Evaluation of Gas Phase Dispersion in Flotation under Predetermined Hydrodynamic Conditions

Science.gov (United States)

Młynarczykowska, Anna; Oleksik, Konrad; Tupek-Murowany, Klaudia

2018-03-01

Results of various investigations shows the relationship between the flotation parameters and gas distribution in a flotation cell. The size of gas bubbles is a random variable with a specific distribution. The analysis of this distribution is useful to make mathematical description of the flotation process. The flotation process depends on many variable factors. These are mainly occurrences like collision of single particle with gas bubble, adhesion of particle to the surface of bubble and detachment process. These factors are characterized by randomness. Because of that it is only possible to talk about the probability of occurence of one of these events which directly affects the speed of the process, thus a constant speed of flotation process. Probability of the bubble-particle collision in the flotation chamber with mechanical pulp agitation depends on the surface tension of the solution, air consumption, degree of pul aeration, energy dissipation and average feed particle size. Appropriate identification and description of the parameters of the dispersion of gas bubbles helps to complete the analysis of the flotation process in a specific physicochemical conditions and hydrodynamic for any raw material. The article presents the results of measurements and analysis of the gas phase dispersion by the size distribution of air bubbles in a flotation chamber under fixed hydrodynamic conditions. The tests were carried out in the Laboratory of Instrumental Methods in Department of Environmental Engineering and Mineral Processing, Faculty of Mining and Geoengineerin, AGH Univeristy of Science and Technology in Krakow.

Light-pressure-induced nonlinear dispersion of a laser field interacting with an atomic gas

International Nuclear Information System (INIS)

Grimm, R.; Mlynek, J.

1990-01-01

We report on detailed studies of the effect of resonant light pressure on the optical response of an atomic gas to a single monochromatic laser field. In this very elementary situation of laser spectroscopy, the redistribution of atomic velocities that is induced by spontaneous light pressure leads to a novel contribution to the optical dispersion curve of the medium. This light-pressure-induced dispersion phenomenon displays a pronounced nonlinear dependence on the laser intensity. Moreover, for a given intensity, its strength is closely related to the laser beam diameter. As most important feature, this light-pressure-induced dispersion displays an even symmetry with respect to the optical detuning from line center. As a result, the total Doppler-broadened dispersion curve of the gas can become asymmetric, and a significant shift of the dispersion line center can occur. In addition to a detailed theoretical description of the phenomenon, we report on its experimental investigation on the λ=555.6 nm 1 S 0 - 3 P 1 transition in atomic ytterbium vapor with the use of frequency-modulation spectroscopy. The experimental findings are in good quantitative agreement with theoretical predictions

Generation of multiple VUV dispersive waves using a tapered gas-filled hollow-core anti-resonant fiber

DEFF Research Database (Denmark)

Habib, Md Selim; Markos, Christos; Bang, Ole

2017-01-01

Hollow-core anti-resonant (HC-AR) fibers are perhaps the best platform for ultrafast nonlinear optics based on light-gas interactions because they offer broadband guidance and low-loss guidance. The main advantage of using gases inside HC fibers is that both the dispersion and nonlinearity can...... be tuned by simply changing the pressure of the gas [1]. The emission of efficient dispersive wave (DW) in the deep-UV has been already observed in a uniform Ar-filled hollow-core fiber with tunability from 200 to 320 nm by changing the gas pressure and pulse energy [2]. In the quest of optimizing...

Numerical Simulation of Dispersion from Urban Greenhouse Gas Sources

Science.gov (United States)

Nottrott, Anders; Tan, Sze; He, Yonggang; Winkler, Renato

2017-04-01

Cities are characterized by complex topography, inhomogeneous turbulence, and variable pollutant source distributions. These features create a scale separation between local sources and urban scale emissions estimates known as the Grey-Zone. Modern computational fluid dynamics (CFD) techniques provide a quasi-deterministic, physically based toolset to bridge the scale separation gap between source level dynamics, local measurements, and urban scale emissions inventories. CFD has the capability to represent complex building topography and capture detailed 3D turbulence fields in the urban boundary layer. This presentation discusses the application of OpenFOAM to urban CFD simulations of natural gas leaks in cities. OpenFOAM is an open source software for advanced numerical simulation of engineering and environmental fluid flows. When combined with free or low cost computer aided drawing and GIS, OpenFOAM generates a detailed, 3D representation of urban wind fields. OpenFOAM was applied to model scalar emissions from various components of the natural gas distribution system, to study the impact of urban meteorology on mobile greenhouse gas measurements. The numerical experiments demonstrate that CH4 concentration profiles are highly sensitive to the relative location of emission sources and buildings. Sources separated by distances of 5-10 meters showed significant differences in vertical dispersion of plumes, due to building wake effects. The OpenFOAM flow fields were combined with an inverse, stochastic dispersion model to quantify and visualize the sensitivity of point sensors to upwind sources in various built environments. The Boussinesq approximation was applied to investigate the effects of canopy layer temperature gradients and convection on sensor footprints.

A simple measurement method of molecular relaxation in a gas by reconstructing acoustic velocity dispersion

Science.gov (United States)

Zhu, Ming; Liu, Tingting; Zhang, Xiangqun; Li, Caiyun

2018-01-01

Recently, a decomposition method of acoustic relaxation absorption spectra was used to capture the entire molecular multimode relaxation process of gas. In this method, the acoustic attenuation and phase velocity were measured jointly based on the relaxation absorption spectra. However, fast and accurate measurements of the acoustic attenuation remain challenging. In this paper, we present a method of capturing the molecular relaxation process by only measuring acoustic velocity, without the necessity of obtaining acoustic absorption. The method is based on the fact that the frequency-dependent velocity dispersion of a multi-relaxation process in a gas is the serial connection of the dispersions of interior single-relaxation processes. Thus, one can capture the relaxation times and relaxation strengths of N decomposed single-relaxation dispersions to reconstruct the entire multi-relaxation dispersion using the measurements of acoustic velocity at 2N  +  1 frequencies. The reconstructed dispersion spectra are in good agreement with experimental data for various gases and mixtures. The simulations also demonstrate the robustness of our reconstructive method.

Experimental and numerical study of light gas dispersion in a ventilated room

Energy Technology Data Exchange (ETDEWEB)

Gelain, Thomas, E-mail: thomas.gelain@irsn.fr; Prévost, Corinne

2015-11-15

Highlights: • Presentation of many experimental local data for different configurations. • Highlight of the influence of numerical parameters used in the CFD code. • Validation of the CFD code ANSYS CFX on the basis of experimental data. - Abstract: The objective of this study is to validate the ANSYS CFX version 12 computational code on the basis of light gas dispersion tests performed in two ventilated rooms. It follows an initial study on heavy gas dispersion carried out by Ricciardi et al. (2008). First, a study of sensitivity to various numerical parameters allows a set of reference data to be developed and the influence of the numerical scheme of advection to be revealed. Second, two helium (simulating hydrogen) dispersion test grids are simulated for the two rooms studied, and the results of the calculations are compared with experimental results. The very good agreement between these results allows the code and its dataset to be validated for this application. In future, a study with higher levels of helium (on the order of 4% vol at equilibrium) is envisaged in the context of safety analyses related to the hydrogen risk, these levels representing the lower explosive limit (LEL) of hydrogen.

Emission quantification using the tracer gas dispersion method: The influence of instrument, tracer gas species and source simulation

DEFF Research Database (Denmark)

Delre, Antonio; Mønster, Jacob; Samuelsson, Jerker

2018-01-01

The tracer gas dispersion method (TDM) is a remote sensing method used for quantifying fugitive emissions by relying on the controlled release of a tracer gas at the source, combined with concentration measurements of the tracer and target gas plumes. The TDM was tested at a wastewater treatment...... plant for plant-integrated methane emission quantification, using four analytical instruments simultaneously and four different tracer gases. Measurements performed using a combination of an analytical instrument and a tracer gas, with a high ratio between the tracer gas release rate and instrument...... precision (a high release-precision ratio), resulted in well-defined plumes with a high signal-to-noise ratio and a high methane-to-tracer gas correlation factor. Measured methane emission rates differed by up to 18% from the mean value when measurements were performed using seven different instrument...

Modeling blast waves, gas and particles dispersion in urban and hilly ground areas

International Nuclear Information System (INIS)

Hank, S.; Saurel, R.; Le Metayer, O.; Lapebie, E.

2014-01-01

The numerical simulation of shock and blast waves as well as particles dispersion in highly heterogeneous media such as cities, urban places, industrial plants and part of countries is addressed. Examples of phenomena under study are chemical gas products dispersion from damaged vessels, gas dispersion in urban places under explosion conditions, shock wave propagation in urban environment. A three-dimensional simulation multiphase flow code (HI2LO) is developed in this aim. To simplify the consideration of complex geometries, a heterogeneous discrete formulation is developed. When dealing with large scale domains, such as countries, the topography is considered with the help of elevation data. Meteorological conditions are also considered, in particular regarding complex temperature and wind profiles. Heat and mass transfers on sub-scale objects, such as buildings, trees and other obstacles are considered as well. Particles motion is addressed through a new turbulence model involving a single parameter to describe accurately plumes. Validations against experiments in basic situations are presented as well as examples of industrial and environmental computations. (authors)

Correlation between centre offsets and gas velocity dispersion of galaxy clusters in cosmological simulations

Science.gov (United States)

Li, Ming-Hua; Zhu, Weishan; Zhao, Dong

2018-05-01

The gas is the dominant component of baryonic matter in most galaxy groups and clusters. The spatial offsets of gas centre from the halo centre could be an indicator of the dynamical state of cluster. Knowledge of such offsets is important for estimate the uncertainties when using clusters as cosmological probes. In this paper, we study the centre offsets roff between the gas and that of all the matter within halo systems in ΛCDM cosmological hydrodynamic simulations. We focus on two kinds of centre offsets: one is the three-dimensional PB offsets between the gravitational potential minimum of the entire halo and the barycentre of the ICM, and the other is the two-dimensional PX offsets between the potential minimum of the halo and the iterative centroid of the projected synthetic X-ray emission of the halo. Haloes at higher redshifts tend to have larger values of rescaled offsets roff/r200 and larger gas velocity dispersion σ v^gas/σ _{200}. For both types of offsets, we find that the correlation between the rescaled centre offsets roff/r200 and the rescaled 3D gas velocity dispersion, σ _v^gas/σ _{200} can be approximately described by a quadratic function as r_{off}/r_{200} ∝ (σ v^gas/σ _{200} - k_2)2. A Bayesian analysis with MCMC method is employed to estimate the model parameters. Dependence of the correlation relation on redshifts and the gas mass fraction are also investigated.

Gas dispersal potential of bedding as a cause for sudden infant death.

Science.gov (United States)

Sakai, Jun; Kanetake, Jun; Takahashi, Shirushi; Kanawaku, Yoshimasa; Funayama, Masato

2008-09-18

We assessed the gas dispersal potential of bedding articles used by 14 infants diagnosed with sudden unexpected infant death at autopsy. Of these cases, eight exhibited FiCO(2) values greater than 10% within 2.5 min, six of which were found prone and two supine. The results demonstrated that these eight beddings had a high rebreathing potential if they covered the babies' faces. We did not, however, take into account in our model the large tissue stores of CO(2). As some bicarbonate pools will delay or suppress the increase of FiCO(2), the time-FiCO(2) graphs of this study are not true for living infants. This model, however, demonstrated the potential gas dispersal ability of bedding. The higher the FiCO(2) values, the more dangerous the situation for rebreathing infants. In addition, FiO(2) in the potential space around the model's face can be estimated mathematically using FiCO(2) values. The FiO(2) graph pattern for each bedding item corresponded roughly to the inverse of the FiCO(2) time course. The FiO(2) of the above eight cases decreased by 8.5% within 2.5 min. Recent studies using living infants placed prone to sleep reported that some babies exhibited larger decreases in FiO(2) than increases observed in FiCO(2). While the decrease of FiO(2) in our model is still theoretical, CO(2) accumulation and O(2) deprivation are closely related. If a striking O(2) deficiency occurs in a short period, babies can lose consciousness before an arousal response is evoked and all infants could be influenced by the poor gas dispersal of bedding; the main cause of sudden death in infancy would thus be asphyxia. When the bedding is soft, the potential for trapping CO(2) seems to be high; however, it is impossible to assess it by appearance alone. We sought to provide some objective indices for the assessment of respiratory compromise in relation to bedding using our model. When a baby is found unresponsive with his/her face covered with poor gas dispersal bedding, we should

Experimental and Numerical Modelling of CO2 Atmospheric Dispersion in Hazardous Gas Emission Sites.

Science.gov (United States)

Gasparini, A.; sainz Gracia, A. S.; Grandia, F.; Bruno, J.

2015-12-01

Under stable atmospheric conditions and/or in presence of topographic depressions, CO2 concentrations can reach high values resulting in lethal effect to living organisms. The distribution of denser than air gases released from the underground is governed by gravity, turbulence and dispersion. Once emitted, the gas distribution is initially driven by buoyancy and a gas cloud accumulates on the ground (gravitational phase); with time the density gradient becomes less important due to dispersion or mixing and gas distribution is mainly governed by wind and atmospheric turbulence (passive dispersion phase). Natural analogues provide evidences of the impact of CO2 leakage. Dangerous CO2 concentration in atmosphere related to underground emission have been occasionally reported although the conditions favouring the persistence of such a concentration are barely studied.In this work, the dynamics of CO2 in the atmosphere after ground emission is assessed to quantify their potential risk. Two approaches have been followed: (1) direct measurement of air concentration in a natural emission site, where formation of a "CO2 lake" is common and (2) numerical atmospheric modelling. Two sites with different morphology were studied: (a) the Cañada Real site, a flat terrain in the Volcanic Field of Campo de Calatrava (Spain); (b) the Solforata di Pomezia site, a rough terrain in the Alban Hills Volcanic Region (Italy). The comparison between field data and model calculations reveal that numerical dispersion models are capable of predicting the formation of CO2 accumulation over the ground as a consequence of underground gas emission. Therefore, atmospheric modelling could be included as a valuable methodology in the risk assessment of leakage in natural degassing systems and in CCS projects. Conclusions from this work provide clues on whether leakage may be a real risk for humans and under which conditions this risk needs to be included in the risk assessment.

GADEN: A 3D Gas Dispersion Simulator for Mobile Robot Olfaction in Realistic Environments.

Science.gov (United States)

Monroy, Javier; Hernandez-Bennets, Victor; Fan, Han; Lilienthal, Achim; Gonzalez-Jimenez, Javier

2017-06-23

This work presents a simulation framework developed under the widely used Robot Operating System (ROS) to enable the validation of robotics systems and gas sensing algorithms under realistic environments. The framework is rooted in the principles of computational fluid dynamics and filament dispersion theory, modeling wind flow and gas dispersion in 3D real-world scenarios (i.e., accounting for walls, furniture, etc.). Moreover, it integrates the simulation of different environmental sensors, such as metal oxide gas sensors, photo ionization detectors, or anemometers. We illustrate the potential and applicability of the proposed tool by presenting a simulation case in a complex and realistic office-like environment where gas leaks of different chemicals occur simultaneously. Furthermore, we accomplish quantitative and qualitative validation by comparing our simulated results against real-world data recorded inside a wind tunnel where methane was released under different wind flow profiles. Based on these results, we conclude that our simulation framework can provide a good approximation to real world measurements when advective airflows are present in the environment.

A wind-tunnel study on exhaust gas dispersion from road vehicles. Part 1. Velocity and concentration fields behind single vehicles

Energy Technology Data Exchange (ETDEWEB)

Kanda, Isao; Uehara, Kiyoshi; Yamao, Yukio [National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 (Japan); Yoshikawa, Yasuo; Morikawa, Tazuko [Petroleum Energy Center, 4-3-9 Toranomon, Minato-ku, Tokyo, 105-0001 (Japan)

2006-09-15

By a reduced-scale model in a wind tunnel, we investigate the dispersion behavior of exhaust gas from automobiles. Two types of vehicles are considered, a passenger car and a small-size truck. Tracer gas experiments show that the exhaust gas dispersion is enhanced significantly by the vehicle wake compared to the case when the vehicle body is absent. The passenger car and the truck promote dispersion in the horizontal and the vertical direction, respectively. The wake field is analyzed by particle image velocimetry (PIV), and the distribution of the mean and the fluctuation fields is found to conform to the concentration field of the exhaust gas. The buoyancy of the exhaust gas has minor effect except on the vertical spread behind the truck whose wake flow amplifies the vertical displacement generated near the pipe exit. (author)

Derivation of simplified basic equations of gas-liquid two-phase dispersed flow based on two-fluid model

International Nuclear Information System (INIS)

Kataoka, Isao; Tomiyama, Akio

2004-01-01

The simplified and physically reasonable basic equations for the gas-liquid dispersed flow were developed based on some appropriate assumptions and the treatment of dispersed phase as isothermal rigid particles. Based on the local instant formulation of mass, momentum and energy conservation of the dispersed flow, time-averaged equations were obtained assuming that physical quantities in the dispersed phase are uniform. These assumptions are approximately valid when phase change rate and/or chemical reaction rate are not so large at gas-liquid interface and there is no heat generation in within the dispersed phase. Detailed discussions were made on the characteristics of obtained basic equations and physical meanings of terms consisting the basic equations. It is shown that, in the derived averaged momentum equation, the terms of pressure gradient and viscous momentum diffusion do not appear and, in the energy equation, the term of molecular thermal diffusion heat flux does not appear. These characteristics of the derived equations were shown to be very consistent concerning the physical interpretation of the gas-liquid dispersed flow. Furthermore, the obtained basic equations are consistent with experiments for the dispersed flow where most of averaged physical quantities are obtained assuming that the distributions of those are uniform within the dispersed phase. Investigation was made on the problem whether the obtained basic equations are well-posed or ill-posed for the initial value problem. The eigenvalues of the simplified mass and momentum equations are calculated for basic equations obtained here and previous two-fluid basic equations with one pressure model. Well-posedness and ill-posedness are judged whether the eigenvalues are real or imaginary. The result indicated the newly developed basic equations always constitute the well-posed initial value problem while the previous two-fluid basic equations based on one pressure model constitutes ill

A dynamic approach for the impact of a toxic gas dispersion hazard considering human behaviour and dispersion modelling.

