results in improved oxidative and phosphorylative properties, especially for mitochondria isolated from preclimacteric fruits.A gradual change in the buoyant density of avocado mitochondria takes place during ripening. Climacteric and postclimacteric avocado mitochondria have the same buoyant density as other plant mitochondria (potato, cauliflower), whereas mitochondria from preclimacteric fruit have a lower density. The transition in buoyant density occurs during the climacteric rise, and two populations of intact mitochondria (p = 1.060 and p = 1.075) can be separated at this stage. Evidence indicates that the difference in mitochondrial buoyant density between preclimacteric and postclimacteric mitochondria is likely due to interactions with soluble cytosolic components.
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.
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).
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
Energy Technology Data Exchange (ETDEWEB)
Mezzano, D.; Hwang, K.; Catalano, P.; Aster, R.H.
1981-01-01
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 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
Theoretical Analysis of A Buoyant Jet Interacting with Small Amplitude Waves
Institute of Scientific and Technical Information of China (English)
Ying-Pin LIN; Hung-Chu HSU; Yang-Yih CHEN
2009-01-01
A new theoretical solution is presented here for the dynamic characteristics of a buoyant jet due to opposing small amplitude waves.The conservation equations of mass,tangential momentum and vertical momentum are solved by the integral method which encompasses the Gaussian profiles of velocity and density.The action of waves is incorporated into the equations of motion as an external force and a new exact solution is obtained to predict the trajectory,velocity distribution and boundary thickness of the buoyant jet over an arbitrary lateral cross section.It is found that the velocity along the centerline is inversely proportional to the ratio of the momentum of the wave to the buoyant jet.The averaged boundary width varies with the fluctuation of the boundary width,the distance from the orifice and the velocity correction function.Owing to the motion d waves,the fluctuation of the boundary width is proportional to the wave steepness.
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.
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...
Hydrostatic Modeling of Buoyant Plumes
Stroman, A.; Dewar, W. K.; Wienders, N.; Deremble, B.
2014-12-01
The Deepwater Horizon oil spill in the Gulf of Mexico has led to increased interest in understanding point source convection dynamics. Most of the existing oil plume models use a Lagrangian based approach, which computes integral measures such as plume centerline trajectory and plume radius. However, this approach doesn't account for feedbacks of the buoyant plume on the ambient environment. Instead, we employ an Eulerian based approach to acquire a better understanding of the dynamics of buoyant plumes. We have performed a series of hydrostatic modeling simulations using the MITgcm. Our results show that there is a dynamical response caused by the presence of the buoyant plume, in that there is a modification of the background flow. We find that the buoyant plume becomes baroclinically unstable and sheds eddies at the neutral buoyancy layer. We also explore different scenarios to determine the effect of the buoyancy source and the temperature stratification on the evolution of buoyant plumes.
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....... and dilution can be successfully correlated by use of momentum or buoyancy length scales. In addition the centerline density deficit and velocity decay are well predicted by using an integral and a k - ∈turbulence model. The results shown here help us to understand in a better way the physical phenornenon...
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.
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
Method for solvent extraction with near-equal density solutions
Birdwell, Joseph F.; Randolph, John D.; Singh, S. Paul
2001-01-01
Disclosed is a modified centrifugal contactor for separating solutions of near equal density. The modified contactor has a pressure differential establishing means that allows the application of a pressure differential across fluid in the rotor of the contactor. The pressure differential is such that it causes the boundary between solutions of near-equal density to shift, thereby facilitating separation of the phases. Also disclosed is a method of separating solutions of near-equal density.
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)
Non-Boussinesq Integral Model for Horizontal Turbulent Buoyant Round Jets
Directory of Open Access Journals (Sweden)
J. Xiao
2009-01-01
Full Text Available Horizontal buoyant jet is a fundamental flow regime for hydrogen safety analysis in power industry. The purpose of this study is to develop a fast non-Boussinesq engineering model the horizontal buoyant round jets. Verification of this integral model is established with available experimental data and comparisons over a large range of density variations with the CFD codes GASFLOW. The model has proved to be an efficient engineering tool for predicting horizontal strongly buoyant round jets.
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)
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
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.
Institute of Scientific and Technical Information of China (English)
JIANG Ai-min; DING Hao-jiang
2005-01-01
In this paper, the specific solutions of orthotropic plane problems with body forces are derived. Then, based on the general solution in the case of distinct eigenvalues and the specific solution for density functionally graded orthotropic media, a series of beam problem, including the problems of cantilever beam with body forces depending only on z or on x coordinate and expressed by z or x polynomial is solved by the principle of superposition and the trial-and-error method.
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...
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.
Novel approaches for the prediction of density of glycol solutions
Institute of Scientific and Technical Information of China (English)
A.Bahadori; Y Hajizadeh; H.B.Vuthaluru; M.O.Tade; S.Mokhatab
2008-01-01
Two new approaches for the accurate prediction of densities of the commonly used glycol solutions in the gas processing industry are presented in the article.The frst approach is based on developing a simple-to-use polynomial corre lation for an appropriate prediction of density of glycol solutions as a function of temperature and weight percent of glycols in water,where the obtained results show very good agreement with the reported experimental data.The second approach,however.is based on the artificial neural networks(ANN)methodology,wherein the results demonstrate the ability of the in troduced method to predict reasonably accurate densities of glycols under operating conditions.Comparisons of the two novel approaches indicated that the simple-to-use correlation appears to be superior owing to its simplicity and clear numerical back ground,wherein the relevant coefficients can be retuned if new and more accurate data are available in the future.The average deviation of the new proposed polynomial correlation results from reported data iS 0.64 kg/m3 whereas the average deviation of artificial neural networks (ANN)methodology from reported data iS 1.1 kg/m3.
Spatially Modulated Instabilities for Scaling Solutions at Finite Charge Density
Cremonini, Sera
2013-01-01
We consider finite charge density geometries which interpolate between AdS2 x R2 in the infrared and AdS4 in the ultraviolet, while traversing an intermediate regime of anisotropic Lifshitz scaling and hyperscaling violation. We work with Einstein-Maxwell-dilaton models and only turn on a background electric field. The spatially modulated instabilities of the near-horizon AdS2 part of the geometry are used to argue that the scaling solutions themselves should be thought of as being unstable -- in the deep infrared -- to spatially modulated phases. We identify instability windows for the scaling exponents, which are refined further by requiring the solutions to satisfy the null energy condition. This analysis reinforces the idea that, for large classes of models, spatially modulated phases describe the ground state of hyperscaling violating scaling geometries.
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.
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....
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)
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.
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.
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)
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...
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...
A new solution to wireless sensor network density control problem
Institute of Scientific and Technical Information of China (English)
SHI Jian; JIA Yu-fu; DONG Tian-lin; LI Jiang
2006-01-01
In this paper,we proposed a scheme based on Monte Carlo algorithm to test whether or not the nodes are redundant for realizing the node density control in the sensor network.The computational complexity is only O(n).We also established the coverage collision detection and back-off mechanism applied in the wireless sensor network.The simulation results show that the system can cover all the interested area with the smallest number of nodes and a coverage void will not appear during the course of state-transition.The coverage collision detection and back-off mechanism proposed in this article can be applied when the nodes have either synchronous or asynchronous mechanism.It also provides a stable stage with the length of the time that can be adjusted.
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
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.
Mirajkar, Harish N
2016-01-01
The presence of stratified layer in atmosphere and ocean leads to buoyant vertical motions, commonly referred to as plumes. It is important to study the mixing dynamics of a plume at a local scale in order to model their evolution and growth. Such a characterization requires measuring the velocity and density of the mixing fluids simultaneously. Here, we present the results of a buoyant plume propagating in a linearly stratified medium with a density difference of 0.5%, thus yielding a buoyancy frequency of N=0.15 s^{-1}. To understand the plume behaviour, statistics such as centerline and axial velocities along varying downstream locations, turbulent kinetic energy, Reynolds stress, and buoyancy flux were measured. The centerline velocity was found to decrease with increase in height. The Reynolds stress and buoyancy flux profiles showed the presence of a unstable layer and the mixing associated within that layer.
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.
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...
The energy balance relation for weak solutions of the density-dependent Navier-Stokes equations
Leslie, T. M.; Shvydkoy, R.
2016-09-01
We consider the incompressible inhomogeneous Navier-Stokes equations with constant viscosity coefficient and density which is bounded and bounded away from zero. We show that the energy balance relation for this system holds for weak solutions if the velocity, density, and pressure belong to a range of Besov spaces of smoothness 1/3. A density-dependent version of the classical Kármán-Howarth-Monin relation is derived.
Sensitivity of the solution of the Elder problem to density, velocity and numerical perturbations
Park, Chan-Hee; Aral, Mustafa M.
2007-06-01
In this paper the Elder problem is studied with the purpose of evaluating the inherent instabilities associated with the numerical solution of this problem. Our focus is first on the question of the existence of a unique numerical solution for this problem, and second on the grid density and fluid density requirements necessary for a unique numerical solution. In particular we have investigated the instability issues associated with the numerical solution of the Elder problem from the following perspectives: (i) physical instability issues associated with density differences; (ii) sensitivity of the numerical solution to idealization irregularities; and, (iii) the importance of a precise velocity field calculation and the association of this process with the grid density levels that is necessary to solve the Elder problem accurately. In the study discussed here we have used a finite element Galerkin model we have developed for solving density-dependent flow and transport problems, which will be identified as TechFlow. In our study, the numerical results of Frolkovič and de Schepper [Frolkovič, P. and H. de Schepper, 2001. Numerical modeling of convection dominated transport coupled with density-driven flow in porous media, Adv. Water Resour., 24, 63-72.] were replicated using the grid density employed in their work. We were also successful in duplicating the same result with a less dense grid but with more computational effort based on a global velocity estimation process we have adopted. Our results indicate that the global velocity estimation approach recommended by Yeh [Yeh, G.-T., 1981. On the computation of Darcian velocity and mass balance in finite element modelling of groundwater flow, Water Resour. Res., 17(5), 1529-1534.] allows the use of less dense grids while obtaining the same accuracy that can be achieved with denser grids. We have also observed that the regularity of the elements in the discretization of the solution domain does make a difference
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.
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.
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.
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...
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-...
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.
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.
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
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.
The effect of random matter density perturbations on the MSW solution to the solar neutrino problem
Nunokawa, H; Semikoz, V B; Valle, José W F
1996-01-01
We consider the implications of solar matter density random noise upon resonant neutrino conversion. The evolution equation describing MSW-like conversion is derived in the framework of the Schr\\"odinger approach. We study quantitatively their effect upon both large and small mixing angle MSW solutions to the solar neutrino problem. This is carried out both for the active-active \
Buoyant subduction on Venus: Implications for subduction around coronae
Burt, J. D.; Head, J. W.
1993-03-01
Potentially low lithospheric densities, caused by high Venus surface and perhaps mantle temperatures, could inhibit the development of negative buoyancy-driven subduction and a global system of plate tectonics/crustal recycling on that planet. No evidence for a global plate tectonic system was found so far, however, specific features strongly resembling terrestrial subduction zones in planform and topographic cross-section were described, including trenches around large coronae and chasmata in eastern Aphrodite Terra. The cause for the absence, or an altered expression, of plate tectonics on Venus remains to be found. Slab buoyancy may play a role in this difference, with higher lithospheric temperatures and a tendency toward positive buoyancy acting to oppose the descent of slabs and favoring under thrusting instead. The effect of slab buoyancy on subduction was explored and the conditions which would lead to under thrusting versus those allowing the formation of trenches and self-perpetuating subduction were defined. Applying a finite element code to assess the effects of buoyant forces on slabs subducting into a viscous mantle, it was found that mantle flow induced by horizontal motion of the convergent lithosphere greatly influences subduction angle, while buoyancy forces produce a lesser effect. Induced mantle flow tends to decrease subduction angle to near an under thrusting position when the subducting lithosphere converges on a stationary overriding lithosphere. When the overriding lithosphere is in motion, as in the case of an expanding corona, subduction angles are expected to increase. An initial stage involved estimating the changes in slab buoyancy due to slab healing and pressurization over the course of subduction. Modeling a slab, descending at a fixed angle and heated by conduction, radioactivity, and the heat released in phase changes, slab material density changes due to changing temperature, phase, and pressure were derived.
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.
Energy Technology Data Exchange (ETDEWEB)
Ji Peijun [College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Feng Wei [College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029 (China)]. E-mail: fengwei@mail.buct.edu.cn; Tan Tianwei [College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029 (China)
2007-07-15
The density of aqueous solutions of amino acids has been modeled with the statistical associating fluid theory (SAFT) equation of state. The modeling is accomplished by extending the previously developed new method to determine the SAFT parameters for amino acids. The modeled systems include {alpha}-alanine/H{sub 2}O, {beta}-alanine/H{sub 2}O, proline/H{sub 2}O, L-asparagine/H{sub 2}O, L-glutamine/H{sub 2}O, L-histidine/H{sub 2}O, serine/H{sub 2}O, glycine/H{sub 2}O, alanine/H{sub 2}O/sucrose, DL-valine/H{sub 2}O/sucrose, arginine/H{sub 2}O/sucrose, serine/H{sub 2}O/ethylene glycol, and glycine/H{sub 2}O/ethylene glycol. The density of binary solutions of amino acids has been correlated or predicted with a high precision. And then the density of multicomponent aqueous solutions of amino acids has been modeled based on the modeling results of binary systems, and a high accuracy of density calculations has been obtained. Finally, the water activities of DL-valine/H{sub 2}O, glycine/H{sub 2}O, and proline/H{sub 2}O have been predicted without using binary interaction parameters, and good results have been obtained.
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.
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...
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.
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...
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.
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)
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
Elliptical Solutions to the Standard Cosmology Model with Realistic Values of Matter Density
Oztas, Ahmet Mecit
2015-01-01
We have examined a solution to the FRW model of the Einstein and de Sitter Universe, often termed the standard model of cosmology, using wide values for the normalized cosmological constant Omega_L and spacetime curvature Omega_k with proposed values of normalized matter density. These solutions were evaluated using a combination of the third type of elliptical equations and were found to display critical points for redshift z, between 1 and 3, when Omega_L is positive. These critical points occur at values for normalized cosmological constant higher than those currently thought important, though we find this solution interesting because the Omega_L term may increase in dominance as the Universe evolves bringing this discontinuity into importance. We also find positive Omega_L tends towards attractive at values of z which are commonly observed for distant galaxies.
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
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...
Laboratory Study of Dispersion of Buoyant Surface Plumes
DEFF Research Database (Denmark)
Petersen, Ole; Larsen, Torben
1990-01-01
-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...
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)
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.
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.
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...
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.
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.)
Kernel density estimation-based solution of the nuclear Schrödinger equation
Unke, Oliver Thorsten; Meuwly, Markus
2015-10-01
Solving the time-dependent Schrödinger equation for nuclear motion remains a challenge. Despite novel approaches based on Bohmian mechanics, the long-time stability and generalization to multiple dimensions remains an open question. In the present work a method based on an ensemble of classical particles instead of a wave function is employed to evolve the system. Quantum effects are introduced through forces derived from the quantum potential Q and the necessary derivatives are obtained from a density estimate using kernel density estimation. Application of the procedure to typical 1- and 2-dimensional problems yields good agreement with numerically exact solutions and favourable scaling with the number of particles is found.
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
is 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 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....
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.
Supergranulation as the Largest Buoyantly Driven Convective Scale of the Sun
Cossette, Jean-Francois; Rast, Mark P.
2016-09-01
The origin of solar supergranulation remains a mystery. Unlike granulation, the size of which is comparable to both the thickness of the radiative boundary layer and local scale-height in the photosphere, supergranulation does not reflect any obvious length scale of the solar convection zone. Moreover, recent observations of flows in the photosphere using Doppler imaging or correlation or feature tracking show a monotonic decrease in horizontal flow power at scales larger than supergranulation. Both local area and global spherical shell simulations of solar convection by contrast show the opposite, an increase in horizontal flow amplitudes to a low wavenumber. We examine these disparities and investigate how the solar supergranulation may arise as a consequence of nonlocal heat transport by cool diving plumes. Using three-dimensional anelastic simulations with surface driving, we show that the kinetic energy of the largest convective scales in the upper layers of a stratified domain reflects the depth of transition from strong buoyant driving to adiabatic stratification below caused by the dilution of the granular downflows. This depth is quite shallow because of the rapid increase of the mean density below the photosphere. We interpret the observed monotonic decrease in solar convective power at scales larger than supergranulation to be a consequence of this rapid transition, with the supergranular scale the largest buoyantly driven mode of convection in the Sun.
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.
Safarov, M. M.; Abdukhamidova, Z.
1995-09-01
We present the results from an experimental investigation of the density of the sunflower oil system as a function of the mass concentration of n-hexane in the ranges of temperatures T=290 520 K and pressures P=0.101 98.1 MPa. A method of hydrostatic weighing was used to measure the density of the solutions under study.
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.
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...
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.
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...
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.
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.
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.
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.
Kengne, Emmanuel; Saydé, Michel; Ben Hamouda, Fathi; Lakhssassi, Ahmed
2013-11-01
Analytical entire traveling wave solutions to the 1+1 density-dependent nonlinear reaction-diffusion equation via the extended generalized Riccati equation mapping method are presented in this paper. This equation can be regarded as an extension case of the Fisher-Kolmogoroff equation, which is used for studying insect and animal dispersal with growth dynamics. The analytical solutions are then used to investigate the effect of equation parameters on the population distribution.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Recently,the global existence of weak solutions to the compressible Navier-Stokes equations with vacuum has attracted much attention.In this paper,we study the one-dimension isentropic Navier-Stokes equations with gravitational force and fixed boundary condition when the density connects with vacuum discontinuously.We prove the global existence and the uniqueness of weak solution,requiring less regularity of the initial data.
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.
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.
Luo, Tao; Xin, Zhouping; Zeng, Huihui
2016-11-01
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 {γ} 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, which ensures the global existence of strong solutions capturing the precise physical behavior that the sound speed is {C^{{1}/{2}}}-Hölder continuous across the vacuum boundary, the large time asymptotic uniform convergence of the evolving vacuum boundary, density and velocity to those of Lane-Emden solutions with detailed convergence rates, and the detailed large time behavior of solutions near the vacuum boundary. Those uniform convergence are of fundamental importance in the study of vacuum free boundary problems which are missing in the previous results for global weak solutions. Moreover, the results obtained in this paper apply to much broader cases of viscosities than those in Fang and Zhang (Arch Ration Mech Anal 191:195-243, 2009) for the theory of weak solutions when the adiabatic exponent {γ} lies in the most physically relevant range. Finally, this paper extends the previous local-in-time theory for strong solutions to a global-in-time one.
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.
Rossi, A
1996-01-01
We present a generalization of the resonant neutrino conversion in matter, including a random component in the matter density profile. The study is focused on the effect of such matter perturbations upon both large and small mixing angle MSW solutions to the solar neutrino problem. This is carried out both for the active-active \
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...
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...
Yang, R.; Song, A.; Li, X. D.; Lu, Y.; Yan, R.; Xu, B.; Li, X.
2014-10-01
A 3D reconstruction solution to ultrasound Joule heat density tomography based on acousto-electric effect by deconvolution is proposed for noninvasive imaging of biological tissue. Compared with ultrasound current source density imaging, ultrasound Joule heat density tomography doesn't require any priori knowledge of conductivity distribution and lead fields, so it can gain better imaging result, more adaptive to environment and with wider application scope. For a general 3D volume conductor with broadly distributed current density field, in the AE equation the ultrasound pressure can't simply be separated from the 3D integration, so it is not a common modulation and basebanding (heterodyning) method is no longer suitable to separate Joule heat density from the AE signals. In the proposed method the measurement signal is viewed as the output of Joule heat density convolving with ultrasound wave. As a result, the internal 3D Joule heat density can be reconstructed by means of Wiener deconvolution. A series of computer simulations set for breast cancer imaging applications, with consideration of ultrasound beam diameter, noise level, conductivity contrast, position dependency and size of simulated tumors, have been conducted to evaluate the feasibility and performance of the proposed reconstruction method. The computer simulation results demonstrate that high spatial resolution 3D ultrasound Joule heat density imaging is feasible using the proposed method, and it has potential applications to breast cancer detection and imaging of other organs.
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
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
The effects of possibly buoyant flat slab segments on Nazca and South American plate motions
Lithgow-Bertelloni, C. R.; Shea, R.; Crameri, F.
2014-12-01
Flat slabs are ubiquitous today and in Earth's past, present in at least 10% of present-day subduction zones. The Nazca slab is a classic example with large dip variations along strike, including two prominent flat segments in Peru and Argentina that coincide with the subduction of aseismic ridges. The origin of flat segments remain enigmatic though much work has examined the consequences for upper plate deformation and continued subduction. In the case of the Argentinian flat segment, detailed seismic imaging has shown significantly increased crustal thickness in the flat part of the slab. Our present understanding of oceanic crust formation suggests that incrased crustal thickness forms in response to larger degrees of partial melt, which in turn decrease the water content of the formed crust. The residuum from this process is depleted. The resulting combined lithospheric column is buoyant with respect to the underlying mantle, and likely cold from its contact with the overlying plate and unlikely to undergo the basalt-eclogite transition due to kinetic hindrances. This has consequences for mantle flow and the shear stresses it exerts at the base of the lithosphere and hence to plate motions. Interestingly, the motion of the Nazca-South America pair is difficult to reproduce even in the most sophisticated models (Stadler et al. 2010) without invoking special coupling, rheology or forces. We examine the effects of the subduction of neutral and buoyant flat segments on mantle flow and plate motions, globally and locally for Nazca and South America. We construct high-resolution models of the morphology and density structure of the Nazca slab and embed them in an existing global slab model. We compute the global viscous flow induced and predict plate motions consistent with the density heterogeneity and plate geometry. As an end member we also examine a Nazca slab that dips uniformly with a 30 degree dip. We find, perhaps unsurprisingly, that the most important
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.
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.
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
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
Complex Probability Distributions A Solution for the Long-Standing Problem of QCD at Finite Density
Azcoiti, V
1996-01-01
We show how the prescription of taking the absolute value of the fermion determinant in the integration measure of QCD at finite density, forgetting its phase, reproduces the correct thermodynamical limit. This prescription, which applies also to other gauge theories with non-positive-definite integration measure, also has the advantage of killing finite size effects due to extremely small mean values of the cosine of the phase of the fermion determinant. We also give an explanation for the pathological behaviour of quenched QCD at finite density.
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.
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.
Boiteux's solution to the shifting-peak problem and the equilibrium price density in continuous time
Horsley, A.; Wrobel, A.J.
