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.
Low buoyant density proteoglycans from saline and dissociative extracts of embryonic chicken retinas
Energy Technology Data Exchange (ETDEWEB)
Morris, J.E.; Ting, Y.P.; Birkholz-Lambrecht, A.
1984-03-01
Retinas were labeled in culture with (/sup 3/H)glucosamine or (/sup 3/H)leucine and (/sup 35/S)sulfate and extracted sequentially with physiologically balanced saline and 4 M guanidine HCl. They were dialyzed into associative conditions (0.5 M NaCl) and chromatographed on agarose columns. Under these conditions, some of the proteoglycans were associated in massive complexes that showed low buoyant densities when centrifuged in CsCl density gradients under dissociative conditions (4 M guanidine HCl). Much of the label in these complexes was in molecules other than proteoglycans. Most of the proteoglycans, however, were included on the agarose columns, where they appeared to be constitutionally of low buoyant density. They resisted attempts to separate potential low buoyant density contaminants from the major proteoglycans by direct CsCl density gradient centrifugation or by the fractionation of saline or 8 M urea extracts on diethylaminoethyl-Sephacel. The diethylaminoethyl-Sephacel fractions were either subjected to CsCl density gradient centrifugation or were chromatographed on Sephacryl S-300, in both cases before and after alkaline cleavage, to confirm the presence of typical O-linked glycosaminoglycans. The medium and balanced salt extracts were enriched in chondroitin sulfate and other sulfated macromolecules, possibly highly sulfated oligosaccharides, that resisted digestion by chondroitinase ABC but were electrophoretically less mobile than heparan sulfate. Guanidine HCl or urea extracts of the residues were mixtures of high and low density proteoglycans that were enriched in heparan sulfate.
Further studies on the relationship between platelet buoyant density and platelet age
International Nuclear Information System (INIS)
Boneu, B.; Vigoni, F.; Boneu, A.; Caranobe, C.; Sie, P.
1982-01-01
The relationship between platelet buoyant density and platelet age was investigated in eight human subjects submitted to an autologous chromium labeled platelet survival study. Platelets were isolated after isopycnic centrifugation using eight discontinuous isoosmotic stractan gradients (five subjects), or various continuous and linear isoosmolar gradients (three subjects). A paradoxical radioactivity enrichment of the dense platelets and a premature loss of radioactivity in the light platelets were observed. These results are explained by a shift of the radioactivity distribution curve toward higher densities during the 3-4 days after platelet injection, while the standard deviation of the distribution was conserved throughout the platelet life span. These results suggest that young platelets are heterogeneous and slightly less dense than the total platelet population
Energy Technology Data Exchange (ETDEWEB)
Abe, Satoshi, E-mail: abe.satoshi@jaea.go.jp; Ishigaki, Masahiro; Sibamoto, Yasuteru; Yonomoto, Taisuke
2016-07-15
Highlights: • This paper shows results of a small scale experiment and CFD analyses on a density stratification erosion with a vertical buoyant jet. • The particle image velocimetry (PIV) and quadrupole mass spectrometer (QMS) with a multiport rotating valve were applied. • Two typical well-used RANS models were applied. • The simulated stratification erosion was in agreement with the experimental result, which suggested that the turbulence mixing occurred only in the jet impinging region. - Abstract: The Japan Atomic Energy Agency (JAEA) has started the ROSA-SA project to investigate thermal hydraulic phenomena in a reactor containment vessel during a severe accident. The hydrogen distribution in the vessel is one of significant safety issues in discussing a potential of hydrogen combustion in the containment. Density stratification and its break-up are important phenomena affecting the hydrogen distribution. This paper focuses on a density stratification erosion and break-up mechanism with a vertical buoyant jet promoting the turbulent helium transport. Small scale experiment and computational fluid dynamics (CFD) analyses were carried out for investigating this phenomena. In the experiment, a rectangular vessel made with acrylic plates with a width of 1.5 m, a length of 1.5 m and a height of 1.8 m was used for visualizing flow field with particle image velocimetry (PIV) system. The quadrupole mass spectrometer (QMS) system with a multiport rotating valve was applied for measuring gaseous concentration at 20 elevation points. In CFD analysis with OpenFOAM, two typical well-used turbulence models were used: low-Reynolds number type k–ε model and SST k–ω model, with a turbulence model modification to consider the buoyant effect in the stratification. As a result, the stratification erosion in the CFD analyses with the modified turbulence model agreed well with the experimental data, indicating importance of the turbulence damping by the buoyant effect.
International Nuclear Information System (INIS)
Abe, Satoshi; Ishigaki, Masahiro; Sibamoto, Yasuteru; Yonomoto, Taisuke
2016-01-01
Highlights: • This paper shows results of a small scale experiment and CFD analyses on a density stratification erosion with a vertical buoyant jet. • The particle image velocimetry (PIV) and quadrupole mass spectrometer (QMS) with a multiport rotating valve were applied. • Two typical well-used RANS models were applied. • The simulated stratification erosion was in agreement with the experimental result, which suggested that the turbulence mixing occurred only in the jet impinging region. - Abstract: The Japan Atomic Energy Agency (JAEA) has started the ROSA-SA project to investigate thermal hydraulic phenomena in a reactor containment vessel during a severe accident. The hydrogen distribution in the vessel is one of significant safety issues in discussing a potential of hydrogen combustion in the containment. Density stratification and its break-up are important phenomena affecting the hydrogen distribution. This paper focuses on a density stratification erosion and break-up mechanism with a vertical buoyant jet promoting the turbulent helium transport. Small scale experiment and computational fluid dynamics (CFD) analyses were carried out for investigating this phenomena. In the experiment, a rectangular vessel made with acrylic plates with a width of 1.5 m, a length of 1.5 m and a height of 1.8 m was used for visualizing flow field with particle image velocimetry (PIV) system. The quadrupole mass spectrometer (QMS) system with a multiport rotating valve was applied for measuring gaseous concentration at 20 elevation points. In CFD analysis with OpenFOAM, two typical well-used turbulence models were used: low-Reynolds number type k–ε model and SST k–ω model, with a turbulence model modification to consider the buoyant effect in the stratification. As a result, the stratification erosion in the CFD analyses with the modified turbulence model agreed well with the experimental data, indicating importance of the turbulence damping by the buoyant effect.
DAENEN, S; HUIGES, W; MODDERMAN, E; HALIE, MR
Studies with synchronized or exponentially growing bacteria and mammalian cell lines are not able to demonstrate small changes in buoyant density during the cell cycle. Flowcytometric analysis of density separated acute myeloid leukemia cells, a system not dependent on time-related variables, shows
Changes in buoyant density relationships of two cell types of Coxiella burneti phase I
International Nuclear Information System (INIS)
Wachter, R.F.; Briggs, G.P.; Gangemi, J.D.; Pedersen, C.E. Jr.
1975-01-01
Coxiella burneti phase I, purified from a formalin-inactivated yolk-sac vaccine, was separated into two bands of morphologically distinct cell types when subjected to sucrose gradient centrifugation. Recycling of the less dense, rod-shaped cells in unbuffered sucrose gradients (pH 5.5 to 6.0) resulted in the formation of bands having the location and appearance of the original two bands. Recycling of the denser band of larger ovoid-shaped cells yielded a single band, suggesting that the larger cell type arose from the smaller cell. In contrast to vaccine-derived rickettsiae, live, cell culture-propagated phase I organisms formed a single band in unbuffered sucrose gradients, at the same density as the upper band of the vaccine preparation. Centrifugation of cell culture-derived rickettsiae for 26 to 48 h in sucrose gradients of pH 5.5 resulted in the formation of a second band, at the same density as the lower band of the vaccine preparation. This did not occur in gradients of pH 7.0. Treatment of cell culture-propagated rickettsiae with formalin or germicidal ultraviolet radiation induced a total shift of the less dense cell population to a zone of higher density when centrifuged isopycnically in CsCl gradients. This density change did not occur in sucrose gradients, suggesting a difference in the effect of these treatments on the permeability of the cell membrane to sucrose and CsCl
Evidence that platelet buoyant density, but not size, correlates with platelet age in man
International Nuclear Information System (INIS)
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
Non-Boussinesq turbulent buoyant jet of a low-density gas leaks into high-density ambient
El-Amin, Mohamed; Sun, Shuyu; Kanayama, Hiroshi
2010-01-01
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.
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.
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
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)
Abe, Satoshi; Ishigaki, Masahiro; Sibamoto, Yasuteru; Yonomoto, Taisuke
2015-01-01
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
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 and...
International Nuclear Information System (INIS)
Penner, J.E.; Haselman, L.C.; Edwards, L.L.
1985-01-01
Smoke from raging fires produced in the aftermath of a major nuclear exchange has been predicted to cause large decreases in surface temperatures. However, the extent of the decrease and even the sign of the temperature change, depend on how the smoke is distributed with altitude. We present a model capable of evaluating the initial distribution of lofted smoke above a massive fire. Calculations are shown for a two-dimensional slab version of the model and a full three-dimensional version. The model has been evaluated by simulating smoke heights for the Hamburg firestorm of 1943 and a smaller scale oil fire which occurred in Long Beach in 1958. Our plume heights for these fires are compared to those predicted by the classical Morton-Taylor-Turner theory for weakly buoyant plumes. We consider the effect of the added buoyancy caused by condensation of water-laden ground level air being carried to high altitude with the convection column as well as the effects of background wind on the calculated smoke plume heights for several fire intensities. We find that the rise height of the plume depends on the assumed background atmospheric conditions as well as the fire intensity. Little smoke is injected into the stratosphere unless the fire is unusually intense, or atmospheric conditions are more unstable than we have assumed. For intense fires significant amounts of water vapor are condensed raising the possibility of early scavenging of smoke particles by precipitation. 26 references, 11 figures
Mixing by turbulent buoyant jets in slender containers
International Nuclear Information System (INIS)
Voropayev, S.I.; Nath, C.; Fernando, H.J.S.
2012-01-01
A turbulent buoyant jet injected vertically into a slender cylinder containing a stratified fluid is investigated experimentally. The working fluid is water, and salt is used to change its density to obtain either a positively or negatively buoyant jet. The interest is the vertical density distribution in container and its dependence on time and other parameters. For each case (lighter or heavier jet) the experimental data could be collapsed into a ‘universal’ time dependent behavior, when properly non-dimensionalized. A theoretical model is advanced to explain the results. Possible applications include refilling of crude oil into U.S. strategic petroleum reserves caverns. -- Highlights: ► We addresses a critical issue on refill of Strategic Petroleum Reserves. ► We conduct experiments on negatively/positively buoyant turbulent jets in long cavern. ► Basing on results of experiments we developed theoretical model for refill operations.
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∣ Wind events, however, overwhelm the buoyancy-driven flow (∣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.
DEFF Research Database (Denmark)
Cushing, Kevin W.; Garofalo, Fabio; Magnusson, Cecilia
2017-01-01
. The density of the microparticles is determined by using a neutrally buoyant selection process that involves centrifuging of microparticles suspended in different density solutions, CsCl for microbeads and Percoll for cells. The speed of sound at 3 MHz in the neutrally buoyant suspensions is measured...... and fixed cells, such as red blood cells, white blood cells, DU-145 prostate cancer cells, MCF-7 breast cancer cells, and LU-HNSCC-25 head and-neck squamous carcinoma cells in phosphate buffered saline. The results show agreement with published data obtained by other methods....
Topology optimization for submerged buoyant structures
Picelli, R.; van Dijk, R.; Vicente, W.M.; Pavanello, R.; Langelaar, M.; van Keulen, A.
2017-01-01
This paper presents an evolutionary structural topology optimization method for the design of completely submerged buoyant modules with design-dependent fluid pressure loading. This type of structure is used to support offshore rig installation and pipeline transportation at all water depths. The
Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames
Directory of Open Access Journals (Sweden)
Zuo-Yu Sun
2014-07-01
Full Text Available Buoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures. The experimental observations show that the flame front of lean hydrogen-air premixed flames will not give rise to the phenomenon of cellular instability when the equivalence ratio has been reduced to a certain value, which is totally different from the traditional understanding of the instability characteristics of lean hydrogen premixed flames. Accompanied by the smoothened flame front, the propagation mode of lean hydrogen premixed flames transitions from initially spherical outwardly towards upwardly when the flames expand to certain sizes. To quantitatively investigate such buoyant instability behaviors, two parameters, “float rate (ψ” and “critical flame radius (Rcr”, have been proposed in the present article. The quantitative results demonstrate that the influences of initial pressure (Pint on buoyant unstable behaviors are different. Based on the effects of variation of density difference and stretch rate on the flame front, the mechanism of such buoyant unstable behaviors has been explained by the competition between the stretch force and the results of gravity and buoyancy, and lean hydrogen premixed flames will display buoyant unstable behavior when the stretch effects on the flame front are weaker than the effects of gravity and buoyancy.
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
Buoyant Helical Twin-Axial Wire Antenna
2016-11-15
February 2017 The below identified patent application is available for licensing. Requests for information should be addressed to...300169 1 of 9 BUOYANT HELICAL TWIN-AXIAL WIRE ANTENNA CROSS REFERENCE TO OTHER PATENT APPLICATIONS [0001] This application is a divisional...application and claims the benefit of the filing date of United States Patent Application No. 14/280,889; filed on May 19, 2014; and entitled “Twin-Axial
Bifurcation in a buoyant horizontal laminar jet
Arakeri, Jaywant H.; Das, Debopam; Srinivasan, J.
2000-06-01
The trajectory of a laminar buoyant jet discharged horizontally has been studied. The experimental observations were based on the injection of pure water into a brine solution. Under certain conditions the jet has been found to undergo bifurcation. The bifurcation of the jet occurs in a limited domain of Grashof number and Reynolds number. The regions in which the bifurcation occurs has been mapped in the Reynolds number Grashof number plane. There are three regions where bifurcation does not occur. The various mechanisms that prevent bifurcation have been proposed.
Buoyant plumes from solute gradients generated by non-motile Escherichia coli
International Nuclear Information System (INIS)
Benoit, M R; Brown, R B; Todd, P; Klaus, D M; Nelson, E S
2008-01-01
The effect of hydrodynamic mixing in bacterial populations due to bacterial chemotaxis is a well-described phenomenon known as bioconvection. Here we report the observation of buoyant plumes that result in hydrodynamic mixing, but in contrast to bioconvection the plumes form in the absence of bacterial motility. We propose that the buoyant flow originates from solute gradients created by bacterial metabolism, similar to solute-induced buoyant flow around growing protein crystals. In our experiments, metabolically-active non-motile Escherichia coli were layered along the bottom of flat-bottomed containers. The E. coli consumed glucose in the medium creating a lighter fluid beneath a heavier fluid. The situation is an example of Rayleigh–Taylor instability, in which a lighter fluid pushes on a heavier one. We developed a numerical model to study the effect of E. coli nutrient consumption and by-product excretion on extracellular solute gradients. The model solutions showed reduced-density fluid along the bottom of the fluid domain leading to buoyant plumes, which were qualitatively similar to the experimental plumes. We also used scaling analyses to study the dependence of plume formation on container size and cell size, and to investigate the effect of reduced gravity, such as the microgravity conditions encountered during spaceflight
Influence of roughness bottom on the dynamics of a buoyant cloud : application to a powder avalanche
Brossard, D.; Naaim-Bouvet, F.; Naaim, M.; Caccamo, P.
2009-04-01
A powder avalanche is referred to as a turbulent flow of snow particles in air. In the past such avalanches have been modelled by buoyant cloud in a watertank: buoyant clouds flow along an inclined plane from a small immersed tank with a release gate (injection is of short duration). The powder avalanches are simulated by a heavy fluid (salt water + colorant or kaolin) which is dispersing in a lighter one. Such experiments allow studies for the influence of roughness bottoms on the dynamics of a buoyant clouds. The authors studied the flows of buoyant clouds on an uniform slope of 20° with different roughness: smooth PVC, abrasive paper, bottom covered with glued particles of PMMA or with glued glass beads of different sizes arranged in a compact way. The released volume varies between 2 to 4 liters and the density of salted water is 1.2. Two cameras are used to obtain the height together with the front velocity. Inside the study area the front velocity is approximately constant and the height of the clouds varies linearly with the distance from the released gate as usually observed in previous experiments. So for each roughness a front velocity and height growth can be defined. It was shown from the experiments that: As the bottom increases in roughness, the front speed increases and the height growth decreases. Nevertheless the height of glued elements does not seem to be the most appropriate parameter to characterize the roughness.
Khine, Y. Y.; Walker, J. S.
1995-02-01
This paper treats the buoyant convection during the Czochralski growth of silicon crystals with a steady, strong, non-uniform, axisymmetric magnetic field. We consider a family of magnetic fields which includes a uniform axial magnetic field and a "cusp" field which is produced by identical solenoids placed symmetrically above and below the plane of the crystal-melt interface and free surface. We investigate the evolution of the buoyant convection as the magnetic field is changed continuously from a uniform axial field to a cusp field, with a constant value of the root-mean-squared magnetic flux density in the melt. We also investigate changes as the magnetic flux density is increased. While the cusp field appears very promising, perfect alignment between the local magnetic field vector and the crystal-melt interface or free surface is not possible, so the effects of a slight misalignment are also investigated.
A note on high Schmidt number laminar buoyant jets discharged horizontally
International Nuclear Information System (INIS)
Dewan, A.; Arakeri, J.H.; Srinivasan, J.
1992-01-01
This paper reports on a new model, developed for the integral analysis of high Schmidt number (or equivalently high Prandtl number) laminar buoyant jets discharged horizontally. This model assumes top-hat density profile across the inner core of jet and Gaussian velocity profile. Entrainment coefficient corresponding to pure laminar jet has been taken in the analysis. The prediction of the jet trajectory agree well with experimental data in the regions where the jet remains laminar
Buoyant density of Mycobacterium tuberculosis: implications for sputum processing
den Hertog, A. L.; Klatser, P. R.; Anthony, R. M.
2009-01-01
A tuberculosis (TB) research laboratory in the Netherlands. The concentration of Mycobacterium tuberculosis cells from sputum is almost universally performed by centrifugation after chemical liquefaction. These methods are thus dependent on the effective sedimentation of mycobacterial cells, and the
Eddy diffusivity of quasi-neutrally-buoyant inertial particles
Martins Afonso, Marco; Muratore-Ginanneschi, Paolo; Gama, Sílvio M. A.; Mazzino, Andrea
2018-04-01
We investigate the large-scale transport properties of quasi-neutrally-buoyant inertial particles carried by incompressible zero-mean periodic or steady ergodic flows. We show how to compute large-scale indicators such as the inertial-particle terminal velocity and eddy diffusivity from first principles in a perturbative expansion around the limit of added-mass factor close to unity. Physically, this limit corresponds to the case where the mass density of the particles is constant and close in value to the mass density of the fluid, which is also constant. Our approach differs from the usual over-damped expansion inasmuch as we do not assume a separation of time scales between thermalization and small-scale convection effects. For a general flow in the class of incompressible zero-mean periodic velocity fields, we derive closed-form cell equations for the auxiliary quantities determining the terminal velocity and effective diffusivity. In the special case of parallel flows these equations admit explicit analytic solution. We use parallel flows to show that our approach sheds light onto the behavior of terminal velocity and effective diffusivity for Stokes numbers of the order of unity.
Wake-Driven Dynamics of Finite-Sized Buoyant Spheres in Turbulence
Mathai, Varghese; Prakash, Vivek N.; Brons, Jon; Sun, Chao; Lohse, Detlef
2015-09-01
Particles suspended in turbulent flows are affected by the turbulence and at the same time act back on the flow. The resulting coupling can give rise to rich variability in their dynamics. Here we report experimental results from an investigation of finite-sized buoyant spheres in turbulence. We find that even a marginal reduction in the particle's density from that of the fluid can result in strong modification of its dynamics. In contrast to classical spatial filtering arguments and predictions of particle models, we find that the particle acceleration variance increases with size. We trace this reversed trend back to the growing contribution from wake-induced forces, unaccounted for in current particle models in turbulence. Our findings highlight the need for improved multiphysics based models that account for particle wake effects for a faithful representation of buoyant-sphere dynamics in turbulence.
Factors affecting the density of Brassica napus seeds
Young, L.; Jalink, H.; Denkert, R.; Reaney, M.
2006-01-01
Brassica napus seed is composed of low density oil (0.92 g.cm(-3)) and higher density solids (1.3-1.45 g.cm(-3)). Seed buoyant density may potentially be used to determine seed oil content and to separate seeds with different oil contents, however, we have found that seeds with the lowest buoyant
Modelling thermal radiation in buoyant turbulent diffusion flames
Consalvi, J. L.; Demarco, R.; Fuentes, A.
2012-10-01
This work focuses on the numerical modelling of radiative heat transfer in laboratory-scale buoyant turbulent diffusion flames. Spectral gas and soot radiation is modelled by using the Full-Spectrum Correlated-k (FSCK) method. Turbulence-Radiation Interactions (TRI) are taken into account by considering the Optically-Thin Fluctuation Approximation (OTFA), the resulting time-averaged Radiative Transfer Equation (RTE) being solved by the Finite Volume Method (FVM). Emission TRIs and the mean absorption coefficient are then closed by using a presumed probability density function (pdf) of the mixture fraction. The mean gas flow field is modelled by the Favre-averaged Navier-Stokes (FANS) equation set closed by a buoyancy-modified k-ɛ model with algebraic stress/flux models (ASM/AFM), the Steady Laminar Flamelet (SLF) model coupled with a presumed pdf approach to account for Turbulence-Chemistry Interactions, and an acetylene-based semi-empirical two-equation soot model. Two sets of experimental pool fire data are used for validation: propane pool fires 0.3 m in diameter with Heat Release Rates (HRR) of 15, 22 and 37 kW and methane pool fires 0.38 m in diameter with HRRs of 34 and 176 kW. Predicted flame structures, radiant fractions, and radiative heat fluxes on surrounding surfaces are found in satisfactory agreement with available experimental data across all the flames. In addition further computations indicate that, for the present flames, the gray approximation can be applied for soot with a minor influence on the results, resulting in a substantial gain in Computer Processing Unit (CPU) time when the FSCK is used to treat gas radiation.
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.
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...
46 CFR 160.010-6 - Capacity of buoyant apparatus.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Capacity of buoyant apparatus. 160.010-6 Section 160.010-6 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND... apparatus is not considered in determining the capacity. (b) [Reserved] ...
Filtered Rayleigh Scattering Measurements in a Buoyant Flowfield
2007-03-01
horizontal and vertical buoyant jet seen everyday is from automobile emissions and smokestacks, respectively. Figure 6. A horizontal...pressure between 150-200 psig in an externally stored 6000 gallon tank. The air is dried by a series of two 21 HRM series heatless driers which
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 and...
46 CFR 160.010-5 - Buoyant apparatus with plastic foam buoyancy.
2010-10-01
... 46 Shipping 6 2010-10-01 2010-10-01 false Buoyant apparatus with plastic foam buoyancy. 160.010-5... Vessels § 160.010-5 Buoyant apparatus with plastic foam buoyancy. (a) Buoyant apparatus with plastic foam buoyancy must have a plastic foam body with an external protective covering. The body may be reinforced as...
Herler, Jürgen; Dirnwöber, Markus
2011-10-31
Estimating the impacts of global and local threats on coral reefs requires monitoring reef health and measuring coral growth and calcification rates at different time scales. This has traditionally been mostly performed in short-term experimental studies in which coral fragments were grown in the laboratory or in the field but measured ex situ. Practical techniques in which growth and measurements are performed over the long term in situ are rare. Apart from photographic approaches, weight increment measurements have also been applied. Past buoyant weight measurements under water involved a complicated and little-used apparatus. We introduce a new method that combines previous field and laboratory techniques to measure the buoyant weight of entire, transplanted corals under water. This method uses an electronic balance fitted into an acrylic glass underwater housing and placed atop of an acrylic glass cube. Within this cube, corals transplanted onto artificial bases can be attached to the balance and weighed at predetermined intervals while they continue growth in the field. We also provide a set of simple equations for the volume and weight determinations required to calculate net growth rates. The new technique is highly accurate: low error of weight determinations due to variation of coral density (corals. We outline a transplantation technique for properly preparing corals for such long-term in situ experiments and measurements.
Buoyant triacylglycerol-filled green algae and methods therefor
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.
Barreyre, T.; Soule, S.; Reves-Sohn, R. A.
2009-12-01
The ability of mid-ocean ridge (MOR) volcanic systems to generate explosive eruptions is inhibited by the large hydrostatic pressures associated with their deep-sea location, which suppress volatile exsolution from the magma, and which preclude the generation of steam from lava-water interaction. Nevertheless, volcaniclastic material indicative of explosive activity has been found along many parts of the global MOR, raising important questions regarding the volatile systematics within mid-ocean ridge magmatic systems, and the processes by which volcaniclastic material may be dispersed during deep-sea eruptions. In this study we measured the settling velocities of volcaniclastic grains recovered from the Gakkel Ridge, Loihi Seamount, and Axial Volcano, and developed empirical settling velocity models as a function of particle size for three different particle shapes (angular, sheet, and rod). We then used the Morton, Turner, Taylor turbulent plume model to investigate how a plume of buoyant water may distribute this volcaniclastic material during a deep-sea eruption so that the physical characteristics of the deposits may be used to constrain the location and size (i.e., energy) of the eruptions that produced them. We ran the turbulent plume model for conditions ranging from a typical black smoker (~150 MW) to a megaplume (~30000 MW), and for water column density stratifications and currents corresponding to nominal conditions for the Arctic and Pacific Oceans. We found that maximum dispersal distances for the dominant size of volcaniclastic material within buoyant water plumes range from Pele). These distances are insufficient to explain the areal extent of the volcaniclastic deposits observed along the 85°E segment of the Gakkel Ridge and various portions of the Juan de Fuca Ridge, indicating that additional energy in the form of momentum from expanding gases is required to produce the observed deposits.
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...
A numerical model for buoyant oil jets and smoke plumes
International Nuclear Information System (INIS)
Zheng, L.; Yapa, P. D.
1997-01-01
Development of a 3-D numerical model to simulate the behaviour of buoyant oil jets from underwater accidents and smoke plumes from oil burning was described. These jets/plumes can be oil-in-water, oil/gas mixture in water, gas in water, or gas in air. The ambient can have a 3-D flow structure, and spatially/temporally varying flow conditions. The model is based on the Lagrangian integral technique. The model formulation of oil jet includes the diffusion and dissolution of oil from the jet to the ambient environment. It is suitable to simulate well blowout accidents that can occur in deep waters, including that of the North Sea. The model has been thoroughly tested against a variety of data, including data from both laboratory and field experiments. In all cases the simulation data compared very well with experimental data. 26 refs., 10 figs
Settling velocity of quasi-neutrally-buoyant inertial particles
Martins Afonso, Marco; Gama, Sílvio M. A.
2018-02-01
We investigate the sedimentation properties of quasi-neutrally buoyant inertial particles carried by incompressible zero-mean fluid flows. We obtain generic formulae for the terminal velocity in generic space-and-time periodic (or steady) flows, along with further information for flows endowed with some degree of spatial symmetry such as odd parity in the vertical direction. These expressions consist in space-time integrals of auxiliary quantities that satisfy partial differential equations of the advection-diffusion-reaction type, which can be solved at least numerically, since our scheme implies a huge reduction of the problem dimensionality from the full phase space to the classical physical space. xml:lang="fr"
Particulate size growth in a buoyant aerosol cloud
International Nuclear Information System (INIS)
Bathula, Sreekanth; Anand, S.; Sapra, B.K.; Chaturvedi, Shashank; Chaudhury, Probal; Pradeepkumar, K.S.
2018-01-01
Intentional/accidental release of Chemical, Biological, Radiological or Nuclear (CBRN) contaminant into environment create air and ground contamination. Preparedness and response towards such incidents require reliable models to predict the contamination levels. If the released contaminant is a gas, then it will undergo dilution by mixing with the atmospheric air hence air concentration will reduce to a greater extent and ground contamination may not be possible unless by means of wet deposition. But if the released contaminant is in the form of an aerosol cloud, significant ground deposition is possible due to dry deposition as well as wet deposition along with the air concentration. Particle size distribution inside the cloud is essential information required in computing the air concentration as well as ground concentration. The particle size distribution inside the cloud also undergoes temporal variation due to microscopic processes like particle-particle interactions (coagulation) and macroscopic like buoyancy, air entrainment and volume expansion etc. In this paper, the numerical computation of particle size and particle number concentration in an instantaneous, uniformly mixed, buoyant spherical puff released from a pressurised container is presented
46 CFR 160.010-4 - General requirements for buoyant apparatus.
2010-10-01
... light twine. (h) Each peripheral body type buoyant apparatus without a net or platform on the inside... pigmented in a dark color. A typical method of securing lifelines and pendants to straps of webbing is shown...
Horizontal H 2-air turbulent buoyant jet resulting from hydrogen leakage
El-Amin, Mohamed; Sun, Shuyu
2012-01-01
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
Energy Technology Data Exchange (ETDEWEB)
Ni, B Y; Wu, G X, E-mail: g.wu@ucl.ac.uk [College of Shipbuilding Engineering, Harbin Engineering University, Harbin 150001 (China)
2017-08-15
The free water exit of an initially fully submerged buoyant spheroid in an axisymmetric flow, which is driven by the difference between the vertical fluid force and gravity, is investigated. The fluid is assumed to be incompressible and inviscid, and the flow to be irrotational. The velocity potential theory is adopted together with fully nonlinear boundary conditions on the free surface. The surface tension is neglected and the pressure is taken as constant on the free surface. The acceleration of the body at each time step is obtained as part of the solution. Its nonlinear mutual dependence on the fluid force is decoupled through the auxiliary function method. The free-surface breakup by body penetration and water detachment from the body are treated through numerical conditions. The slender body theory based on the zero potential assumption on the undisturbed flat free surface is adopted, through which a condition for full water exit of a spheroid is obtained. Comparison is made between the results from the slender body theory and from the fully nonlinear theory through the boundary-element method, and good agreement is found when the spheroid is slender. Extensive case studies are undertaken to investigate the effects of body density, dimensions and the initial submergence. (paper)
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.
2016-10-01
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.
Influence of mesh non-orthogonality on numerical simulation of buoyant jet flows
International Nuclear Information System (INIS)
Ishigaki, Masahiro; Abe, Satoshi; Sibamoto, Yasuteru; Yonomoto, Taisuke
2017-01-01
Highlights: • Influence of mesh non-orthogonality on numerical solution of buoyant jet flows. • Buoyant jet flows are simulated with hexahedral and prismatic meshes. • Jet instability with prismatic meshes may be overestimated compared to that with hexahedral meshes. • Modified solvers that can reduce the influence of mesh non-orthogonality and reduce computation time are proposed. - Abstract: In the present research, we discuss the influence of mesh non-orthogonality on numerical solution of a type of buoyant flow. Buoyant jet flows are simulated numerically with hexahedral and prismatic mesh elements in an open source Computational Fluid Dynamics (CFD) code called “OpenFOAM”. Buoyant jet instability obtained with the prismatic meshes may be overestimated compared to that obtained with the hexahedral meshes when non-orthogonal correction is not applied in the code. Although the non-orthogonal correction method can improve the instability generated by mesh non-orthogonality, it may increase computation time required to reach a convergent solution. Thus, we propose modified solvers that can reduce the influence of mesh non-orthogonality and reduce the computation time compared to the existing solvers in OpenFOAM. It is demonstrated that calculations for a buoyant jet with a large temperature difference are performed faster by the modified solver.
Influence of mesh non-orthogonality on numerical simulation of buoyant jet flows
Energy Technology Data Exchange (ETDEWEB)
Ishigaki, Masahiro, E-mail: ishigaki.masahiro@jaea.go.jp; Abe, Satoshi; Sibamoto, Yasuteru; Yonomoto, Taisuke
2017-04-01
Highlights: • Influence of mesh non-orthogonality on numerical solution of buoyant jet flows. • Buoyant jet flows are simulated with hexahedral and prismatic meshes. • Jet instability with prismatic meshes may be overestimated compared to that with hexahedral meshes. • Modified solvers that can reduce the influence of mesh non-orthogonality and reduce computation time are proposed. - Abstract: In the present research, we discuss the influence of mesh non-orthogonality on numerical solution of a type of buoyant flow. Buoyant jet flows are simulated numerically with hexahedral and prismatic mesh elements in an open source Computational Fluid Dynamics (CFD) code called “OpenFOAM”. Buoyant jet instability obtained with the prismatic meshes may be overestimated compared to that obtained with the hexahedral meshes when non-orthogonal correction is not applied in the code. Although the non-orthogonal correction method can improve the instability generated by mesh non-orthogonality, it may increase computation time required to reach a convergent solution. Thus, we propose modified solvers that can reduce the influence of mesh non-orthogonality and reduce the computation time compared to the existing solvers in OpenFOAM. It is demonstrated that calculations for a buoyant jet with a large temperature difference are performed faster by the modified solver.
Modelling thermal radiation and soot formation in buoyant diffusion flames
International Nuclear Information System (INIS)
Demarco Bull, R.A.
2012-01-01
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)
Numerical simulation of turbulent buoyant flows in horizontal channels
International Nuclear Information System (INIS)
Seiter, C.
1995-09-01
A numerical method is presented, to calculate the three-dimensional, time-dependent large scale structure of turbulent buoyant flows. The subject of the study is the Rayleigh-Benard-convection with air (Pr=0.71, Ra=2.5 10 6 , 10 7 ) and sodium (Pr=0.006, Ra=8.4 10 4 , 2.5 10 5 , 10 6 , 10 7 ) and a fluid layer with water and an internal heat source (Pr=7.0, Ra I =1.5 10 10 ) at moderate and high Rayleigh-numbers. The goal of the work is both, the analysis of structures of instantaneous as well as the statistical analysis of spatially and/or time averaged data, to give a contribution to the investigation of the characteristics of turbulent natural convection mainly in fluids with small Prandtl-numbers. The large eddy simulation of natural convection requires the development of appropriate momentum and heat subgrid scale models and the formulation of new boundary conditions. The used energy-length-models in the computer code TURBIT are extended methodically by modification of the characteristic length scales of the sub scale turbulence. The reduction or the increase of the sub scale turbulence correlations, caused by the influence of solid boundaries or the stratification, is considered. In the same way the new boundary conditions for the diffusive terms of the conservation equations are seen to be necessary, when the thermal or in the case of liquid metals the more critical hydrodynamic boundary layer is resolved insufficiently or not at all. The extended and new methods, models and boundary conditions, which enabled the realization of the planned simulations, are presented. (orig.)
Morgan, J. P.; Shi, C.; Hasenclever, J.
2010-12-01
through faster mantle and reduces the distance though the slower asthenosphere. With this interpretation, the inference of a radially symmetric ~40-70 km high-~250 km-radius ‘bump’ of uplift of the base of buoyant plume-fed asthenosphere (PFA) can be directly estimated from PLUME results and the measured ~6-10% reduction in shear velocity between the PFA and underlying mantle. The inferred dynamic relief at the base of the PFA due to buoyancy within the underlying plume conduit is strikingly similar to the relief we find in recent axisymmetric 2D and Cartesian 3-D numerical experiments that explore the dynamics of mantle convection with a PFA. The width and height of the bump scale directly with the total buoyancy anomaly in the upper ~500km of the plume conduit, we discuss numerical experiments that quantify this relationship, show that it is, to first order, independent of the viscosity of material in the plume conduit or asthenosphere, and which also quantify the ~400km-radius geoid anomaly produced by these subasthenospheric mantle density anomalies. This effect can only happen if the asthenosphere is more buoyant than underlying mantle — and is therefore direct evidence that a buoyant plume-fed asthenosphere exists around Hawaii.
The Entrainment Rate for Buoyant Plumes in a Crossflow
Devenish, B. J.; Rooney, G. G.; Webster, H. N.; Thomson, D. J.
2010-03-01
We consider large-eddy simulations (LES) of buoyant plumes from a circular source with initial buoyancy flux F 0 released into a stratified environment with constant buoyancy frequency N and a uniform crossflow with velocity U. We make a systematic comparison of the LES results with the mathematical theory of plumes in a crossflow. We pay particular attention to the limits {tilde{U}≪1} and {tilde{U}≫ 1}, where {tilde{U}=U/(F_0 N)^{1/4}}, for which analytical results are possible. For {tilde{U}≫ 1}, the LES results show good agreement with the well-known two-thirds law for the rise in height of the plume. Sufficiently far above the source, the centreline vertical velocity of the LES plumes is consistent with the analytical z -1/3 and z -1/2 scalings for respectively {tilde{U}≪ 1} and {tilde{U}≫ 1}. In the general case, where the entrainment is assumed to be the sum of the contributions from the horizontal and vertical velocity components, we find that the discrepancy between the LES data and numerical solutions of the plume equations is largest for {tilde{U}=O(1)}. We propose a modified additive entrainment assumption in which the contributions from the horizontal and vertical velocity components are not equally weighted. We test this against observations of the plume generated by the Buncefield fire in the U.K. in December 2005 and find that the results compare favourably. We also show that the oscillations of the plume as it settles down to its final rise height may be attenuated by the radiation of gravity waves. For {tilde{U}≪ 1} the oscillations decay rapidly due to the transport of energy away from the plume by gravity waves. For {tilde{U}>rsim 1} the gravity waves travel in the same direction and at the same speed as the flow. In this case, the oscillations of the plume do not decay greatly by radiation of gravity waves.
Numerical modelling of the buoyant marine microplastics in the South-Eastern Baltic Sea
Bagaev, Andrei; Mizyuk, Artem; Chubarenko, Irina; Khatmullilna, Liliya
2017-04-01
Microplastics is a burning issue in the marine pollution science. Its sources, ways of propagation and final destiny pose a lot of questions to the modern oceanographers. Hence, a numerical model is an optimal tool for reconstruction of microplastics pathways and fate. Within the MARBLE project (lamp.ocean.ru), a model of Lagrangian particles transport was developed. It was tested coupled with oceanographic transport fields from the operational oceanography product of Copernicus Marine Monitoring Environment Service. Our model deals with two major types of microplastics such as microfibres and buoyant spheroidal particles. We are currently working to increase the grid resolution by means of the NEMO regional configuration for the south-eastern Baltic Sea. Several expeditions were organised to the three regions of the Baltic Sea (the Gotland, the Bornholm, and the Gdansk basins). Water samples from the surface and different water layers were collected, processed, and analysed by our team. A set of laboratory experiments was specifically designed to establish the settling velocity of particles of various shapes and densities. The analysis in question provided us with the understanding necessary for the model to reproduce the large-scale dynamics of microfibres. In the simulation, particles were spreading from the shore to the deep sea, slowly sinking to the bottom, while decreasing in quantity due to conditional sedimentation. Our model is expected to map out the microplastics life cycle and to account for its distribution patterns under the impact of wind and currents. For this purpose, we have already included the parameterization for the wind drag force applied to a particle. Initial results of numerical experiments seem to indicate the importance of proper implicit parameterization of the particle dynamics at the vertical solid boundary. Our suggested solutions to that problem will be presented at the EGU-2017. The MARBLE project is supported by Russian Science
Experimental study of heat and mass transfer in a buoyant countercurrent exchange flow
Conover, Timothy Allan
Buoyant Countercurrent Exchange Flow occurs in a vertical vent through which two miscible fluids communicate, the higher-density fluid, residing above the lower-density fluid, separated by the vented partition. The buoyancy- driven zero net volumetric flow through the vent transports any passive scalars, such as heat and toxic fumes, between the two compartments as the fluids seek thermodynamic and gravitational equilibrium. The plume rising from the vent into the top compartment resembles a pool fire plume. In some circumstances both countercurrent flows and pool fires can ``puff'' periodically, with distinct frequencies. One experimental test section containing fresh water in the top compartment and brine (NaCl solution) in the bottom compartment provided a convenient, idealized flow for study. This brine flow decayed in time as the concentrations approached equilibrium. A second test section contained fresh water that was cooled by heat exchangers above and heated by electrical elements below and operated steadily, allowing more time for data acquisition. Brine transport was reduced to a buoyancy- scaled flow coefficient, Q*, and heat transfer was reduced to an analogous coefficient, H*. Results for vent diameter D = 5.08 cm were consistent between test sections and with the literature. Some results for D = 2.54 cm were inconsistent, suggesting viscosity and/or molecular diffusion of heat become important at smaller scales. Laser Doppler Velocimetry was used to measure velocity fields in both test sections, and in thermal flow a small thermocouple measured temperature simultaneously with velocity. Measurement fields were restricted to the plume base region, above the vent proper. In baseline periodic flow, instantaneous velocity and temperature were ensemble averaged, producing a movie of the average variation of each measure during a puffing flow cycle. The temperature movie revealed the previously unknown cold core of the puff during its early development. The
The effect of particle properties on the depth profile of buoyant plastics in the ocean
Kooi, Merel; Reisser, J.; Slat, B.; Ferrari, F.; Schmid, M.; Cunsolo, S.; Brambini, R.; Noble, K.; Sirks, L.A.; Linders, T.E.W.; Schoeneich-Argent, R.I.; Koelmans, A.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
Energy Technology Data Exchange (ETDEWEB)
Brown, Richard S.; Pflugrath, Brett D.; Carlson, Thomas J.; Deng, Zhiqun
2012-02-03
On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing through hydroturbines experience a rapid decrease in pressure as they pass by the turbine blade and the severity of this decompression can be highly variable. This rapid decrease in pressure can result in injuries such as swim bladder rupture, exophthalmia, and emboli and hemorrhaging in the fins and tissues. However, recent research indicates that the presence of a telemetry tag (acoustic, radio, inductive) implanted inside the coelom of a juvenile salmon increases the likelihood that the fish will be injured or die during turbine passage. Thus, previous research conducted using telemetry tags implanted into the coelom of fish may have been inaccurate. Thus, a new technique is needed to provide unbiased estimates of survival through turbines. This research provides an evaluation of the effectiveness of a neutrally buoyant externally attached acoustic transmitter. Both nontagged fish and fish tagged with a neutrally buoyant external transmitter were exposed to a range of rapid decompressions simulating turbine passage. Juvenile Chinook salmon tagged with a neutrally buoyant externally attached acoustic transmitter did not receive a higher degree of barotrauma than their nontagged counterparts. We suggest that future research include field-based comparisons of survival and behavior among fish tagged with a neutrally buoyant external transmitter and those internally implanted with transmitters.
Fan, Jianke; Zhao, Dapeng; Dong, Dongdong
2016-02-01
We determined P-wave tomographic images by inverting a large number of arrival-time data from 2749 local earthquakes and 1462 teleseismic events, which are used to depict the three-dimensional morphology of the subducted Eurasian Plate along the northern segment of the Manila Trench. Dramatic changes in the dip angle of the subducted Eurasian Plate are revealed from the north to the south, being consistent with the partial subduction of a buoyant plateau beneath the Luzon Arc. Slab tears may exist along the edges of the buoyant plateau within the subducted plate induced by the plateau subduction, and the subducted lithosphere may be absent at depths greater than 250 km at ˜19°N and ˜21°N. The subducted buoyant plateau is possibly oriented toward NW-SE, and the subducted plate at ˜21°N is slightly steeper than that at ˜19°N. These results may explain why the western and eastern volcanic chains in the Luzon Arc are separated by ˜50 km at ˜18°N, whereas they converge into a single volcanic chain northward, which may be related to the oblique subduction along the Manila Trench caused by the northwestern movement of the Philippine Sea Plate. A low-velocity zone is revealed at depths of 20-200 km beneath the Manila Accretionary Prism at ˜22°N, suggesting that the subduction along the Manila Trench may stop there and the collision develops northward. The Taiwan Orogeny may originate directly from the subduction of the buoyant plateau, because the initial time of the Taiwan Orogeny is coincident with that of the buoyant plateau subduction.
A buoyant plume adjacent to a headland-Observations of the Elwha River plume
Warrick, J.A.; Stevens, A.W.
2011-01-01
Small rivers commonly discharge into coastal settings with topographic complexities - such as headlands and islands - but these settings are underrepresented in river plume studies compared to more simplified, straight coasts. The Elwha River provides a unique opportunity to study the effects of coastal topography on a buoyant plume, because it discharges into the Strait of Juan de Fuca on the western side of its deltaic headland. Here we show that this headland induces flow separation and transient eddies in the tidally dominated currents (O(100. cm/s)), consistent with other headlands in oscillatory flow. These flow conditions are observed to strongly influence the buoyant river plume, as predicted by the "small-scale" or "narrow" dynamical classification using Garvine's (1995) system. Because of the transient eddies and the location of the river mouth on the headland, flow immediately offshore of the river mouth is directed eastward twice as frequently as it is westward. This results in a buoyant plume that is much more frequently "bent over" toward the east than the west. During bent over plume conditions, the plume was attached to the eastern shoreline while having a distinct, cuspate front along its westernmost boundary. The location of the front was found to be related to the magnitude and direction of local flow during the preceding O(1. h), and increases in alongshore flow resulted in deeper freshwater mixing, stronger baroclinic anomalies, and stronger hugging of the coast. During bent over plume conditions, we observed significant convergence of river plume water toward the frontal boundary within 1. km of the river mouth. These results show how coastal topography can strongly influence buoyant plume behavior, and they should assist with understanding of initial coastal sediment dispersal pathways from the Elwha River during a pending dam removal project. ?? 2010.