Science.gov (United States)

Lovreglio, Ruggiero; Ronchi, Enrico; Maragkos, Georgios; Beji, Tarek; Merci, Bart

2016-11-15

The release of toxic gases due to natural/industrial accidents or terrorist attacks in populated areas can have tragic consequences. To prevent and evaluate the effects of these disasters different approaches and modelling tools have been introduced in the literature. These instruments are valuable tools for risk managers doing risk assessment of threatened areas. Despite the significant improvements in hazard assessment in case of toxic gas dispersion, these analyses do not generally include the impact of human behaviour and people movement during emergencies. This work aims at providing an approach which considers both modelling of gas dispersion and evacuation movement in order to improve the accuracy of risk assessment for disasters involving toxic gases. The approach is applied to a hypothetical scenario including a ship releasing Nitrogen dioxide (NO2) on a crowd attending a music festival. The difference between the results obtained with existing static methods (people do not move) and a dynamic approach (people move away from the danger) which considers people movement with different degrees of sophistication (either a simple linear path or more complex behavioural modelling) is discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

Self Powered Non-Dispersive Infra-Red CO{sub 2} Gas Sensor

Energy Technology Data Exchange (ETDEWEB)

Gibson, D R; MacGregor, C, E-mail: des@gassensing.co.uk [Gas Sensing Solutions Ltd, 60 Grayshill Road, Westfield North Courtyard, Glasgow G68 9HQ (United Kingdom)

2011-08-17

This paper describes a non-dispersive infra-red CO{sub 2} gas sensor, incorporating a mid-infra-red solid state light source/ detector combination, tuned to match the spectral absorption characteristic of CO{sub 2} gas. Injection moulded optics provide low cost manufacture. Continuous operation power consumption is < 3.5mW and pulsed mode with energy per measurement < 6mJ. Self powered operation using a solar cell is demonstrated together with wireless capability. Performance of two path length variants (20mm and 70mm) is described. The sensor shows invariant temperature output characteristic from -25 to 50 deg. C. Accuracy level is typically {+-}3% of reading.

Axial dispersion of gas and solid phases in a gas—solid packed column at trickle flow

NARCIS (Netherlands)

Roes, A.W.M.; van Swaaij, Willibrordus Petrus Maria

1979-01-01

Axial dispersion of gas and solid phases in a gas—solid packed column at trickle flow, a promising new countercurrent operation, was evaluated using residence time distribution (RTD) experiments. The column was packed with dumped Pall rings, the gas phase was air at ambient conditions and the solid

Validation of OpenFoam for heavy gas dispersion applications.

Science.gov (United States)

Mack, A; Spruijt, M P N

2013-11-15

In the present paper heavy gas dispersion calculations were performed with OpenFoam. For a wind tunnel test case, numerical data was validated with experiments. For a full scale numerical experiment, a code to code comparison was performed with numerical results obtained from Fluent. The validation was performed in a gravity driven environment (slope), where the heavy gas induced the turbulence. For the code to code comparison, a hypothetical heavy gas release into a strongly turbulent atmospheric boundary layer including terrain effects was selected. The investigations were performed for SF6 and CO2 as heavy gases applying the standard k-ɛ turbulence model. A strong interaction of the heavy gas with the turbulence is present which results in a strong damping of the turbulence and therefore reduced heavy gas mixing. Especially this interaction, based on the buoyancy effects, was studied in order to ensure that the turbulence-buoyancy coupling is the main driver for the reduced mixing and not the global behaviour of the turbulence modelling. For both test cases, comparisons were performed between OpenFoam and Fluent solutions which were mainly in good agreement with each other. Beside steady state solutions, the time accuracy was investigated. In the low turbulence environment (wind tunnel test) which for both codes (laminar solutions) was in good agreement, also with the experimental data. The turbulent solutions of OpenFoam were in much better agreement with the experimental results than the Fluent solutions. Within the strong turbulence environment, both codes showed an excellent comparability. Copyright © 2013 Elsevier B.V. All rights reserved.

Short-term gas dispersion in idealised urban canopy in street parallel with flow direction

Science.gov (United States)

Chaloupecká, Hana; Jaňour, Zbyněk; Nosek, Štěpán

2016-03-01

Chemical attacks (e.g. Syria 2014-15 chlorine, 2013 sarine or Iraq 2006-7 chlorine) as well as chemical plant disasters (e.g. Spain 2015 nitric oxide, ferric chloride; Texas 2014 methyl mercaptan) threaten mankind. In these crisis situations, gas clouds are released. Dispersion of gas clouds is the issue of interest investigated in this paper. The paper describes wind tunnel experiments of dispersion from ground level point gas source. The source is situated in a model of an idealised urban canopy. The short duration releases of passive contaminant ethane are created by an electromagnetic valve. The gas cloud concentrations are measured in individual places at the height of the human breathing zone within a street parallel with flow direction by Fast-response Ionisation Detector. The simulations of the gas release for each measurement position are repeated many times under the same experimental set up to obtain representative datasets. These datasets are analysed to compute puff characteristics (arrival, leaving time and duration). The results indicate that the mean value of the dimensionless arrival time can be described as a growing linear function of the dimensionless coordinate in the street parallel with flow direction where the gas source is situated. The same might be stated about the dimensionless leaving time as well as the dimensionless duration, however these fits are worse. Utilising a linear function, we might also estimate some other statistical characteristics from datasets than the datasets means (medians, trimeans). The datasets of the dimensionless arrival time, the dimensionless leaving time and the dimensionless duration can be fitted by the generalized extreme value distribution (GEV) in all sampling positions except one.

Analysis of Chlorine Gas Incident Simulation and Dispersion Within a Complex and Populated Urban Area Via Computation Fluid Dynamics

Directory of Open Access Journals (Sweden)

Eslam Kashi

2015-04-01

Full Text Available In some instances, it is inevitable that large amounts of potentially hazardous chemicals like chlorine gas are stored and used in facilities in densely populated areas. In such cases, all safety issues must be carefully considered. To reach this goal, it is important to have accurate information concerning chlorine gas behaviors and how it is dispersed in dense urban areas. Furthermore, maintaining adequate air movement and the ability to purge ambient from potential toxic and dangerous chemicals like chlorine gas could be helpful. These are among the most important actions to be taken toward the improvement of safety in a big metropolis like Tehran. This paper investigates and analyzes chlorine gas leakage scenarios, including its dispersion and natural air ventilation  effects on how it might be geographically spread in a city, using computational  fluid dynamic (CFD. Simulations of possible hazardous events and solutions for preventing or reducing their probability are presented to gain a better insight into the incidents. These investigations are done by considering hypothetical scenarios which consist of chlorine gas leakages from pipelines or storage tanks under different conditions. These CFD simulation results are used to investigate and analyze chlorine gas behaviors, dispersion, distribution, accumulation, and other possible hazards by means of a simplified CAD model of an urban area near a water-treatment facility. Possible hazards as well as some prevention and post incident solutions are also suggested.

Calculations of the mean regional dispersion of a radioactive gas emitted from a continuous source

International Nuclear Information System (INIS)

Persson, C.

1974-10-01

The mean dispersion of a radioactive gas over distances of the order of 1000 kilometers is estimated with the aid of a statistical treatment of computed geostrophic trajectories and simplified vertical diffusion calculations based on the eddy diffusivity theory. (author)

Dispersion of odorants in natural gas distribution networks

Science.gov (United States)

Gross, R.; Fontana, E.; Silva, A.; Quadri, M. B.; Souza, S. M. A. G. U.

2018-03-01

A numerical modeling analysis of a pulse train diffusion, representing an odorant injection in a natural gas pipeline, was carried out and compared with experimental data from a real pipeline. The main purpose of this study is to evaluate how the odorant dispersion occurs along the pipe. Due to technical limitations, the odorant is injected in the line as a pulse and it is important to find out the point in the pipeline where the oscillating concentration of odorant fits into a range of values that meet both the legislation and the interests of customers who may have the quality of their products affected by this oscillation. Since the natural gas pipelines do not have strong streamline curvatures and the flow is always turbulent, it is relatively easy to determine the velocity and concentration fields using the Computational Fluid Dynamics techniques. In this study the RANS (Reynolds Average Navier-Stokes) equations with the k - ɛ turbulence model was used to build the mathematical model. Comparisons of the experimental data and numerical results show a strong agreement for the studied cases. Based on the results, it was possible to know the minimum and maximum values of odorant concentration along the pipelines.

High-resolution modelling of atmospheric dispersion of dense gas using TWODEE-2.1: application to the 1986 Lake Nyos limnic eruption

Science.gov (United States)

Folch, Arnau; Barcons, Jordi; Kozono, Tomofumi; Costa, Antonio

2017-06-01

Atmospheric dispersal of a gas denser than air can threat the environment and surrounding communities if the terrain and meteorological conditions favour its accumulation in topographic depressions, thereby reaching toxic concentration levels. Numerical modelling of atmospheric gas dispersion constitutes a useful tool for gas hazard assessment studies, essential for planning risk mitigation actions. In complex terrains, microscale winds and local orographic features can have a strong influence on the gas cloud behaviour, potentially leading to inaccurate results if not captured by coarser-scale modelling. We introduce a methodology for microscale wind field characterisation based on transfer functions that couple a mesoscale numerical weather prediction model with a microscale computational fluid dynamics (CFD) model for the atmospheric boundary layer. The resulting time-dependent high-resolution microscale wind field is used as input for a shallow-layer gas dispersal model (TWODEE-2.1) to simulate the time evolution of CO2 gas concentration at different heights above the terrain. The strategy is applied to review simulations of the 1986 Lake Nyos event in Cameroon, where a huge CO2 cloud released by a limnic eruption spread downslopes from the lake, suffocating thousands of people and animals across the Nyos and adjacent secondary valleys. Besides several new features introduced in the new version of the gas dispersal code (TWODEE-2.1), we have also implemented a novel impact criterion based on the percentage of human fatalities depending on CO2 concentration and exposure time. New model results are quantitatively validated using the reported percentage of fatalities at several locations. The comparison with previous simulations that assumed coarser-scale steady winds and topography illustrates the importance of high-resolution modelling in complex terrains.

HYDRODYNAMICS OF HIGH-REDSHIFT GALAXY COLLISIONS: FROM GAS-RICH DISKS TO DISPERSION-DOMINATED MERGERS AND COMPACT SPHEROIDS

International Nuclear Information System (INIS)

Bournaud, Frederic; Chapon, Damien; Teyssier, Romain; Powell, Leila C.; Duc, Pierre-Alain; Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Contini, Thierry; Epinat, Benoit; Shapiro, Kristen L.

2011-01-01

Disk galaxies at high redshift (z ∼ 2) are characterized by high fractions of cold gas, strong turbulence, and giant star-forming clumps. Major mergers of disk galaxies at high redshift should then generally involve such turbulent clumpy disks. Merger simulations, however, model the interstellar medium as a stable, homogeneous, and thermally pressurized medium. We present the first merger simulations with high fractions of cold, turbulent, and clumpy gas. We discuss the major new features of these models compared to models where the gas is artificially stabilized and warmed. Gas turbulence, which is already strong in high-redshift disks, is further enhanced in mergers. Some phases are dispersion dominated, with most of the gas kinetic energy in the form of velocity dispersion and very chaotic velocity fields, unlike merger models using a thermally stabilized gas. These mergers can reach very high star formation rates, and have multi-component gas spectra consistent with SubMillimeter Galaxies. Major mergers with high fractions of cold turbulent gas are also characterized by highly dissipative gas collapse to the center of mass, with the stellar component following in a global contraction. The final galaxies are early type with relatively small radii and high Sersic indices, like high-redshift compact spheroids. The mass fraction in a disk component that survives or re-forms after a merger is severely reduced compared to models with stabilized gas, and the formation of a massive disk component would require significant accretion of external baryons afterwards. Mergers thus appear to destroy extended disks even when the gas fraction is high, and this lends further support to smooth infall as the main formation mechanism for massive disk galaxies.

Gas dispersion concentration of trace inorganic contaminants from fuel gas and analysis using head-column field-amplified sample stacking capillary electrophoresis.

Science.gov (United States)

Yang, Jianmin; Li, Hai-Fang; Li, Meilan; Lin, Jin-Ming

2012-08-21

The presence of inorganic elements in fuel gas generally accelerates the corrosion and depletion of materials used in the fuel gas industry, and even leads to serious accidents. For identification of existing trace inorganic contaminants in fuel gas in a portable way, a highly efficient gas-liquid sampling collection system based on gas dispersion concentration is introduced in this work. Using the constructed dual path gas-liquid collection setup, inorganic cations and anions were simultaneously collected from real liquefied petroleum gas (LPG) and analyzed by capillary electrophoresis (CE) with indirect UV absorbance detection. The head-column field-amplified sample stacking technique was applied to improve the detection limits to 2-25 ng mL(-1). The developed collection and analytical methods have successfully determined existing inorganic contaminants in a real LPG sample in the range of 4.59-138.69 μg m(-3). The recoveries of cations and anions with spiked LPG samples were between 83.98 and 105.63%, and the relative standard deviations (RSDs) were less than 7.19%.

Predictive Modelling of Concentration of Dispersed Natural Gas in a Single Room

Directory of Open Access Journals (Sweden)

Abdulfatai JIMOH

2009-07-01

Full Text Available This paper aimed at developing a mathematical model equation to predict the concentration of natural gas in a single room. The model equation was developed by using theoretical method of predictive modelling. The model equation developed is as given in equation 28. The validity of the developed expression was tested through the simulation of experimental results using computer software called MathCAD Professional. Both experimental and simulated results were found to be in close agreement. The statistical analysis carried out through the correlation coefficients for the results of experiment 1, 2, 3 and 4 were found to be 0.9986, 1.0000, 0.9981 and 0.9999 respectively, which imply reasonable close fittings between the experimental and simulated concentrations of dispersed natural gas within the room. Thus, the model equation developed can be considered a good representation of the phenomena that occurred when there is a leakage or accidental release of such gas within the room.

NOx Monitoring in Humid Exhaust Gas Using Non-Dispersive Infrared Spectroscopy

DEFF Research Database (Denmark)

Stolberg-Rohr, Thomine Kirstine

This PhD thesis is concerned with the measurement of NOX in moist exhaust gas onboard ships using non-dispersive infrared (NDIR) spectroscopy. In such a measurement one of the major challenges is spectral interference from water vapour which is present in high concentrations in the exhaust. The Ph......D study investigates a possible solution to this problem, which is to balance out the signal contribution from water vapour by means of carefully designed and manufactured optical bandpass filters. The thesis, presents a thorough theoretical description of the NDIR sensor concept together with simulations...... suggesting that it is possible but challenging to measure NOX in moist exhaust gas using NDIR. The characteristics of optical filters tend to change with temperature, and since this compromises the water signal balancing, much of the work presented in the thesis is devoted to the design of optical bandpass...

Hanford gas dispersion analysis

International Nuclear Information System (INIS)

Fujita, R.K.; Travis, J.R.