2002-01-01
Bewley's condition on production sets, imposed to ensure the existence of an equilibrium price density when L∞ is the commodity space, is weakened to allow applications to continuous-time problems, and especially to peak-load pricing when the users' utility and production functions are Mackey contin
González-López, Jorge; Ruiz-Hernández, Sergio E.; Fernández-González, Ángeles; Jiménez, Amalia; de Leeuw, Nora H.; Grau-Crespo, Ricardo
2015-04-01
The incorporation of cobalt in mixed metal carbonates is a possible route to the immobilization of this toxic element in the environment. However, the thermodynamics of (Ca,Co)CO3 solid solutions are still unclear due to conflicting data from experiment and from the observation of natural ocurrences. Atomistic computer simulations, which allow the evaluation of thermodynamic properties without the interference of unknown kinetic factors, have been increasingly used in recent years for the investigation of the thermodynamics of mixing and impurity incorporation in carbonate. We report here the results of a computer simulation study of the mixing of calcite (CaCO3) and spherocobaltite (CoCO3), using density functional theory calculations. Our simulations suggest that previously proposed thermodynamic models, based only on observed compositions, significantly overestimate the solubility between the two solids and therefore underestimate the extension of the miscibility gap under ambient conditions. The enthalpy of mixing of the disordered solid solution is strongly positive and moderately asymmetric: calcium incorporation in spherocobaltite is more endothermic than cobalt incorporation in calcite. Ordering of the impurities in (0001) layers is energetically favourable with respect to the disordered solid solution at low temperatures and intermediate compositions, but the ordered phase is still unstable to demixing. The solvus and spinodal lines in the phase diagram using a sub-regular solution model has been also calculated, and conclude that many Ca1-xCoxCO3 mineral solid solutions (with observed compositions of up to x=0.027, and above x=0.93) are metastable with respect to phase separation. The strong non-ideality of this solid solution has an important effect on the solid solution / aqueous solution thermodynamic partitioning: the equilibrium level of substitutional impurities in the endmember solids is always low, regardless of the composition of the aqueous
Energy Technology Data Exchange (ETDEWEB)
Griffiths, R.; Reichel, N. [Schlumberger, Sungai Buloh (Malaysia)
2013-08-01
For many years the industry has been searching for a way to eliminate the logistical difficulties and risk associated with deployment of radioisotopes for formation evaluation. The traditional gamma-gamma density (GGD) measurement uses the scattering of 662-keV gamma rays from a 137Cs radioisotopic source, with a 30.17-year half-life, to determine formation density. The traditional neutron measurement uses an Am-Be source emitting neutrons with an energy around 4 MeV, with a half-life of 432 years. Both these radioisotopic sources pose health, security, and environmental risks. Pulsed-neutron generators have been used in the industry for several decades in wireline tools and more recently in logging-while-drilling tools. These generators produce 14-MeV neutrons, many of which interact with the nuclei in the formation. Elastic collisions allow a neutron porosity measurement to be derived, which has been available to the industry since 2005. Inelastic interactions are typically followed by the emission of a variety of high-energy gamma rays. Similar to the case of the GGD measurement, the transport and attenuation of these gamma rays is a strong function of the formation density. However, the gamma-ray source is now distributed over a volume within the formation, where gamma rays have been induced by neutron interactions and the source can no longer be considered to be a point as in the case of a radioisotopic source. In addition, the extent of the induced source region depends on the transport of the fast neutrons from the source to the point of gamma-ray production. Even though the physics is more complex, it is possible to measure the formation density if the fast neutron transport is taken into account when deriving the density answer. This paper briefly reviews the physics underlying the sourceless neutron porosity and recently introduced neutron-gamma density (SNGD) measurement, demonstrates how they can be used in traditional workflows and illustrates their
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.
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.
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.
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)
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.
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.
The effect of particle properties on the depth profile of buoyant plastics in the ocean
Kooi, Merel; Reisser, Julia; Slat, Boyan; Ferrari, Francesco F.; Schmid, Moritz S.; Cunsolo, Serena; Brambini, Roberto; Noble, Kimberly; Sirks, Lys-Anne; Linders, Theo E. W.; Schoeneich-Argent, Rosanna I.; Koelmans, Albert A.
2016-01-01
Most studies on buoyant microplastics in the marine environment rely on sea surface sampling. Consequently, microplastic amounts can be underestimated, as turbulence leads to vertical mixing. Models that correct for vertical mixing are based on limited data. In this study we report measurements of the depth profile of buoyant microplastics in the North Atlantic subtropical gyre, from 0 to 5 m depth. Microplastics were separated into size classes (0.5–1.5 and 1.5–5.0 mm) and types (‘fragments’ and ‘lines’), and associated with a sea state. Microplastic concentrations decreased exponentially with depth, with both sea state and particle properties affecting the steepness of the decrease. Concentrations approached zero within 5 m depth, indicating that most buoyant microplastics are present on or near the surface. Plastic rise velocities were also measured, and were found to differ significantly for different sizes and shapes. Our results suggest that (1) surface samplers such as manta trawls underestimate total buoyant microplastic amounts by a factor of 1.04–30.0 and (2) estimations of depth-integrated buoyant plastic concentrations should be done across different particle sizes and types. Our findings can assist with improving buoyant ocean plastic vertical mixing models, mass balance exercises, impact assessments and mitigation strategies. PMID:27721460
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.
The study on density change of carbon dioxide seawater solution at high pressure and low temperature
International Nuclear Information System (INIS)
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
Institute of Scientific and Technical Information of China (English)
LIU Dan; WEI Guo; SUN Jin-wei; LIU Xin
2009-01-01
In the osmotic dehydration process of food, on-line estimation of concentrations of two components in ternary solution with NaCI and sucrose was performed based on multi-functional sensing technique.Moving Least Squares were adopted in approximation procedure to estimate the viscosity of such interested ternary solu-tion with the given data set.As a result, in one mode of using total experimental data as calibration data andvalidation data, the relative deviations of estimated viscosities are less than ～ 1.24%.In the other mode, by taking total experimental data except the ones for estimation as calibration data, the relative deviations are less than±3.47%.In the same way, the density of ternary solution can be also estimated with deviations less than ± 0.11% and ± 0.30% respectively in these two models.The satisfactory and accurate results show the ex-traordinary efficiency of Moving Least Squares behaved in signal approximation for multi-functional sensors.
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.
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...
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
Effect of Technology Enhanced Conceptual Change Texts on Students' Understanding of Buoyant Force
Ozkan, Gulbin; Selcuk, Gamze Sezgin
2015-01-01
In this study, the effect of technology enhanced conceptual change texts on elementary school students' understanding of buoyant force was investigated. The conceptual change texts (written forms) used in this study are proven for effectiveness and are enriched by using technology support in this study. These texts were tried out on two groups. A…
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)
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)
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
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...
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
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
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...
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...
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...
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.
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...
Response of buoyant plumes to transient discharges investigated using an adaptive solver
O'Callaghan, J.; Rickard, G.; Popinet, S.; Stevens, C.
2010-11-01
The behavior of buoyant plumes driven by variable momentum inputs were examined using an adaptive Navier-Stokes solver (Gerris). Boundary conditions were representative of an idealized stratified, coastal environment. Salinity ranged from 5 to 30 in the top 5 m of the water column to replicate the strong vertical gradients experienced in fjord environments. Two-dimensional simulations examined the response of the buoyant plume driven by zero, steady, and variable momentum fluxes. The behavior was quantified in terms of the characteristic features of a buoyant plume, the thickness of the nose (or head of gravity current), and the trailing tail. Both the nose and tail of the plume were substantially thicker for the variable momentum run, whereas elongation and thinning of the plume was evident for the steady and zero momentum inputs. Furthermore, an order of magnitude difference in available potential energy was found for the variable momentum run. Validation of the Boussinesq approximation initially utilized the classic lock-exchange experiment with excellent agreement to previous numerical and theoretical experiments. Frontal speeds of the gravity current converged toward the theoretical value of Benjamin (1968). The adaptive mesh permitted lock-exchange simulations at Reynolds number (Re) of ˜10,500 and are some of the highest Re runs to date. Moreover, improved computational efficiency was achieved using the adaptive solver with simulations completed in 20% of the time they took on a static, high-resolution grid.
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.
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.
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Vazquez, G.; Chenlo, F.; Pereira, G. [Univ. of Santiago de Compostela (Spain). Dept. of Chemical Engineering
1997-06-01
Absorption of CO{sub 2} in a wetted-wall column by 0.5 M Na{sub 2}CO{sub 3}/0.5 M NaHCO{sub 3} buffer with and without various concentrations of saccharose, fructose, glucose, formaldehyde, glycerin, methanol, or ethanol was measured under conditions in which the reaction of CO{sub 2} was of pseudo-first-order. For the purposes of comparison, experiments were also carried out with arsenite in both buffer and pure water. For all of these solutes, the absorption enhancement factor increased with solute concentration. Rate constants k{sub c} for the overall reaction were obtained by fitting Danckwerts` expression for absorption to the experimental data, and correlation of k{sub c} with solute concentration then afforded rate constants k{sub cat} for the catalyzed reactions. For each solute, an empirical correlation was found between the absorption enhancement factor and Hatta numbers calculated from the rate constant for the uncatalyzed reaction and from k = k{sub cat}[cat]. The notion that the enhancement of absorption by acid-base reaction is facilitated by dipole-dipole interaction between the solutes and CO{sub 2} is supported by an empirical correlation relating k{sub cat} to the degree of dissociation of the solute and the density of OH groups in the solute molecule.
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
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.
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
Directory of Open Access Journals (Sweden)
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.
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.
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.
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.
Characterization of Buoyant Fluorescent Particles for Field Observations of Water Flows
Directory of Open Access Journals (Sweden)
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.
Experimental Study on Liquid Free Surface in Buoyant-Thermocapillary Convection
Institute of Scientific and Technical Information of China (English)
DUAN Li; KANG Qi; HU Wen-Rui
2008-01-01
@@ We investigate the surface deformations of buoyant-thermocapillary convection in a rectangular cavity due to gravity and temperature gradient between the two sidewalls. The cavity is 52mm×42 mm in horizontal cross section, the thickness of liquid layer h is changed from 2.5mm to 6.5 mm. Surface deformations of h = 3.5 mm and 6.0mm are discussed and compared. Temperature difference is increased gradually, and the flow in the liquid layer will change from stable convection to unstable convection. Two kinds of optical diagnostic system with image processor are developed for study of the kinetics of buoyant-thermocapillaxy convection, they give out the information of liquid free surface. The quantitative results are calculated by Fourier transform and correlation analysis, respectively. With the increasing temperature gradient, surface deformations calculated are more declining. It is interesting phenomenon that the inclining directions of the convections in thin and thick liquid layers are different. For a thin layer, the convection is mainly controlled by thermocapillary effect. However,for a thick layer, the convection is mainly controlled by buoyancy effect. The surface deformation theoretically analysed is consistent with our experimental results. The present experiment proves that surface deformation is related to temperature gradient and thickness of the liquid layer. In other words, surface deformation lies on capillary convection and buoyancy convection.
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.
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.
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...
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...
Zhao, Zuofeng; Angell, C Austen
2016-02-12
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
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
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.
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...
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 ...
Institute of Scientific and Technical Information of China (English)
WU Teng-hu; SHAO Xue-ming; YU Zhao-sheng
2011-01-01
In this article, we employ a fully-resolved numerical simulation method (the fictitious domain method) to investigate the effects of large neutrally-buoyant particles on the turbulent flow in a pipe at low Reynolds number and non-dilute regimes. The tube Reynolds number is fixed to be 4 900, the particle-pipe diameter ratio is 0.1, and the particle volume fraction ranges from 0.33％ to 10％. Our results indicate that the presence of large particles decreases the maximum root-of-mean-square (rms) of the streamwise velocity fluctuation near the wall by weakening the intensity of large-scale streamwise vortices, although in the region very close to the wall the particles increase the rms of streamwise velocity fluctuation. On the other hand, the particles induce small-scale vortices in the near-wall region, resulting in the enhancement of the rms of radial and circumferential velocity fluctuations there.
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.
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
International Nuclear Information System (INIS)
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.
Rosen, Mordecai D.
2016-10-01
The high energy density (HED) and inertial confinement fusion (ICF) physics community relies on increasingly sophisticated high power laser driven experiments to advance the field. We review early work in the design and analysis of such experiments, and discuss the problems encountered. By finding solutions to those problems we put the field on firmer ground, allowing the community to develop it to the exciting stage it is in today. Specific examples include: drive and preheat in complex hohlraum geometries with the complicating effects of sample motion; and issues in the successful design of laboratory soft x-ray lasers and in the invention of methods to reduce the required optical laser driver energy by several orders of magnitude.
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.
地质封存中CO2水溶液密度研究进展%Research Progress on Density of CO2 Aqueous Solution
Institute of Scientific and Technical Information of China (English)
常飞; 宋永臣; 张毅
2011-01-01
Sequestration of CO2 into underground saline aquifer is considered as a viable option to reduce CO2 and mitigate climate change. The density of CO2 salt solution is a key parameter for CO2 saline aquifer storage which determines the diffusion and migration of CO2 in reservoir and then affects the storage safety. Research progress of the density of CO2 aqueous solution from an experimental and a simulation perspective were summarized. It was found that although the operating range of existing density data nearly covered the scope of storage conditions,they cannot meet the needs of sequestration in terms of quantity and accuracy. Most of the existing model are empirical formula,which have a narrow applicable range and low prediction accuracy. Theoretical model is in the research stage, in which the theoretical model based on SAFT Equation of State is the research focus at present. It is necessary to investigate the relationship between density of CO2 aqueous solution and factors such as temperature,pressure,CO2 concentration and salinity under sequestration conditions systematically and build a theoretical model with wide applicable range and high prediction accuracy in order to provide necessary support for CO2 saline aquifer storage.%CO2地下盐水层封存是减排CO2、缓解气候变化的可行方案之一.CO2盐水溶液密度影响CO2在储层中的扩散和运移,从而影响封存的安全性;因此,对于CO2盐水层封存十分重要.文章从实验测量和数学模型两个角度总结了对CO2水溶液密度的研究进展,认为现有实验数据的工况范围能够覆盖封存条件范围,但在数量和准确性方面都无法满足CO2地下盐水层封存需要.现有溶液密度模型大多数是经验公式,适用范围较窄、预测精度不高.理论模型正处于研究阶段,基于SAFT状态方程的理论模型是目前的研究热点.因此,需要系统研究封存条件下的CO2水溶液密度与温度、压力、CO2质
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
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 and analysis of confined turbulent buoyant jet with variable source
Institute of Scientific and Technical Information of China (English)
EL-AMIN Mohamed F; AL-GHAMDI Abdulmajeed; SALAMA Amgad; SUN Shuyu
2015-01-01
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-ε turbulence model is used to model the turbulent flow. Comparisons show good agreements between simulated and measured results. The average devia- tion of the simulated temperature by realizablek-ε 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 varia- tion 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 experime- nts 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.
Isolation of Low Abundance Proteins and Cells Using Buoyant Glass Microbubble Chromatography
Directory of Open Access Journals (Sweden)
Steingrimur Stefansson
2013-01-01
Full Text Available Conventional protein affinity chromatography relies on highly porous resins that have large surface areas. These properties are ideal for fast flow separation of proteins from biological samples with maximum yields, but these properties can also lead to increased nonspecific protein binding. In certain applications where the purity of an isolated protein is more important than the yield, using a glass solid phase could be advantageous as glass is nonporous and hydrophilic and has a low surface area and low nonspecific protein binding. As a proof of principle, we used protein A-conjugated hollow glass microbubbles to isolate fluorescently labeled neurofilament heavy chain spiked into serum and compared them to protein A Sepharose and protein A magnetic beads (Dynabeads using an anti-neurofilament protein antibody. As expected, a greater volume of glass bubbles was required to match the binding capacity of the magnetic beads and Sepharose resins. On the other hand, nonspecific protein binding to glass bubbles was greatly reduced compared to the other resins. Additionally, since the glass bubbles are buoyant and transparent, they are well suited for isolating cells from biological samples and staining them in situ.
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.
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.
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...
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.
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.
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
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.
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/\
Kim, Sungho; Giddens, Don P
2015-04-01
The accumulation of low density lipoprotein (LDL) in the arterial intima is a critical step in the initiation and progression of atheromatous lesions. In this study we examine subject-specific LDL transport into the intima of carotid bifurcations in three human subjects using a three-pore model for LDL mass transfer. Subject-specific carotid artery computational models were derived using magnetic resonance imaging (MRI) to obtain the geometry and phase-contract MRI (PC-MRI) to acquire pulsatile inflow and outflow boundary conditions for each subject. The subjects were selected to represent a wide range of anatomical configurations and different stages of atherosclerotic development from mild to moderate intimal thickening. A fluid-solid interaction (FSI) model was implemented in the computational fluid dynamics (CFD) approach in order to consider the effects of a compliant vessel on wall shear stress (WSS). The WSS-dependent response of the endothelium to LDL mass transfer was modeled by multiple pathways to include the contributions of leaky junctions, normal junctions, and transcytosis to LDL solute and plasma volume flux from the lumen into the intima. Time averaged WSS (TAWSS) over the cardiac cycle was computed to represent the spatial WSS distribution, and wall thickness (WTH) was determined from black blood MRI (BBMRI) so as to visualize intimal thickening patterns in the bifurcations. The regions which are exposed to low TAWSS correspond to elevated WTH and higher mass and volume flux via the leaky junctions. In all subjects, the maximum LDL solute flux was observed to be immediately downstream of the stenosis, supporting observations that existing atherosclerotic lesions tend to progress in the downstream direction of the stenosis.
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.
Brunner, K.; Kukulka, T.; Proskurowski, G.; Law, K. L.
2015-11-01
This paper is the second of a two-part series that investigates passive buoyant tracers in the ocean surface boundary layer (OSBL). The first part examines the influence of equilibrium wind-waves on vertical tracer distributions, based on large eddy simulations (LESs) of the wave-averaged Navier-Stokes equation. Motivated by observations of buoyant microplastic marine debris (MPMD), this study applies the LES model and the parametric one-dimensional column model from part one to examine the vertical distributions of MPMD. MPMD is widely distributed in vast regions of the subtropical gyres and has emerged as a major open ocean pollutant whose distribution is subject to upper ocean turbulence. The models capture shear-driven turbulence, Langmuir turbulence (LT), and enhanced turbulent kinetic energy input due to breaking waves (BWs). Model results are only consistent with observations of MPMD profiles and the relationship between surface concentrations and wind speed if LT effects are included. Neither BW nor shear-driven turbulence is capable of deeply submerging MPMD, suggesting that the observed vertical MPMD distributions are a characteristic signature of wave-driven LT. Thus, this study demonstrates that LT substantially increases turbulent transport in the OSBL, resulting in deep submergence of buoyant tracers. The parametric model is applied to 11 years of observations in the North Atlantic and North Pacific subtropical gyres to show that surface measurements substantially underestimate MPMD concentrations by a factor of 3-13.
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...
Ruban, V P
2016-01-01
The dynamics of a vortex filament in a trapped Bose-Einstein condensate is considered when the equilibrium density of the condensate, in rotating with angular velocity ${\\bf\\Omega}$ coordinate system, is Gaussian with a quadratic form ${\\bf r}\\cdot\\hat D{\\bf r}$. It is shown that equation of motion of the filament in the local induction approximation admits a class of exact solutions in the form of a straight moving vortex, ${\\bf R}(\\beta,t)=\\beta {\\bf M}(t) +{\\bf N}(t)$, where $\\beta$ is a longitudinal parameter, and $t$ is the time. The vortex is in touch with an ellipsoid, as it follows from the conservation laws ${\\bf N}\\cdot \\hat D {\\bf N}=C_1$ and ${\\bf M}\\cdot \\hat D {\\bf N}=C_0=0$. Equation of motion for the tangent vector ${\\bf M}(t)$ turns out to be closed, and it has the integrals ${\\bf M}\\cdot \\hat D {\\bf M}=C_2$, $(|{\\bf M}| -{\\bf M}\\cdot\\hat G{\\bf \\Omega})=C$, where the matrix $\\hat G=2(\\hat I \\mbox{Tr\\,} \\hat D -\\hat D)^{-1}$. Intersection of the corresponding level surfaces determines trajecto...
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
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.
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 (< 0.2 μm) fraction and Cu, Co, Zn, Cd, and Pb are mainly in the unfiltered fraction. At TAG and Snakepit, unfiltered copper is correlated with unfiltered cobalt, and unfiltered 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.
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
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
Peruzzo, Paolo; Pietro Viero, Daniele; Defina, Andrea
2016-11-01
The seeds of many aquatic plants, as well as many propagulae and larvae, are buoyant and transported at the water surface. These particles are therefore subject to surface tension, which may enhance their capture by emergent vegetation through capillary attraction. In this work, we develop a semi-empirical model that predicts the probability that a floating particle is retained by plant stems and branches piercing the water surface, due to capillarity, against the drag force exerted by the flowing water. Specific laboratory experiments are also performed to calibrate and validate the model.
Design and Environment, 1972
1972-01-01
Three-part report pinpointing problems and uncovering solutions for the dual concepts of density (ratio of people to space) and crowding (psychological response to density). Section one, A Primer on Crowding,'' reviews new psychological and social findings; section two, Density in the Suburbs,'' shows conflict between status quo and increased…
MacGregor, K B
2003-01-01
We present results from an investigation of the dynamical behavior of buoyant magnetic flux rings in the radiative interior of a uniformly rotating early-type star. Our physical model describes a thin, axisymmetric, toroidal flux tube that is released from the outer boundary of the convective core, and is acted upon by buoyant, centrifugal, Coriolis, magnetic tension, and aerodynamic drag forces. We find that rings emitted in the equatorial plane can attain a stationary equilibrium state that is stable with respect to small displacements in radius, but is unstable when perturbed in the meridional direction. Rings emitted at other latitudes travel toward the surface along trajectories that largely parallel the rotation axis of the star. Over much of the ascent, the instantaneous rise speed is determined by the rate of heating by the absorption of radiation that diffuses into the tube from the external medium. Since the time scale for this heating varies like the square of the tube cross-sectional radius, for t...
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
Numerical simulation of a viscous vortex ring interaction with a density interface
Marcus, D. L.; Bell, J. B.
1990-10-01
When a vortex-dominated flow interacts with a sharp density interface, the dynamics are characterized by the interaction of baroclinically generated vorticity with the already existing vorticity field. This can be seen in many natural and technology settings; examples are the interaction of a ship or submarine wake with a thermocline, the collision of a buoyant thermal with a temperature inversion, and the interaction of a vortex flow with a flame front. This problem also serves as a generic model for turbulent mixing and entrainment processes across sharp density interfaces. The interaction between vortices and a free surface, with corresponds to the case where the density jump is very large, has been studied fairly extensively, both experimentally and computationally. By comparison, the literature for the more general case of vortex pairs and rings interacting with sharp density interfaces is relatively sparse. Experiments and numerical studies have been performed, but the numerical simulations were confined primarily to vortex pairs, restricted to the inviscid case, and the effect of density variation modeled under the Boussinesq approximation. The experiments were also confined to the Boussinesq regime. The motion of a vortex ring was studied in a sharply stratified, viscous fluid via a numerical solution of the full Navier-Stokes equations with finite-amplitude density variation. Both Boussinesq and non-Boussinesq flow regimes will be studied, the effect of viscosity on the interaction will be examined, and three-dimensional aspects of the motion will be addressed, such as Widnall instability of the vortex ring and vortex reconnection at the interface.