Cross-flow shearing effects on the trajectory of highly buoyant bent-over plumes
Tohidi, Ali; Kaye, Nigel Berkeley; Gollner, Michael J.
2017-11-01
The dynamics of highly buoyant plumes in cross-flow is ubiquitous throughout both industrial and environmental phenomena. The rise of smoke from a chimney, wastewater discharge into river currents, and dispersion of wildfire plumes are only a few instances. There have been many previous studies investigating the behavior of jets and highly buoyant plumes in cross-flow. So far, however, very little attention has been paid to the role of shearing effects in the boundary layer on the plume trajectory, particularly on the rise height. Numerical simulations and dimensional analysis are conducted to characterize the near- and far-field behavior of a highly buoyant plume in a boundary layer cross-flow. The results show that shear in the cross-flow leads to large differences in the rise height of the plume in relation to a uniform cross-flow, especially at far-field. This material is based upon work supported by the National Science Foundation under Grant No.1200560. Any opinions, findings, and conclusions or recommendations expressed in the material are of the authors and do not necessarily reflect the views of NSF.
Wang, Yi; Huang, Yanqiu; Liu, Jiaping; Wang, Hai; Liu, Qiuhan
2013-01-01
The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and veloc...
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.
Numerical studies of pulsating buoyant plume in isothermal and non isothermal situations
International Nuclear Information System (INIS)
Sharma, Pavan K.; Singh, R.K.; Mohanty, Ananya; Das, D.
2014-01-01
A computational study has been carried out for predicting the behaviour of buoyant plume in isothermal and non isothermal configuration. General simulation objectives of any buoyant flow simulation are macroscopic in nature and deals with the grass data in respect of buoyancy induced scalar transport. However, the accuracy of predicting such macroscopic parameters is a strong function of several other microscopic parameters which govern the overall macroscopic behaviour. Some of the microscopic parameters for analysis could be buoyancy induced stable/unstable flows, relative plume behaviour, baroclinic velocity distribution etc. Only the CFD based flow modelling approach is capable of calculating several of these aspects. LES based modelling scores over the conventional RANS based computational modelling. The primary objective of the present study was to model buoyant plume simulation of different types in order to explore the details regarding plume and flow structure, instabilities and puffing behaviour. One of the influencing parameters on the overall plume behaviour is the buoyancy resolution index i.e. fineness of chosen grid in relation to the buoyancy intensity and other hydrodynamic parameters. The grid sensitivity studies have been carried out to find out the optimum value grid size by way of buoyant pool fire simulations. Comparative simulation has also been made for a square and round pool fire and it was found that for engineering simulations equivalent area square pool modeling is sufficient. Using the optimum value of grid size and square pool shape simulations have been carried out for different value of fire intensity. The flame puffing frequency as calculated by the reported correlation was compared against the computationally observed puffing frequency and the agreement was generally found to be excellent. Besides these results the comparisons of predicted peak flames temperatures data for various case studies with the available experimental data
Mier-Torrecilla, Monica; Geyer, Adelina; Phillips, Jeremy C.; Idelsohn, Sergio R.; Oñate, Eugenio
2010-05-01
In this work we investigate numerically the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid using the Particle Finite Element Method (PFEM), a newly developed tool that combines the flexibility of particle-based methods with the accuracy of the finite element discretization. In order to test the applicability of PFEM to the study of negatively buoyant jets, we have compared the two-dimensional numerical results with experiments investigating the injection of a jet of dyed water through a nozzle in the base of a cylindrical tank containing rapeseed oil. In both simulations and experiments, the fountain inlet flow velocity and nozzle diameter were varied to cover a wide range of Reynolds Re and Froude numbers Fr, such that 0.1 < Fr < 30, reproducing both weak and strong fountains in a laminar regime (8 < Re < 1350). Numerical results, together with the experimental observations, allow us to describe three different fountain behaviors that have not been previously reported. Based on the Re and Fr values for the numerical and experimental simulations, we have built a regime map to define how these values may control the occurrence of each of the observed flow types. Whereas the Fr number itself provides a prediction of the maximum penetration height of the jet, its combination with the Re number provides a prediction of the flow behavior for a specific nozzle diameter and injection velocity. Conclusive remarks concerning the dynamics of negatively buoyant jets may be applied later on to several geological situations, e.g. the flow structure of a fully submerged subaqueous eruptive vent discharging magma or the replenishment of magma chambers in the Earth's crust.
The thermal interaction of a buoyant plume from a calandria tube with an oblique jet
Energy Technology Data Exchange (ETDEWEB)
Rossouw, D.J.; Atkins, M.D.; Beharie, K. [Nuclear Science Division, School of Mechanical & Aeronautical Engineering, University of the Witwatersrand, Johannesburg (South Africa); Kim, T., E-mail: tong.kim@wits.ac.za [Nuclear Science Division, School of Mechanical & Aeronautical Engineering, University of the Witwatersrand, Johannesburg (South Africa); Rhee, B.W.; Kim, H.T. [Severe Accident and PHWR Safety Research Division, Korea Atomic Energy Research Institute, Daejun (Korea, Republic of)
2016-12-15
Highlights: • A crucial role of relative orientation between mixed convection modes is observed. • The extent of thermal interaction strongly depends on the relative orientation. • Coolant flow is substantially diffused by a buoyant plume if counter-acting. • Slightly oblique coolant flow to the gravitational axis provides the best cooling. - Abstract: Severe reactor core damage may occur from fuel channel failure as a consequence of excessive heat emitted from calandria tubes (CTs) in a pressurised heavy water (D{sub 2}O) reactor (CANDU). The heating of the CTs is caused by creep deformation of the pressure tubes (PTs), which may be ballooning or sagging depending on the internal pressure of the PTs. The deformation of the pressure tube is due to overheating as a result of a loss-of-coolant accident (LOCA) and emergency core cooling system (ECCS) failure. To prevent the exacerbation of the LOCA, circulating D{sub 2}O in the moderator tank may be utilized by forming a secondary jet that externally cools the individual CTs. The buoyant plume develops around the CTs and interacts with the secondary jet at a certain oblique angle with respect to the gravitational axis, depending on the spatial location of the hot calandria tubes (or the hot reactor core region). This study reports on how the local and overall heat transfer characteristics on a calandria tube where the buoyant plume develops, are altered by the obliqueness of the external secondary jet (from a co-current jet to a counter-current jet) in a simplified configuration at the jet Reynolds number of Re{sub j} = 1500 for the Archimedes number of Ar{sub D} = 0.11 and Rayleigh number of Ra{sub D} = 1.6 × 10{sup 6} (modified Rayleigh number of 3.0 × 10{sup 7}).
Numerical simulation of fuel mixing with air in laminar buoyant vortex rings
International Nuclear Information System (INIS)
Prasad, M. Jogendra; Sundararajan, T.
2016-01-01
Highlights: • At large Reynolds number, small vortex ring is formed due to thin boundary layer. • At higher stroke to diameter ratio, larger vortex is formed which travels farther. • After formation, trailing stem transfers circulation and fuel to the ring by buoyancy. • Formation number of buoyant vortex ring is higher than that of non-buoyant ring. • Buoyant fuel puffs entrain more air than non-buoyant air-premixed fuel puffs. - Abstract: The formation and evolution of vortex rings consisting of methane-air mixtures have been numerically simulated for different stroke to diameter (L/D) ratios (1.5, 3.5 and 6), Reynolds numbers (1000 and 2000) and initial mixture compositions (fuel with 0%, 15% and 30% of stoichiometric air). The numerical simulations are first validated by comparing with the results of earlier computational studies and also with in-house data from smoke visualization studies. In pure methane case, buoyancy significantly aids the upward rise of the vortex ring. The increase of vortex core height with time is faster for larger L/D ratio, contributed mainly by the larger initial puff volume. The radial size of the vortex also increases rapidly with time during the formation stage; this is followed by a slight shrinkage when piston comes to a stop. Later, a slow radial growth of the ring occurs due to the entrainment of ambient air, except during vortex pinch-off. The boundary layer thickness δ_e at orifice exit decreases as Re"−"0"."5 at a fixed L/D ratio; this in turn, results in a vortex of smaller size and circulation level, at a relatively higher Reynolds number. For L/D values greater than the critical value, a trailing stem is formed behind the ring vortex which feeds circulation and fuel into the vortex ring in the later stages of vortex evolution. Mass fraction contours indicate that fuel-air mixing is more effective within the vortex than in the stem. Ambient air entrainment is larger at higher L/D ratio and lower Re, for the
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.
Laboratory experiments on the interaction between inclined negatively buoyant jets and regular waves
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Ferrari Simone
2015-01-01
Full Text Available In this paper we present the results from a series of laboratory experiments on inclined negatively buoyant jets released in a receiving environment with waves. This simulates the case, typical of many practical applications, of the sea discharge of fluids denser than the receiving environment, as in the case of the brine from a desalination plant. The experiments were performed employing a Light Induced Fluorescence (LIF technique, in order to measure the concentration fields. Both the jet and the wave motion features were varied, in order to simulate a typical discharge into the Mediterranean Sea. Reference discharges in a stagnant environment were performed as well. The jet behaviour was analyzed from a statistical point of view, both considering the global phenomenon and its single phases. The influence of the wave motion on the inclined negatively buoyant jet geometry and dilution turns out to be a combined action of a split into two branches of the jet and a rotation. Their combined action decreases the jet maximum height and the impact distance, and is the main cause for the higher dilution reached in a wavy environment.
Characterization of buoyant fluorescent particles for field observations of water flows.
Tauro, Flavia; Aureli, Matteo; Porfiri, Maurizio; Grimaldi, Salvatore
2010-01-01
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.
Characterization of Buoyant Fluorescent Particles for Field Observations of Water Flows
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Flavia Tauro
2010-12-01
Full Text Available In this paper, the feasibility of off-the-shelf buoyant fluorescent microspheres as particle tracers in turbid water flows is investigated. Microspheres’ fluorescence intensity is experimentally measured and detected in placid aqueous suspensions of increasing concentrations of clay to simulate typical conditions occurring in natural drainage networks. Experiments are conducted in a broad range of clay concentrations and particle immersion depths by using photoconductive cells and image-based sensing technologies. Results obtained with both methodologies exhibit comparable trends and show that the considered particles are fairly detectable in critically turbid water flows. Further information on performance and integration of the studied microspheres in low-cost measurement instrumentation for field observations is obtained through experiments conducted in a custom built miniature water channel. This experimental characterization provides a first assessment of the feasibility of commercially available buoyant fluorescent beads in the analysis of high turbidity surface water flows. The proposed technology may serve as a minimally invasive sensing system for hazardous events, such as pollutant diffusion in natural streams and flash flooding due to extreme rainfall.
Zhang, Congyao; Churazov, Eugene; Schekochihin, Alexander A.
2018-05-01
Buoyant bubbles of relativistic plasma in cluster cores plausibly play a key role in conveying the energy from a supermassive black hole to the intracluster medium (ICM) - the process known as radio-mode AGN feedback. Energy conservation guarantees that a bubble loses most of its energy to the ICM after crossing several pressure scale heights. However, actual processes responsible for transferring the energy to the ICM are still being debated. One attractive possibility is the excitation of internal waves, which are trapped in the cluster's core and eventually dissipate. Here we show that a sufficient condition for efficient excitation of these waves in stratified cluster atmospheres is flattening of the bubbles in the radial direction. In our numerical simulations, we model the bubbles phenomenologically as rigid bodies buoyantly rising in the stratified cluster atmosphere. We find that the terminal velocities of the flattened bubbles are small enough so that the Froude number Fr ≲ 1. The effects of stratification make the dominant contribution to the total drag force balancing the buoyancy force. Clear signs of internal waves are seen in the simulations. These waves propagate horizontally and downwards from the rising bubble, spreading their energy over large volumes of the ICM. If our findings are scaled to the conditions of the Perseus cluster, the expected terminal velocity is ˜100 - 200 km s-1 near the cluster cores, which is in broad agreement with direct measurements by the Hitomi satellite.
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.
Energy Technology Data Exchange (ETDEWEB)
Manera, Annalisa; Bardet, Philippe; Petrov, Victor
2018-03-29
Fluid jets interacting with a stratified layer play an important role in the safety of several reactor designs. In the containment of nuclear power plants, fluid jets dominate the transport and mixing of gaseous species and consequent hydrogen distribution in case of a severe accident. The mixing phenomena in the containment are driven by buoyant high-momentum injections (jets) and low momentum injection plumes. Mixing near the postulated break is initially dominated by high flow velocities. Plumes with moderate flow velocities are instead relevant in the break compartment during the long-term pressurization phase, or in any of the apertures between two connected compartments if the mass flows are sufficiently high and the density differences between efflux and ambient are sufficiently low. Phenomena of interest include free plumes (as produced by the efflux from the break compartment in a larger room or directly from a break flow), wall plumes (such those produced by low mass flows through inter-compartment apertures), and propagating stratification fronts in the ambient (for any stably stratified conditions). These phenomena have been highly ranked about nuclear reactor design, especially regarding of safety protocols. During a Pressurized Thermal Shock (PTS) scenario, the interaction between the cold ECCS injection plume and the stratified fluid present in the cold (or hot) leg is important in order to determine the temperature at the time-dependent temperature at the inlet of the reactor pressure vessel (RPV) and the potential to cause a thermal shock on the RPV wall. In sodium-cooled fast reactors (SFRs), core channels are typically hydro-dynamically isolated so that there exists a considerable temperature variation at the exit of adjacent fuel assemblies. All the above phenomena are characterized by the interaction of buoyant jets with the stratified flow. In stratified layers baroclinic forces create significant redistribution of turbulent kinetic energy and
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...
Application of Recurrence Analysis to the period doubling cascade of a confined buoyant flow
International Nuclear Information System (INIS)
Angeli, D; Corticelli, M A; Fichera, A; Pagano, A
2017-01-01
Recurrence Analysis (RA) is a promising and flexible tool to identify the behaviour of nonlinear dynamical systems. The potentialities of such a technique are explored in the present work, for the study of transitions to chaos of buoyant flow in enclosures. The case of a hot cylindrical source centred in a square enclosure, is considered here, for which an extensive database of results has been collected in recent years. For a specific value of the system aspect ratio, a sequence of period doublings has been identified, leading to the onset of chaos. RA is applied here to analyse the different flow regimes along the route to chaos. The qualitative visual identification of patterns and the statistics given by the quantitative analysis suggest that this kind of tool is well suited to the study of transitional flows in thermo-fluid dynamics. (paper)
Meanders and eddy formation by a buoyant coastal current flowing over a sloping topography
Directory of Open Access Journals (Sweden)
L. Cimoli
2017-11-01
Full Text Available This study investigates the linear and non-linear instability of a buoyant coastal current flowing along a sloping topography. In fact, the bathymetry strongly impacts the formation of meanders or eddies and leads to different dynamical regimes that can both enhance or prevent the cross-shore transport. We use the Regional Ocean Modeling System (ROMS to run simulations in an idealized channel configuration, using a fixed coastal current structure and testing its unstable evolution for various depths and topographic slopes. The experiments are integrated beyond the linear stage of the instability, since our focus is on the non-linear end state, namely the formation of coastal eddies or meanders, to classify the dynamical regimes. We find three non-linear end states, whose properties cannot be deduced solely from the linear instability analysis. They correspond to a quasi-stable coastal current, the propagation of coastal meanders, and the formation of coherent eddies. We show that the topographic parameter Tp, defined as the ratio of the topographic Rossby wave speed over the current speed, plays a key role in controlling the amplitude of the unstable cross-shore perturbations. This result emphasizes the limitations of linear stability analysis to predict the formation of coastal eddies, because it does not account for the non-linear saturation of the cross-shore perturbations, which is predominant for large negative Tp values. We show that a second dimensionless parameter, the vertical aspect ratio γ, controls the transition from meanders to coherent eddies. We suggest the use of the parameter space (Tp, γ to describe the emergence of coastal eddies or meanders from an unstable buoyant current. By knowing the values of Tp and γ for an observed flow, which can be calculated from hydrological sections, we can identify which non-linear end state characterizes that flow – namely if it is quasi-stable, meanders, or forms eddies.
Directory of Open Access Journals (Sweden)
Yi Wang
2013-01-01
Full Text Available The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0 Pa to −5 Pa.
Wang, Yi; Huang, Yanqiu; Liu, Jiaping; Wang, Hai; Liu, Qiuhan
2013-01-01
The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0 Pa to -5 Pa.
Do buoyant plumes enhance cross-shelf transport in the Black Sea?
Sedakov, Roman; Zavialov, Peter; Izhitsky, Alexander
2017-04-01
Like many inland seas, the Black Sea is exposed to massive continental discharges on the one hand and significant anthropogenic stresses, including pollution, on the other. It is, therefore, important to understand mechanisms of advection of continental water into the sea and factors that may influence transport of such water across shelf areas. In this study, we focus on the coastal segment of the Black Sea between the Feodosia Bay, which includes nature reserve and resort areas, and the Kerch Strait. The Sea of Azov outflow penetrates into the Black Sea through the latter, forming a plume of relatively fresh, light waters with elevated concentrations of suspended matter but also pollutants, especially hydrocarbons. This plume, which can be detected via satellite imagery of the region, extends on over 70 km from the Kerch Strait outfall along Crimea shore and reaches the Feodosia Bay, making that area the most polluted of the Crimea shoreline. In situ velocity measurements were conducted at a mooring station deployed in the area at the depth of 5 and 21.5 meters during the period 17th-23rd of May 2015. These data demonstrated high correlation of the wind stress with the cross-shore component of the velocity in the surface layer and anti-correlation with that in the bottom layer during the periods when a two-layered stratification of the water column due to the occurrence of the Azov plume was present, and lack of such correlation otherwise. In order to investigate whether the buoyant plume in the surface layer is capable of fortifying the wind-driven cross-shelf exchanges, we develop a dynamical model of current forming under the influence of wind tension, pressure gradient and Earth's rotation in a simple one- and a two- layer setups. Firstly, a 2D model was investigated that did not account Coriolis effect. Secondly, a 3D model with Coriolis effect was investigated. The main parameter of the problem is the eddy diffusivity coefficient, which we choose to be
Barreyre, Thibaut; Soule, S. Adam; Sohn, Robert A.
2011-08-01
We use tank experiments to measure settling rates of deep-sea volcaniclastic material recovered from the Arctic (85°E Gakkel Ridge) and Pacific (Juan de Fuca Ridge, Loihi seamount) Oceans. We find that clast size and shape exert a strong influence on settling velocity, with velocities of ~ 30 cm/s for large (~ 8 mm), blocky clasts, compared to velocities of ~ 2.5 cm/s for small (Pele) entrained in a megaplume could be advected as far as a few kilometers from a source region. These results indicate that entrainment in buoyant seawater plumes during an eruption may play an important role in clast dispersal, but it is not clear if this mechanism can explain the distribution of volcaniclastic material at the sites on the Gakkel and Juan de Fuca Ridges where our samples were acquired. In order to understand the dispersal of volcaniclastic material in the deep-sea it will be necessary to rigorously characterize existing deposits, and develop models capable of incorporating explosive gas phases into the eruption plume.
A two-layer model for buoyant inertial displacement flows in inclined pipes
Etrati, Ali; Frigaard, Ian A.
2018-02-01
We investigate the inertial flows found in buoyant miscible displacements using a two-layer model. From displacement flow experiments in inclined pipes, it has been observed that for significant ranges of Fr and Re cos β/Fr, a two-layer, stratified flow develops with the heavier fluid moving at the bottom of the pipe. Due to significant inertial effects, thin-film/lubrication models developed for laminar, viscous flows are not effective for predicting these flows. Here we develop a displacement model that addresses this shortcoming. The complete model for the displacement flow consists of mass and momentum equations for each fluid, resulting in a set of four non-linear equations. By integrating over each layer and eliminating the pressure gradient, we reduce the system to two equations for the area and mean velocity of the heavy fluid layer. The wall and interfacial stresses appear as source terms in the reduced system. The final system of equations is solved numerically using a robust, shock-capturing scheme. The equations are stabilized to remove non-physical instabilities. A linear stability analysis is able to predict the onset of instabilities at the interface and together with numerical solution, is used to study displacement effectiveness over different parametric regimes. Backflow and instability onset predictions are made for different viscosity ratios.
Experimental Studies for the characterization of the mixing processes in negative buoyant jets
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Querzoli G.
2013-04-01
Full Text Available A negatively buoyant jet (NBJ corresponds to the physical phenomenon that develops when a fluid is discharged upwards into a lighter environment or downwards into a heavier receptor fluid. In a NBJ the flow is initially driven mostly by the momentum, so it basically behaves as a simple jet released withthe same angle, while far from the outlet the buoyancy prevails, bending the jet axis down and making it similar to a plume. The coexistence in the same phenomenon of both the characteristics of simple jets and plumes makes the NBJs a phenomenon still not entirely explained but, considering also the numerous practical applications, very interesting to study. Here some of the experimental results are presented. The laboratory experiment were obtained on a model simulating a typical sea discharge of brine from desalination plants: a pipe laid down on the sea bottom, with orifices on its lateral wall, releasing brine (heavier than the sea water with a certain angle to the horizontal, in order to increase the jet path before sinking to the seafloor. A non-intrusive image analysis technique, namely Feature Tracking Velocimetry, is applied to measure velocity fields, with the aim at understanding the influence of some non-dimensional parameters driving the phenomenon (e.g. Reynolds number, release angle on the structure of the NBJ and of the turbulence.
An 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.
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.
A corrected vortex blob method for 3D thermal buoyant flows
Energy Technology Data Exchange (ETDEWEB)
Golia, Carmine; Buonomo, Bernardo; Viviani, Antonio [Seconda Universita di Napoli (SUN), Dipartimento di Ingegneria Aerospaziale e Meccanica (DIAM), via Roma 29, 81031 Aversa (Italy)
2008-11-15
This work explores novel ideas to improve the accuracy of integral approximation to differential operators (divergence, gradient and Laplacian) in the simulation of 3D thermal buoyant flows with meshless Lagrangian Blobs methods. Basically, we investigate and develop an integral discretization of the differential operators of the field equations, by using convolutions of truncated 3D-Taylor series expansions with a kernel function defined on a compact support around the blob centre of a given particle. This allows to overtake: circle the irregular distribution of cells in the compact support around the given blob, circle the deficiency of cells in the compact support due to the presence of a boundary cutting the compact support of nearby blobs. The accuracy and the order of approximation of such discretizations are determined in regular and randomly distorted grids of various sizes, and compared with the widely used particle strength exchange formulations. The analysis of the effects of using the new formulations to solve problems at realistic values of the Grashof number demonstrates the validity and the benefits of the novel findings. (author)
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.
Numerical simulation and analysis of confined turbulent buoyant jet with variable source
El-Amin, Mohamed; Al-Ghamdi, Abdulmajeed; Salama, Amgad; Sun, Shuyu
2016-01-01
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-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.
Bhimireddy, Sudheer Reddy; Bhaganagar, Kiran
2016-11-01
Buoyant plumes are common in atmosphere when there exists a difference in temperature or density between the source and its ambience. In a stratified environment, plume rise happens until the buoyancy variation exists between the plume and ambience. In a calm no wind ambience, this plume rise is purely vertical and the entrainment happens because of the relative motion of the plume with ambience and also ambient turbulence. In this study, a plume centroid is defined as the plume mass center and is calculated from the kinematic equation which relates the rate of change of centroids position to the plume rise velocity. Parameters needed to describe the plume are considered as the plume radius, plumes vertical velocity and local buoyancy of the plume. The plume rise velocity is calculated by the mass, momentum and heat conservation equations in their differential form. Our study focuses on the entrainment velocity, as it depicts the extent of plume growth. This entrainment velocity is made up as sum of fractions of plume's relative velocity and ambient turbulence. From the results, we studied the effect of turbulence on the plume growth by observing the variation in the plume radius at different heights and the centroid height reached before loosing its buoyancy.
Trench Advance By the Subduction of Buoyant Features - Application to the Izu-Bonin-Marianas Arc
Goes, S. D. B.; Fourel, L.; Morra, G.
2014-12-01
Most subduction trenches retreat, not only today but throughout the Cenozoic. However, a few trenches clearly advance during part of the evolution, including Izu-Bonin Marianas (IBM) and Kermadec. Trench retreat is well understood as a basic consequence of slab pull, but it is debated what causes trench advance. The IBM trench underwent a complex evolution: right after its initiation, it rotated clockwise, leading to very fast retreat in the north and slow retreat in the south. But since 10-15 Ma, IBM trench motions have switched to advance at the southern end, and since 5 Ma also the northern end is advancing. Based on 2-D subduction models, it has been proposed proposed that the change in age of the subducting plate at the IBM trench (from 40-70 m.y. at the initiation of the trench 45 m.y. ago to 100-140 m.y. lithosphere subducting at the trench today) and its effect on plate strength could explain the transition from trench retreat to trench advance, and that the age gradient (younger in the north and older in the south) could explain the rotation of the trench. However, with new 3-D coupled fluid-solid subduction model where we can include such lateral age gradients, we find that this does not yield the observed behaviour. Instead, we propose an alternative mechanism, involving the subduction of the buoyant Caroline Island Ridge at the southern edge of the Mariana trench and show that it can explain both trench motion history and the current morphology of the IBM slab as imaged by seismic tomography.
THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC SIMULATIONS OF BUOYANT BUBBLES IN GALAXY CLUSTERS
International Nuclear Information System (INIS)
O'Neill, S. M.; De Young, D. S.; Jones, T. W.
2009-01-01
We report results of three-dimensional magnetohydrodynamic 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 and De Young. 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 β = P gas /P mag ∼ 3 can influence the dynamics of the bubbles, provided the fields are not tangled on scales comparable to or smaller than the size of the bubbles. Quasi-uniform, horizontal fields with initial β ∼ 10 2 bifurcated our bubbles before they rose more than about a scale height of the ICM, and substantially weaker fields produced clear distortions. These behaviors resulted from stretching and amplification of ICM fields trapped in irregularities along the top surface of the young bubbles. On the other hand, tangled magnetic fields with similar, modest strengths are generally less easily amplified by the bubble motions and are thus less influential in bubble evolution. Inclusion of a comparably strong, tangled magnetic field inside the initial bubbles had little effect on our bubble evolution, since those fields were quickly diminished through expansion of the bubble and reconnection of the initial field.
Modeling Highly Buoyant Flows in the Castel Giorgio: Torre Alfina Deep Geothermal Reservoir
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Giorgio Volpi
2018-01-01
Full Text Available The Castel Giorgio-Torre Alfina (CG-TA, central Italy is a geothermal reservoir whose fluids are hosted in a carbonate formation at temperatures ranging between 120°C and 210°C. Data from deep wells suggest the existence of convective flow. We present the 3D numerical model of the CG-TA to simulate the undisturbed natural geothermal field and investigate the impacts of the exploitation process. The open source finite-element code OpenGeoSys is applied to solve the coupled systems of partial differential equations. The commercial software FEFLOW® is also used as additional numerical constraint. Calculated pressure and temperature have been calibrated against data from geothermal wells. The flow field displays multicellular convective patterns that cover the entire geothermal reservoir. The resulting thermal plumes protrude vertically over 3 km at Darcy velocity of about 7⁎10-8 m/s. The analysis of the exploitation process demonstrated the sustainability of a geothermal doublet for the development of a 5 MW pilot plant. The buoyant circulation within the geothermal system allows the reservoir to sustain a 50-year production at a flow rate of 1050 t/h. The distance of 2 km, between the production and reinjection wells, is sufficient to prevent any thermal breakthrough within the estimated operational lifetime. OGS and FELFOW results are qualitatively very similar with differences in peak velocities and temperatures. The case study provides valuable guidelines for future exploitation of the CG-TA deep geothermal reservoir.
Self Induced Buoyant Blow Off in Upward Flame Spread on Thin Solid Fuels
Johnston, Michael C.; T'ien, James S.; Muff, Derek E.; Olson, Sandra L.; Ferkul, Paul V.
2013-01-01
) is as follows: The observed one-sided extinction is a blow- off induced by buoyant entrainment. It is known that the flammable diffusion flame regime is bounded by quenching and blow ]off limits when varying incoming air velocity. The narrowest samples tested (between 2 and 5 cm) begin within the flammable range, but as the flame grows, the buoyancy driven air velocity increases at the neighborhood of the flame base. The initially stable flame crosses the extinguishment boundary resulting in a flame blow-off. When one-side of the flame extinguishes, the remaining side shrinks due to the reduced heat transfer to the solid. This reduces the induced velocity and the flame becomes stable. It is proposed that this may have implications to upward flame growth beyond this experiment.
Volpi, Giorgio; Crosta, Giovanni B.; Colucci, Francesca; Fischer, Thomas; Magri, Fabien
2017-04-01
Geothermal heat is a viable source of energy and its environmental impact in terms of CO2 emissions is significantly lower than conventional fossil fuels. However, nowadays its utilization is inconsistent with the enormous amount of energy available underneath the surface of the earth. This is mainly due to the uncertainties associated with it, as for example the lack of appropriate computational tools, necessary to perform effective analyses. The aim of the present study is to build an accurate 3D numerical model, to simulate the exploitation process of the deep geothermal reservoir of Castel Giorgio - Torre Alfina (central Italy), and to compare results and performances of parallel simulations performed with TOUGH2 (Pruess et al. 1999), FEFLOW (Diersch 2014) and the open source software OpenGeoSys (Kolditz et al. 2012). Detailed geological, structural and hydrogeological data, available for the selected area since early 70s, show that Castel Giorgio - Torre Alfina is a potential geothermal reservoir with high thermal characteristics (120 ° C - 150 ° C) and fluids such as pressurized water and gas, mainly CO2, hosted in a carbonate formation. Our two steps simulations firstly recreate the undisturbed natural state of the considered system and then perform the predictive analysis of the industrial exploitation process. The three adopted software showed a strong numerical simulations accuracy, which has been verified by comparing the simulated and measured temperature and pressure values of the geothermal wells in the area. The results of our simulations have demonstrated the sustainability of the investigated geothermal field for the development of a 5 MW pilot plant with total fluids reinjection in the same original formation. From the thermal point of view, a very efficient buoyant circulation inside the geothermal system has been observed, thus allowing the reservoir to support the hypothesis of a 50 years production time with a flow rate of 1050 t
Theoretical analysis and semianalytical solutions for a turbulent buoyant hydrogen-air jet
El-Amin, Mohamed; Sun, S.; Salama, Amgad
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).
Buoyant miscible displacement flow of shear-thinning fluids: Experiments and Simulations
Ale Etrati Khosroshahi, Seyed Ali; Frigaard, Ian
2017-11-01
We study displacement flow of two miscible fluids with density and viscosity contrast in an inclined pipe. Our focus is mainly on displacements where transverse mixing is not significant and thus a two-layer, stratified flow develops. Our experiments are carried out in a long pipe, covering a wide range of flow-rates, inclination angles and viscosity ratios. Density and viscosity contrasts are achieved by adding Glycerol and Xanthan gum to water, respectively. At each angle, flow rate and viscosity ratio are varied and density contrast is fixed. We identify and map different flow regimes, instabilities and front dynamics based on Fr , Re / Frcosβ and viscosity ratio m. The problem is also studied numerically to get a better insight into the flow structure and shear-thinning effects. Numerical simulations are completed using OpenFOAM in both pipe and channel geometries and are compared against the experiments. Schlumberger, NSERC.
Energy Technology Data Exchange (ETDEWEB)
Burns, S.P. [Texas Univ., Austin, TX (United States); Gianoulakis, S.E. [Sandia National Labs., Albuquerque, NM (United States)
1995-07-01
A numerical solution for buoyant natural convection within a square enclosure containing a fluid with highly temperature dependent viscosity is presented. Although the fluid properties employed do not represent any real fluid, the large variation in the fluid viscosity with temperature is characteristic of turbulent flow modeling with eddy-viscosity concepts. Results are obtained using a primitive variable formulation and the resistor method. The results presented include velocity, temperature and pressure distributions within the enclosure as well as shear stress and heat flux distributions along the enclosure walls. Three mesh refinements were employed and uncertainty values are suggested for the final mesh refinement. These solutions are part of a contributed benchmark solution set for the subject problem.
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
Brown, Richard S; Deng, Z Daniel; Cook, Katrina V; Pflugrath, Brett D; Li, Xinya; Fu, Tao; Martinez, Jayson J; Li, Huidong; Trumbo, Bradly A; Ahmann, Martin L; Seaburg, Adam G
2013-01-01
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 confirm this.
Zhang, Wei; He, Zhiguo; Jiang, Houshuo
2017-11-01
Time-resolved particle image velocimetry (PIV) has been used to measure instantaneous two-dimensional velocity vector fields of laboratory-generated turbulent buoyant plumes in linearly stratified saltwater over extended periods of time. From PIV-measured time-series flow data, characteristics of plume mean flow and turbulence have been quantified. To be specific, maximum plume penetration scaling and entrainment coefficient determined from the mean flow agree well with the theory based on the entrainment hypothesis for buoyant plumes in stratified fluids. Besides the well-known persistent entrainment along the plume stem (i.e., the 'plume-stem' entrainment), the mean plume velocity field shows persistent entrainment along the outer edge of the plume cap (i.e., the 'plume-cap' entrainment), thereby confirming predictions from previous numerical simulation studies. To our knowledge, the present PIV investigation provides the first measured flow field data in the plume cap region. As to measured plume turbulence, both the turbulent kinetic energy field and the turbulence dissipation rate field attain their maximum close to the source, while the turbulent viscosity field reaches its maximum within the plume cap region; the results also show that maximum turbulent viscosity scales as νt,max = 0.030(B/N)1/2, where B is source buoyancy flux and N is ambient buoyancy frequency. These PIV data combined with previously published numerical simulation results have implications for understanding the roles of hydrothermal plume turbulence, i.e. plume turbulence within the cap region causes the 'plume-cap' entrainment that plays an equally important role as the 'plume-stem' entrainment in supplying the final volume flux at the plume spreading level.
Velocity and concentration fields in turbulent buoyant mixing in tilted tubes
Znaien, J.; Moisy, F.; Hulin, J. P.; Salin, D.; Hinch, E. J.
2008-11-01
2D PIV and LIF measurements have been performed on buoyancy driven flows of two miscible fluids of the same viscosity in a tube tilted at different angles θ from vertical and at different density contrasts (characterized by the Atwood number At). As θ increases and At decreases, the flow regime evolves, behind the front, from a turbulent shear flow towards a laminar counter flow with 3 layers of different concentrations. Time variations of the structure function show that both intermittent and developed turbulence occur in intermediate conditions. In the turbulent regime (Reλ˜60) the magnitudes of the longitudinal u'^2 and transverse v'^2 velocity fluctuations and of the component u'v' of the Reynolds stress tensor are shown to be largest on the tube axis while viscous stresses is only important close to the walls. The analyzis of the momentum transfer in the flow with buoyancy forces estimated from the concentration gradients demonstrates that 3D effects are required to achieve the momentum balance. These results are discussed in the framework of classical turbulence models.
On the use of the standard k-e turbulence model in GOTHIC to simulate buoyant flows with light gases
International Nuclear Information System (INIS)
Andreani, M.; Smith, B.
2003-01-01
Helium is used as a simulant of hydrogen in tests aiming at reproducing conditions in the containment of a nuclear reactor relevant for severe accident scenarios. In the frame of the TEMPEST Project of the 5 th European Framework Programme, the task to demonstrate that gas distribution results obtained using helium can be considered representative of the behaviour of hydrogen is addressed in a cylindrical vessel geometry using experiments in a mid-scale facility. Scoping test calculations using the GOTHIC code are used for the designing of the tests, which include low-injection velocity conditions. In order to provide trustworthy results, the GOTHIC code was first validated against results for similar conditions obtained in the Large Scale Gas Mixing Facility (LSGMF) in Canada. In particular, it was investigated whether the standard k-ε turbulence model implemented in the code was capable to produce sufficiently accurate results or the RNG variant implemented in an in-house version of the code is more appropriate. This investigation was therefore the occasion to obtain an evaluation of the capabilities of the two turbulence models within the structure of the GOTHIC code to predict the distribution of non-condensables under conditions of low velocity, highly buoyant injections. In general, the standard k-ε turbulence model provided more accurate results
MULTI-PARAMETRIC STUDY OF RISING 3D BUOYANT FLUX TUBES IN AN ADIABATIC STRATIFICATION USING AMR
International Nuclear Information System (INIS)
Martínez-Sykora, Juan; Cheung, Mark C. M.; Moreno-Insertis, Fernando
2015-01-01
We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, magnetohydrodynamic simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vorticity in the main body of the tube of opposite sign on the opposite sides of the apex. This is a consequence of the inhomogeneity of the azimuthal component of the field on the flux surfaces. The lift force associated with this global vorticity makes the flanks of the tube move away from their initial vertical plane in an antisymmetric fashion. The trajectories have an oscillatory motion superimposed, due to the shedding of vortex rolls to the wake, which creates a Von Karman street
MULTI-PARAMETRIC STUDY OF RISING 3D BUOYANT FLUX TUBES IN AN ADIABATIC STRATIFICATION USING AMR
Energy Technology Data Exchange (ETDEWEB)
Martínez-Sykora, Juan; Cheung, Mark C. M. [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States); Moreno-Insertis, Fernando [Instituto de Astrofísica de Canarias, E-38200 La Laguna (Tenerife) (Spain)
2015-11-20
We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, magnetohydrodynamic simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vorticity in the main body of the tube of opposite sign on the opposite sides of the apex. This is a consequence of the inhomogeneity of the azimuthal component of the field on the flux surfaces. The lift force associated with this global vorticity makes the flanks of the tube move away from their initial vertical plane in an antisymmetric fashion. The trajectories have an oscillatory motion superimposed, due to the shedding of vortex rolls to the wake, which creates a Von Karman street.
International Nuclear Information System (INIS)
Chock, D.P.; Winkler, S.L.; Pu Sun
2002-01-01
We have introduced a new and elaborate approach to understand the impact of grid resolution and subgrid chemistry assumption on the grid-model prediction of species concentrations for a system with highly non-homogeneous chemistry - a reactive buoyant plume immediately downwind of the stack in a convective boundary layer. The Parcel-Grid approach plume was used to describe both the air parcel turbulent transport and chemistry. This approach allows an identical transport process for all simulations. It also allows a description of subgrid chemistry. The ambient and plume parcel transport follows the description of Luhar and Britter (Atmos. Environ, 23 (1989) 1911, 26A (1992) 1283). The chemistry follows that of the Carbon-Bond mechanism. Three different grid sizes were considered: fine, medium and coarse, together with three different subgrid chemistry assumptions: micro-scale or individual parcel, tagged-parcel (plume and ambient parcels treated separately), and untagged-parcel (plume and ambient parcels treated indiscriminately). Reducing the subgrid information is not necessarily similar to increasing the model grid size. In our example, increasing the grid size leads to a reduction in the suppression of ozone in the presence of a high-NO x stack plume, and a reduction in the effectiveness of the NO x -inhibition effect. On the other hand, reducing the subgrid information (by using the untagged-parcel assumption) leads to an increase in ozone reduction and an enhancement of the NO x -inhibition effect insofar as the ozone extremum is concerned. (author)
International Nuclear Information System (INIS)
Fazey, Francesca M.C.; Ryan, Peter G.
2016-01-01
Recent estimates suggest that roughly 100 times more plastic litter enters the sea than is found floating at the sea surface, despite the buoyancy and durability of many plastic polymers. Biofouling by marine biota is one possible mechanism responsible for this discrepancy. Microplastics (<5 mm in diameter) are more scarce than larger size classes, which makes sense because fouling is a function of surface area whereas buoyancy is a function of volume; the smaller an object, the greater its relative surface area. We tested whether plastic items with high surface area to volume ratios sank more rapidly by submerging 15 different sizes of polyethylene samples in False Bay, South Africa, for 12 weeks to determine the time required for samples to sink. All samples became sufficiently fouled to sink within the study period, but small samples lost buoyancy much faster than larger ones. There was a direct relationship between sample volume (buoyancy) and the time to attain a 50% probability of sinking, which ranged from 17 to 66 days of exposure. Our results provide the first estimates of the longevity of different sizes of plastic debris at the ocean surface. Further research is required to determine how fouling rates differ on free floating debris in different regions and in different types of marine environments. Such estimates could be used to improve model predictions of the distribution and abundance of floating plastic debris globally. - Highlights: • We tested how fragment size affects the rate of buoyancy loss at sea due to biofouling for two low-density plastic polymers. • We found a strong direct relationship between fragment size and surface longevity. • Our longevity estimates ranged from 17 days for the thinnest microplastics to 66 days for thicker macroplastics. • Our results provide the first estimates of the longevity of different sizes of plastic debris at the ocean surface. • The results could be used to improve model predictions of the
Stefanescu, Doru M.; Moitra, Avijit; Kacar, A. Sedat; Dhindaw, Brij K.
1990-01-01
Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or siliconcarbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which considers process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.
Lazeroms, Werner M. J.; Jenkins, Adrian; Hilmar Gudmundsson, G.; van de Wal, Roderik S. W.
2018-01-01
Basal melting below ice shelves is a major factor in mass loss from the Antarctic Ice Sheet, which can contribute significantly to possible future sea-level rise. Therefore, it is important to have an adequate description of the basal melt rates for use in ice-dynamical models. Most current ice models use rather simple parametrizations based on the local balance of heat between ice and ocean. In this work, however, we use a recently derived parametrization of the melt rates based on a buoyant meltwater plume travelling upward beneath an ice shelf. This plume parametrization combines a non-linear ocean temperature sensitivity with an inherent geometry dependence, which is mainly described by the grounding-line depth and the local slope of the ice-shelf base. For the first time, this type of parametrization is evaluated on a two-dimensional grid covering the entire Antarctic continent. In order to apply the essentially one-dimensional parametrization to realistic ice-shelf geometries, we present an algorithm that determines effective values for the grounding-line depth and basal slope in any point beneath an ice shelf. Furthermore, since detailed knowledge of temperatures and circulation patterns in the ice-shelf cavities is sparse or absent, we construct an effective ocean temperature field from observational data with the purpose of matching (area-averaged) melt rates from the model with observed present-day melt rates. Our results qualitatively replicate large-scale observed features in basal melt rates around Antarctica, not only in terms of average values, but also in terms of the spatial pattern, with high melt rates typically occurring near the grounding line. The plume parametrization and the effective temperature field presented here are therefore promising tools for future simulations of the Antarctic Ice Sheet requiring a more realistic oceanic forcing.
Imhof, Hannes K; Laforsch, Christian
2016-11-01
Microplastic has been ubiquitously detected in freshwater ecosystems. A variety of freshwater organisms were shown to ingest microplastic particles, while a high potential for adverse effects are expected. However, studies addressing the effect of microplastic in freshwater species are still scarce compared to studies on marine organisms. In order to gain further insights into possible adverse effects of microplastic particles on freshwater invertebrates and to set the base for further experiments we exposed the mud snail (Potampoyrgus antipodarum) to a large range of common and environmentally relevant non-buoyant polymers (polyamide, polyethylene terephthalate, polycarbonate, polystyrene, polyvinylchloride). The impact of these polymers was tested by performing two exposure experiments with irregular shaped microplastic particles with a broad size distribution in a low (30%) and a high microplastic dose (70%) in the food. First, possible effects on adult P. antipodarum were assessed by morphological and life-history parameters. Second, the effect of the same mixture on the development of juvenile P. antipodarum until maturity was analyzed. Adult P. antipodarum showed no morphological changes after the exposure to the microplastic particles, even if supplied in a high dose. Moreover, although P. antipodarum is an established model organism and reacts especially sensitive to endocrine active substances no effects on embryogenesis were detected. Similarly, the juvenile development until maturity was not affected. Considering, that most studies showing effects on marine and freshwater invertebrates mostly exposed their experimental organisms to very small (≤20 μm) polystyrene microbeads, we anticipate that these effects may be highly dependent on the chemical composition of the polymer itself and the size and shape of the particles. Therefore, more studies are necessary to enable the identification of harmful synthetic polymers as some of them may be
Strom, K.; Rouhnia, M.
2016-12-01
Previous studies have suggested that sedimentation from buoyant, muddy plumes lofting over clear saltwater can take place at rates higher than that expected from individual particle settling (i.e., CWs). Two potential drivers of enhanced sedimentation are flocculation and interfacial instabilities. We experimentally measured the sediment fluxes from each of these processes using two sets of laboratory experiments that investigate two different modes of instability, one driven by sediment settling and one driven by fluid shear. The settling-driven and shear-driven instability experiments were carried out in a stagnant stratification tank and a stratification flume respectively. In both sets, continuous interface monitoring and concentration measurements were made to observe developments of instabilities and their effects on the removal of sediment. Floc size was measured during the experiments using a floc camera and image analysis routines. This presentation will provide an overview of the stagnant tank experiments, but will focus on results from the stratified flume experiments and an analysis that attempts to synthesizes the results from the entirety of the study. The results from the stratified flume experiments show that under shear instabilities, the effective settling velocity is greater than the floc settling velocity, and that the rate increases with plume velocity and interface mixing. The difference between effective and floc settling velocity was denoted as the shear-induced settling velocity. This rate was found to be a strong function of the Richardson number, and was attributed to mixing processes at the interface. Conceptual and empirical analysis shows that the shear-induced settling velocity is proportional to URi-2. The resulting effective settling velocity models developed from these experiments are then used to examine the rates and potential locations of operations of these mechanism over the length of a river mouth plume.