1994-01-01

An analysis was performed to verify the design of a waste gas exhauster for use in support of rotary core sampling activities at the Westinghouse Hanford Waste Tank Farm. The exhauster was designed to remove waste gases from waste storage tanks during the rotary core drilling process of the solid materials in the tank. Some of the waste gases potentially are very hazardous and must be monitored during the exhauster's operation. If the toxic gas concentrations in specific areas near the exhauster exceed minimum Threshold Limit Values (TLVs), personnel must be excluded from the area. The exhauster stack height is of interest because an increase in stack height will alter the gas concentrations at the critical locations. The exhaust stack is currently ∼4.6 m (15 ft) high. An equipment operator will be located within a 6.1 m (20 ft) radius of the exhaust stack, and his/her head will be at an elevation 3.7 m (12 ft) above ground level (AGL). Therefore, the maximum exhaust gas concentrations at this location must be below the TLV for the toxic gases. Also, the gas concentrations must be within the TLV at a 61 m (200 ft) radius from the stack. If the calculated gas concentrations are above the TLV, where the operator is working below the stack at the 61 m (200 ft) radius location, the stack height may need to be increased

Development of a code to simulate dispersion of atmospheric released tritium gas in the environmental media and to evaluate doses. TRIDOSE

International Nuclear Information System (INIS)

Murata, Mikio; Noguchi, Hiroshi; Yokoyama, Sumi

2000-11-01

A computer code (TRIDOSE) was developed to assess the environmental impact of atmospheric released tritium gas (T 2 ) from nuclear fusion related facilities. The TRIDOSE simulates dispersion of T 2 and resultant HTO in the atmosphere, land, plant, water and foods in the environment, and evaluates contamination concentrations in the media and exposure doses. A part of the mathematical models in TRIDOSE were verified by comparison of the calculation with the results of the short range (400 m) dispersion experiment of HT gas performed in Canada postulating a short-time (30 minutes) accidental release. (author)

Source strength and dispersion of CO2 releases from high-pressure pipelines: CFD model using real gas equation of state

International Nuclear Information System (INIS)

Liu, Xiong; Godbole, Ajit; Lu, Cheng; Michal, Guillaume; Venton, Philip

2014-01-01

Highlights: • Validated CFD models for decompression and dispersion of CO 2 releases from pipelines. • Incorporation of real gas EOS into CFD code for source strength estimation. • Demonstration of better performance of SST k–ω turbulence model for jet flow. • Demonstration of better performance of real gas EOS compared to ideal gas EOS. • Demonstration of superiority of CFD models over a commercial risk assessment package. - Abstract: Transportation of CO 2 in high-pressure pipelines forms a crucial link in the ever-increasing application of Carbon Capture and Storage (CCS) technologies. An unplanned release of CO 2 from a pipeline presents a risk to human and animal populations and the environment. Therefore it is very important to develop a deeper understanding of the atmospheric dispersion of CO 2 before the deployment of CO 2 pipelines, to allow the appropriate safety precautions to be taken. This paper presents a two-stage Computational Fluid Dynamics (CFD) study developed (1) to estimate the source strength, and (2) to simulate the subsequent dispersion of CO 2 in the atmosphere, using the source strength estimated in stage (1). The Peng–Robinson (PR) EOS was incorporated into the CFD code. This enabled accurate modelling of the CO 2 jet to achieve more precise source strength estimates. The two-stage simulation approach also resulted in a reduction in the overall computing time. The CFD models were validated against experimental results from the British Petroleum (BP) CO 2 dispersion trials, and also against results produced by the risk management package Phast. Compared with the measurements, the CFD simulation results showed good agreement in both source strength and dispersion profile predictions. Furthermore, the effect of release direction on the dispersion was studied. The presented research provides a viable method for the assessment of risks associated with CCS

Development of a code to simulate dispersion of atmospheric released tritium gas in the environmental media and to evaluate doses. TRIDOSE

Energy Technology Data Exchange (ETDEWEB)

Murata, Mikio [Nuclear Engineering Co., Ltd., Hitachi, Ibaraki (Japan); Noguchi, Hiroshi; Yokoyama, Sumi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2000-11-01

A computer code (TRIDOSE) was developed to assess the environmental impact of atmospheric released tritium gas (T{sub 2}) from nuclear fusion related facilities. The TRIDOSE simulates dispersion of T{sub 2} and resultant HTO in the atmosphere, land, plant, water and foods in the environment, and evaluates contamination concentrations in the media and exposure doses. A part of the mathematical models in TRIDOSE were verified by comparison of the calculation with the results of the short range (400 m) dispersion experiment of HT gas performed in Canada postulating a short-time (30 minutes) accidental release. (author)

Computational sensitivity study of spray dispersion and mixing on the fuel properties in a gas turbine combustor

Energy Technology Data Exchange (ETDEWEB)

Grosshans, Holger; Szász, Robert-Zoltán [Division of Fluid Mechanics, Lund University (Sweden); Cao, Le [Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing (China); Fuchs, Laszlo, E-mail: holger.grosshans@uclouvain.be [Department of Mechanics, KTH, Stockholm (Sweden)

2017-04-15

A swirl stabilized gas turbine burner has been simulated in order to assess the effects of the fuel properties on spray dispersion and fuel–air mixing. The properties under consideration include fuel surface tension, viscosity and density. The turbulence of the gas phase is modeled applying the methodology of large eddy simulation whereas the dispersed liquid phase is described by Lagrangian particle tracking. The exchange of mass, momentum and energy between the two phases is accounted for by two-way coupling. Bag and stripping breakup regimes are considered for secondary droplet breakup, using the Reitz–Diwakar and the Taylor analogy breakup models. Moreover, a model for droplet evaporation is included. The results reveal a high sensitivity of the spray structure to variations of all investigated parameters. In particular, a decrease in the surface tension or the fuel viscosity, or an increase in the fuel density, lead to less stable liquid structures. As a consequence, smaller droplets are generated and the overall spray surface area increases, leading to faster evaporation and mixing. Furthermore, with the trajectories of the small droplets being strongly influenced by aerodynamic forces (and less by their own inertia), the spray is more affected by the turbulent structures of the gaseous phase and the spray dispersion is enhanced. (paper)

Determination of Levetiracetam in Human Plasma by Dispersive Liquid-Liquid Microextraction Followed by Gas Chromatography-Mass Spectrometry

Science.gov (United States)

2016-01-01

Levetiracetam (LEV) is an antiepileptic drug that is clinically effective in generalized and partial epilepsy syndromes. The use of this drug has been increasing in clinical practice and intra- or -interindividual variability has been exhibited for special population. For this reason, bioanalytical methods are required for drug monitoring in biological matrices. So this work presents a dispersive liquid-liquid microextraction method followed by gas chromatography-mass spectrometry (DLLME-GC-MS) for LEV quantification in human plasma. However, due to the matrix complexity a previous purification step is required. Unlike other pretreatment techniques presented in the literature, for the first time, a procedure employing ultrafiltration tubes Amicon® (10 kDa porous size) without organic solvent consumption was developed. GC-MS analyses were carried out using a linear temperature program, capillary fused silica column, and helium as the carrier gas. DLLME optimized parameters were type and volume of extraction and dispersing solvents, salt addition, and vortex agitation time. Under chosen parameters (extraction solvent: chloroform, 130 μL; dispersing solvent: isopropyl alcohol, 400 μL; no salt addition and no vortex agitation time), the method was completely validated and all parameters were in agreement with the literature recommendations. LEV was quantified in patient's plasma sample using less than 550 μL of organic solvent. PMID:27830105

Determination of Levetiracetam in Human Plasma by Dispersive Liquid-Liquid Microextraction Followed by Gas Chromatography-Mass Spectrometry

Directory of Open Access Journals (Sweden)

Greyce Kelly Steinhorst Alcantara

2016-01-01

Full Text Available Levetiracetam (LEV is an antiepileptic drug that is clinically effective in generalized and partial epilepsy syndromes. The use of this drug has been increasing in clinical practice and intra- or -interindividual variability has been exhibited for special population. For this reason, bioanalytical methods are required for drug monitoring in biological matrices. So this work presents a dispersive liquid-liquid microextraction method followed by gas chromatography-mass spectrometry (DLLME-GC-MS for LEV quantification in human plasma. However, due to the matrix complexity a previous purification step is required. Unlike other pretreatment techniques presented in the literature, for the first time, a procedure employing ultrafiltration tubes Amicon® (10 kDa porous size without organic solvent consumption was developed. GC-MS analyses were carried out using a linear temperature program, capillary fused silica column, and helium as the carrier gas. DLLME optimized parameters were type and volume of extraction and dispersing solvents, salt addition, and vortex agitation time. Under chosen parameters (extraction solvent: chloroform, 130 μL; dispersing solvent: isopropyl alcohol, 400 μL; no salt addition and no vortex agitation time, the method was completely validated and all parameters were in agreement with the literature recommendations. LEV was quantified in patient’s plasma sample using less than 550 μL of organic solvent.

Modeling of corium dispersion in DCH accidents

International Nuclear Information System (INIS)

Wu, Q.

1996-01-01

A model that governs the dispersion process in the direct containment heating (DCH) reactor accident scenario is developed by a stepwise approach. In this model, the whole transient is subdivided into four phases with an isothermal assumption. These are the liquid and gas discharge, the liquid film flow in the cavity before gas blowdown, the liquid and gas flow in the cavity with droplet entrainment, and the liquid transport and re-entrainment in the subcompartment. In each step, the dominant driving mechanisms are identified to construct the governing equations. By combining all the steps together, the corium dispersion information is obtained in detail. The key parameters are predicted quantitatively. These include the fraction of liquid that flows out of the cavity before gas blowdown, the dispersion fraction and the mean droplet diameter in the cavity, the cavity pressure rise due to the liquid friction force, and the dispersion fractions in the containment via different paths. Compared with the data of the 1:10 scale experiments carried out at Purdue University, fairly good agreement is obtained. A stand-alone prediction of the corium dispersion under prototypic Zion reactor conditions is carried out by assuming an isothermal process without chemical reactions. (orig.)

Atmospheric dispersion prediction and source estimation of hazardous gas using artificial neural network, particle swarm optimization and expectation maximization

Science.gov (United States)

Qiu, Sihang; Chen, Bin; Wang, Rongxiao; Zhu, Zhengqiu; Wang, Yuan; Qiu, Xiaogang

2018-04-01

Hazardous gas leak accident has posed a potential threat to human beings. Predicting atmospheric dispersion and estimating its source become increasingly important in emergency management. Current dispersion prediction and source estimation models cannot satisfy the requirement of emergency management because they are not equipped with high efficiency and accuracy at the same time. In this paper, we develop a fast and accurate dispersion prediction and source estimation method based on artificial neural network (ANN), particle swarm optimization (PSO) and expectation maximization (EM). The novel method uses a large amount of pre-determined scenarios to train the ANN for dispersion prediction, so that the ANN can predict concentration distribution accurately and efficiently. PSO and EM are applied for estimating the source parameters, which can effectively accelerate the process of convergence. The method is verified by the Indianapolis field study with a SF6 release source. The results demonstrate the effectiveness of the method.

Effect of palladium dispersion on the capture of toxic components from fuel gas by palladium-alumina sorbents

Energy Technology Data Exchange (ETDEWEB)

John P. Baltrus; Evan J. Granite; Erik C. Rupp; Dennis C. Stanko; Bret Howard; Henry W. Pennline [US DOE National Energy Technology Laboratory, Pittsburgh, PA (United States)

2011-05-15

The dispersion and location of Pd in alumina-supported sorbents prepared by different methods was found to influence the performance of the sorbents in the removal of mercury, arsine, and hydrogen selenide from a simulated fuel gas. When Pd is well dispersed in the pores of the support, contact interaction with the support is maximized, Pd is less susceptible to poisoning by sulfur, and the sorbent has better long-term activity for adsorption of arsine and hydrogen selenide, but poorer adsorption capacity for Hg. As the contact interaction between Pd and the support is lessened the Pd becomes more susceptible to poisoning by sulfur, resulting in higher capacity for Hg, but poorer long-term performance for adsorption of arsenic and selenium. 18 refs., 3 figs., 4 tabs.

The influence of the dispersion corrections on the performance of DFT method in modeling HNgY noble gas molecules and their complexes

Science.gov (United States)

Cukras, Janusz; Sadlej, Joanna

2018-01-01

The letter reports a comparative assessment of the usefulness of the two different Grimme's corrections for evaluating dispersion interaction (DFT-D3 and DFT-D3BJ) for the representative molecules of the family of noble-gas hydrides HXeY and their complexes with the HZ molecules, where Y and Z are F/Cl/OH/SH. with special regard to the dispersion term calculated by means of the symmetry-adapted perturbation theory (at the SAPT0 level). The results indicate that despite differences in the total interactions energy (DFT + corrections) versus SAPT0 results, the sequence of contributions of the individual dispersion terms is still maintained. Both dispersion corrections perform similarly and they improve the results suggesting that it is worthwhile to include them in calculations.

Effect of Additional Structure on Effective Stack Height of Gas Dispersion in Atmosphere

Directory of Open Access Journals (Sweden)

Takenobu Michioka

2016-03-01

Full Text Available Wind-tunnel experiments were conducted to evaluate the effect of additional structure (building, sea wall and banking on the effective stack height, which is usually used in safety analyses of nuclear power facilities in Japan. The effective stack heights were estimated with and without the additional structure in addition to the reactor building while varying several conditions such as the source height, the height of additional structure and the distance between the source position and the additional structure. When the source height is equivalent to the reactor building height, the additional structure enhances both the vertical and horizontal gas dispersion widths and decreases the ground gas concentration, and it means that the additional structure does not decrease the effective stack height. When the source height is larger than the reactor height, the additional structures might affect the effective stack height. As the distance between the source and the additional structure decreases, or as the height of the additional structure increases, the structure has a larger effect on the effective stack height.

A new optical rotation dispersion formula

International Nuclear Information System (INIS)

Kimel, I.

1981-12-01

A new dispersion formula for the rotatory power is obtained in the framework of Kubo forlalism for transport coefficients. Unlike the well known Rosenfeld-Condon dispersion law, this formula is consistent with the free electron gas asymptotic behavior. (Author) [pt

Quenching of Particle-Gas Combustible Mixtures Using Electric Particulate Suspension (EPS) and Dispersion Methods

Science.gov (United States)

Colver, Gerald M.; Goroshin, Samuel; Lee, John H. S.

2001-01-01

A cooperative study is being carried out between Iowa State University and McGill University. The new study concerns wall and particle quenching effects in particle-gas mixtures. The primary objective is to measure and interpret flame quenching distances, flammability limits, and burning velocities in particulate suspensions. A secondary objective is to measure particle slip velocities and particle velocity distribution as these influence flame propagation. Two suspension techniques will be utilized and compared: (1) electric particle suspension/EPS; and (2) flow dispersion. Microgravity tests will permit testing of larger particles and higher and more uniform dust concentrations than is possible in normal gravity.

The mechanism of strong electric field effect on the dispersed media in the rarefied gas

International Nuclear Information System (INIS)

Gagarin, A.G.; Savchenko, Y.N.; Vigdonchik, V.H.

1985-01-01

This paper discusses two approaches to the description of the flow of fluids and gases, that is, a phenomenological method and a molecular-kinetic method. Four dispersed admixtures are described using the model of solid spheres as for molecules and a system of aerodynamic equations is obtained. In this system interactions between gas molecules and admixtures are taken into consideration already in the zero approximation. The paper is also concerned with the experimental study of the motion of dispersed particles in corona discharge which is a typical example of a strong nonuniform electric field with a volume discharge. From the comparison of experimental and calculated paths it was found that the particles move five to seven times faster than they would have done under the action of the Coulomb force alone at a real amount of charge of the particle. The result of comparison also shows that their motion primarily depends on the jet flow of electric wind

Modelling of Dispersed Gas-Liquid Flow using LBGK and LPT Approach

Science.gov (United States)

Agarwal, Alankar; Prakash, Akshay; Ravindra, B.

2017-11-01

The dynamics of gas bubbles play a significant, if not crucial, role in a large variety of industrial process that involves using reactors. Many of these processes are still not well understood in terms of optimal scale-up strategies.An accurate modeling of bubbles and bubble swarms become important for high fidelity bioreactor simulations. This study is a part of the development of robust bubble fluid interaction modules for simulation of industrial-scale reactors. The work presents the simulation of a single bubble rising in a quiescent water tank using current models presented in the literature for bubble-fluid interaction. In this multiphase benchmark problem, the continuous phase (water) is discretized using the Lattice Bhatnagar-Gross and Krook (LBGK) model of Lattice Boltzmann Method (LBM), while the dispersed gas phase (i.e. air-bubble) modeled with the Lagrangian particle tracking (LPT) approach. The cheap clipped fourth order polynomial function is used to model the interaction between two phases. The model is validated by comparing the simulation results for terminal velocity of a bubble at varying bubble diameter and the influence of bubble motion in liquid velocity with the theoretical and previously available experimental data. This work is supported by the ``Centre for Development of Advanced Computing (C-DAC), Pune'' by providing the advanced computational facility in PARAM Yuva-II.

The effect of a micro bubble dispersed gas phase on hydrogen isotope transport in liquid metals under nuclear irradiation

Energy Technology Data Exchange (ETDEWEB)

Fradera, J., E-mail: jfradera@ubu.es; Cuesta-López, S., E-mail: scuesta@ubu.es

2013-12-15

The present work intend to be a first step towards the understanding and quantification of the hydrogen isotope complex phenomena in liquid metals for nuclear technology. Liquid metals under nuclear irradiation in, e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles. Other liquid metal systems of a nuclear reactor involve hydrogen isotope absorption processes, e.g., tritium extraction system. Hence, hydrogen isotope absorption into gas bubbles modelling and control may have a capital importance regarding design, operation and safety. Here general models for hydrogen isotopes transport in liquid metal and absorption into gas phase, that do not depend on the mass transfer limiting regime, are exposed and implemented in OpenFOAM® CFD tool for 0D–3D simulations. Results for a 0D case show the impact of a He dispersed phase of nano bubbles on hydrogen isotopes inventory at different temperatures as well as the inventory evolution during a He nucleation event. In addition, 1D and 2D axisymmetric cases are exposed showing the effect of a He dispersed gas phase on hydrogen isotope permeation through a lithium lead eutectic alloy and the effect of vortical structures on hydrogen isotope transport at a backward facing step. Exposed results give a valuable insight on current nuclear technology regarding the importance of controlling hydrogen isotope transport and its interactions with nucleation event through gas absorption processes.