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
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.
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
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...... Isles. Published by Elsevier Science Ltd. All rights reserved...
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)
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
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.
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)
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)
Yu, Haiqing; Lu, Joann J.; Rao, Wei
2016-01-01
Density gradient centrifugation is widely utilized for various high purity sample preparations, and density gradient ultracentrifugation (DGU) is often used for more resolution-demanding purification of organelles and protein complexes. Accurately locating different isopycnic layers and precisely extracting solutions from these layers play a critical role in achieving high-resolution DGU separations. In this technique note, we develop a DGU procedure by freezing the solution rapidly (but gently) after centrifugation to fix the resolved layers and by slicing the frozen solution to fractionate the sample. Because the thickness of each slice can be controlled to be as thin as 10 micrometers, we retain virtually all the resolution produced by DGU. To demonstrate the effectiveness of this method, we fractionate complex V from HeLa mitochondria using a conventional technique and this freezing-slicing (F-S) method. The comparison indicates that our F-S method can reduce complex V layer thicknesses by ~40%. After fractionation, we analyze complex V proteins directly on a matrix assisted laser desorption/ionization, time-of-flight mass spectrometer. Twelve out of fifteen subunits of complex V are positively identified. Our method provides a practical protocol to identify proteins from complexes, which is useful to investigate biomolecular complexes and pathways in various conditions and cell types.
Yu, Haiqing; Lu, Joann J; Rao, Wei; Liu, Shaorong
2016-01-01
Density gradient centrifugation is widely utilized for various high purity sample preparations, and density gradient ultracentrifugation (DGU) is often used for more resolution-demanding purification of organelles and protein complexes. Accurately locating different isopycnic layers and precisely extracting solutions from these layers play a critical role in achieving high-resolution DGU separations. In this technique note, we develop a DGU procedure by freezing the solution rapidly (but gently) after centrifugation to fix the resolved layers and by slicing the frozen solution to fractionate the sample. Because the thickness of each slice can be controlled to be as thin as 10 micrometers, we retain virtually all the resolution produced by DGU. To demonstrate the effectiveness of this method, we fractionate complex V from HeLa mitochondria using a conventional technique and this freezing-slicing (F-S) method. The comparison indicates that our F-S method can reduce complex V layer thicknesses by ~40%. After fractionation, we analyze complex V proteins directly on a matrix assisted laser desorption/ionization, time-of-flight mass spectrometer. Twelve out of fifteen subunits of complex V are positively identified. Our method provides a practical protocol to identify proteins from complexes, which is useful to investigate biomolecular complexes and pathways in various conditions and cell types. PMID:27668122
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.
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.
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.
DEFF Research Database (Denmark)
Frimand, Kenneth; Bohr, Henrik; Jalkanen, Karl J.;
2000-01-01
A detailed comparative study of structures, vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra has been carried out for the zwitterionic structure of the amino acid L-alanine. Theoretically determined structures necessary for deriving VA and VCD spectra were calculated...... with three different solvation approaches: the zwitterion surrounded by explicit water molecules only, the zwitterion embedded in a self-consistent reaction field (Onsager model) and the zwitterion plus the explicit water molecules embedded in a self-consistent reaction field. The structures were optimized...... at the density functional theory level using the B3LYP functional with the 6-31G* basis set. The Hessians and atomic polar tensors and atomic axial tensors were all calculated at the B3LYP/6-31G* level of theory. An important result is the method of treating solvent effects by both adding explicit water...
Cui, Wei; Lansac, Yves; Lee, Hochun; Hong, Seung-Tae; Jang, Yun Hee
2016-09-14
Complex formation between lithium (Li(+)) ions and electrolyte molecules would affect the ionic conductivity through the electrolyte in lithium-ion batteries (LIBs). We hence revisit the solvation number of Li(+) in the most commonly used ethylene carbonate (EC) electrolyte. The solvation number n of Li(+)(EC)n in the first solvation shell of Li(+) is estimated on the basis of the free energy calculated by the density functional theory combined with a hybrid solvation model where the explicit solvation shell of Li(+) is immersed in a free volume of an implicit bulk solvent. This new hybrid solvation (implicit and explicit) model predicts the most probable solvation number (n = 4) and solvation free energy (-91.3 kcal mol(-1)) of Li(+) in a good agreement with those predicted by calculations employing simpler solvation models (either implicit or explicit). The desolvation (n = 2) of Li(0)(EC)n upon reduction near anodes is also well described with this new hybrid model.
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.
Cardoso, Silvana S S
2016-01-01
High speeds have been measured at seep and mud-volcano sites expelling methane-rich fluids from the seabed. Thermal or solute-driven convection alone cannot explain such high velocities in low-permeability sediments. Here, we demonstrate that in addition to buoyancy, osmotic effects generated by the adsorption of methane onto the sediments can create large overpressures, capable of recirculating seawater from the seafloor to depth in the sediment layer, then expelling it upwards at rates of up to a few hundreds of metres per year. In the presence of global warming, such deep recirculation of seawater can accelerate the melting of methane hydrates at depth from timescales of millennia to just decades, and can drastically increase the rate of release of methane into the hydrosphere and perhaps the atmosphere.
Zhang, H.; Schwartz, F.W.; Wood, W.W.; Garabedian, S.P.; LeBlanc, D.R.
1998-01-01
A multispecies numerical code was developed to simulate flow and mass transport with kinetic adsorption in variable-density flow systems. The two-dimensional code simulated the transport of bromide (Br-), a nonreactive tracer, and lithium (Li+), a reactive tracer, in a large-scale tracer test performed in a sand-and-gravel aquifer at Cape Cod, Massachusetts. A two-fraction kinetic adsorption model was implemented to simulate the interaction of Li+ with the aquifer solids. Initial estimates for some of the transport parameters were obtained from a nonlinear least squares curve-fitting procedure, where the breakthrough curves from column experiments were matched with one-dimensional theoretical models. The numerical code successfully simulated the basic characteristics of the two plumes in the tracer test. At early times the centers of mass of Br- and Li+ sank because the two plumes were closely coupled to the density-driven velocity field. At later times the rate of downward movement in the Br- plume due to gravity slowed significantly because of dilution by dispersion. The downward movement of the Li+ plume was negligible because the two plumes moved in locally different velocity regimes, where Li+ transport was retarded relative to Br-. The maximum extent of downward transport of the Li+ plume was less than that of the Br- plume. This study also found that at early times the downward movement of a plume created by a three-dimensional source could he much more extensive than the case with a two-dimensional source having the same cross-sectional area. The observed shape of the Br- plume at Cape Cod was simulated by adding two layers with different hydraulic conductivities at shallow depth across the region. The large dispersion and asymmetrical shape of the Li+ plume were simulated by including kinetic adsorption-desorption reactions.
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.
Rixman, Monica; Macias, Celia; Dean, Delphine; Ortiz, Christine
2003-03-01
The first step in the biological rejection response to an implanted blood-contacting biomaterial is the non-covalent adsorption of proteins onto the surface, which triggers a cascade reaction ultimately resulting in thrombus formation. Using the technique of high resolution force spectroscopy, we have quantified the nonspecific intermolecular forces between fatty acid-complexed human serum albumin (HSA) covalently attached to a cantilever probe tip and individual end-grafted poly(ethylene oxide) mushrooms. In order to help elucidate the molecular origins of the constituent forces (e.g. steric, electrostatic, van der Waals), experiments were performed varying both the solution environmental conditions (e.g. ionic strength, removal of the bound fatty acids, and the addition of the antihydrophobic agent isopropanol), and the probe deflection rate.
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.
Cui, Wei; Lansac, Yves; Lee, Hochun; Hong, Seung-Tae; Jang, Yun Hee
2016-09-14
Complex formation between lithium (Li(+)) ions and electrolyte molecules would affect the ionic conductivity through the electrolyte in lithium-ion batteries (LIBs). We hence revisit the solvation number of Li(+) in the most commonly used ethylene carbonate (EC) electrolyte. The solvation number n of Li(+)(EC)n in the first solvation shell of Li(+) is estimated on the basis of the free energy calculated by the density functional theory combined with a hybrid solvation model where the explicit solvation shell of Li(+) is immersed in a free volume of an implicit bulk solvent. This new hybrid solvation (implicit and explicit) model predicts the most probable solvation number (n = 4) and solvation free energy (-91.3 kcal mol(-1)) of Li(+) in a good agreement with those predicted by calculations employing simpler solvation models (either implicit or explicit). The desolvation (n = 2) of Li(0)(EC)n upon reduction near anodes is also well described with this new hybrid model. PMID:27506245
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...
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 Rea. As Rea→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 Rea 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 λc≈0.137 below which tumbling is stable (as well as log rolling). The simulation results show a bifurcation line in the λ -Rea plane that reaches λ ≈0.1275 at the smallest shear Reynolds number (Rea=1 ) at which we could simulate with the lattice Boltzmann code, in qualitative agreement with the analytical results.
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 ...
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...
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.
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.
Taisne, B.; Tait, S.
2009-06-01
When a volume of magma is released from a source at depth, one key question is whether or not this will culminate in an eruption or in the emplacement of a shallow intrusion. We address some of the physics behind this question by describing and interpreting laboratory experiments on the propagation of cracks filled with fixed volumes of buoyant liquid in a brittle, elastic host. Experiments were isothermal, and the liquid was incompressible. The cracks propagated vertically because of liquid buoyancy but were then found to come to a halt at a configuration of static mechanical equilibrium, a result that is inconsistent with the prediction of the theory of linear elastic fracture mechanics in two dimensions. We interpret this result as due to a three-dimensional effect. At the curved crack front, horizontal cracking is necessary in order for vertical propagation to take place. As the crack elongates and thins, the former becomes progressively harder and, in the end, impossible to fracture. We present a scaling law for the final length and breadth of cracks as a function of a governing dimensionless parameter, constructed from the liquid volume, the buoyancy, and host fracture toughness. An important implication of this result is that a minimum volume of magma is required for a volcanic eruption to occur for a given depth of magma reservoir.
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)
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.
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Gonzalez-Perez, A.; Ruso, J.M.; Nimo, J.; Rodriguez, J.R. E-mail: fmjulio@usc.es
2003-12-01
Density measurements of dodecyl- (C{sub 12}DBACl), tetradecyl- (C{sub 14}DBACl), hexadecyldimethylbenzylammonium chloride (C{sub 16}DBACl) and of decyl- (C{sub 10}DBABr) and dodecyldimethylbenzylammonium bromide (C{sub 12}DBABr) in aqueous solutions at T=15 deg. C and T=25 deg. C have been carried out. From these results, apparent and partial molar volumes were calculated. Positive deviations from the Debye-Hueckel limiting law provide evidence for limited association at concentrations below the critical micelle concentration. The change of the apparent molar volume upon micellization was calculated. The relevant parameters have been presented in function of the alkyl chain length. Apparent molar volumes of the present compounds in the micellar phase, V{sub phi}{sup m}, and the change upon micellization, {delta}V{sub phi}{sup m}, have been discussed in terms of temperature and type of counterion.
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.)
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).
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...... breathing in the sitting position ranged from 0.25 to 0.37 g.cm-3. Subnormal values were found in patients with emphsema. In patients with pulmonary congestion and edema, lung density values ranged from 0.33 to 0.93 g.cm-3. The lung density measurement correlated well with the findings in chest radiographs...... but the lung density values were more sensitive indices. This was particularly evident in serial observations of individual patients....
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.
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.
Institute of Scientific and Technical Information of China (English)
张明; 刘波; 潘雨婷; 张征
2015-01-01
While the proportion of photovoltaic power generation in the electrical power system is increasing year by year, its access system optimizing choice has become one of need-to-be- solved problems before accepting photovoltaic power generation. In this paper, based on a distributed photovoltaic power station case, it discussed and analyzed high density multi access points distributed PV access system solutions. It mainly focused on comprehensive comparison from several aspects, such as system active power loss and economic benefit. Under the premise of ensuring the normal distributed photovoltaic system power generation operation, it put forward recommended solutions for spontaneous generation for personal use, elimination on the spot, effectively reducing network loss and obtaining economic benefit.%随着光伏发电在电力系统中所占比重的逐年增大，其接入系统方案的优化选择成为电网在接纳光伏发电之前首先需要解决的问题之一。因此，本文以拟建的某分布式光伏电站为例，对高密度多接入点分布式光伏的接入系统方案进行了研究和分析，重点从系统有功损耗和经济效益等多方面进行了综合比选，在保证分布式光伏系统正常发电的前提下，提出了有利于自发自用、就地消纳、有效降低网损及经济效益的推荐方案。
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)
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
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
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.
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.
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...
... 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 ...
Ontogeny of body density and the swimbladder in yellowtail kingfish Seriola lalandi larvae.
Woolley, L D; Qin, J G
2013-02-01
The ontogeny of larval body density and the morphological and histological events during swimbladder development were investigated in two cohorts of yellowtail kingfish Seriola lalandi larvae to understand the relationship between larval morphology and body density. Larvae inflation occurred on 3 dph, and the inflation window was 3-5 dph when the pneumatic duct was still connected to the gut. The swimbladder volume increased with larval age and the epithelial lining on the swimbladder became flattened squamous cells after initial inflation. Seriola lalandi developed into a physoclist with the formation of the rete mirabile and the gas-secreting gland comprised low-columnar epithelial cells. Larvae with successfully inflated swimbladders remained positively buoyant, whereas larvae without SB inflation became negatively buoyant and their body density gradually reached 1.030 ± 0.001 g cm(-3) by 10 dph. Diel density changes were observed after 5 dph, owing to day time deflation and night-time inflation of the swimbladder. These results show that SB inflation has a direct effect on body density in larval S. lalandi and environmental factors should be further investigated to enhance the rate of SB inflation to prevent the sinking death syndrome in the early life stage of the fish larvae.
Ontogeny of body density and the swimbladder in yellowtail kingfish Seriola lalandi larvae.
Woolley, L D; Qin, J G
2013-02-01
The ontogeny of larval body density and the morphological and histological events during swimbladder development were investigated in two cohorts of yellowtail kingfish Seriola lalandi larvae to understand the relationship between larval morphology and body density. Larvae Seriola lalandi developed into a physoclist with the formation of the rete mirabile and the gas-secreting gland comprised low-columnar epithelial cells. Larvae with successfully inflated swimbladders remained positively buoyant, whereas larvae without SB inflation became negatively buoyant and their body density gradually reached 1.030 ± 0.001 g cm(-3) by 10 dph. Diel density changes were observed after 5 dph, owing to day time deflation and night-time inflation of the swimbladder. These results show that SB inflation has a direct effect on body density in larval S. lalandi and environmental factors should be further investigated to enhance the rate of SB inflation to prevent the sinking death syndrome in the early life stage of the fish larvae. PMID:23398074
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
van Duijnen, Piet Th.; Greene, Shannon N.; Richards, Nigel G. J.
2007-01-01
We report the calculated visible spectrum of [Fe-III(PyPepS)(2)](-) in aqueous solution. From all-classical molecular dynamics simulations on the solute and 200 water molecules with a polarizable force field, 25 solute/solvent configurations were chosen at random from a 50 ps production run and subj
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.
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
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.
Piezoelectric Energy Harvesting Solutions
Caliò, Renato; Rongala, Udaya Bhaskar; Camboni, Domenico; Milazzo, Mario; Stefanini, Cesare; de Petris, Gianluca; Oddo, Calogero Maria
2014-01-01
This paper reviews the state of the art in piezoelectric energy harvesting. It presents the basics of piezoelectricity and discusses materials choice. The work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions. The reviewed literature is compared based on power density and bandwidth. Lastly, the question of power conversion is addressed by reviewing various circuit solutions. PMID:24618725
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.
Degenerate density perturbation theory
Palenik, Mark C.; Dunlap, Brett I.
2016-09-01
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 Nd 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 α exchange-correlation (XC) functional, we find an analytic solution for the first-order density and first- through third-order energies as a function of α , 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.
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.
Kobryn, A E; Hirata, F
2005-01-01
We present results of theoretical study and numerical calculation of the dynamics of molecular liquids based on combination of the memory equation formalism and the reference interaction site model - RISM. Memory equations for the site-site intermediate scattering functions are studied in the mode-coupling approximation for the first order memory kernels, while equilibrium properties such as site-site static structure factors are deduced from RISM. The results include the temperature-density(pressure) dependence of translational diffusion coefficients D and orientational relaxation times t for acetonitrile in water, methanol in water and methanol in acetonitrile, all in the limit of infinite dilution. Calculations are performed over the range of temperatures and densities employing the SPC/E model for water and optimized site-site potentials for acetonitrile and methanol. The theory is able to reproduce qualitatively all main features of temperature and density dependences of D and t observed in real and comp...
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...
Institute of Scientific and Technical Information of China (English)
LI YouRong; GONG ZhenXing; WU ChunMei; WU ShuangYing
2012-01-01
Using asymptotical analysis,we investigate the characteristics of the coupled thermal and solutal capillary convection with the radial temperature and solute concentration gradients in a shallow annular pool with the free surface.The pool is heated from the outer cylinder with high solutal concentration and cooled at the inner cylinder with low solutal concentration.The asymptotic solution is obtained in the core region in the limit as the aspect ratio,which is defined as the ratio of the depth to the width of the pool,goes to zero.The comparison with the previous work certifies that the asymptotic solution is right and believable.The influences of the solutal capillary force,the buoyant force,the Soret effect and the geometric parameters on the fluid flow are analyzed.
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)
郝世峰; 楼茂园; 杨诗芳; 李超; 孔照林; 裘薇
2015-01-01
To solve atmospheric primitive equations, the finite difference approach would result in numerous problems, com-pared to the differential equations. Taking the semi-Lagrange model as an example, there exist two diﬃcult prob-lems——the particle trajectory computation and the solutions of the Helmholtz equations. In this study, based on the substitution of atmosphere pressure, the atmospheric primitive equations are linearized within an integral time step, which are broadly seen as ordinary differential equations and can be derived as semi-analytical solutions (SASs). The variables of SASs are continuous functions of time and discretized in a special direction, so the gradient and divergence terms are solved by the difference method. Since the numerical solution of the SASs can be calculated via a highly pre-cise numerical computational method of exponential matrix——the precise integration method, the numerical solution of SASs at any time in the future can be obtained via step-by-step integration procedure. For the SAS methodology, the pressure, as well as the wind vector and displacement, can be obtained without solving the Helmholtz formulations. Compared to the extrapolated method, the SAS is more reasonable as the displacements of the particle are solved via time integration. In order to test the validity of the algorithms, the SAS model is constructed and the same experi-ment of a non-linear density current as reported by Straka in 1993 is implemented, which contains non-linear dynamics, transient features and fine-scale structures of the fluid flow. The results of the experiment with 50 m spatial resolution show that the SAS model can capture the characters of generation and development process of the Kelvin-Helmholtz shear instability vortex; the structures of the perturbation potential temperature field are very close to the benchmark solutions given by Straka, as well as the structures of the simulated atmosphere pressure and wind field. To further
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
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.
Jang, Myungsu; Kim, Somin; Jeong, Haneul; Ju, Sang-Yong
2016-10-14
Sorted single-walled carbon nanotubes (SWNTs) are of paramount importance for their utilization in high-end optoelectronic applications. Sodium cholate (SC)-based density gradient ultracentrifugation (DGU) has been instrumental in isolating small diameter (d t) SWNTs. Here, we show that SWNTs wrapped by flavin mononucleotide (FMN) as a dispersing agent are sorted in DGU, and show sorting order reversal behavior, departing from prototypical SC-SWNT trends. Larger d t SWNTs are sorted in lower density (ρ), and buoyant ρ distribution of FMN-SWNT ranges from 1.15-1.25 g cm(-3). Such a nanotube layering pattern originates from both the binding affinity between FMN and SWNT and the less-susceptible hydrated volume of remote phosphate sidechains of FMN according to nanotube d t change. PMID:27595315
Jang, Myungsu; Kim, Somin; Jeong, Haneul; Ju, Sang-Yong
2016-10-01
Sorted single-walled carbon nanotubes (SWNTs) are of paramount importance for their utilization in high-end optoelectronic applications. Sodium cholate (SC)-based density gradient ultracentrifugation (DGU) has been instrumental in isolating small diameter (d t) SWNTs. Here, we show that SWNTs wrapped by flavin mononucleotide (FMN) as a dispersing agent are sorted in DGU, and show sorting order reversal behavior, departing from prototypical SC-SWNT trends. Larger d t SWNTs are sorted in lower density (ρ), and buoyant ρ distribution of FMN-SWNT ranges from 1.15-1.25 g cm-3. Such a nanotube layering pattern originates from both the binding affinity between FMN and SWNT and the less-susceptible hydrated volume of remote phosphate sidechains of FMN according to nanotube d t change.
DEFF Research Database (Denmark)
Efeoglu, Arkin; Møller, Charles; Serie, Michel
2013-01-01
This paper outlines an artifact building and evaluation proposal. Design Science Research (DSR) studies usually consider encapsulated artifact that have relationships with other artifacts. The solution prototype as a composed artifact demands for a more comprehensive consideration in its systemat...
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
Institute of Scientific and Technical Information of China (English)
周思同; 王永斌; 赵鹏; 路洋洋
2014-01-01
分析了漂浮电缆受力情况，给出了平静海面下的接收信号表达式，得到了信号电压与电场强度的近似关系式。分析了海浪对漂浮电缆的影响，建立了海浪下的漂浮电缆模型，推导出水下航行器的拖带速度和线缆深度的关系，并且推导了海浪下漂浮电缆的接收信号表达式，得到了信号电压与电场强度的近似关系式，从而为水下航行器漂浮电缆收信性能的计算与应用提供了参考。%First, the paper analyzes the method of submarine receiving signal in VLF in quietsea and the load-carrying capability of buoyant cable. It infers the receiving voltage under quiet sea depending on force analysis and gets the relation between signal voltage and E-field. Then, the sea wave effect to buoy-ant cable is analyzed, the model of buoyant cable under sea wave is set up, and antenna's receiving signal voltage under sea wave is inferred. The relationship between the underwater vehicle towing speed and cable depth is derived, and the relation between signal voltage and E-field is achieved, thus to provide reference for the performance of submarine receiving signal.
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.
Christov, Ivan C
2012-01-01
In classical continuum physics, a wave is a mechanical disturbance. Whether the disturbance is stationary or traveling and whether it is caused by the motion of atoms and molecules or the vibration of a lattice structure, a wave can be understood as a specific type of solution of an appropriate mathematical equation modeling the underlying physics. Typical models consist of partial differential equations that exhibit certain general properties, e.g., hyperbolicity. This, in turn, leads to the possibility of wave solutions. Various analytical techniques (integral transforms, complex variables, reduction to ordinary differential equations, etc.) are available to find wave solutions of linear partial differential equations. Furthermore, linear hyperbolic equations with higher-order derivatives provide the mathematical underpinning of the phenomenon of dispersion, i.e., the dependence of a wave's phase speed on its wavenumber. For systems of nonlinear first-order hyperbolic equations, there also exists a general ...