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...
Kelley, M. C.; Haerendel, G.; Kappler, H.; Valenzuela, A.; Balsley, B. B.; Carter, D. A.; Ecklund, W. L.; Carlson, C. W.; Haeusler, B.; Torbert, R.
1976-01-01
Recent rocket probe, barium cloud and radar measurements conducted during equatorial spread F conditions are interpreted in terms of a Rayleigh-Taylor gravitational instability operating on the bottomside of the F peak. The persistent theoretical problems associated with strong radar echoes typically observed in patch-like structures at high altitudes are explained in terms of regions of depleted plasma density which buoyantly rise against the gravitational field.
National Research Council Canada - National Science Library
Gerhard, Erich M
2008-01-01
.... For instance, in one embodiment two oppositely extending curves each float and each are pressed by the water in a balanced manner to provide a stable platform for one or more antennas which can be...
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....
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.
Krohn, Benedikt; Manera, Annalisa; Petrov, Victor
2018-04-01
Turbulent mixing in stratified environments represents a challenging task in experimental turbulence research, especially when large density gradients are desired. When optical measurement techniques like particle image velocimetry (PIV) are applied to stratified liquids, it is common practice to combine two aqueous solutions with different density but equal refractive index, to suppress particle image deflections. While refractive image matching (RIM) has been developed in the late 1970s, the achieved limit of 4% density ratio was not rivalled up to day. In the present work, we report a methodology, based on the behavior of excess properties and their change in a multicomponent system while mixing, that allows RIM for solutions with higher density differences. The methodology is then successfully demonstrated using a ternary combination of water, isopropanol and glycerol, for which RIM in presence of a density ratio of 8.6% has been achieved. Qualitative PIV results of a turbulent buoyant jet with 8.6% density ratio are shown.
Energy Technology Data Exchange (ETDEWEB)
Eschbach, E.J.; Enderlin, C.W.
1993-10-01
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.
International Nuclear Information System (INIS)
Hanna, S.R.; Chang, J.C.
1997-01-01
The HGSYSTEM/UF 6 model was developed for use in preparing Safety Analysis Reports (SARs) by estimating the consequences of possible accidental releases of UF 6 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/UF 6 to account for flow and dispersion around buildings. The original HGSYSTEM/UF 6 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)
Eschbach, E.J.; Enderlin, C.W.
1993-10-01
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
Stochastic transport models for mixing in variable-density turbulence
Bakosi, J.; Ristorcelli, J. R.
2011-11-01
In variable-density (VD) turbulent mixing, where very-different- density materials coexist, the density fluctuations can be an order of magnitude larger than their mean. Density fluctuations are non-negligible in the inertia terms of the Navier-Stokes equation which has both quadratic and cubic nonlinearities. Very different mixing rates of different materials give rise to large differential accelerations and some fundamentally new physics that is not seen in constant-density turbulence. In VD flows material mixing is active in a sense far stronger than that applied in the Boussinesq approximation of buoyantly-driven flows: the mass fraction fluctuations are coupled to each other and to the fluid momentum. Statistical modeling of VD mixing requires accounting for basic constraints that are not important in the small-density-fluctuation passive-scalar-mixing approximation: the unit-sum of mass fractions, bounded sample space, and the highly skewed nature of the probability densities become essential. We derive a transport equation for the joint probability of mass fractions, equivalent to a system of stochastic differential equations, that is consistent with VD mixing in multi-component turbulence and consistently reduces to passive scalar mixing in constant-density flows.
... 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 ...
International Nuclear Information System (INIS)
Ignatyuk, A.V.
1998-01-01
For any applications of the statistical theory of nuclear reactions it is very important to obtain the parameters of the level density description from the reliable experimental data. The cumulative numbers of low-lying levels and the average spacings between neutron resonances are usually used as such data. The level density parameters fitted to such data are compiled in the RIPL Starter File for the tree models most frequently used in practical calculations: i) For the Gilber-Cameron model the parameters of the Beijing group, based on a rather recent compilations of the neutron resonance and low-lying level densities and included into the beijing-gc.dat file, are chosen as recommended. As alternative versions the parameters provided by other groups are given into the files: jaeri-gc.dat, bombay-gc.dat, obninsk-gc.dat. Additionally the iljinov-gc.dat, and mengoni-gc.dat files include sets of the level density parameters that take into account the damping of shell effects at high energies. ii) For the backed-shifted Fermi gas model the beijing-bs.dat file is selected as the recommended one. Alternative parameters of the Obninsk group are given in the obninsk-bs.dat file and those of Bombay in bombay-bs.dat. iii) For the generalized superfluid model the Obninsk group parameters included into the obninsk-bcs.dat file are chosen as recommended ones and the beijing-bcs.dat file is included as an alternative set of parameters. iv) For the microscopic approach to the level densities the files are: obninsk-micro.for -FORTRAN 77 source for the microscopical statistical level density code developed in Obninsk by Ignatyuk and coworkers, moller-levels.gz - Moeller single-particle level and ground state deformation data base, moller-levels.for -retrieval code for Moeller single-particle level scheme. (author)
International Nuclear Information System (INIS)
Wells, BE; Meyer, P.E.; Chen, G.
2000-01-01
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
Magmatic densities control erupted volumes in Icelandic volcanic systems
Hartley, Margaret; Maclennan, John
2018-04-01
Magmatic density and viscosity exert fundamental controls on the eruptibility of magmas. In this study, we investigate the extent to which magmatic physical properties control the eruptibility of magmas from Iceland's Northern Volcanic Zone (NVZ). By studying subaerial flows of known age and volume, we are able to directly relate erupted volumes to magmatic physical properties, a task that has been near-impossible when dealing with submarine samples dredged from mid-ocean ridges. We find a strong correlation between magmatic density and observed erupted volumes on the NVZ. Over 85% of the total volume of erupted material lies close to a density and viscosity minimum that corresponds to the composition of basalts at the arrival of plagioclase on the liquidus. These magmas are buoyant with respect to the Icelandic upper crust. However, a number of small-volume eruptions with densities greater than typical Icelandic upper crust are also found in Iceland's neovolcanic zones. We use a simple numerical model to demonstrate that the eruption of magmas with higher densities and viscosities is facilitated by the generation of overpressure in magma chambers in the lower crust and uppermost mantle. This conclusion is in agreement with petrological constraints on the depths of crystallisation under Iceland.
Magmatic Densities Control Erupted Volumes in Icelandic Volcanic Systems
Directory of Open Access Journals (Sweden)
Margaret Hartley
2018-04-01
Full Text Available Magmatic density and viscosity exert fundamental controls on the eruptibility of magmas. In this study, we investigate the extent to which magmatic physical properties control the eruptibility of magmas from Iceland's Northern Volcanic Zone (NVZ. By studying subaerial flows of known age and volume, we are able to directly relate erupted volumes to magmatic physical properties, a task that has been near-impossible when dealing with submarine samples dredged from mid-ocean ridges. We find a strong correlation between magmatic density and observed erupted volumes on the NVZ. Over 85% of the total volume of erupted material lies close to a density and viscosity minimum that corresponds to the composition of basalts at the arrival of plagioclase on the liquidus. These magmas are buoyant with respect to the Icelandic upper crust. However, a number of small-volume eruptions with densities greater than typical Icelandic upper crust are also found in Iceland's neovolcanic zones. We use a simple numerical model to demonstrate that the eruption of magmas with higher densities and viscosities is facilitated by the generation of overpressure in magma chambers in the lower crust and uppermost mantle. This conclusion is in agreement with petrological constraints on the depths of crystallization under Iceland.
Nayak, Binaya Bhusan; Kamiya, Eriko; Nishino, Tomohiko; Wada, Minoru; Nishimura, Masahiko; Kogure, Kazuhiro
2005-01-01
The co-existence of physiologically different cells in bacterial cultures is a general phenomenon. We have examined the applicability of the density dependent cell sorting (DDCS) method to separate subpopulations from a long-term starvation culture of Vibrio parahaemolyticus. The cells were subjected to Percoll density gradient and separated into 12 fractions of different buoyant densities, followed by measuring the cell numbers, culturability, respiratory activity and leucine incorporation activity. While more than 78% of cells were in lighter fractions, about 95% of culturable cells were present in heavier fractions. The high-density subpopulations also had high proportion of cells capable of forming formazan granules. Although this was accompanied by the cell specific INT-reduction rate, both leucine incorporation rates and INT-reduction rates per cell had a peak at mid-density fraction. The present results indicated that DDCS could be used to separate subpopulations of different physiological conditions.
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.
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.
International Nuclear Information System (INIS)
Stoner, J.O. Jr.
1991-01-01
The densities of arc-evaporated carbon target foils have been measured by several methods. The density depends upon the method used to measure it; for the same surface density, values obtained by different measurement techniques may differ by fifty percent or more. The most reliable density measurements are by flotation, yielding a density of 2.01±0.03 g cm -3 , and interferometric step height with the surface density known from auxiliary measurements, yielding a density of 2.61±0.4 g cm -3 . The difference between these density values mayy be due in part to the compressive stresses that carbon films have while still on their substrates, uncertainties in the optical calibration of surface densities of carbon foils, and systematic errors in step-height measurements. Mechanical thickness measurements by micrometer caliper are unreliable due to nonplanarity of these foils. (orig.)
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...
Achieving maximum baryon densities
International Nuclear Information System (INIS)
Gyulassy, M.
1984-01-01
In continuing work on nuclear stopping power in the energy range E/sub lab/ approx. 10 GeV/nucleon, calculations were made of the energy and baryon densities that could be achieved in uranium-uranium collisions. Results are shown. The energy density reached could exceed 2 GeV/fm 3 and baryon densities could reach as high as ten times normal nuclear densities
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…
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....
Why Density Dependent Propulsion?
Robertson, Glen A.
2011-01-01
In 2004 Khoury and Weltman produced a density dependent cosmology theory they call the Chameleon, as at its nature, it is hidden within known physics. The Chameleon theory has implications to dark matter/energy with universe acceleration properties, which implies a new force mechanism with ties to the far and local density environment. In this paper, the Chameleon Density Model is discussed in terms of propulsion toward new propellant-less engineering methods.
International Nuclear Information System (INIS)
Tendler, M.
1984-06-01
The energy loss from a tokamak plasma due to neutral hydrogen radiation and recycling is of great importance for the energy balance at the periphery. It is shown that the requirement for thermal equilibrium implies a constraint on the maximum attainable edge density. The relation to other density limits is discussed. The average plasma density is shown to be a strong function of the refuelling deposition profile. (author)
International Nuclear Information System (INIS)
Grimes, S.M.
2005-01-01
Recent research in the area of nuclear level densities is reviewed. The current interest in nuclear astrophysics and in structure of nuclei off of the line of stability has led to the development of radioactive beam facilities with larger machines currently being planned. Nuclear level densities for the systems used to produce the radioactive beams influence substantially the production rates of these beams. The modification of level-density parameters near the drip lines would also affect nucleosynthesis rates and abundances
International Nuclear Information System (INIS)
Carr-Brion, K.G.; Keen, E.F.
1982-01-01
System for determining the true density of a fluent mixture such as a liquid slurry, containing entrained gas, such as air comprises a restriction in pipe through which at least a part of the mixture is passed. Density measuring means such as gamma-ray detectors and source measure the apparent density of the mixture before and after its passage through the restriction. Solid-state pressure measuring devices are arranged to measure the pressure in the mixture before and after its passage through the restriction. Calculating means, such as a programmed microprocessor, determine the true density from these measurements using relationships given in the description. (author)
On density forecast evaluation
Diks, C.
2008-01-01
Traditionally, probability integral transforms (PITs) have been popular means for evaluating density forecasts. For an ideal density forecast, the PITs should be uniformly distributed on the unit interval and independent. However, this is only a necessary condition, and not a sufficient one, as
Learning Grasp Affordance Densities
DEFF Research Database (Denmark)
Detry, Renaud; Kraft, Dirk; Kroemer, Oliver
2011-01-01
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......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...
Lazzeretti, Paolo
2018-04-01
It is shown that nonsymmetric second-rank current density tensors, related to the current densities induced by magnetic fields and nuclear magnetic dipole moments, are fundamental properties of a molecule. Together with magnetizability, nuclear magnetic shielding, and nuclear spin-spin coupling, they completely characterize its response to magnetic perturbations. Gauge invariance, resolution into isotropic, deviatoric, and antisymmetric parts, and contributions of current density tensors to magnetic properties are discussed. The components of the second-rank tensor properties are rationalized via relationships explicitly connecting them to the direction of the induced current density vectors and to the components of the current density tensors. The contribution of the deviatoric part to the average value of magnetizability, nuclear shielding, and nuclear spin-spin coupling, uniquely determined by the antisymmetric part of current density tensors, vanishes identically. The physical meaning of isotropic and anisotropic invariants of current density tensors has been investigated, and the connection between anisotropy magnitude and electron delocalization has been discussed.
Demonstration of de novo synthesis of enzymes by density labelling with stable isotopes
International Nuclear Information System (INIS)
Huebner, G.; Hirschberg, K.
1977-01-01
The technique of in vivo density labelling of proteins with H 2 18 O and 2 H 2 O has been used to investigate hormonal regulation and developmental expression of enzymes in plant cells. Buoyant density data obtained from isopycnic equilibrium centrifugation demonstrated that the cytokinine-induced nitrate reductase activity and the gibberellic acid-induced phosphatase activity in isolated embryos of Agrostemma githago are activities of enzymes synthesized de novo. The increase in alanine-specific aminopeptidase in germinating A. githago seeds is not due to de novo synthesis but to the release of preformed enzyme. On the basis of this result it is possible to apply the enzyme aminopeptidase as an internal density standard in equilibrium centrifugation. Density labelling experiments on proteins in pea cotyledons have been used to study the change in the activity of acid phosphatase, alanine-specific aminopeptidase, and peroxidase during germination. The activities of these enzymes increase in cotyledons of Pisum sativum. Density labelling by 18 O and 2 H demonstrates de novo synthesis of these three enzymes. The differential time course of enzyme induction shows the advantage of using H 2 18 O as labelling substance in cases when the enzyme was synthesized immediately at the beginning of germination. At this stage of development the amino-acid pool available for synthesis is formed principally by means of hydrolysis of storage proteins. The incorporation of 2 H into the new proteins takes place in a measurable amount at a stage of growth in which the amino acids are also synthesized de novo. The enzyme acid phosphatase of pea cotyledons was chosen to demonstrate the possibility of using the density labelling technique to detect protein turnover. (author)
International Nuclear Information System (INIS)
Engel, J.
2007-01-01
The Hohenberg-Kohn theorem and Kohn-Sham procedure are extended to functionals of the localized intrinsic density of a self-bound system such as a nucleus. After defining the intrinsic-density functional, we modify the usual Kohn-Sham procedure slightly to evaluate the mean-field approximation to the functional, and carefully describe the construction of the leading corrections for a system of fermions in one dimension with a spin-degeneracy equal to the number of particles N. Despite the fact that the corrections are complicated and nonlocal, we are able to construct a local Skyrme-like intrinsic-density functional that, while different from the exact functional, shares with it a minimum value equal to the exact ground-state energy at the exact ground-state intrinsic density, to next-to-leading order in 1/N. We briefly discuss implications for real Skyrme functionals
International Nuclear Information System (INIS)
Das, M.P.
1984-07-01
The state of the art of the density functional formalism (DFT) is reviewed. The theory is quantum statistical in nature; its simplest version is the well-known Thomas-Fermi theory. The DFT is a powerful formalism in which one can treat the effect of interactions in inhomogeneous systems. After some introductory material, the DFT is outlined from the two basic theorems, and various generalizations of the theorems appropriate to several physical situations are pointed out. Next, various approximations to the density functionals are presented and some practical schemes, discussed; the approximations include an electron gas of almost constant density and an electron gas of slowly varying density. Then applications of DFT in various diverse areas of physics (atomic systems, plasmas, liquids, nuclear matter) are mentioned, and its strengths and weaknesses are pointed out. In conclusion, more recent developments of DFT are indicated
Low Density Supersonic Decelerators
National Aeronautics and Space Administration — The Low-Density Supersonic Decelerator project will demonstrate the use of inflatable structures and advanced parachutes that operate at supersonic speeds to more...
density functional theory approach
Indian Academy of Sciences (India)
YOGESH ERANDE
2017-07-27
Jul 27, 2017 ... a key role in all optical switching devices, since their optical properties can be .... optimized in the gas phase using Density Functional Theory. (DFT).39 The ...... The Mediation of Electrostatic Effects by Sol- vents J. Am. Chem.
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, especially of ...
Density scaling for multiplets
International Nuclear Information System (INIS)
Nagy, A
2011-01-01
Generalized Kohn-Sham equations are presented for lowest-lying multiplets. The way of treating non-integer particle numbers is coupled with an earlier method of the author. The fundamental quantity of the theory is the subspace density. The Kohn-Sham equations are similar to the conventional Kohn-Sham equations. The difference is that the subspace density is used instead of the density and the Kohn-Sham potential is different for different subspaces. The exchange-correlation functional is studied using density scaling. It is shown that there exists a value of the scaling factor ζ for which the correlation energy disappears. Generalized OPM and Krieger-Li-Iafrate (KLI) methods incorporating correlation are presented. The ζKLI method, being as simple as the original KLI method, is proposed for multiplets.
International Nuclear Information System (INIS)
Maslov, V.M.
1998-01-01
Fission level densities (or fissioning nucleus level densities at fission saddle deformations) are required for statistical model calculations of actinide fission cross sections. Back-shifted Fermi-Gas Model, Constant Temperature Model and Generalized Superfluid Model (GSM) are widely used for the description of level densities at stable deformations. These models provide approximately identical level density description at excitations close to the neutron binding energy. It is at low excitation energies that they are discrepant, while this energy region is crucial for fission cross section calculations. A drawback of back-shifted Fermi gas model and traditional constant temperature model approaches is that it is difficult to include in a consistent way pair correlations, collective effects and shell effects. Pair, shell and collective properties of nucleus do not reduce just to the renormalization of level density parameter a, but influence the energy dependence of level densities. These effects turn out to be important because they seem to depend upon deformation of either equilibrium or saddle-point. These effects are easily introduced within GSM approach. Fission barriers are another key ingredients involved in the fission cross section calculations. Fission level density and barrier parameters are strongly interdependent. This is the reason for including fission barrier parameters along with the fission level densities in the Starter File. The recommended file is maslov.dat - fission barrier parameters. Recent version of actinide fission barrier data obtained in Obninsk (obninsk.dat) should only be considered as a guide for selection of initial parameters. These data are included in the Starter File, together with the fission barrier parameters recommended by CNDC (beijing.dat), for completeness. (author)
International Nuclear Information System (INIS)
Belblidia, L.A.; Bratianu, C.
1979-01-01
Boiling flow in a steam generator, a water-cooled reactor, and other multiphase processes can be subject to instabilities. It appears that the most predominant instabilities are the so-called density-wave oscillations. They can cause difficulties for three main reasons; they may induce burnout; they may cause mechanical vibrations of components; and they create system control problems. A comprehensive review is presented of experimental and theoretical studies concerning density-wave oscillations. (author)
International Nuclear Information System (INIS)
Stankus, S.V.; Basin, A.S.
1983-01-01
Results are presented for measurements of the density of metallic ytterbium in the liquid state and at the liquid-solid phase transition. Based on the numerical data obtained, the coefficient of thermal expansion βZ of the liquid and the density discontinuity on melting deltarho/sub m/ are calculated. The magnitudes of βZ and deltarho/sub m/ for the heavy lanthanides are compared
International Nuclear Information System (INIS)
Igor Kaganovich
2000-01-01
Negative ions tend to stratify in electronegative plasmas with hot electrons (electron temperature Te much larger than ion temperature Ti, Te > Ti ). The boundary separating a plasma containing negative ions, and a plasma, without negative ions, is usually thin, so that the negative ion density falls rapidly to zero-forming a negative ion density front. We review theoretical, experimental and numerical results giving the spatio-temporal evolution of negative ion density fronts during plasma ignition, the steady state, and extinction (afterglow). During plasma ignition, negative ion fronts are the result of the break of smooth plasma density profiles during nonlinear convection. In a steady-state plasma, the fronts are boundary layers with steepening of ion density profiles due to nonlinear convection also. But during plasma extinction, the ion fronts are of a completely different nature. Negative ions diffuse freely in the plasma core (no convection), whereas the negative ion front propagates towards the chamber walls with a nearly constant velocity. The concept of fronts turns out to be very effective in analysis of plasma density profile evolution in strongly non-isothermal plasmas
Xue, Xinzhi; Katz, Joseph
2017-11-01
Very little experimental data exits on the flow structure in the near field of a crude oil jet fragmenting in water because of inability to probe dense droplet cloud. Refractive index-matching is applied to overcome this challenge by using silicone oil and sugar water as a surrogate liquid pair. Their density ratio, viscosity ratio, and interfacial tension are closely matched with those of crude oil and seawater. Simultaneous PLIF and PIV measurements are conducted by fluorescently tagging the oil and seeding both phases with particles. With increasing jet Reynolds and Weber numbers, the oil plume breakup occurs closer to the nozzle, the spreading angle of the jet increases, and the droplet sizes decrease. The varying spread rate is attributed to differences in droplet size distributions. The location of primary oil breakup is consistent with the region of high strain rate fluctuations. What one may perceive as oil droplets in opaque fluids actually consists of multi-layers containing water droplets, which sometimes encapsulate smaller oil droplets, creating a ``Russian Doll'' like phenomenon. This system forms as ligaments of oil and water wrap around each other during entrainment. Results include profiles of mean velocity and turbulence parameters along with energy spectra. Gulf of Mexico Research Inititave.
International Nuclear Information System (INIS)
Vaeth, W.
1979-04-01
The correlation of signal components at different frequencies like higher harmonics cannot be detected by a normal power spectral density measurement, since this technique correlates only components at the same frequency. This paper describes a special method for measuring the correlation of two signal components at different frequencies: the CRISS power spectral density. From this new function in frequency analysis, the correlation of two components can be determined quantitatively either they stem from one signal or from two diverse signals. The principle of the method, suitable for the higher harmonics of a signal as well as for any other frequency combinations is shown for the digital frequency analysis technique. Two examples of CRISS power spectral densities demonstrates the operation of the new method. (orig.) [de
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
International Nuclear Information System (INIS)
Hofman, G.L.
1996-01-01
A fuel development campaign that results in an aluminum plate-type fuel of unlimited LEU burnup capability with an uranium loading of 9 grams per cm 3 of meat should be considered an unqualified success. The current worldwide approved and accepted highest loading is 4.8 g cm -3 with U 3 Si 2 as fuel. High-density uranium compounds offer no real density advantage over U 3 Si 2 and have less desirable fabrication and performance characteristics as well. Of the higher-density compounds, U 3 Si has approximately a 30% higher uranium density but the density of the U 6 X compounds would yield the factor 1.5 needed to achieve 9 g cm -3 uranium loading. Unfortunately, irradiation tests proved these peritectic compounds have poor swelling behavior. It is for this reason that the authors are turning to uranium alloys. The reason pure uranium was not seriously considered as a dispersion fuel is mainly due to its high rate of growth and swelling at low temperatures. This problem was solved at least for relatively low burnup application in non-dispersion fuel elements with small additions of Si, Fe, and Al. This so called adjusted uranium has nearly the same density as pure α-uranium and it seems prudent to reconsider this alloy as a dispersant. Further modifications of uranium metal to achieve higher burnup swelling stability involve stabilization of the cubic γ phase at low temperatures where normally α phase exists. Several low neutron capture cross section elements such as Zr, Nb, Ti and Mo accomplish this in various degrees. The challenge is to produce a suitable form of fuel powder and develop a plate fabrication procedure, as well as obtain high burnup capability through irradiation testing
Levinson, N
1940-01-01
A typical gap theorem of the type discussed in the book deals with a set of exponential functions { \\{e^{{{i\\lambda}_n} x}\\} } on an interval of the real line and explores the conditions under which this set generates the entire L_2 space on this interval. A typical gap theorem deals with functions f on the real line such that many Fourier coefficients of f vanish. The main goal of this book is to investigate relations between density and gap theorems and to study various cases where these theorems hold. The author also shows that density- and gap-type theorems are related to various propertie
International Nuclear Information System (INIS)
Cardoso Junior, J.L.
1982-10-01
Experimental data show that the number of nuclear states increases rapidly with increasing excitation energy. The properties of highly excited nuclei are important for many nuclear reactions, mainly those that go via processes of the compound nucleus type. In this case, it is sufficient to know the statistical properties of the nuclear levels. First of them is the function of nuclear levels density. Several theoretical models which describe the level density are presented. The statistical mechanics and a quantum mechanics formalisms as well as semi-empirical results are analysed and discussed. (Author) [pt
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...
Holographic magnetisation density waves
Energy Technology Data Exchange (ETDEWEB)
Donos, Aristomenis [Centre for Particle Theory and Department of Mathematical Sciences, Durham University,Stockton Road, Durham, DH1 3LE (United Kingdom); Pantelidou, Christiana [Departament de Fisica Quantica i Astrofisica & Institut de Ciencies del Cosmos (ICC),Universitat de Barcelona,Marti i Franques 1, 08028 Barcelona (Spain)
2016-10-10
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.
Metamorphic core complex formation by density inversion and lower-crust extrusion.
Martinez, F; Goodliffe, A M; Taylor, B
2001-06-21
Metamorphic core complexes are domal uplifts of metamorphic and plutonic rocks bounded by shear zones that separate them from unmetamorphosed cover rocks. Interpretations of how these features form are varied and controversial, and include models involving extension on low-angle normal faults, plutonic intrusions and flexural rotation of initially high-angle normal faults. The D'Entrecasteaux islands of Papua New Guinea are actively forming metamorphic core complexes located within a continental rift that laterally evolves to sea-floor spreading. The continental rifting is recent (since approximately 6 Myr ago), seismogenic and occurring at a rapid rate ( approximately 25 mm yr-1). Here we present evidence-based on isostatic modelling, geological data and heat-flow measurements-that the D'Entrecasteaux core complexes accommodate extension through the vertical extrusion of ductile lower-crust material, driven by a crustal density inversion. Although buoyant extrusion is accentuated in this region by the geological structure present-which consists of dense ophiolite overlaying less-dense continental crust-this mechanism may be generally applicable to regions where thermal expansion lowers crustal density with depth.
Indian Academy of Sciences (India)
best known for developing the density functional theory (DFT). This is an extremely ... lem that has become famous in popular culture is that of the planet. Tatooine. Fans of ... the Schrödinger equation (or, if relativistic effects are important, the Dirac .... it supplies a moral justification for one's subsequent endeav- ours along ...
Nesin, Gert; Barrow, Lloyd H.
1984-01-01
Describes a fourth-grade unit on density which introduces a concept useful in the study of chemistry and procedures appropriate to the chemistry laboratory. The hands-on activities, which use simple equipment and household substances, are at the level of thinking Piaget describes as concrete operational. (BC)
Seewaldt, Victoria L.
2012-01-01
The identification of a signalling protein that regulates the accumulation of fat and connective tissue in breasts may help to explain why high mammographic density is linked to breast-cancer risk and may provide a marker for predicting this risk.
DEFF Research Database (Denmark)
Reinholdt, Peter; Kongsted, Jacob; Olsen, Jógvan Magnus Haugaard
2017-01-01
We analyze the performance of the polarizable density embedding (PDE) model-a new multiscale computational approach designed for prediction and rationalization of general molecular properties of large and complex systems. We showcase how the PDE model very effectively handles the use of large...
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...
International Nuclear Information System (INIS)
Aydin, Alhun; Sisman, Altug
2016-01-01
By considering the quantum-mechanically minimum allowable energy interval, we exactly count number of states (NOS) and introduce discrete density of states (DOS) concept for a particle in a box for various dimensions. Expressions for bounded and unbounded continua are analytically recovered from discrete ones. Even though substantial fluctuations prevail in discrete DOS, they're almost completely flattened out after summation or integration operation. It's seen that relative errors of analytical expressions of bounded/unbounded continua rapidly decrease for high NOS values (weak confinement or high energy conditions), while the proposed analytical expressions based on Weyl's conjecture always preserve their lower error characteristic. - Highlights: • Discrete density of states considering minimum energy difference is proposed. • Analytical DOS and NOS formulas based on Weyl conjecture are given. • Discrete DOS and NOS functions are examined for various dimensions. • Relative errors of analytical formulas are much better than the conventional ones.
Energy Technology Data Exchange (ETDEWEB)
Aydin, Alhun; Sisman, Altug, E-mail: sismanal@itu.edu.tr
2016-03-22
By considering the quantum-mechanically minimum allowable energy interval, we exactly count number of states (NOS) and introduce discrete density of states (DOS) concept for a particle in a box for various dimensions. Expressions for bounded and unbounded continua are analytically recovered from discrete ones. Even though substantial fluctuations prevail in discrete DOS, they're almost completely flattened out after summation or integration operation. It's seen that relative errors of analytical expressions of bounded/unbounded continua rapidly decrease for high NOS values (weak confinement or high energy conditions), while the proposed analytical expressions based on Weyl's conjecture always preserve their lower error characteristic. - Highlights: • Discrete density of states considering minimum energy difference is proposed. • Analytical DOS and NOS formulas based on Weyl conjecture are given. • Discrete DOS and NOS functions are examined for various dimensions. • Relative errors of analytical formulas are much better than the conventional ones.
Density dependent effective interactions
International Nuclear Information System (INIS)
Dortmans, P.J.; Amos, K.
1994-01-01
An effective nucleon-nucleon interaction is defined by an optimal fit to select on-and half-off-of-the-energy shell t-and g-matrices determined by solutions of the Lippmann-Schwinger and Brueckner-Bethe-Goldstone equations with the Paris nucleon-nucleon interaction as input. As such, it is seen to better reproduce the interaction on which it is based than other commonly used density dependent effective interactions. The new (medium modified) effective interaction when folded with appropriate density matrices, has been used to define proton- 12 C and proton- 16 O optical potentials. With them elastic scattering data are well fit and the medium effects identifiable. 23 refs., 8 figs
Variable Kernel Density Estimation
Terrell, George R.; Scott, David W.
1992-01-01
We investigate some of the possibilities for improvement of univariate and multivariate kernel density estimates by varying the window over the domain of estimation, pointwise and globally. Two general approaches are to vary the window width by the point of estimation and by point of the sample observation. The first possibility is shown to be of little efficacy in one variable. In particular, nearest-neighbor estimators in all versions perform poorly in one and two dimensions, but begin to b...
Density oscillations within hadrons
International Nuclear Information System (INIS)
Arnold, R.; Barshay, S.
1976-01-01
In models of extended hadrons, in which small bits of matter carrying charge and effective mass exist confined within a medium, oscillations in the matter density may occur. A way of investigating this possibility experimentally in high-energy hadron-hadron elastic diffraction scattering is suggested, and the effect is illustrated by examining some existing data which might be relevant to the question [fr
Toward a Redefinition of Density
Rapoport, Amos
1975-01-01
This paper suggests that in addition to the recent work indicating that crowding is a subjective phenomenon, an adequate definition of density must also include a subjective component since density is a complex phenomenon in itself. Included is a discussion of both physical density and perceived density. (Author/MA)
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.
Density Distribution Sunflower Plots
Directory of Open Access Journals (Sweden)
William D. Dupont
2003-01-01
Full Text Available Density distribution sunflower plots are used to display high-density bivariate data. They are useful for data where a conventional scatter plot is difficult to read due to overstriking of the plot symbol. The x-y plane is subdivided into a lattice of regular hexagonal bins of width w specified by the user. The user also specifies the values of l, d, and k that affect the plot as follows. Individual observations are plotted when there are less than l observations per bin as in a conventional scatter plot. Each bin with from l to d observations contains a light sunflower. Other bins contain a dark sunflower. In a light sunflower each petal represents one observation. In a dark sunflower, each petal represents k observations. (A dark sunflower with p petals represents between /2-pk k and /2+pk k observations. The user can control the sizes and colors of the sunflowers. By selecting appropriate colors and sizes for the light and dark sunflowers, plots can be obtained that give both the overall sense of the data density distribution as well as the number of data points in any given region. The use of this graphic is illustrated with data from the Framingham Heart Study. A documented Stata program, called sunflower, is available to draw these graphs. It can be downloaded from the Statistical Software Components archive at http://ideas.repec.org/c/boc/bocode/s430201.html . (Journal of Statistical Software 2003; 8 (3: 1-5. Posted at http://www.jstatsoft.org/index.php?vol=8 .
International Nuclear Information System (INIS)
Porter, M.R.; Foster, J.M.; Hodson, A.L.; Hazen, W.E.; Hendel, A.Z.; Bull, R.M.
1982-01-01
Measurements of the differential local density spectrum have been made using a 1 m 2 discharge chamber mounted in the Leeds discharge chamber array. The results are fitted to a power law of the form h(δ)dδ = kδsup(-ν)dδ, where ν=2.47+-0.04; k=0.21 s - 1 , for 7 m - 2 - 2 ; ν=2.90+-0.22; k=2.18 s - 1 , for δ > 200 m - 2 . Details of the measurement techniques are given with particular reference to the treatment of closely-spaced discharges. A comparison of these results with previous experiments using different techniques is made
Measurement of loose powder density
International Nuclear Information System (INIS)
Akhtar, S.; Ali, A.; Haider, A.; Farooque, M.
2011-01-01
Powder metallurgy is a conventional technique for making engineering articles from powders. Main objective is to produce final products with the highest possible uniform density, which depends on the initial loose powder characteristics. Producing, handling, characterizing and compacting materials in loose powder form are part of the manufacturing processes. Density of loose metallic or ceramic powder is an important parameter for die design. Loose powder density is required for calculating the exact mass of powder to fill the die cavity for producing intended green density of the powder compact. To fulfill this requirement of powder metallurgical processing, a loose powder density meter as per ASTM standards is designed and fabricated for measurement of density. The density of free flowing metallic powders can be determined using Hall flow meter funnel and density cup of 25 cm/sup 3/ volume. Density of metal powders like cobalt, manganese, spherical bronze and pure iron is measured and results are obtained with 99.9% accuracy. (author)
International Nuclear Information System (INIS)
Ayala, A.L.
1996-01-01
In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial 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 and estimate the value of the shadowing corrections in this case. Then 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. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab
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.
Anomalous evolution of Ar metastable density with electron density in high density Ar discharge
International Nuclear Information System (INIS)
Park, Min; Chang, Hong-Young; You, Shin-Jae; Kim, Jung-Hyung; Shin, Yong-Hyeon
2011-01-01
Recently, an anomalous evolution of argon metastable density with plasma discharge power (electron density) was reported [A. M. Daltrini, S. A. Moshkalev, T. J. Morgan, R. B. Piejak, and W. G. Graham, Appl. Phys. Lett. 92, 061504 (2008)]. Although the importance of the metastable atom and its density has been reported in a lot of literature, however, a basic physics behind the anomalous evolution of metastable density has not been clearly understood yet. In this study, we investigated a simple global model to elucidate the underlying physics of the anomalous evolution of argon metastable density with the electron density. On the basis of the proposed simple model, we reproduced the anomalous evolution of the metastable density and disclosed the detailed physics for the anomalous result. Drastic changes of dominant mechanisms for the population and depopulation processes of Ar metastable atoms with electron density, which take place even in relatively low electron density regime, is the clue to understand the result.
Richardson effects in turbulent buoyant flows
Biggi, Renaud; Blanquart, Guillaume
2010-11-01
Rayleigh Taylor instabilities are found in a wide range of scientific fields from supernova explosions to underwater hot plumes. The turbulent flow is affected by the presence of buoyancy forces and may not follow the Kolmogorov theory anymore. The objective of the present work is to analyze the complex interactions between turbulence and buoyancy. Towards that goal, simulations have been performed with a high order, conservative, low Mach number code [Desjardins et. al. JCP 2010]. The configuration corresponds to a cubic box initially filled with homogeneous isotropic turbulence with heavy fluid on top and light gas at the bottom. The initial turbulent field was forced using linear forcing up to a Reynolds number of Reλ=55 [Meneveau & Rosales, POF 2005]. The Richardson number based on the rms velocity and the integral length scale was varied from 0.1 to 10 to investigate cases with weak and strong buoyancy. Cases with gravity as a stabilizer of turbulence (gravity pointing up) were also considered. The evolution of the turbulent kinetic energy and the total kinetic energy was analyzed and a simple phenomenological model was proposed. Finally, the energy spectra and the isotropy of the flow were also investigated.
Near field characteristics of buoyant helium plumes
Indian Academy of Sciences (India)
pressure tubing. Helium gas enters the bottom of the settling chamber, passing through two ... A 40 mesh, flat stainless steel screen is placed across the orifice exit. ... PIV and PLIF measurements are carried out in phase resolved manner.
International Nuclear Information System (INIS)
Szasz, L.; Berrios-Pagan, I.; McGinn, G.
1975-01-01
A new Density-Functional formula is constructed for atoms. The kinetic energy of the electron is divided into two parts: the kinetic self-energy and the orthogonalization energy. Calculations were made for the total energies of neutral atoms, positive ions and for the He isoelectronic series. For neutral atoms the results match the Hartree-Fock energies within 1% for atoms with N 36 the results generally match the HF energies within 0.1%. For positive ions the results are fair; for the molecular applications a simplified model is developed in which the kinetic energy consists of the Weizsaecker term plus the Fermi energy reduced by a continuous function. (orig.) [de
International Nuclear Information System (INIS)
Freyss, M.
2015-01-01
This chapter gives an introduction to first-principles electronic structure calculations based on the density functional theory (DFT). Electronic structure calculations have a crucial importance in the multi-scale modelling scheme of materials: not only do they enable one to accurately determine physical and chemical properties of materials, they also provide data for the adjustment of parameters (or potentials) in higher-scale methods such as classical molecular dynamics, kinetic Monte Carlo, cluster dynamics, etc. Most of the properties of a solid depend on the behaviour of its electrons, and in order to model or predict them it is necessary to have an accurate method to compute the electronic structure. DFT is based on quantum theory and does not make use of any adjustable or empirical parameter: the only input data are the atomic number of the constituent atoms and some initial structural information. The complicated many-body problem of interacting electrons is replaced by an equivalent single electron problem, in which each electron is moving in an effective potential. DFT has been successfully applied to the determination of structural or dynamical properties (lattice structure, charge density, magnetisation, phonon spectra, etc.) of a wide variety of solids. Its efficiency was acknowledged by the attribution of the Nobel Prize in Chemistry in 1998 to one of its authors, Walter Kohn. A particular attention is given in this chapter to the ability of DFT to model the physical properties of nuclear materials such as actinide compounds. The specificities of the 5f electrons of actinides will be presented, i.e., their more or less high degree of localisation around the nuclei and correlations. The limitations of the DFT to treat the strong 5f correlations are one of the main issues for the DFT modelling of nuclear fuels. Various methods that exist to better treat strongly correlated materials will finally be presented. (author)
Hormonal Determinants of Mammographic Density
National Research Council Canada - National Science Library
Simpson, Jennifer K; Modugno, Francemary; Weissfeld, Joel L; Kuller, Lewis; Vogel, Victor; Constantino, Joseph P
2005-01-01
.... However, not all women on HRT will experience an increase in breast density. We propose a novel hypothesis to explain in part the individual variability in breast density seen among women on HRT...
Density limit in ASDEX discharges with peaked density profiles
International Nuclear Information System (INIS)
Staebler, A.; Niedermeyer, H.; Loch, R.; Mertens, V.; Mueller, E.R.; Soeldner, F.X.; Wagner, F.
1989-01-01
Results concerning the density limit in OH and NI-heated ASDEX discharges with the usually observed broad density profiles have been reported earlier: In ohmic discharges with high q a (q-cylindrical is used throughout this paper) the Murakami parameter (n e R/B t ) is a good scaling parameter. At the high densities edge cooling is observed causing the plasma to shrink until an m=2-instability terminates the discharge. When approaching q a =2 the density limit is no longer proportional to I p ; a minimum exists in n e,max (q a ) at q a ∼2.15. With NI-heating the density limit increases less than proportional to the heating power; the behaviour during the pre-disruptive phase is rather similar to the one of OH discharges. There are specific operating regimes on ASDEX leading to discharges with strongly peaked density profiles: the improved ohmic confinement regime, counter neutral injection, and multipellet injection. These regimes are characterized by enhanced energy and particle confinement. The operational limit in density for these discharges is, therefore, of great interest having furthermore in mind that high central densities are favourable in achieving high fusion yields. In addition, further insight into the mechanisms of the density limit observed in tokamaks may be obtained by comparing plasmas with rather different density profiles at their maximum attainable densities. 7 refs., 2 figs
Smoothing densities under shape constraints
Davies, Paul Laurie; Meise, Monika
2009-01-01
In Davies and Kovac (2004) the taut string method was proposed for calculating a density which is consistent with the data and has the minimum number of peaks. The main disadvantage of the taut string density is that it is piecewise constant. In this paper a procedure is presented which gives a smoother density by minimizing the total variation of a derivative of the density subject to the number, positions and heights of the local extreme values obtained from the taut string density. 2...
High density hydrogen research
International Nuclear Information System (INIS)
Hawke, R.S.
1977-01-01
The interest in the properties of very dense hydrogen is prompted by its abundance in Saturn and Jupiter and its importance in laser fusion studies. Furthermore, it has been proposed that the metallic form of hydrogen may be a superconductor at relatively high temperatures and/or exist in a metastable phase at ambient pressure. For ten years or more, laboratories have been developing the techniques to study hydrogen in the megabar region (1 megabar = 100 GPa). Three major approaches to study dense hydrogen experimentally have been used, static presses, shockwave compression, and magnetic compression. Static tchniques have crossed the megabar threshold in stiff materials but have not yet been convincingly successful in very compressible hydrogen. Single and double shockwave techniques have improved the precision of the pressure, volume, temperature Equation of State (EOS) of molecular hydrogen (deuterium) up to near 1 Mbar. Multiple shockwave and magnetic techniques have compressed hydrogen to several megabars and densities in the range of the metallic phase. The net result is that hydrogen becomes conducting at a pressure between 2 and 4 megabars. Hence, the possibility of making a significant amount of hydrogen into a metal in a static press remains a formidable challenge. The success of such experiments will hopefully answer the questions about hydrogen's metallic vs. conducting molecular phase, superconductivity, and metastability. 4 figures, 15 references
Emad, Ahmed; Drouin, Régen
2014-09-01
Physical separation by density gradient centrifugation (DGC) is usually used as an initial step of multistep enrichment protocols for purification of fetal cells (FCs) from maternal blood. Many protocols were designed but no single approach was efficient enough to provide noninvasive prenatal diagnosis. Procedures and methods were difficult to compare because of the nonuniformity of protocols among different groups. Recovery of FCs is jeopardized by their loss during the process of enrichment. Any loss of FCs must be minimized because of the multiplicative effect of each step of the enrichment process. The main objective of this study was to evaluate FC loss caused by DGC. Fetal cells were quantified in peripheral blood samples obtained from both euploid and aneuploid pregnancies before and after enrichment by buoyant DGC using Histopaque 1.119 g/mL. Density gradient centrifugation results in major loss of 60% to 80% of rare FCs, which may further complicate subsequent enrichment procedures. Eliminating aggressive manipulations can significantly minimize FC loss. Data obtained raise questions about the appropriateness of the DGC step for the enrichment of rare FCs and argues for the use of the alternative nonaggressive version of the procedure presented here or prioritizing other methods of enrichments. © 2014 John Wiley & Sons, Ltd.
Density limit experiments on FTU
International Nuclear Information System (INIS)
Pucella, G.; Tudisco, O.; Apicella, M.L.; Apruzzese, G.; Artaserse, G.; Belli, F.; Boncagni, L.; Botrugno, A.; Buratti, P.; Calabrò, G.; Castaldo, C.; Cianfarani, C.; Cocilovo, V.; Dimatteo, L.; Esposito, B.; Frigione, D.; Gabellieri, L.; Giovannozzi, E.; Bin, W.; Granucci, G.
2013-01-01
One of the main problems in tokamak fusion devices concerns the capability to operate at a high plasma density, which is observed to be limited by the appearance of catastrophic events causing loss of plasma confinement. The commonly used empirical scaling law for the density limit is the Greenwald limit, predicting that the maximum achievable line-averaged density along a central chord depends only on the average plasma current density. However, the Greenwald density limit has been exceeded in tokamak experiments in the case of peaked density profiles, indicating that the edge density is the real parameter responsible for the density limit. Recently, it has been shown on the Frascati Tokamak Upgrade (FTU) that the Greenwald density limit is exceeded in gas-fuelled discharges with a high value of the edge safety factor. In order to understand this behaviour, dedicated density limit experiments were performed on FTU, in which the high density domain was explored in a wide range of values of plasma current (I p = 500–900 kA) and toroidal magnetic field (B T = 4–8 T). These experiments confirm the edge nature of the density limit, as a Greenwald-like scaling holds for the maximum achievable line-averaged density along a peripheral chord passing at r/a ≃ 4/5. On the other hand, the maximum achievable line-averaged density along a central chord does not depend on the average plasma current density and essentially depends on the toroidal magnetic field only. This behaviour is explained in terms of density profile peaking in the high density domain, with a peaking factor at the disruption depending on the edge safety factor. The possibility that the MARFE (multifaced asymmetric radiation from the edge) phenomenon is the cause of the peaking has been considered, with the MARFE believed to form a channel for the penetration of the neutral particles into deeper layers of the plasma. Finally, the magnetohydrodynamic (MHD) analysis has shown that also the central line
Resolvability of regional density structure
Plonka, A.; Fichtner, A.