Coupling of WRF and Building-resolved CFD Simulations for Greenhouse Gas Transport and Dispersion

Science.gov (United States)

Prasad, K.; Hu, H.; McDermott, R.; Lopez-Coto, I.; Davis, K. J.; Whetstone, J. R.; Lauvaux, T.

2014-12-01

The Indianapolis Flux Experiment (INFLUX) aims to use a top-down inversion methodology to quantify sources of Greenhouse Gas (GHG) emissions over an urban domain with high spatial and temporal resolution. Atmospheric transport of tracer gases from an emission source to a tower mounted receptor are usually conducted using the Weather Research and Forecasting (WRF) model. WRF is used extensively in the atmospheric community to simulate mesoscale atmospheric transport. For such simulations, WRF employs a parameterized turbulence model and does not resolve the fine scale dynamics that are generated by the flow around buildings and communities that are part of a large city. Since the model domain includes the city of Indianapolis, much of the flow of interest is over an urban topography. The NIST Fire Dynamics Simulator (FDS) is a computational fluid dynamics model to perform large eddy simulations of flow around buildings, but it has not been nested within a larger-scale atmospheric transport model such as WRF. FDS has the potential to evaluate the impact of complex urban topography on near-field dispersion and mixing that cannot be simulated with a mesoscale atmospheric model, and which may be important to determining urban GHG emissions using atmospheric measurements. A methodology has been developed to run FDS as a sub-grid scale model within a WRF simulation. The coupling is based on nudging the FDS flow field towards the one computed by WRF, and is currently limited to one way coupling performed in an off-line mode. Using the coupled WRF / FDS model, NIST will investigate the effects of the urban canopy at horizontal resolutions of 2-10 m. The coupled WRF-FDS simulations will be used to calculate the dispersion of tracer gases in an urban domain and to evaluate the upwind areas that contribute to tower observations, referred to in the inversion community as influence functions. Predicted mixing ratios will be compared with tower measurements and WRF simulations

Conditions for the formation and atmospheric dispersion of a toxic, heavy gas layer during thermal metamorphism of coal and evaporite deposits by sill intrusion

Science.gov (United States)

Storey, Michael; Hankin, Robin K. S.

2010-05-01

There is compelling evidence for massive discharge of volatiles, including toxic species, into the atmosphere at the end of the Permian. It has been argued that most of the gases were produced during thermal metamorphism of coal and evaporite deposits in the East Siberia Tunguska basin following sill intrusion (Retallack and Jahren, 2008; Svensen et al., 2009). The release of the volatiles has been proposed as a major cause of environmental and extinction events at the end of the Permian, with venting of carbon gases and halocarbons to the atmosphere leading to global warming and atmospheric ozone depletion (Svensen et al., 2009) Here we consider the conditions required for the formation and dispersion of toxic, heavier than air, gas plumes, made up of a mixture of CO2, CH4, H2S and SO2 and formed during the thermal metamorphism of C- and S- rich sediments. Dispersion models and density considerations within a range of CO2/CH4 ratios and volatile fluxes and temperatures, for gas discharge by both seepage and from vents, allow the possibility that following sill emplacement much of the vast East Siberia Tunguska basin was - at least intermittently - covered by a heavy, toxic gas layer that was unfavorable for life. Dispersion scenarios for a heavy gas layer beyond the Siberian region during end-Permian times will be presented. REFERENCES G. J. Retallack and A. H. Jahren, Methane release from igneous intrusion of coal during Late Permian extinction events, Journal of Geology, volume 116, 1-20, 2008 H. Svensen et al., Siberian gas venting and the end-Permian environmental crisis, Earth and Planetary Science Letters, volume 277, 490-500, 2009

Determination of organophosphorus pesticides by dispersive liquid-liquid micro extraction coupled with gas chromatography-electron capture detection

International Nuclear Information System (INIS)

Mohd Marsin Sanagi; Siti Umairah Mokhtar; Mazidatul Akmam Miskam; Wan Aini Wan Ibrahim

2011-01-01

A simple, rapid and sensitive method termed as dispersive liquid-liquid micro extraction (DLLME) combined with gas chromatography-electron capture detector (GC-ECD) was developed for the determination of selected organophosphorus pesticides (OPPs) namely chloropyrifos, dimethoate and diazinon in water sample. In this method, a mixture of carbon disulfide, CS 2 (extraction solvent) and methanol (disperser solvent) was rapidly injected using syringe into the 5.00 mL water sample to form a cloudy solution where the OPPs were extracted into the fine droplets of extraction solvent. Upon centrifugation for 3 min at 3500 rpm, the fine droplets were sedimented at the bottom of the centrifuge tube. Sedimented phase (1 μL) was injected into the GC-ECD for separation and determination of OPPs. Important extraction parameters, such as type of disperser solvent, volume of extraction solvent and volume of disperser solvent were investigated. The optimized conditions for DLLME of the selected OPPs were methanol as disperser solvent, 30 μL of extraction solvent (CS 2 ) and 1.0 mL of disperser solvent (methanol). Under the optimum extraction conditions, the method showed good linearity in the range of 0.1 to 1.0 μg/ mL with correlation coefficient (r 2 ), in the range of 0.9976 to 0.9994 and low limits of detection (LOD) between 0.047 and 0.201 μg/ mL. The proposed method provided acceptable recoveries (72.67- 144 %) with good RSDs ranging from 2.74 % to 7.48 %. This method was successfully applied to the determination of OPPs in water samples obtained from a golf course and chloropyrifos and diazinon were detected at concentration 0.18 μg/ mL and 0.07 μg/ mL, respectively. (author)

Comparison of Dorris-Gray and Schultz methods for the calculation of surface dispersive free energy by inverse gas chromatography.

Science.gov (United States)

Shi, Baoli; Wang, Yue; Jia, Lina

2011-02-11

Inverse gas chromatography (IGC) is an important technique for the characterization of surface properties of solid materials. A standard method of surface characterization is that the surface dispersive free energy of the solid stationary phase is firstly determined by using a series of linear alkane liquids as molecular probes, and then the acid-base parameters are calculated from the dispersive parameters. However, for the calculation of surface dispersive free energy, generally, two different methods are used, which are Dorris-Gray method and Schultz method. In this paper, the results calculated from Dorris-Gray method and Schultz method are compared through calculating their ratio with their basic equations and parameters. It can be concluded that the dispersive parameters calculated with Dorris-Gray method will always be larger than the data calculated with Schultz method. When the measuring temperature increases, the ratio increases large. Compared with the parameters in solvents handbook, it seems that the traditional surface free energy parameters of n-alkanes listed in the papers using Schultz method are not enough accurate, which can be proved with a published IGC experimental result. © 2010 Elsevier B.V. All rights reserved.

Determination of Organophosphorus Pesticides in Soil by Dispersive Liquid–Liquid Microextraction and Gas Chromatography

Science.gov (United States)

Yang, Zhonghua; Liu, Yu; Liu, Donghui; Zhou, Zhiqiang

2012-01-01

In this article, a rapid and sensitive sample pretreatment technique for the determination of organophosphorus pesticides (OPPs) in soil samples is developed by using dispersive liquid–liquid microextraction (DLLME) combined with gas chromatography–flame photometric detection. Experimental conditions, including the kind of extraction and disperser solvent and their volumes, the extraction time, and the salt addition, are investigated, and the following experiment factors are used: 20 µL chlorobenzene as the extraction solvent; 1.0 mL acetonitrile as the disperser solvent; no addition of salt; and an extraction time of 1 min. Under the optimum conditions, the linearities for the three target OPPs (ethoprophos, chlorpyriphos, and profenofos) are obtained by five points in the concentration range of 2.5–1500 µg/kg, and three replicates are used for each point. Correlation coefficients vary from 0.9987 to 0.9997. The repeatability is tested by spiking soil samples at a concentration level of 5.0 µg/kg. The relative standard deviation (n = 3) varied between 2.0% and 6.6%. The limits of detection, based on a signal-to-noise ratio (S/N) of 3, range from 200 to 500 pg/g. This method is applied to the analysis of the spiked samples S1, S2, and S3, which are collected from the China Agriculture University's orchard, lawn, and garden, respectively. The recoveries for each target analyte are in the range between 87.9% and 108.0%, 87.4% and 108.0%, and 86.7% and 107.2%, respectively. PMID:22291051

Building-Resolved CFD Simulations for Greenhouse Gas Transport and Dispersion over Washington DC / Baltimore

Science.gov (United States)

Prasad, K.; Lopez-Coto, I.; Ghosh, S.; Mueller, K.; Whetstone, J. R.

2015-12-01

The North-East Corridor project aims to use a top-down inversion methodology to quantify sources of Greenhouse Gas (GHG) emissions over urban domains such as Washington DC / Baltimore with high spatial and temporal resolution. Atmospheric transport of tracer gases from an emission source to a tower mounted receptor are usually conducted using the Weather Research and Forecasting (WRF) model. For such simulations, WRF employs a parameterized turbulence model and does not resolve the fine scale dynamics generated by the flow around buildings and communities comprising a large city. The NIST Fire Dynamics Simulator (FDS) is a computational fluid dynamics model that utilizes large eddy simulation methods to model flow around buildings at length scales much smaller than is practical with WRF. FDS has the potential to evaluate the impact of complex urban topography on near-field dispersion and mixing difficult to simulate with a mesoscale atmospheric model. Such capabilities may be important in determining urban GHG emissions using atmospheric measurements. A methodology has been developed to run FDS as a sub-grid scale model within a WRF simulation. The coupling is based on nudging the FDS flow field towards that computed by WRF, and is currently limited to one way coupling performed in an off-line mode. Using the coupled WRF / FDS model, NIST will investigate the effects of the urban canopy at horizontal resolutions of 10-20 m in a domain of 12 x 12 km. The coupled WRF-FDS simulations will be used to calculate the dispersion of tracer gases in the North-East Corridor and to evaluate the upwind areas that contribute to tower observations, referred to in the inversion community as influence functions. Results of this study will provide guidance regarding the importance of explicit simulations of urban atmospheric turbulence in obtaining accurate estimates of greenhouse gas emissions and transport.

Gas dispersal potential of infant bedding of sudden death cases. (I): CO2 accumulation around the face of infant mannequin model.

Science.gov (United States)

Sakai, Jun; Takahashi, Shirushi; Funayama, Masato

2009-04-01

We assessed CO(2) gas dispersal potential of bedding that had actually been used by 26 infants diagnosed with sudden unexpected infant death using a baby mannequin model. The age of victims ranged from 1 to 12 months. In some cases, the parents alleged that the infant faces were not covered with bedding when they were found. The parent's memories, however, may not have been accurate; therefore, we examined the potential for gas dispersal based on the supposition that the bedding had covered their faces. The mannequin was connected with a respirator set on the tidal volume and respiratory rates matched with the baby's age. Before measuring, CO(2) flow was regulated in 5%+/-0.1% of end-tidal PCO(2). After the model was placed on each bedding condition, measurements were performed at least five times under each respiratory condition. Four cases showed a plateau of FiCO(2) bedding. Especially, the latter seven bedding could have high rebreathing potential if they covered the infant's faces and the probability of environmental asphyxia should be considered.

Strongly coupled dispersed two-phase flows; Ecoulements diphasiques disperses fortement couples

Energy Technology Data Exchange (ETDEWEB)

Zun, I.; Lance, M.; Ekiel-Jezewska, M.L.; Petrosyan, A.; Lecoq, N.; Anthore, R.; Bostel, F.; Feuillebois, F.; Nott, P.; Zenit, R.; Hunt, M.L.; Brennen, C.E.; Campbell, C.S.; Tong, P.; Lei, X.; Ackerson, B.J.; Asmolov, E.S.; Abade, G.; da Cunha, F.R.; Lhuillier, D.; Cartellier, A.; Ruzicka, M.C.; Drahos, J.; Thomas, N.H.; Talini, L.; Leblond, J.; Leshansky, A.M.; Lavrenteva, O.M.; Nir, A.; Teshukov, V.; Risso, F.; Ellinsen, K.; Crispel, S.; Dahlkild, A.; Vynnycky, M.; Davila, J.; Matas, J.P.; Guazelli, L.; Morris, J.; Ooms, G.; Poelma, C.; van Wijngaarden, L.; de Vries, A.; Elghobashi, S.; Huilier, D.; Peirano, E.; Minier, J.P.; Gavrilyuk, S.; Saurel, R.; Kashinsky, O.; Randin, V.; Colin, C.; Larue de Tournemine, A.; Roig, V.; Suzanne, C.; Bounhoure, C.; Brunet, Y.; Tanaka, A.T.; Noma, K.; Tsuji, Y.; Pascal-Ribot, S.; Le Gall, F.; Aliseda, A.; Hainaux, F.; Lasheras, J.; Didwania, A.; Costa, A.; Vallerin, W.; Mudde, R.F.; Van Den Akker, H.E.A.; Jaumouillie, P.; Larrarte, F.; Burgisser, A.; Bergantz, G.; Necker, F.; Hartel, C.; Kleiser, L.; Meiburg, E.; Michallet, H.; Mory, M.; Hutter, M.; Markov, A.A.; Dumoulin, F.X.; Suard, S.; Borghi, R.; Hong, M.; Hopfinger, E.; Laforgia, A.; Lawrence, C.J.; Hewitt, G.F.; Osiptsov, A.N.; Tsirkunov, Yu. M.; Volkov, A.N.

2003-07-01

-phase flow, current distribution and mass transfer along a vertical gas evolving electrode; a two-way coupled model for dilute multiphase flows. Topic 3: turbulence modulation by particles, droplets or bubbles in dense systems: influence of particles on the transition to turbulence in pipe flow; comparison between a point particle model and a finite-diameter-model for the particle turbulence interaction in a suspension; the effect on turbulence by bubbles rising through it under buoyancy; the physical mechanisms of modifying the structure of turbulent homogeneous shear flows by dispersed particles; influence of hydrodynamic interactions between particles on the turbulent flow in a suspension; review of relationships between Lagrangian and Eulerian scales; a two-point PDF for modelling turbulent dispersed two-phase flows and derivation of a two field model; mathematical and numerical modeling of two-phase compressible flows with micro-inertia. Topic 4: collective effects in dispersed two-phase flows clustering and phase distribution: hydrodynamic structure of downward bubbly flow; influence of gravity on the dynamics of a turbulent bubbly pipe flow; experimental study of two-phase flows; particle clusters formed in dispersed gas-solid flows: simulations and experiments; experimental study of the turbulence in bubbly flows at high void fraction; first step in the study of the correlation between air/water flow fluctuations and random buffering forces; clustering and settling velocity of micro-droplets in a grid turbulence. Topic 5: large scale instabilities and gravity driven dispersed flows: new 'non-isothermal' linear instability modes in fluidized beds and bubbly flows; large scale instability in a confined buoyant shear layer; convective instability in uniform dispersed layers; structures in gravity driven bubbly flows; effects of concentration profiles on velocity profiles in sewer; pyroclastic density currents viewed as mammoth scale two-phase flows; mixing and

Short communication: measurements of methane emissions from feed samples in filter bags or dispersed in the medium in an in vitro gas production system.

Science.gov (United States)

Ramin, M; Krizsan, S J; Jančík, F; Huhtanen, P

2013-07-01

The objective of this study was to compare methane (CH4) emissions from different feeds when incubated within filter bags for in vitro analysis or directly dispersed in the medium in an automated gas in vitro system. Four different concentrates and 4 forages were used in this study. Two lactating Swedish Red cows were used for the collection of rumen fluid. Feed samples were milled to pass a 1.0-mm screen. Aliquots (0.5 g) of samples were weighed directly in the bottles or within the F 0285 filter bags that were placed in the bottles. Gas samples were taken during 24 and 48 h of incubation, and CH4 concentration was determined. The data were analyzed using a general linear model. Feeds differed significantly in CH4 emission both at 24 and at 48 h of incubation. The interaction between feed and method on methane emission in vitro was significant, indicating that the ranking of feeds was not consistent between the methods. Generally, greater amounts of CH4 were emitted from samples directly dispersed in the medium compared with those incubated within the filter bags, which could be a result of lower microbial activity within the filter bags. The ratio of CH4 to total gas was greater when the feeds were incubated within bags compared with samples directly dispersed in the medium. Incubating samples in filter bags during 48 h of incubation cannot be recommended for determination of CH4 emission of feeds in vitro. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Large eddy simulation of pollutant gas dispersion with buoyancy ejected from building into an urban street canyon.