The Hatteras Front: August 2004 velocity and density structure
Savidge, Dana K.; Austin, Jay A.
2007-07-01
The Hatteras Front is a persistent mesoscale cross-shelf oriented front off Cape Hatteras, North Carolina. It is the boundary between relatively cool, fresh Mid-Atlantic Bight shelf waters and warmer, saltier shelf waters of the South Atlantic Bight, which both converge along-shelf upon Cape Hatteras year round. The Frontal Interaction Near Cape Hatteras (FINCH) project was conducted in 2004-2005 to intensively sample the Hatteras Front with shipboard ADCP and undulating towed CTD. This paper documents velocity and density structures associated with the cross-shelf oriented zone of Hatteras Front during the August 2004 field season. Property gradients across the Hatteras Front are large, with temperature (T) and salinity (S) differences of ˜4-6°C, 2-5 psu, respectively over distances of 1-2 km. The T and S are not completely compensating, and a strong density (ρ) gradient also exists, with Δρ of ˜2 kg/m3 across a gentler 10 km wide front. The density gradient results in a steric sea-level height gradient of ˜1-2 cm across the Front, which is in approximate geostrophic balance with a surface intensified jet, directed shoreward along the cross-shelf oriented Front. The velocity is sheared with depth at 3.0 × 10-2 to 5.0 × 10-2 s-1 in the upper 5 m of the jet; a rate consistent with the density gradient according to the thermal wind relationship. Shoreward transport of ˜4.8 × 104 m3/s results from the surface intensified jet. The structure of the velocity field associated with the Hatteras Front resembles that of a slope-controlled buoyant plume, as described by Lentz and Helfrich (2002). Velocity and density structures are similar during both advancing (southwestward) and retreating (northeastward) motion of the Front.
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.
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
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.
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.
Direct Density Derivative Estimation.
Sasaki, Hiroaki; Noh, Yung-Kyun; Niu, Gang; Sugiyama, Masashi
2016-06-01
Estimating the derivatives of probability density functions is an essential step in statistical data analysis. A naive approach to estimate the derivatives is to first perform density estimation and then compute its derivatives. However, this approach can be unreliable because a good density estimator does not necessarily mean a good density derivative estimator. To cope with this problem, in this letter, we propose a novel method that directly estimates density derivatives without going through density estimation. The proposed method provides computationally efficient estimation for the derivatives of any order on multidimensional data with a hyperparameter tuning method and achieves the optimal parametric convergence rate. We further discuss an extension of the proposed method by applying regularized multitask learning and a general framework for density derivative estimation based on Bregman divergences. Applications of the proposed method to nonparametric Kullback-Leibler divergence approximation and bandwidth matrix selection in kernel density estimation are also explored. PMID:27140943
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...
Information Geometric Density Estimation
Sun, Ke; Marchand-Maillet, Stéphane
2014-01-01
We investigate kernel density estimation where the kernel function varies from point to point. Density estimation in the input space means to find a set of coordinates on a statistical manifold. This novel perspective helps to combine efforts from information geometry and machine learning to spawn a family of density estimators. We present example models with simulations. We discuss the principle and theory of such density estimation.
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...
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
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.
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.
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.
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
The role of adequate reference materials in density measurements in hemodialysis
Furtado, A.; Moutinho, J.; Moura, S.; Oliveira, F.; Filipe, E.
2015-02-01
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.
Magnetic Half-Monopole Solutions
Teh, Rosy; Lim, Kok-Geng; Koh, Pin-Wai
2009-07-01
We present exact SU(2) Yang-Mills-Higgs monopole solutions of one half topological charge. These non-Abelian solutions possess gauge potentials which are singular along either the positive or the negative z-axis and common magnetic fields that are singular only at the origin where the half-monopole is located. These half-monopoles are actually a half Wu-Yang monopole and they can possess a finite point electric charge and become half-dyons. They do not necessarily satisfy the first order Bogomol'nyi equations and they possess infinite energy density at r = 0.
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.
Adaptive kernel density estimation
Philippe Van Kerm
2003-01-01
This insert describes the module akdensity. akdensity extends the official kdensity that estimates density functions by the kernel method. The extensions are of two types: akdensity allows the use of an "adaptive kernel" approach with varying, rather than fixed, bandwidths; and akdensity estimates pointwise variability bands around the estimated density functions. Copyright 2003 by Stata Corporation.
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.
Trautmann, Wolfgang; Russotto, Paolo
2016-01-01
The nuclear equation-of-state is a topic of highest current interest in nuclear structure and reactions as well as in astrophysics. In particular, the equation-of-state of asymmetric matter and the symmetry energy representing the difference between the energy densities of neutron matter and of symmetric nuclear matter are not sufficiently well constrained at present. The density dependence of the symmetry energy is conventionally expressed in the form of the slope parameter L describing the derivative with respect to density of the symmetry energy at saturation. Results deduced from nuclear structure and heavy-ion reaction data are distributed around a mean value L=60 MeV. Recent studies have more thoroughly investigated the density range that a particular observable is predominantly sensitive to. Two thirds of the saturation density is a value typical for the information contained in nuclear-structure data. Higher values exceeding saturation have been shown to be probed with meson production and collective ...
Learning Grasp Affordance Densities
DEFF Research Database (Denmark)
Detry, Renaud; Kraft, Dirk; Kroemer, Oliver;
2011-01-01
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...... these and 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...... 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...
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
... 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 ( ...
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
Veeder, G. J.
1974-01-01
An improved mass-luminosity relation for faint main-sequence stars derived from recently revised masses for some faint double stars is presented. The total local mass density is increased to nearly 0.2 solar masses per cu pc. This estimate is as large as the mass density required by Oort's (1965) dynamical analysis of stellar motions perpendicular to the galactic plane if the mass is concentrated in a narrow layer.
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...
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
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
Ayala, A P; Levin, E M
1998-01-01
In this paper we re-analyse the situation with the shadowing corrections (SC) in QCD for the proton deep inelastic structure functions. We reconsider the Glauber - Mueller approach for the SC in deep inelastic scattering (DIS) and suggest a new nonlinear evolution equation. We argue that this equation solves the problem of the SC in the wide kinematic region where $\\as\\, \\kappa \\,=\\,\\as\\,\\frac{3 \\pi \\as}{2 Q^2R^2}\\,x G(x,Q^2) out to be essential in the gluon deep inelastic structure function but rather small in $F_2(x,Q^2)$. We claim that the SC in $xG(x,Q^2)$ is so large that the BFKL Pomeron is hidden under the SC and cannot be seen even in such ``hard" processes that have been proposed to test it. We found that the gluon density is proportional to $\\ln(1/x)$ in the region of very small $x$. This result means that the gluon density does not reach saturation in the region of applicability of the new evolution equation. It should be confronted with the solution of the GLR equation which leads to saturation.
Yoon, Sung-Soo; Khang, Dahl-Young
2013-12-26
A simple and facile method to fabricate SiO2 micro- or nanotubes has been demonstrated based on room temperature wet chemical oxidation of a porous layer of Si pillar templates that have been prepared by metal-assisted chemical etching (MaCE). Under typical conditions, Si pillars produced by the MaCE have been found to be covered with a thin nanoporous Si layer. The porous Si skin layer has been chemically oxidized by simple dipping in AgNO3 solution at room temperature, which has led to seamless SiO2 shell layer thanks to the accompanying volume expansion during the wet oxidation. Following wet removal of core Si by KOH yields the SiO2 micro- or nanotubes, either in test tube shape or in open shape at both ends, depending on processing method. The vertical arrays of the SiO2 tube on the Si substrate, after hydrophobic siloxane oligomer printing, has been found to have very large loading capacity on water, due to extremely high porosity (>90%) and good enough mechanical stability. The novel method to fabricate SiO2 tubes can shed new light in design of novel aquatic devices, other than simple mimicking the leg of a water strider. Also, the method may be very helpful in various applications of SiO2 nanotubes. PMID:24313459
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.
Benbow, Steven J; Rivett, Michael O; Chittenden, Neil; Herbert, Alan W; Watson, Sarah; Williams, Steve J; Norris, Simon
2014-10-15
A safety case for the disposal of Intermediate Level (radioactive) Waste (ILW) in a deep geological disposal facility (GDF) requires consideration of the potential for waste-derived light non-aqueous phase liquid (LNAPL) to migrate under positive buoyancy from disposed waste packages. Were entrainment of waste-derived radionuclides in LNAPL to occur, such migration could result in a shorter overall travel time to environmental or human receptors than radionuclide migration solely associated with the movement of groundwater. This paper provides a contribution to the assessment of this issue through multiphase-flow numerical modelling underpinned by a review of the UK's ILW inventory and literature to define the nature of the associated ILW LNAPL source term. Examination has been at the waste package-local GDF environment scale to determine whether proposed disposal of ILW would lead to significant likelihood of LNAPL migration, both from waste packages and from a GDF vault into the local host rock. Our review and numerical modelling support the proposition that the release of a discrete free phase LNAPL from ILW would not present a significant challenge to the safety case even with conservative approximations. 'As-disposed' LNAPL emplaced with the waste is not expected to pose a significant issue. 'Secondary LNAPL' generated in situ within the disposed ILW, arising from the decomposition of plastics, in particular PVC (polyvinyl chloride), could form the predominant LNAPL source term. Released high molecular weight phthalate plasticizers are judged to be the primary LNAPL potentially generated. These are expected to have low buoyancy-based mobility due to their very low density contrast with water and high viscosity. Due to the inherent uncertainties, significant conservatisms were adopted within the numerical modelling approach, including: the simulation of a deliberately high organic material--PVC content wastestream (2D03) within an annular grouted waste package
Benbow, Steven J; Rivett, Michael O; Chittenden, Neil; Herbert, Alan W; Watson, Sarah; Williams, Steve J; Norris, Simon
2014-10-15
A safety case for the disposal of Intermediate Level (radioactive) Waste (ILW) in a deep geological disposal facility (GDF) requires consideration of the potential for waste-derived light non-aqueous phase liquid (LNAPL) to migrate under positive buoyancy from disposed waste packages. Were entrainment of waste-derived radionuclides in LNAPL to occur, such migration could result in a shorter overall travel time to environmental or human receptors than radionuclide migration solely associated with the movement of groundwater. This paper provides a contribution to the assessment of this issue through multiphase-flow numerical modelling underpinned by a review of the UK's ILW inventory and literature to define the nature of the associated ILW LNAPL source term. Examination has been at the waste package-local GDF environment scale to determine whether proposed disposal of ILW would lead to significant likelihood of LNAPL migration, both from waste packages and from a GDF vault into the local host rock. Our review and numerical modelling support the proposition that the release of a discrete free phase LNAPL from ILW would not present a significant challenge to the safety case even with conservative approximations. 'As-disposed' LNAPL emplaced with the waste is not expected to pose a significant issue. 'Secondary LNAPL' generated in situ within the disposed ILW, arising from the decomposition of plastics, in particular PVC (polyvinyl chloride), could form the predominant LNAPL source term. Released high molecular weight phthalate plasticizers are judged to be the primary LNAPL potentially generated. These are expected to have low buoyancy-based mobility due to their very low density contrast with water and high viscosity. Due to the inherent uncertainties, significant conservatisms were adopted within the numerical modelling approach, including: the simulation of a deliberately high organic material--PVC content wastestream (2D03) within an annular grouted waste package
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...
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
Energy Technology Data Exchange (ETDEWEB)
Vranjes, J., E-mail: jvranjes@yahoo.com [Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife (Spain); Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife (Spain); Kono, M., E-mail: kono@fps.chuo-u.ac.jp [Faculty of Policy Studies, Chuo University, Tokyo (Japan)
2015-01-15
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 cylindrical configuration. This is of practical importance for drift wave instability in various plasmas, and, in particular, in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit volume (per second) in quiet regions in the corona. Consequently, within the life-time of a magnetic structure such energy losses can easily be compensated by the stochastic drift wave heating.
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.
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.
The Asymptotic Regime of High Density QCD
Gay-Ducati, M B
2000-01-01
We discuss the distinct approaches for high density QCD (hdQCD) in the asymptotic regime of large values of parton density. We derive the AGL equation for running coupling constant and obtain the asymptotic solution, demonstrating that the property of partial saturation of the solution of the AGL equation is not modified by the running of the coupling constant. We show that in this kinematical regime, the solution of the AGL equation coincides with the solution of an evolution equation, obtained recently using the McLerran-Venugopalan approach. Using the asymptotic behavior of the gluon distribution we calculate the $F_2$ structure function assuming first that the leading twist relation between these two quantities is valid and second that this relation is modified by the higher twist terms associated to the unitarity corrections. In the first case we obtain that the corresponding $F_2$ structure function is linearly proportional to $ln s$, which agrees with the results obtained recently by Kovchegov using a ...
Hadron form factors using density-density correlators
Alexandrou, C.; Koutsou, G.; Neff, H.
2006-01-01
Gauge invariant density-density correlators yield detailed information on hadron structure. Hadron deformation and form factors can be extracted for momentum transfers up to about 6 GeV$^2$. We use stochastic techniques and dilution to compute the all to all propagator required for the exact evaluation of density-density correlators. We present first results for the pion form factor.
Strong shock implosion, approximate solution
Fujimoto, Y.; Mishkin, E. A.; Alejaldre, C.
1983-01-01
The self-similar, center-bound motion of a strong spherical, or cylindrical, shock wave moving through an ideal gas with a constant, γ= cp/ cv, is considered and a linearized, approximate solution is derived. An X, Y phase plane of the self-similar solution is defined and the representative curved of the system behind the shock front is replaced by a straight line connecting the mappings of the shock front with that of its tail. The reduced pressure P(ξ), density R(ξ) and velocity U1(ξ) are found in closed, quite accurate, form. Comparison with numerically obtained results, for γ= {5}/{3} and γ= {7}/{5}, is shown.
On the charge density and asymptotic tail of a monopole
Harland, Derek
2015-01-01
We propose a new definition for the abelian magnetic charge density of a non-abelian monopole, based on zero-modes of an associated Dirac operator. Unlike the standard definition of the charge density, this density is smooth in the core of the monopole. We show that this charge density induces a magnetic field whose expansion in powers of 1/r agrees with that of the conventional asymptotic magnetic field to all orders. We also show that the asymptotic field can be easily calculated from the spectral curve. Explicit examples are given for known monopole solutions.
Quantitative scattering of melanin solutions
Riesz, J; Meredith, P; Gilmore, Joel; Meredith, Paul; Riesz, Jennifer
2005-01-01
The optical scattering coefficient of a dilute, well solubilised eumelanin solution has been accurately measured as a function of incident wavelength, and found to contribute less than 6% of the total optical attenuation between 210 and 325nm. At longer wavelengths (325nm to 800nm) the scattering was less than the minimum sensitivity of our instrument. This indicates that UV and visible optical density spectra can be interpreted as true absorption with a high degree of confidence. The scattering coefficient vs wavelength was found to be consistent with Rayleigh Theory for a particle radius of 38+-1nm.
Ayala, A P; Levin, E M
1996-01-01
In this talk we present our detail study ( theory and numbers) [1] on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather contraversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula [2] and estimate the value of the shadowing corrections in this case. Than we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus - nucleus cascade.
Quasiconvexity and density topology
Rabier, Patrick J
2012-01-01
We prove that if f : R^N --> R is quasiconvex and U is open in the density topology of R^N, then sup_U f = ess sup_U f, while inf_U f = ess inf_U f if and only if the equality holds when U = R^N. The first (second) property is typical of lsc (usc) functions and, even when U is an ordinary open subset, there seems to be no record that they both hold for all quasiconvex functions. This property ensures that the pointwise extrema of f on any nonempty density open subset can be arbitrarily closely approximated by values of f achieved on "large" subsets, which may be of relevance in a variety of issues. To support this claim, we use it to characterize the common points of continuity, or approximate continuity, of two quasiconvex functions that coincide away from a set of measure zero.
Quantal density functional theory
Sahni, Viraht
2016-01-01
This book deals with quantal density functional theory (QDFT) which is a time-dependent local effective potential theory of the electronic structure of matter. The treated time-independent QDFT constitutes a special case. In the 2nd edition, the theory is extended to include the presence of external magnetostatic fields. The theory is a description of matter based on the ‘quantal Newtonian’ first and second laws which is in terms of “classical” fields that pervade all space, and their quantal sources. The fields, which are explicitly defined, are separately representative of electron correlations due to the Pauli exclusion principle, Coulomb repulsion, correlation-kinetic, correlation-current-density, and correlation-magnetic effects. The book further describes Schrödinger theory from the new physical perspective of fields and quantal sources. It also describes traditional Hohenberg-Kohn-Sham DFT, and explains via QDFT the physics underlying the various energy functionals and functional derivatives o...
Langfeld, Kurt
2016-01-01
Although Monte Carlo calculations using Importance Sampling have matured into the most widely employed method for determining first principle results in QCD, they spectacularly fail for theories with a sign problem or for which certain rare configurations play an important role. Non-Markovian Random walks, based upon iterative refinements of the density-of-states, overcome such overlap problems. I will review the Linear Logarithmic Relaxation (LLR) method and, in particular, focus onto ergodicity and exponential error suppression. Applications include the high-state Potts model, SU(2) and SU(3) Yang-Mills theories as well as a quantum field theory with a strong sign problem: QCD at finite densities of heavy quarks.
Spectrophotometric determination of zinc in impure solutions
International Nuclear Information System (INIS)
A dithizone colorimetric method is described for determining zinc concentrations of 0.001 to 5 g/l in aqueous solutions from Rio Tinto Mines, containing copper, iron and other impurities. Citrate, cyanide and bis-2hydroxyethyl)-dithiocarbamate are added to the aqueous sample of masking several metals, and zinc is extracted at pH 5 with a solution of dithizone in carbon tetrachloride. Excess of dithizone is removed with sodium sulphide, and optical density of zinc dithionate in organic solution is measured at 5.35 nm. Calibration curves obey Beer's law up to 0.5 micro Zn/ml. (Author) 5 refs
Contingent kernel density estimation.
Directory of Open Access Journals (Sweden)
Scott Fortmann-Roe
Full Text Available Kernel density estimation is a widely used method for estimating a distribution based on a sample of points drawn from that distribution. Generally, in practice some form of error contaminates the sample of observed points. Such error can be the result of imprecise measurements or observation bias. Often this error is negligible and may be disregarded in analysis. In cases where the error is non-negligible, estimation methods should be adjusted to reduce resulting bias. Several modifications of kernel density estimation have been developed to address specific forms of errors. One form of error that has not yet been addressed is the case where observations are nominally placed at the centers of areas from which the points are assumed to have been drawn, where these areas are of varying sizes. In this scenario, the bias arises because the size of the error can vary among points and some subset of points can be known to have smaller error than another subset or the form of the error may change among points. This paper proposes a "contingent kernel density estimation" technique to address this form of error. This new technique adjusts the standard kernel on a point-by-point basis in an adaptive response to changing structure and magnitude of error. In this paper, equations for our contingent kernel technique are derived, the technique is validated using numerical simulations, and an example using the geographic locations of social networking users is worked to demonstrate the utility of the method.
Chiral density wave in nuclear matter
Energy Technology Data Exchange (ETDEWEB)
Heinz, Achim [Institute for Theoretical Physics, Goethe University, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main (Germany); Giacosa, Francesco [Institute for Theoretical Physics, Goethe University, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main (Germany); Institute of Physics, Jan Kochanowski University, 25-406 Kielce (Poland); Rischke, Dirk H. [Institute for Theoretical Physics, Goethe University, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main (Germany)
2015-01-15
Inspired by recent work on inhomogeneous chiral condensation in cold, dense quark matter within models featuring quark degrees of freedom, we investigate the chiral density-wave solution in nuclear matter at zero temperature and nonvanishing baryon number density in the framework of the so-called extended linear sigma model (eLSM). The eLSM is an effective model for the strong interaction based on the global chiral symmetry of quantum chromodynamics (QCD). It contains scalar, pseudoscalar, vector, and axial-vector mesons as well as baryons. In the latter sector, the nucleon and its chiral partner are introduced as parity doublets in the mirror assignment. The eLSM simultaneously provides a good description of hadrons in vacuum as well as nuclear matter ground-state properties. We find that an inhomogeneous phase in the form of a chiral density wave is realized, but only for densities larger than 2.4ρ{sub 0}, where ρ{sub 0} is the nuclear matter ground-state density.
Water Density Fluctuations Relevant to Hydrophobic Hydration are Unaltered by Attractions
Remsing, Richard C
2014-01-01
An understanding of density fluctuations in bulk water has made significant contributions to our understanding of the hydration and interactions of idealized, purely repulsive hydrophobic solutes. To similarly inform the hydration of realistic hydrophobic solutes that have dispersive interactions with water, here we characterize water density fluctuations in the presence of attractive fields that correspond to solute-water attractions. We find that when the attractive field acts only in the solute hydration shell, but not in the solute core, it does not significantly alter water density fluctuations in the solute core region. We further find that for a wide range of solute sizes and attraction strengths, the free energetics of turning on the attractive fields in bulk water are accurately captured by linear response theory. Our results also suggest strategies for more efficiently estimating hydration free energies of realistic solutes in bulk water and at interfaces.
Generalized Solutions of Functional Differential Inclusions
Directory of Open Access Journals (Sweden)
Anna Machina
2008-01-01
Full Text Available We consider the initial value problem for a functional differential inclusion with a Volterra multivalued mapping that is not necessarily decomposable in L1n[a,b]. The concept of the decomposable hull of a set is introduced. Using this concept, we define a generalized solution of such a problem and study its properties. We have proven that standard results on local existence and continuation of a generalized solution remain true. The question on the estimation of a generalized solution with respect to a given absolutely continuous function is studied. The density principle is proven for the generalized solutions. Asymptotic properties of the set of generalized approximate solutions are studied.
Density measures and additive property
Kunisada, Ryoichi
2015-01-01
We deal with finitely additive measures defined on all subsets of natural numbers which extend the asymptotic density (density measures). We consider a class of density measures which are constructed from free ultrafilters on natural numbers and study a certain additivity property of such density measures.
Simulation of nanoscale density fluctuations
Reiss, Howard; Bowles, Richard K.
2000-11-01
Problems associated with the simulation of density fluctuations of limited breadth in a small cell are exposed and studied. The fluctuations are viewed as "physical clusters" of the type that might appear in nucleation processes and related phenomena. One of the most important features of the study stems from the fact that the simulation of a small heterogeneity in a macroscopic system presents problems that do not occur in the simulation of a bulk homogeneous property of the system. For example, once having simulated the probability of appearance of the fluctuation in a small cell, how is that result to be "mapped" onto the macrosystem in order to specify the equilibrium number of such fluctuations in that system? This problem is closely associated with the proper separation of the translational and internal degrees of freedom of the system, and has arisen in a number of fields, including the theory of nucleation. There are other problems associated with exponential dependence of cluster probability on the work of formation of the cluster, and also with rareness of some important clusters. In the latter case, simulative "umbrella sampling" does not always solve the entire problem. The present study is confined to clusters that appear in rarefied gases. Such systems are important in a number of scenarios, including nucleation processes. Several cluster models are considered including those consisting of molecules confined to a "container" of fixed volume and those constructed on the center of mass of the cluster. Connections between them are derived and rigorous solutions to the mapping problem are derived. Quantitative measures for the accuracy of approximate solutions, applied to cases in which the cluster is compact, are provided and exact solutions are provided even for the noncompact case. Some surprising results emerge from the study, among which is the fact that a cluster whose location is determined by one of its molecules, does not always have a
High energy density in multisoliton collisions
Saadatmand, Danial; Dmitriev, Sergey V.; Kevrekidis, Panayotis G.