2016-12-01
Lateral density variations are the source of mass transport in the Earth at all scales, acting as drivers of convectivemotion. However, the density structure of the Earth remains largely unknown since classic seismic observables and gravityprovide only weak constraints with strong trade-offs. Current density models are therefore often based on velocity scaling,making strong assumptions on the origin of structural heterogeneities, which may not necessarily be correct. Our goal is to assessif 3D density structure may be resolvable with emerging full-waveform inversion techniques. We have previously quantified the impact of regional-scale crustal density structure on seismic waveforms with the conclusion that reasonably sized density variations within thecrust can leave a strong imprint on both travel times and amplitudes, and, while this can produce significant biases in velocity and Q estimates, the seismic waveform inversion for density may become feasible. In this study we performprincipal component analyses of sensitivity kernels for P velocity, S velocity, and density. This is intended to establish theextent to which these kernels are linearly independent, i.e. the extent to which the different parameters may be constrainedindependently. Since the density imprint we observe is not exclusively linked to travel times and amplitudes of specific phases,we consider waveform differences between complete seismograms. We test the method using a known smooth model of the crust and seismograms with clear Love and Rayleigh waves, showing that - as expected - the first principal kernel maximizes sensitivity to SH and SV velocity structure, respectively, and that the leakage between S velocity, P velocity and density parameter spaces is minimal in the chosen setup. Next, we apply the method to data from 81 events around the Iberian Penninsula, registered in total by 492 stations. The objective is to find a principal kernel which would maximize the sensitivity to density
Super liquid density target designs
International Nuclear Information System (INIS)
Pan, Y.L.; Bailey, D.S.
1976-01-01
The success of laser fusion depends on obtaining near isentropic compression of fuel to very high densities and igniting this fuel. To date, the results of laser fusion experiments have been based mainly on the exploding pusher implosion of fusion capsules consisting of thin glass microballoons (wall thickness of less than 1 micron) filled with low density DT gas (initial density of a few mg/cc). Maximum DT densities of a few tenths of g/cc and temperatures of a few keV have been achieved in these experiments. We will discuss the results of LASNEX target design calculations for targets which: (a) can compress fuel to much higher densities using the capabilities of existing Nd-glass systems at LLL; (b) allow experimental measurement of the peak fuel density achieved
Kascak, Daniel J.
2004-01-01
With the growing concerns of global warming, the need for pollution-free vehicles is ever increasing. Pollution-free flight is one of NASA's goals for the 21" Century. , One method of approaching that goal is hydrogen-fueled aircraft that use fuel cells or turbo- generators to develop electric power that can drive electric motors that turn the aircraft's propulsive fans or propellers. Hydrogen fuel would likely be carried as a liquid, stored in tanks at its boiling point of 20.5 K (-422.5 F). Conventional electric motors, however, are far too heavy (for a given horsepower) to use on aircraft. Fortunately the liquid hydrogen fuel can provide essentially free refrigeration that can be used to cool the windings of motors before the hydrogen is used for fuel. Either High Temperature Superconductors (HTS) or high purity metals such as copper or aluminum may be used in the motor windings. Superconductors have essentially zero electrical resistance to steady current. The electrical resistance of high purity aluminum or copper near liquid hydrogen temperature can be l/lOO* or less of the room temperature resistance. These conductors could provide higher motor efficiency than normal room-temperature motors achieve. But much more importantly, these conductors can carry ten to a hundred times more current than copper conductors do in normal motors operating at room temperature. This is a consequence of the low electrical resistance and of good heat transfer coefficients in boiling LH2. Thus the conductors can produce higher magnetic field strengths and consequently higher motor torque and power. Designs, analysis and actual cryogenic motor tests show that such cryogenic motors could produce three or more times as much power per unit weight as turbine engines can, whereas conventional motors produce only 1/5 as much power per weight as turbine engines. This summer work has been done with Litz wire to maximize the current density. The current is limited by the amount of heat it
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 ...
Transition densities with electron scattering
International Nuclear Information System (INIS)
Heisenberg, J.
1985-01-01
This paper reviews the ground state and transition charge densities in nuclei via electron scattering. Using electrons as a spectroscopic tool in nuclear physics, these transition densities can be determined with high precision, also in the nuclear interior. These densities generally ask for a microscopic interpretation in terms of contributions from individual nucleons. The results for single particle transitions confirm the picture of particle-phonon coupling. (Auth.)
Sets with Prescribed Arithmetic Densities
Czech Academy of Sciences Publication Activity Database
Luca, F.; Pomerance, C.; Porubský, Štefan
2008-01-01
Roč. 3, č. 2 (2008), s. 67-80 ISSN 1336-913X R&D Projects: GA ČR GA201/07/0191 Institutional research plan: CEZ:AV0Z10300504 Keywords : generalized arithmetic density * generalized asymptotic density * generalized logarithmic density * arithmetical semigroup * weighted arithmetic mean * ratio set * R-dense set * Axiom A * delta-regularly varying function Subject RIV: BA - General Mathematics
Histogram Estimators of Bivariate Densities
National Research Council Canada - National Science Library
Husemann, Joyce A
1986-01-01
One-dimensional fixed-interval histogram estimators of univariate probability density functions are less efficient than the analogous variable-interval estimators which are constructed from intervals...
Importing low-density ideas to high-density revitalisation
DEFF Research Database (Denmark)
Arnholtz, Jens; Ibsen, Christian Lyhne; Ibsen, Flemming
2016-01-01
Why did union officials from a high-union-density country like Denmark choose to import an organising strategy from low-density countries such as the US and the UK? Drawing on in-depth interviews with key union officials and internal documents, the authors of this article argue two key points. Fi...
Mammography density estimation with automated volumetic breast density measurement
International Nuclear Information System (INIS)
Ko, Su Yeon; Kim, Eun Kyung; Kim, Min Jung; Moon, Hee Jung
2014-01-01
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.
The Density of Sustainable Settlements
DEFF Research Database (Denmark)
Lauring, Michael; Silva, Victor; Jensen, Ole B.
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...
Options for refractive index and viscosity matching to study variable density flows
Clément, Simon A.; Guillemain, Anaïs; McCleney, Amy B.; Bardet, Philippe M.
2018-02-01
Variable density flows are often studied by mixing two miscible aqueous solutions of different densities. To perform optical diagnostics in such environments, the refractive index of the fluids must be matched, which can be achieved by carefully choosing the two solutes and the concentration of the solutions. To separate the effects of buoyancy forces and viscosity variations, it is desirable to match the viscosity of the two solutions in addition to their refractive index. In this manuscript, several pairs of index matched fluids are compared in terms of viscosity matching, monetary cost, and practical use. Two fluid pairs are studied in detail, with two aqueous solutions (binary solutions of water and a salt or alcohol) mixed into a ternary solution. In each case: an aqueous solution of isopropanol mixed with an aqueous solution of sodium chloride (NaCl) and an aqueous solution of glycerol mixed with an aqueous solution of sodium sulfate (Na_2SO_4). The first fluid pair allows reaching high-density differences at low cost, but brings a large difference in dynamic viscosity. The second allows matching dynamic viscosity and refractive index simultaneously, at reasonable cost. For each of these four solutes, the density, kinematic viscosity, and refractive index are measured versus concentration and temperature, as well as wavelength for the refractive index. To investigate non-linear effects when two index-matched, binary solutions are mixed, the ternary solutions formed are also analyzed. Results show that density and refractive index follow a linear variation with concentration. However, the viscosity of the isopropanol and NaCl pair deviates from the linear law and has to be considered. Empirical correlations and their coefficients are given to create index-matched fluids at a chosen temperature and wavelength. Finally, the effectiveness of the refractive index matching is illustrated with particle image velocimetry measurements performed for a buoyant jet in a
International Nuclear Information System (INIS)
Mishra, V.; Boukharouba, N.; Brient, C.E.; Grimes, S.M.; Pedroni, R.S.
1994-01-01
Levels in 57 Co have been studied in the region of resolved levels (E 57 Fe(p,n) 57 Co neutron spectrum with resolution ΔE∼5 keV. Seventeen previously unknown levels are located. Level density parameters in the continuum region are deduced from thick target measurements of the same reaction and additional level density information is deduced from Ericson fluctuation studies of the reaction 56 Fe(p,n) 56 Co. A set of level density parameters is found which describes the level density of 57 Co at energies up to 14 MeV. Efforts to obtain level density information from the 56 Fe(d,n) 57 Co reaction were unsuccessful, but estimates of the fraction of the deuteron absorption cross section corresponding to compound nucleus formation are obtained
International Nuclear Information System (INIS)
Balonis, M.; Glasser, F.P.
2009-01-01
The densities of principal crystalline phases occurring in Portland cement are critically assessed and tabulated, in some cases with addition of new data. A reliable and self-consistent density set for crystalline phases was obtained by calculating densities from crystallographic data and unit cell contents. Independent laboratory work was undertaken to synthesize major AFm and AFt cement phases, determine their unit cell parameters and compare the results with those recorded in the literature. Parameters were refined from powder diffraction patterns using CELREF 2 software. A density value is presented for each phase, showing literature sources, in some cases describing limitations on the data, and the weighting attached to numerical values where an averaging process was used for accepted data. A brief discussion is made of the consequences of the packing of water to density changes in AFm and AFt structures.
Obesity and Regional Immigrant Density.
Emerson, Scott D; Carbert, Nicole S
2017-11-24
Canada has an increasingly large immigrant population. Areas of higher immigrant density, may relate to immigrants' health through reduced acculturation to Western foods, greater access to cultural foods, and/or promotion of salubrious values/practices. It is unclear, however, whether an association exists between Canada-wide regional immigrant density and obesity among immigrants. Thus, we examined whether regional immigrant density was related to obesity, among immigrants. Adult immigrant respondents (n = 15,595) to a national population-level health survey were merged with region-level immigrant density data. Multi-level logistic regression was used to model the odds of obesity associated with increased immigrant density. The prevalence of obesity among the analytic sample was 16%. Increasing regional immigrant density was associated with lower odds of obesity among minority immigrants and long-term white immigrants. Immigrant density at the region-level in Canada may be an important contextual factor to consider when examining obesity among immigrants.
Density dependent hadron field theory
International Nuclear Information System (INIS)
Fuchs, C.; Lenske, H.; Wolter, H.H.
1995-01-01
A fully covariant approach to a density dependent hadron field theory is presented. The relation between in-medium NN interactions and field-theoretical meson-nucleon vertices is discussed. The medium dependence of nuclear interactions is described by a functional dependence of the meson-nucleon vertices on the baryon field operators. As a consequence, the Euler-Lagrange equations lead to baryon rearrangement self-energies which are not obtained when only a parametric dependence of the vertices on the density is assumed. It is shown that the approach is energy-momentum conserving and thermodynamically consistent. Solutions of the field equations are studied in the mean-field approximation. Descriptions of the medium dependence in terms of the baryon scalar and vector density are investigated. Applications to infinite nuclear matter and finite nuclei are discussed. Density dependent coupling constants obtained from Dirac-Brueckner calculations with the Bonn NN potentials are used. Results from Hartree calculations for energy spectra, binding energies, and charge density distributions of 16 O, 40,48 Ca, and 208 Pb are presented. Comparisons to data strongly support the importance of rearrangement in a relativistic density dependent field theory. Most striking is the simultaneous improvement of charge radii, charge densities, and binding energies. The results indicate the appearance of a new ''Coester line'' in the nuclear matter equation of state
Measuring single-cell density.
Grover, William H; Bryan, Andrea K; Diez-Silva, Monica; Suresh, Subra; Higgins, John M; Manalis, Scott R
2011-07-05
We have used a microfluidic mass sensor to measure the density of single living cells. By weighing each cell in two fluids of different densities, our technique measures the single-cell mass, volume, and density of approximately 500 cells per hour with a density precision of 0.001 g mL(-1). We observe that the intrinsic cell-to-cell variation in density is nearly 100-fold smaller than the mass or volume variation. As a result, we can measure changes in cell density indicative of cellular processes that would be otherwise undetectable by mass or volume measurements. Here, we demonstrate this with four examples: identifying Plasmodium falciparum malaria-infected erythrocytes in a culture, distinguishing transfused blood cells from a patient's own blood, identifying irreversibly sickled cells in a sickle cell patient, and identifying leukemia cells in the early stages of responding to a drug treatment. These demonstrations suggest that the ability to measure single-cell density will provide valuable insights into cell state for a wide range of biological processes.
Attractor comparisons based on density
International Nuclear Information System (INIS)
Carroll, T. L.
2015-01-01
Recognizing a chaotic attractor can be seen as a problem in pattern recognition. Some feature vector must be extracted from the attractor and used to compare to other attractors. The field of machine learning has many methods for extracting feature vectors, including clustering methods, decision trees, support vector machines, and many others. In this work, feature vectors are created by representing the attractor as a density in phase space and creating polynomials based on this density. Density is useful in itself because it is a one dimensional function of phase space position, but representing an attractor as a density is also a way to reduce the size of a large data set before analyzing it with graph theory methods, which can be computationally intensive. The density computation in this paper is also fast to execute. In this paper, as a demonstration of the usefulness of density, the density is used directly to construct phase space polynomials for comparing attractors. Comparisons between attractors could be useful for tracking changes in an experiment when the underlying equations are too complicated for vector field modeling
Energy vs. density on paths toward more exact density functionals.
Kepp, Kasper P
2018-03-14
Recently, the progression toward more exact density functional theory has been questioned, implying a need for more formal ways to systematically measure progress, i.e. a "path". Here I use the Hohenberg-Kohn theorems and the definition of normality by Burke et al. to define a path toward exactness and "straying" from the "path" by separating errors in ρ and E[ρ]. A consistent path toward exactness involves minimizing both errors. Second, a suitably diverse test set of trial densities ρ' can be used to estimate the significance of errors in ρ without knowing the exact densities which are often inaccessible. To illustrate this, the systems previously studied by Medvedev et al., the first ionization energies of atoms with Z = 1 to 10, the ionization energy of water, and the bond dissociation energies of five diatomic molecules were investigated using CCSD(T)/aug-cc-pV5Z as benchmark at chemical accuracy. Four functionals of distinct designs was used: B3LYP, PBE, M06, and S-VWN. For atomic cations regardless of charge and compactness up to Z = 10, the energy effects of the different ρ are energy-wise insignificant. An interesting oscillating behavior in the density sensitivity is observed vs. Z, explained by orbital occupation effects. Finally, it is shown that even large "normal" problems such as the Co-C bond energy of cobalamins can use simpler (e.g. PBE) trial densities to drastically speed up computation by loss of a few kJ mol -1 in accuracy. The proposed method of using a test set of trial densities to estimate the sensitivity and significance of density errors of functionals may be useful for testing and designing new balanced functionals with more systematic improvement of densities and energies.
International Nuclear Information System (INIS)
Kamada, Yutaka; Hosogane, Nobuyuki; Hirayama, Toshio; Tsunematsu, Toshihide
1990-05-01
This report studies mainly the density limit for a series of gas- and pellet-fuelled limiter discharges in JT-60. With the pellet injection into high-current/low-q (q(a)=2.3∼2.5) discharges, the Murakami factor reaches up to 10∼13 x 10 19 m -2 T -1 . The values are about factors of 1.5∼2.0 higher than those for usual gas-fuelled discharges. The pellet injected discharges have high central density, whereas the electron density in the outer region (a/2 abs and n e 2 (r=50 cm) x Z eff (r=50 cm). (author)
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
Magnetothermopower in unconventional density waves
International Nuclear Information System (INIS)
Dora, B.; Maki, K.; Vanyolos, A.; Virosztek, A.
2003-10-01
After a brief introduction on unconventional density waves (i.e. unconventional charge density wave (UCDW) and unconventional spin density wave (USDW)), we discuss the magnetotransport of the low temperature phase (LTP) of α-(BEDT-TTF) 2 KHg(SCN) 4 . Recently we have proposed that the low temperature phase in α-(BEDT-TTF) 2 KHg(SCN 4 should be UCDW. Here we show that UCDW describes very consistently the magnetothermopower of )α-(BEDT-TTF) 2 KHg(SCN) 4 observed by Choi et al. (author)
Chung, B H; Segrest, J P; Franklin, F
1998-12-01
As a model for the formation of beta-very low density lipoproteins (VLDL) and small, dense LDL by the intraplasma metabolic activities in vivo, lipoproteins in fresh plasma were interacted in vitro with endogenous lecithin:cholesterol acyltransferase (LCAT) and cholesterylester transfer proteins (CETP) and subsequently with purified lipoprotein lipase (LpL). The LCAT and CETP reactions in a mildly hypertriglyceridemic (HTG) plasma at 37 degrees C for 18 h resulted in (1) esterification of about 45% plasma unesterified cholesterol (UC), (2) a marked increase in cholesterylester (CE) (+129%) and a decrease in triglyceride (TG) (-45%) in VLDL, and (3) a marked increase of TG (+ 341%) with a small net decrease of CE (-3.6%) in LDL, causing a significant alteration in the TG/CE of VLDL (from 8.0 to 1.9) and of LDL (from 0.20 to 0.93). The LDL in LCAT and CETP-reacted plasma is larger and more buoyant than that in control plasma. In vitro lipolysis of control and LCAT and CETP-reacted plasma by LpL, which hydrolyzed >90% of VLDL-TG and about 50-60% of LDL-TG, converted most of VLDL in control plasma (>85%) but less than half (40%) of VLDL in LCAT and CETP-reacted plasma into the IDL-LDL density fraction and transformed the large, buoyant LDL in the LCAT and CETP-reacted plasma into particles smaller and denser than those in the control plasma. The remnants that accumulated in the VLDL density region of the postlipolysis LCAT and CETP-reacted plasma contained apo B-100 and E but little or no detectable apo Cs and consisted of particles having pre-beta and beta-electrophoretic mobilities. The inhibition of LCAT during incubation of plasma, which lessened the extent of alteration in VLDL and LDL core lipids, increased the extent of lipolytic removal of VLDL from the VLDL density region but lowered the extent of alteration in the size and density of LDL. The LCAT, CETP and/or LpL-mediated alterations in the density of LDL in normolipidemic fasting plasma were less pronounced
FOREWORD: Special issue on density
Fujii, Kenichi
2004-04-01
This special issue on density was undertaken to provide readers with an overview of the present state of the density standards for solids, liquids and gases, as well as the technologies developed for measuring density. This issue also includes topics on the refractive index of gases and on techniques used for calibrating hydrometers so that almost all areas concerned with density standards are covered in four review articles and seven original articles, most of which describe current research being conducted at national metrology institutes (NMIs). A review article was invited from the Ruhr-Universität Bochum to highlight research on the magnetic suspension densimeters. In metrology, the determinations of the volume of a weight and the density of air are of primary importance in establishing a mass standard because the effect of the buoyancy force of air acting on the weight must be known accurately to determine the mass of the weight. A density standard has therefore been developed at many NMIs with a close relation to the mass standard. Hydrostatic weighing is widely used to measure the volume of a solid. The most conventional hydrostatic weighing method uses water as a primary density standard for measuring the volume of a solid. A brief history of the determination of the density of water is therefore given in a review article, as well as a recommended value for the density of water with a specified isotopic abundance. The most modern technique for hydrostatic weighing uses a solid density standard instead of water. For this purpose, optical interferometers for measuring the diameters of silicon spheres have been developed to convert the length standard into the volume standard with a small uncertainty. A review article is therefore dedicated to describing the state-of-the-art optical interferometers developed for silicon spheres. Relative combined standard uncertainties of several parts in 108 have been achieved today for measuring the volume and density of
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
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We synthesized a number of aniline derivatives containing acyl groups to compare their barriers of rotation around ... KEY WORDS: Monoacyl aniline, Synthesis, Density functional theory, Rotation barrier. INTRODUCTION. Developments in ...
Vibronic coupling density and related concepts
International Nuclear Information System (INIS)
Sato, Tohru; Uejima, Motoyuki; Iwahara, Naoya; Haruta, Naoki; Shizu, Katsuyuki; Tanaka, Kazuyoshi
2013-01-01
Vibronic coupling density is derived from a general point of view as a one-electron property density. Related concepts as well as their applications are presented. Linear and nonlinear vibronic coupling density and related concepts, orbital vibronic coupling density, reduced vibronic coupling density, atomic vibronic coupling constant, and effective vibronic coupling density, illustrate the origin of vibronic couplings and enable us to design novel functional molecules or to elucidate chemical reactions. Transition dipole moment density is defined as an example of the one-electron property density. Vibronic coupling density and transition dipole moment density open a way to design light-emitting molecules with high efficiency.
Density Distributions of Cyclotrimethylenetrinitramines (RDX)
International Nuclear Information System (INIS)
Hoffman, D M
2002-01-01
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 French
Imaginary time density-density correlations for two-dimensional electron gases at high density
Energy Technology Data Exchange (ETDEWEB)
Motta, M.; Galli, D. E. [Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Moroni, S. [IOM-CNR DEMOCRITOS National Simulation Center and SISSA, Via Bonomea 265, 34136 Trieste (Italy); Vitali, E. [Department of Physics, College of William and Mary, Williamsburg, Virginia 23187-8795 (United States)
2015-10-28
We evaluate imaginary time density-density correlation functions for two-dimensional homogeneous electron gases of up to 42 particles in the continuum using the phaseless auxiliary field quantum Monte Carlo method. We use periodic boundary conditions and up to 300 plane waves as basis set elements. We show that such methodology, once equipped with suitable numerical stabilization techniques necessary to deal with exponentials, products, and inversions of large matrices, gives access to the calculation of imaginary time correlation functions for medium-sized systems. We discuss the numerical stabilization techniques and the computational complexity of the methodology and we present the limitations related to the size of the systems on a quantitative basis. We perform the inverse Laplace transform of the obtained density-density correlation functions, assessing the ability of the phaseless auxiliary field quantum Monte Carlo method to evaluate dynamical properties of medium-sized homogeneous fermion systems.
Comparison of density estimators. [Estimation of probability density functions
Energy Technology Data Exchange (ETDEWEB)
Kao, S.; Monahan, J.F.
1977-09-01
Recent work in the field of probability density estimation has included the introduction of some new methods, such as the polynomial and spline methods and the nearest neighbor method, and the study of asymptotic properties in depth. This earlier work is summarized here. In addition, the computational complexity of the various algorithms is analyzed, as are some simulations. The object is to compare the performance of the various methods in small samples and their sensitivity to change in their parameters, and to attempt to discover at what point a sample is so small that density estimation can no longer be worthwhile. (RWR)
Statistical theory of electron densities
International Nuclear Information System (INIS)
Pratt, L.R.; Hoffman, G.G.; Harris, R.A.
1988-01-01
An optimized Thomas--Fermi theory is proposed which retains the simplicity of the original theory and is a suitable reference theory for Monte Carlo density functional treatments of condensed materials. The key ingredient of the optimized theory is a neighborhood sampled potential which contains effects of the inhomogeneities in the one-electron potential. In contrast to the traditional Thomas--Fermi approach, the optimized theory predicts a finite electron density in the vicinity of a nucleus. Consideration of the example of an ideal electron gas subject to a central Coulomb field indicates that implementation of the approach is straightforward. The optimized theory is found to fail completely when a classically forbidden region is approached. However, these circumstances are not of primary interest for calculations of interatomic forces. It is shown how the energy functional of the density may be constructed by integration of a generalized Hellmann--Feynman relation. This generalized Hellmann--Feynman relation proves to be equivalent to the variational principle of density functional quantum mechanics, and, therefore, the present density theory can be viewed as a variational consequence of the constructed energy functional
Current interruption by density depression
International Nuclear Information System (INIS)
Wagner, J.S.; Tajima, T.; Akasofu, S.I.
1985-04-01
Using a one-dimensional electrostatic particle code, we examine processes associated with current interruption in a collisionless plasma when a density depression is present along the current channel. Current interruption due to double layers was suggested by Alfven and Carlqvist (1967) as a cause of solar flares. At a local density depression, plasma instabilities caused by an electron current flow are accentuated, leading to current disruption. Our simulation study encompasses a wide range of the parameters in such a way that under appropriate conditions, both the Alfven and Carlqvist (1967) regime and the Smith and Priest (1972) regime take place. In the latter regime the density depression decays into a stationary structure (''ion-acoustic layer'') which spawns a series of ion-acoustic ''solitons'' and ion phase space holes travelling upstream. A large inductance of the current circuit tends to enhance the plasma instabilities
Sleep spindle density in narcolepsy
DEFF Research Database (Denmark)
Christensen, Julie Anja Engelhard; Nikolic, Miki; Hvidtfelt, Mathias
2017-01-01
BACKGROUND: Patients with narcolepsy type 1 (NT1) show alterations in sleep stage transitions, rapid-eye-movement (REM) and non-REM sleep due to the loss of hypocretinergic signaling. However, the sleep microstructure has not yet been evaluated in these patients. We aimed to evaluate whether...... the sleep spindle (SS) density is altered in patients with NT1 compared to controls and patients with narcolepsy type 2 (NT2). METHODS: All-night polysomnographic recordings from 28 NT1 patients, 19 NT2 patients, 20 controls (C) with narcolepsy-like symptoms, but with normal cerebrospinal fluid hypocretin...... levels and multiple sleep latency tests, and 18 healthy controls (HC) were included. Unspecified, slow, and fast SS were automatically detected, and SS densities were defined as number per minute and were computed across sleep stages and sleep cycles. The between-cycle trends of SS densities in N2...
High Energy Density Laboratory Astrophysics
Lebedev, Sergey V
2007-01-01
During the past decade, research teams around the world have developed astrophysics-relevant research utilizing high energy-density facilities such as intense lasers and z-pinches. Every two years, at the International conference on High Energy Density Laboratory Astrophysics, scientists interested in this emerging field discuss the progress in topics covering: - Stellar evolution, stellar envelopes, opacities, radiation transport - Planetary Interiors, high-pressure EOS, dense plasma atomic physics - Supernovae, gamma-ray bursts, exploding systems, strong shocks, turbulent mixing - Supernova remnants, shock processing, radiative shocks - Astrophysical jets, high-Mach-number flows, magnetized radiative jets, magnetic reconnection - Compact object accretion disks, x-ray photoionized plasmas - Ultrastrong fields, particle acceleration, collisionless shocks. These proceedings cover many of the invited and contributed papers presented at the 6th International Conference on High Energy Density Laboratory Astrophys...
Energy vs. density on paths toward exact density functionals
DEFF Research Database (Denmark)
Kepp, Kasper Planeta
2018-01-01
Recently, the progression toward more exact density functional theory has been questioned, implying a need for more formal ways to systematically measure progress, i.e. a “path”. Here I use the Hohenberg-Kohn theorems and the definition of normality by Burke et al. to define a path toward exactness...
Density dependence of the nuclear energy-density functional
Papakonstantinou, Panagiota; Park, Tae-Sun; Lim, Yeunhwan; Hyun, Chang Ho
2018-01-01
Background: The explicit density dependence in the coupling coefficients entering the nonrelativistic nuclear energy-density functional (EDF) is understood to encode effects of three-nucleon forces and dynamical correlations. The necessity for the density-dependent coupling coefficients to assume the form of a preferably small fractional power of the density ρ is empirical and the power is often chosen arbitrarily. Consequently, precision-oriented parametrizations risk overfitting in the regime of saturation and extrapolations in dilute or dense matter may lose predictive power. Purpose: Beginning with the observation that the Fermi momentum kF, i.e., the cubic root of the density, is a key variable in the description of Fermi systems, we first wish to examine if a power hierarchy in a kF expansion can be inferred from the properties of homogeneous matter in a domain of densities, which is relevant for nuclear structure and neutron stars. For subsequent applications we want to determine a functional that is of good quality but not overtrained. Method: For the EDF, we fit systematically polynomial and other functions of ρ1 /3 to existing microscopic, variational calculations of the energy of symmetric and pure neutron matter (pseudodata) and analyze the behavior of the fits. We select a form and a set of parameters, which we found robust, and examine the parameters' naturalness and the quality of resulting extrapolations. Results: A statistical analysis confirms that low-order terms such as ρ1 /3 and ρ2 /3 are the most relevant ones in the nuclear EDF beyond lowest order. It also hints at a different power hierarchy for symmetric vs. pure neutron matter, supporting the need for more than one density-dependent term in nonrelativistic EDFs. The functional we propose easily accommodates known or adopted properties of nuclear matter near saturation. More importantly, upon extrapolation to dilute or asymmetric matter, it reproduces a range of existing microscopic
Simulating QCD at finite density
de Forcrand, Philippe
2009-01-01
In this review, I recall the nature and the inevitability of the "sign problem" which plagues attempts to simulate lattice QCD at finite baryon density. I present the main approaches used to circumvent the sign problem at small chemical potential. I sketch how one can predict analytically the severity of the sign problem, as well as the numerically accessible range of baryon densities. I review progress towards the determination of the pseudo-critical temperature T_c(mu), and towards the identification of a possible QCD critical point. Some promising advances with non-standard approaches are reviewed.
Momentum density maps for molecules
International Nuclear Information System (INIS)
Cook, J.P.D.; Brion, C.E.
1982-01-01
Momentum-space and position-space molecular orbital density functions computed from LCAO-MO-SCF wavefunctions are used to rationalize the shapes of some momentum distributions measured by binary (e,2e) spectroscopy. A set of simple rules is presented which enable one to sketch the momentum density function and the momentum distribution from a knowledge of the position-space wavefunction and the properties and effects of the Fourier Transform and the spherical average. Selected molecular orbitals of H 2 , N 2 and CO 2 are used to illustrate this work
Photoionization and High Density Gas
Kallman, T.; Bautista, M.; White, Nicholas E. (Technical Monitor)
2002-01-01
We present results of calculations using the XSTAR version 2 computer code. This code is loosely based on the XSTAR v.1 code which has been available for public use for some time. However it represents an improvement and update in several major respects, including atomic data, code structure, user interface, and improved physical description of ionization/excitation. In particular, it now is applicable to high density situations in which significant excited atomic level populations are likely to occur. We describe the computational techniques and assumptions, and present sample runs with particular emphasis on high density situations.
Flashing coupled density wave oscillation
International Nuclear Information System (INIS)
Jiang Shengyao; Wu Xinxin; Zhang Youjie
1997-07-01
The experiment was performed on the test loop (HRTL-5), which simulates the geometry and system design of the 5 MW reactor. The phenomenon and mechanism of different kinds of two-phase flow instabilities, namely geyser instability, flashing instability and flashing coupled density wave instability are described. The especially interpreted flashing coupled density wave instability has never been studied well, it is analyzed by using a one-dimensional non-thermo equilibrium two-phase flow drift model computer code. Calculations are in good agreement with the experiment results. (5 refs.,5 figs., 1 tab.)
DEFF Research Database (Denmark)
Takenaga, K.; Matsuo, S.; Saitoh, K.
2016-01-01
High-density single-mode multicore fibers were designed and fabricated. A heterogeneous 30-core fiber realized a low crosstalk of −55 dB. A quasi-single-mode homogeneous 31-core fiber attained the highest core count as a single-mode multicore fiber.......High-density single-mode multicore fibers were designed and fabricated. A heterogeneous 30-core fiber realized a low crosstalk of −55 dB. A quasi-single-mode homogeneous 31-core fiber attained the highest core count as a single-mode multicore fiber....
High density operation in pulsator
International Nuclear Information System (INIS)
Klueber, O.; Cannici, B.; Engelhardt, W.; Gernhardt, J.; Glock, E.; Karger, F.; Lisitano, G.; Mayer, H.M.; Meisel, D.; Morandi, P.
1976-03-01
This report summarizes the results of experiments at high electron densities (>10 14 cm -3 ) which have been achieved by pulsed gas inflow during the discharge. At these densities a regime is established which is characterized by βsub(p) > 1, nsub(i) approximately nsub(e), Tsub(i) approximately Tsub(e) and tausub(E) proportional to nsub(e). Thus the toroidal magnetic field contributes considerably to the plasma confinement and the ions constitute almost half of the plasma pressure. Furthermore, the confinement is appreciably improved and the plasma becomes impermeable to hot neutrals. (orig.) [de
A numerical study of variable density flow and mixing in porous media
Fan, Yin; Kahawita, René
1994-10-01
A numerical study of a negatively buoyant plume intruding into a neutrally stratified porous medium has been undertaken using finite different methods. Of particular interest has been to ascertain whether the experimentally observed gravitational instabilities that form along the lower edge of the plume are reproduced in the numerical model. The model has been found to faithfully reproduce the mean flow as well as the gravitational instabilities in the intruding plume. A linear stability analysis has confirmed the fact that the negatively buoyant plume is in fact gravitationally unstable and that the stability depends on two parameters: a concentration Rayleigh number and a characteristic length scale which is dependent on the transverse dispersivity.
Creating Great Neighborhoods: Density in Your Community
This report highlights nine community-led efforts to create vibrant neighborhoods through density, discusses the connections between smart growth and density, and introduces design principles to ensure that density becomes a community asset.
Level densities in nuclear physics
International Nuclear Information System (INIS)
Beckerman, M.
1978-01-01
In the independent-particle model nucleons move independently in a central potential. There is a well-defined set of single- particle orbitals, each nucleon occupies one of these orbitals subject to Fermi statistics, and the total energy of the nucleus is equal to the sum of the energies of the individual nucleons. The basic question is the range of validity of this Fermi gas description and, in particular, the roles of the residual interactions and collective modes. A detailed examination of experimental level densities in light-mass system is given to provide some insight into these questions. Level densities over the first 10 MeV or so in excitation energy as deduced from neutron and proton resonances data and from spectra of low-lying bound levels are discussed. To exhibit some of the salient features of these data comparisons to independent-particle (shell) model calculations are presented. Shell structure is predicted to manifest itself through discontinuities in the single-particle level density at the Fermi energy and through variatons in the occupancy of the valence orbitals. These predictions are examined through combinatorial calculations performed with the Grover [Phys. Rev., 157, 832(1967), 185 1303(1969)] odometer method. Before the discussion of the experimenta results, statistical mechanical level densities for spherical nuclei are reviewed. After consideration of deformed nuclei, the conclusions resulting from this work are drawn. 7 figures, 3 tables
Solar corona electron density distribution
International Nuclear Information System (INIS)
Esposito, P.B.; Edenhofer, P.; Lueneburg, E.
1980-01-01
Three and one-half months of single-frequency (f= 0 2.2 x 10 9 Hz) time delay data (earth-to-spacecraft and return signal travel time) were acquired from the Helios 2 spacecraft around the time of its solar occupation (May 16, 1976). Following the determination of the spacecraft trajectory the excess time delay due to the integrated effect of free electrons along the signal's ray path could be separated and modeled. An average solar corona, equatorial, electron density profile, during solar minimum, was deduced from time delay measurements acquired within 5--60 solar radii (R/sub S/) of the sun. As a point of reference, at 10 R/sub S/ from the sun we find an average electron density of 4500 el cm -3 . However, there appears to be an asymmtry in the electron density as the ray path moved from the west (preoccultation) to east (post-occulation) solar limb. This may be related to the fact that during entry into occulation the heliographic latitude of the ray path (at closes approach to the sun) was about 6 0 , whereas during exit it became -7 0 . The Helios electron density model is compared with similar models deduced from a variety of different experimental techniques. Within 5--20 R/sub S/ of the sun the models separate according to solar minimum or maximum conditions; however, anomalies are evident
Electron densities in planetary nebulae
International Nuclear Information System (INIS)
Stanghellini, L.; Kaler, J.B.
1989-01-01
Electron densities for 146 planetary nebulae have been obtained for analyzing a large sample of forbidden lines by interpolating theoretical curves obtained from solutions of the five-level atoms using up-to-date collision strengths and transition probabilities. Electron temperatures were derived from forbidden N II and/or forbidden O III lines or were estimated from the He II 4686 A line strengths. The forbidden O II densities are generally lower than those from forbidden Cl III by an average factor of 0.65. For data sets in which forbidden O II and forbidden S II were observed in common, the forbidden O II values drop to 0.84 that of the forbidden S II, implying that the outermost parts of the nebulae might have elevated densities. The forbidden Cl II and forbidden Ar IV densities show the best correlation, especially where they have been obtained from common data sets. The data give results within 30 percent of one another, assuming homogeneous nebulae. 106 refs
Indian Academy of Sciences (India)
QCD predicts a phase transition between hadronic matter and a quark-gluon plasma at high energy density. The relativistic heavy ion collider (RHIC) at Brookhaven National Laboratory is a new facility dedicated to the experimental study of matter under extreme conditions. Already the first round of experimental results at ...
density-dependent selection revisited
Indian Academy of Sciences (India)
Unknown
is a more useful way of looking at density-dependent selection, and then go on ... these models was that the condition for maintenance of ... In a way, their formulation may be viewed as ... different than competition among species, and typical.
Modern charge-density analysis
Gatti, Carlo
2012-01-01
Focusing on developments from the past 10-15 years, this volume presents an objective overview of the research in charge density analysis. The most promising methodologies are included, in addition to powerful interpretative tools and a survey of important areas of research.
Optimization of Barron density estimates
Czech Academy of Sciences Publication Activity Database
Vajda, Igor; van der Meulen, E. C.
2001-01-01
Roč. 47, č. 5 (2001), s. 1867-1883 ISSN 0018-9448 R&D Projects: GA ČR GA102/99/1137 Grant - others:Copernicus(XE) 579 Institutional research plan: AV0Z1075907 Keywords : Barron estimator * chi-square criterion * density estimation Subject RIV: BD - Theory of Information Impact factor: 2.077, year: 2001
High current density ion source
International Nuclear Information System (INIS)
King, H.J.
1977-01-01
A high-current-density ion source with high total current is achieved by individually directing the beamlets from an electron bombardment ion source through screen and accelerator electrodes. The openings in these screen and accelerator electrodes are oriented and positioned to direct the individual beamlets substantially toward a focus point. 3 figures, 1 table
International Nuclear Information System (INIS)
Alladio, F.
1985-01-01
A short summary of the present status of experimental observations, theoretical ideas and understanding of the density limit in tokamaks is presented. It is the result of the discussion that was held on this topic at the 4th European Tokamak Workshop in Copenhagen (December 4th to 6th, 1985). 610 refs
Density estimation from local structure
CSIR Research Space (South Africa)
Van der Walt, Christiaan M
2009-11-01
Full Text Available Mixture Model (GMM) density function of the data and the log-likelihood scores are compared to the scores of a GMM trained with the expectation maximization (EM) algorithm on 5 real-world classification datasets (from the UCI collection). They show...
Dual model for parton densities
International Nuclear Information System (INIS)
El Hassouni, A.; Napoly, O.
1981-01-01
We derive power-counting rules for quark densities near x=1 and x=0 from parton interpretations of one-particle inclusive dual amplitudes. Using these rules, we give explicit expressions for quark distributions (including charm) inside hadrons. We can then show the compatibility between fragmentation and recombination descriptions of low-p/sub perpendicular/ processes
Micro Coriolis Gas Density Sensor
Sparreboom, Wouter; Ratering, Gijs; Kruijswijk, Wim; van der Wouden, E.J.; Groenesteijn, Jarno; Lötters, Joost Conrad
2017-01-01
In this paper we report on gas density measurements using a micro Coriolis sensor. The technology to fabricate the sensor is based on surface channel technology. The measurement tube is freely suspended and has a wall thickness of only 1 micron. This renders the sensor extremely sensitive to changes
Method of measuring surface density
International Nuclear Information System (INIS)
Gregor, J.
1982-01-01
A method is described of measuring surface density or thickness, preferably of coating layers, using radiation emitted by a suitable radionuclide, e.g., 241 Am. The radiation impinges on the measured material, e.g., a copper foil and in dependence on its surface density or thickness part of the flux of impinging radiation is reflected and part penetrates through the material. The radiation which has penetrated through the material excites in a replaceable adjustable backing characteristic radiation of an energy close to that of the impinging radiation (within +-30 keV). Part of the flux of the characteristic radiation spreads back to the detector, penetrates through the material in which in dependence on surface density or thickness of the coating layer it is partly absorbed. The flux of the penetrated characteristic radiation impinging on the face of the detector is a function of surface density or thickness. Only that part of the energy is evaluated of the energy spectrum which corresponds to the energy of characteristic radiation. (B.S.)
Information Density and Syntactic Repetition
Temperley, David; Gildea, Daniel
2015-01-01
In noun phrase (NP) coordinate constructions (e.g., NP and NP), there is a strong tendency for the syntactic structure of the second conjunct to match that of the first; the second conjunct in such constructions is therefore low in syntactic information. The theory of uniform information density predicts that low-information syntactic…
Ferreira, Lizé-Mari; Eaby, Alan; Dillen, Jan
2017-12-15
The topology of the Coulomb potential density has been studied within the context of the theory of Atoms in Molecules and has been compared with the topologies of the electron density, the virial energy density and the Ehrenfest force density. The Coulomb potential density is found to be mainly structurally homeomorphic with the electron density. The Coulomb potential density reproduces the non-nuclear attractor which is observed experimentally in the molecular graph of the electron density of a Mg dimer, thus, for the first time ever providing an alternative and energetic foundation for the existence of this critical point. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
Double trouble at high density:
DEFF Research Database (Denmark)
Gergs, André; Palmqvist, Annemette; Preuss, Thomas G
2014-01-01
Population size is often regulated by negative feedback between population density and individual fitness. At high population densities, animals run into double trouble: they might concurrently suffer from overexploitation of resources and also from negative interference among individuals...... regardless of resource availability, referred to as crowding. Animals are able to adapt to resource shortages by exhibiting a repertoire of life history and physiological plasticities. In addition to resource-related plasticity, crowding might lead to reduced fitness, with consequences for individual life...... history. We explored how different mechanisms behind resource-related plasticity and crowding-related fitness act independently or together, using the water flea Daphnia magna as a case study. For testing hypotheses related to mechanisms of plasticity and crowding stress across different biological levels...
Generalized Expression for Polarization Density
International Nuclear Information System (INIS)
Wang, Lu; Hahm, T.S.
2009-01-01
A general polarization density which consists of classical and neoclassical parts is systematically derived via modern gyrokinetics and bounce-kinetics by employing a phase-space Lagrangian Lie-transform perturbation method. The origins of polarization density are further elucidated. Extending the work on neoclassical polarization for long wavelength compared to ion banana width [M. N. Rosenbluth and F. L. Hinton, Phys. Rev. Lett. 80, 724 (1998)], an analytical formula for the generalized neoclassical polarization including both finite-banana-width (FBW) and finite-Larmor-radius (FLR) effects for arbitrary radial wavelength in comparison to banana width and gyroradius is derived. In additional to the contribution from trapped particles, the contribution of passing particles to the neoclassical polarization is also explicitly calculated. Our analytic expression agrees very well with the previous numerical results for a wide range of radial wavelength.
Asymptotic density and effective negligibility
Astor, Eric P.
In this thesis, we join the study of asymptotic computability, a project attempting to capture the idea that an algorithm might work correctly in all but a vanishing fraction of cases. In collaboration with Hirschfeldt and Jockusch, broadening the original investigation of Jockusch and Schupp, we introduce dense computation, the weakest notion of asymptotic computability (requiring only that the correct answer is produced on a set of density 1), and effective dense computation, where every computation halts with either the correct answer or (on a set of density 0) a symbol denoting uncertainty. A few results make more precise the relationship between these notions and work already done with Jockusch and Schupp's original definitions of coarse and generic computability. For all four types of asymptotic computation, including generic computation, we demonstrate that non-trivial upper cones have measure 0, building on recent work of Hirschfeldt, Jockusch, Kuyper, and Schupp in which they establish this for coarse computation. Their result transfers to yield a minimal pair for relative coarse computation; we generalize their method and extract a similar result for relative dense computation (and thus for its corresponding reducibility). However, all of these notions of near-computation treat a set as negligible iff it has asymptotic density 0. Noting that this definition is not computably invariant, this produces some failures of intuition and a break with standard expectations in computability theory. For instance, as shown by Hamkins and Miasnikov, the halting problem is (in some formulations) effectively densely computable, even in polynomial time---yet this result appears fragile, as indicated by Rybalov. In independent work, we respond to this by strengthening the approach of Jockusch and Schupp to avoid such phenomena; specifically, we introduce a new notion of intrinsic asymptotic density, invariant under computable permutation, with rich relations to both
High density energy storage capacitor
International Nuclear Information System (INIS)
Whitham, K.; Howland, M.M.; Hutzler, J.R.
1979-01-01
The Nova laser system will use 130 MJ of capacitive energy storage and have a peak power capability of 250,000 MW. This capacitor bank is a significant portion of the laser cost and requires a large portion of the physical facilities. In order to reduce the cost and volume required by the bank, the Laser Fusion Program funded contracts with three energy storage capacitor producers: Aerovox, G.E., and Maxwell Laboratories, to develop higher energy density, lower cost energy storage capacitors. This paper describes the designs which resulted from the Aerovox development contract, and specifically addresses the design and initial life testing of a 12.5 kJ, 22 kV capacitor with a density of 4.2 J/in 3 and a projected cost in the range of 5 cents per joule
Density operators in quantum mechanics
International Nuclear Information System (INIS)
Burzynski, A.