Science.gov (United States)

Hu, L H; Xu, Y; Zhu, W; Wu, L; Tang, F; Lu, K H

2011-09-15

The dispersion of buoyancy driven smoke soot and carbon monoxide (CO) gas, which was ejected out from side building into an urban street canyon with aspect ratio of 1 was investigated by large eddy simulation (LES) under a perpendicular wind flow. Strong buoyancy effect, which has not been revealed before, on such pollution dispersion in the street canyon was studied. The buoyancy release rate was 5 MW. The wind speed concerned ranged from 1 to 7.5m/s. The characteristics of flow pattern, distribution of smoke soot and temperature, CO concentration were revealed by the LES simulation. Dimensionless Froude number (Fr) was firstly introduced here to characterize the pollutant dispersion with buoyancy effect counteracting the wind. It was found that the flow pattern can be well categorized into three regimes. A regular characteristic large vortex was shown for the CO concentration contour when the wind velocity was higher than the critical re-entrainment value. A new formula was theoretically developed to show quantitatively that the critical re-entrainment wind velocities, u(c), for buoyancy source at different floors, were proportional to -1/3 power of the characteristic height. LES simulation results agreed well with theoretical analysis. The critical Froude number was found to be constant of 0.7. Copyright © 2010 Elsevier B.V. All rights reserved.

Experimental simulation of corium dispersion phenomena in direct containment heating

International Nuclear Information System (INIS)

Wu, Q.

1996-01-01

In a direct containment heating (DCH) accident scenario, the degree of corium dispersion is one of the most significant factors responsible for the reactor containment heating and pressurization. To study the mechanisms of the corium dispersion phenomenon, a DCH separate effect test facility of 1:10 linear scale for Zion PWR geometry is constructed. Experiments are carried out with air-water and air-woods metal simulating steam and molten core materials. The physical process of corium dispersion is studied in detail through various instruments, as well as with flow visualization at several locations. The accident transient begins with the liquid jet discharge at the bottom of the reactor pressure vessel. Once the jet impinges on the cavity bottom floor, it immediately spreads out and moves rapidly to the cavity exit as a film flow. Part of the discharged liquid flows out of the cavity before gas blowdown, and the rest is subjected to the entrainment process due to the high speed gas stream. The liquid film and droplet flows from the reactor cavity will then experience subcompartment trapping and re-entrainment. Consequently, the dispersed liquid droplets that follow the gas stream are transported into the containment atmosphere, resulting in containment heating and pressurization in the prototypic condition. Comprehensive measurements are obtained in this study, including the liquid jet velocity, liquid film thickness and velocity transients in the test cavity, gas velocity and velocity profile in the cavity, droplet size distribution and entrainment rate, and the fraction of dispersed liquid in the containment building. These data are of great importance for better understanding of the corium dispersion mechanisms. (orig.)

Accurate Recovery of H i Velocity Dispersion from Radio Interferometers

Energy Technology Data Exchange (ETDEWEB)

Ianjamasimanana, R. [Max-Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Blok, W. J. G. de [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Heald, George H., E-mail: roger@mpia.de, E-mail: blok@astron.nl, E-mail: George.Heald@csiro.au [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV, Groningen (Netherlands)

2017-05-01

Gas velocity dispersion measures the amount of disordered motion of a rotating disk. Accurate estimates of this parameter are of the utmost importance because the parameter is directly linked to disk stability and star formation. A global measure of the gas velocity dispersion can be inferred from the width of the atomic hydrogen (H i) 21 cm line. We explore how several systematic effects involved in the production of H i cubes affect the estimate of H i velocity dispersion. We do so by comparing the H i velocity dispersion derived from different types of data cubes provided by The H i Nearby Galaxy Survey. We find that residual-scaled cubes best recover the H i velocity dispersion, independent of the weighting scheme used and for a large range of signal-to-noise ratio. For H i observations, where the dirty beam is substantially different from a Gaussian, the velocity dispersion values are overestimated unless the cubes are cleaned close to (e.g., ∼1.5 times) the noise level.

Droplet dispersion angle measurements on a Pease-Antony Venturi scrubber

Directory of Open Access Journals (Sweden)

N. A. G. Puentes

2012-03-01

Full Text Available A Pease-Anthony Venturi scrubber is a gas cleaning device that uses liquid, injected in the equipment as jets, to remove contaminants from the gas. The liquid jet is atomized into droplets, which are dispersed throughout the equipment due to the turbulence. The performance of the scrubber is affected by the spatial distribution of the droplets. Although CFD models have been used to predict the droplet dispersion, these models are expensive. Alternatively, the concept of "jet spreading angle" could be used as a simple and quick way to estimate droplet dispersion. The purpose of this paper is to measure the spreading angle of jets transversally injected into the throat of a Venturi scrubber and correlate it with both gas and jet velocities. The throat gas velocities varied between 59 and 74 m/s and the jet velocity between 3.18 and 19.1 m/s. The angles were measured through image analysis, obtained with high velocity photography. The spreading angle was found to be strongly dependent on jet velocity.

Modelling airborne dispersion for disaster management

Science.gov (United States)

Musliman, I. A.; Yohnny, L.

2017-05-01

Industrial disasters, like any other disasters, can happen anytime, anywhere and in any form. Airborne industrial disaster is a kind of catastrophic event involving the release of particles such as chemicals and industrial wastes into environment in gaseous form, for instance gas leakages. Unlike solid and liquid materials, gases are often colourless and odourless, the particles are too tiny to be visible to the naked eyes; hence it is difficult to identify the presence of the gases and to tell the dispersion and location of the substance. This study is to develop an application prototype to perform simulation modelling on the gas particles to determine the dispersion of the gas particles and to identify the coverage of the affected area. The prototype adopted Lagrangian Particle Dispersion (LPD) model to calculate the position of the gas particles under the influence of wind and turbulent velocity components, which are the induced wind due to the rotation of the Earth, and Convex Hull algorithm to identify the convex points of the gas cloud to form the polygon of the coverage area. The application performs intersection and overlay analysis over a set of landuse data at Pasir Gudang, Johor industrial and residential area. Results from the analysis would be useful to tell the percentage and extent of the affected area, and are useful for the disaster management to evacuate people from the affected area. The developed application can significantly increase efficiency of emergency handling during a crisis. For example, by using a simulation model, the emergency handling can predict what is going to happen next, so people can be well informed and preparations works can be done earlier and better. Subsequently, this application helps a lot in the decision making process.

Modelling airborne dispersion for disaster management

International Nuclear Information System (INIS)

Musliman, I A; Yohnny, L

2017-01-01

Industrial disasters, like any other disasters, can happen anytime, anywhere and in any form. Airborne industrial disaster is a kind of catastrophic event involving the release of particles such as chemicals and industrial wastes into environment in gaseous form, for instance gas leakages. Unlike solid and liquid materials, gases are often colourless and odourless, the particles are too tiny to be visible to the naked eyes; hence it is difficult to identify the presence of the gases and to tell the dispersion and location of the substance. This study is to develop an application prototype to perform simulation modelling on the gas particles to determine the dispersion of the gas particles and to identify the coverage of the affected area. The prototype adopted Lagrangian Particle Dispersion (LPD) model to calculate the position of the gas particles under the influence of wind and turbulent velocity components, which are the induced wind due to the rotation of the Earth, and Convex Hull algorithm to identify the convex points of the gas cloud to form the polygon of the coverage area. The application performs intersection and overlay analysis over a set of landuse data at Pasir Gudang, Johor industrial and residential area. Results from the analysis would be useful to tell the percentage and extent of the affected area, and are useful for the disaster management to evacuate people from the affected area. The developed application can significantly increase efficiency of emergency handling during a crisis. For example, by using a simulation model, the emergency handling can predict what is going to happen next, so people can be well informed and preparations works can be done earlier and better. Subsequently, this application helps a lot in the decision making process. (paper)

Droplet dispersion angle measurements on a Pease-Antony Venturi scrubber

OpenAIRE

Puentes,N. A. G.; Guerra,V. G.; Coury,J. R.; Gonçalves,J. A. S.

2012-01-01

A Pease-Anthony Venturi scrubber is a gas cleaning device that uses liquid, injected in the equipment as jets, to remove contaminants from the gas. The liquid jet is atomized into droplets, which are dispersed throughout the equipment due to the turbulence. The performance of the scrubber is affected by the spatial distribution of the droplets. Although CFD models have been used to predict the droplet dispersion, these models are expensive. Alternatively, the concept of "jet spreading angle" ...

Studies of emulsification, emulsion prevention and underwater dispersion

Energy Technology Data Exchange (ETDEWEB)

Celius, H.K.; Vassbotn, T.

1985-03-01

This is a report from the work performed under task 2: ''Effect of demulsifiers and despersants injected into a blowing oil stream'' of the research program ''Dispersion of oil on sea''. Three ad hoc experiments have been carried out involving laboratory studies in a small turbulent oil plume, tests with revolving flasks, and a small scale field test with a combined gas/oil plume. The results show that emulsion is formed in plume from underwater blowouts, and that this formation is prevented by small amounts (250 ppM) of demulsifiers or dispersants. Larger concentrations of dispersants (ca 2%) disperse the oil, and the oil is transported to the upper water layer in the gas/oil plume. None of the experiments have been designed as true scale tests, and the results cannot be directly transferred to operational, full scale conditions. The experiments have however narroved the necessary extent of studies, and allows for a simpler experimental procedure in the full scale field test planned for June 1985. 19 references.

Origin of Scale-Dependent Dispersivity and Its Implications For Miscible Gas Flooding

Energy Technology Data Exchange (ETDEWEB)

Steven Bryant; Russ Johns; Larry Lake; Thomas Harmon

2008-09-30

Dispersive mixing has an important impact on the effectiveness of miscible floods. Simulations routinely assume Fickian dispersion, yet it is well established that dispersivity depends on the scale of measurement. This is one of the main reasons that a satisfactory method for design of field-scale miscible displacement processes is still not available. The main objective of this project was to improve the understanding of the fundamental mechanisms of dispersion and mixing, particularly at the pore scale. To this end, microsensors were developed and used in the laboratory to measure directly the solute concentrations at the scale of individual pores; the origin of hydrodynamic dispersion was evaluated from first principles of laminar flow and diffusion at the grain scale in simple but geometrically completely defined porous media; techniques to use flow reversal to distinguish the contribution to dispersion of convective spreading from that of true mixing; and the field scale impact of permeability heterogeneity on hydrodynamic dispersion was evaluated numerically. This project solved a long-standing problem in solute transport in porous media by quantifying the physical basis for the scaling of dispersion coefficient with the 1.2 power of flow velocity. The researchers also demonstrated that flow reversal uniquely enables a crucial separation of irreversible and reversible contributions to mixing. The interpretation of laboratory and field experiments that include flow reversal provides important insight. Other advances include the miniaturization of long-lasting microprobes for in-situ, pore-scale measurement of tracers, and a scheme to account properly in a reservoir simulator (grid-block scale) for the contributions of convective spreading due to reservoir heterogeneity and of mixing.

Refined potentials for rare gas atom adsorption on rare gas and alkali-halide surfaces

Science.gov (United States)

Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

1985-01-01

The utilization of models of interatomic potential for physical interaction to estimate the long range attractive potential for rare gases and ions is discussed. The long range attractive force is calculated in terms of the atomic dispersion properties. A data base of atomic dispersion parameters for rare gas atoms, alkali ion, and halogen ions is applied to the study of the repulsive core; the procedure for evaluating the repulsive core of ion interactions is described. The interaction of rare gas atoms on ideal rare gas solid and alkali-halide surfaces is analyzed; zero coverage absorption potentials are derived.

LNG vapor dispersion prediction with the DEGADIS dense-gas dispersion model. Topical report, April 1988-July 1990. Documentation

International Nuclear Information System (INIS)

Havens, J.; Spicer, T.

1990-09-01

The topical report is one of a series on the development of methods for LNG vapor dispersion prediction for regulatory application. The results indicate that the DEGADIS model is superior both phenomenologically and in performance to the Gaussian line source model promulgated in 49 CFR 193 for LNG vapor dispersion simulation. Availability of the DEGADIS model for VAX and IBM-PC formats provides for wider use of the model and greater potential for industry and regulatory acceptance. The acceptance is seen as an important interim objective while research continues on vapor dispersion estimation methods which provide for effects of vapor detention systems, turbulence induced by plant structure, and plant/area topographical features

Parallelization of simulation code for liquid-gas model of lattice-gas fluid

International Nuclear Information System (INIS)

Kawai, Wataru; Ebihara, Kenichi; Kume, Etsuo; Watanabe, Tadashi

2000-03-01

A simulation code for hydrodynamical phenomena which is based on the liquid-gas model of lattice-gas fluid is parallelized by using MPI (Message Passing Interface) library. The parallelized code can be applied to the larger size of the simulations than the non-parallelized code. The calculation times of the parallelized code on VPP500 (Vector-Parallel super computer with dispersed memory units), AP3000 (Scalar-parallel server with dispersed memory units), and a workstation cluster decreased in inverse proportion to the number of processors. (author)

Transport of temperature-velocity covariance in gas-solid flow and its relation to the axial dispersion coefficient

Science.gov (United States)

Subramaniam, Shankar; Sun, Bo

2015-11-01

The presence of solid particles in a steady laminar flow generates velocity fluctuations with respect to the mean fluid velocity that are termed pseudo-turbulence. The level of these pseudo-turbulent velocity fluctuations has been characterized in statistically homogeneous fixed particle assemblies and freely evolving suspensions using particle-resolved direct numerical simulation (PR-DNS) by Mehrabadi et al. (JFM, 2015), and it is found to be a significant contribution to the total kinetic energy associated with the flow. The correlation of these velocity fluctuations with temperature (or a passive scalar) generates a flux term that appears in the transport equation for the average fluid temperature (or average scalar concentration). The magnitude of this transport of temperature-velocity covariance is quantified using PR-DNS of thermally fully developed flow past a statistically homogeneous fixed assembly of particles, and the budget of the average fluid temperature equation is presented. The relation of this transport term to the axial dispersion coefficient (Brenner, Phil. Trans. Roy. Soc. A, 1980) is established. The simulation results are then interpreted in the context of our understanding of axial dispersion in gas-solid flow. NSF CBET 1336941.

Dispersion of a layered electron gas with nearest neighbour-tunneling

International Nuclear Information System (INIS)

Miesenboeck, H.M.

1988-09-01

The dispersion of the first plasmon band is calculated within the Random Phase Approximation for a superlattice of two-dimensional electron-gases, mutually interacting, and with nearest neighbour hopping between the planes. It is further shown that the deviations of this dispersion from the one in systems with zero interplane motion are very small in commonly realized experimental situations and that they are expected to be observable only in samples with plane distances of 100A and less. (author). 15 refs, 3 figs, 1 tab

75 FR 53371 - Liquefied Natural Gas Facilities: Obtaining Approval of Alternative Vapor-Gas Dispersion Models

Science.gov (United States)

2010-08-31

.... PHMSA-2010-0226] Liquefied Natural Gas Facilities: Obtaining Approval of Alternative Vapor-Gas... safety standards for siting liquefied natural gas (LNG) facilities. Those standards require that an..., and Handling of Liquefied Natural Gas. That consensus [[Page 53372

Measurement of phase interaction in dispersed gas-particle two-phase flow by phase-doppler anemometry

Directory of Open Access Journals (Sweden)

Mergheni Ali Mohamed

2008-01-01

Full Text Available For simultaneous measurement of size and velocity distributions of continuous and dispersed phases in a two-phase flow a technique phase-Doppler anemometry was used. Spherical glass particles with a particle diameter range from 102 up to 212 µm were used. In this two-phase flow an experimental results are presented which indicate a significant influence of the solid particles on the flow characteristics. The height of influence of these effects depends on the local position in the jet. Near the nozzle exit high gas velocity gradients exist and therefore high turbulence production in the shear layer of the jet is observed. Here the turbulence intensity in the two-phase jet is decreased compared to the single-phase jet. In the developed zone the velocity gradient in the shear layer is lower and the turbulence intensity reduction is higher. .

Review of potential models for UF6 dispersion

International Nuclear Information System (INIS)

Sykes, R.I.; Lewellen, W.S.

1992-07-01

A survey of existing atmospheric dispersion models has been conducted to determine the most appropriate basis for the development of a model for predicting the consequences of an accidental UF 6 release. The model is required for safety analysis studies and should therefore be computationally efficient. The release of UF 6 involves a number of physical phenomena which make the situation more complicated than passive dispersion of a trace gas. The safety analysis must consider the density variations in the UF 6 cloud, which can be heavier or lighter than the ambient air. The release also involves rapid chemical reactions and associated heat release, which must be modeled. Other Department of Energy storage facilities require a dense gas prediction capability, so the model must be sufficiently general for use with a variety of release scenarios. The special problems associated with UF 6 make it unique, so there are very few models with existing capability for the problem. There are, however, a large number of dense gas dispersion models, some with relevant chemical reaction modeling, that could potentially form the basis of an advanced UF 6 model. We have examined a large selection of possible candidates, and selected 5 models for detailed consideration

Critical confrontation of standard and more sophisticated methods for modelling the dispersion in air of heavy gas clouds; evaluation and illustration of the intrinsic limitations of both categories

International Nuclear Information System (INIS)

Riethmuller, M.L.