2015-09-01
Solitons are very effective in transporting energy over great distances and collisions between them can produce high energy density spots of relevance to phase transformations, energy localization and defect formation among others. It is then important to study how energy density accumulation scales in multisoliton collisions. In this study, we demonstrate that the maximal energy density that can be achieved in collision of N slowly moving kinks and antikinks in the integrable sine-Gordon field, remarkably, is proportional to N2, while the total energy of the system is proportional to N . This maximal energy density can be achieved only if the difference between the number of colliding kinks and antikinks is minimal, i.e., is equal to 0 for even N and 1 for odd N and if the pattern involves an alternating array of kinks and antikinks. Interestingly, for odd (even) N the maximal energy density appears in the form of potential (kinetic) energy, while kinetic (potential) energy is equal to zero. The results of the present study rely on the analysis of the exact multisoliton solutions for N =1 ,2 , and 3 and on the numerical simulation results for N =4 ,5 ,6 , and 7. The effect of weak Hamiltonian and non-Hamiltonian perturbations on the maximal energy density in multikink collisions is also discussed as well as that of the collision relative phase. Based on these results one can speculate that the soliton collisions in the sine-Gordon field can, in principle, controllably produce very high energy density. This can have important consequences for many physical phenomena described by the Klein-Gordon equations.
On Shearing Fluids with Homogeneous Densities
Srivastava, D C; Kumar, Rajesh
2016-01-01
In this paper, we study shearing spherically symmetric homogeneous density fluids in comoving coordinates. It is found that the expansion of the four-velocity of a perfect fluid is homogeneous, whereas its shear is generated by an arbitrary function of time M(t), related to the mass function of the distribution. This function is found to bear a functional relationship with density. The field equations are reduced to two coupled first order ordinary differential equations for the metric coefficients, g 11 and g 22. We have explored a class of solutions assuming that M is a linear function of the density. This class embodies, as a subcase, the complete class of shear-free solutions. We have discussed the off quoted work of Kustaanheimo (1947) and have noted that it deals with shear-free fluids having anisotropic pressure. It is shown that the anisotropy of the fluid is characterized by an arbitrary function of time. We have discussed some issues of historical priorities and credentials related to shear-free sol...
Density functional theory: Foundations reviewed
Energy Technology Data Exchange (ETDEWEB)
Kryachko, Eugene S., E-mail: eugene.kryachko@ulg.ac.be [Bogolyubov Institute for Theoretical Physics, Kiev, 03680 (Ukraine); Ludeña, Eduardo V., E-mail: popluabe@yahoo.es [Centro de Química, Instituto Venezolano de Investigaciones Científicas, IVIC, Apartado 21827, Caracas 1020-A (Venezuela, Bolivarian Republic of); Prometheus Program, Senescyt (Ecuador); Grupo Ecuatoriano para el Estudio Experimental y Teórico de Nanosistemas, GETNano, USFQ, N104-E, Quito (Ecuador); Escuela Politécnica Superior del Litoral, ESPOL, Guayaquil (Ecuador)
2014-11-10
Guided by the above motto (quotation), we review a broad range of issues lying at the foundations of Density Functional Theory, DFT, a theory which is currently omnipresent in our everyday computational study of atoms and molecules, solids and nano-materials, and which lies at the heart of modern many-body computational technologies. The key goal is to demonstrate that there are definitely the ways to improve DFT. We start by considering DFT in the larger context provided by reduced density matrix theory (RDMT) and natural orbital functional theory (NOFT), and examine the implications that N-representability conditions on the second-order reduced density matrix (2-RDM) have not only on RDMT and NOFT but, also, by extension, on the functionals of DFT. This examination is timely in view of the fact that necessary and sufficient N-representability conditions on the 2-RDM have recently been attained. In the second place, we review some problems appearing in the original formulation of the first Hohenberg–Kohn theorem which is still a subject of some controversy. In this vein we recall Lieb’s comment on this proof and the extension to this proof given by Pino et al. (2009), and in this context examine the conditions that must be met in order that the one-to-one correspondence between ground-state densities and external potentials remains valid for finite subspaces (namely, the subspaces where all Kohn–Sham solutions are obtained in practical applications). We also consider the issue of whether the Kohn–Sham equations can be derived from basic principles or whether they are postulated. We examine this problem in relation to ab initio DFT. The possibility of postulating arbitrary Kohn–Sham-type equations, where the effective potential is by definition some arbitrary mixture of local and non-local terms, is discussed. We also deal with the issue of whether there exists a universal functional, or whether one should advocate instead the construction of problem
Contact Lens Solution Toxicity
... rash and rashes clinical tools newsletter | contact Share | Contact Lens Solution Toxicity Information for adults A A A This image shows a reaction to contact lens solution. The prominent blood vessels and redness ...
International Nuclear Information System (INIS)
This Functional Design Criteria (FDC) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage
The Geometrical Structure of the Tolman VII solution
Raghoonundun, Ambrish M
2016-01-01
The Tolman~VII solution, an exact analytic solution to the spherically symmetric, static Einstein equations with a perfect fluid source, has many characteristics that make it interesting for modelling high density physical astronomical objects. Here we supplement those characteristics with the geometrical tensors that this solution possess, and find that the Weyl, Riemann, and Ricci tensor components show unexpected mathematical behaviour that change depending on physically motivated parameters, even though the mass of the modelled objects is fixed. We show these features firstly through tensor components, and then through the scalars in the null tetrad formalism of Newmann and Penrose. The salient conclusion of this analysis is the intimate relationship between the Tolman~VII solution and the constant density Schwarzschild interior solution: the former being a straight forward generalization of the latter while eschewing the unphysical constant density.
Boson ground state fields in electroweak theory with non-zero charge densities
Syska, J.
2002-01-01
The "non-linear" self-consistent theory of classical fields in the electroweak model is proposed. Homogeneous boson ground state solutions in the GSW model at the presence of a non-zero extended fermionic charge densities are reviewed and fully reinterpreted to make the theory with non-zero charge densities fruitful. Consequences of charge density fluctuations are proposed.
Buoyant Rover for Under-Ice Exploration
Berisford, D. F.; Leichty, J. M.; Klesh, A. T.; Matthews, J. B.; Hand, K. P.
2012-12-01
We have designed, constructed and tested a prototype robotic mobility platform for exploring the underside of ice sheets in frozen lake or ocean environments. The ice-water interface often provides some of the most interesting and dynamic chemistry in partially frozen systems, as dissolved impurities are rejected from the advancing freezing front. Higher concentrations of microorganisms can be found in this region, and the topography of the ice underside can help reveal the history of its formation. Furthermore, in lake environments ice cover can serve to trap gases released from biological and geological processes in the subsurface. The rover uses a two-wheeled design with a flexible dragging tail, enabling it to fit into a 10-inch diameter ice borehole. The sealed air-filled cylindrical body, along with closed-cell foam inside of cone-shaped wheels, provides buoyancy force to enable roving along the underside of the ice. The prototype contains two cameras that stream live video via a tethered connection to a ground station and uses semi-autonomous control via a PC. Preliminary testing of the prototype in a cold lab and in northern Alaskan thermokarst lakes demonstrates the utility and simplicity of this type of robotic platform for exploring the ice-water interface. This technology has potential future use in landed missions to icy ocean worlds in the solar system.
Paramagnetic ionic liquids for measurements of density using magnetic levitation.
Bwambok, David K; Thuo, Martin M; Atkinson, Manza B J; Mirica, Katherine A; Shapiro, Nathan D; Whitesides, George M
2013-09-01
Paramagnetic ionic liquids (PILs) provide new capabilities to measurements of density using magnetic levitation (MagLev). In a typical measurement, a diamagnetic object of unknown density is placed in a container containing a PIL. The container is placed between two magnets (typically NdFeB, oriented with like poles facing). The density of the diamagnetic object can be determined by measuring its position in the magnetic field along the vertical axis (levitation height, h), either as an absolute value or relative to internal standards of known density. For density measurements by MagLev, PILs have three advantages over solutions of paramagnetic salts in aqueous or organic solutions: (i) negligible vapor pressures; (ii) low melting points; (iii) high thermal stabilities. In addition, the densities, magnetic susceptibilities, glass transition temperatures, thermal decomposition temperatures, viscosities, and hydrophobicities of PILs can be tuned over broad ranges by choosing the cation-anion pair. The low melting points and high thermal stabilities of PILs provide large liquidus windows for density measurements. This paper demonstrates applications and advantages of PILs in density-based analyses using MagLev. PMID:23972068
Gedanken Densities and Exact Constraints in Density Functional Theory
Perdew, John P; Sun, Jianwei; Burke, Kieron
2014-01-01
Approximations to the exact density functional for the exchange-correlation energy of a many-electron ground state can be constructed by satisfying constraints that are universal, i.e., valid for all electron densities. Gedanken densities are designed for the purpose of this construction, but need not be realistic. The uniform electron gas is an old gedanken density. Here, we propose a spherical two-electron gedanken density in which the dimensionless density gradient can be an arbitrary positive constant wherever the density is non-zero. The Lieb-Oxford lower bound on the exchange energy can be satisfied within a generalized gradient approximation (GGA) by bounding its enhancement factor or simplest GGA exchange-energy density. This enhancement-factor bound is well known to be sufficient, but our gedanken density shows that it is also necessary. The conventional exact exchange-energy density satisfies no such local bound, but energy densities are not unique, and the simplest GGA exchange-energy density is no...
Ducati, M B G
2001-01-01
The dynamics of high partonic density QCD is presented considering, in the double logarithm approximation, the parton recombination mechanism built in the AGL formalism, developed including unitarity corrections for the nucleon as well for nucleus. It is shown that these corrections are under theoretical control. The resulting non linear evolution equation is solved in the asymptotic regime, and a comprehensive phenomenology concerning Deep Inelastic Scattering like $F_2$, $F_L$, $F_2^c$. $\\partial F_2/ \\partial \\ln Q^2$, $\\partial F^A_2/ \\partial \\ln Q^2$, etc, is presented. The connection of our formalism with the DGLAP and BFKL dynamics, and with other perturbative (K) and non-perturbative (MV-JKLW) approaches is analised in detail. The phenomena of saturation due to shadowing corrections and the relevance of this effect in ion physics and heavy quark production is emphasized. The implications to e-RHIC, HERA-A, and LHC physics and some open questions are mentioned.
Lin, Yue; Li, Cheng
2012-01-01
Nearest neighbors search is a fundamental problem in various research fields like machine learning, data mining and pattern recognition. Recently, hashing-based approaches, e.g., Locality Sensitive Hashing (LSH), are proved to be effective for scalable high dimensional nearest neighbors search. Many hashing algorithms found their theoretic root in random projection. Since these algorithms generate the hash tables (projections) randomly, a large number of hash tables (i.e., long codewords) are required in order to achieve both high precision and recall. To address this limitation, we propose a novel hashing algorithm called {\\em Density Sensitive Hashing} (DSH) in this paper. DSH can be regarded as an extension of LSH. By exploring the geometric structure of the data, DSH avoids the purely random projections selection and uses those projective functions which best agree with the distribution of the data. Extensive experimental results on real-world data sets have shown that the proposed method achieves better ...
DEFF Research Database (Denmark)
Christensen, Ole; Heil, Christopher; Deng, Baiqiao
1999-01-01
A Gabor system is a set of time-frequency shifts S(g, Lambda) = {e(2 pi ibx) g(x - a)}((a,b)is an element of Lambda) of a function g is an element of L-2(R-d). We prove that if a finite union of Gabor systems boolean (ORk=1S)-S-r(g(k), Lambda(k)) forms a frame for L-2(R-d) then the lower and upper...... Beurling densities of Lambda = boolean ORk=1r Lambda(k) satisfy D- (Lambda) greater than or equal to 1 and D+(Lambda) boolean ORk=1r {g(k)(x - a)}(a is an element of Gamma k) of pure...
Oberacker, V E
2015-01-01
In this manuscript we provide an outline of the numerical methods used in implementing the density constrained time-dependent Hartree-Fock (DC-TDHF) method and provide a few examples of its application to nuclear fusion. In this approach, dynamic microscopic calculations are carried out on a three-dimensional lattice and there are no adjustable parameters, the only input is the Skyrme effective NN interaction. After a review of the DC-TDHF theory and the numerical methods, we present results for heavy-ion potentials $V(R)$, coordinate-dependent mass parameters $M(R)$, and precompound excitation energies $E^{*}(R)$ for a variety of heavy-ion reactions. Using fusion barrier penetrabilities, we calculate total fusion cross sections $\\sigma(E_\\mathrm{c.m.})$ for reactions between both stable and neutron-rich nuclei. We also determine capture cross sections for hot fusion reactions leading to the formation of superheavy elements.
International Nuclear Information System (INIS)
The dynamics of high partonic density QCD is present considering, in the double logarithm approximation, the parton recombination mechanism built in the AGL formalism, developed including unitarity corrections for the nucleon as well for nucleus. It is shown that these corrections are under theoretical control. The resulting non linear evolution in the asymptotic regime and a comprehensive phenomenology concerning Deep Inelastic Scattering F2, FL, F2c.δF2/δIn Q2, δF2A/δIn Q2, etc, is presented. The connection of our formalism with the DGLAP and BFKL dynamics, and with other perturbative (K) and non perturbative (MV-JKLW) approaches is analysed in detail. The phenomena of saturation due to shadowing corrections and the relevance of this effect in ion physics and heavy quark production is emphasized. The implications to e-RHIC, HERA-A, and LHC physics and some open questions are mentioned. (author)
Isopiestic density law of actinide nitrates applied to criticality calculations
International Nuclear Information System (INIS)
Up to now, criticality safety experts used density laws fitted on experimental data and applied them in and outside the measurement range. Depending on the case, such an approach could be wrong for nitrate solutions. Seven components are concerned: UO2(NO3)2, U(NO3)4, Pu(NO3)4, Pu(NO3)3, Th(NO3)4, Am(NO3)3 and HNO3. To get rid of this problem, a new methodology based on the thermodynamic concept of binary electrolytes solutions mixtures at constant water activity, so called 'isopiestic' solutions, has been developed by IRSN to calculate the nitrate solutions density. This article shortly presents the theoretical aspects of the method, its qualification using benchmarks and its implementation in IRSN graphical user interface. (author)
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 cation exchange layer of the bipolar membrane. In steady state these ions are replaced by salt ions transported from the bulk solutions into the transition region by diffusion and migration due to t...
Higgs- and Skyrme-Chern-Simons densities in all dimensions
Tchrakian, D H
2015-01-01
Two types of new Chern-Simons (CS) densities, both defined in all odd and even dimensions, are proposed. These new CS densities feature a scalar field interacting with a scalar. In one case this is a Higgs scalar while in the other it is a Skyrme scalar. The motivation is to study the effects of adding these new CS terms to a Lagrangian which supports static soliton solutions prior to their introduction.
Hadronic density of states from string theory.
Pando Zayas, Leopoldo A; Vaman, Diana
2003-09-12
We present an exact calculation of the finite temperature partition function for the hadronic states corresponding to a Penrose-Güven limit of the Maldacena-Nùñez embedding of the N=1 super Yang-Mills (SYM) into string theory. It is established that the theory exhibits a Hagedorn density of states. We propose a semiclassical string approximation to the finite temperature partition function for confining gauge theories admitting a supergravity dual, by performing an expansion around classical solutions characterized by temporal windings. This semiclassical approximation reveals a hadronic energy density of states of a Hagedorn type, with the coefficient determined by the gauge theory string tension as expected for confining theories. We argue that our proposal captures primarily information about states of pure N=1 SYM theory, given that this semiclassical approximation does not entail a projection onto states of large U(1) charge. PMID:14525414
Hadronic density of states from string theory.
Pando Zayas, Leopoldo A; Vaman, Diana
2003-09-12
We present an exact calculation of the finite temperature partition function for the hadronic states corresponding to a Penrose-Güven limit of the Maldacena-Nùñez embedding of the N=1 super Yang-Mills (SYM) into string theory. It is established that the theory exhibits a Hagedorn density of states. We propose a semiclassical string approximation to the finite temperature partition function for confining gauge theories admitting a supergravity dual, by performing an expansion around classical solutions characterized by temporal windings. This semiclassical approximation reveals a hadronic energy density of states of a Hagedorn type, with the coefficient determined by the gauge theory string tension as expected for confining theories. We argue that our proposal captures primarily information about states of pure N=1 SYM theory, given that this semiclassical approximation does not entail a projection onto states of large U(1) charge.
Nonmetal-metal transition in metal–molten-salt solutions
Silvestrelli, P.-L.; Alavi, A.; Parrinello, M.; Frenkel, D.
1996-01-01
The method of ab initio molecular dynamics, based on finite-temperature density-functional theory, is used to study the nonmetal-metal transition in two different metal–molten-salt solutions, Kx(KCl)1-x and Nax(NaBr)1-x. As the excess metal concentration is increased the electronic density becomes d
Holographic quark-gluon plasmas at finite quark density
Energy Technology Data Exchange (ETDEWEB)
Bigazzi, F. [Dipartimento di Fisica e Astronomia, Universita di Firenze, Sesto Fiorentino (Firenze), Pisa (Italy); INFN, Sezione di Torino (Italy); Cotrone, A. [Dipartimento di Fisica, Universita di Torino (Italy); Mas, J. [Departamento de Fisica de Particulas, Universidade de Santiago de Compostela (Spain); Instituto Galego de Fisica de Altas Enerxias (IGFAE), Santiago de Compostela (Spain); Tarrio, J. [Institute for Theoretical Physics and Spinoza Institute, Universiteit Utrecht, 3584 CE, Utrecht (Netherlands); Mayerson, D. [Institute for Theoretical Physics, University of Amsterdam (Netherlands)
2012-07-15
Gravity solutions holographically dual to strongly coupled quark-gluon plasmas with non-zero quark density are reviewed. They are motivated by the urgency of finding novel tools to explore the phase diagram of QCD-like theories at finite chemical potential. After presenting the solutions and their regime of validity, some of their physical properties are discussed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Complete reconstruction of reduced density matrices
Mazziotti, David A.
2000-08-01
Different from traditional electronic structure methods, the contracted Schrödinger equation with reduced-density-matrix (RDM) reconstruction may be exact when only the 2-particle RDM is employed as the fundamental parameter. Although Rosina's theorem indicates that the 3 and the 4-RDMs are functionals of the 2-RDM, cumulant theory generates only those terms expressible as antisymmetrized products of lower RDMs. We present a formal solution for reconstruction where the approximate cumulant formulas are systematically corrected through contraction conditions. Using a part of the formal 3-RDM reconstruction, the CSE is compared with other methods through a quasi-spin model containing as many as eight-hundred fermions.
Proteins in solution: Fractal surfaces in solutions
Directory of Open Access Journals (Sweden)
R. Tscheliessnig
2016-02-01
Full Text Available The concept of the surface of a protein in solution, as well of the interface between protein and 'bulk solution', is introduced. The experimental technique of small angle X-ray and neutron scattering is introduced and described briefly. Molecular dynamics simulation, as an appropriate computational tool for studying the hydration shell of proteins, is also discussed. The concept of protein surfaces with fractal dimensions is elaborated. We finish by exposing an experimental (using small angle X-ray scattering and a computer simulation case study, which are meant as demonstrations of the possibilities we have at hand for investigating the delicate interfaces that connect (and divide protein molecules and the neighboring electrolyte solution.
Tension density as counter force to the Lorentz force density
Nozaki, Hiroo; Senami, Masato; Ichikawa, Kazuhide; Tachibana, Akitomo
2016-08-01
It is confirmed numerically that the tension density defined in quantum field theory is the counter force to the Lorentz force density. We take benzenedithiol in a nonequilibrium steady state as an example for the numerical demonstration of the balance between these densities. While we use simply a nonequilibrium Green’s function method for a quantum conduction state instead of computations based on quantum field theory, the balance between the tension density and the Lorentz force density can be confirmed. The tension density is free from the relaxation time ansatz and defined as a local quantity. The tension density may give a novel viewpoint to the understanding of the physics of electrical conduction.
Earth's density flattening and hypothesis of latitudinal normal density
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
In this paper, the definition of latitudinal density and density flattening of the level ellipsoid is given, and integral formulas of latitudinal density for pole gravity and equator gravity are derived. According to the pole gravity condition and equator gravity condition for the level ellipsoid, latitudinal density distribution function of the level ellipsoid is obtained. It is proved mathematically that latitudinal density of the earth's equator is larger than that of the pole, the earth's density flat-tening calculated preliminarily is 1/322, and hypothesis of the earth's latitudinal normal density is further proposed, so that theoretical preparation for studying the forming cause of the earth gravity in problems such as continent drift, mantle convection, and submarine extension is made well.
Statistical Complexity in Traveling Densities
Lopez-Ruiz, Ricardo; Sanudo, Jaime
2009-01-01
In this work, we analyze the behavior of statistical complexity in several systems where two identical densities that travel in opposite direction cross each other. The crossing between two Gaussian, rectangular and triangular densities is studied in detail. For these three cases, the shape of the total density presenting an extreme value in complexity is found.
Bone Densitometry (Bone Density Scan)
... of DXA Bone Densitometry? What is a Bone Density Scan (DXA)? Bone density scanning, also called dual-energy x-ray absorptiometry ( ... is today's established standard for measuring bone mineral density (BMD). An x-ray (radiograph) is a noninvasive ...
Solution to manufacturing execution system; MES solution
Energy Technology Data Exchange (ETDEWEB)
Oikawa, H.; Kato, T.; Tanaka, M. [Fuji Electric Co. Ltd., Tokyo (Japan)
2000-05-10
In structuring supply chain management (SCM) in the manufacturing industry, the role of the manufacturing execution system (MES) is very important. In the region of SCM and enterprise resource planning (ERP), even if an optimum system is planned and supply chain planning (SCP) software is actually introduced, only a limited SCM effect can be expected. Fuji Electric has integrated long-cultivated manufacturing know-how into the solution to the MES with an intention to structure manufacturing-field-oriented SCM by linking solutions to SCM, ERP and logistics. (author)
Jin, Zhongming; Li, Cheng; Lin, Yue; Cai, Deng
2014-08-01
Nearest neighbor search is a fundamental problem in various research fields like machine learning, data mining and pattern recognition. Recently, hashing-based approaches, for example, locality sensitive hashing (LSH), are proved to be effective for scalable high dimensional nearest neighbor search. Many hashing algorithms found their theoretic root in random projection. Since these algorithms generate the hash tables (projections) randomly, a large number of hash tables (i.e., long codewords) are required in order to achieve both high precision and recall. To address this limitation, we propose a novel hashing algorithm called density sensitive hashing (DSH) in this paper. DSH can be regarded as an extension of LSH. By exploring the geometric structure of the data, DSH avoids the purely random projections selection and uses those projective functions which best agree with the distribution of the data. Extensive experimental results on real-world data sets have shown that the proposed method achieves better performance compared to the state-of-the-art hashing approaches.