1979-01-01
A brief discussion and resume of density operator formalism in the way it occurs in modern physics (in quantum optics, quantum statistical physics, quantum theory of radiation) is presented. Particularly we emphasize the projection operator method, application of spectral theorems and superoperators formalism in operator Hilbert spaces (Hilbert-Schmidt type). The paper includes an appendix on direct sums and direct products of spaces and operators, and problems of reducibility for operator class by using the projection operators. (author)
International Nuclear Information System (INIS)
Lombard, R.J.; Mas, D.; Moszkowski, S.A.
1991-01-01
We discuss two expressions for the density of kinetic energy which differ by an integration by parts. Using the Wigner transform we shown that the arithmetic mean of these two terms is closely analogous to the classical value. Harmonic oscillator wavefunctions are used to illustrate the radial dependence of these expressions. We study the differences they induce through effective mass terms when performing self-consistent calculations. (author)
Neutronic density perturbation by probes
International Nuclear Information System (INIS)
Vigon, M. A.; Diez, L.
1956-01-01
The introduction of absorbent materials of neutrons in diffuser media, produces local disturbances of neutronic density. The disturbance depends especially on the nature and size of the absorbent. Approximated equations which relates te disturbance and the distance to the absorbent in the case of thin disks have been drawn. The experimental comprobation has been carried out in two especial cases. In both cases the experimental results are in agreement with the calculated values from these equations. (Author)
International Nuclear Information System (INIS)
Knuyt, G.K.; Callebaut, D.K.
1978-01-01
The equations defining the ion density in a non-quasineutral plasma (chasma) are derived for a number of particular cases from the general results obtained in paper 1. Explicit calculations are made for a fairly general class of boundaries: all tri-axial ellipsoids, including cylinders with elliptic cross-section and the plane parallel case. The results are very simple. When the ion production and the beam intensity are constant then the steady state ion space charge is also constant in space, it varies over less than 10% for the various geometries, it may exceed the beam density largely for comparatively high pressures (usually still less than about 10 -3 Torr), it is tabulated for a number of interesting cases and moreover it can be calculated precisely and easily by some simple formulae for which also approximations are elaborated. The total potential is U =-ax 2 -by 2 -cz 2 , a, b and c constants which can be calculated immediately from the space charge density and the geometry; the largest coefficient varies at most over a factor four for various geometries; it is tabulated for a number of interesting cases. (author)
Density functional theory of nuclei
International Nuclear Information System (INIS)
Terasaki, Jun
2008-01-01
The density functional theory of nuclei has come to draw attention of scientists in the field of nuclear structure because the theory is expected to provide reliable numerical data in wide range on the nuclear chart. This article is organized to present an overview of the theory to the people engaged in the theory of other fields as well as those people in the nuclear physics experiments. At first, the outline of the density functional theory widely used in the electronic systems (condensed matter, atoms, and molecules) was described starting from the Kohn-Sham equation derived on the variational principle. Then the theory used in the field of nuclear physics was presented. Hartree-Fock and Hartree-Fock-Bogolyubov approximation by using Skyrme interaction was explained. Comparison of the results of calculations and experiments of binding energies and ground state mean square charge radii of some magic number nuclei were shown. The similarity and dissimilarity between the two streams were summarized. Finally the activities of the international project of Universal Nuclear Energy Density Functional (UNEDF) which was started recently lead by US scientist was reported. This project is programmed for five years. One of the applications of the project is the calculation of the neutron capture cross section of nuclei on the r-process, which is absolutely necessary for the nucleosynthesis research. (S. Funahashi)
Dual chiral density wave in quark matter
International Nuclear Information System (INIS)
Tatsumi, Toshitaka
2002-01-01
We prove that quark matter is unstable for forming a dual chiral density wave above a critical density, within the Nambu-Jona-Lasinio model. Presence of a dual chiral density wave leads to a uniform ferromagnetism in quark matter. A similarity with the spin density wave theory in electron gas and the pion condensation theory is also pointed out. (author)
Density functionals in the laboratory frame
International Nuclear Information System (INIS)
Giraud, B. G.
2008-01-01
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
On VC-density over indiscernible sequences
Guingona, Vincent; Hill, Cameron Donnay
2011-01-01
In this paper, we study VC-density over indiscernible sequences (denoted VC_ind-density). We answer an open question in [1], showing that VC_ind-density is always integer valued. We also show that VC_ind-density and dp-rank coincide in the natural way.
Research of mechanism of density lock
International Nuclear Information System (INIS)
Wang Shengfei; Yan Changqi; Gu Haifeng
2010-01-01
Mechanism of density lock was analyzed according to the work conditions of density lock. The results showed that: the stratification with no disturbance satisfied the work conditions of density lock; fluids between the stratification were not mixed at the condition of connected to each other; the density lock can be open automatically by controlled the pressure balance at the stratification. When disturbance existed, the stratification might be broken and mass would be transferred by convection. The stability of stratification can be enhanced by put the special structure in density lock to ensure the normal work of density lock. At last, the minimum of heat loss in density lock was also analyzed. (authors)
Energy Technology Data Exchange (ETDEWEB)
Gokaltun, Seckin; McDaniel, Dwayne; Roelant, David [Applied Research Center, Florida International University, 10555 West Flagler Street, Suite 2100, Miami, FL 33174 (United States)
2012-07-01
Multiphase flows involving gas and liquid phases can be observed in engineering operations at various Department of Energy sites, such as mixing of slurries using pulsed-air mixers and hydrogen gas generation in liquid waste tanks etc. The dynamics of the gas phase in the liquid domain play an important role in the mixing effectiveness of the pulsed-air mixers or in the level of gas pressure build-up in waste tanks. To understand such effects, computational fluid dynamics methods (CFD) can be utilized by developing a three-dimensional computerized multiphase flow model that can predict accurately the behavior of gas motion inside liquid-filled tanks by solving the governing mathematical equations that represent the physics of the phenomena. In this paper, such a CFD method, lattice Boltzmann method (LBM), is presented that can model multiphase flows accurately and efficiently. LBM is favored over traditional Navier-Stokes based computational models since interfacial forces are handled more effectively in LBM. The LBM is easier to program, more efficient to solve on parallel computers, and has the ability to capture the interface between different fluid phases intrinsically. The LBM used in this paper can solve for the incompressible and viscous flow field in three dimensions, while at the same time, solve the Cahn-Hillard equation to track the position of the gas-liquid interface specifically when the density and viscosity ratios between the two fluids are high. This feature is of primary importance since the previous LBM models proposed for multiphase flows become unstable when the density ratio is larger than 10. The ability to provide stable and accurate simulations at large density ratios becomes important when the simulation case involves fluids such as air and water with a density ratio around 1000 that are common to many engineering problems. In order to demonstrate the capability of the 3D LBM method at high density ratios, a static bubble simulation is
Minimal nuclear energy density functional
Bulgac, Aurel; Forbes, Michael McNeil; Jin, Shi; Perez, Rodrigo Navarro; Schunck, Nicolas
2018-04-01
We present a minimal nuclear energy density functional (NEDF) called "SeaLL1" that has the smallest number of possible phenomenological parameters to date. SeaLL1 is defined by seven significant phenomenological parameters, each related to a specific nuclear property. It describes the nuclear masses of even-even nuclei with a mean energy error of 0.97 MeV and a standard deviation of 1.46 MeV , two-neutron and two-proton separation energies with rms errors of 0.69 MeV and 0.59 MeV respectively, and the charge radii of 345 even-even nuclei with a mean error ɛr=0.022 fm and a standard deviation σr=0.025 fm . SeaLL1 incorporates constraints on the equation of state (EoS) of pure neutron matter from quantum Monte Carlo calculations with chiral effective field theory two-body (NN ) interactions at the next-to-next-to-next-to leading order (N3LO) level and three-body (NNN ) interactions at the next-to-next-to leading order (N2LO) level. Two of the seven parameters are related to the saturation density and the energy per particle of the homogeneous symmetric nuclear matter, one is related to the nuclear surface tension, two are related to the symmetry energy and its density dependence, one is related to the strength of the spin-orbit interaction, and one is the coupling constant of the pairing interaction. We identify additional phenomenological parameters that have little effect on ground-state properties but can be used to fine-tune features such as the Thomas-Reiche-Kuhn sum rule, the excitation energy of the giant dipole and Gamow-Teller resonances, the static dipole electric polarizability, and the neutron skin thickness.
Leptin and bone mineral density
DEFF Research Database (Denmark)
Morberg, Cathrine M.; Tetens, Inge; Black, Eva
2003-01-01
Leptin has been suggested to decrease bone mineral density (BMD). This observational analysis explored the relationship between serum leptin and BMD in 327 nonobese men (controls) (body mass index 26.1 +/- 3.7 kg/m(2), age 49.9 +/- 6.0 yr) and 285 juvenile obese men (body mass index 35.9 +/- 5.9 kg...... males, but it also stresses the fact that the strong covariation between the examined variables is a shortcoming of the cross-sectional design....
Bounded Densities and Their Derivatives
DEFF Research Database (Denmark)
Kozine, Igor; Krymsky, V.
2009-01-01
This paper describes how one can compute interval-valued statistical measures given limited information about the underlying distribution. The particular focus is on a bounded derivative of a probability density function and its combination with other available statistical evidence for computing ...... quantities of interest. To be able to utilise the evidence about the derivative it is suggested to adapt the ‘conventional’ problem statement to variational calculus and the way to do so is demonstrated. A number of examples are given throughout the paper....
Equilibrium problems for Raney densities
Forrester, Peter J.; Liu, Dang-Zheng; Zinn-Justin, Paul
2015-07-01
The Raney numbers are a class of combinatorial numbers generalising the Fuss-Catalan numbers. They are indexed by a pair of positive real numbers (p, r) with p > 1 and 0 0 and similarly use both methods to identify the equilibrium problem for (p, r) = (θ/q + 1, 1/q), θ > 0 and q \\in Z+ . The Wiener-Hopf method is used to extend the latter to parameters (p, r) = (θ/q + 1, m + 1/q) for m a non-negative integer, and also to identify the equilibrium problem for a family of densities with moments given by certain binomial coefficients.
High density fuel storage rack
International Nuclear Information System (INIS)
Zezza, L.J.
1980-01-01
High storage density for spent nuclear fuel assemblies in a pool achieved by positioning fuel storage cells of high thermal neutron absorption materials in an upright configuration in a rack. The rack holds the cells at required pitch. Each cell carries an internal fuel assembly support, and most cells are vertically movable in the rack so that they rest on the pool bottom. Pool water circulation through the cells and around the fuel assemblies is permitted by circulation openings at the top and bottom of the cells above and below the fuel assemblies
Origin of cosmological density fluctuations
International Nuclear Information System (INIS)
Carr, B.J.
1984-11-01
The density fluctuations required to explain the large-scale cosmological structure may have arisen spontaneously as a result of a phase transition in the early Universe. There are several ways in which such fluctuations may have ben produced, and they could have a variety of spectra, so one should not necessarily expect all features of the large-scale structure to derive from a simple power law spectrum. Some features may even result from astrophysical amplification mechanisms rather than gravitational instability. 128 references
Finite density aspects of leptogenesis
International Nuclear Information System (INIS)
Hohenegger, Andreas
2010-01-01
Leptogenesis takes place in the early universe at high temperatures and densities and a deviation from equilibrium in the decay of heavy Majorana neutrinos is a fundamental requirement for the generation of the asymmetry. The equations, commonly used for its description, are largely based on classical Boltzmann equations (BEs) while the source of CP-violation is a quantum interference phenomenon. In view of this clash, it is desirable to study such processes in terms of non-equilibrium quantum field theory. On the other hand, it is simpler to solve BEs rather than the corresponding quantum field theoretical ones. Therefore, we derive modified BEs from first principles in the Kadanoff-Baym (KB) formalism. The results, found for a simple toy model, can be applied to popular phenomenological scenarios by analogy. This approach uncovers structural differences of the corrected equations and leads to different results for the form of the finite density contributions to the CP-violating parameter. In the case of degenerate heavy neutrino masses, corresponding to the popular scenario of resonant leptogenesis, it allows to explicitly distinguish between regimes where BEs are applicable or inapplicable.
Density fluctuations in extended inflation
International Nuclear Information System (INIS)
Guth, A.H.; Jain, B.
1992-01-01
We estimate the density perturbation spectrum δρ/ρ in the extended inflationary model, in which the scalar curvature is coupled to a Brans-Dicke field. Through a conformal transformation and a redefinition of the Brans-Dicke field, the action of the theory is cast into a form with no coupling to the scalar curvature and a canonical kinetic term for the redefined field. Following Kolb, Salopek, and Turner, we calculate δρ/ρ using the transformed action and the standard recipe developed for conventional inflation. This recipe is expected to give a valid order-of-magnitude estimate, but a precise calculation would require a more careful treatment of several aspects of the problem. The spectrum behaves as a positive power of the wavelength, a feature that might be useful in building models to account for the observed large-scale structure of the universe. Our result for the overall amplitude of density perturbations differs slightly from that of the previous authors, and the reasons for these differences are discussed. We also point out that the conformal transformation method can be applied to a wider class of generalized gravity theories
The Nutrient Density of Snacks
Directory of Open Access Journals (Sweden)
Julie Hess BA
2017-03-01
Full Text Available Background: Although Americans receive almost a quarter of their daily energy from snacks, snacking remains a poorly defined and understood eating occasion. However, there is little dietary guidance about choosing snacks. Families, clinicians, and researchers need a comprehensive approach to assessing their nutritional value. Objective: To quantify and compare the nutrient density of commonly consumed snacks by their overall nutrient profiles using the Nutrient-Rich Foods (NRF Index 10.3. Methods: NRF Index scores were calculated for the top 3 selling products (based on 2014 market research data in different snack categories. These NRF scores were averaged to provide an overall nutrient-density score for each category. Results: Based on NRF scores, yogurt (55.3, milk (52.5, and fruit (30.1 emerged as the most nutrient-dense snacks. Ice cream (−4.4, pies and cakes (−11.1, and carbonated soft drinks (−17.2 emerged as the most nutrient-poor snacks. Conclusions: The NRF Index is a useful tool for assessing the overall nutritional value of snacks based on nutrients to limit and nutrients to encourage.
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
Asymptotic density and the Ershov hierarchy
Downey, Rod; Jockusch, Carl; McNicholl, Timothy H.; Schupp, Paul
2013-01-01
We classify the asymptotic densities of the $\\Delta^0_2$ sets according to their level in the Ershov hierarchy. In particular, it is shown that for $n \\geq 2$, a real $r \\in [0,1]$ is the density of an $n$-c.e.\\ set if and only if it is a difference of left-$\\Pi_2^0$ reals. Further, we show that the densities of the $\\omega$-c.e.\\ sets coincide with the densities of the $\\Delta^0_2$ sets, and there are $\\omega$-c.e.\\ sets whose density is not the density of an $n$-c.e. set for any $n \\in \\ome...
Imaging Breast Density: Established and Emerging Modalities
Directory of Open Access Journals (Sweden)
Jeon-Hor Chen
2015-12-01
Full Text Available Mammographic density has been proven as an independent risk factor for breast cancer. Women with dense breast tissue visible on a mammogram have a much higher cancer risk than women with little density. A great research effort has been devoted to incorporate breast density into risk prediction models to better estimate each individual’s cancer risk. In recent years, the passage of breast density notification legislation in many states in USA requires that every mammography report should provide information regarding the patient’s breast density. Accurate definition and measurement of breast density are thus important, which may allow all the potential clinical applications of breast density to be implemented. Because the two-dimensional mammography-based measurement is subject to tissue overlapping and thus not able to provide volumetric information, there is an urgent need to develop reliable quantitative measurements of breast density. Various new imaging technologies are being developed. Among these new modalities, volumetric mammographic density methods and three-dimensional magnetic resonance imaging are the most well studied. Besides, emerging modalities, including different x-ray–based, optical imaging, and ultrasound-based methods, have also been investigated. All these modalities may either overcome some fundamental problems related to mammographic density or provide additional density and/or compositional information. The present review article aimed to summarize the current established and emerging imaging techniques for the measurement of breast density and the evidence of the clinical use of these density methods from the literature.
International Nuclear Information System (INIS)
Murray, M.
1988-02-01
The transverse energy, E/sub tau/ spectra for O 16 and S 32 incident for various elements at 200 GeVnucleon are shown. The target and projectile dependencies of the data are discussed. The energy density achieved is estimated. For O 16 on Tungsten the multiplicity spectrum is also presented as well as the pseudorapidity spectra as a function of the transverse energy. The multiplicity cross section dσdN as measured in the backward hemisphere (0.9 < /eta/ < 2.9/ is found to be very similar in shape to the transverse energy distribution dσdE/tau/ reflecting the particular geometry of nucleus nucleus nucleus collisions. The dependence on the atomic mass of the target, A/sub tau/ and projectile A/sub p/ is not what one would expect from naive considerations
Review of non-nuclear density gauges as possible replacements for ITD's nuclear density gauges.
2015-01-01
This report examines the possibility of replacing nuclear density gauges (NDGs) with non-nuclear density gauges (NNDGs) to : measure density of hot mix asphalt (HMA) and unbound pavement layers in the field. The research team evaluated the : effectiv...
On thermodynamic limits of entropy densities
Moriya, H; Van Enter, A
We give some sufficient conditions which guarantee that the entropy density in the thermodynamic limit is equal to the thermodynamic limit of the entropy densities of finite-volume (local) Gibbs states.
Density structures inside the plasmasphere: Cluster observations
DEFF Research Database (Denmark)
Darrouzet, F.; Decreau, P.M.E.; De Keyser, J.
2004-01-01
The electron density profiles derived from the EFW and WHISPER instruments on board the four Cluster spacecraft reveal density structures inside the plasmasphere and at its outer boundary, the plasmapause. We have conducted a statistical study to characterize these density structures. We focus...... on the plasmasphere crossing on I I April 2002, during which Cluster observed several density irregularities inside the plasmasphere, as well as a plasmaspheric plume. We derive the density gradient vectors from simultaneous density measurements by the four spacecraft. We also determine the normal velocity...... of the boundaries of the plume and of the irregularities from the time delays between those boundaries in the four individual density profiles, assuming they are planar. These new observations yield novel insights about the occurrence of density irregularities, their geometry and their dynamics. These in...
Global Population Density Grid Time Series Estimates
National Aeronautics and Space Administration — Global Population Density Grid Time Series Estimates provide a back-cast time series of population density grids based on the year 2000 population grid from SEDAC's...
VT Building Density - from E911 ESITE
Vermont Center for Geographic Information — (Link to Metadata) The FacilitiesBuildings_DENSITY data set depicts density for defined types of structures in Vermont. The vector source used to generate the...
THE INFLUENCE OF DIFFERENT STOCKING DENSITIES AND ...
African Journals Online (AJOL)
Helet Lambrechts
stocking densities will have a possible inhibitory effect on the establishment of ... Keywords: Ostriches, stocking density, male:female ratio, reproductive performance .... Eggs were stored upright with the air cell in the uppermost position.
Ethnicity, Soybean Consumption, and Mammographic Densities
National Research Council Canada - National Science Library
Maskarinec, Gertraud
1997-01-01
The purpose of this study is to determine whether mammographic density patterns differ by ethnic background and to explore the possible association of a soy rich diet with mammographic density patterns...
Limitations in accurate electron density studies
International Nuclear Information System (INIS)
Wal, R. van der.
1982-01-01
Most of X-ray diffraction studies are devoted to the determination of three-dimensional crystal structures from the electron density distributions. In these cases the density distributions are described by the independent atom model (IAM model), which consists of a superposition of spherically averaged free atom densities, which are smeared by thermal vibrations. During the last few decades studies have been made into the deviations of the density distribution from the IAM model, which enables a study of the chemical binding between atoms. The total density can be described using pseudo-atom multipole models as a superposition of aspherical pseudo-atom densities. A fundamental problem is that the separation of this density into an IAM and a deformation part is not unique. This thesis considers the problem and besides deformation densities from X-ray diffraction also considers the corresponding deformation electric field and deformation potential. (C.F.)
Anisotropic dynamic mass density for fluidsolid composites
Wu, Ying; Mei, Jun; Sheng, Ping
2012-01-01
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
Density functional theory and parallel processing
International Nuclear Information System (INIS)
Ward, R.C.; Geist, G.A.; Butler, W.H.
1987-01-01
The authors demonstrate a method for obtaining the ground state energies and charge densities of a system of atoms described within density functional theory using simulated annealing on a parallel computer
On the origin of plasma density blobs
Energy Technology Data Exchange (ETDEWEB)
Krasheninnikov, S.I., E-mail: skrash@mae.ucsd.edu
2016-12-01
By keeping nonlinear Boltzmann factor in electron density dependence on electrostatic potential it is demonstrated that large plasma density blobs, often seen in experiment inside separatrix, can exist within the framework of drift wave dynamics. The estimates show that plasma density in a blob can be ∼3 times higher that average plasma density, but hardly exceeds this limit, which in a ball park is in agreement with experimental observations.
The dynamics of variable-density turbulence
International Nuclear Information System (INIS)
Sandoval, D.L.
1995-11-01
The dynamics of variable-density turbulent fluids are studied by direct numerical simulation. The flow is incompressible so that acoustic waves are decoupled from the problem, and implying that density is not a thermodynamic variable. Changes in density occur due to molecular mixing. The velocity field, is in general, divergent. A pseudo-spectral numerical technique is used to solve the equations of motion. Three-dimensional simulations are performed using a grid size of 128 3 grid points. Two types of problems are studied: (1) the decay of isotropic, variable-density turbulence, and (2) buoyancy-generated turbulence in a fluid with large density fluctuations. In the case of isotropic, variable-density turbulence, the overall statistical decay behavior, for the cases studied, is relatively unaffected by the presence of density variations when the initial density and velocity fields are statistically independent. The results for this case are in quantitative agreement with previous numerical and laboratory results. In this case, the initial density field has a bimodal probability density function (pdf) which evolves in time towards a Gaussian distribution. The pdf of the density field is symmetric about its mean value throughout its evolution. If the initial velocity and density fields are statistically dependent, however, the decay process is significantly affected by the density fluctuations. For the case of buoyancy-generated turbulence, variable-density departures from the Boussinesq approximation are studied. The results of the buoyancy-generated turbulence are compared with variable-density model predictions. Both a one-point (engineering) model and a two-point (spectral) model are tested against the numerical data. Some deficiencies in these variable-density models are discussed and modifications are suggested
36 CFR 910.12 - Development density.
2010-07-01
... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Development density. 910.12... DEVELOPMENT AREA Urban Planning and Design Concerns § 910.12 Development density. (a) Land would be developed... density within the building envelope delineated by specific height restrictions, but shall also establish...
Interactive density maps for moving objects
Scheepens, R.J.; Willems, C.M.E.; Wetering, van de H.M.M.; Wijk, van J.J.
2012-01-01
Trajectories capture the movements of objects with multiple attributes. A visualization method called density maps shows trends in these trajectories. Density map creation involves aggregating smoothed trajectories in a density field and then visualizing the field. Users can explore attributes along
Statistical density modification using local pattern matching
International Nuclear Information System (INIS)
Terwilliger, Thomas C.
2003-01-01
Statistical density modification can make use of local patterns of density found in protein structures to improve crystallographic phases. A method for improving crystallographic phases is presented that is based on the preferential occurrence of certain local patterns of electron density in macromolecular electron-density maps. The method focuses on the relationship between the value of electron density at a point in the map and the pattern of density surrounding this point. Patterns of density that can be superimposed by rotation about the central point are considered equivalent. Standard templates are created from experimental or model electron-density maps by clustering and averaging local patterns of electron density. The clustering is based on correlation coefficients after rotation to maximize the correlation. Experimental or model maps are also used to create histograms relating the value of electron density at the central point to the correlation coefficient of the density surrounding this point with each member of the set of standard patterns. These histograms are then used to estimate the electron density at each point in a new experimental electron-density map using the pattern of electron density at points surrounding that point and the correlation coefficient of this density to each of the set of standard templates, again after rotation to maximize the correlation. The method is strengthened by excluding any information from the point in question from both the templates and the local pattern of density in the calculation. A function based on the origin of the Patterson function is used to remove information about the electron density at the point in question from nearby electron density. This allows an estimation of the electron density at each point in a map, using only information from other points in the process. The resulting estimates of electron density are shown to have errors that are nearly independent of the errors in the original map using
Conditional Density Approximations with Mixtures of Polynomials
DEFF Research Database (Denmark)
Varando, Gherardo; López-Cruz, Pedro L.; Nielsen, Thomas Dyhre
2015-01-01
Mixtures of polynomials (MoPs) are a non-parametric density estimation technique especially designed for hybrid Bayesian networks with continuous and discrete variables. Algorithms to learn one- and multi-dimensional (marginal) MoPs from data have recently been proposed. In this paper we introduce...... two methods for learning MoP approximations of conditional densities from data. Both approaches are based on learning MoP approximations of the joint density and the marginal density of the conditioning variables, but they differ as to how the MoP approximation of the quotient of the two densities...
Experimental level densities of atomic nuclei
Energy Technology Data Exchange (ETDEWEB)
Guttormsen, M.; Bello Garrote, F.L.; Eriksen, T.K.; Giacoppo, F.; Goergen, A.; Hagen, T.W.; Klintefjord, M.; Larsen, A.C.; Nyhus, H.T.; Renstroem, T.; Rose, S.J.; Sahin, E.; Siem, S.; Tornyi, T.G.; Tveten, G.M. [University of Oslo, Department of Physics, Oslo (Norway); Aiche, M.; Ducasse, Q.; Jurado, B. [University of Bordeaux, CENBG, CNRS/IN2P3, B.P. 120, Gradignan (France); Bernstein, L.A.; Bleuel, D.L. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Byun, Y.; Voinov, A. [Ohio University, Department of Physics and Astronomy, Athens, Ohio (United States); Gunsing, F. [CEA Saclay, DSM/Irfu/SPhN, Cedex (France); Lebois, L.; Leniau, B.; Wilson, J. [Institut de Physique Nucleaire d' Orsay, Orsay Cedex (France); Wiedeking, M. [iThemba LABS, P.O. Box 722, Somerset West (South Africa)
2015-12-15
It is almost 80 years since Hans Bethe described the level density as a non-interacting gas of protons and neutrons. In all these years, experimental data were interpreted within this picture of a fermionic gas. However, the renewed interest of measuring level density using various techniques calls for a revision of this description. In particular, the wealth of nuclear level densities measured with the Oslo method favors the constant-temperature level density over the Fermi-gas picture. From the basis of experimental data, we demonstrate that nuclei exhibit a constant-temperature level density behavior for all mass regions and at least up to the neutron threshold. (orig.)
Density heterogeneity of the cratonic lithosphere
DEFF Research Database (Denmark)
Cherepanova, Yulia; Artemieva, Irina
2015-01-01
Using free-board modeling, we examine a vertically-averaged mantle density beneath the Archean-Proterozoic Siberian craton in the layer from the Moho down to base of the chemical boundary layer (CBL). Two models are tested: in Model 1 the base of the CBL coincides with the LAB, whereas in Model 2...... the base of the CBL is at a 180 km depth. The uncertainty of density model is density structure of the Siberian lithospheric mantle with a strong...... correlation between mantle density variations and the tectonic setting. Three types of cratonic mantle are recognized from mantle density anomalies. 'Pristine' cratonic regions not sampled by kimberlites have the strongest depletion with density deficit of 1.8-3.0% (and SPT density of 3.29-3.33 t/m3...
International Nuclear Information System (INIS)
Rand, M.L.; Packham, M.A.; Mustard, J.F.
1983-01-01
The origin of the density heterogeneity of platelets was studied by measuring the survival of density subpopulations of rabbit platelets separated by discontinuous Stractan density gradient centrifugation. When a total population of 51 Cr-labelled platelets was injected into recipient rabbits, the relative specific radioactivity of the most dense platelets decreased rapidly. In contrast, that of the least dense platelets had not changed 24 hr after injection, and then decreased slowly. To distinguish between the possibilities that most dense platelets are cleared from the circulation more quickly than least dense platelets or that platelets decrease in density as they age in the circulation, the concurrent survival of least dense and most dense platelets, labelled with either 51 Cr or 111 In-labelled total platelet populations, determined concurrently in the same rabbits, are identical, calculated from 1 hr values as 100%. However, the 1-hr recovery of 111 In-labelled platelets was slightly but significantly less than that of 51 Cr-labelled platelets. Therefore, researchers studied the survival of 51 Cr-labelled least dense and 111 In-labelled most dense platelets as well as that of 111 In-labelled least dense and 51 Cr-labelled most dense platelets. Mean 1-hr recovery of least dense platelets, labelled with either isotope (78% +/- 7%, SD) was similar to that of most dense platelets, labelled with either isotope (77% +/- 8%; SD). Mean survival of least dense platelets was 47.3 +/- 18.7 hr (SD), which was significantly less than that of most dense platelets (76.1 +/- 21.6 hr; SD) (p less than 0.0025). These results indicate that platelets decrease in buoyant density as they age in the circulation and that most dense platelets are enriched in young platelets, and least dense in old
Dresselhaus, Thomas; Neugebauer, Johannes; Knecht, Stefan; Keller, Sebastian; Ma, Yingjin; Reiher, Markus
2015-01-28
We present the first implementation of a density matrix renormalization group algorithm embedded in an environment described by density functional theory. The frozen density embedding scheme is used with a freeze-and-thaw strategy for a self-consistent polarization of the orbital-optimized wavefunction and the environmental densities with respect to each other.
The Fourier transform of tubular densities
Prior, C B
2012-05-18
We consider the Fourier transform of tubular volume densities, with arbitrary axial geometry and (possibly) twisted internal structure. This density can be used to represent, among others, magnetic flux or the electron density of biopolymer molecules. We consider tubes of both finite radii and unrestricted radius. When there is overlap of the tube structure the net density is calculated using the super-position principle. The Fourier transform of this density is composed of two expressions, one for which the radius of the tube is less than the curvature of the axis and one for which the radius is greater (which must have density overlap). This expression can accommodate an asymmetric density distribution and a tube structure which has non-uniform twisting. In addition we give several simpler expressions for isotropic densities, densities of finite radius, densities which decay at a rate sufficient to minimize local overlap and finally individual surfaces of the tube manifold. These simplified cases can often be expressed as arclength integrals and can be evaluated using a system of first-order ODEs. © 2012 IOP Publishing Ltd.
The Fourier transform of tubular densities
International Nuclear Information System (INIS)
Prior, C B; Goriely, A
2012-01-01
We consider the Fourier transform of tubular volume densities, with arbitrary axial geometry and (possibly) twisted internal structure. This density can be used to represent, among others, magnetic flux or the electron density of biopolymer molecules. We consider tubes of both finite radii and unrestricted radius. When there is overlap of the tube structure the net density is calculated using the super-position principle. The Fourier transform of this density is composed of two expressions, one for which the radius of the tube is less than the curvature of the axis and one for which the radius is greater (which must have density overlap). This expression can accommodate an asymmetric density distribution and a tube structure which has non-uniform twisting. In addition we give several simpler expressions for isotropic densities, densities of finite radius, densities which decay at a rate sufficient to minimize local overlap and finally individual surfaces of the tube manifold. These simplified cases can often be expressed as arclength integrals and can be evaluated using a system of first-order ODEs. (paper)
Controlling of density uniformity of polyacrylate foams
International Nuclear Information System (INIS)
Shan Wenwen; Yuan Baohe; Wang Yanhong; Xu Jiayun; Zhang Lin
2010-01-01
The density non-uniformity existing in most low-density foams will affect performance of the foams. The trimethylolpropane trimethacrylate (TMPTA) foam targets were prepared and controlling methods of the foams, density uniformity were explored together with its forming mechanism. It has been found that the UV-light with high intensity can improve the distribution uniformity of the free radicals induced by UV photons in the solvents, thus improve the density uniformity of the foams. In addition, container wall would influence the concentration distribution of the solution, which affects the density uniformity of the foams. Thus, the UV-light with high intensity was chosen together with polytetrafluoroethylene molds instead of glass molds to prepare the foams with the density non-uniformity less than 10%. β-ray detection technology was used to measure the density uniformity of the TMPTA foams with the density in the range of 10 to 100 mg · cm -3 , and the results show that the lower the foam density is, the worse the density uniformity is. (authors)
A SURVEY OF CORONAL CAVITY DENSITY PROFILES
International Nuclear Information System (INIS)
Fuller, J.; Gibson, S. E.
2009-01-01
Coronal cavities are common features of the solar corona that appear as darkened regions at the base of coronal helmet streamers in coronagraph images. Their darkened appearance indicates that they are regions of lowered density embedded within the comparatively higher density helmet streamer. Despite interfering projection effects of the surrounding helmet streamer (which we refer to as the cavity rim), Fuller et al. have shown that under certain conditions it is possible to use a Van de Hulst inversion of white-light polarized brightness (pB) data to calculate the electron density of both the cavity and cavity rim plasma. In this article, we apply minor modifications to the methods of Fuller et al. in order to improve the accuracy and versatility of the inversion process, and use the new methods to calculate density profiles for both the cavity and cavity rim in 24 cavity systems. We also examine trends in cavity morphology and how departures from the model geometry affect our density calculations. The density calculations reveal that in all 24 cases the cavity plasma has a flatter density profile than the plasma of the cavity rim, meaning that the cavity has a larger density depletion at low altitudes than it does at high altitudes. We find that the mean cavity density is over four times greater than that of a coronal hole at an altitude of 1.2 R sun and that every cavity in the sample is over twice as dense as a coronal hole at this altitude. Furthermore, we find that different cavity systems near solar maximum span a greater range in density at 1.2 R sun than do cavity systems near solar minimum, with a slight trend toward higher densities for systems nearer to solar maximum. Finally, we found no significant correlation of cavity density properties with cavity height-indeed, cavities show remarkably similar density depletions-except for the two smallest cavities that show significantly greater depletion.
Reineke’s stand density index: a quantitative and non-unitless measure of stand density
Curtis L. VanderSchaaf
2013-01-01
When used as a measure of relative density, Reinekeâs stand density index (SDI) can be made unitless by relating the current SDI to a standard density but when used as a quantitative measure of stand density SDI is not unitless. Reinekeâs SDI relates the current stand density to an equivalent number of trees per unit area in a stand with a quadratic mean diameter (Dq)...
Device for measuring fission product density
International Nuclear Information System (INIS)
Kaneda, Mitsunori.
1980-01-01
Purpose: To determine the fission product density of xenon or the like and enable measurement of real time of fission product density in a reactor by calculating the disintegration and annihilation of the fission product on the basis of neutron detected output. Constitution: The neutron flux in a reactor is detected by a detector, and applied to first and second density calculators. Second fission product density signal of xenon or the like outputted from first device is again inputted to the device to form an annihilation signal due to disintegration to determine the present density of the second fission product of xenon or the like corresponding to the decrease of the neutron due to the poison of xeron or the like. Similarly, second device determines the first fission product density of iodine or the like. (Sekiya, K.)
Level density from realistic nuclear potentials
International Nuclear Information System (INIS)
Calboreanu, A.
2006-01-01
Nuclear level density of some nuclei is calculated using a realistic set of single particle states (sps). These states are derived from the parameterization of nuclear potentials that describe the observed sps over a large number of nuclei. This approach has the advantage that one can infer level density for nuclei that are inaccessible for a direct study, but are very important in astrophysical processes such as those close to the drip lines. Level densities at high excitation energies are very sensitive to the actual set of sps. The fact that the sps spectrum is finite has extraordinary consequences upon nuclear reaction yields due to the leveling-off of the level density at extremely high excitation energies wrongly attributed so far to other nuclear effects. Single-particle level density parameter a parameter is extracted by fitting the calculated densities to the standard Bethe formula
Density of states functions for photonic crystals
International Nuclear Information System (INIS)
McPhedran, R.C.; McOrist, J.; Sterke, C.M. de; Nicorovici, N.A.; Botten, L.C.; Asatryan, A.A.
2004-01-01
We discuss density of states functions for photonic crystals, in the context of the two-dimensional problem for arrays of cylinders of arbitrary cross section. We introduce the mutual density of states (MDOS), and show that this function can be used to calculate both the local density of states (LDOS), which gives position information for emission of radiation from photonic crystals, and the spectral density of states (SDOS), which gives angular information. We establish the connection between MDOS, LDOS, SDOS and the conventional density of states, which depends only on frequency. We relate all four functions to the band structure and propagating states within the crystal, and give numerical examples of the relation between band structure and density of states functions
ITER Experts' meeting on density limits
International Nuclear Information System (INIS)
Borrass, K.; Igitkhanov, Y.L.; Uckan, N.A.
1989-12-01
The necessity of achieving a prescribed wall load or fusion power essentially determines the plasma pressure in a device like ITER. The range of operation densities and temperatures compatible with this condition is constrained by the problems of power exhaust and the disruptive density limit. The maximum allowable heat loads on the divertor plates and the maximum allowable sheath edge temperature practically impose a lower limit on the operating densities, whereas the disruptive density limit imposes an upper limit. For most of the density limit scalings proposed in the past an overlap of the two constraints or at best a very narrow accessible density range is predicted for ITER. Improved understanding of the underlying mechanisms is therefore a crucial issue in order to provide a more reliable basis for extrapolation to ITER and to identify possible ways of alleviating the problem
A Density Functional Theory Study
Lim, XiaoZhi
2011-12-11
Complexes with pincer ligand moieties have garnered much attention in the past few decades. They have been shown to be highly active catalysts in several known transition metal-catalyzed organic reactions as well as some unprecedented organic transformations. At the same time, the use of computational organometallic chemistry to aid in the understanding of the mechanisms in organometallic catalysis for the development of improved catalysts is on the rise. While it was common in earlier studies to reduce computational cost by truncating donor group substituents on complexes such as tertbutyl or isopropyl groups to hydrogen or methyl groups, recent advancements in the processing capabilities of computer clusters and codes have streamlined the time required for calculations. As the full modeling of complexes become increasingly popular, a commonly overlooked aspect, especially in the case of complexes bearing isopropyl substituents, is the conformational analysis of complexes. Isopropyl groups generate a different conformer with each 120 ° rotation (rotamer), and it has been found that each rotamer typically resides in its own potential energy well in density functional theory studies. As a result, it can be challenging to select the most appropriate structure for a theoretical study, as the adjustment of isopropyl substituents from a higher-energy rotamer to the lowest-energy rotamer usually does not occur during structure optimization. In this report, the influence of the arrangement of isopropyl substituents in pincer complexes on calculated complex structure energies as well as a case study on the mechanism of the isomerization of an iPrPCP-Fe complex is covered. It was found that as many as 324 rotamers can be generated for a single complex, as in the case of an iPrPCP-Ni formato complex, with the energy difference between the global minimum and the highest local minimum being as large as 16.5 kcalmol-1. In the isomerization of a iPrPCP-Fe complex, it was found
Model SM-1 ballast density gauge
International Nuclear Information System (INIS)
Gao Weixiang; Fang Jidong; Zhang Xuejuan; Zhang Reilin; Gao Wanshan
1990-05-01
The ballast density is one of the principal parameters for roadbed operating state. It greatly affects the railroad stability, the accumulation of railroad residual deformation and the amount of work for railroad maintenance. SM-1 ballast density gauge is designed to determine the density of ballast by using the effect of γ-ray passed through the ballast. Its fundamentals, construction, specifications, application and economic profit are described
Some recent efforts toward high density implosions
International Nuclear Information System (INIS)
McClellan, G.E.
1980-01-01
Some recent Livermore efforts towards achieving high-density implosions are presented. The implosion dynamics necessary to compress DT fuel to 10 to 100 times liquid density are discussed. Methods of diagnosing the maximum DT density for a specific design are presented along with results to date. The dynamics of the double-shelled target with an exploding outer shell are described, and some preliminary experimental results are presented
The urban density premium across establishments
R. Jason Faberman; Matthew Freedman
2013-01-01
We use longitudinal microdata to estimate the urban density premium for U.S. establishments, controlling for observed establishment characteristics and dynamic establishment behavior. Consistent with previous studies, we estimate a density premium between 6 and 10 percent, even after controlling for establishment composition, local skill mix, and the endogeneity of location choice. More importantly, we find that the estimated density premium is realized almost entirely at birth and is constan...
Moments expansion densities for quantifying financial risk
Ñíguez, T.M.; Perote, J.
2017-01-01
We propose a novel semi-nonparametric distribution that is feasibly parameterized to represent the non-Gaussianities of the asset return distributions. Our Moments Expansion (ME) density presents gains in simplicity attributable to its innovative polynomials, which are defined by the difference between the nth power of the random variable and the nth moment of the density used as the basis. We show that the Gram-Charlier distribution is a particular case of the ME-type of densities. The latte...
Addendum to ''Density fluctuations in liquid rubidium''
International Nuclear Information System (INIS)
Haan, S.W.; Mountain, R.D.; Hsu, C.S.; Rahman, A.
1980-01-01
We performed molecular-dynamics simulations of liquid rubidium and the Lennard-Jones fluid at several densities and temperatures, and of a system whose pair potential is the repulsive core of the rubidium potential. In all cases, propagating density fluctuations occurred in the rubidiumlike systems at much shorter wavelengths than in the Lennard-Jones system. This indicates that the repulsive part of the pair potential is the dominant factor in determining the relaxation of short-wavelength density fluctuations
Density limit studies on DIII-D
Energy Technology Data Exchange (ETDEWEB)
Maingi, R. [Oak Ridge National Lab., TN (United States); Mahdavi, M.A.; Petrie, T.W. [General Atomics, San Diego, CA (United States)] [and others
1998-08-01
The authors have studied the processes limiting plasma density and successfully achieved discharges with density {approximately}50% above the empirical Greenwald density limit with H-mode confinement. This was accomplished by density profile control, enabled through pellet injection and divertor pumping. By examining carefully the criterion for MARFE formation, the authors have derived an edge density limit with scaling very similar to Greenwald scaling. Finally, they have looked in detail at the first and most common density limit process in DIII-D, total divertor detachment, and found that the local upstream separatrix density (n{sub e}{sup sep,det}) at detachment onset (partial detachment) increases with the scrape-off layer heating power, P{sub heat}, i.e., n{sub e}{sup sep,det} {approximately} P{sub heat}{sup 0.76}. This is in marked contrast to the line-average density at detachment which is insensitive to the heating power. The data are in reasonable agreement with the Borass model, which predicted that the upstream density at detachment would increase as P{sub heat}{sup 0.7}.
A classical density functional investigation of nucleation
International Nuclear Information System (INIS)
Ghosh, Satinath; Ghosh, Swapan K.
2009-01-01
Study of nucleation and growth phenomena in condensation is of prime importance in various applications such as crystal growth, nanoparticle synthesis, pattern formation etc. The knowledge of nucleation barrier in condensation is necessary to control the nucleation kinetics, size of the nanoparticles etc. Classical nucleation theory (CNT) assumes the density of the drop as bulk density irrespective of the size of the drop and overestimates the nucleation barrier. Here we are interested in solving the problem analytically using density functional theory (DFT) with square gradient approximation along the lines of Cahn and Hilliard. Nucleation barrier and density profile obtained in this work are consistent with other works based on nonclassical theory. (author)
Digital radioisotope moisture-density meter
International Nuclear Information System (INIS)
Bychvarov, N.; Vankov, I.; Dimitrov, L.
1982-01-01
The primary information from the detectors of a combined radioisotope moisture-density meter is obtained as pulses, their counting rate being functionally dependent on the humidity per unit volume and the wet density. However, most practical cases demand information on the moisture per unit weight and the mass density of the dry skeleton. The paper describes how the proposed electronic circuit processes the input primary information to obtain the moisture in weight % and the mass density of the dry skeleton in g/cm 3 . (authors)
Density limit studies on DIII-D
International Nuclear Information System (INIS)
Maingi, R.; Mahdavi, M.A.; Petrie, T.W.
1998-08-01
The authors have studied the processes limiting plasma density and successfully achieved discharges with density ∼50% above the empirical Greenwald density limit with H-mode confinement. This was accomplished by density profile control, enabled through pellet injection and divertor pumping. By examining carefully the criterion for MARFE formation, the authors have derived an edge density limit with scaling very similar to Greenwald scaling. Finally, they have looked in detail at the first and most common density limit process in DIII-D, total divertor detachment, and found that the local upstream separatrix density (n e sep,det ) at detachment onset (partial detachment) increases with the scrape-off layer heating power, P heat , i.e., n e sep,det ∼ P heat 0.76 . This is in marked contrast to the line-average density at detachment which is insensitive to the heating power. The data are in reasonable agreement with the Borass model, which predicted that the upstream density at detachment would increase as P heat 0.7
High density harp for SSCL linac
International Nuclear Information System (INIS)
Fritsche, C.T.; Krogh, M.L.; Crist, C.E.
1993-01-01
AlliedSignal Inc., Kansas City Division, and the Superconducting Super Collider Laboratory (SSCL) are collaboratively developing a high density harp for the SSCL linac. This harp is designed using hybrid microcircuit (HMC) technology to obtain a higher wire density than previously available. The developed harp contains one hundred twenty-eight 33-micron-diameter carbon wires on 0.38-mm centers. The harp features an onboard broken wire detection circuit. Carbon wire preparation and attachment processes were developed. High density surface mount connectors were located. The status of high density harp development will be presented along with planned future activities
High density harp for SSCL linac
International Nuclear Information System (INIS)
Fritsche, C.T.; Krogh, M.L.