1983-01-01

Mathematical models of gas dispersion have evolved drastically since the 1930's. For a long time, the most widely used approach was the so-called Gaussian model as described in practical terms by Turner or box models which have shown relative merits. In the field of heavy gas dispersion, the use of such approaches appeared somewhat limited and therefore new models have been proposed. Some of these new generation models were making use of the latest progress in turbulence modelling as derived from laboratory work as well as numerical advances. The advent of faster and larger computers made possible the development of three dimensional codes that were computing both flow field and gas dispersion taking into account details of the ground obstacles, heat exchange and possibly phase changes as well. The description of these new types of models makes them appear as a considerable improvement over the simpler approaches. However, recent comparisons between many of these have led to the conclusion that the scatter between predictions attained with sophisticated models was just as large as with other ones. It seems therefore, that current researchers might have fallen into the trap of confusing mathematical precision with accuracy. It is therefore felt necessary to enlighten this question by an investigation which, rather than comparing individual models, would analyse the key features of both approaches and put in evidence their relative merits and degree of realism when being really applied

Modeling solid-fuel dispersal during slow loss-of-flow-type transients

International Nuclear Information System (INIS)

DiMelfi, R.J.; Fenske, G.R.

1981-01-01

The dispersal, under certain accident conditions, of solid particles of fast-reactor fuel is examined in this paper. In particular, we explore the possibility that solid-fuel fragmentation and dispersal can be driven by expanding fission gas, during a slow LOF-type accident. The consequences of fragmentation are studied in terms of the size and speed of dispersed particles, and the overall quantity of fuel moved. (orig.)

Assessment of cavity dispersal correlations for possible implementation in the CONTAIN code

International Nuclear Information System (INIS)

Williams, D.C.; Griffith, R.O.

1996-02-01

Candidate models and correlations describing entrainment and dispersal of core debris from reactor cavities in direct containment heating (DCH) event, are assessed against a data base of approximately 600 experiments performed previously at Brookhaven National Laboratory and Sandia National Laboratories reactor cavities was studied. Cavity geometries studied are those of the Surry and Zion nuclear power plants and scale factors of 1/42 and 1/10 were studied for both geometries. Other parameters varied in the experiments include gas pressure driving the dispersal, identities of the driving gas and of the simulant fluid, orifice diameter in the pressure vessel, and volume of the gas pressure vessel. Correlations were assessed in terms of their ability to reproduce the observed trends in the fractions dispersed as the experimental parameters were varied. For the fraction of the debris dispersed, the correlations recommended for inclusion in the CONTAIN code are the Tutu-Ginsberg correlations, the integral form of the correlation proposed by Levy and a modified form of the Whalley-Hewitt correlation. For entrainment rates, the recommended correlations are the time-dependent forms of the Levy correlation, a correlation suggested by Tutu, and the modified Whalley-Hewitt correlation

Growth of plant root cultures in liquid- and gas-dispersed reactor environments.

Science.gov (United States)

McKelvey, S A; Gehrig, J A; Hollar, K A; Curtis, W R

1993-01-01

The growth of Agrobacterium transformed "hairy root" cultures of Hyoscyamus muticus was examined in various liquid- and gas-dispersed bioreactor configurations. Reactor runs were replicated to provide statistical comparisons of nutrient availability on culture performance. Accumulated tissue mass in submerged air-sparged reactors was 31% of gyratory shake-flask controls. Experiments demonstrate that poor performance of sparged reactors is not due to bubble shear damage, carbon dioxide stripping, settling, or flotation of roots. Impaired oxygen transfer due to channeling and stagnation of the liquid phase are the apparent causes of poor growth. Roots grown on a medium-perfused inclined plane grew at 48% of gyratory controls. This demonstrates the ability of cultures to partially compensate for poor liquid distribution through vascular transport of nutrients. A reactor configuration in which the medium is sprayed over the roots and permitted to drain down through the root tissue was able to provide growth rates which are statistically indistinguishable (95% T-test) from gyratory shake-flask controls. In this type of spray/trickle-bed configuration, it is shown that distribution of the roots becomes a key factor in controlling the rate of growth. Implications of these results regarding design and scale-up of bioreactors to produce fine chemicals from root cultures are discussed.

Contaminant dispersion prediction and source estimation with integrated Gaussian-machine learning network model for point source emission in atmosphere

International Nuclear Information System (INIS)

Ma, Denglong; Zhang, Zaoxiao

2016-01-01

Highlights: • The intelligent network models were built to predict contaminant gas concentrations. • The improved network models coupled with Gaussian dispersion model were presented. • New model has high efficiency and accuracy for concentration prediction. • New model were applied to indentify the leakage source with satisfied results. - Abstract: Gas dispersion model is important for predicting the gas concentrations when contaminant gas leakage occurs. Intelligent network models such as radial basis function (RBF), back propagation (BP) neural network and support vector machine (SVM) model can be used for gas dispersion prediction. However, the prediction results from these network models with too many inputs based on original monitoring parameters are not in good agreement with the experimental data. Then, a new series of machine learning algorithms (MLA) models combined classic Gaussian model with MLA algorithm has been presented. The prediction results from new models are improved greatly. Among these models, Gaussian-SVM model performs best and its computation time is close to that of classic Gaussian dispersion model. Finally, Gaussian-MLA models were applied to identifying the emission source parameters with the particle swarm optimization (PSO) method. The estimation performance of PSO with Gaussian-MLA is better than that with Gaussian, Lagrangian stochastic (LS) dispersion model and network models based on original monitoring parameters. Hence, the new prediction model based on Gaussian-MLA is potentially a good method to predict contaminant gas dispersion as well as a good forward model in emission source parameters identification problem.

Contaminant dispersion prediction and source estimation with integrated Gaussian-machine learning network model for point source emission in atmosphere

Energy Technology Data Exchange (ETDEWEB)

Ma, Denglong [Fuli School of Food Equipment Engineering and Science, Xi’an Jiaotong University, No.28 Xianning West Road, Xi’an 710049 (China); Zhang, Zaoxiao, E-mail: zhangzx@mail.xjtu.edu.cn [State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, No.28 Xianning West Road, Xi’an 710049 (China); School of Chemical Engineering and Technology, Xi’an Jiaotong University, No.28 Xianning West Road, Xi’an 710049 (China)

2016-07-05

Highlights: • The intelligent network models were built to predict contaminant gas concentrations. • The improved network models coupled with Gaussian dispersion model were presented. • New model has high efficiency and accuracy for concentration prediction. • New model were applied to indentify the leakage source with satisfied results. - Abstract: Gas dispersion model is important for predicting the gas concentrations when contaminant gas leakage occurs. Intelligent network models such as radial basis function (RBF), back propagation (BP) neural network and support vector machine (SVM) model can be used for gas dispersion prediction. However, the prediction results from these network models with too many inputs based on original monitoring parameters are not in good agreement with the experimental data. Then, a new series of machine learning algorithms (MLA) models combined classic Gaussian model with MLA algorithm has been presented. The prediction results from new models are improved greatly. Among these models, Gaussian-SVM model performs best and its computation time is close to that of classic Gaussian dispersion model. Finally, Gaussian-MLA models were applied to identifying the emission source parameters with the particle swarm optimization (PSO) method. The estimation performance of PSO with Gaussian-MLA is better than that with Gaussian, Lagrangian stochastic (LS) dispersion model and network models based on original monitoring parameters. Hence, the new prediction model based on Gaussian-MLA is potentially a good method to predict contaminant gas dispersion as well as a good forward model in emission source parameters identification problem.

Molecularly Imprinted Nanomicrospheres as Matrix Solid-Phase Dispersant Combined with Gas Chromatography for Determination of Four Phosphorothioate Pesticides in Carrot and Yacon

Directory of Open Access Journals (Sweden)

Mengchun Zhou

2015-01-01

Full Text Available An efficient, rapid, and selective method for sample pretreatment, namely, molecularly imprinted matrix solid-phase dispersion (MI-MSPD coupled with gas chromatography (GC, was developed for the rapid isolation of four phosphorothioate organophosphorus pesticides (tolclofos-methyl, phoxim, chlorpyrifos, and parathion-methyl from carrot and yacon samples. New molecularly imprinted polymer nanomicrospheres were synthesized by using typical structural analogue tolclofos-methyl as a dummy template via surface grafting polymerization on nanosilica. Then, these four pesticides in carrot and yacon were extracted and adsorbed using the imprinted nanomicrospheres and further determined by gas chromatography. Under the optimized conditions, a good linearity of four pesticides was obtained in a range of 0.05–17.0 ng·g−1 with R varying from 0.9971 to 0.9996, and the detection limit of the method was 0.012~0.026 ng·g−1 in carrot and yacon samples. The recovery rates at two spiked levels were in the range of 85.4–105.6% with RSD ≤9.6%. The presented MI-MSPD method combined the advantages of MSPD for allowing the extraction, dispersion, and homogenization in two steps and the advantages of MIPs for high affinity and selectivity towards four phosphorothioate pesticides, which could be applied to the determination of pesticide residues in complicated vegetal samples.

Testing of a new dense gas approach in the Lagrangian Dispersion Model SPRAY.

Science.gov (United States)

Mortarini, Luca; Alessandrini, Stefano; Ferrero, Enrico; Anfossi, Domenico; Manfrin, Massimiliano

2013-04-01

A new original method for the dispersion of a positively and negatively buoyant plume is proposed. The buoyant pollutant movement is treated introducing a fictitious scalar inside the Lagrangian Stochastic Particle Model SPRAY. The method is based on the same idea of Alessandrini and Ferrero (Phys. A 388:1375-1387, 2009) for the treatment of a background substance entrainment into the plume. In this application, the fictitious scalar is the density and momentum difference between the plume portions and the environment air that naturally takes into account the interaction between the plume and the environment. As a consequence, no more particles than those inside the plume have to be released to simulate the entrainment of the background air temperature. In this way the entrainment is properly simulated and the plume sink is calculated from the local property of the flow. This new approach is wholly Lagrangian in the sense that the Eulerian grid is only used to compute the propriety of a portion of the plume from the particles contained in every cell. No equation of the bulk plume is solved on a fixed grid. To thoroughly test the turbulent velocity field calculated by the model, the latter is compared with a water tank experiment carried out in the TURLAB laboratory in Turin (Italy). A vertical density driven current was created releasing a saline solution (salt and water) in a water tank with no mean flow. The experiment reproduces in physical similarity, based on the density Froud number, the release of a dense gas in the planetary boundary layer and the Particle Image Velocimetry technique has been used to analyze the buoyancy generated velocity field. The high temporal and spatial resolution of the measurements gives a deep insight to the problems of the bouncing of the dense gas and of the creation of the outflow velocity at the ground.

Determination of solvent concentration-dependent dispersion in the vapor extraction (VAPEX) process

Energy Technology Data Exchange (ETDEWEB)

Abukhalifeh, H.; Lohi, A.; Upreti, S. [Ryerson Polytechnic Univ., Toronto, ON (Canada)

2008-07-01

This paper presented the results of a computational algorithm that revealed the optimal conditions required for vapor extraction (VAPEX) for a solvent gas-heavy oil system. VAPEX is a promising recovery process because it requires low energy use and emits fewer greenhouse gases to the atmosphere compared to other enhanced oil recovery methods. The process is governed by the dispersion of solvent gases into heavy oil and bitumen. As such, it is essential to accurately determine solvent dispersion in VAPEX in order to effectively predict the amount and time scale of oil recovery, and to optimize field operations. VAPEX experiments were conducted in this study to determined the dispersion coefficient of a solvent as a function of its concentration in heavy oil and bitumen. The principles of variational calculus were used together with a mass transfer model of the experimental process. It was concluded that the oil production determined by the model should agree with its experimental counterpart, given the optimal gas dispersion versus concentration function.

An anomalous extinction law in the Cep OB3b young cluster: Evidence for dust processing during gas dispersal

International Nuclear Information System (INIS)

Allen, Thomas S.; Prchlik, Jakub J.; Megeath, S. Thomas; Gutermuth, Robert A.; Pipher, Judith L.; Naylor, Tim; Jeffries, R. D.

2014-01-01

We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and K s photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the R V = 3.1 and R V = 5 laws commonly used for the diffuse atomic interstellar medium and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight A V is investigated and we find the extinction law becomes shallower for regions with A V > 2.5 mag. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster.

An anomalous extinction law in the Cep OB3b young cluster: Evidence for dust processing during gas dispersal

Energy Technology Data Exchange (ETDEWEB)

Allen, Thomas S.; Prchlik, Jakub J.; Megeath, S. Thomas [University of Toledo, Ritter Astrophysical Observatory, Department of Physics and Astronomy, Toledo, OH 43606 (United States); Gutermuth, Robert A. [Five College Astronomy Department, Smith College, Northampton, MA 01063 (United States); Pipher, Judith L. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Naylor, Tim [School of Physics, University of Exeter, Exeter, UK EX4 4QL (United Kingdom); Jeffries, R. D. [Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire, UK ST5 5BG (United Kingdom)

2014-05-10

We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and K{sub s} photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the R{sub V} = 3.1 and R{sub V} = 5 laws commonly used for the diffuse atomic interstellar medium and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight A{sub V} is investigated and we find the extinction law becomes shallower for regions with A{sub V} > 2.5 mag. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster.

Measurement and simulation of the turbulent dispersion of a radioactive tracer in a two-phase flow system

Energy Technology Data Exchange (ETDEWEB)

Hensel, F; Rohde, U

1998-10-01

The turbulent dispersion of a radiotracer in an experimental setup with a natural convection liquid-gaseous flow was investigated. A liquid-gaseous bubbly flow was generated in a narrow tank by injection of pressurized air into water or by catalytic disintegration of H{sub 2}O{sub 2}. Turbulent Prandtl numbers for gas and tracer dispersion were varied. In the case of higher gas superficial velocities (J{sub gas}{approx}5-15 mm/s), a reasonable agreement was achieved between calculated and measured tracer transport velocity and dispersion coefficient values. A nearly linear correlation between j{sub gas} and D was found in agreement with other authors. The calculation results contribute to a better understanding of the phenomena and interpretation of the measurement results as well as to the validation of the CFD code for turbulent two-phase flow applications. Further investigations are necessary to improve the agreement in the cases of H{sub 2}O{sub 2} disintegration and low gas superficial velocities. (orig.)

Measurement and simulation of the turbulent dispersion of a radioactive tracer in a two-phase flow system

International Nuclear Information System (INIS)

Hensel, F.; Rohde, U.

1998-01-01

The turbulent dispersion of a radiotracer in an experimental setup with a natural convection liquid-gaseous flow was investigated. A liquid-gaseous bubbly flow was generated in a narrow tank by injection of pressurized air into water or by catalytic disintegration of H 2 O 2 . Turbulent Prandtl numbers for gas and tracer dispersion were varied. In the case of higher gas superficial velocities (J gas ∼5-15 mm/s), a reasonable agreement was achieved between calculated and measured tracer transport velocity and dispersion coefficient values. A nearly linear correlation between j gas and D was found in agreement with other authors. The calculation results contribute to a better understanding of the phenomena and interpretation of the measurement results as well as to the validation of the CFD code for turbulent two-phase flow applications. Further investigations are necessary to improve the agreement in the cases of H 2 O 2 disintegration and low gas superficial velocities. (orig.)

Irradiation behavior of low-enriched U/sub 6/Fe-Al dispersion fuel elements

Energy Technology Data Exchange (ETDEWEB)

Hofman, G.L.; Domagala, R.F.; Copeland, G.L.

1987-10-01

An irradiation test of miniature fuel plates containing low-enriched (20% /sup 235/U)U/sub 6/Fe dispersed and clad in Al was performed. The postirradiation examination shows U/sub 6/Fe to form extensive fission gas bubbles at burnups of only approx. = 20% of the original 20% fuel enrichment. Plate failure by fission gas-driven pillowing occurred at approx. = 40% burnup. This places U/sub 6/FE at the lowest burnup capability among low enriched dispersion fuels that have been tested for use in research and test reactors

Dispersion of Waxy Gas Oil by Some Nonionic Surfactants

International Nuclear Information System (INIS)

Khidr, T.T.; Mahmoud, S.A.

2004-01-01

Straight chain fatty alcohols having the following number of carbon atoms C 12 , C 14 , C 18 and C 21 each alcohol was ethoxylated to the same of ethylene oxide content, characterized through average molecular weight and elemental analysis. The surface properties of these compounds were studied through surface tension measurements. The synthesized additives were tested as flow improvers for improving the cold flow properties of two waxy gas oils through pour point test. The results show the right efficiency of these compounds in improving the flow ability. Comparative evaluation of the synthesized products with available commercial additive (com) showed their efficiency and suitability to use in gas oils. Wax modification was assisted through photo analysis. Correlation between wax modification and flow improvement in term of pour point depression appeared to be merely qualitative in such heterogeneous gas oil systems

Surface-plasmon dispersion relation for the inhomogeneous charge-density medium

International Nuclear Information System (INIS)

Harsh, O.K.; Agarwal, B.K.