Generating random density matrices
Zyczkowski, Karol; Nechita, Ion; Collins, Benoit
2010-01-01
We study various methods to generate ensembles of quantum density matrices of a fixed size N and analyze the corresponding probability distributions P(x), where x denotes the rescaled eigenvalue, x=N\\lambda. Taking a random pure state of a two-partite system and performing the partial trace over one subsystem one obtains a mixed state represented by a Wishart--like matrix W=GG^{\\dagger}, distributed according to the induced measure and characterized asymptotically, as N -> \\infty, by the Marchenko-Pastur distribution. Superposition of k random maximally entangled states leads to another family of explicitly derived distributions, describing singular values of the sum of k independent random unitaries. Taking a larger system composed of 2s particles, constructing $s$ random bi-partite states, performing the measurement into a product of s-1 maximally entangled states and performing the partial trace over the remaining subsystem we arrive at a random state characterized by the Fuss-Catalan distribution of order...
Carbon nanotube growth density control
Delzeit, Lance D. (Inventor); Schipper, John F. (Inventor)
2010-01-01
Method and system for combined coarse scale control and fine scale control of growth density of a carbon nanotube (CNT) array on a substrate, using a selected electrical field adjacent to a substrate surface for coarse scale density control (by one or more orders of magnitude) and a selected CNT growth temperature range for fine scale density control (by multiplicative factors of less than an order of magnitude) of CNT growth density. Two spaced apart regions on a substrate may have different CNT growth densities and/or may use different feed gases for CNT growth.
High-Throughput ab-initio Dilute Solute Diffusion Database
Wu, Henry; Mayeshiba, Tam; Morgan, Dane
2016-01-01
We demonstrate automated generation of diffusion databases from high-throughput density functional theory (DFT) calculations. A total of more than 230 dilute solute diffusion systems in Mg, Al, Cu, Ni, Pd, and Pt host lattices have been determined using multi-frequency diffusion models. We apply a correction method for solute diffusion in alloys using experimental and simulated values of host self-diffusivity. We find good agreement with experimental solute diffusion data, obtaining a weighte...
Thermospheric density and satellite drag modeling
Mehta, Piyush Mukesh
GRACE satellites. Moving toward accurate atmospheric models and absolute densities requires physics based models for CD. Closed-form solutions of CD have been developed and exist for a handful of simple geometries (flat plate, sphere, and cylinder). However, for complex geometries, the Direct Simulation Monte Carlo (DSMC) method is an important tool for developing CD models. DSMC is computationally intensive and real-time simulations for CD are not feasible. Therefore, parameterized models for CD are required. Modeling CD for an RSO requires knowledge of the gas-surface interaction (GSI) that defines the manner in which the atmospheric particles exchange momentum and energy with the surface. The momentum and energy exchange is further influenced by likely adsorption of atomic oxygen that may partially or completely cover the surface. An important parameter that characterizes the GSI is the energy accommodation coefficient, α. An innovative and state-of-the-art technique of developing parameterized drag coefficient models is presented and validated using the GRACE satellite. The effect of gas-surface interactions on physical drag coefficients is examined. An attempt to reveal the nature of gas-surface interactions at altitudes above 500 km is made using the STELLA satellite. A model that can accurately estimate CD has the potential to: (i) reduce the sources of uncertainty in the drag model, (ii) improve density estimates by resolving time-varying biases and moving toward absolute densities, and (iii) increase data sources for density estimation by allowing for the use of a wide range of RSOs as information sources. Results from this work have the potential to significantly improve the accuracy of conjunction analysis and SSA.
Solutions to Organizational Paradox
DEFF Research Database (Denmark)
Li, Xin; Worm, Verner; Peihong, Xie
Organizations face all kinds of paradoxical problems. There exist various solutions to organizational paradoxes. We develop a typology that lists nine possible logical approaches to understanding the relationship between paradoxical opposites, out of which we identify five types of solutions...... to organizational paradox. Four of the five solutions are explicitly associated with four prominent philosophies. We show the relevance of the five solutions to the real world by applying our scheme to understand different solutions to the generic strategy paradox. Finally, we address the question whether...... there is a superior solution and point out the paradox of paradox resolving, namely, paradoxes cannot be resolved once for all and we have to live with them....
Accurate ab initio spin densities
Boguslawski, Katharina; Legeza, Örs; Reiher, Markus
2012-01-01
We present an approach for the calculation of spin density distributions for molecules that require very large active spaces for a qualitatively correct description of their electronic structure. Our approach is based on the density-matrix renormalization group (DMRG) algorithm to calculate the spin density matrix elements as basic quantity for the spatially resolved spin density distribution. The spin density matrix elements are directly determined from the second-quantized elementary operators optimized by the DMRG algorithm. As an analytic convergence criterion for the spin density distribution, we employ our recently developed sampling-reconstruction scheme [J. Chem. Phys. 2011, 134, 224101] to build an accurate complete-active-space configuration-interaction (CASCI) wave function from the optimized matrix product states. The spin density matrix elements can then also be determined as an expectation value employing the reconstructed wave function expansion. Furthermore, the explicit reconstruction of a CA...
Relativistic Solutions of Anisotropic Compact Objects
Paul, Bikash Chandra
2016-01-01
We present a class of new relativistic solutions with anisotropic fluid for compact stars in hydrostatic equilibrium. The interior space-time geometry considered here for compact objects are described by parameters namely, $\\lambda$, $k$, $A$, $R$ and $n$. The values of the geometrical parameters are determined here for obtaining a class of physically viable stellar models. The energy-density, radial pressure and tangential pressure are finite and positive inside the anisotropic stars. Considering some stars of known mass we present stellar models which describe compact astrophysical objects with nuclear density.
Kargerová, A; Pekař, M
2014-06-15
The densities of hyaluronan solutions in water and 0.15M NaCl were measured in the temperature range from 25 to 50°C for the hyaluronan molecular weights from 10 to 1,750 kDa. The density increased linearly with concentration and decreased with temperature. The data were fitted by the equation describing the density as a linear function of concentration and a quadratic function of temperature. The effect of molecular weight was negligible and thus single equation was sufficient to describe all data. The apparent and partial specific volumes were calculated from the density data including their extrapolated values to infinite dilutions. The measurement of ultrasound speed in the same solutions under the same conditions enabled to calculate the compressibility and its dependence on concentration and temperature. The compressibility decreased with both the concentration and the temperature but the effect of the concentration was only slight mild. The compressibility was used to estimate the hydration numbers which slightly decreased with increasing temperature and concentration. The addition of NaCl changed only the numerical values of density and ultrasound velocity while not changing the character of their dependence on temperature and concentration. Measured and calculated data indicate that hyaluronan does not disturb the specific water structure in the studied concentration range and support the idea of the existence of water clusters or nanodroplets hydrating the hyaluronan chains in solution. PMID:24721101
Synthesis of solid solutions of perovskites
Energy Technology Data Exchange (ETDEWEB)
Dambekalne, M.Y.; Antonova, M.K.; Perro, I.T.; Plaude, A.V.
1986-03-01
The authors carry out thermographic studies, using a derivatograph, in order to understand the nature of the processes taking place during the synthesis of solid solutions of perovskites. Based on the detailed studies on the phase transformations occurring in the charges of the PSN-PMN solid solutions and on the selection of the optimum conditions for carrying out their synthesis, the authors obtained a powder containing a minimum quantity of the undesirable pyrochlore phase and by sintering it using the hot pressing method, they produced single phase ceramic specimens containing the perovskite phase alone with a density close to the theoretical value and showing zero apparent porosity and water absorption.
Generating Solutions to the Einstein - Maxwell Equations
Contopoulos, I G; Kleidis, K; Papadopoulos, D B; Witten, L
2015-01-01
The Einstein-Maxwell (E-M) equations in a curved spacetime that admits at least one Killing vector are derived, from a Lagrangian density adapted to symmetries. In this context, an auxiliary space of potentials is introduced, in which, the set of potentials associated to an original (seed) solution of the E-M equations are transformed to a new set, either by continuous transformations or by discrete transformations. In this article, continuous transformations are considered. Accordingly, originating from the so-called $\\gamma_A$-metric, other exact solutions to the E-M equations are recovered and discussed.
Comparison of density determination of liquid samples by density meters
Buchner, C.; Wolf, H.; Vámossy, C.; Lorefice, S.; Lenard, E.; Spohr, I.; Mares, G.; Perkin, M.; Parlic-Risovic, T.; Grue, L.-L.; Tammik, K.; van Andel, I.; Zelenka, Z.
2016-01-01
Hydrostatic density determinations of liquids as reference material are mainly performed by National Metrology Institutes to provide means for calibrating or checking liquid density measuring instruments such as oscillation-type density meters. These density meters are used by most of the metrology institutes for their calibration and scientific work. The aim of this project was to compare the results of the liquid density determination by oscillating density meters of the participating laboratories. The results were linked to CCM.D.K-2 partly via Project EURAMET.M.D.K-2 (1019) "Comparison of liquid density standards" by hydrostatic weighing piloted by BEV in 2008. In this comparison pentadecane, water and of oil with a high viscosity were measured at atmospheric pressure using oscillation type density meter. The temperature range was from 15 °C to 40 °C. The measurement results were in some cases discrepant. Further studies, comparisons are essential to explore the capability and uncertainty of the density meters Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
Counting solutions from finite samplings.
Huang, Haiping; Zhou, Haijun
2012-02-01
We formulate the solution counting problem within the framework of the inverse Ising problem and use fast belief propagation equations to estimate the entropy whose value provides an estimate of the true one. We test this idea on both diluted models [random 2-SAT (2-satisfiability) and 3-SAT problems] and a fully connected model (binary perceptron), and show that when the constraint density is small, this estimate can be very close to the true value. The information stored by the salamander retina under the natural movie stimuli can also be estimated, and our result is consistent with that obtained by the Monte Carlo method. Of particular significance is that the sizes of other metastable states for this real neuronal network are predicted. PMID:22463290
Polymer density functional approach to efficient evaluation of path integrals
DEFF Research Database (Denmark)
Brukhno, Andrey; Vorontsov-Velyaminov, Pavel N.; Bohr, Henrik
2005-01-01
A polymer density functional theory (P-DFT) has been extended to the case of quantum statistics within the framework of Feynman path integrals. We start with the exact P-DFT formalism for an ideal open chain and adapt its efficient numerical solution to the case of a ring. We show that, similarly...
Institute of Scientific and Technical Information of China (English)
Li Mo; Fei Yuan; Jian Yang
2011-01-01
In this paper, we give an overview of mobile backhaul solutions and propose an MPLS-centered solution that takes intoaccount timing synchronization, OAM, and protection： We also propose an evolved protection bandwidth allocation mechanism that makes the transport network as efficient as possible.
Another exact inflationary solution
Kruger, A T; Kruger, Adam T.; Norbury, John W.
2000-01-01
A new closed-form inflationary solution is given for a hyperbolic interaction potential. The method used to arrive at this solution is outlined as it appears possible to generate additional sets of equations which satisfy the model. In addition a new form of decaying cosmological constant is presented.
Solution structure of (+)-discodermolide.
Smith, A B; LaMarche, M J; Falcone-Hindley, M
2001-03-01
[structure: see text]. The solution structure of (+)-discodermolide (1) has been determined via 1- and 2-D NMR techniques in conjunction with Monte Carlo conformational analysis. Taken together, the results demonstrate that in solution (+)-discodermolide occupies a helical conformation remarkably similar to the solid state conformation.
Probabilistic solution of relative entropy weighted control
Bierkens, Joris
2012-01-01
We show that stochastic control problems with a particular cost structure involving a relative entropy term admit a purely probabilistic solution, without the necessity of applying the dynamic programming principle. The argument is as follows. Minimization of the expectation of a random variable with respect to the underlying probability measure, penalized by relative entropy, may be solved exactly. In the case where the randomness is generated by a standard Brownian motion, this exact solution can be written as a Girsanov density. The stochastic process appearing in the Girsanov exponent has the role of control process, and the relative entropy of the change of probability measure is equal to the integral of the square of this process. An explicit expression for the control process may be obtained in terms of the Malliavin derivative of the density process. The theory is applied to the problem of minimizing the maximum of a Brownian motion (penalized by the relative entropy), leading to an explicit expressio...
Neace, James C.
1986-01-01
Process for removing diluent degradation products from a solvent extraction solution, which has been used to recover uranium and plutonium from spent nuclear fuel. A wash solution and the solvent extraction solution are combined. The wash solution contains (a) water and (b) up to about, and including, 50 volume percent of at least one-polar water-miscible organic solvent based on the total volume of the water and the highly-polar organic solvent. The wash solution also preferably contains at least one inorganic salt. The diluent degradation products dissolve in the highly-polar organic solvent and the organic solvent extraction solvent do not dissolve in the highly-polar organic solvent. The highly-polar organic solvent and the extraction solvent are separated.
Trajectory probability hypothesis density filter
García-Fernández, Ángel F.; Svensson, Lennart
2016-01-01
This paper presents the probability hypothesis density (PHD) filter for sets of trajectories. The resulting filter, which is referred to as trajectory probability density filter (TPHD), is capable of estimating trajectories in a principled way without requiring to evaluate all measurement-to-target association hypotheses. As the PHD filter, the TPHD filter is based on recursively obtaining the best Poisson approximation to the multitrajectory filtering density in the sense of minimising the K...
The Estimation of Conditional Densities
Xiaohong Chen; Oliver Linton; Robinson, Peter M.
2001-01-01
We discuss a number of issues in the smoothed nonparametric estimation of kernel conditional probability density functions for stationary processes. The kernel conditional density estimate is a ratio of joint and marginal density estimates. We point out the different implications of leading choices of bandwidths in numerator and denominator for the ability of the estimate to integrate to one and to have finite moments. Again bearing in mind different bandwidth possibilities, we discuss asympt...
High-density fiber optic biosensor arrays
Epstein, Jason R.; Walt, David R.
2002-02-01
Novel approaches are required to coordinate the immense amounts of information derived from diverse genomes. This concept has influenced the expanded role of high-throughput DNA detection and analysis in the biological sciences. A high-density fiber optic DNA biosensor was developed consisting of oligonucleotide-functionalized, 3.1 mm diameter microspheres deposited into the etched wells on the distal face of a 500 micrometers imaging fiber bundle. Imaging fiber bundles containing thousands of optical fibers, each associated with a unique oligonucleotide probe sequence, were the foundation for an optically connected, individually addressable DNA detection platform. Different oligonucleotide-functionalized microspheres were combined in a stock solution, and randomly dispersed into the etched wells. Microsphere positions were registered from optical dyes incorporated onto the microspheres. The distribution process provided an inherent redundancy that increases the signal-to-noise ratio as the square root of the number of sensors examined. The representative amount of each probe-type in the array was dependent on their initial stock solution concentration, and as other sequences of interest arise, new microsphere elements can be added to arrays without altering the existing detection capabilities. The oligonucleotide probe sequences hybridize to fluorescently-labeled, complementary DNA target solutions. Fiber optic DNA microarray research has included DNA-protein interaction profiles, microbial strain differentiation, non-labeled target interrogation with molecular beacons, and single cell-based assays. This biosensor array is proficient in DNA detection linked to specific disease states, single nucleotide polymorphism (SNP's) discrimination, and gene expression analysis. This array platform permits multiple detection formats, provides smaller feature sizes, and enables sensor design flexibility. High-density fiber optic microarray biosensors provide a fast
Density Estimation with Mercer Kernels
Macready, William G.
2003-01-01
We present a new method for density estimation based on Mercer kernels. The density estimate can be understood as the density induced on a data manifold by a mixture of Gaussians fit in a feature space. As is usual, the feature space and data manifold are defined with any suitable positive-definite kernel function. We modify the standard EM algorithm for mixtures of Gaussians to infer the parameters of the density. One benefit of the approach is it's conceptual simplicity, and uniform applicability over many different types of data. Preliminary results are presented for a number of simple problems.
Berghauser Pont, M.Y.; Haupt, P.A.
2009-01-01
The concentration of humans – in some cases judged as too high, in others not high enough – and the problems connected to this, have resulted in discussions on density. Prior to the 20th century, density in European cities was merely an outcome of complex circumstances. During the second half of the 19th century, high densities in industrializing cities were argued to be one of the major causes of fires, diseases and social turmoil. In this period, density was introduced as a tool to analyse ...
Canonical density matrix perturbation theory.
Niklasson, Anders M N; Cawkwell, M J; Rubensson, Emanuel H; Rudberg, Elias
2015-12-01
Density matrix perturbation theory [Niklasson and Challacombe, Phys. Rev. Lett. 92, 193001 (2004)] is generalized to canonical (NVT) free-energy ensembles in tight-binding, Hartree-Fock, or Kohn-Sham density-functional theory. The canonical density matrix perturbation theory can be used to calculate temperature-dependent response properties from the coupled perturbed self-consistent field equations as in density-functional perturbation theory. The method is well suited to take advantage of sparse matrix algebra to achieve linear scaling complexity in the computational cost as a function of system size for sufficiently large nonmetallic materials and metals at high temperatures. PMID:26764847
Spin density matrices for nuclear density functionals with parity violations
Barrett, B R
2010-01-01
The spin density matrix (SDM) used in atomic and molecular physics is revisited for nuclear physics, in the context of the radial density functional theory. The vector part of the SDM defines a "hedgehog" situation, which exists only if nuclear states contain some amount of parity violation.
Current density and state density in diluted magnetic semiconductor nanostructures
Pérez Merchancano, S. T.; Paredes Gutiérrez, H.; Zuñiga, J. A.
2016-02-01
We study in this paper the spin-polarized current density components in diluted magnetic semiconductor tunnelling diodes with different sample geometries. We calculate the resonant JxV and the density of states. The differential conductance curves are analyzed as functions of the applied voltage and the magnetic potential strength induced by the magnetic ions.
SIPPI: A Matlab toolbox for sampling the solution to inverse problems with complex prior information
DEFF Research Database (Denmark)
Hansen, Thomas Mejer; Cordua, Knud Skou; Caroline Looms, Majken;
2013-01-01
on the solution. The combined states of information (i.e. the solution to the inverse problem) is a probability density function typically referred to as the a posteriori probability density function. We present a generic toolbox for Matlab and Gnu Octave called SIPPI that implements a number of methods...
Regularized Regression and Density Estimation based on Optimal Transport
Burger, M.
2012-03-11
The aim of this paper is to investigate a novel nonparametric approach for estimating and smoothing density functions as well as probability densities from discrete samples based on a variational regularization method with the Wasserstein metric as a data fidelity. The approach allows a unified treatment of discrete and continuous probability measures and is hence attractive for various tasks. In particular, the variational model for special regularization functionals yields a natural method for estimating densities and for preserving edges in the case of total variation regularization. In order to compute solutions of the variational problems, a regularized optimal transport problem needs to be solved, for which we discuss several formulations and provide a detailed analysis. Moreover, we compute special self-similar solutions for standard regularization functionals and we discuss several computational approaches and results. © 2012 The Author(s).
High density operation for reactor-relevant power exhaust
Wischmeier, M.
2015-08-01
With increasing size of a tokamak device and associated fusion power gain an increasing power flux density towards the divertor needs to be handled. A solution for handling this power flux is crucial for a safe and economic operation. Using purely geometric arguments in an ITER-like divertor this power flux can be reduced by approximately a factor 100. Based on a conservative extrapolation of current technology for an integrated engineering approach to remove power deposited on plasma facing components a further reduction of the power flux density via volumetric processes in the plasma by up to a factor of 50 is required. Our current ability to interpret existing power exhaust scenarios using numerical transport codes is analyzed and an operational scenario as a potential solution for ITER like divertors under high density and highly radiating reactor-relevant conditions is presented. Alternative concepts for risk mitigation as well as strategies for moving forward are outlined.
A molecular density functional theory to study solvation in water
Jeanmairet, Guillaume
2014-01-01
A classical density functional theory is applied to study solvation of solutes in water. An approx- imate form of the excess functional is proposed for water. This functional requires the knowledge of pure solvent direct correlation functions. Those functions can be computed by using molecular simulations such as molecular dynamic or Monte Carlo. It is also possible to use functions that have been determined experimentally. The functional minimization gives access to the solvation free energy and to the equilibrium solvent density. Some correction to the functional are also proposed to get the proper tetrahedral order of solvent molecules around a charged solute and to reproduce the correct long range hydrophobic behavior of big apolar solutes. To proceed the numerical minimization of the functional, the theory has been discretized on two tridimensional grids, one for the space coordinates, the other for the angular coordinates, in a functional minimization code written in modern Fortran, mdft. This program i...
Institute of Scientific and Technical Information of China (English)
戴天奇; 姚世卫; 魏志国
2015-01-01
海上浮动核电站温排水会导致停泊水域温度升高，研究其稀释扩散规律并适当控制排放水域温度对于防止环境水体热污染具有重要意义。本文将温排水排放过程简化为横流环境中的热射流过程进行数值模拟。在有限体积法的基础上，采用 SIMPLE 算法和 Realizable k-ε湍流模型建立了热射流浮升过程的三维数学模型，并基于已有文献实验数据，验证了该模型的准确性。分析了环境流速和排放口角度对温排水热影响范围和程度的作用规律。结果显示：环境流速较大时，对流换热剧烈，排放角度对温排水影响范围较小；环境流速较小时，来流的冲刷作用减弱，排放角度对温排水的影响范围较大；相同工况下，在垂直流向平面上排放角度的变化对中心温度沿流向分布影响较小，而在平行流向平面上排放角度的变化对中心温度分布的影响较大，且环境流速对于中心温度沿流向分布影响较小。%The waste heat emissions of thermal discharge from floating nuclear power plants may have a negative thermal effect on the environment.Investigation on the buoyant and diffusion rules of thermal dis-charge from floating nuclear power plants and properly controlling the discharging temperature have great significance for seat water thermal pollution prevention.This paper simplified the thermal discharge process as thermal jet in cross flow to establish the 3D mathematic model for thermal jets floating process, on the basis of finite volume method and using the SIMPLE algorithm and Realizable k-εturbulence model. Then this model was verified by using the experimental data from reference[5 ].The thermal effect range and degree of environmental velocity and discharge angle on thermal discharge were investigated.The re-sults show that,at high ambient velocities,the convection heat transfer was intense so that the heat-affect-ed zone was influenced
Mammography density estimation with automated volumetic breast density measurement
Energy Technology Data Exchange (ETDEWEB)
Ko, Su Yeon; Kim, Eun Kyung; Kim, Min Jung; Moon, Hee Jung [Dept. of Radiology, Severance Hospital, Research Institute of Radiological Science, Yonsei University College of Medicine, Seoul (Korea, Republic of)
2014-06-15
To compare automated volumetric breast density measurement (VBDM) with radiologists' evaluations based on the Breast Imaging Reporting and Data System (BI-RADS), and to identify the factors associated with technical failure of VBDM. In this study, 1129 women aged 19-82 years who underwent mammography from December 2011 to January 2012 were included. Breast density evaluations by radiologists based on BI-RADS and by VBDM (Volpara Version 1.5.1) were compared. The agreement in interpreting breast density between radiologists and VBDM was determined based on four density grades (D1, D2, D3, and D4) and a binary classification of fatty (D1-2) vs. dense (D3-4) breast using kappa statistics. The association between technical failure of VBDM and patient age, total breast volume, fibroglandular tissue volume, history of partial mastectomy, the frequency of mass > 3 cm, and breast density was analyzed. The agreement between breast density evaluations by radiologists and VBDM was fair (k value = 0.26) when the four density grades (D1/D2/D3/D4) were used and moderate (k value = 0.47) for the binary classification (D1-2/D3-4). Twenty-seven women (2.4%) showed failure of VBDM. Small total breast volume, history of partial mastectomy, and high breast density were significantly associated with technical failure of VBDM (p 0.001 to 0.015). There is fair or moderate agreement in breast density evaluation between radiologists and VBDM. Technical failure of VBDM may be related to small total breast volume, a history of partial mastectomy, and high breast density.