1993-05-01
AlliedSignal Inc., Kansas City Division, and the Superconducting Super Collider Laboratory (SSCL) are collaboratively developing a high density harp for the SSCL linac. This harp is designed using hybrid microcircuit (HMC) technology to obtain a higher wire density than previously available. The developed harp contains one hundred twenty-eight 33-micron-diameter carbon wires on 0.38-mm centers. The harp features an onboard broken wire detection circuit. Carbon wire preparation and attachment processes were developed. High density surface mount connectors were located. The status of high density harp development will be presented along with planned future activities
Precision density measuring equipment: Design, selected examples
International Nuclear Information System (INIS)
Karasinski, T.; Patzelt, K.; Dieker, C.; Hansen, H.; Wenzl, H.; Schober, T.
1987-06-01
The report deals with solids density measurement using the pyknometer, the hydrostatic balance, or the floating specimen method. The mathematical relations are derived, and error sources are shown. A detailed description is given of a measuring set-up for measuring the density of solids and liquids. An error calculation is presented. After explaining the determination of density of a standard solid body, the report describes the density measurement of monocrystalline germanium, of niobium-tritide, Ni 3 Al, Ge-Si, and gallium arsenide, the determination of space-lattice expansion by hydrogen isotopes, and of the purity of H-D mixtures. (GG) [de
Magnetization of High Density Hadronic Fluid
DEFF Research Database (Denmark)
Bohr, Henrik; Providencia, Constanca; da Providencia, João
2012-01-01
In the present paper the magnetization of a high density relativistic fluid of elementary particles is studied. At very high densities, such as may be found in the interior of a neutron star, when the external magnetic field is gradually increased, the energy of the normal phase of the fluid...... in the particle fluid. For nuclear densities above 2 to 3 rho(0), where rho(0) is the equilibrium nuclear density, the resulting magnetic field turns out to be rather huge, of the order of 10(17) Gauss....
Spatial mapping of humeral head bone density.
Alidousti, Hamidreza; Giles, Joshua W; Emery, Roger J H; Jeffers, Jonathan
2017-09-01
Short-stem humeral replacements achieve fixation by anchoring to the metaphyseal trabecular bone. Fixing the implant in high-density bone can provide strong fixation and reduce the risk of loosening. However, there is a lack of data mapping the bone density distribution in the proximal humerus. The aim of the study was to investigate the bone density in proximal humerus. Eight computed tomography scans of healthy cadaveric humeri were used to map bone density distribution in the humeral head. The proximal humeral head was divided into 12 slices parallel to the humeral anatomic neck. Each slice was then divided into 4 concentric circles. The slices below the anatomic neck, where short-stem implants have their fixation features, were further divided into radial sectors. The average bone density for each of these regions was calculated, and regions of interest were compared using a repeated-measures analysis of variance with significance set at P density was found to decrease from proximal to distal regions, with the majority of higher bone density proximal to the anatomic neck of the humerus (P density increases from central to peripheral regions, where cortical bone eventually occupies the space (P density distribution in the medial calcar region was also observed. This study indicates that it is advantageous with respect to implant fixation to preserve some bone above the anatomic neck and epiphyseal plate and to use the denser bone at the periphery. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
Concrete density estimation by rebound hammer method
International Nuclear Information System (INIS)
Ismail, Mohamad Pauzi bin; Masenwat, Noor Azreen bin; Sani, Suhairy bin; Mohd, Shukri; Jefri, Muhamad Hafizie Bin; Abdullah, Mahadzir Bin; Isa, Nasharuddin bin; Mahmud, Mohamad Haniza bin
2016-01-01
Concrete is the most common and cheap material for radiation shielding. Compressive strength is the main parameter checked for determining concrete quality. However, for shielding purposes density is the parameter that needs to be considered. X- and -gamma radiations are effectively absorbed by a material with high atomic number and high density such as concrete. The high strength normally implies to higher density in concrete but this is not always true. This paper explains and discusses the correlation between rebound hammer testing and density for concrete containing hematite aggregates. A comparison is also made with normal concrete i.e. concrete containing crushed granite
What Exactly is a Parton Density ?
International Nuclear Information System (INIS)
Collins, J.C.
2003-01-01
I give an account of the definitions of parton densities, both the conventional ones, integrated over parton transverse momentum, and unintegrated transverse-momentum-dependent densities. The aim is to get a precise and correct definition of a parton density as the target expectation value of a suitable quantum mechanical operator, so that a clear connection to non-perturbative QCD is provided. Starting from the intuitive ideas in the parton model that predate QCD, we will see how the simplest operator definitions suffer from divergences. Corrections to the definition are needed to eliminate the divergences. An improved definition of unintegrated parton densities is proposed. (author)
Nonspherical atomic ground-state densities and chemical deformation densities from x-ray scattering
International Nuclear Information System (INIS)
Ruedenberg, K.; Schwarz, W.H.E.
1990-01-01
Presuming that chemical insight can be gained from the difference between the molecular electron density and the superposition of the ground-state densities of the atoms in a molecule, it is pointed out that, for atoms with degenerate ground states, an unpromoted ''atom in a molecule'' is represented by a specific ensemble of the degenerate atomic ground-state wave functions and that this ensemble is determined by the anisotropic local surroundings. The resulting atomic density contributions are termed oriented ground state densities, and the corresponding density difference is called the chemical deformation density. The constraints implied by this conceptual approach for the atomic density contributions are formulated and a method is developed for determining them from x-ray scattering data. The electron density of the appropriate promolecule and its x-ray scattering are derived, the determination of the parameters of the promolecule is outlined, and the chemical deformation density is formulated
Density measurements of small amounts of high-density solids by a floatation method
International Nuclear Information System (INIS)
Akabori, Mitsuo; Shiba, Koreyuki
1984-09-01
A floatation method for determining the density of small amounts of high-density solids is described. The use of a float combined with an appropriate floatation liquid allows us to measure the density of high-density substances in small amounts. Using the sample of 0.1 g in weight, the floatation liquid of 3.0 g cm -3 in density and the float of 1.5 g cm -3 in apparent density, the sample densities of 5, 10 and 20 g cm -3 are determined to an accuracy better than +-0.002, +-0.01 and +-0.05 g cm -3 , respectively that correspond to about +-1 x 10 -5 cm 3 in volume. By means of appropriate degassing treatments, the densities of (Th,U)O 2 pellets of --0.1 g in weight and --9.55 g cm -3 in density were determined with an accuracy better than +-0.05 %. (author)
International Nuclear Information System (INIS)
Singh, M.P.; Tewari, B.S.; Ajay
2006-01-01
In the present work, we have studied the effect of temperature and carrier density on anisotropy in supercurrent density in bilayer cuprate superconductors. Here, we have considered a tight binding bilayered Hubbard Hamiltonian containing intra and interlayer attractive interactions. The situation considered here is similar to a SIS junction. We have got the expressions for the superconducting order parameters, carrier density and anisotropy in superconducting density (I ab /I c ) for such SIS junction. The numerical analysis show that the anisotropy in the supercurrent density depends on temperature and carrier density in layered high T c cuprates. (author)
The density limit in JET diverted plasmas
Energy Technology Data Exchange (ETDEWEB)
Campbell, D J; Clement, S; Gottardi, N; Gowers, C; Harbour, P; Loarte, A; Horton, L; Lingertat, J; Lowry, C G; Saibene, G; Stamp, M; Stork, D [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Monk, R [Royal Holloway Coll., London (United Kingdom). Dept. of Physics
1994-07-01
In JET limiter plasmas the density limit is associated with radiated power fractions of 100% and, in plasmas with carbon limiters, it is invariably disruptive. However, in discharges with solid beryllium limiters the limit is identified with the formation of a MARFE and disruptions are less frequent. In addition, the improved conditioning of the vessel arising from the use of beryllium has significantly improved the density limit scaling, so that the maximum density rises with the square root of the input power. In diverted plasmas several confinement regimes exist, making the characterization of the density limit more complex. While the density limit in L-mode plasmas is generally disruptive, the limit in ELMy and ELM-free H-modes generally prompts a return to the L-mode and a disruption is not inevitable. The density limit does rise with the increasing power, but the L-to-H transition complicates the analysis. Nevertheless, at low plasma currents (<2 MA), densities significantly above the Greenwald limit can be achieved, while at higher currents power handling limitations have constrained the range of density which can be achieved. (authors). 7 refs., 4 figs.
Enhancing critical current density of cuprate superconductors
Chaudhari, Praveen
2015-06-16
The present invention concerns the enhancement of critical current densities in cuprate superconductors. Such enhancement of critical current densities include using wave function symmetry and restricting movement of Abrikosov (A) vortices, Josephson (J) vortices, or Abrikosov-Josephson (A-J) vortices by using the half integer vortices associated with d-wave symmetry present in the grain boundary.
Absolute density measurements in the middle atmosphere
Directory of Open Access Journals (Sweden)
M. Rapp
2001-05-01
Full Text Available In the last ten years a total of 25 sounding rockets employing ionization gauges have been launched at high latitudes ( ~ 70° N to measure total atmospheric density and its small scale fluctuations in an altitude range between 70 and 110 km. While the determination of small scale fluctuations is unambiguous, the total density analysis has been complicated in the past by aerodynamical disturbances leading to densities inside the sensor which are enhanced compared to atmospheric values. Here, we present the results of both Monte Carlo simulations and wind tunnel measurements to quantify this aerodynamical effect. The comparison of the resulting ‘ram-factor’ profiles with empirically determined density ratios of ionization gauge measurements and falling sphere measurements provides excellent agreement. This demonstrates both the need, but also the possibility, to correct aerodynamical influences on measurements from sounding rockets. We have determined a total of 20 density profiles of the mesosphere-lower-thermosphere (MLT region. Grouping these profiles according to season, a listing of mean density profiles is included in the paper. A comparison with density profiles taken from the reference atmospheres CIRA86 and MSIS90 results in differences of up to 40%. This reflects that current reference atmospheres are a significant potential error source for the determination of mixing ratios of, for example, trace gas constituents in the MLT region.Key words. Middle atmosphere (composition and chemistry; pressure, density, and temperature; instruments and techniques
517 DWELLING DENSITY VARIABILITY ACROSS GOVERNMENT ...
African Journals Online (AJOL)
Osondu
confidence level, apartment type had no significant effect on dwelling density in ... words: dwelling density, home spaces, housing units, multifamily apartments ... spaces for work, Obateru (2005) defined .... of Statistics Year Book, 2008; Seeling et al., ... stress. The bedroom and habitable room indicators show similar trend.
Absolute density measurements in the middle atmosphere
Directory of Open Access Journals (Sweden)
M. Rapp
Full Text Available In the last ten years a total of 25 sounding rockets employing ionization gauges have been launched at high latitudes ( ~ 70° N to measure total atmospheric density and its small scale fluctuations in an altitude range between 70 and 110 km. While the determination of small scale fluctuations is unambiguous, the total density analysis has been complicated in the past by aerodynamical disturbances leading to densities inside the sensor which are enhanced compared to atmospheric values. Here, we present the results of both Monte Carlo simulations and wind tunnel measurements to quantify this aerodynamical effect. The comparison of the resulting ‘ram-factor’ profiles with empirically determined density ratios of ionization gauge measurements and falling sphere measurements provides excellent agreement. This demonstrates both the need, but also the possibility, to correct aerodynamical influences on measurements from sounding rockets. We have determined a total of 20 density profiles of the mesosphere-lower-thermosphere (MLT region. Grouping these profiles according to season, a listing of mean density profiles is included in the paper. A comparison with density profiles taken from the reference atmospheres CIRA86 and MSIS90 results in differences of up to 40%. This reflects that current reference atmospheres are a significant potential error source for the determination of mixing ratios of, for example, trace gas constituents in the MLT region.
Key words. Middle atmosphere (composition and chemistry; pressure, density, and temperature; instruments and techniques
Electronic DC transformer with high power density
Pavlovský, M.
2006-01-01
This thesis is concerned with the possibilities of increasing the power density of high-power dc-dc converters with galvanic isolation. Three cornerstones for reaching high power densities are identified as: size reduction of passive components, reduction of losses particularly in active components
All Hazard Hotspots/Population Density
Indian Academy of Sciences (India)
This map shows hotspots of humanitarian risk for floods, cyclones, and drought overlaying a population density gradient. Blue areas with striped overlay represent areas of high population density that are also risk hotspots. These are at higher risk of future population displacement as a result of climate hazards.
Fast response densitometer for measuring liquid density
1972-01-01
Densitometer was developed which produces linear voltage proportional to changes in density of flowing liquid hydrogen. Unit has fast response time and good system stability, statistical variation, and thermal equilibrium. System accuracy is 2 percent of total density span. Basic design may be altered to include measurement of other flowing materials.
The Fourier transform of tubular densities
Prior, C B; Goriely, A
2012-01-01
molecules. We consider tubes of both finite radii and unrestricted radius. When there is overlap of the tube structure the net density is calculated using the super-position principle. The Fourier transform of this density is composed of two expressions, one
Density functional theory and multiscale materials modeling
Indian Academy of Sciences (India)
One of the vital ingredients in the theoretical tools useful in materials modeling at all the length scales of interest is the concept of density. In the microscopic length scale, it is the electron density that has played a major role in providing a deeper understanding of chemical binding in atoms, molecules and solids.
A multiconfigurational hybrid density-functional theory
DEFF Research Database (Denmark)
Sharkas, Kamal; Savin, Andreas; Jensen, Hans Jørgen Aagaard
2012-01-01
We propose a multiconfigurational hybrid density-functional theory which rigorously combines a multiconfiguration self-consistent-field calculation with a density-functional approximation based on a linear decomposition of the electron-electron interaction. This gives a straightforward extension ...
Synthesizing chaotic maps with prescribed invariant densities
International Nuclear Information System (INIS)
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 Letter, 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
Analyticity of the density of electronic wavefunctions
DEFF Research Database (Denmark)
Fournais, Søren; Hoffmann-Ostenhof, Maria; Hoffmann-Ostenhof, Thomas
2004-01-01
We prove that the electronic densities of atomic and molecular eigenfunctions are real analytic in R^3 away from the nuclei.......We prove that the electronic densities of atomic and molecular eigenfunctions are real analytic in R^3 away from the nuclei....
The Thermal Entropy Density of Spacetime
Directory of Open Access Journals (Sweden)
Rongjia Yang
2013-01-01
Full Text Available Introducing the notion of thermal entropy density via the first law of thermodynamics and assuming the Einstein equation as an equation of thermal state, we obtain the thermal entropy density of any arbitrary spacetime without assuming a temperature or a horizon. The results confirm that there is a profound connection between gravity and thermodynamics.
Microinstabilities in weak density gradient tokamak systems
International Nuclear Information System (INIS)
Tang, W.M.; Rewoldt, G.; Chen, L.
1986-04-01
A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient
Polarizable Density Embedding Coupled Cluster Method
DEFF Research Database (Denmark)
Hršak, Dalibor; Olsen, Jógvan Magnus Haugaard; Kongsted, Jacob
2018-01-01
by an embedding potential consisting of a set of fragment densities obtained from calculations on isolated fragments with a quantum-chemistry method such as Hartree-Fock (HF) or Kohn-Sham density functional theory (KS-DFT) and dressed with a set of atom-centered anisotropic dipole-dipole polarizabilities...
Locality of correlation in density functional theory
Energy Technology Data Exchange (ETDEWEB)
Burke, Kieron [Department of Chemistry, University of California, Irvine, California 92697 (United States); Cancio, Antonio [Department of Physics and Astronomy, Ball State University, Muncie, Indiana 47306 (United States); Gould, Tim [Qld Micro- and Nanotechnology Centre, Griffith University, Nathan, Qld 4111 (Australia); Pittalis, Stefano [CNR-Istituto di Nanoscienze, Via Campi 213A, I-41125 Modena (Italy)
2016-08-07
The Hohenberg-Kohn density functional was long ago shown to reduce to the Thomas-Fermi (TF) approximation in the non-relativistic semiclassical (or large-Z) limit for all matter, i.e., the kinetic energy becomes local. Exchange also becomes local in this limit. Numerical data on the correlation energy of atoms support the conjecture that this is also true for correlation, but much less relevant to atoms. We illustrate how expansions around a large particle number are equivalent to local density approximations and their strong relevance to density functional approximations. Analyzing highly accurate atomic correlation energies, we show that E{sub C} → −A{sub C} ZlnZ + B{sub C}Z as Z → ∞, where Z is the atomic number, A{sub C} is known, and we estimate B{sub C} to be about 37 mhartree. The local density approximation yields A{sub C} exactly, but a very incorrect value for B{sub C}, showing that the local approximation is less relevant for the correlation alone. This limit is a benchmark for the non-empirical construction of density functional approximations. We conjecture that, beyond atoms, the leading correction to the local density approximation in the large-Z limit generally takes this form, but with B{sub C} a functional of the TF density for the system. The implications for the construction of approximate density functionals are discussed.
New aspects of high energy density plasma
International Nuclear Information System (INIS)
Hotta, Eiki
2005-10-01
The papers presented at the symposium on 'New aspects of high energy density plasma' held at National Institute for Fusion Science are collected in this proceedings. The papers reflect the present status and recent progress in the experiments and theoretical works on high energy density plasma produced by pulsed power technology. The 13 of the presented papers are indexed individually. (J.P.N.)
Magnetosheath density fluctuations and magnetopause motion
Energy Technology Data Exchange (ETDEWEB)
Sibeck, D.G. [Johns Hopkins Univ. Applied Physics Lab., Laurel, MD (United States); Gosling, J.T. [Los Alamos National Lab., NM (United States)
1996-01-01
The interplanetary magnetic field (IMF) orientation controls foreshock densities and modulates the fraction of the solar wind dynamic pressure applied to the magnetosphere. Such pressure variations produce bow shock and magnetopause motion and cause the radial profiles for various magnetosheath parameters to sweep inward and outward past nearly stationary satellites. The authors report ISEE 2 observations of correlated density and speed fluctuations, and anticorrelated density and temperature fluctuations, on an outbound pass through the northern dawnside magnetosheath. Densities decreased when the magnetic field rotated southward and draped about the magnetopause. In the absence of any significant solar wind density or dynamic pressure variations, they interpret the magnetosheath fluctuations as evidence for radial magnetosheath motion induced by variations in the IMF orientation. 41 refs., 8 figs.
Epidemiologic Studies of Isoflavones & Mammographic Density
Maskarinec, Gertraud; Verheus, Martijn; Tice, Jeffrey A.
2010-01-01
Isoflavones, phytoestrogens in soy beans with estrogen-like properties, have been examined for their cancer protective effects. Mammographic density is a strong predictor of breast cancer. This review summarizes studies that have examined the association between isoflavones and breast density. Observational investigations in Hawaii and Singapore suggest slightly lower breast density among women of Asian descent with regular soy intake, but two larger studies from Japan and Singapore did not observe a protective effect. The findings from seven randomized trials with primarily Caucasian women indicate that soy or isoflavones do not modify mammographic density. Soy foods and isoflavone supplements within a nutritional range do not appear to modify breast cancer risk as assessed by mammographic density. PMID:22253990
Epidemiologic Studies of Isoflavones & Mammographic Density
Directory of Open Access Journals (Sweden)
Jeffrey A. Tice
2010-01-01
Full Text Available Isoflavones, phytoestrogens in soy beans with estrogen-like properties, have been examined for their cancer protective effects. Mammographic density is a strong predictor of breast cancer. This review summarizes studies that have examined the association between isoflavones and breast density. Observational investigations in Hawaii and Singapore suggest slightly lower breast density among women of Asian descent with regular soy intake, but two larger studies from Japan and Singapore did not observe a protective effect. The findings from seven randomized trials with primarily Caucasian women indicate that soy or isoflavones do not modify mammographic density. Soy foods and isoflavone supplements within a nutritional range do not appear to modify breast cancer risk as assessed by mammographic density.
Whistler wave trapping in a density crest
International Nuclear Information System (INIS)
Sugai, H.; Niki, H.; Inutake, M.; Takeda, S.
1979-11-01
The linear trapping process of whistler waves in a field-aligned density crest is investigated theoretically and experimentally below ω = ωsub(c)/2 (half gyrofrequency). The conditions of the crest trapping are derived in terms of the frequency ω/ωsub(c), the incident wave-normal angle theta sub(i), and the density ratio n sub(i)/n sub(o), where n sub(i) and n sub(o) denote the density at the incident point and that at the ridge, respectively. The oscillation length of the trapped ray path is calculated for a parabolic density profile. The experiment on antenna-excited whistler wave has been performed in a large magnetized plasma with the density crest. The phase and amplitude profile of the whistler wave is measured along and across the crest. The measurement has verified characteristic behaviors of the crest trapping. (author)
Mechanisms Affecting Population Density in Fragmented Habitat
Directory of Open Access Journals (Sweden)
Lutz Tischendorf
2005-06-01
Full Text Available We conducted a factorial simulation experiment to analyze the relative importance of movement pattern, boundary-crossing probability, and mortality in habitat and matrix on population density, and its dependency on habitat fragmentation, as well as inter-patch distance. We also examined how the initial response of a species to a fragmentation event may affect our observations of population density in post-fragmentation experiments. We found that the boundary-crossing probability from habitat to matrix, which partly determines the emigration rate, is the most important determinant for population density within habitat patches. The probability of crossing a boundary from matrix to habitat had a weaker, but positive, effect on population density. Movement behavior in habitat had a stronger effect on population density than movement behavior in matrix. Habitat fragmentation and inter-patch distance may have a positive or negative effect on population density. The direction of both effects depends on two factors. First, when the boundary-crossing probability from habitat to matrix is high, population density may decline with increasing habitat fragmentation. Conversely, for species with a high matrix-to-habitat boundary-crossing probability, population density may increase with increasing habitat fragmentation. Second, the initial distribution of individuals across the landscape: we found that habitat fragmentation and inter-patch distance were positively correlated with population density when individuals were distributed across matrix and habitat at the beginning of our simulation experiments. The direction of these relationships changed to negative when individuals were initially distributed across habitat only. Our findings imply that the speed of the initial response of organisms to habitat fragmentation events may determine the direction of observed relationships between habitat fragmentation and population density. The time scale of post
Multicomponent density functional theory embedding formulation
Energy Technology Data Exchange (ETDEWEB)
Culpitt, Tanner; Brorsen, Kurt R.; Pak, Michael V.; Hammes-Schiffer, Sharon, E-mail: shs3@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Ave, Urbana, Illinois 61801 (United States)
2016-07-28
Multicomponent density functional theory (DFT) methods have been developed to treat two types of particles, such as electrons and nuclei, quantum mechanically at the same level. In the nuclear-electronic orbital (NEO) approach, all electrons and select nuclei, typically key protons, are treated quantum mechanically. For multicomponent DFT methods developed within the NEO framework, electron-proton correlation functionals based on explicitly correlated wavefunctions have been designed and used in conjunction with well-established electronic exchange-correlation functionals. Herein a general theory for multicomponent embedded DFT is developed to enable the accurate treatment of larger systems. In the general theory, the total electronic density is separated into two subsystem densities, denoted as regular and special, and different electron-proton correlation functionals are used for these two electronic densities. In the specific implementation, the special electron density is defined in terms of spatially localized Kohn-Sham electronic orbitals, and electron-proton correlation is included only for the special electron density. The electron-proton correlation functional depends on only the special electron density and the proton density, whereas the electronic exchange-correlation functional depends on the total electronic density. This scheme includes the essential electron-proton correlation, which is a relatively local effect, as well as the electronic exchange-correlation for the entire system. This multicomponent DFT-in-DFT embedding theory is applied to the HCN and FHF{sup −} molecules in conjunction with two different electron-proton correlation functionals and three different electronic exchange-correlation functionals. The results illustrate that this approach provides qualitatively accurate nuclear densities in a computationally tractable manner. The general theory is also easily extended to other types of partitioning schemes for multicomponent systems.
Fu, Shuangcheng; Fang, Yong; Yuan, Huixin; Tan, Wanjiang; Dong, Yiwen
2017-09-01
Hydrocyclones can be applied to recycle waste plastics with different densities through separating plastics based on their differences in densities. In the process, the medium density is one of key parameters and the value of the medium's density is not just the average of the density of two kinds of plastics separated. Based on the force analysis and establishing the equation of motion of particles in the hydrocyclone, a formula to calculate the optimum separation medium density has been deduced. This value of the medium's density is a function of various parameters including the diameter, density, radial position and tangential velocity of particles, and viscosity of the medium. Tests on the separation performance of the hydrocyclone has been conducted with PET and PVC particles. The theoretical result appeared to be in good agreement with experimental results. Copyright © 2017 Elsevier Ltd. All rights reserved.
External field as the functional of inhomogeneous density and the density matrix functional approach
Bobrov, V.B.; Trigger, S.A.; Vlasov, Y.P.
2012-01-01
Based on the Hohenberg-Kohn lemma and the hypotheses of the density functional existence for the external-field potential, it is shown that the strict result of the density functional theory is the equation of the external-field potential as the density functional. This result leads to the
Periodic subsystem density-functional theory
International Nuclear Information System (INIS)
Genova, Alessandro; Pavanello, Michele; Ceresoli, Davide
2014-01-01
By partitioning the electron density into subsystem contributions, the Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) has recently emerged as a powerful tool for reducing the computational scaling of Kohn–Sham DFT. To date, however, FDE has been employed to molecular systems only. Periodic systems, such as metals, semiconductors, and other crystalline solids have been outside the applicability of FDE, mostly because of the lack of a periodic FDE implementation. To fill this gap, in this work we aim at extending FDE to treat subsystems of molecular and periodic character. This goal is achieved by a dual approach. On one side, the development of a theoretical framework for periodic subsystem DFT. On the other, the realization of the method into a parallel computer code. We find that periodic FDE is capable of reproducing total electron densities and (to a lesser extent) also interaction energies of molecular systems weakly interacting with metallic surfaces. In the pilot calculations considered, we find that FDE fails in those cases where there is appreciable density overlap between the subsystems. Conversely, we find FDE to be in semiquantitative agreement with Kohn–Sham DFT when the inter-subsystem density overlap is low. We also conclude that to make FDE a suitable method for describing molecular adsorption at surfaces, kinetic energy density functionals that go beyond the GGA level must be employed
Periodic subsystem density-functional theory
Genova, Alessandro; Ceresoli, Davide; Pavanello, Michele
2014-11-01
By partitioning the electron density into subsystem contributions, the Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) has recently emerged as a powerful tool for reducing the computational scaling of Kohn-Sham DFT. To date, however, FDE has been employed to molecular systems only. Periodic systems, such as metals, semiconductors, and other crystalline solids have been outside the applicability of FDE, mostly because of the lack of a periodic FDE implementation. To fill this gap, in this work we aim at extending FDE to treat subsystems of molecular and periodic character. This goal is achieved by a dual approach. On one side, the development of a theoretical framework for periodic subsystem DFT. On the other, the realization of the method into a parallel computer code. We find that periodic FDE is capable of reproducing total electron densities and (to a lesser extent) also interaction energies of molecular systems weakly interacting with metallic surfaces. In the pilot calculations considered, we find that FDE fails in those cases where there is appreciable density overlap between the subsystems. Conversely, we find FDE to be in semiquantitative agreement with Kohn-Sham DFT when the inter-subsystem density overlap is low. We also conclude that to make FDE a suitable method for describing molecular adsorption at surfaces, kinetic energy density functionals that go beyond the GGA level must be employed.
ADN* Density log estimation Using Rockcell*
International Nuclear Information System (INIS)
Okuku, C.; Iloghalu, Emeka. M.; Omotayo, O.
2003-01-01
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
Density Variations in the Earth's Magnetospheric Cusps
Walsh, B. M.; Niehof, J.; Collier, M. R.; Welling, D. T.; Sibeck, D. G.; Mozer, F. S.; Fritz, T. A.; Kuntz, K. D.
2016-01-01
Seven years of measurements from the Polar spacecraft are surveyed to monitor the variations of plasma density within the magnetospheric cusps. The spacecraft's orbital precession from 1998 through 2005 allows for coverage of both the northern and southern cusps from low altitude out to the magnetopause. In the mid- and high- altitude cusps, plasma density scales well with the solar wind density (n(sub cusp)/n(sub sw) approximately 0.8). This trend is fairly steady for radial distances greater then 4 R(sub E). At low altitudes (r less than 4R(sub E)) the density increases with decreasing altitude and even exceeds the solar wind density due to contributions from the ionosphere. The density of high charge state oxygen (O(greater +2) also displays a positive trend with solar wind density within the cusp. A multifluid simulation with the Block-Adaptive-Tree Solar Wind Roe-Type Upwind Scheme MHD model was run to monitor the relative contributions of the ionosphere and solar wind plasma within the cusp. The simulation provides similar results to the statistical measurements from Polar and confirms the presence of ionospheric plasma at low altitudes.
Chiral dynamics and peripheral transverse densities
Energy Technology Data Exchange (ETDEWEB)
Granados, Carlos G. [Uppsala University (Sweden); Weiss, Christian [JLAB, Newport News, VA (United States)
2014-01-01
In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M{sub {pi}}{sup -1}) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two--pion threshold at timelike t = 4 M{ sub {pi}}{sup 2}, which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M{sub {pi}}{sup -1}) and the "molecular" region b = O(M{sub N}{sup 2}/M{sub {pi}}{sup 3}); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N{ sub c} limit of QCD; (e) quantify the region of transverse distances where the chiral components of the densities are numerically dominant; (f) calculate the chiral divergences of the b{sup 2}-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M{sub {pi}} -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes.
Zhong, Zai-Zhe
2004-01-01
The partial separability of multipartite qubit density matrixes is strictly defined. We give a reduction way from N-partite qubit density matrixes to bipartite qubit density matrixes, and prove a necessary condition that a N-partite qubit density matrix to be partially separable is its reduced density matrix to satisfy PPT condition.
Hartree--Fock density matrix equation
International Nuclear Information System (INIS)
Cohen, L.; Frishberg, C.
1976-01-01
An equation for the Hartree--Fock density matrix is discussed and the possibility of solving this equation directly for the density matrix instead of solving the Hartree--Fock equation for orbitals is considered. Toward that end the density matrix is expanded in a finite basis to obtain the matrix representative equation. The closed shell case is considered. Two numerical schemes are developed and applied to a number of examples. One example is given where the standard orbital method does not converge while the method presented here does
Heat and density pulse propagation in ASDEX
International Nuclear Information System (INIS)
Giannone, L.; Riedl, K.; Stroth, U.; Eberhagen, A.; Gruber, O.; Mertens, V.
1990-01-01
Experimental measurements of the electron thermal conductivity, derived from the radial propagation of the heat pulse generated by a sawtooth crash, have consistently yielded larger values than those obtained by power balance. It has been proposed that this discrepancy could be the result of the coupling of density and temperature perturbations. Numerical modelling of heat and density pulse propagation on ASDEX has been used to address this question. In addition, measurements at various electron densities and in hydrogen and deuterium were undertaken, with the aim of providing a broad base of experimental measurements for testing the various transport models proposed. (author) 9 refs., 1 fig
Heat and density pulse propagation in ASDEX
International Nuclear Information System (INIS)
Giannone, L.; Riedel, K.; Stroth, U.; Eberhagen, A.; Gruber, O.; Mertens, V.
1990-01-01
Experimental measurements of the electron thermal conductivity, derived from the radial propagation of the heat pulse generated by a sawtooth crash, have consistently yielded larger values than those obtained by power balance. It has been proposed that this discrepancy could be the result of the coupling of density and temperature perturbations. Numerical modelling of heat and density pulse propagation on ASDEX has been used to address this question. In addition, measurements at various electron densities and in hydrogen and deuterium were undertaken, with the aim of providing a broad base of experimental measurements for testing the various transport models proposed. (orig.)
The effect of density gradients on hydrometers
Heinonen, Martti; Sillanpää, Sampo
2003-05-01
Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we studied the effect of non-uniform density of liquid on a hydrometer reading. The effect induced by vertical temperature gradients was investigated theoretically and experimentally. A method for compensating for the effect mathematically was developed and tested with experimental data obtained with the MIKES hydrometer calibration system. In the tests, the method was found reliable. However, the reliability depends on the available information on the hydrometer dimensions and density gradients.
Fluid Density and Impact Cavity Formation
Directory of Open Access Journals (Sweden)
Ga-Chun Lin
2018-01-01
Full Text Available Characteristics of the impact cavity formed when a steel ball is dropped into aqueous solutions of densities ranging from 0.98 g·cm-3 to 1.63 g·cm-3 were investigated. A high-speed camera was used to record the formation and collapse of the cavity. The results showed cavity diameter, volume, and pinch-off time are independent of fluid density, on average. There was an unexplained reduction in cavity formation for densities of 1.34 g·cm-3 and 1.45 g·cm-3.
Spectral density regression for bivariate extremes
Castro Camilo, Daniela
2016-05-11
We introduce a density regression model for the spectral density of a bivariate extreme value distribution, that allows us to assess how extremal dependence can change over a covariate. Inference is performed through a double kernel estimator, which can be seen as an extension of the Nadaraya–Watson estimator where the usual scalar responses are replaced by mean constrained densities on the unit interval. Numerical experiments with the methods illustrate their resilience in a variety of contexts of practical interest. An extreme temperature dataset is used to illustrate our methods. © 2016 Springer-Verlag Berlin Heidelberg
Systematics of nuclear level density parameters
International Nuclear Information System (INIS)
Bucurescu, Dorel; Egidy, Till von
2005-01-01
The level density parameters for the back-shifted Fermi gas (both without and with energy-dependent level density parameter) and the constant temperature models have been determined for 310 nuclei between 18 F and 251 Cf by fitting the complete level schemes at low excitation energies and the s-wave neutron resonance spacings at the neutron binding energies. Simple formulae are proposed for the description of the two parameters of each of these models, which involve only quantities available from the mass tables. These formulae may constitute a reliable tool for extrapolating to nuclei far from stability, where nuclear level densities cannot be measured
Local density approximations for relativistic exchange energies
International Nuclear Information System (INIS)
MacDonald, A.H.
1986-01-01
The use of local density approximations to approximate exchange interactions in relativistic electron systems is reviewed. Particular attention is paid to the physical content of these exchange energies by discussing results for the uniform relativistic electron gas from a new point of view. Work on applying these local density approximations in atoms and solids is reviewed and it is concluded that good accuracy is usually possible provided self-interaction corrections are applied. The local density approximations necessary for spin-polarized relativistic systems are discussed and some new results are presented
Lipid composition of positively buoyant eggs of reef building corals
Arai, Iakayuki; Kato, Misako; Heyward, Andrew; Ikeda, Yutaka; Iizuka, Tokio; Maruyama, Tadashi
1993-07-01
Lipid composition of the eggs of three reef building corals, Acropora millepora, A. tenuis and Montipora digitata, were determined. Sixty to 70% of the egg dry weight was lipid, which consisted of wax esters (69.5 81.8%), triacylglycerols (1.1 8.4%) and polar lipids c/mainly phospholipids (11.9 13.2%). Montipora digitata also contained some polar lipids typical of the thylakoid membrane in chloroplasts, probably due to the presence of symbiotic zooxanthellae in the eggs. The wax esters appeared to be the major contributor to positive buoyancy of the eggs, and specific gravity of wax esters in A. millepora was estimated to be 0.92. Among the fatty acids of the wax esters, 34.9 51.3% was hexadecanoic acid (16:0) while the major fatty acids in polar lipids were octadecenoic acid (18:1), hexadecanoic acid (16:0), eicosapentaenoic acid (20:5) and eicosatetraenoic acid (20:4). The wax ester appears to be the main component of the 4.5 6.0 μm diameter lipid droplets which fill most of the central mass of the coral eggs.
Investigation of slightly forced buoyant flow in a training reactor
International Nuclear Information System (INIS)
Legradi, G.; Aszodi, A.; Por, G.
2001-01-01
A measurement based on the temperature noise analysis method was carried out in the Training Reactor of the Budapest University of Technology and Economics. The main goals were the estimation of the flow velocity immediately above the reactor core and investigation of the thermal-hydraulical conditions of the reactor, mainly in the core. Subsequently 2D and 3D computations were carried out with the aid of the code CFX- 4.3. The main objective of the 2D calculation was to clarify the thermal-hydraulical conditions of the whole reactor tank with a reasonable computing demand. It was also necessary to accomplish 3D numerical investigations of the reactor core and the space above since three dimensional effects of the flow could only be studied in this way. In addition, obtaining certain boundary conditions of the 3D computations was another significant aim of the 2D investigations. It is important that the results of the noise analysis and the operational measuring system of the reactor gave us a basis for verifying our computations.(author)
Characterization of Horizontally-Issuing Reacting Buoyant Jets
2011-03-01
with unparalleled support. I would like to especially thank Mr. John Hixenbaugh whose comical nature and upbeat personality always brightened my day...as the air and fuel mixture navigate circumferentially around the engine. When fuel and air are injected into the UCC, a swirling motion is created...are dominant. As a result, the flow is laminar, characterized by smooth constant motions . Conversely, at high Reynolds numbers, inertial or momentum
Filtered Rayleigh Scattering Measurements in a Buoyant Flow Field
National Research Council Canada - National Science Library
Meents, Steven M
2008-01-01
Filtered Rayleigh Scattering (FRS) is a non-intrusive, laser-based flow characterization technique that consists of a narrow linewidth laser, a molecular absorption filter, and a high resolution camera behind the filter to record images...
Experimental and theoretical studies of buoyant-thermo capillary flow
International Nuclear Information System (INIS)
Favre, E.; Blumenfeld, L.; Soubbaramayer
1996-01-01
In the AVLIS process, uranium metal is evaporated using a high power electron gun. We have prior discussed the power balance equation in the electron beam evaporation process and pointed out, among the loss terms, the importance of the power loss due to the convective flow in the molten pool driven by buoyancy and thermo capillarity. An empirical formula has been derived from model experiments with cerium, to estimate the latter power loss and that formula can be used practically in engineering calculations. In order to complete the empirical approach, a more fundamental research program of theoretical and experimental studies have been carried out in Cea-France, with the objective of understanding the basic phenomena (heat transport, flow instabilities, turbulence, etc.) occurring in a convective flow in a liquid layer locally heated on its free surface
Astronaut Training using Virtual Reality in a Neutrally Buoyant Environment
Everson, Timothy; McDermott, Christopher; Kain, Aaron; Fernandez, Cesar; Horan, Ben
2017-01-01
Astronauts undergo significant training in preparation for operating in space. In the past governments have been driving space exploration through ventures such as the National Aeronautics and Space Administration (NASA), however more recently new private companies have formed such as SpaceX who are designing commercially viable and reusable spacecraft. As such, the economics of space travel are more important than ever, and there is a logical need to research affordable and effective trainin...
Continents as lithological icebergs: The importance of buoyant lithospheric roots
Abbott, D.H.; Drury, R.; Mooney, W.D.
1997-01-01
An understanding of the formation of new continental crust provides an important guide to locating the oldest terrestrial rocks and minerals. We evaluated the crustal thicknesses of the thinnest stable continental crust and of an unsubductable oceanic plateau and used the resulting data to estimate the amount of mantle melting which produces permanent continental crust. The lithospheric mantle is sufficiently depleted to produce permanent buoyancy (i.e., the crust is unsubductable) at crustal thicknesses greater than 25-27 km. These unsubductable oceanic plateaus and hotspot island chains are important sources of new continental crust. The newest continental crust (e.g., the Ontong Java plateau) has a basaltic composition, not a granitic one. The observed structure and geochemistry of continents are the result of convergent margin magmatism and metamorphism which modify the nascent basaltic crust into a lowermost basaltic layer overlain by a more silicic upper crust. The definition of a continent should imply only that the lithosphere is unsubductable over ??? 0.25 Ga time periods. Therefore, the search for the oldest crustal rocks should include rocks from lower to mid-crustal levels.
46 CFR 160.010-3 - Inflatable buoyant apparatus.
2010-10-01
... capacity of 25 or more persons must be provided with self-bailing floor drains. If the floor of a reversible one includes one or more drains, each drain must be arranged to completely drain the floor of... the buoyancy tubes are not vivid reddish orange, vivid yellow, or a fluorescent color of a similar hue...
PIV Measurements in Weakly Buoyant Gas Jet Flames
Sunderland, Peter B.; Greenbberg, Paul S.; Urban, David L.; Wernet, Mark P.; Yanis, William
2001-01-01
Despite numerous experimental investigations, the characterization of microgravity laminar jet diffusion flames remains incomplete. Measurements to date have included shapes, temperatures, soot properties, radiative emissions and compositions, but full-field quantitative measurements of velocity are lacking. Since the differences between normal-gravity and microgravity diffusion flames are fundamentally influenced by changes in velocities, it is imperative that the associated velocity fields be measured in microgravity flames. Velocity measurements in nonbuoyant flames will be helpful both in validating numerical models and in interpreting past microgravity combustion experiments. Pointwise velocity techniques are inadequate for full-field velocity measurements in microgravity facilities. In contrast, Particle Image Velocimetry (PIV) can capture the entire flow field in less than 1% of the time required with Laser Doppler Velocimetry (LDV). Although PIV is a mature diagnostic for normal-gravity flames , restrictions on size, power and data storage complicate these measurements in microgravity. Results from the application of PIV to gas jet flames in normal gravity are presented here. Ethane flames burning at 13, 25 and 50 kPa are considered. These results are presented in more detail in Wernet et al. (2000). The PIV system developed for these measurements recently has been adapted for on-rig use in the NASA Glenn 2.2-second drop tower.
Modeling Highly Buoyant Flows in the Castel Giorgio
Volpi, Giorgio; Magri, Fabien; Colucci, Francesca; Fisher, Thomas; De Caro, Mattia; Crosta, Giovanni B.
2018-01-01
The Castel Giorgio-Torre Alfina (CG-TA, central Italy) is a geothermal reservoir whose fluids are hosted in a carbonate formation at temperatures ranging between 120°C and 210°C. Data from deep wells suggest the existence of convective flow. We present the 3D numerical model of the CG-TA to simulate the undisturbed natural geothermal field and investigate the impacts of the exploitation process. The open source finite-element code OpenGeoSys is applied to solve the coupled systems of partial ...
Spin theory of the density functional: reduced matrices and density functions
International Nuclear Information System (INIS)
Pavlov, R.; Delchev, Y.; Pavlova, K.; Maruani, J.
1993-01-01
Expressions for the reduced matrices and density functions of N-fermion systems of arbitrary order s (1<=s<=N) are derived within the frame of rigorous spin approach to the density functional theory (DFT). Using the local-scale transformation method and taking into account the particle spin it is shown that the reduced matrices and density functions are functionals of the total one-fermion density. Similar dependence is found for the distribution density of s-particle aggregates. Generalization and applicability of DFT to the case of s-particle ensembles and aggregates is discussed. 14 refs
Local-scaling density-functional method: Intraorbit and interorbit density optimizations
International Nuclear Information System (INIS)
Koga, T.; Yamamoto, Y.; Ludena, E.V.
1991-01-01
The recently proposed local-scaling density-functional theory provides us with a practical method for the direct variational determination of the electron density function ρ(r). The structure of ''orbits,'' which ensures the one-to-one correspondence between the electron density ρ(r) and the N-electron wave function Ψ({r k }), is studied in detail. For the realization of the local-scaling density-functional calculations, procedures for intraorbit and interorbit optimizations of the electron density function are proposed. These procedures are numerically illustrated for the helium atom in its ground state at the beyond-Hartree-Fock level
International Nuclear Information System (INIS)
Goss-Custard, J.D.; McGrorty, S.; Clarke, R.T.; Pearson, B.; Rispin, W.E.; Durell, S.E.A. le V. dit; Rose, R.J.; Warwick, R.M.; Kirby, R.
1991-01-01
A winter survey of seven species of wading birds in six estuaries in south-west England was made to develop a method for predicting bird densities should a tidal power barrage be built on the Severn estuary. Within most estuaries, bird densities correlated with the densities of widely taken prey species. A barrage would substantially reduce the area of intertidal flats available at low water for the birds to feed but the invertebrate density could increase in the generally more benign post-barrage environmental conditions. Wader densities would have to increase approximately twofold to allow the same overall numbers of birds to remain post-barrage as occur on the Severn at present. Provisional estimates are given of the increases in prey density required to allow bird densities to increase by this amount. With the exception of the prey of dunlin, these fall well within the ranges of densities found in other estuaries, and so could in principle be attained in the post-barrage Severn. An attempt was made to derive equations with which to predict post-barrage densities of invertebrates from easily measured, static environmental variables. The fact that a site was in the Severn had a significant additional effect on invertebrate density in seven cases. This suggests that there is a special feature of the Severn, probably one associated with its highly dynamic nature. This factor must be identified if the post-barrage densities of invertebrates are to be successful predicted. (author)
True density and apparent density during the drying process for vegetables and fruits: a review.
Rodríguez-Ramírez, J; Méndez-Lagunas, L; López-Ortiz, A; Torres, S Sandoval
2012-12-01
This review presents the concepts involved in determining the density of foodstuffs, and summarizes the volumetric determination techniques used to calculate true density and apparent density in foodstuffs exposed to the drying process. The behavior of density with respect to moisture content (X) and drying temperature (T) is presented and explained with a basis in changes in structure, conformation, chemical composition, and second-order phase changes that occur in the processes of mass and heat transport, as reported to date in the literature. A review of the empirical and theoretical equations that represent density is presented, and their application in foodstuffs is discussed. This review also addresses cases with nonideal density behavior, including variations in ρ(s) and ρ(w) as a function of the inside temperature of the material, depending on drying conditions (X, T). A compilation of studies regarding the density of dehydrated foodstuffs is also presented. © 2012 Institute of Food Technologists®
Determination of critical density of charge
International Nuclear Information System (INIS)
Vila, F.