1989-01-01

The surface-plasmon dispersion relation is derived for the plane-bounded electron gas when there is an inhomogeneous charge-density distribution in the plasma. The hydrodynamical model is used. Both cphi and dcphi/dx are taken to be continuous at the surface of the slab, where cphi is the scalar potential. The dispersion relation is compared with the theoretical works of Stern and Ferrell and of Harsh and Agarwal. It is also compared with the observations of Kunz. A dispersion relation for the volume-plasmon oscillations is derived which resembles the well-known relation of Bohm and Pines

Hypersonic flow past slender bodies in dispersive hydrodynamics

International Nuclear Information System (INIS)

El, G.A.; Khodorovskii, V.V.; Tyurina, A.V.

2004-01-01

The problem of two-dimensional steady hypersonic flow past a slender body is formulated for dispersive media. It is shown that for the hypersonic flow, the original 2+0 boundary-value problem is asymptotically equivalent to the 1+1 piston problem for the fully nonlinear flow in the same physical system, which allows one to take advantage of the analytic methods developed for one-dimensional systems. This type of equivalence, well known in ideal Euler gas dynamics, has not been established for dispersive hydrodynamics so far. Two examples pertaining to collisionless plasma dynamics are considered

A galactic disk as a two-fluid system: Consequences for the critical stellar velocity dispersion and the formation of condensations in the gas

International Nuclear Information System (INIS)

Jog, C.J.; Solomon, P.M.

1984-01-01

We examine the consequences of treating a galactic disk as a two-fluid system for the stability of the entire disk and for the stability and form of the gas in the disk. We find that the existence of even a small fraction of the total disk surface density in a cold fluid (that is, the gas) makes it much harder to stabilize the entire two-fluid disk. (C/sub s/,min)/sub 2-f/, the critical stellar velocity dispersion for a two-fluid disk in an increasing function of μ/sub g//μ/sub s/, the gas fraction, and μ/sub t//kappa, where μ/sub g/, μ/sub s/, and μ/sub t/ are the gaseous, stellar, and total disk surface densities and kappa is the epicyclic frequency. In the Galaxy, we find that (C/sub s/,min)/sub 2-f/ as a function of R peaks when μ/sub t//kappa peaks-at galactocentric radii of Rapprox.5-7 kpc; two-fluid instabilities are most likely to occur in this region. This region is coincident with the peak in the molecular cloud distribution in the Galaxy. At the higher effective gas density resulting from the growth of a two-fluid instability, the gas may become unstble, even when originally the gas by itself is stable. The wavelength of a typical (induced) gas instability in the inner galaxy is approx.400 pc, and it contains approx.10 7 M/sub sun/ of interstellar matter; these instabilities may be identified with clusters of giant molecular clouds. We suggest that many of the spiral features seen in gas-rich spiral galaxies may be material arms or arm segments resulting from sheared two-fluid gravitational instabilities. The analysis presented here is applicable to any general disk galaxy consisting of stars and gas

Determination of Parabens by Injection-Port Derivatization Coupled With Gas-Chromatography-Mass Spectrometry and Matrix Solid Phase Dispersion

Science.gov (United States)

Djatmika, Rosalina; Ding, Wang-Hsien; Sulistyarti, Hermin

2018-01-01

A rapid determination of four parabens preservatives (methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) in marketed seafood is presented. Analytes were extracted and purified using matrix solid-phase dispersion (MSPD) method, followed by Injection port acylation gas chromatography-mass spectrometry (GC-MS) with acetic anhydride reagent. In this method, acylation of parabens was performed by acetic anhydride at GC injection-port generating reduction of the time-consuming sample-processing steps, and the amount of toxic reagents and solvents. The parameters affecting this method such as injection port temperature, purge-off time and acylation (acetic anhydride) volume were studied. In addition, the MSPD influence factors (including the amount of dispersant and clean-up co-sorbent, as well as the volume of elution solvent) were also investigated. After MSPD method and Injection port acylation applied, good linearity of analytes was achieved. The limits of quantitation (LOQs) were 0.2 to 1.0 ng/g (dry weight). Compared with offline derivatization commonly performed, injection port acylation employs a rapid, simple, low-cost and environmental-friendly derivatization process. The optimized method has been successfully applied for the analysis of parabens in four kind of marketed seafood. Preliminary results showed that the total concentrations of four selected parabens ranged from 16.7 to 44.7 ng/g (dry weight).

Simultaneous derivatisation and preconcentration of parabens in food and other matrices by isobutyl chloroformate and dispersive liquid-liquid microextraction followed by gas chromatographic analysis.

Science.gov (United States)

Jain, Rajeev; Mudiam, Mohana Krishna Reddy; Chauhan, Abhishek; Ch, Ratnasekhar; Murthy, R C; Khan, Haider A

2013-11-01

A simple, rapid and economical method has been proposed for the quantitative determination of parabens (methyl, ethyl, propyl and butyl paraben) in different samples (food, cosmetics and water) based on isobutyl chloroformate (IBCF) derivatisation and preconcentration using dispersive liquid-liquid microextraction in single step. Under optimum conditions, solid samples were extracted with ethanol (disperser solvent) and 200 μL of this extract along with 50 μL of chloroform (extraction solvent) and 10 μL of IBCF was rapidly injected into 2 mL of ultra-pure water containing 150 μL of pyridine to induce formation of a cloudy state. After centrifugation, 1 μL of the sedimented phase was analysed using gas chromatograph-flame ionisation detector (GC-FID) and the peaks were confirmed using gas chromatograph-positive chemical ionisation-mass spectrometer (GC-PCI-MS). Method was found to be linear over the range of 0.1-10 μg mL(-1) with square of correlation coefficient (R(2)) in the range of 0.9913-0.9992. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.029-0.102 μg mL(-1) and 0.095-0.336 μg mL(-1) with a signal to noise ratio of 3:1 and 10:1, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

CFD simulation of gas-liquid floating particles mixing in an agitated vessel

Directory of Open Access Journals (Sweden)

Li Liangchao

2017-01-01

Full Text Available Gas dispersion and floating particles suspension in an agitated vessel were studied numerically by using computational fluid dynamics (CFD. The Eulerian multi-fluid model along with standard k-ε turbulence model was used in the simulation. A multiple reference frame (MRF approach was used to solve the impeller rotation. The velocity field, gas and floating particles holdup distributions in the vessel were first obtained, and then, the effects of operating conditions on gas dispersion and solid suspension were investigated. The simulation results show that velocity field of solid phase and gas phase are quite different in the agitated vessel. Floating particles are easy to accumulate in the center of the surface region and the increasing of superficial gas velocity is in favor of floating particles off-surface suspension. With increasing solids loading, the gas dispersion becomes worse, while relative solid holdup distribution changes little. The limitations of the present modeling are discussed and further research in the future is proposed.

A Novel Solid State Non-Dispersive Infrared CO2 Gas Sensor Compatible with Wireless and Portable Deployment

Directory of Open Access Journals (Sweden)

Desmond Gibson

2013-05-01

Full Text Available This paper describes development of a novel mid-infrared light emitting diode (LED and photodiode (PD light source/detector combination and use within a non-dispersive infrared (NDIR carbon dioxide gas sensor. The LED/PD based NDIR sensor provides fast stabilisation time (time required to turn on the sensor from cold, warm up, take and report a measurement, and power down again ≈1 second, longevity (>15 years, low power consumption and low cost. Described performance is compatible with “fit and forget” wireless deployed sensors in applications such as indoor air quality monitoring/control & energy conservation in buildings, transport systems, horticultural greenhouses and portable deployment for safety, industrial and medical applications. Fast stabilisation time, low intrinsic power consumption and cycled operation offer typical energy consumption per measurement of mJ’s, providing extended operation using battery and/or energy harvesting strategies (measurement interval of ≈ 2 minutes provides >10 years operation from one AA battery. Specific performance data is provided in relation to measurement accuracy and noise, temperature performance, cross sensitivity, measurement range (two pathlength variants are described covering ambient through to 100% gas concentration, comparison with NDIR utilizing thermal source/pyroelectric light source/detector combination and compatibility with energy harvesting. Semiconductor based LED/PD processing together with injection moulded reflective optics and simple assembly provide a route to low cost high volume manufacturing.

A novel solid state non-dispersive infrared CO2 gas sensor compatible with wireless and portable deployment.

Science.gov (United States)

Gibson, Desmond; MacGregor, Calum

2013-05-29

This paper describes development of a novel mid-infrared light emitting diode (LED) and photodiode (PD) light source/detector combination and use within a non-dispersive infrared (NDIR) carbon dioxide gas sensor. The LED/PD based NDIR sensor provides fast stabilisation time (time required to turn on the sensor from cold, warm up, take and report a measurement, and power down again ≈1 second), longevity (>15 years), low power consumption and low cost. Described performance is compatible with "fit and forget" wireless deployed sensors in applications such as indoor air quality monitoring/control & energy conservation in buildings, transport systems, horticultural greenhouses and portable deployment for safety, industrial and medical applications. Fast stabilisation time, low intrinsic power consumption and cycled operation offer typical energy consumption per measurement of mJ's, providing extended operation using battery and/or energy harvesting strategies (measurement interval of ≈ 2 minutes provides >10 years operation from one AA battery). Specific performance data is provided in relation to measurement accuracy and noise, temperature performance, cross sensitivity, measurement range (two pathlength variants are described covering ambient through to 100% gas concentration), comparison with NDIR utilizing thermal source/pyroelectric light source/detector combination and compatibility with energy harvesting. Semiconductor based LED/PD processing together with injection moulded reflective optics and simple assembly provide a route to low cost high volume manufacturing.

Anomalous dispersion due to hydrocarbons: The secret of reservoir geophysics?

Science.gov (United States)

Brown, R.L.

2009-01-01

When P- and S-waves travel through porous sandstone saturated with hydrocarbons, a bit of magic happens to make the velocities of these waves more frequency-dependent (dispersive) than when the formation is saturated with brine. This article explores the utility of the anomalous dispersion in finding more oil and gas, as well as giving a possible explanation about the effect of hydrocarbons upon the capillary forces in the formation. ?? 2009 Society of Exploration Geophysicists.

Computational fluid dynamics modeling of gas dispersion in multi impeller bioreactor.

Science.gov (United States)

Ahmed, Syed Ubaid; Ranganathan, Panneerselvam; Pandey, Ashok; Sivaraman, Savithri

2010-06-01

In the present study, experiments have been carried out to identify various flow regimes in a dual Rushton turbines stirred bioreactor for different gas flow rates and impeller speeds. The hydrodynamic parameters like fractional gas hold-up, power consumption and mixing time have been measured. A two fluid model along with MUSIG model to handle polydispersed gas flow has been implemented to predict the various flow regimes and hydrodynamic parameters in the dual turbines stirred bioreactor. The computational model has been mapped on commercial solver ANSYS CFX. The flow regimes predicted by numerical simulations are validated with the experimental results. The present model has successfully captured the flow regimes as observed during experiments. The measured gross flow characteristics like fractional gas hold-up, and mixing time have been compared with numerical simulations. Also the effect of gas flow rate and impeller speed on gas hold-up and power consumption have been investigated. (c) 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Hypercrosslinked Additives for Ageless Gas-Separation Membranes.

Science.gov (United States)

Lau, Cher Hon; Mulet, Xavier; Konstas, Kristina; Doherty, Cara M; Sani, Marc-Antoine; Separovic, Frances; Hill, Matthew R; Wood, Colin D

2016-02-05

The loss of internal pores, a process known as physical aging, inhibits the long-term use of the most promising gas-separation polymers. Previously we reported that a porous aromatic framework (PAF-1) could form a remarkable nanocomposite with gas-separation polymers to stop aging. However, PAF-1 synthesis is very onerous both from a reagent and reaction-condition perspective, making it difficult to scale-up. We now reveal a highly dispersible and scalable additive based on α,α'-dichloro-p-xylene (p-DCX), that inhibits aging more effectively, and crucially almost doubles gas-transport selectivity. These synergistic effects are related to the intimately mixed nanocomposite that is formed though the high dispersibility of p-DCX in the gas-separation polymer. This reduces particle-size effects and the internal free volume is almost unchanged over time. This study shows this inexpensive and scalable polymer additive delivers exceptional gas-transport performance and selectivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

'' Ideal Gas '' gluon plasma with medium dependent dispersion relation

International Nuclear Information System (INIS)

Gorenstein, M.I.

1995-01-01

An '' ideal gas '' model with temperature dependent particle mass is constructed for the gluon plasma equation of state. This simple model gives us an example of a system with temperature dependent effective Hamiltonian. To satisfy thermodynamical relations in these systems, standard statistical mechanics formulas have to be supplemented by special requirements which are considered in details. A self-consistent '' ideal gas '' formulation is used to describe Monte Carlo lattice data for the thermodynamical functions of SU(2) and SU(3) gluon plasma. 14 refs., 8 figs

Optimization of two different dispersive liquid-liquid microextraction methods followed by gas chromatography-mass spectrometry determination for polycyclic aromatic hydrocarbons (PAHs) analysis in water.

Science.gov (United States)

Tseng, Wan-Chi; Chen, Pai-Shan; Huang, Shang-Da

2014-03-01

Novel sample preparation methods termed "up-and-down shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME)" and "water with low concentration of surfactant in dispersed solvent-assisted emulsion dispersive liquid-liquid microextraction (WLSEME)" coupled with gas chromatography-mass spectrometry (GC-MS) have been developed for the analysis of 11 polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. For UDSA-DLLME, an up-and-down shaker-assisted emulsification was employed. Extraction was complete in 3min. Only 14 μL of 1-heptanol was required, without a dispersive solvent. Under the optimum conditions, the linear range was 0.08-100 µg L(-1), and the LODs were in the range 0.022-0.060 µg L(-1). The enrichment factors (EFs) ranged from 392 to 766. Relative recoveries were between 84% and 113% for river, lake, and field water. In WLSEME, 9 μL of 1-nonanol as extraction solvent and 240 μL of 1 mg L(-1) Triton X-100 as surfactant were mixed in a microsyringe to form a cloudy emulsified solution, which was then injected into the samples. Compared with other surfactant-assisted emulsion methods, WLSEME uses much less surfactant. The linear range was 0.08-100 µg L(-1), and the LODs were 0.022-0.13 µg L(-1). The EFs ranged from 388 to 649. The relative recoveries were 86-114% for all three water specimens. Copyright © 2013 Elsevier B.V. All rights reserved.

Mathematical modeling of disperse two-phase flows

CERN Document Server

Morel, Christophe

2015-01-01

This book develops the theoretical foundations of disperse two-phase flows, which are characterized by the existence of bubbles, droplets or solid particles finely dispersed in a carrier fluid, which can be a liquid or a gas. Chapters clarify many difficult subjects, including modeling of the interfacial area concentration. Basic knowledge of the subjects treated in this book is essential to practitioners of Computational Fluid Dynamics for two-phase flows in a variety of industrial and environmental settings. The author provides a complete derivation of the basic equations, followed by more advanced subjects like turbulence equations for the two phases (continuous and disperse) and multi-size particulate flow modeling. As well as theoretical material, readers will discover chapters concerned with closure relations and numerical issues. Many physical models are presented, covering key subjects including heat and mass transfers between phases, interfacial forces and fluid particles coalescence and breakup, a...

AERMOD as a Gaussian dispersion model for planning tracer gas dispersion tests for landfill methane emission quantification

DEFF Research Database (Denmark)

Matacchiera, F.; Manes, C.; Beaven, R. P.

2018-01-01

that measurements are taken where the plumes of a released tracer-gas and landfill-gas are well-mixed. However, the distance at which full mixing of the gases occurs is generally unknown prior to any experimental campaign. To overcome this problem the present paper demonstrates that, for any specific TDM...

Investigation of liquid phase axial dispersion in Taylor bubble flow by radiotracer residence time distribution analysis

Directory of Open Access Journals (Sweden)

Jin J.H.

2013-05-01

Full Text Available A gas-liquid Taylor bubble flow occurs in small diameter channels in which gas bubbles are separated by slugs of pure liquid. This type of flow regime is well suited for solid catalyzed gas-liquid reactors in which the reaction efficiency is a strong function of axial dispersion in the regions of pure liquid. This paper presents an experimental study of liquid phase axial dispersion in a Taylor bubble flow developed in a horizontal tube using high speed photography and radiotracer residence time distribution (RTD analysis. A parametric dependence of axial dispersion on average volume fraction of gas phase was also investigated by varying the relative volumetric flow rates of the two phases. 137mBa produced from a 137Cs/137mBa radionuclide generator was used as radiotracer and measurements were made using the NaI(Tl scintillation detectors. Validation of 137mBa in the form of barium chloride as aqueous phase radiotracer was also carried out. Axial Dispersion Model (ADM was used to simulate the hydrodynamics of the system and the results of the experiment are presented. It was observed that the system is characterized by very high values of Peclet Number (Pe∼102 which reveals an approaching plug type flow. The experimental and model estimated values of mean residence times were observed in agreement with each other.