Conduction heat transfer solutions
International Nuclear Information System (INIS)
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. This material is useful for engineers, scientists, technologists, and designers of all disciplines, particularly those who design thermal systems or estimate temperatures and heat transfer rates in structures. More than 500 problem solutions and relevant data are tabulated for easy retrieval. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. A case number is assigned to each problem for cross-referencing, and also for future reference. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. At least one source reference is given so that the user can review the methods used to derive the solutions. Problem solutions are given in the form of equations, graphs, and tables of data, all of which are also identified by problem case numbers and source references
Seepold, Ralf E D; Madrid, Natividad Martinez
2011-01-01
Embedded systems have an increasing importance in our everyday lives. The growing complexity of embedded systems and the emerging trend to interconnections between them lead to new challenges. Intelligent solutions are necessary to overcome these challenges and to provide reliable and secure systems to the customer under a strict time and financial budget. ""Solutions on Embedded Systems"" documents results of several innovative approaches that provide intelligent solutions in embedded systems. The objective is to present mature approaches, to provide detailed information on the implementation
Dissipative cosmological solutions
Chimento, Luis P.; Jakubi, Alejandro S.
1997-01-01
The exact general solution to the Einstein equations in a homogeneous Universe with a full causal viscous fluid source for the bulk viscosity index $m=1/2$ is found. We have investigated the asymptotic stability of Friedmann and de Sitter solutions, the former is stable for $m\\ge 1/2$ and the latter for $m\\le 1/2$. The comparison with results of the truncated theory is made. For $m=1/2$, it was found that families of solutions with extrema no longer remain in the full case, and they are repla...
Lublinsky, Boris; Yakubovich, Alexey
2013-01-01
The go-to guidebook for deploying Big Data solutions with Hadoop Today's enterprise architects need to understand how the Hadoop frameworks and APIs fit together, and how they can be integrated to deliver real-world solutions. This book is a practical, detailed guide to building and implementing those solutions, with code-level instruction in the popular Wrox tradition. It covers storing data with HDFS and Hbase, processing data with MapReduce, and automating data processing with Oozie. Hadoop security, running Hadoop with Amazon Web Services, best practices, and automating Hadoop processes i
Slightly Two or Three Dimensional Self-Similar Solutions
Sari, Re'em; Yalinewich, Almog; MacFadyen, Andrew
2011-01-01
Self similarity allows for analytic or semi-analytic solutions to many hydrodynamics problems. Most of these solutions are one dimensional. Using linear perturbation theory, expanded around such a one-dimensional solution, we find self-similar hydrodynamic solutions that are two- or three-dimensional. Since the deviation from a one-dimensional solution is small, we call these slightly two-dimensional and slightly three-dimensional self-similar solutions, respectively. As an example, we treat strong spherical explosions of the second type. A strong explosion propagates into an ideal gas with negligible temperature and density profile of the form rho(r,theta,phi)=r^{-omega}[1+sigma*F(theta,phi)], where omega>3 and sigma << 1. Analytical solutions are obtained by expanding the arbitrary function F(theta,phi) in spherical harmonics. We compare our results with two dimensional numerical simulations, and find good agreement.
Solution to enterprise resource planning; ERP solution
Energy Technology Data Exchange (ETDEWEB)
Suzuki, M.; Okajima, E. [Fuji Electric Co. Ltd., Tokyo (Japan)
2000-05-10
The environment around enterprises has greatly changed in sluggish Japanese economy since the bubble burst. To make the total enterprise activity efficient and speedy and to flexibly meet changes in enterprise environments and diversified customer needs, enterprises are planning to shift the existing methods to enterprise resource planning (ERP) as the infrastructure of strategic enterprise management. This paper describes the solution to ERP which is package software for the key system, the core of enterprise basic business, and also an application example, giving guideline for restructuring the basic business. (author)
Continuous Dependence on the Density for Stratified Steady Water Waves
Chen, Robin Ming; Walsh, Samuel
2016-02-01
There are two distinct regimes commonly used to model traveling waves in stratified water: continuous stratification, where the density is smooth throughout the fluid, and layer-wise continuous stratification, where the fluid consists of multiple immiscible strata. The former is the more physically accurate description, but the latter is frequently more amenable to analysis and computation. By the conservation of mass, the density is constant along the streamlines of the flow; the stratification can therefore be specified by prescribing the value of the density on each streamline. We call this the streamline density function. Our main result states that, for every smoothly stratified periodic traveling wave in a certain small-amplitude regime, there is an L ∞ neighborhood of its streamline density function such that, for any piecewise smooth streamline density function in that neighborhood, there is a corresponding traveling wave solution. Moreover, the mapping from streamline density function to wave is Lipschitz continuous in a certain function space framework. As this neighborhood includes piecewise smooth densities with arbitrarily many jump discontinues, this theorem provides a rigorous justification for the ubiquitous practice of approximating a smoothly stratified wave by a layered one. We also discuss some applications of this result to the study of the qualitative features of such waves.
Genetic determinants of mammographic density
International Nuclear Information System (INIS)
Changes in breast density are highly correlated with steroid hormone exposure. In a cross-sectional study of 396 Caucasian and African-American women, we evaluated whether polymorphisms in genes involved in steroid hormone biosynthesis and metabolism, CYP17 (T27C), COMT (Val158Met), 17HSDB1 (Ser312Gly) and 3HSDB1 (Asn367Thr), predict mammographic density. We also evaluated whether associations vary by menopausal and hormone replacement therapy status. We found no strong consistent relationships between polymorphisms in these genes and breast density. African-American women homozygous for the Thr allele of 3HSDB1 had increased density (the absolute difference versus the Asn/Asn genotype was +19.7%; P trend = 0.02), while Caucasian homozygous women had decreased density (-5.1%; P trend = 0.04). Among premenopausal women, carriers of the Ser allele had (not significantly) greater density (versus Gly/Gly genotype: +7.1%; P trend = 0.07). In addition, among current users of hormone replacement therapy, we observed that women with the low-activity Met/Met genotype of COMT had greater breast density (versus the Val/Val genotype: +11.7%; P trend = 0.01). Additional large studies evaluating these and other candidate breast cancer genes will be required to determine what proportion, if any, of the interindividual differences in breast density are due to underlying genetic variation in genes involved in steroid hormone biosynthesis or metabolism
Soliton-like solution in quantum electrodynamics
Skoromnik, O D; Keitel, C H
2016-01-01
A novel soliton-like solution in quantum electrodynamics is obtained via a self-consistent field method. By writing the Hamiltonian of quantum electrodynamics in the Coulomb gauge, we separate out a classical component in the density operator of the electron-positron field. Then, by modeling the state vector in analogy with the theory of superconductivity, we minimize the functional for the energy of the system. This results in the equations of the self-consistent field, where the solutions are associated with the collective excitation of the electron-positron field---the soliton-like solution. In addition, the canonical transformation of the variables allowed us to separate out the total momentum of the system and, consequently, to find the relativistic energy dispersion relation for the moving soliton.
The Conductivity of Solutions.
Rayner-Canham, Geoff
1993-01-01
Presents historical background and modern explanations for the popular demonstration of showing conductivity of solutions through the insertion of a light-bulb conductivity tester into deionized water and water with salt in it. (PR)
Convergent Aeronautics Solutions Project
National Aeronautics and Space Administration — The Convergent Aeronautics Solutions (CAS) Project uses short-duration activities to establish early-stage concept and technology feasibility for high-potential...
Cromolyn Sodium Nasal Solution
... is sometimes prescribed for other uses; ask your doctor or pharmacist for more information. ... the instructions provided with the solution. Ask your doctor, pharmacist, or respiratory therapist to demonstrate the proper technique. ...
TUTUNEA MIHAELA FILOFTEIA
2012-01-01
The integration of activities, the business processes as well as their optimization, bring the perspective of profitable growth and create significant and competitive advantages in any company. The adoption of some ERP integrated software solutions, from SMEs’ perspective, must be considered as a very important management decision in medium and long term. ERP solutions, along with the transparent and optimized management of all internal processes, also offer an...
Conduction heat transfer solutions
International Nuclear Information System (INIS)
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs
Determining the Limiting Current Density of Vanadium Redox Flow Batteries
Directory of Open Access Journals (Sweden)
Jen-Yu Chen
2014-09-01
Full Text Available All-vanadium redox flow batteries (VRFBs are used as energy storage systems for intermittent renewable power sources. The performance of VRFBs depends on materials of key components and operating conditions, such as current density, electrolyte flow rate and electrolyte composition. Mass transfer overpotential is affected by the electrolyte flow rate and electrolyte composition, which is related to the limiting current density. In order to investigate the effect of operating conditions on mass transport overpotential, this study established a relationship between the limiting current density and operating conditions. First, electrolyte solutions with different states of charge were prepared and used for a single cell to obtain discharging polarization curves under various operating conditions. The experimental results were then analyzed and are discussed in this paper. Finally, this paper proposes a limiting current density as a function of operating conditions. The result helps predict the effect of operating condition on the cell performance in a mathematical model.
Energy density and spatial curvature in general relativity
Energy Technology Data Exchange (ETDEWEB)
Frankel, T.; Galloway, G.J.
1981-04-01
Positive energy density tends to limit the size of space. This effect is studied within several contexts. We obtain sufficient conditions (which involve the energy density in a crucial way) for the compactness of spatial hypersurfaces in space-time. We then obtain some results concerning static or, more generally, stationary space-times. The Schwarzchild solution puts an upper bound on the size of a static spherically symmetric fluid with density bounded from below. We derive a result of roughly the same nature which, however, requires no symmetry and allows for rotation. Also, we show that static or rotating universes with L = 0 require that the density along some spatial geodesic must fall off rapidly with distance from a point.
Fluctuations around Periodic BPS-Density Waves in the Calogero Model
Bardek, V; Meljanac, S
2010-01-01
The collective field formulation of the Calogero model supports periodic density waves. An important set of such density waves is a two-parameter family of BPS solutions of the equations of motion of the collective field theory. One of these parameters is essentially the average particle density, which determines the period, while the other parameter determines the amplitude. These BPS solutions are sometimes referred to as "small amplitude waves" since they undulate around their mean density, but never vanish. We present complete analysis of quadratic fluctuations around these BPS solutions. The corresponding fluctuation hamiltonian (i.e., the stability operator) is diagonalized in terms of bosonic creation and annihilation operators which correspond to the complete orthogonal set of Bloch-Floquet eigenstates of a related periodic Schr\\"odinger hamiltonian, which we derive explicitly. Remarkably, the fluctuation spectrum is independent of the parameter which determines the density wave's amplitude. As a cons...
Energy Technology Data Exchange (ETDEWEB)
Strom, I.; Joosten, L.; Boonstra, C. [DHV Sustainability Consultants, Eindhoiven (Netherlands)
2006-05-15
PEP stands for 'Promotion of European Passive Houses' and is a consortium of European partners, supported by the European Commission, Directorate General for Energy and Transport. In this working paper an overview is given of Passive House solutions. An inventory has been made of Passive House solutions for new build residences applied in each country. Based on this, the most common basic solutions have been identified and described in further detail, including the extent to which solutions are applied in common and best practice and expected barriers for the implementation in each country. An inventory per country is included in the appendix. The analysis of Passive House solutions in partner countries shows high priority with regard to the performance of the thermal envelope, such as high insulation of walls, roofs, floors and windows/ doors, thermal bridge-free construction and air tightness. Due to the required air tightness, special attention must be paid to indoor air quality through proper ventilation. Finally, efficient ((semi-)solar) heating systems for combined space and DHW heating still require a significant amount of attention in most partner countries. Other basic Passive House solutions show a smaller discrepancy with common practice and fewer barriers have been encountered in partner countries. In the next section, the general barriers in partner countries have been inventoried. For each type of barrier a suggested approach has been given. Most frequently encountered barriers in partner countries are: limited know-how; limited contractor skills; and acceptation of Passive Houses in the market. Based on the suggested approaches to overcoming barriers, this means that a great deal of attention must be paid to providing practical information and solutions to building professionals, providing practical training to installers and contractors and communication about the Passive House concept to the market.
Derivation of the Fick's Law for the Lorentz Model in a low density regime
Basile, Giada; Nota, Alessia; Pezzotti, Federica; Pulvirenti, Mario
2014-01-01
We consider the Lorentz model in a slab with two mass reservoirs at the boundaries. We show that, in a low density regime, there exists a unique stationary solution for the microscopic dynamics which converges to the stationary solution of the heat equation, namely to the linear profile of the density. In the same regime the macroscopic current in the stationary state is given by the Fick's law, with the diffusion coefficient determined by the Green-Kubo formula.
Derivation of the Fick's Law for the Lorentz Model in a Low Density Regime
Basile, G.; Nota, A.; Pezzotti, F.; Pulvirenti, M.
2015-06-01
We consider the Lorentz model in a slab with two mass reservoirs at the boundaries. We show that, in a low density regime, there exists a unique stationary solution for the microscopic dynamics, which converges to the stationary solution of the heat equation, namely to the linear profile of the density. In the same regime, the macroscopic current in the stationary state is given by the Fick's law, with the diffusion coefficient determined by the Green-Kubo formula.
Charge density waves in solids
Gor'kov, LP
2012-01-01
The latest addition to this series covers a field which is commonly referred to as charge density wave dynamics.The most thoroughly investigated materials are inorganic linear chain compounds with highly anisotropic electronic properties. The volume opens with an examination of their structural properties and the essential features which allow charge density waves to develop.The behaviour of the charge density waves, where interesting phenomena are observed, is treated both from a theoretical and an experimental standpoint. The role of impurities in statics and dynamics is considered and an
Matching of Stephani and de Sitter solutions on the hypersurface of constant time
Korkina, M P
2013-01-01
The spherically symmetric solution for perfect fluid with homogeneous density and inhomogeneous pressure has been considered. This solution is known as Stephani solution. The matching of this solution and de Sitter solution has been done on a hypersurface of constant time. The matching has been done for general case and for particular cases (flat, closed, open universe). An equality of the densities and a bound of the pressures have been shown on the matching hypersurface. Also, restrictions on some arbitrary functions have been found.
High-cell-density cultivation of microorganisms.
Riesenberg, D; Guthke, R
1999-04-01
High-cell-density cultivation (HCDC) is required to improve microbial biomass and product formation substantially. An overview of HCDC is given for microorganisms including bacteria, archae and eukarya (yeasts). Problems encountered by HCDC and their possible solutions are discussed. Improvements of strains, different types of bioreactors and cultivation strategies for successful HCDC are described. Stirred-tank reactors with and without cell retention, a dialysis-membrane reactor, a gas-lift reactor and a membrane cyclone reactor used for HCDC are outlined. Recently modified traditional feeding strategies and new ones are included, in particular those for unlimited growth to very dense cultures. Emphasis is placed on robust fermentation control because of the growing industrial interest in this field. Therefore, developments in the application of multivariate statistical control, artificial neural networks, fuzzy control and knowledge-based supervision (expert systems) are summarized. Recent advances using Escherichia coli--the pioneer organism for HCDC--are outlined. PMID:10341426
Low density bismaleimide-carbon microballoon composites
Kourtides, D. A.; Parker, J. A. (Inventor)
1979-01-01
A process is described for the preparation of composite laminate.structures of glass cloth preimpregnated with polybismaleimide resin and adhered to a polybismaleimide glass or aromatic polyamide paper honeycomb cell structure that is filled or partially filled with a syntactic foam consisting of a mixture of bismaleimide resin and carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic microballoons and subsequently bonded using a 2% bismaleimide solution. The laminate structures are cured for two hours at 477 deg K and are adhered to the honeycomb bismaleimide adhesive using a pressure of 700 KN/sq m pressure at 450 deg K. The laminate composite is then post-cured for two hours at 527 deg K to produce a composite laminate having a density in the range from about 95 kilograms per cubic meter to 130 kilograms per cubic meter.
On Axisymmetric and Stationary Solutions of the Self-Gravitating Vlasov System
Ames, Ellery; Logg, Anders
2016-01-01
Axisymmetric and stationary solutions are constructed to the Einstein--Vlasov and Vlasov--Poisson systems. These solutions are constructed numerically, using finite element methods and a fixed-point iteration in which the total mass is fixed at each step. A variety of axisymmetric stationary solutions are exhibited, including solutions with toroidal, disk-like, spindle-like, and composite spatial density configurations, as are solutions with non-vanishing net angular momentum. In the case of toroidal solutions, we show for the first time, solutions of the Einstein--Vlasov system which contain ergoregions.
On axisymmetric and stationary solutions of the self-gravitating Vlasov system
Ames, Ellery; Andréasson, Håkan; Logg, Anders
2016-08-01
Axisymmetric and stationary solutions are constructed to the Einstein-Vlasov and Vlasov-Poisson systems. These solutions are constructed numerically, using finite element methods and a fixed-point iteration in which the total mass is fixed at each step. A variety of axisymmetric stationary solutions are exhibited, including solutions with toroidal, disk-like, spindle-like, and composite spatial density configurations, as are solutions with non-vanishing net angular momentum. In the case of toroidal solutions, we show for the first time, solutions of the Einstein-Vlasov system which contain ergoregions.
Analytical solutions for Tokamak equilibria with reversed toroidal current
Energy Technology Data Exchange (ETDEWEB)
Martins, Caroline G. L.; Roberto, M.; Braga, F. L. [Departamento de Fisica, Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, Sao Paulo 12228-900 (Brazil); Caldas, I. L. [Instituto de Fisica, Universidade de Sao Paulo, 05315-970 Sao Paulo, SP (Brazil)
2011-08-15
In tokamaks, an advanced plasma confinement regime has been investigated with a central hollow electric current with negative density which gives rise to non-nested magnetic surfaces. We present analytical solutions for the magnetohydrodynamic equilibria of this regime in terms of non-orthogonal toroidal polar coordinates. These solutions are obtained for large aspect ratio tokamaks and they are valid for any kind of reversed hollow current density profiles. The zero order solution of the poloidal magnetic flux function describes nested toroidal magnetic surfaces with a magnetic axis displaced due to the toroidal geometry. The first order correction introduces a poloidal field asymmetry and, consequently, magnetic islands arise around the zero order surface with null poloidal magnetic flux gradient. An analytic expression for the magnetic island width is deduced in terms of the equilibrium parameters. We give examples of the equilibrium plasma profiles and islands obtained for a class of current density profile.
Density functionals from deep learning
McMahon, Jeffrey M
2016-01-01
Density-functional theory is a formally exact description of a many-body quantum system in terms of its density; in practice, however, approximations to the universal density functional are required. In this work, a model based on deep learning is developed to approximate this functional. Deep learning allows computational models that are capable of naturally discovering intricate structure in large and/or high-dimensional data sets, with multiple levels of abstraction. As no assumptions are made as to the form of this structure, this approach is much more powerful and flexible than traditional approaches. As an example application, the model is shown to perform well on approximating the kinetic-energy density functional for noninteracting electrons. The model is analyzed in detail, and its advantages over conventional machine learning are discussed.
High Energy Density Capacitors Project
National Aeronautics and Space Administration — NASA?s future space science missions cannot be realized without the state of the art energy storage devices which require high energy density, high reliability, and...
Institute of Scientific and Technical Information of China (English)
史定华; 徐洪; 等
2002-01-01
For a repairable redundant system consisting of two same components with exponential lifetime and general repair time distribution,the probability densities of the system in some state at time t were determined by a group of ordinary and partial differential equations,called density evolution equations.It was proved that the time-dependent solution of the density evolution equations uniquely exists and strongly converges to its steady state density solution by a semi-group method.In this proof,it is not necessary to suppose that the repair rate function is bounded.The technique of the proof is valuable for many density evolution equatons.
Haspot, Boris
2016-06-01
We consider the compressible Navier-Stokes equations for viscous and barotropic fluids with density dependent viscosity. The aim is to investigate mathematical properties of solutions of the Navier-Stokes equations using solutions of the pressureless Navier-Stokes equations, that we call quasi solutions. This regime corresponds to the limit of highly compressible flows. In this paper we are interested in proving the announced result in Haspot (Proceedings of the 14th international conference on hyperbolic problems held in Padova, pp 667-674, 2014) concerning the existence of global weak solution for the quasi-solutions, we also observe that for some choice of initial data (irrotationnal) the quasi solutions verify the porous media, the heat equation or the fast diffusion equations in function of the structure of the viscosity coefficients. In particular it implies that it exists classical quasi-solutions in the sense that they are {C^{∞}} on {(0,T)× {R}N} for any {T > 0}. Finally we show the convergence of the global weak solution of compressible Navier-Stokes equations to the quasi solutions in the case of a vanishing pressure limit process. In particular for highly compressible equations the speed of propagation of the density is quasi finite when the viscosity corresponds to {μ(ρ)=ρ^{α}} with {α > 1}. Furthermore the density is not far from converging asymptotically in time to the Barrenblatt solution of mass the initial density {ρ0}.
Urban density and pupil attainment
Gibbons, Stephen; Silva, Olmo
2008-01-01
We explore the association between urban density and pupil attainment using three cohorts of pupils in schooling in England. Although – as widely recognised – attainment in dense urban places is low on average, this is not because urban environments disadvantage pupils, but because the most disadvantaged pupils with low average attainments attend the most urbanised schools. To control for this, we exploit changes in urban density faced by pupils during compulsory transition from Primary to Se...
Primordial density and BAO reconstruction
Zhu, Hong-Ming; Chen, Xuelei
2016-01-01
We present a new method to reconstruct the primordial (linear) density field using the estimated nonlinear displacement field. The divergence of the displacement field gives the reconstructed density field. We solve the nonlinear displacement field in the 1D cosmology and show the reconstruction results. The new reconstruction algorithm recovers a lot of linear modes and reduces the nonlinear damping scale significantly. The successful 1D reconstruction results imply the new algorithm should also be a promising technique in the 3D case.