1992-11-01
In this work is given a full theoretically treatment of the problem how to determine the critical density of charge on nonconductive rectangular charged surfaces placed near a small spherical conductive and earthed surface. (author). 11 refs, 2 figs
A pedagogical look at Jeans' density scale
International Nuclear Information System (INIS)
Chu, K-H W
2007-01-01
We illustrate the derivations of Jeans' criteria for the gravitational instabilities in a static homogeneous Newtonian system for pedagogical objectives. The critical Jeans density surface is presented in terms of dimensionless sound speeds and (characteristic) length scales
Acute pulmonary parenchymal densities in the adult
International Nuclear Information System (INIS)
Murphy, C.H.; Murphy, M.R.
1987-01-01
The thrust of the radiographic interpretation is to correlate the often non-specific appearance of any parenchymal density with its time-table of development, rate of change, distribution, and the patient's clinical status. Although this chapter contains separate sections on each major cause of acute pulmonary opacification, the intent of the chapter overall is their differential diagnosis. Before beginning to deal with acute pulmonary densities, it is stressed that acute densities can only be differentiated from chronic ones by reviewing preoperative or pre-existing studies. Without the baseline comparison film or reliable presumption of prior normalcy, the acuteness of a parenchymal density may not be apparent until later examinations reveal change or resolution. Also, as discussed is baseline pathology that is altered by the portable technique can be terribly confusing when attempting to evaluate a single isolated film in an acute clinical situation
Density functional theory in quantum chemistry
Tsuneda, Takao
2014-01-01
This book examines density functional theory based on the foundation of quantum chemistry. Unconventional in approach, it reviews basic concepts, then describes the physical meanings of state-of-the-art exchange-correlation functionals and their corrections.
Relativistic density functional for nuclear structure
2016-01-01
This book aims to provide a detailed introduction to the state-of-the-art covariant density functional theory, which follows the Lorentz invariance from the very beginning and is able to describe nuclear many-body quantum systems microscopically and self-consistently. Covariant density functional theory was introduced in nuclear physics in the 1970s and has since been developed and used to describe the diversity of nuclear properties and phenomena with great success. In order to provide an advanced and updated textbook of covariant density functional theory for graduate students and nuclear physics researchers, this book summarizes the enormous amount of material that has accumulated in the field of covariant density functional theory over the last few decades as well as the latest developments in this area. Moreover, the book contains enough details for readers to follow the formalism and theoretical results, and provides exhaustive references to explore the research literature.
Magnetic fields and density functional theory
Energy Technology Data Exchange (ETDEWEB)
Salsbury Jr., Freddie [Univ. of California, Berkeley, CA (United States)
1999-02-01
A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.
Spectral density regression for bivariate extremes
Castro Camilo, Daniela; de Carvalho, Miguel
2016-01-01
can be seen as an extension of the Nadaraya–Watson estimator where the usual scalar responses are replaced by mean constrained densities on the unit interval. Numerical experiments with the methods illustrate their resilience in a variety of contexts
Geometric interpretation of density displacements and charge ...
Indian Academy of Sciences (India)
Unknown
The “geometric” interpretation of the electronic density displacements in the Hilbert space is ... an attitude is also close to the chemical thinking ..... These vectors explicitly define the corresponding ..... chain-rule for implicit functionals: p p. N p.
A Safari Through Density Functional Theory
Dreizler, Reiner M.; Lüdde, Cora S.
Density functional theory is widely used to treat quantum many body problems in many areas of physics and related fields. A brief survey of this method covering foundations, functionals and applications is presented here.
Uncertainty for Part Density Determination: An Update
Energy Technology Data Exchange (ETDEWEB)
Valdez, Mario Orlando [Los Alamos National Laboratory
2016-12-14
Accurate and precise density measurements by hydrostatic weighing requires the use of an analytical balance, configured with a suspension system, to both measure the weight of a part in water and in air. Additionally, the densities of these liquid media (water and air) must be precisely known for the part density determination. To validate the accuracy and precision of these measurements, uncertainty statements are required. The work in this report is a revision of an original report written more than a decade ago, specifically applying principles and guidelines suggested by the Guide to the Expression of Uncertainty in Measurement (GUM) for determining the part density uncertainty through sensitivity analysis. In this work, updated derivations are provided; an original example is revised with the updated derivations and appendix, provided solely to uncertainty evaluations using Monte Carlo techniques, specifically using the NIST Uncertainty Machine, as a viable alternative method.
Density of Threatened and Endangered Species
California Natural Resource Agency — A compiled density of threatened and endangered species built around 2000m wide hexagonal cells. The dataset was created by generating a blank hex grid, intersecting...
Synthesis, Crystal Structure, Density Function Theory, Molecular ...
African Journals Online (AJOL)
Tropical Journal of Pharmaceutical Research February 2016; 15 (2): 385-392 ... tested for its antimicrobial activities and computational studies including density function test (DFT) and docking ... agonists [4], selective dopamine D3 and D4 ...
Density distributions and depth in flocks
Lewis, J. M.; Turner, M. S.
2017-12-01
Recent experimental evidence suggests that interactions in flocks of birds do not involve a characteristic length scale. Bird flocks have also been revealed to have an inhomogeneous density distribution, with the density of birds near the border greater than near the centre. We introduce a strictly metric-free model for collective behaviour that incorporates a distributed motional bias, providing control of the density distribution. A simple version of this model is then able to provide a good fit to published data for the density variation across flocks of Starlings. We find that it is necessary for individuals on the edge of the flock to have an inward motional bias but that birds in the interior of the flock instead must have an outward bias. We discuss the ability of individuals to determine their depth within a flock and show how this might be achieved by relatively simple analysis of their visual environment.
Gauge-invariant cosmological density perturbations
International Nuclear Information System (INIS)
Sasaki, Misao.
1986-06-01
Gauge-invariant formulation of cosmological density perturbation theory is reviewed with special emphasis on its geometrical aspects. Then the gauge-invariant measure of the magnitude of a given perturbation is presented. (author)
High Energy Density Polymer Film Capacitors
National Research Council Canada - National Science Library
Boufelfel, Ali
2006-01-01
High-energy-density capacitors that are compact and light-weight are extremely valuable in a number of critical DoD systems that include portable field equipment, pulsed lasers, detection equipment...
Magnetic fields and density functional theory
International Nuclear Information System (INIS)
Salsbury, Freddie Jr.
1999-01-01
A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules
Nonparametric methods for volatility density estimation
Es, van Bert; Spreij, P.J.C.; Zanten, van J.H.
2009-01-01
Stochastic volatility modelling of financial processes has become increasingly popular. The proposed models usually contain a stationary volatility process. We will motivate and review several nonparametric methods for estimation of the density of the volatility process. Both models based on
Density controlled carbon nanotube array electrodes
Ren, Zhifeng F [Newton, MA; Tu, Yi [Belmont, MA
2008-12-16
CNT materials comprising aligned carbon nanotubes (CNTs) with pre-determined site densities, catalyst substrate materials for obtaining them and methods for forming aligned CNTs with controllable densities on such catalyst substrate materials are described. The fabrication of films comprising site-density controlled vertically aligned CNT arrays of the invention with variable field emission characteristics, whereby the field emission properties of the films are controlled by independently varying the length of CNTs in the aligned array within the film or by independently varying inter-tubule spacing of the CNTs within the array (site density) are disclosed. The fabrication of microelectrode arrays (MEAs) formed utilizing the carbon nanotube material of the invention is also described.
Density distortion within a rotating body
International Nuclear Information System (INIS)
Lanzano, P.
1975-01-01
This paper ascertains the distortion of the density distribution within a self-gravitating body in hydrostatic equilibrium under the influence of rotation. For this purpose, the Poisson equation has been solved by using the undistorted density profile within the Laplacian to obtain the distorted density. The Laplacian has been expressed in terms of a system of curvilinear coordinates for which the equipotential surfaces constitute a family of fundamental surfaces. In performing the requisite algebraic manipulations, the Clairaut and Radau equations developed in a previous paper (Lanzano,1974) were utilized to eliminate the derivatives of the elements pertaining to the equipotential surfaces. The density distortion has been obtained up to third-order terms in a small rotational parameter. (Auth.)
Exploring effective interactions through transition charge density ...
Indian Academy of Sciences (India)
tematics like reduced transition probabilities B(E2) and static quadrupole moments Q(2) ... approximations of solving large scale shell model problems in Monte Carlo meth- ... We present the theoretical study of transition charge densities.
Compatible growth models and stand density diagrams
International Nuclear Information System (INIS)
Smith, N.J.; Brand, D.G.
1988-01-01
This paper discusses a stand average growth model based on the self-thinning rule developed and used to generate stand density diagrams. Procedures involved in testing are described and results are included
Deuteron transverse densities in holographic QCD
Energy Technology Data Exchange (ETDEWEB)
Mondal, Chandan [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China); Indian Institute of Technology Kanpur, Department of Physics, Kanpur (India); Chakrabarti, Dipankar [Indian Institute of Technology Kanpur, Department of Physics, Kanpur (India); Zhao, Xingbo [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China)
2017-05-15
We investigate the transverse charge density in the longitudinally as well as transversely polarized deuteron using the recent empirical description of the deuteron electromagnetic form factors in the framework of holographic QCD. The predictions of the holographic QCD are compared with the results of a standard phenomenological parameterization. In addition, we evaluate GPDs and the gravitational form factors for the deuteron. The longitudinal momentum densities are also investigated in the transverse plane. (orig.)
Batteries. Higher energy density than gasoline?
International Nuclear Information System (INIS)
Fischer, Michael; Werber, Mathew; Schwartz, Peter V.
2009-01-01
The energy density of batteries is two orders of magnitude below that of liquid fuels. However, this information alone cannot be used to compare batteries to liquid fuels for automobile energy storage media. Because electric motors have a higher energy conversion efficiency and lower mass than combustion engines, they can provide a higher deliverable mechanical energy density than internal combustion for most transportation applications. (author)
High-density limit of quantum chromodynamics
International Nuclear Information System (INIS)
Alvarez, E.
1983-01-01
By means of a formal expansion of the partition function presumably valid at large baryon densities, the propagator of the quarks is expressed in terms of the gluon propagator. This result is interpreted as implying that correlations between quarks and gluons are unimportant at high enough density, so that a kind of mean-field approximation gives a very accurate description of the physical system
City density and CO_2 efficiency
International Nuclear Information System (INIS)
Gudipudi, Ramana; Fluschnik, Till; Ros, Anselmo García Cantú; Walther, Carsten; Kropp, Jürgen P.
2016-01-01
Cities play a vital role in the global climate change mitigation agenda. City population density is one of the key factors that influence urban energy consumption and the subsequent GHG emissions. However, previous research on the relationship between population density and GHG emissions led to contradictory results due to urban/rural definition conundrum and the varying methodologies for estimating GHG emissions. This work addresses these ambiguities by employing the City Clustering Algorithm (CCA) and utilizing the gridded CO_2 emissions data. Our results, derived from the analysis of all inhabited areas in the US, show a sub-linear relationship between population density and the total emissions (i.e. the sum of on-road and building emissions) on a per capita basis. Accordingly, we find that doubling the population density would entail a reduction in the total CO_2 emissions in buildings and on-road sectors typically by at least 42%. Moreover, we find that population density exerts a higher influence on on-road emissions than buildings emissions. From an energy consumption point of view, our results suggest that on-going urban sprawl will lead to an increase in on-road energy consumption in cities and therefore stresses the importance of developing adequate local policy measures to limit urban sprawl. - Highlights: •We use gridded population, land use and CO_2 emissions data. •We attribute building and on-road sectoral emissions to populated settlements. •We apply CCA to identify unique city extents and population densities. •Doubling the population density increases CO_2 efficiency typically by 42%. •Population density has more influence on-road CO_2 efficiency than buildings sector.
Dislocation density changes in nickel under creep
International Nuclear Information System (INIS)
Moiseeva, I.V.; Okrainets, P.N.; Pishchak, V.K.
1984-01-01
Variation in dislocation density was studied in the process of nickel creep p at t=900 deg c and σ=2 kgf/mm 2 . The dislocation structure was studied independently by the X-ray technique and transmission electron-microscopy. The e two methods show good conformity of results by comparison. It is concluded that independent determination of dislocation density under creep is possible us sing the X-ray technique
Condensation energy density in Bi-2212 superconductors
International Nuclear Information System (INIS)
Matsushita, Teruo; Kiuchi, Masaru; Haraguchi, Teruhisa; Imada, Takeki; Okamura, Kazunori; Okayasu, Satoru; Uchida, Satoshi; Shimoyama, Jun-ichi; Kishio, Kohji
2006-01-01
The relationship between the condensation energy density and the anisotropy parameter, γ a , has been derived for Bi-2212 superconductors in various anisotropic states by analysing the critical current density due to columnar defects introduced by heavy ion irradiation. The critical current density depended on the size of the defects, determined by the kind and irradiation energy of the ions. A significantly large critical current density of 17.0 MA cm -2 was obtained at 5 K and 0.1 T even for the defect density of a matching field of 1 T in a specimen irradiated with iodine ions. The dependence of the critical current density on the size of the defects agreed well with the prediction from the summation theory of pinning forces, and the condensation energy density could be obtained consistently from specimens irradiated with different ions. The condensation energy density obtained increased with decreasing γ a over the entire range of measurement temperature, and reached about 60% of the value for the most three-dimensional Y-123 observed by Civale et al at 5 K. This gives the reason for the very strong pinning in Bi-2212 superconductors at low temperatures. The thermodynamic critical field obtained decreased linearly with increasing temperature and extrapolated to zero at a certain characteristic temperature, T * , lower than the critical temperature, T c . T * , which seems to be associated with the superconductivity in the block layers, was highest for the optimally doped specimen. This shows that the superconductivity becomes more inhomogeneous as the doped state of a superconductor deviates from the optimum condition
Calculation of the density of liquid radon
International Nuclear Information System (INIS)
Herreman, W.
1980-01-01
Eleven condensed gases were investigated to relate their critical molar volume Vsub(c) to their molar volume Vsub(o)(Vsub(o) is the molar volume where the fluidity phi = 0). From this relationship the critical density of radon was calculated psub(c) = 1613 kg m -3 . From this principle of corresponding states for viscosity and with this value for psub(c) the density for the saturated liquid state of radon was predicted. (author)
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The density of liquid Ni-Cr alloy was measured by a modified sessile drop method. The density of liquid Ni-Cr alloywas found to decrease with increasing temperature and Cr concentration in the alloy. The molar volume of liquidNi-Cr alloy increases with increasing the Cr concentration in the alloy. The molar volume of Ni-Cr alloy determinedin the present work shows a positive deviation from the linear molar volume.
On density of the Vassiliev invariants
DEFF Research Database (Denmark)
Røgen, Peter
1999-01-01
The main result is that the Vassiliev invariants are dense in the set of numeric knot invariants if and only if they separate knots.Keywords: Knots, Vassiliev invariants, separation, density, torus knots......The main result is that the Vassiliev invariants are dense in the set of numeric knot invariants if and only if they separate knots.Keywords: Knots, Vassiliev invariants, separation, density, torus knots...
Density conditions for triangles in multipartite graphs
DEFF Research Database (Denmark)
Bondy, Adrian; Shen, Jin; Thomassé, Stephan
2006-01-01
subgraphs in G. We investigate in particular the case where G is a complete multipartite graph. We prove that a finite tripartite graph with all edge densities greater than the golden ratio has a triangle and that this bound is best possible. Also we show that an infinite-partite graph with finite parts has...... a triangle, provided that the edge density between any two parts is greater than 1/2....
Weight loss and bone mineral density.
Hunter, Gary R; Plaisance, Eric P; Fisher, Gordon
2014-10-01
Despite evidence that energy deficit produces multiple physiological and metabolic benefits, clinicians are often reluctant to prescribe weight loss in older individuals or those with low bone mineral density (BMD), fearing BMD will be decreased. Confusion exists concerning the effects that weight loss has on bone health. Bone density is more closely associated with lean mass than total body mass and fat mass. Although rapid or large weight loss is often associated with loss of bone density, slower or smaller weight loss is much less apt to adversely affect BMD, especially when it is accompanied with high intensity resistance and/or impact loading training. Maintenance of calcium and vitamin D intake seems to positively affect BMD during weight loss. Although dual energy X-ray absorptiometry is normally used to evaluate bone density, it may overestimate BMD loss following massive weight loss. Volumetric quantitative computed tomography may be more accurate for tracking bone density changes following large weight loss. Moderate weight loss does not necessarily compromise bone health, especially when exercise training is involved. Training strategies that include heavy resistance training and high impact loading that occur with jump training may be especially productive in maintaining, or even increasing bone density with weight loss.
From the trajectory to the density memory
International Nuclear Information System (INIS)
Cakir, Rasit; Krokhin, Arkadii; Grigolini, Paolo
2007-01-01
In this paper we discuss the connection between trajectory and density memory. The first form of memory is a property of a stochastic trajectory, whose stationary correlation function shows that the fluctuation at a given time depends on the earlier fluctuations. The density memory is a property of a collection of trajectories, whose density time evolution is described by a time convoluted equation showing that the density time evolution depends on its past history. We show that the trajectory memory does not necessarily yields density memory, and that density memory might be compatible with the existence of abrupt jumps resetting to zero the system's memory. We focus our attention on a time-convoluted diffusion equation, when the memory kernel is an inverse power law with (i) negative and (ii) positive tail. In case (i) there exist both renewal trajectories and trajectories with memory, compatible with this equation. Case (ii), which has eluded so far a convincing interpretation in terms of trajectories, is shown to be compatible only with trajectory memory
Path-integral computation of superfluid densities
International Nuclear Information System (INIS)
Pollock, E.L.; Ceperley, D.M.
1987-01-01
The normal and superfluid densities are defined by the response of a liquid to sample boundary motion. The free-energy change due to uniform boundary motion can be calculated by path-integral methods from the distribution of the winding number of the paths around a periodic cell. This provides a conceptually and computationally simple way of calculating the superfluid density for any Bose system. The linear-response formulation relates the superfluid density to the momentum-density correlation function, which has a short-ranged part related to the normal density and, in the case of a superfluid, a long-ranged part whose strength is proportional to the superfluid density. These facts are discussed in the context of path-integral computations and demonstrated for liquid 4 He along the saturated vapor-pressure curve. Below the experimental superfluid transition temperature the computed superfluid fractions agree with the experimental values to within the statistical uncertainties of a few percent in the computations. The computed transition is broadened by finite-sample-size effects
Density and surface tension of ionic liquids.
Kolbeck, C; Lehmann, J; Lovelock, K R J; Cremer, T; Paape, N; Wasserscheid, P; Fröba, A P; Maier, F; Steinrück, H-P
2010-12-30
We measured the density and surface tension of 9 bis[(trifluoromethyl)sulfonyl]imide ([Tf(2)N](-))-based and 12 1-methyl-3-octylimidazolium ([C(8)C(1)Im](+))-based ionic liquids (ILs) with the vibrating tube and the pendant drop method, respectively. This comprehensive set of ILs was chosen to probe the influence of the cations and anions on density and surface tension. When the alkyl chain length in the [C(n)C(1)Im][Tf(2)N] series (n = 1, 2, 4, 6, 8, 10, 12) is increased, a decrease in density is observed. The surface tension initially also decreases but reaches a plateau for alkyl chain lengths greater than n = 8. Functionalizing the alkyl chains with ethylene glycol groups results in a higher density as well as a higher surface tension. For the dependence of density and surface tension on the chemical nature of the anion, relations are only found for subgroups of the studied ILs. Density and surface tension values are discussed with respect to intermolecular interactions and surface composition as determined by angle-resolved X-ray photoelectron spectroscopy (ARXPS). The absence of nonvolatile surface-active contaminants was proven by ARXPS.
Negative density-distribution relationship in butterflies.
Päivinen, Jussi; Grapputo, Alessandro; Kaitala, Veijo; Komonen, Atte; Kotiaho, Janne S; Saarinen, Kimmo; Wahlberg, Niklas
2005-03-01
Because "laws of nature" do not exist in ecology, much of the foundations of community ecology rely on broad statistical generalisations. One of the strongest generalisations is the positive relationship between density and distribution within a given taxonomic assemblage; that is, locally abundant species are more widespread than locally sparse species. Several mechanisms have been proposed to create this positive relationship, and the testing of these mechanisms is attracting increasing attention. We report a strong, but counterintuitive, negative relationship between density and distribution in the butterfly fauna of Finland. With an exceptionally comprehensive data set (data includes all 95 resident species in Finland and over 1.5 million individuals), we have been able to submit several of the mechanisms to powerful direct empirical testing. Without exception, we failed to find evidence for the proposed mechanisms creating a positive density-distribution relationship. On the contrary, we found that many of the mechanisms are equally able to generate a negative relationship. We suggest that one important determinant of density-distribution relationships is the geographical location of the study: on the edge of a distribution range, suitable habitat patches are likely to be more isolated than in the core of the range. In such a situation, only the largest and best quality patches are likely to be occupied, and these by definition can support a relatively dense population leading to a negative density-distribution relationship. Finally, we conclude that generalizations about the positive density-distribution relationship should be made more cautiously.
Quantitative assessment of breast density from mammograms
International Nuclear Information System (INIS)
Jamal, N.; Ng, K.H.
2004-01-01
Full text: It is known that breast density is increasingly used as a risk factor for breast cancer. This study was undertaken to develop and validate a semi-automated computer technique for the quantitative assessment of breast density from digitised mammograms. A computer technique had been developed using MATLAB (Version 6.1) based GUI applications. This semi-automated image analysis tool consists of gradient correction, segmentation of breast region from background, segmentation of fibroglandular and adipose region within the breast area and calculation of breast density. The density is defined as the percentage of fibroglandular tissue area divided by the total breast area in the mammogram. This technique was clinically validated with 122 normal mammograms; these were subjectively evaluated and classified according to the five parenchyma patterns of the Tabar's scheme (Class I- V) by a consultant radiologist. There was a statistical significant correlation between the computer technique and subjective classification (r 2 = 0.84, p<0.05). 71.3% of subjective classification was correctly classified using the computer technique. We had developed a computer technique for the quantitative assessment of breast density and validated its accuracy for computerized classification based on Tabar's scheme. This quantitative tool is useful for the evaluation of a large dataset of mammograms to predict breast cancer risk based on density. Furthermore it has the potential to provide an early marker for success or failure in chemoprevention studies such as hormonal replacement therapy. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine
Tao, Jianmin; Ye, Lin-Hui; Duan, Yuhua
2017-12-01
The primary goal of Kohn-Sham density functional theory is to evaluate the exchange-correlation contribution to electronic properties. However, the accuracy of a density functional can be affected by the electron density. Here we apply the nonempirical Tao-Mo (TM) semilocal functional to study the influence of the electron density on the exchange and correlation energies of atoms and ions, and compare the results with the commonly used nonempirical semilocal functionals local spin-density approximation (LSDA), Perdew-Burke-Ernzerhof (PBE), Tao-Perdew-Staroverov-Scuseria (TPSS), and hybrid functional PBE0. We find that the spin-restricted Hartree-Fock density yields the exchange and correlation energies in good agreement with the Optimized Effective Potential method, particularly for spherical atoms and ions. However, the errors of these semilocal and hybrid functionals become larger for self-consistent densities. We further find that the quality of the electron density have greater effect on the exchange-correlation energies of kinetic energy density-dependent meta-GGA functionals TPSS and TM than on those of the LSDA and GGA, and therefore, should have greater influence on the performance of meta-GGA functionals. Finally, we show that the influence of the density quality on PBE0 is slightly reduced, compared to that of PBE, due to the exact mixing.
Dietary modification of human macular pigment density.
Hammond, B R; Johnson, E J; Russell, R M; Krinsky, N I; Yeum, K J; Edwards, R B; Snodderly, D M
1997-08-01
The retinal carotenoids lutein (L) and zeaxanthin (Z) that form the macular pigment (MP) may help to prevent neovascular age-related macular degeneration. The purpose of this study was to determine whether MP density in the retina could be raised by increasing dietary intake of L and Z from foods. Macular pigment was measured psychophysically for 13 subjects. Serum concentrations of L, Z, and beta-carotene were measured by high-performance liquid chromatography. Eleven subjects modified their usual daily diets by adding 60 g of spinach (10.8 mg L, 0.3 mg Z, 5 mg beta-carotene) and ten also added 150 g of corn (0.3 mg Z, 0.4 mg L); two other subjects were given only corn. Dietary modification lasted up to 15 weeks. For the subjects fed spinach or spinach and corn, three types of responses to dietary modification were identified: Eight "retinal responders" had increases in serum L (mean, 33%; SD, 22%) and in MP density (mean, 19%; SD, 11%); two "retinal nonresponders" showed substantial increases in serum L (mean, 31%) but not in MP density (mean, -11%); one "serum and retinal nonresponder" showed no changes in serum L, Z, or beta-carotene and no change in MP density. For the two subjects given only corn, serum L changed little (+11%, -6%), but in one subject serum Z increased (70%) and MP density increased (25%). Increases in MP density were obtained within 4 weeks of dietary modification for most, but not all, subjects. When MP density increased with dietary modification, it remained elevated for at least several months after resuming an unmodified diet. Augmentation of MP for both experimental and clinical investigation appears to be feasible for many persons.
Thermospheric density and satellite drag modeling
Mehta, Piyush Mukesh
The United States depends heavily on its space infrastructure for a vast number of commercial and military applications. Space Situational Awareness (SSA) and Threat Assessment require maintaining accurate knowledge of the orbits of resident space objects (RSOs) and the associated uncertainties. Atmospheric drag is the largest source of uncertainty for low-perigee RSOs. The uncertainty stems from inaccurate modeling of neutral atmospheric mass density and inaccurate modeling of the interaction between the atmosphere and the RSO. In order to reduce the uncertainty in drag modeling, both atmospheric density and drag coefficient (CD) models need to be improved. Early atmospheric density models were developed from orbital drag data or observations of a few early compact satellites. To simplify calculations, densities derived from orbit data used a fixed CD value of 2.2 measured in a laboratory using clean surfaces. Measurements from pressure gauges obtained in the early 1990s have confirmed the adsorption of atomic oxygen on satellite surfaces. The varying levels of adsorbed oxygen along with the constantly changing atmospheric conditions cause large variations in CD with altitude and along the orbit of the satellite. Therefore, the use of a fixed CD in early development has resulted in large biases in atmospheric density models. A technique for generating corrections to empirical density models using precision orbit ephemerides (POE) as measurements in an optimal orbit determination process was recently developed. The process generates simultaneous corrections to the atmospheric density and ballistic coefficient (BC) by modeling the corrections as statistical exponentially decaying Gauss-Markov processes. The technique has been successfully implemented in generating density corrections using the CHAMP and GRACE satellites. This work examines the effectiveness, specifically the transfer of density models errors into BC estimates, of the technique using the CHAMP and
International Nuclear Information System (INIS)
Wolnik, Barbara; Dembowski, Marcin; Bołt, Witold; Baetens, Jan M; De Baets, Bernard
2017-01-01
The focus of this paper is on the density classification problem in the context of affine continuous cellular automata. Although such cellular automata cannot solve this problem in the classical sense, most density-conserving affine continuous cellular automata with a unit neighborhood radius are valid solutions of a slightly relaxed version of this problem. This result follows from a detailed study of the dynamics of the density-conserving affine continuous cellular automata that we introduce. (paper)
ON THE ORIGIN OF THE HIGH COLUMN DENSITY TURNOVER IN THE H I COLUMN DENSITY DISTRIBUTION
International Nuclear Information System (INIS)
Erkal, Denis; Gnedin, Nickolay Y.; Kravtsov, Andrey V.
2012-01-01
We study the high column density regime of the H I column density distribution function and argue that there are two distinct features: a turnover at N H I ≈ 10 21 cm –2 , which is present at both z = 0 and z ≈ 3, and a lack of systems above N H I ≈ 10 22 cm –2 at z = 0. Using observations of the column density distribution, we argue that the H I-H 2 transition does not cause the turnover at N H I ≈ 10 21 cm –2 but can plausibly explain the turnover at N H I ∼> 10 22 cm –2 . We compute the H I column density distribution of individual galaxies in the THINGS sample and show that the turnover column density depends only weakly on metallicity. Furthermore, we show that the column density distribution of galaxies, corrected for inclination, is insensitive to the resolution of the H I map or to averaging in radial shells. Our results indicate that the similarity of H I column density distributions at z = 3 and 0 is due to the similarity of the maximum H I surface densities of high-z and low-z disks, set presumably by universal processes that shape properties of the gaseous disks of galaxies. Using fully cosmological simulations, we explore other candidate physical mechanisms that could produce a turnover in the column density distribution. We show that while turbulence within giant molecular clouds cannot affect the damped Lyα column density distribution, stellar feedback can affect it significantly if the feedback is sufficiently effective in removing gas from the central 2-3 kpc of high-redshift galaxies. Finally, we argue that it is meaningful to compare column densities averaged over ∼ kpc scales with those estimated from quasar spectra that probe sub-pc scales due to the steep power spectrum of H I column density fluctuations observed in nearby galaxies.
Number density structures in the inner heliosphere
Stansby, D.; Horbury, T. S.
2018-06-01
Aims: The origins and generation mechanisms of the slow solar wind are still unclear. Part of the slow solar wind is populated by number density structures, discrete patches of increased number density that are frozen in to and move with the bulk solar wind. In this paper we aimed to provide the first in-situ statistical study of number density structures in the inner heliosphere. Methods: We reprocessed in-situ ion distribution functions measured by Helios in the inner heliosphere to provide a new reliable set of proton plasma moments for the entire mission. From this new data set we looked for number density structures measured within 0.5 AU of the Sun and studied their properties. Results: We identified 140 discrete areas of enhanced number density. The structures occurred exclusively in the slow solar wind and spanned a wide range of length scales from 50 Mm to 2000 Mm, which includes smaller scales than have been previously observed. They were also consistently denser and hotter that the surrounding plasma, but had lower magnetic field strengths, and therefore remained in pressure balance. Conclusions: Our observations show that these structures are present in the slow solar wind at a wide range of scales, some of which are too small to be detected by remote sensing instruments. These structures are rare, accounting for only 1% of the slow solar wind measured by Helios, and are not a significant contribution to the mass flux of the solar wind.
High throughput nonparametric probability density estimation.
Farmer, Jenny; Jacobs, Donald
2018-01-01
In high throughput applications, such as those found in bioinformatics and finance, it is important to determine accurate probability distribution functions despite only minimal information about data characteristics, and without using human subjectivity. Such an automated process for univariate data is implemented to achieve this goal by merging the maximum entropy method with single order statistics and maximum likelihood. The only required properties of the random variables are that they are continuous and that they are, or can be approximated as, independent and identically distributed. A quasi-log-likelihood function based on single order statistics for sampled uniform random data is used to empirically construct a sample size invariant universal scoring function. Then a probability density estimate is determined by iteratively improving trial cumulative distribution functions, where better estimates are quantified by the scoring function that identifies atypical fluctuations. This criterion resists under and over fitting data as an alternative to employing the Bayesian or Akaike information criterion. Multiple estimates for the probability density reflect uncertainties due to statistical fluctuations in random samples. Scaled quantile residual plots are also introduced as an effective diagnostic to visualize the quality of the estimated probability densities. Benchmark tests show that estimates for the probability density function (PDF) converge to the true PDF as sample size increases on particularly difficult test probability densities that include cases with discontinuities, multi-resolution scales, heavy tails, and singularities. These results indicate the method has general applicability for high throughput statistical inference.
Density-functional expansion methods: Grand challenges.
Giese, Timothy J; York, Darrin M
2012-03-01
We discuss the source of errors in semiempirical density functional expansion (VE) methods. In particular, we show that VE methods are capable of well-reproducing their standard Kohn-Sham density functional method counterparts, but suffer from large errors upon using one or more of these approximations: the limited size of the atomic orbital basis, the Slater monopole auxiliary basis description of the response density, and the one- and two-body treatment of the core-Hamiltonian matrix elements. In the process of discussing these approximations and highlighting their symptoms, we introduce a new model that supplements the second-order density-functional tight-binding model with a self-consistent charge-dependent chemical potential equalization correction; we review our recently reported method for generalizing the auxiliary basis description of the atomic orbital response density; and we decompose the first-order potential into a summation of additive atomic components and many-body corrections, and from this examination, we provide new insights and preliminary results that motivate and inspire new approximate treatments of the core-Hamiltonian.
On radiative density limits in stellarators
International Nuclear Information System (INIS)
Wobig, H.
2001-01-01
Density limits in stellarators are caused mainly by enhanced impurity radiation leading to a collapse of the temperature. A simple model can be established, which computes the temperature in the plasma with a fixed heating profile and a temperature-dependent radiation profile. If the temperature-dependent radiation function has one or several extrema, multiple solutions of the transport equation exist and radiative collapse occurs when the high temperature branch merges with the unstable temperature branch. At this bifurcation point the temperature decreases to a stable low temperature solution. The bifurcation point is a function of the heating power and the plasma density. Thus a density limit can be defined as the point where bifurcation occurs. It is shown that bifurcation and sudden temperature collapse does not occur below a power threshold. Anomalous thermal conductivity and the details of the impurity radiation, which in the present model is assumed to be in corona equilibrium, determine the scaling of the density limit. A model of the anomalous transport is developed, which leads to Gyro-Bohm scaling of the confinement time. The density limit based on this transport model is close to experimental findings in Wendelstein 7-AS. (author)
Transition density of charge-exchange processes
International Nuclear Information System (INIS)
Lovas, R.G.
1983-01-01
The transition density between parent and analogue states is studied with special reference to its role in charge-exchange nuclear reactions. The structure of the target nucleus is described in a perturbative approach, in which the Coulomb and asymmetry potentials mix the eigenstates of a charge-independent single-particle Hamiltonian. In this model formulae are derived for the transition density, the Coulomb displacement energy and the neutron-proton density difference, and their relationship is used to estimate the transition density. This estimate shows that: the largest contribution comes from the density of the excess neutrons; the weight of the Coulomb-mixing effect is small up to excess neutron number 10, and grows rapidly beyond; the weight of the core polarization term induced by the excess neutrons is modest and is the same for all nuclei. It is indicated that the Coulomb effect may explain the departure from the Lane model of nucleon charge-exchange scattering found for heavy nuclei, whereas the core polarization may account for the observed anomalous dependence of the deg 0 pion charge-exchange cross section on the number of excess neutrons. (author)
Hong Shen
2011-01-01
The concepts of curve profile, curve intercept, curve intercept density, curve profile area density, intersection density in containing intersection (or intersection density relied on intersection reference), curve profile intersection density in surface (or curve intercept intersection density relied on intersection of containing curve), and curve profile area density in surface (AS) were defined. AS expressed the amount of curve profile area of Y phase in the unit containing surface area, S...
Procedure of non-contacting local mass density and mass density distribution measurements
International Nuclear Information System (INIS)
Menzel, M.; Winkler, K.
1985-01-01
The invention has been aimed at a procedure of non-contacting local mass density and/or mass density distribution measurements i.e. without the interfering influence of sensors or probes. It can be applied to installations, apparatuses and pipings of chemical engineering, to tank constructions and transportation on extreme temperature and/or pressure conditions and aggressive media influences respectively. The procedure has utilized an ionizing quantum radiation whereby its unknown weakening and scattering is compensated by a suitable combination of scattering and transmission counter rate measurements in such a way that the local mass densities and the mass density distribution respectively are determinable
Exploring high-density baryonic matter: Maximum freeze-out density
Energy Technology Data Exchange (ETDEWEB)
Randrup, Joergen [Lawrence Berkeley National Laboratory, Nuclear Science Division, Berkeley, CA (United States); Cleymans, Jean [University of Cape Town, UCT-CERN Research Centre and Department of Physics, Rondebosch (South Africa)
2016-08-15
The hadronic freeze-out line is calculated in terms of the net baryon density and the energy density instead of the usual T and μ{sub B}. This analysis makes it apparent that the freeze-out density exhibits a maximum as the collision energy is varied. This maximum freeze-out density has μ{sub B} = 400 - 500 MeV, which is above the critical value, and it is reached for a fixed-target bombarding energy of 20-30 GeV/N well within the parameters of the proposed NICA collider facility. (orig.)
Electron density and gas density measurements in a millimeter-wave discharge
Energy Technology Data Exchange (ETDEWEB)
Schaub, S. C., E-mail: sschaub@mit.edu; Hummelt, J. S.; Guss, W. C.; Shapiro, M. A.; Temkin, R. J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology 167 Albany St., Bldg. NW16, Cambridge, Massachusetts 02139 (United States)
2016-08-15
Electron density and neutral gas density have been measured in a non-equilibrium air breakdown plasma using optical emission spectroscopy and two-dimensional laser interferometry, respectively. A plasma was created with a focused high frequency microwave beam in air. Experiments were run with 110 GHz and 124.5 GHz microwaves at powers up to 1.2 MW. Microwave pulses were 3 μs long at 110 GHz and 2.2 μs long at 124.5 GHz. Electron density was measured over a pressure range of 25 to 700 Torr as the input microwave power was varied. Electron density was found to be close to the critical density, where the collisional plasma frequency is equal to the microwave frequency, over the pressure range studied and to vary weakly with input power. Neutral gas density was measured over a pressure range from 150 to 750 Torr at power levels high above the threshold for initiating breakdown. The two-dimensional structure of the neutral gas density was resolved. Intense, localized heating was found to occur hundreds of nanoseconds after visible plasma formed. This heating led to neutral gas density reductions of greater than 80% where peak plasma densities occurred. Spatial structure and temporal dynamics of gas heating at atmospheric pressure were found to agree well with published numerical simulations.
Electron density and gas density measurements in a millimeter-wave discharge
International Nuclear Information System (INIS)
Schaub, S. C.; Hummelt, J. S.; Guss, W. C.; Shapiro, M. A.; Temkin, R. J.
2016-01-01
Electron density and neutral gas density have been measured in a non-equilibrium air breakdown plasma using optical emission spectroscopy and two-dimensional laser interferometry, respectively. A plasma was created with a focused high frequency microwave beam in air. Experiments were run with 110 GHz and 124.5 GHz microwaves at powers up to 1.2 MW. Microwave pulses were 3 μs long at 110 GHz and 2.2 μs long at 124.5 GHz. Electron density was measured over a pressure range of 25 to 700 Torr as the input microwave power was varied. Electron density was found to be close to the critical density, where the collisional plasma frequency is equal to the microwave frequency, over the pressure range studied and to vary weakly with input power. Neutral gas density was measured over a pressure range from 150 to 750 Torr at power levels high above the threshold for initiating breakdown. The two-dimensional structure of the neutral gas density was resolved. Intense, localized heating was found to occur hundreds of nanoseconds after visible plasma formed. This heating led to neutral gas density reductions of greater than 80% where peak plasma densities occurred. Spatial structure and temporal dynamics of gas heating at atmospheric pressure were found to agree well with published numerical simulations.
The virialization density of peaks with general density profiles under spherical collapse
Rubin, Douglas; Loeb, Abraham
2013-01-01
We calculate the non-linear virialization density, $\\Delta_c$, of halos under spherical collapse from peaks with an arbitrary initial and final density profile. This is in contrast to the standard calculation of $\\Delta_c$ which assumes top-hat profiles. Given our formalism, the non-linear halo density can be calculated once the shape of the initial peak's density profile and the shape of the virialized halo's profile are provided. We solve for $\\Delta_c$ for halos in an Einstein de-Sitter an...
Bone density in patients with chondromalacia patella.
Salehi, Iraj; Khazaeli, Shabnam; Hatami, Parta; Malekpour, Mahdi
2010-06-01
Chondromalacia of the patella is the most common cause of anterior knee pain in young women. The etiology of the disease is not well-understood but the initial lesion is a disorganization of collagenous structures. Since the disease is proposed to be due to generalized constitutional disturbance, we postulated that bony structures could also be involved. To investigate this hypothesis we measured the bone density of 286 patients with the diagnosis of chondromalacia of the patella during a 4-year period using dual energy X-ray absorptiometry (DXA) method. We found a significant number of patients having low bone densities. This problem was more pronounced in men and in younger age groups. We suggest base-line bone density evaluation in all patients, treatment of osteopenia or osteoporosis in select patients and regular follow-ups using DXA.
Acoustic levitation methods for density measurements
Trinh, E. H.; Hsu, C. J.
1986-01-01
The capability of ultrasonic levitators operating in air to perform density measurements has been demonstrated. The remote determination of the density of ordinary liquids as well as low density solid metals can be carried out using levitated samples with size on the order of a few millimeters and at a frequency of 20 kHz. Two basic methods may be used. The first one is derived from a previously known technique developed for acoustic levitation in liquid media, and is based on the static equilibrium position of levitated samples in the earth's gravitational field. The second approach relies on the dynamic interaction between a levitated sample and the acoustic field. The first technique appears more accurate (1 percent uncertainty), but the latter method is directly applicable to a near gravity-free environment such as that found in space.
High Density Digital Data Storage System
Wright, Kenneth D., II; Gray, David L.; Rowland, Wayne D.
1991-01-01
The High Density Digital Data Storage System was designed to provide a cost effective means for storing real-time data from the field-deployable digital acoustic measurement system. However, the high density data storage system is a standalone system that could provide a storage solution for many other real time data acquisition applications. The storage system has inputs for up to 20 channels of 16-bit digital data. The high density tape recorders presently being used in the storage system are capable of storing over 5 gigabytes of data at overall transfer rates of 500 kilobytes per second. However, through the use of data compression techniques the system storage capacity and transfer rate can be doubled. Two tape recorders have been incorporated into the storage system to produce a backup tape of data in real-time. An analog output is provided for each data channel as a means of monitoring the data as it is being recorded.
Systematics of the level density parameters
International Nuclear Information System (INIS)
Ignatyuk, A.V.; Istekov, K.K.; Smirenkin, G.N.
1977-01-01
The excitation energy dependence of nucleus energy-level density is phenomenologically systematized in terms of the Fermi gas model. The analysis has been conducted in the atomic mass number range of A(>=)150, where the collective effects are mostly pronounced. The density parameter a(U) is obtained using data on neutron resonances. To depict energy spectra of nuclear states in the Fermi gas model (1) the contributions from collective rotational and vibrational modes (2), as well as from pair correlations (3) are also taken into account. It is shown, that at excitation energies close to the neutron binding energy all three systematics of a(U) yield practically the same energy-level densities. At high energies only the (2) and (3) systematics are valid, and at energies lower than the neutron binding energy only the last systematics will be adequate
Measurement of the lunar neutron density profile
International Nuclear Information System (INIS)
Woolum, D.S.; Burnett, D.S.; Furst, M.; Weiss, J.R.
1975-01-01
An in situ measurement of the lunar neutron density from 20 to 400 g cm -2 depth below the lunar surface was made by the Apollo 17 Lunar Neutron Probe Experiment (LNPE) using particle tracks produced by the 10 B (n,α) 7 Li reaction. Both the absolute magnitude and the depth profile of the neutron density are in good agreement with theoretical calculations by Lingenfelter, Canfield, and Hampel. However, relatively small deviations between experiment and theory in the effect of Cd absorption on the neutron density and in the relative 149 Sm to 157 Gd capture rates reported previously (Russ et al., 1972) imply that the true lunar 157 Gd capture rate is about one half of that calculated theoretically. (Auth.)
Hazy increased density in diffuse lung disease
International Nuclear Information System (INIS)
Klein, J.S.; Webb, W.R.; Gamsu, G.; Warnock, M.; Park, C.K.
1989-01-01
In order to determine the significance of ground glass density on high-resolution CT scans of patients with idiopathic pulmonary fibrosis and other lung disorders, the authors have reviewed 200 high-resolution CT studies and found 50 cases demonstrating areas of hazy increased lung density. Disease entities most often associated with this finding included DIP, UIP, alveolar proteinosis, sarcoidosis, and bronchiolitis obliterans/ organizing pneumonia. Pathologic examination revealed either cellular or fluid material lining terminal air spaces, often associated with alveolar wall infiltration and an absence of fibrosis. Gallium scans and bronchoalveolar lavage in some cases showed active inflammation Follow-up high-resolution CT studies in 10 patients showed either change or resolution of the hazy densities, confirming the presence of a reversible parenchymal lesion
DCMDN: Deep Convolutional Mixture Density Network
D'Isanto, Antonio; Polsterer, Kai Lars
2017-09-01
Deep Convolutional Mixture Density Network (DCMDN) estimates probabilistic photometric redshift directly from multi-band imaging data by combining a version of a deep convolutional network with a mixture density network. The estimates are expressed as Gaussian mixture models representing the probability density functions (PDFs) in the redshift space. In addition to the traditional scores, the continuous ranked probability score (CRPS) and the probability integral transform (PIT) are applied as performance criteria. DCMDN is able to predict redshift PDFs independently from the type of source, e.g. galaxies, quasars or stars and renders pre-classification of objects and feature extraction unnecessary; the method is extremely general and allows the solving of any kind of probabilistic regression problems based on imaging data, such as estimating metallicity or star formation rate in galaxies.
Rational Density Functional Selection Using Game Theory.