The Density of Sustainable Settlements
Lauring, Michael; Silva, Victor; Jensen, Ole B.; Heiselberg, Per
2010-01-01
This paper is the initial result of a cross-disciplinary attempt to encircle an answer to the question of optimal densities of sustainable settlements. Urban density is an important component in the framework of sustainable development and influences not only the character and design of cities but also the architectural and technical strategies of buildings. The paper is based on literature studies in the fields of urban mobility, urban ecology, urban design, architecture and civil engineerin...
International Nuclear Information System (INIS)
In this note we construct families of asymptotically flat, smooth, horizonless solutions with a large number of non-trivial two-cycles (bubbles) of N = 1 five-dimensional supergravity with an arbitrary number of vector multiplets, which may or may not have the charges of a macroscopic black hole and which contain the known bubbling solutions as a sub-family. We do this by lifting various multi-center BPS states of type IIA compactified on Calabi-Yau three-folds and taking the decompactification (M-theory) limit. We also analyse various properties of these solutions, including the conserved charges, the shape, especially the (absence of) throat and closed timelike curves, and relate them to the various properties of the four-dimensional BPS states. We finish by briefly commenting on their degeneracies and their possible relations to the fuzzball proposal of Mathur et al
International Nuclear Information System (INIS)
This paper deals with in situ solution mining. A significant fraction of known U.S. uranium reserves occur as low grade mineralization in sedimentary sandstone deposits located between 40 and 200 meters subsurface. For a variety of reasons, such deposits may not be economically developable by any method other than in situ solution mining. This coupled with the current market price of uranium has led to significant development and application of in situ solution mining for uranium production during the past several years. The process consists of the ore body; well field; lixiviant; uranium recovery process; waste treatment processes; and aquifer restoration. A tabulation of firms involved with a summary of the leach chemistry used is given. 3 refs
Trajectory versus probability density entropy
Bologna, Mauro; Grigolini, Paolo; Karagiorgis, Markos; Rosa, Angelo
2001-07-01
We show that the widely accepted conviction that a connection can be established between the probability density entropy and the Kolmogorov-Sinai (KS) entropy is questionable. We adopt the definition of density entropy as a functional of a distribution density whose time evolution is determined by a transport equation, conceived as the only prescription to use for the calculation. Although the transport equation is built up for the purpose of affording a picture equivalent to that stemming from trajectory dynamics, no direct use of trajectory time evolution is allowed, once the transport equation is defined. With this definition in mind we prove that the detection of a time regime of increase of the density entropy with a rate identical to the KS entropy is possible only in a limited number of cases. The proposals made by some authors to establish a connection between the two entropies in general, violate our definition of density entropy and imply the concept of trajectory, which is foreign to that of density entropy.
SOME UNUSUAL SOLUTIONS FOR EUROPEAN NETWORKS
Directory of Open Access Journals (Sweden)
Vernescu V
2012-03-01
Full Text Available Authors present several non-conventional solutions unused in Europe which are, however, frequently adopted in some medium (M and low (L voltages (V networks from North-American and Australian countries, especially in low density areas of consumption in rural and urban distribution. The proposed solutions may assure diversified supply possibilities in our middle and South–Eastern regions, as regards modernizing and upgrading the distribution networks. The solutions try to propose to adapt our European practice to the North-American experience, aiming at developing more flexible, cheaper and safer supply of the consumers, both at MV and at LV networks. Several original solutions promoted in Romanian networks and their peculiarities are also described. The paper presents distribution schemes at medium voltage in connection with low voltage supply in different condition of neutral treatment at MV or LV. It also shows the measures to be adopted in order to diminish the investment expenses in low voltage at the supplied consumers. The technical condition of co-existence of OHEL at MV and LV on the same poles, without jeopardizing the LV equipment, is necessary. Among the solutions proposed, the authors also describe the unconventional one, consisting in the supply of isolated monophase consumer at MV by ground return and also the conditions necessary for sure and safe operation of this particularly connection. Finally, there are shown some conclusions about the necessity to assure imposed environmental conditions.
Amiano, Mitch; Ethier, Kay; Thomas, Michael D
2006-01-01
Offering a unique approach to learning XML, this book walks readers through the process of building a complete, functional, end-to-end XML solutionFeatured case study is an online business product catalog that includes reports, data input/output, workflow, stylesheet formatting, RSS feeds, and integration with external services like Google, eBay, and AmazonThe format of presenting a problem and working through the design to come up with a solution enables readers to understand how XML markup allows a business to share data across applications internally or with partners or customers even thoug
Calculus problems and solutions
Ginzburg, A
2011-01-01
Ideal for self-instruction as well as for classroom use, this text helps students improve their understanding and problem-solving skills in analysis, analytic geometry, and higher algebra. More than 1,200 problems appear in the text, with concise explanations of the basic notions and theorems to be used in their solution. Many are followed by complete answers; solutions for the others appear at the end of the book. Topics include sequences, functions of a single variable, limit of a function, differential calculus for functions of a single variable, fundamental theorems and applications of dif
Jorgensen, Adam; Welch, John; Clark, Dan; Price, Christopher; Mitchell, Brian
2014-01-01
Tap the power of Big Data with Microsoft technologies Big Data is here, and Microsoft's new Big Data platform is a valuable tool to help your company get the very most out of it. This timely book shows you how to use HDInsight along with HortonWorks Data Platform for Windows to store, manage, analyze, and share Big Data throughout the enterprise. Focusing primarily on Microsoft and HortonWorks technologies but also covering open source tools, Microsoft Big Data Solutions explains best practices, covers on-premises and cloud-based solutions, and features valuable case studies. Best of all,
Density Sorting During the Evolution of Continental Crust
Kelemen, P. B.; Behn, M. D.; Hacker, B. R.
2015-12-01
We consider two settings - in addition to "delamination" of arc lower crust - in which dense, mafic eclogites founder into the convecting mantle while buoyant, felsic lithologies accumulate at the base of evolving continental crust. Arc processes play a central role in generating continental crust, but it remains uncertain how basaltic arc crust is transformed to andesitic continental crust. Dense, SiO2-poor products of fractionation may founder from the base of arc crust by "delamination", but lower arc crust after delamination has significantly different trace elements compared to lower continental crust (LCC). In an alternative model, buoyant magmatic rocks generated at arcs are first subducted, mainly via subduction erosion. Upon heating, these buoyant lithologies ascend through the mantle wedge or along a subduction channel, and are "relaminated" at the base of overlying crust (e.g., Hacker et al EPSL 11, AREPS 15). Average buoyant lavas and plutons for the Aleutians, Izu-Bonin-Marianas, Kohistan and Talkeetna arcs fall within the range of estimated LCC major and trace elements. Relamination is more efficient in generating continental crust than delamination. Himalayan cross-sections show Indian crust thrust beneath Tibetan crust, with no intervening mantle. There is a horizontal Moho at ca 80 km depth, extending from thickened Indian crust, across the region where Tibetan crust overlies Indian crust, into thickened Tibetan crust. About half the subducted Indian crust is present, whereas the other half is missing. Data (Vp/Vs; Miocene lavas formed by interaction of continental crust with mantle; xenolith thermometry) indicate 1000°C or more from ca 50 km depth to the Moho since the Miocene. We build on earlier studies (LePichon et al Tectonics 92, T'phys 97; Schulte-Pelkum et al Nature 05; Monsalve et al JGR 08) to advance the hypothesis that rapid growth of garnet occurs at 70-80 km and 1000°C within subducting Indian crust. Dense eclogites founder
Small time asymptotics of Ornstein-Uhlenbeck densities in Hilbert spaces
Jegaraj, Terence
2009-01-01
We show that Varadhan's small time asymptotics for densities of the solution of a stochastic differential equation in $\\mathbb{R}^n$ carries over to a Hilbert space-valued Ornstein-Uhlenbeck process whose transition semigroup is strongly Feller and symmetric. In the Hilbert space setting, densities are with respect to a Gaussian invariant measure.
Dependence of Reaction Rate Constants on Density in Supercritical Fluids
Institute of Scientific and Technical Information of China (English)
WANGTao; SHENZhongyao
2002-01-01
A new method,which correlates rate constants of chemical reactions and density or pressure in supercritical fluids,was developed.Based on the transition state theory and thermodynamic principles, the rate constant can be reasonably correlated with the density of the supercritical fluid,and a correlation equation was obtained. Coupled with the equation of state (EOS) of a supercritical solvent,the effect of pressure on reaction rate constant could be represented.Two typical systems were used to test this method.The result indicates that this method is suitable for dilute supercritical fluid solutions.
Statistical Gauge Theory for Relativistic Finite Density Problems
Institute of Scientific and Technical Information of China (English)
YING Shu-Qian
2001-01-01
A relativistic quantum field theory is presented for finite density problems based on the principle of locality. It is shown that, in addition to the conventional ones, a local approach to the relativistic quantum field theories at both zero and finite densities consistent with the violation of Bell-like inequalities should contain and provide solutions to at least three additional problems, namely, i) the statistical gauge invariance; ii) the dark components of the local observables; and iii) the fermion statistical blocking effects, based upon an asymptotic nonthermal ensemble. An application to models is presented to show the importance of the discussions.
Density profiles of dark matter halos with anisotropic velocity tensors
Hiotelis, Nicolaos
2002-01-01
We present density profiles, that are solutions of the spherical Jeans equation, derived under the following two assumptions: (i) the coarse grained phase-density follows a power-law of radius, rho/(sigma^3) proportional to r^{-alpha}, and (ii) the velocity anisotropy parameter is given by the relation beta_a(r) = beta_1 + 2 beta_2 {(r/r_*)/(1+(r/r_*)^2)} where beta_1, beta_2 are parameters and r_* equals twice the virial radius, r_{vir}, of the system. These assumptions are well motivated by...
Duple-EDA and sample density balancing
Institute of Scientific and Technical Information of China (English)
CAI YunPeng; XU Hua; SUN XiaoMin; JIA PeiFa; LIU ZeHua
2009-01-01
In this paper,a new method is proposed to overcome the problem of local optima traps in a class of evolutionary algorithms,called estimation of distribution algorithms (EDAs),in real-valued function optimization.The Duple-EDA framework is proposed in which not only the current best solutions but also the search history are modeled,so that long-term feedback can be taken into account.Sample Density Balancing (SDB) is proposed under the framework to alleviate the drift phenomenon in EDA.A selection scheme based on Pareto ranking considering both the fitness and the historical sample density is adopted,which prevents the algorithm from repeatedly sampling in a small region and directs it to explore potentially optimal regions,thus helps it avoid being stuck into local optima.An MBOA (mixed Bayesian optimization algorithm) version of the framework is implemented and tested on several benchmark problems.Experimental results show that the proposed method outperforms a standard niching method in these benchmark problems.
Optimization of constrained density functional theory
O'Regan, David D.; Teobaldi, Gilberto
2016-07-01
Constrained density functional theory (cDFT) is a versatile electronic structure method that enables ground-state calculations to be performed subject to physical constraints. It thereby broadens their applicability and utility. Automated Lagrange multiplier optimization is necessary for multiple constraints to be applied efficiently in cDFT, for it to be used in tandem with geometry optimization, or with molecular dynamics. In order to facilitate this, we comprehensively develop the connection between cDFT energy derivatives and response functions, providing a rigorous assessment of the uniqueness and character of cDFT stationary points while accounting for electronic interactions and screening. In particular, we provide a nonperturbative proof that stable stationary points of linear density constraints occur only at energy maxima with respect to their Lagrange multipliers. We show that multiple solutions, hysteresis, and energy discontinuities may occur in cDFT. Expressions are derived, in terms of convenient by-products of cDFT optimization, for quantities such as the dielectric function and a condition number quantifying ill definition in multiple constraint cDFT.
Covariant density functional theory for nuclear matter
Energy Technology Data Exchange (ETDEWEB)
Badarch, U.
2007-07-01
The present thesis is organized as follows. In Chapter 2 we study the Nucleon-Nucleon (NN) interaction in Dirac-Brueckner (DB) approach. We start by considering the NN interaction in free-space in terms of the Bethe-Salpeter (BS) equation to the meson exchange potential model. Then we present the DB approach for nuclear matter by extending the BS equation for the in-medium NN interaction. From the solution of the three-dimensional in-medium BS equation, we derive the DB self-energies and total binding energy which are the main results of the DB approach, which we later incorporate in the field theoretical calculation of the nuclear equation of state. In Chapter 3, we introduce the basic concepts of density functional theory in the context of Quantum Hadrodynamics (QHD-I). We reach the main point of this work in Chapter 4 where we introduce the DDRH approach. In the DDRH theory, the medium dependence of the meson-nucleon vertices is expressed as functionals of the baryon field operators. Because of the complexities of the operator-valued functionals we decide to use the mean-field approximation. In Chapter 5, we contrast microscopic and phenomenological approaches to extracting density dependent meson-baryon vertices. Chapter 6 gives the results of our studies of the EOS of infinite nuclear matter in detail. Using formulas derived in Chapters 4 and 5 we calculate the properties of symmetric and asymmetric nuclear matter and pure neutron matter. (orig.)
Stability of esmolol hydrochloride in intravenous solutions.
Baaske, D M; Dykstra, S D; Wagenknecht, D M; Karnatz, N N
1994-11-01
The stability of esmolol hydrochloride in a variety of i.v. solutions was studied. Solutions of esmolol hydrochloride 10 mg/mL were prepared separately in 0.45% sodium chloride injection, 0.9% sodium chloride injection, 5% dextrose injection, 5% dextrose and 0.45% sodium chloride injection, 5% dextrose and 0.9% sodium chloride injection, 5% dextrose with lactated Ringer's injection, lactated Ringer's injection, 5% sodium bicarbonate injection, and 5% dextrose injection with potassium chloride 40 meq/L. One glass and one polyvinyl chloride container of each solution (except glass only in the case of the solution in 5% sodium bicarbonate injection) were stored in the dark at 5 degrees C, under ambient room light at 23-27 degrees C, in the dark at 40 degrees C, and under intense light at 25-30 degrees C. At storage intervals up to 168 hours, samples were tested for esmolol hydrochloride concentration by high-performance liquid chromatography. Optical density and pH were also measured. Esmolol hydrochloride was stable in the various i.v. fluids for at least 168 hours when stored at 5 degrees C or 23-27 degrees C, for at least 24 hours when stored under intense light, and, with one exception, for at least 48 hours when stored at 40 degrees C. When mixed with 5% sodium bicarbonate injection, the drug was stable for only about 24 hours at 40 degrees C. There were no substantial changes in optical density or pH. The type of container had no effect on stability. With one exception, esmolol hydrochloride was stable in all the i.v. solutions under all the conditions tested. PMID:7856582
Density Distributions of Cyclotrimethylenetrinitramines (RDX)
Energy Technology Data Exchange (ETDEWEB)
Hoffman, D M
2002-03-19
As part of the US Army Foreign Comparative Testing (FCT) program the density distributions of six samples of class 1 RDX were measured using the density gradient technique. This technique was used in an attempt to distinguish between RDX crystallized by a French manufacturer (designated insensitive or IRDX) from RDX manufactured at Holston Army Ammunition Plant (HAAP), the current source of RDX for Department of Defense (DoD). Two samples from different lots of French IRDX had an average density of 1.7958 {+-} 0.0008 g/cc. The theoretical density of a perfect RDX crystal is 1.806 g/cc. This yields 99.43% of the theoretical maximum density (TMD). For two HAAP RDX lots the average density was 1.786 {+-} 0.002 g/cc, only 98.89% TMD. Several other techniques were used for preliminary characterization of one lot of French IRDX and two lot of HAAP RDX. Light scattering, SEM and polarized optical microscopy (POM) showed that SNPE and Holston RDX had the appropriate particle size distribution for Class 1 RDX. High performance liquid chromatography showed quantities of HMX in HAAP RDX. French IRDX also showed a 1.1 C higher melting point compared to HAAP RDX in the differential scanning calorimetry (DSC) consistent with no melting point depression due to the HMX contaminant. A second part of the program involved characterization of Holston RDX recrystallized using the French process. After reprocessing the average density of the Holston RDX was increased to 1.7907 g/cc. Apparently HMX in RDX can act as a nucleating agent in the French RDX recrystallization process. The French IRDX contained no HMX, which is assumed to account for its higher density and narrower density distribution. Reprocessing of RDX from Holston improved the average density compared to the original Holston RDX, but the resulting HIRDX was not as dense as the original French IRDX. Recrystallized Holston IRDX crystals were much larger (3-500 {micro}m or more) then either the original class 1 HAAP RDX or
Higher dimensional strange quark matter solutions in self creation cosmology
Şen, R.; Aygün, S.
2016-03-01
In this study, we have generalized the higher dimensional flat Friedmann-Robertson-Walker (FRW) universe solutions for a cloud of string with perfect fluid attached strange quark matter (SQM) in Self Creation Cosmology (SCC). We have obtained that the cloud of string with perfect fluid does not survive and the string tension density vanishes for this model. However, we get dark energy model for strange quark matter with positive density and negative pressure in self creation cosmology.
Meson loop effect on high density chiral phase transition
Sakaguchi, T; Kouno, H; Yahiro, M; Sakaguchi, Tomohiko; Matsuzaki, Masayuki; Kouno, Hiroaki; Yahiro, Masanobu
2006-01-01
We test the stability of the mean-field solution in the Nambu--Jona-Lasinio model. For stable solutions with respect to both the \\sigma and \\pi directions, we investigate effects of the mesonic loop corrections of 1/N_c, which correspond to the next-to-leading order in the 1/N_c expansion, on the high density chiral phase transition. The corrections weaken the first order phase transition and shift the critical chemical potential to a lower value. At N_c=3, however, instability of the mean field effective potential prevents us from determining the minimum of the corrected one.
Polymer solution phase separation: Microgravity simulation
Cerny, Lawrence C.; Sutter, James K.
1989-01-01
In many multicomponent systems, a transition from a single phase of uniform composition to a multiphase state with separated regions of different composition can be induced by changes in temperature and shear. The density difference between the phase and thermal and/or shear gradients within the system results in buoyancy driven convection. These differences affect kinetics of the phase separation if the system has a sufficiently low viscosity. This investigation presents more preliminary developments of a theoretical model in order to describe effects of the buoyancy driven convection in phase separation kinetics. Polymer solutions were employed as model systems because of the ease with which density differences can be systematically varied and because of the importance of phase separation in the processing and properties of polymeric materials. The results indicate that the kinetics of the phase separation can be performed viscometrically using laser light scattering as a principle means of following the process quantitatively. Isopycnic polymer solutions were used to determine the viscosity and density difference limits for polymer phase separation.
Density Of The Copper-Rich Cu-Pb-Fe Alloys
Sak T.; Kucharski M.
2015-01-01
Density of the copper-rich corner of the ternary Cu-Pb-Fe alloys was determined with the dilatometric method. Investigated alloys had constant copper content equal to 0.9, 0.8 and 0.7 mole fraction, and varied iron concentration up to 0.1 mole fraction. A model predicting the density of ternary solution from knowledge of density of pure component and the excess of molar volume for limiting binaries is proposed.
Density Of The Copper-Rich Cu-Pb-Fe Alloys
Directory of Open Access Journals (Sweden)
Sak T.
2015-09-01
Full Text Available Density of the copper-rich corner of the ternary Cu-Pb-Fe alloys was determined with the dilatometric method. Investigated alloys had constant copper content equal to 0.9, 0.8 and 0.7 mole fraction, and varied iron concentration up to 0.1 mole fraction. A model predicting the density of ternary solution from knowledge of density of pure component and the excess of molar volume for limiting binaries is proposed.
Aqueous polyethylene oxide solutions
International Nuclear Information System (INIS)
A number of aspects concerning the reorientation of polymer, water and ion hydration complexes have been studied in aqueous solution of polyethylene oxide (PEO). The polymer dynamics are investigated by 1H-PEO and 13C-PEO nuclear relaxation experiments. 162 refs.; 30 figs.; 19 tabs
Zee, van der S.E.A.T.M.; Leijnse, A.
2013-01-01
Solute transport is of importance in view of the movement of nutrient elements, e.g. towards the plant root system, and because of a broad range of pollutants. Pollution is not necessarily man induced, but may be due to geological or geohydrological causes, e.g. in the cases of pollution with arseni
Treatment of Aqueous Solutions
Van Spronsen, J.; Witkamp, G.J.
2013-01-01
The invention is directed to a process for the recovery or removal of one or more crystallizable compounds from an aqueous solution containing, apart from the said crystallizable compounds, one or more organic or inorganic scale- forming or scale-inducing materials having a lower solubility in water
Can Solution Supersaturation Affect Protein Crystal Quality?
Gorti, Sridhar
2013-01-01
The formation of large protein crystals of "high quality" is considered a characteristic manifestation of microgravity. The physical processes that predict the formation of large, high quality protein crystals in the microgravity environment of space are considered rooted in the existence of a "depletion zone" in the vicinity of crystal. Namely, it is considered reasonable that crystal quality suffers in earth-grown crystals as a result of the incorporation of large aggregates, micro-crystals and/or large molecular weight "impurities", processes which are aided by density driven convective flow or mixing at the crystal-liquid interface. Sedimentation and density driven convection produce unfavorable solution conditions in the vicinity of the crystal surface, which promotes rapid crystal growth to the detriment of crystal size and quality. In this effort, we shall further present the hypothesis that the solution supersaturatoin at the crystal surface determines the growth mechanism, or mode, by which protein crystals grow. It is further hypothesized that protein crystal quality is affected by the mechanism or mode of crystal growth. Hence the formation of a depletion zone in microgravity environment is beneficial due to inhibition of impurity incorporatoin as well as preventing a kinetic roughening transition. It should be noted that for many proteins the magnitude of neither protein crystal growth rates nor solution supersaturation are predictors of a kinetic roughening transition. That is, the kinetic roughening transition supersaturation must be dtermined for each individual protein.
Ion Pairing in Alkali Nitrate Electrolyte Solutions.
Xie, Wen Jun; Zhang, Zhen; Gao, Yi Qin
2016-03-10
In this study, we investigate the thermodynamics of alkali nitrate salt solutions, especially the formation of contact ion pairs between alkali cation and nitrate anion. The ion-pairing propensity shows an order of LiNO3 law of matching water affinity" is followed by these alkali nitrate salt solutions. The spatial patterns of contact ion pairs are different in the three salt solutions studied here: Li(+) forms the contact ion pair with only one oxygen of the nitrate while Na(+) and K(+) can also be shared by two oxygens of the nitrate. In reproducing the salt activity coefficient using Kirkwood-Buff theory, we find that it is essential to include electronic polarization for Li(+) which has a high charge density. The electronic continuum correction for nonpolarizable force field significantly improves the agreement between the calculated activity coefficients and their experimental values. This approach also improves the performance of the force field on salt solubility. From these two aspects, this study suggests that electronic continuum correction can be a promising approach to force-field development for ions with high charge densities. PMID:26901167