McAnanama-Brereton, Suzanne; Waller, Mark P
2018-01-22
Theoretical chemistry has a paradox of choice due to the availability of a myriad of density functionals and basis sets. Traditionally, a particular density functional is chosen on the basis of the level of user expertise (i.e., subjective experiences). Herein we circumvent the user-centric selection procedure by describing a novel approach for objectively selecting a particular functional for a given application. We achieve this by employing game theory to identify optimal functional/basis set combinations. A three-player (accuracy, complexity, and similarity) game is devised, through which Nash equilibrium solutions can be obtained. This approach has the advantage that results can be systematically improved by enlarging the underlying knowledge base, and the deterministic selection procedure mathematically justifies the density functional and basis set selections.
Solidity of viscous liquids. IV. Density fluctuations
DEFF Research Database (Denmark)
Dyre, J. C.
2006-01-01
This paper is the fourth in a series exploring the physical consequences of the solidity of highly viscous liquids. It is argued that the two basic characteristics of a flow event (a jump between two energy minima in configuration space) are the local density change and the sum of all particle...... displacements. Based on this it is proposed that density fluctuations are described by a time-dependent Ginzburg-Landau equation with rates in k space of the form C+Dk^2 with D>>C a^2 where a is the average intermolecular distance. The inequality expresses a long-wavelength dominance of the dynamics which...... with Debye behavior at low frequencies and an omega^{−1/2} decay of the loss at high frequencies. Finally, a general formalism for the description of viscous liquid dynamics, which supplements the density dynamics by including stress fields, a potential energy field, and molecular orientational fields...
Baryon density in alternative BBN models
International Nuclear Information System (INIS)
Kirilova, D.
2002-10-01
We present recent determinations of the cosmological baryon density ρ b , extracted from different kinds of observational data. The baryon density range is not very wide and is usually interpreted as an indication for consistency. It is interesting to note that all other determinations give higher baryon density than the standard big bang nucleosynthesis (BBN) model. The differences of the ρ b values from the BBN predicted one (the most precise today) may be due to the statistical and systematic errors in observations. However, they may be an indication of new physics. Hence, it is interesting to study alternative BBN models, and the possibility to resolve the discrepancies. We discuss alternative cosmological scenarios: a BBN model with decaying particles (m ∼ MeV, τ ∼ sec) and BBN with electron-sterile neutrino oscillations, which permit to relax BBN constraints on the baryon content of the Universe. (author)
Density-Based 3D Shape Descriptors
Directory of Open Access Journals (Sweden)
Schmitt Francis
2007-01-01
Full Text Available We propose a novel probabilistic framework for the extraction of density-based 3D shape descriptors using kernel density estimation. Our descriptors are derived from the probability density functions (pdf of local surface features characterizing the 3D object geometry. Assuming that the shape of the 3D object is represented as a mesh consisting of triangles with arbitrary size and shape, we provide efficient means to approximate the moments of geometric features on a triangle basis. Our framework produces a number of 3D shape descriptors that prove to be quite discriminative in retrieval applications. We test our descriptors and compare them with several other histogram-based methods on two 3D model databases, Princeton Shape Benchmark and Sculpteur, which are fundamentally different in semantic content and mesh quality. Experimental results show that our methodology not only improves the performance of existing descriptors, but also provides a rigorous framework to advance and to test new ones.
Planck intermediate results - LII. Planet flux densities
DEFF Research Database (Denmark)
Akrami, Y.; Ashdown, M.; Aumont, J.
2017-01-01
Measurements of flux density are described for five planets, Mars, Jupiter, Saturn, Uranus, and Neptune, across the six Planck High Frequency Instrument frequency bands (100–857 GHz) and these are then compared with models and existing data. In our analysis, we have also included estimates...... of the brightness of Jupiter and Saturn at the three frequencies of the Planck Low Frequency Instrument (30, 44, and 70 GHz). The results provide constraints on the intrinsic brightness and the brightness time-variability of these planets. The majority of the planet flux density estimates are limited by systematic...... errors, but still yield better than 1% measurements in many cases. Applying data from Planck HFI, the Wilkinson Microwave Anisotropy Probe (WMAP), and the Atacama Cosmology Telescope (ACT) to a model that incorporates contributions from Saturn’s rings to the planet’s total flux density suggests a best...
Statistical density of nuclear excited states
Directory of Open Access Journals (Sweden)
V. M. Kolomietz
2015-10-01
Full Text Available A semi-classical approximation is applied to the calculations of single-particle and statistical level densities in excited nuclei. Landau's conception of quasi-particles with the nucleon effective mass m* < m is used. The approach provides the correct description of the continuum contribution to the level density for realistic finite-depth potentials. It is shown that the continuum states does not affect significantly the thermodynamic calculations for sufficiently small temperatures T ≤ 1 MeV but reduce strongly the results for the excitation energy at high temperatures. By use of standard Woods - Saxon potential and nucleon effective mass m* = 0.7m the A-dependency of the statistical level density parameter K was evaluated in a good qualitative agreement with experimental data.
Density and polarizability of liquid 4He
International Nuclear Information System (INIS)
Kempin'ski, V.; Zhuk, T.; Stankovski, Ya.; Sitarzh, S.
1988-01-01
The temperature changes in the density of liquid helium are measured in the temperature range of 1.63 to 4.2 K.; Unlike the conventional pycnometric technique, the changes in the hydrostatic displacement of the liquid were determined. The cirrectness of the method chosen and the appropriate equipment for its realization are substantiated. The results obtained are in good agreement with those of other authors. On the basis of temperature measurements of the dependence of density ρ and permittivity ε, the dependence of polarizability A of liquid 4 He on temperature and density was calculated. The results obtained show an alternating character of the dependences A(T) and A(ρ). These dependences are found to correlate
Obliquely propagating dust-density waves
International Nuclear Information System (INIS)
Piel, A.; Arp, O.; Klindworth, M.; Melzer, A.
2008-01-01
Self-excited dust-density waves are experimentally studied in a dusty plasma under microgravity. Two types of waves are observed: a mode inside the dust volume propagating in the direction of the ion flow and another mode propagating obliquely at the boundary between the dusty plasma and the space charge sheath. The dominance of oblique modes can be described in the frame of a fluid model. It is shown that the results fom the fluid model agree remarkably well with a kinetic electrostatic model of Rosenberg [J. Vac. Sci. Technol. A 14, 631 (1996)]. In the experiment, the instability is quenched by increasing the gas pressure or decreasing the dust density. The critical pressure and dust density are well described by the models
Low-memory iterative density fitting.
Grajciar, Lukáš
2015-07-30
A new low-memory modification of the density fitting approximation based on a combination of a continuous fast multipole method (CFMM) and a preconditioned conjugate gradient solver is presented. Iterative conjugate gradient solver uses preconditioners formed from blocks of the Coulomb metric matrix that decrease the number of iterations needed for convergence by up to one order of magnitude. The matrix-vector products needed within the iterative algorithm are calculated using CFMM, which evaluates them with the linear scaling memory requirements only. Compared with the standard density fitting implementation, up to 15-fold reduction of the memory requirements is achieved for the most efficient preconditioner at a cost of only 25% increase in computational time. The potential of the method is demonstrated by performing density functional theory calculations for zeolite fragment with 2592 atoms and 121,248 auxiliary basis functions on a single 12-core CPU workstation. © 2015 Wiley Periodicals, Inc.
Sintered ceramics having controlled density and porosity
International Nuclear Information System (INIS)
Brassfield, H.C.; DeHollander, W.R.; Nivas, Y.
1980-01-01
A new method was developed for sintering ceramic uranium dioxide powders, in which ammonium oxalate is admixed with the powder prior to being pressed into a cylindrical green body, so that the end-point density of the final nuclear-reactor fuel product can be controlled. When the green body is heated, the ammonium oxalate decomposes and leaves discrete porosity in the sintered body, which corresponds to the ammonium oxalate regions in the green body. Thus the end-point density of the sintered body is a function of the amount of ammonium oxalate added. The final density of the sintered product is about 90-97% of the theoretical. The addition of ammonium oxalate also allows control of the pore size and distribution throughout the fuel. The process leaves substantially no impurities in the sintered strucuture. (DN)
Dingwell, Donald B.
1992-01-01
The density of Ga2O3 liquid in equilibrium with air has been measured at 18000 to 19000C using an Ir double-bob Archimedean method. The data yield the following description of the density of Ga2O3 liquid: ρ= 4.8374(84)–0.00065(12)(T −18500C). This density-temperature relationship is compared with the partial molar volume of Ga2O3 in glasses in the systems CaO–Ga2O3–SiO2 and Na2O–Ga2O3–SiO2, corrected to the glass transition temperature using thermal expansivities. The comparison illustrates t...
Engineering photonic density of states using metamaterials
DEFF Research Database (Denmark)
Jacob, Z.; Kim, J.Y.; Naik, G.V.
2010-01-01
The photonic density of states (PDOS), like its electronic counterpart, is one of the key physical quantities governing a variety of phenomena and hence PDOS manipulation is the route to new photonic devices. The PDOS is conventionally altered by exploiting the resonance within a device such as a......The photonic density of states (PDOS), like its electronic counterpart, is one of the key physical quantities governing a variety of phenomena and hence PDOS manipulation is the route to new photonic devices. The PDOS is conventionally altered by exploiting the resonance within a device...... such as a microcavity or a bandgap structure like a photonic crystal. Here we show that nanostructured metamaterials with hyperbolic dispersion can dramatically enhance the photonic density of states paving the way for metamaterial-based PDOS engineering....
Versatile Density Functionals for Computational Surface Science
DEFF Research Database (Denmark)
Wellendorff, Jess
Density functional theory (DFT) emerged almost 50 years ago. Since then DFT has established itself as the central electronic structure methodology for simulating atomicscale systems from a few atoms to a few hundred atoms. This success of DFT is due to a very favorable accuracy-to-computational c......Density functional theory (DFT) emerged almost 50 years ago. Since then DFT has established itself as the central electronic structure methodology for simulating atomicscale systems from a few atoms to a few hundred atoms. This success of DFT is due to a very favorable accuracy...... resampling techniques, thereby systematically avoiding problems with overfitting. The first ever density functional presenting both reliable accuracy and convincing error estimation is generated. The methodology is general enough to be applied to more complex functional forms with higher-dimensional fitting...
Combinatorial nuclear level-density model
International Nuclear Information System (INIS)
Uhrenholt, H.; Åberg, S.; Dobrowolski, A.; Døssing, Th.; Ichikawa, T.; Möller, P.
2013-01-01
A microscopic nuclear level-density model is presented. The model is a completely combinatorial (micro-canonical) model based on the folded-Yukawa single-particle potential and includes explicit treatment of pairing, rotational and vibrational states. The microscopic character of all states enables extraction of level-distribution functions with respect to pairing gaps, parity and angular momentum. The results of the model are compared to available experimental data: level spacings at neutron separation energy, data on total level-density functions from the Oslo method, cumulative level densities from low-lying discrete states, and data on parity ratios. Spherical and deformed nuclei follow basically different coupling schemes, and we focus on deformed nuclei
Quantum Entanglement and Reduced Density Matrices
Purwanto, Agus; Sukamto, Heru; Yuwana, Lila
2018-05-01
We investigate entanglement and separability criteria of multipartite (n-partite) state by examining ranks of its reduced density matrices. Firstly, we construct the general formula to determine the criterion. A rank of origin density matrix always equals one, meanwhile ranks of reduced matrices have various ranks. Next, separability and entanglement criterion of multipartite is determined by calculating ranks of reduced density matrices. In this article we diversify multipartite state criteria into completely entangled state, completely separable state, and compound state, i.e. sub-entangled state and sub-entangledseparable state. Furthermore, we also shorten the calculation proposed by the previous research to determine separability of multipartite state and expand the methods to be able to differ multipartite state based on criteria above.
Biometric recognition via fixation density maps
Rigas, Ioannis; Komogortsev, Oleg V.
2014-05-01
This work introduces and evaluates a novel eye movement-driven biometric approach that employs eye fixation density maps for person identification. The proposed feature offers a dynamic representation of the biometric identity, storing rich information regarding the behavioral and physical eye movement characteristics of the individuals. The innate ability of fixation density maps to capture the spatial layout of the eye movements in conjunction with their probabilistic nature makes them a particularly suitable option as an eye movement biometrical trait in cases when free-viewing stimuli is presented. In order to demonstrate the effectiveness of the proposed approach, the method is evaluated on three different datasets containing a wide gamut of stimuli types, such as static images, video and text segments. The obtained results indicate a minimum EER (Equal Error Rate) of 18.3 %, revealing the perspectives on the utilization of fixation density maps as an enhancing biometrical cue during identification scenarios in dynamic visual environments.
Gamma irradiation effects in low density polyethylene
International Nuclear Information System (INIS)
Ono, Lilian S.; Scagliusi, Sandra R.; Cardoso, Elisabeth E.L.; Lugao, Ademar B.
2011-01-01
Low density polyethylene (LDPE) is obtained from ethylene gas polymerization, being one of the most commercialized polymers due to its versatility and low cost. It's a semi-crystalline polymer, usually inactive at room temperature, capable to attain temperatures within a 80 deg C - 100 deg C range, without changing its physical-chemical properties. LDPE has more resistance when compared to its equivalent High Density Polyethylene (HDPE). LDPE most common applications consist in manufacturing of laboratory materials, general containers, pipes, plastic bags, etc. Gamma radiation is used on polymers in order to modify mechanical and physical-chemical features according to utility purposes. This work aims to the study of gamma (γ) radiation interaction with low density polyethylene to evaluate changes in its physical-chemical properties. Polymer samples were exposed to 5, 10, 15, 20 and 30kGy doses, at room temperature. Samples characterization employed Thermal Analysis, Melt Flow Index, Infrared Spectroscopy and Swelling tests. (author)
Residual Defect Density in Random Disks Deposits.
Topic, Nikola; Pöschel, Thorsten; Gallas, Jason A C
2015-08-03
We investigate the residual distribution of structural defects in very tall packings of disks deposited randomly in large channels. By performing simulations involving the sedimentation of up to 50 × 10(9) particles we find all deposits to consistently show a non-zero residual density of defects obeying a characteristic power-law as a function of the channel width. This remarkable finding corrects the widespread belief that the density of defects should vanish algebraically with growing height. A non-zero residual density of defects implies a type of long-range spatial order in the packing, as opposed to only local ordering. In addition, we find deposits of particles to involve considerably less randomness than generally presumed.
Hounsfield unit density accurately predicts ESWL success.
Magnuson, William J; Tomera, Kevin M; Lance, Raymond S
2005-01-01
Extracorporeal shockwave lithotripsy (ESWL) is a commonly used non-invasive treatment for urolithiasis. Helical CT scans provide much better and detailed imaging of the patient with urolithiasis including the ability to measure density of urinary stones. In this study we tested the hypothesis that density of urinary calculi as measured by CT can predict successful ESWL treatment. 198 patients were treated at Alaska Urological Associates with ESWL between January 2002 and April 2004. Of these 101 met study inclusion with accessible CT scans and stones ranging from 5-15 mm. Follow-up imaging demonstrated stone freedom in 74.2%. The overall mean Houndsfield density value for stone-free compared to residual stone groups were significantly different ( 93.61 vs 122.80 p ESWL for upper tract calculi between 5-15mm.
Propulsion Physics Using the Chameleon Density Model
Robertson, Glen A.
2011-01-01
To grow as a space faring race, future spaceflight systems will require a new theory of propulsion. Specifically one that does not require mass ejection without limiting the high thrust necessary to accelerate within or beyond our solar system and return within a normal work period or lifetime. The Chameleon Density Model (CDM) is one such model that could provide new paths in propulsion toward this end. The CDM is based on Chameleon Cosmology a dark matter theory; introduced by Khrouy and Weltman in 2004. Chameleon as it is hidden within known physics, where the Chameleon field represents a scalar field within and about an object; even in the vacuum. The CDM relates to density changes in the Chameleon field, where the density changes are related to matter accelerations within and about an object. These density changes in turn change how an object couples to its environment. Whereby, thrust is achieved by causing a differential in the environmental coupling about an object. As a demonstration to show that the CDM fits within known propulsion physics, this paper uses the model to estimate the thrust from a solid rocket motor. Under the CDM, a solid rocket constitutes a two body system, i.e., the changing density of the rocket and the changing density in the nozzle arising from the accelerated mass. Whereby, the interactions between these systems cause a differential coupling to the local gravity environment of the earth. It is shown that the resulting differential in coupling produces a calculated value for the thrust near equivalent to the conventional thrust model used in Sutton and Ross, Rocket Propulsion Elements. Even though imbedded in the equations are the Universe energy scale factor, the reduced Planck mass and the Planck length, which relates the large Universe scale to the subatomic scale.
Negative density-distribution relationship in butterflies
Directory of Open Access Journals (Sweden)
Kotiaho Janne S
2005-03-01
Full Text Available Abstract Background Because "laws of nature" do not exist in ecology, much of the foundations of community ecology rely on broad statistical generalisations. One of the strongest generalisations is the positive relationship between density and distribution within a given taxonomic assemblage; that is, locally abundant species are more widespread than locally sparse species. Several mechanisms have been proposed to create this positive relationship, and the testing of these mechanisms is attracting increasing attention. Results We report a strong, but counterintuitive, negative relationship between density and distribution in the butterfly fauna of Finland. With an exceptionally comprehensive data set (data includes all 95 resident species in Finland and over 1.5 million individuals, we have been able to submit several of the mechanisms to powerful direct empirical testing. Without exception, we failed to find evidence for the proposed mechanisms creating a positive density-distribution relationship. On the contrary, we found that many of the mechanisms are equally able to generate a negative relationship. Conclusion We suggest that one important determinant of density-distribution relationships is the geographical location of the study: on the edge of a distribution range, suitable habitat patches are likely to be more isolated than in the core of the range. In such a situation, only the largest and best quality patches are likely to be occupied, and these by definition can support a relatively dense population leading to a negative density-distribution relationship. Finally, we conclude that generalizations about the positive density-distribution relationship should be made more cautiously.
Density and geometry of single component plasmas
International Nuclear Information System (INIS)
Speck, A.; Gabrielse, G.; Larochelle, P.; Le Sage, D.; Levitt, B.; Kolthammer, W.S.; McConnell, R.; Wrubel, J.; Grzonka, D.; Oelert, W.; Sefzick, T.; Zhang, Z.; Comeau, D.; George, M.C.; Hessels, E.A.; Storry, C.H.; Weel, M.; Walz, J.
2007-01-01
The density and geometry of p-bar and e + plasmas in realistic trapping potentials are required to understand and optimize antihydrogen (H-bar) formation. An aperture method and a quadrupole oscillation frequency method for characterizing such plasmas are compared for the first time, using electrons in a cylindrical Penning trap. Both methods are used in a way that makes it unnecessary to assume that the plasmas are spheroidal, and it is shown that they are not. Good agreement between the two methods illustrates the possibility to accurately determine plasma densities and geometries within non-idealized, realistic trapping potentials
Development of nuclear density and moisture gauges
International Nuclear Information System (INIS)
Zhu Huaian; Zhu Dichen; Jiang Yulan; Yin Xiling; Li Jianwen; Cheng Jianbing; Yan Haiqing
1993-01-01
The model MT5012 nuclear density and moisture gauge is an advanced portable meter to inspect the compactness of a highway roadbed and pavement foundation. It has perfect functions and the advantage of quickness, accuracy and non-destruction. It is also applicable to civil engineering, such as railway, airport and embankment. The model MT5022 nuclear density and moisture gauge is a mobile meter for continuous inspection and control of the compactness of a highway and pavement foundation. It can be installed on road roller, wheelbarrow and other traffic machines while working, and is more efficient than the portable ones
Density and geometry of single component plasmas
Speck, A; Larochelle, P; Le Sage, D; Levitt, B; Kolthammer, W S; McConnell, R; Wrubel, J; Grzonka, D; Oelert, W; Sefzick, T; Zhang, Z; Comeau, D; George, M C; Hessels, E A; Storry, C H; Weel, M; Walz, J
2007-01-01
The density and geometry of p¯ and e+ plasmas in realistic trapping potentials are required to understand and optimize antihydrogen (H¯) formation. An aperture method and a quadrupole oscillation frequency method for characterizing such plasmas are compared for the first time, using electrons in a cylindrical Penning trap. Both methods are used in a way that makes it unnecessary to assume that the plasmas are spheroidal, and it is shown that they are not. Good agreement between the two methods illustrates the possibility to accurately determine plasma densities and geometries within non-idealized, realistic trapping potentials.
Tables of nuclear level density parameters
International Nuclear Information System (INIS)
Chatterjee, A.; Ghosh, S.K.; Majumdar, H.
1976-03-01
The Renormalized Gas Model (RGM) has been used to calculate single particle level density parameters for more than 2000 nucleides over the range 9<=Z<=126 (15<=A<=338). Three separate tables present the elements on or near the valley of beta stability, neutron-rich fission fragment nucleides, and transitional nuclei, actinides and light-mass super heavy elements. Each table identifies the nucleus in terms of Z and N and presents the RGM deformation energy of binding, the total RGM structural energy correction over the free gas Fermi surface, and the level density parameter
Communication: Simple liquids' high-density viscosity
Costigliola, Lorenzo; Pedersen, Ulf R.; Heyes, David M.; Schrøder, Thomas B.; Dyre, Jeppe C.
2018-02-01
This paper argues that the viscosity of simple fluids at densities above that of the triple point is a specific function of temperature relative to the freezing temperature at the density in question. The proposed viscosity expression, which is arrived at in part by reference to the isomorph theory of systems with hidden scale invariance, describes computer simulations of the Lennard-Jones system as well as argon and methane experimental data and simulation results for an effective-pair-potential model of liquid sodium.
Maximum entropy method in momentum density reconstruction
International Nuclear Information System (INIS)
Dobrzynski, L.; Holas, A.
1997-01-01
The Maximum Entropy Method (MEM) is applied to the reconstruction of the 3-dimensional electron momentum density distributions observed through the set of Compton profiles measured along various crystallographic directions. It is shown that the reconstruction of electron momentum density may be reliably carried out with the aid of simple iterative algorithm suggested originally by Collins. A number of distributions has been simulated in order to check the performance of MEM. It is shown that MEM can be recommended as a model-free approach. (author). 13 refs, 1 fig
The number density of a charged relic
International Nuclear Information System (INIS)
Berger, C.F.; Kraml, S.; Palorini, F.
2008-07-01
We investigate scenarios in which a charged, long-lived scalar particle decouples from the primordial plasma in the Early Universe. We compute the number density at time of freeze-out considering both the cases of abelian and non-abelian interactions and including the effect of Sommerfeld enhancement at low initial velocity. We also discuss as extreme case the maximal cross section that fulfils the unitarity bound. We then compare these number densities to the exotic nuclei searches for stable relics and to the BBN bounds on unstable relics and draw conclusions for the cases of a stau or stop NLSP in supersymmetric models with a gravitino or axino LSP. (orig.)
Communication: Simple liquids' high-density viscosity.
Costigliola, Lorenzo; Pedersen, Ulf R; Heyes, David M; Schrøder, Thomas B; Dyre, Jeppe C
2018-02-28
This paper argues that the viscosity of simple fluids at densities above that of the triple point is a specific function of temperature relative to the freezing temperature at the density in question. The proposed viscosity expression, which is arrived at in part by reference to the isomorph theory of systems with hidden scale invariance, describes computer simulations of the Lennard-Jones system as well as argon and methane experimental data and simulation results for an effective-pair-potential model of liquid sodium.
Density and energy of supernova remnants
Energy Technology Data Exchange (ETDEWEB)
Canto, J [Manchester Univ. (UK). Dept. of Astronomy
1977-12-01
The effects of an interstellar magnetic field on the gas flow behind a strong shock front are considered. The ambient density and energy of supernova remnants are estimated from the intensity ratio of sulphur lines I(6717)/I(6731). It is found that, on average, the ambient density around galactic supernova remnants is 4 cm/sup -3/. The total energy appears to be the same for all supernova remnants (to within a factor = approximately 5). A mean value of 4 10/sup 51/ erg is found.
Excited-state density functional theory
International Nuclear Information System (INIS)
Harbola, Manoj K; Hemanadhan, M; Shamim, Md; Samal, P
2012-01-01
Starting with a brief introduction to excited-state density functional theory, we present our method of constructing modified local density approximated (MLDA) energy functionals for the excited states. We show that these functionals give accurate results for kinetic energy and exchange energy compared to the ground state LDA functionals. Further, with the inclusion of GGA correction, highly accurate total energies for excited states are obtained. We conclude with a brief discussion on the further direction of research that include the construction of correlation energy functional and exchange potential for excited states.
High density data recording for SSCL linac
International Nuclear Information System (INIS)
VanDeusen, A.L.; Crist, C.
1993-01-01
The Superconducting Super Collider Laboratory and AlliedSignal Aerospace have collaboratively developed a high density data monitoring system for beam diagnostic activities. The 128 channel data system is based on a custom multi-channel high speed digitizer card for the VXI bus. The card is referred to as a Modular Input VXI (MIX) digitizer. Multiple MIX cards are used in the complete system to achieve the necessary high channel density requirements. Each MIX digitizer card also contains programmable signal conditioning, and enough local memory to complete an entire beam scan without assistance from the host processor
The number density of a charged relic
Energy Technology Data Exchange (ETDEWEB)
Berger, C.F. [Massachusetts Institute of Technology, Cambridge, MA (United States). Center for Theoretical Physics]|[California Univ., Santa Barbara, CA (United States). Kavli Inst. for Theoretical Physics; Covi, L. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kraml, S. [CNRS/IN2P3, Grenoble (France). Lab. de Physique Subatomique et de Cosmologie; Palorini, F. [Lyon Univ., UCBL, CNRS/IN2P3, Villeurbanne (France). IPN de Lyon
2008-07-15
We investigate scenarios in which a charged, long-lived scalar particle decouples from the primordial plasma in the Early Universe. We compute the number density at time of freeze-out considering both the cases of abelian and non-abelian interactions and including the effect of Sommerfeld enhancement at low initial velocity. We also discuss as extreme case the maximal cross section that fulfils the unitarity bound. We then compare these number densities to the exotic nuclei searches for stable relics and to the BBN bounds on unstable relics and draw conclusions for the cases of a stau or stop NLSP in supersymmetric models with a gravitino or axino LSP. (orig.)
Particle acceleration in near critical density plasma
International Nuclear Information System (INIS)
Gu, Y.J.; Kong, Q.; Kawata, S.; Izumiyama, T.; Nagashima, T.
2013-01-01
Charged particle acceleration schemes driven by ultra intense laser and near critical density plasma interactions are presented. They include electron acceleration in a plasma channel, ion acceleration by the Coulomb explosion and high energy electron beam driven ion acceleration. It is found that under the near critical density plasma both ions and electrons are accelerated with a high acceleration gradient. The electron beam containing a large charge quantity is accelerated well with 23 GeV/cm. The collimated ion bunch reaches 1 GeV. The investigations and discussions are based on 2.5D PIC (particle-in-cell) simulations. (author)
Fish stocking density impacts tank hydrodynamics
DEFF Research Database (Denmark)
Rasmussen, Michael R.; Lunger, Angela; Laursen, Jesper
2006-01-01
The effect of stocking density upon the hydrodynamics of a circular tank, configured in a recirculation system, was investigated. Red drums Sciaenops ocellatus of approximately 140 g wet weight, were stocked at five rates varying from 0 to 12 kg m-3. The impact of the presence of fish upon tank...... hydrodynamics was established using in-tank-based Rhodamine WT fluorometry at a flow rate of 0.23 l s-1 (tank exchange rate of 1.9 h-1). With increasing numbers of animals, curvilinear relationships were observed for dispersion coefficients and tank mixing times. Stocking densities of 3, 6, 9 and 12 kg m-3...
Level densities in rare earth nuclei
International Nuclear Information System (INIS)
Siem, S.; Tveter, T.S.; Bergholt, L.; Guttormsen, M.; Melby, E.; Rekstad, J.
1997-01-01
An iterative procedure for simultaneous extraction of fine structure in the level density and the γ-ray strength function from a set of primary γ-ray spectra has been developed. Data from the reactions 163 Dy(3He,αγ) 172 Dy and 173 Yb(3He,αγ) 172 Yb reveals step like enhancements in the level density in the region below 5 MeV and peaks in the γ-ray strength function at low γ-energy (E γ ∼ 2 - 3.5 MeV). Tentative physical interpretations are presented. (author)
Directory of Open Access Journals (Sweden)
Sikandar Hayat Khan
2017-01-01
Full Text Available Background. Recent literature in lipidology has identified LDL-fractions to be more atherogenic. In this regard, small density LDL-cholesterol (sdLDLc has been considered to possess more atherogenicity than other LDL-fractions like large buoyant LDL-cholesterol (lbLDLc. Recently, Srisawasdi et al. have developed a method for calculating sdLDLc and lbLDLc based upon a regression equation. Using that in developing world may provide us with a valuable tool for ASCVD risk prediction. Objective. (1 To correlate directly measured and calculated lipid indices with insulin resistance, UACR, glycated hemoglobin, anthropometric indices, and blood pressure. (2 To evaluate these lipid parameters in subjects with or without metabolic syndrome, nephropathy, and hypertension and among various groups based upon glycated hemoglobin results. Design. Cross-sectional study. Place and Duration of Study. From Jan 2016 to 15 April 2017. Subjects and Methods. Finally enrolled subjects (male: 110, female: 122 were evaluated for differences in various lipid parameters, including measured LDL-cholesterol (mLDLc, HDLc and calculated LDL-cholesterol (cLDLc, non-HDLc, sdLDLC, lbLDLC, and their ratio among subjects with or without metabolic syndrome, nephropathy, glycation index, anthropometric indices, and hypertension. Results. Significant but weak correlation was mainly observed between anthropometric indices, insulin resistance, blood pressure, and nephropathy for non-HDLc, sdLDLc, and sdLDLc/lbLDLc. Generally lipid indices were higher among subjects with metabolic syndrome [{sdLDLc: 0.92 + 0.33 versus 0.70 + 0.29 (p 7.0%. Subjects having nephropathy (UACR > 2.4 mg/g had higher concentration of non-HDLc levels in comparison to sdLDLc [{non-HDLc: 3.68 + 0.59 versus 3.36 + 0.43} (p=0.007, {sdLDLc: 0.83 + 0.27 versus 0.75 + 0.35 (p=NS}]. Conclusion. Lipid markers including cLDLc and mLDLc are less associated with traditional ASCVD markers than non-HDLc, sdLDLc, and sd
Owens, Peter M; Titus-Ernstoff, Linda; Gibson, Lucinda; Beach, Michael L; Beauregard, Sandy; Dalton, Madeline A
2010-02-12
Studies involving the built environment have typically relied on US Census data to measure residential density. However, census geographic units are often unsuited to health-related research, especially in rural areas where development is clustered and discontinuous. We evaluated the accuracy of both standard census methods and alternative GIS-based methods to measure rural density. We compared residential density (units/acre) in 335 Vermont school neighborhoods using conventional census geographic units (tract, block group and block) with two GIS buffer measures: a 1-kilometer (km) circle around the school and a 1-km circle intersected with a 100-meter (m) road-network buffer. The accuracy of each method was validated against the actual residential density for each neighborhood based on the Vermont e911 database, which provides an exact geo-location for all residential structures in the state. Standard census measures underestimate residential density in rural areas. In addition, the degree of error is inconsistent so even the relative rank of neighborhood densities varies across census measures. Census measures explain only 61% to 66% of the variation in actual residential density. In contrast, GIS buffer measures explain approximately 90% of the variation. Combining a 1-km circle with a road-network buffer provides the closest approximation of actual residential density. Residential density based on census units can mask clusters of development in rural areas and distort associations between residential density and health-related behaviors and outcomes. GIS-defined buffers, including a 1-km circle and a road-network buffer, can be used in conjunction with census data to obtain a more accurate measure of residential density.
Directory of Open Access Journals (Sweden)
Gibson Lucinda
2010-02-01
Full Text Available Abstract Background Studies involving the built environment have typically relied on US Census data to measure residential density. However, census geographic units are often unsuited to health-related research, especially in rural areas where development is clustered and discontinuous. Objective We evaluated the accuracy of both standard census methods and alternative GIS-based methods to measure rural density. Methods We compared residential density (units/acre in 335 Vermont school neighborhoods using conventional census geographic units (tract, block group and block with two GIS buffer measures: a 1-kilometer (km circle around the school and a 1-km circle intersected with a 100-meter (m road-network buffer. The accuracy of each method was validated against the actual residential density for each neighborhood based on the Vermont e911 database, which provides an exact geo-location for all residential structures in the state. Results Standard census measures underestimate residential density in rural areas. In addition, the degree of error is inconsistent so even the relative rank of neighborhood densities varies across census measures. Census measures explain only 61% to 66% of the variation in actual residential density. In contrast, GIS buffer measures explain approximately 90% of the variation. Combining a 1-km circle with a road-network buffer provides the closest approximation of actual residential density. Conclusion Residential density based on census units can mask clusters of development in rural areas and distort associations between residential density and health-related behaviors and outcomes. GIS-defined buffers, including a 1-km circle and a road-network buffer, can be used in conjunction with census data to obtain a more accurate measure of residential density.
Local density approximation for exchange in excited-state density functional theory
Harbola, Manoj K.; Samal, Prasanjit
2004-01-01
Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies.
Density-density functionals and effective potentials in many-body electronic structure calculations
International Nuclear Information System (INIS)
Reboredo, Fernando A.; Kent, Paul R.
2008-01-01
We demonstrate the existence of different density-density functionals designed to retain selected properties of the many-body ground state in a non-interacting solution starting from the standard density functional theory ground state. We focus on diffusion quantum Monte Carlo applications that require trial wave functions with optimal Fermion nodes. The theory is extensible and can be used to understand current practices in several electronic structure methods within a generalized density functional framework. The theory justifies and stimulates the search of optimal empirical density functionals and effective potentials for accurate calculations of the properties of real materials, but also cautions on the limits of their applicability. The concepts are tested and validated with a near-analytic model.
Low density, variation in sintered density and high nitrogen in uranium dioxide
International Nuclear Information System (INIS)
Balakrishna, Palanki; Murty, B.N.; Anuradha, M.; Nageshwara Rao, P.; Jayaraj, R.N.; Ganguly, C.
2000-01-01
Low sintered density and density variation in sintered UO 2 were found to have been caused by non uniformity in the granule feed characteristics to the compacting press. The nitrogen impurity content of sintered UO 2 was found to be sintering furnace related and associated with low sintered density pellets. The problems of low density, variation in sintered density and high nitrogen could be solved by the replacement of the prevailing four punch precompaction by a single punch process; by the introduction of a vibro-sieve for the separation of fine particles from the press feed granules; by innovation in the powder feed shoe design for simultaneous and uniform dispensing of powder in all the die holes; by increasing the final compaction pressure and by modifying the gas flows and preheat temperature in the sintering furnace. (author)
Single-particle energies and density of states in density functional theory
van Aggelen, H.; Chan, G. K.-L.
2015-07-01
Time-dependent density functional theory (TD-DFT) is commonly used as the foundation to obtain neutral excited states and transition weights in DFT, but does not allow direct access to density of states and single-particle energies, i.e. ionisation energies and electron affinities. Here we show that by extending TD-DFT to a superfluid formulation, which involves operators that break particle-number symmetry, we can obtain the density of states and single-particle energies from the poles of an appropriate superfluid response function. The standard Kohn- Sham eigenvalues emerge as the adiabatic limit of the superfluid response under the assumption that the exchange- correlation functional has no dependence on the superfluid density. The Kohn- Sham eigenvalues can thus be interpreted as approximations to the ionisation energies and electron affinities. Beyond this approximation, the formalism provides an incentive for creating a new class of density functionals specifically targeted at accurate single-particle eigenvalues and bandgaps.
High-Latitude Neutral Mass Density Maxima
Huang, C. Y.; Huang, Y.; Su, Y.-J.; Huang, T.; Sutton, E. K.
2017-10-01
Recent studies have reported that thermospheric effects due to solar wind driving can be observed poleward of auroral latitudes. In these papers, the measured neutral mass density perturbations appear as narrow, localized maxima in the cusp and polar cap. They conclude that Joule heating below the spacecraft is the cause of the mass density increases, which are sometimes associated with local field-aligned current structures, but not always. In this paper we investigate neutral mass densities measured by accelerometers on the CHAllenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) spacecraft from launch until years 2010 (CHAMP) and 2012 (GRACE), approximately 10 years of observations from each satellite. We extract local maxima in neutral mass densities over the background using a smoothing window with size of one quarter of the orbit. The maxima have been analyzed for each year and also for the duration of each set of satellite observations. We show where they occur, under what solar wind conditions, and their relation to magnetic activity. The region with the highest frequency of occurrence coincides approximately with the cusp and mantle, with little direct evidence of an auroral zone source. Our conclusions agree with the "hot polar cap" observations that have been reported and studied in the past.
Optimal stocking densities of snails [ Archachatina marginata ...
African Journals Online (AJOL)
Optimal stocking densities of breeding and fattening snails [Archachatina marginata Saturalis A.m.s (Swainson)] were determined through two experiments (five treatments, four replicates and randomised complete block design each) between April and December 1998.Experiment 1 had 3,6, 12, 17 and 22 A.m.s. adult ...
Does low surface brightness mean low density?
deBlok, WJG; McGaugh, SS
1996-01-01
We compare the dynamical properties of two galaxies at identical positions on the Tully-Fisher relation, but with different surface brightnesses. We find that the low surface brightness galaxy UGC 128 has a higher mass-to-light ratio, and yet has lower mass densities than the high surface brightness
Effective Lagrangian density in gauge supersymmetry
International Nuclear Information System (INIS)
Chang, S.S.
1976-01-01
In the framework of gauge supersymmetry proposed by Arnowitt and Nath, an effective Lagrangian density is formally rewritten in terms of a spontaneously broken vacuum metric and the remaining perturbative part in the gauge metric tensor. Tensor notations in the superspace are revised so that all sign factors of Grassmann parities appear more systematically
Estimation and display of beam density profiles
Energy Technology Data Exchange (ETDEWEB)
Dasgupta, S; Mukhopadhyay, T; Roy, A; Mallik, C
1989-03-15
A setup in which wire-scanner-type beam-profile monitor data are collected on-line in a nuclear data-acquisition system has been used and a simple algorithm for estimation and display of the current density distribution in a particle beam is described.
Magnet and device for magnetic density separation
Polinder, H.; Rem, P.C.
2014-01-01
A planar magnet for magnetic density separation, comprising an array of pole pieces succeeding in longitudinal direction of a mounting plane, each pole piece having a body extending transversely along the mounting plane with a substantially constant cross section that includes a top segment that is
Supernovae and high density nuclear matter
International Nuclear Information System (INIS)
Kahana, S.
1986-01-01
The role of the nuclear equation of state (EOS) in producing prompt supernova explosions is examined. Results of calculations of Baron, Cooperstein, and Kahana incorporating general relativity and a new high density EOS are presented, and the relevance of these calculations to laboratory experiments with heavy ions considered. 31 refs., 6 figs., 2 tabs
Symbol recognition with kernel density matching.
Zhang, Wan; Wenyin, Liu; Zhang, Kun
2006-12-01
We propose a novel approach to similarity assessment for graphic symbols. Symbols are represented as 2D kernel densities and their similarity is measured by the Kullback-Leibler divergence. Symbol orientation is found by gradient-based angle searching or independent component analysis. Experimental results show the outstanding performance of this approach in various situations.
Theory to determine the critical charge density
International Nuclear Information System (INIS)
Vila, F.
1997-08-01
In this paper we theoretically determine the critical charge density in the system earthed metallic sphere-uniformly charged dielectric plane, in presence of earthed surfaces. This is a situation frequently encountered in industrial condition and has a great importance to evaluate the danger of the electrostatic discharges. (author)
Supernovae and high density nuclear matter
Energy Technology Data Exchange (ETDEWEB)
Kahana, S.
1986-01-01
The role of the nuclear equation of state (EOS) in producing prompt supernova explosions is examined. Results of calculations of Baron, Cooperstein, and Kahana incorporating general relativity and a new high density EOS are presented, and the relevance of these calculations to laboratory experiments with heavy ions considered. 31 refs., 6 figs., 2 tabs.
High density implosion experiments at Nova
International Nuclear Information System (INIS)
Cable, M.D.; Hatchett, S.P.; Nelson, M.B.; Lerche, R.A.; Murphy, T.J.; Ress, D.B.
1994-01-01
Deuterium filled glass microballoons are used as indirectly driven targets for implosion experiments at the Nova Laser Fusion Facility. High levels of laser precision were required to achieve fuel densities and convergences to an ignition scale hot spot. (AIP) copyright 1994 American Institute of Physics
Current density profile evolution in JET
International Nuclear Information System (INIS)
Stubberfield, P.M.; Balet, B.; Campbell, D.; Challis, C.D.; Cordey, J.G.; O'Rourke, J.; Hammett, G.; Schmidt, G.L.
1989-01-01
Simulation studies have been made of the current density profile evolution in discharges where the bootstrap current is expected to be significant. The changes predicted in the total current profile have been confirmed by comparison with experimental results. (author) 8 refs., 6 figs
Elastic reflection waveform inversion with variable density
Li, Yuanyuan
2017-08-17
Elastic full waveform inversion (FWI) provides a better description of the subsurface than those given by the acoustic assumption. However it suffers from a more serious cycle skipping problem compared with the latter. Reflection waveform inversion (RWI) provides a method to build a good background model, which can serve as an initial model for elastic FWI. Therefore, we introduce the concept of RWI for elastic media, and propose elastic RWI with variable density. We apply Born modeling to generate the synthetic reflection data by using optimized perturbations of P- and S-wave velocities and density. The inversion for the perturbations in P- and S-wave velocities and density is similar to elastic least-squares reverse time migration (LSRTM). An incorrect initial model will lead to some misfits at the far offsets of reflections; thus, can be utilized to update the background velocity. We optimize the perturbation and background models in a nested approach. Numerical tests on the Marmousi model demonstrate that our method is able to build reasonably good background models for elastic FWI with absence of low frequencies, and it can deal with the variable density, which is needed in real cases.
Finite size scaling and spectral density studies
International Nuclear Information System (INIS)
Berg, B.A.
1991-01-01
Finite size scaling (FSS) and spectral density (SD) studies are reported for the deconfining phase transition. This talk concentrates on Monte Carlo (MC) results for pure SU(3) gauge theory, obtained in collaboration with Alves and Sanielevici, but the methods are expected to be useful for full QCD as well. (orig.)
Direct sampling for stand density index
Mark J. Ducey; Harry T. Valentine
2008-01-01
A direct method of estimating stand density index in the field, without complex calculations, would be useful in a variety of silvicultural situations. We present just such a method. The approach uses an ordinary prism or other angle gauge, but it involves deliberately "pushing the point" or, in some cases, "pulling the point." This adjusts the...
Density functional theory of polydisperse fluid interfaces
International Nuclear Information System (INIS)
Baus, M.; Bellier-Castella, L.; Xu, H.
2002-01-01
Most colloids usually exhibit one or several polydispersities. A natural framework for the theoretical description of polydisperse systems is provided by the extension of density functional theory to 'continuous' mixtures. This will be illustrated here by the study of both the bulk and interfacial properties of a simple van der Waals model for a polydisperse colloidal fluid. (author)
does earthworms density really modify soil's hydrodynamic ...
African Journals Online (AJOL)
N. Ababsa,, M. Kribaa, D. Addad, L. Tamrabet and M. Baha
1 mai 2016 ... Journal of Fundamental and Applied Sciences is licensed under a Creative Commons Attribution-NonCommercial 4.0. International License. Libraries Resource Directory. We are listed under Research Associations category. DOES EARTHWORMS DENSITY REALLY MODIFY SOIL'S HYDRODYNAMIC.
The temporal variability of species densities
International Nuclear Information System (INIS)
Redfearn, A.; Pimm, S.L.
1993-01-01
Ecologists use the term 'stability' to mean to number of different things (Pimm 1984a). One use is to equate stability with low variability in population density over time (henceforth, temporal variability). Temporal variability varies greatly from species to species, so what effects it? There are at least three sets of factors: the variability of extrinsic abiotic factors, food web structure, and the intrinsic features of the species themselves. We can measure temporal variability using at least three statistics: the coefficient of variation of density (CV); the standard deviation of the logarithms of density (SDL); and the variance in the differences between logarithms of density for pairs of consecutive years (called annual variability, hence AV, b y Wolda 1978). There are advantages and disadvantages to each measure (Williamson 1984), though in our experience, the measures are strongly correlated across sets of taxonomically related species. The increasing availability of long-term data sets allows one to calculate these statistics for many species and so to begin to understand the various causes of species differences in temporal variability
Chemical hardness and density functional theory
Indian Academy of Sciences (India)
Unknown
RALPH G PEARSON. Chemistry Department, University of California, Santa Barbara, CA 93106, USA. Abstract. The concept of chemical hardness is reviewed from a personal point of view. Keywords. Hardness; softness; hard & soft acids bases (HSAB); principle of maximum hardness. (PMH) density functional theory (DFT) ...
Apparatus for measurement of tree core density
International Nuclear Information System (INIS)
Blincow, D.W.
1975-01-01
Apparatus is described for direct measurement of the density of a core sample from a tree. A radiation source and detector with a receptacle for the core therebetween, an integrator unit for the detector output, and an indicating meter driven by the integrator unit are described