ATMOSPHERIC DYNAMICS OF AIR POLLUTION DISPERSION AND SUSTAINABLE ENVIRONMENT IN JOS-NIGERIA

Directory of Open Access Journals (Sweden)

Moses Eterigho Emetere

2017-01-01

Full Text Available The basic properties of chlorine were used to determine the dis persion patterns of the recent Jos explosion. The dynamic aerosols content model was us ed to affirm the eight kinds of dispersion patterns discussed in this text. The locati on of the victims showed that the dispersion at Jos was either linear or polynomial disp ersion. The dispersions are influenced by atmospheric ventilation, stagnation and recir culation. The last chlorine gas explosion follows the linear or polynomial dispers ion because of the current state of aerosol loadings in Jos. The aftermath effect of this kind of dispersion may be more threatening than the initial danger due to the chem ical formation of more dangerous compounds. The atmosphe ric conditions for the formati on of toxic compound were investigated using twelve years MERRA satellite o bservation. The degree of freedom of methane, carbon oxide and ozone was nearly uniform for the past five years. This means the next five years or more may be threa tening for life forms within the region. The installation of gas tracers within major locations in Jos was suggested to monitor the formation of dioxins in the atmosphere.

Plume dispersion and deposition processes of tracer gas and aerosols in short-distance experiments

International Nuclear Information System (INIS)

Taeschner, M.; Bunnenberg, C.

1988-01-01

Data used in this paper were extracted from field experiments carried out in France and Canada to study the pathway of elementary tritium after possible emissions from future fusion reactors and from short-range experiments with nutrient aerosols performed in a German forest in view of a therapy of damaged coniferous trees by foliar nutrition. Comparisons of dispersion parameters evaluated from the tritium field experiments show that in the case of the 30-min release the variations of the wind directions represent the dominant mechanism of lateral plume dispersion under unstable weather conditions. This corresponds with the observation that for the short 2-min emission the plume remains more concentrated during propagation, and the small lateral dispersion parameters typical for stable conditions have to be applied. The investigations on the dispersion of aerosol plumes into a forest boundary layer show that the Gaussian plume model can be modified by a windspeed factor to be valid for predictions on aerosol concentrations and depositions even in a structured topography like a forest

Development and Characterization of Gas Diffusion Layer Using Carbon Slurry Dispersed by Ammonium Lauryl Sulfate for Proton Exchange Member Fuel Cells

Science.gov (United States)

Villacorta, Rashida

Gas diffusion layers (GDLs) are a critical and essential part of proton exchange membrane fuel cells (PEMFCs). They carry out various important functions such as transportation of reactants to and from the reaction sites. The material properties and structural characteristics of the substrate and the microporous layer strongly influence fuel cell performance. The microporous layer of the GDLs was fabricated with the carbon slurry dispersed in water containing ammonium lauryl sulfate (ALS) using the wire rod coating method. GDLs were fabricated with different materials to compose the microporous layer and evaluated the effects on PEMFC power output performance. The consistency of the carbon slurry was achieved by adding 25 wt. % of PTFE, a binding agent with a 75:25 ratio of carbon (Pureblack and vapor grown carbon fiber). The GDLs were investigated in PEMFC under various relative humidity (RH) conditions using H2/O2 and H2/Air. GDLs were also fabricated with the carbon slurry dispersed in water containing sodium dodecyl sulfate (SDS) and multiwalled carbon nanotubes (MWCNTs) with isopropyl alcohol (IPA) based for fuel cell performance comparison. MWCNTs and SDS exhibits the highest performance at 60% and 70% RH with a peak power density of 1100 mW.cm-2 and 850 mW.cm-2 using air and oxygen as an oxidant. This means that the gas diffusion characteristics of these two samples were optimum at 60 and 70 % RH with high limiting current density range. It was also found that the composition of the carbon slurry, specifically ALS concentration has the highest peak power density of 1300 and 500mW.cm-2 for both H2/O 2 and H2/Air at 100% RH. However, SDS and MWCNTs demonstrates the lowest power density using air and oxygen as an oxidants at 100% RH.

A comparative study of gas-gas miscibility processes in underground gas storage reservoirs

Energy Technology Data Exchange (ETDEWEB)

Rafiee, M.M.; Schmitz, S. [DBI - Gastechnologisches Institut gGmbH, Freiberg (Germany)

2013-08-01

Intermixture of gases in underground gas reservoirs have had great weight for natural gas storage in UGS projects with substitution of cushion gas by inert gases or changing the stored gas quality or origin, as for the replacement of town gas by natural gas. It was also investigated during the last years for Enhanced Gas Recovery (EGR) and Carbon Capture and Storage (CCS) projects. The actual importance of its mechanisms is discussed for the H{sub 2} storage in Power to Gas to Power projects (PGP). In these approaches miscibility of the injected gas with the gas in place in the reservoir plays an important role in the displacement process. The conditions and parameters for the gas-gas displacement and mixing have been investigated in previous projects, as e.g. the miscibility of CO{sub 2} with natural gas (CLEAN). Furthermore the miscibility process of town gas with natural gas and sauer gas with sweet gas were also previously measured and compared in laboratory. The objective of this work is to investigate the miscibility of H{sub 2} injection into natural gas reservoirs using a compositional and a black oil reservoir simulator. Three processes of convection, dispersion and diffusion are considered precisely. The effect of gas miscibility is studied for both simulators and the results are compared to find optimum miscibility parameters. The findings of this work could be helpful for further pilot and field case studies to predict and monitor the changes in gas composition and quality. In future this monitoring might become more important when PGP together with H{sub 2}-UGS, as storage technology, will help to successfully implement the change to an energy supply from more renewable sources. Similarly the method confirms the use of the black oil simulator as an alternative for gas-gas displacement and sequestration reservoir simulation in comparison to the compositional simulator. (orig.)

The Influence of subway climatology on gas dispersion and the effectiveness of guided evacuations in a complex subway station

Directory of Open Access Journals (Sweden)

Markus Brüne

2016-09-01

Full Text Available This paper discusses a strategy that integrates data from tracer gas experiments with results from pedestrian simulation software in the evaluation of different evacuation procedures for subway stations in response to a fire or a terrorist attack with chemical, biological, radiological, nuclear and enhanced conventional weapons (CBRNE. The study demonstrates that by combining the two data sets a greater understanding of the impact of different evacuations routes on an evacuee's health is gained. It is shown that by controlling the routes pedestrians would use to exit a subway station, the number of fatalities and evacuees with long term health issues can be reduced. It is highlighted that a dynamic evacuation guiding system based on subway climatology would take into account the source of the toxin, the resulting dispersal of gas, smoke, etc. and the subway climatology at the time. In doing so, it would be possible to identify the most endangered areas and guide passengers via an adaptive escape route using audio and visual techniques. Information on the evolution of the emergency situation could also simultaneously be relayed back to the rescue forces to help to plan the rescue and evacuation procedures and optimise the deployment of the search and rescue teams.

Irradiation behavior of U 6Mn-Al dispersion fuel elements

Science.gov (United States)

Meyer, M. K.; Wiencek, T. C.; Hayes, S. L.; Hofman, G. L.

2000-02-01

Irradiation testing of U 6Mn-Al dispersion fuel miniplates was conducted in the Oak Ridge Research Reactor (ORR). Post-irradiation examination showed that U 6Mn in an unrestrained plate configuration performs similarly to U 6Fe under irradiation, forming extensive and interlinked fission gas bubbles at a fission density of approximately 3×10 27 m-3. Fuel plate failure occurs by fission gas pressure driven `pillowing' on continued irradiation.

Overview of the phase diagram of ionic magnetic colloidal dispersions

International Nuclear Information System (INIS)

Cousin, F.; Dubois, E.; Cabuil, V.; Boue, F.; Perzynski, R.

2001-01-01

We study ionic magnetic colloidal dispersions, which are constituted of γ-Fe 2 O 3 nanoparticles dispersed in water, and stabilized with electrostatic interparticle repulsion. The phase diagram PV versus Φ (P: osmotic pressure, V: particle volume, Φ: particle volume fraction) is explored, especially in the range of high Π and high Φ. The osmotic pressure P of the colloidal dispersion is known either by a measurement either because it is imposed during the sample preparation by osmotic compression. The structure of the colloidal dispersion is determined from Small Angle Neutron Scattering. Two regimes can be distinguished. At high pressure, fluid and solid phases can exist. Their structure is governed by strong electrostatic repulsion, the range of which is here evaluated. At low pressure, gas, liquid and glassy solids can exist. Their structure results from a sticky hard sphere potential. (author)

Srv mediated dispersal of streptococcal biofilms through SpeB is observed in CovRS+ strains.

Directory of Open Access Journals (Sweden)

Kristie L Connolly

Full Text Available Group A Streptococcus (GAS is a human specific pathogen capable of causing both mild infections and severe invasive disease. We and others have shown that GAS is able to form biofilms during infection. That is to say, they form a three-dimensional, surface attached structure consisting of bacteria and a multi-component extracellular matrix. The mechanisms involved in regulation and dispersal of these GAS structures are still unclear. Recently we have reported that in the absence of the transcriptional regulator Srv in the MGAS5005 background, the cysteine protease SpeB is constitutively produced, leading to increased tissue damage and decreased biofilm formation during a subcutaneous infection in a mouse model. This was interesting because MGAS5005 has a naturally occurring mutation that inactivates the sensor kinase domain of the two component regulatory system CovRS. Others have previously shown that strains lacking covS are associated with decreased SpeB production due to CovR repression of speB expression. Thus, our results suggest the inactivation of srv can bypass CovR repression and lead to constitutive SpeB production. We hypothesized that Srv control of SpeB production may be a mechanism to regulate biofilm dispersal and provide a mechanism by which mild infection can transition to severe disease through biofilm dispersal. The question remained however, is this mechanism conserved among GAS strains or restricted to the unique genetic makeup of MGAS5005. Here we show that Srv mediated control of SpeB and biofilm dispersal is conserved in the invasive clinical isolates RGAS053 (serotype M1 and MGAS315 (serotype M3, both of which have covS intact. This work provides additional evidence that Srv regulated control of SpeB may mediate biofilm formation and dispersal in diverse strain backgrounds.

A "Greenhouse Gas" Experiment for the Undergraduate Laboratory

Science.gov (United States)

Gomez, Elaine; Paul, Melissa; Como, Charles; Barat, Robert

2014-01-01

This experiment and analysis offer an effective experience in greenhouse gas reduction. Ammoniated water is flowed counter-current to a simulated flue gas of air and CO2 in a packed column. The gaseous CO2 concentrations are measured with an on-line, non- dispersive, infrared analyzer. Column operating parameters include total gas flux, dissolved…

Design of compact dispersion interferometer with a high efficiency nonlinear crystal and a low power CO2 laser

Science.gov (United States)

Akiyama, T.; Yoshimura, S.; Tomita, K.; Shirai, N.; Murakami, T.; Urabe, K.

2017-12-01

When the electron density of a plasma generated in high pressure environment is measured by a conventional interferometer, the phase shifts due to changes of the neutral gas density cause significant measurement errors. A dispersion interferometer, which measures the phase shift that arises from dispersion of medium between the fundamental and the second harmonic wavelengths of laser light, can suppress the measured phase shift due to the variations of neutral gas density. In recent years, the CO2 laser dispersion interferometer has been applied to the atmospheric pressure plasmas and its feasibility has been demonstrated. By combining a low power laser and a high efficiency nonlinear crystal for the second harmonic component generation, a compact dispersion interferometer can be designed. The optical design and preliminary experiments are conducted.

A new NAMA framework for dispersed energy end-use sectors

DEFF Research Database (Denmark)

Cheng, Chia-Chin

2010-01-01

This paper presents a new approach for a nationally appropriate mitigation actions (NAMA) framework that can unlock the huge potential for greenhouse gas mitigation in dispersed energy end-use sectors in developing countries; specifically, the building sector and the industrial sector. These two ...

High heat load properties of TiC dispersed Mo alloys

International Nuclear Information System (INIS)

Tokunaga, Kazutoshi; Yoshida, Naoaki; Miura, Yasushi; Kurishita, Hiroaki; Kitsunai, Yuji; Kayano, Hideo.

1996-01-01

Electron beam high heat load experiment of new developed three kinds of TiC dispersed Mo alloys (Mo-0.1wt%TiC, Mo-0.5wt%TiC and Mo-1.0wt%TiC) was studied so as to evaluate it's high heat load at using as the surface materials of divertor. The obtained results indicated that cracks were not observed by embrittlement by recrystallization until about 2200degC of surface temperature and the gas emission properties were not different from sintered molibdenum. However, at near melting point, deep cracks on grain boundary and smaller gas emission than that of sintered Mo were observed. So that, we concluded that TiC dispersed Mo alloy was good surface materials used under the conditions of the stationary heat flux and less than the melting point, although not good one to be melted under nonstationary large heat flux. (S.Y.)

Dispersion and exposure of sour gas flare emissions

International Nuclear Information System (INIS)

Davies, M.

2002-01-01

This presentation described the implications of flare research project findings with reference to reduced combustion efficiency, stack plume down wash and minor species. A plume model shows that reduced combustion efficiency decreases the energy available for plume rise. Reduced combustion may therefore decrease H 2 S to SO 2 conversion. Stack plume down wash can decrease plume rise under high wind speed conditions, and in extreme cases can also preclude any plume rise. Minor species include vapour phase emissions of polynuclear aromatic hydrocarbons (PAH), benzene, toluene, ethyl-benzene and xylenes (BTEX), and aldehydes. They also include particulate phase emissions such as soot and PAH. Observed concentrations of minor species were presented along with predicted vapour phase concentrations and particulate phase emissions. The standard modelling approaches used in this study included the Gaussian plume model, flame height, plume rise and dispersion. figs

Two-Fluid Models for Simulating Dispersed Multiphase Flows-A Review

Directory of Open Access Journals (Sweden)

L.X. Zhou

2009-01-01

Full Text Available The development of two-fluid models for simulating dispersed multiphase flows (gas-particle, gas-droplet, bubble-liquid, liquid-particle flows by the present author within the last 20 years is systematically reviewed. The two-fluid models based on Reynolds expansion, time averaging and mass-weighed averaging, and also PDF transport equations are described. Different versions of two-phase turbulence models, including the unified second-order moment (USM and k-ε-kp models, the DSM-PDF model, the SOM-MC model, the nonlinear k-e-kp model, and the USM-Θ model for dense gas-particle flows and their application and experimental validation are discussed.

Comparison of some dispersion-corrected and traditional functionals with CCSD(T) and MP2 ab initio methods: Dispersion, induction, and basis set superposition error

Science.gov (United States)

Roy, Dipankar; Marianski, Mateusz; Maitra, Neepa T.; Dannenberg, J. J.

2012-10-01

We compare dispersion and induction interactions for noble gas dimers and for Ne, methane, and 2-butyne with HF and LiF using a variety of functionals (including some specifically parameterized to evaluate dispersion interactions) with ab initio methods including CCSD(T) and MP2. We see that inductive interactions tend to enhance dispersion and may be accompanied by charge-transfer. We show that the functionals do not generally follow the expected trends in interaction energies, basis set superposition errors (BSSE), and interaction distances as a function of basis set size. The functionals parameterized to treat dispersion interactions often overestimate these interactions, sometimes by quite a lot, when compared to higher level calculations. Which functionals work best depends upon the examples chosen. The B3LYP and X3LYP functionals, which do not describe pure dispersion interactions, appear to describe dispersion mixed with induction about as accurately as those parametrized to treat dispersion. We observed significant differences in high-level wavefunction calculations in a basis set larger than those used to generate the structures in many of the databases. We discuss the implications for highly parameterized functionals based on these databases, as well as the use of simple potential energy for fitting the parameters rather than experimentally determinable thermodynamic state functions that involve consideration of vibrational states.

SAGE measurements of the stratospheric aerosol dispersion and loading from the Soufriere Volcano

Science.gov (United States)

Mccormick, M. P.; Kent, G. S.; Yue, G. K.; Cunnold, D. M.

1981-01-01

Explosions of the Soufriere volcano on the Caribbean Island of St. Vincent reduced two major stratospheric plumes which the stratospheric aerosol and gas experiment (SAGE) satellite tracked to West Africa and the North Atlantic Ocean. The total mass of the stratospheric ejecta measured is less than 0.5% of the global stratospheric aerosol burden. No significant temperature or climate perturbation is expected. It is found that the movement and dispersion of the plumes agree with those deduced from high altitude meteorological data and dispersion theory. The stratospheric aerosol dispersion and loading from the Soufrier volcano was measured.

Technology and products of gas companies; Gas gaisha no Technology and Products

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-06-10

This paper presents the latest technology and products of gas companies. `Newly developed gas table for one-push automatic fish broiling` of Tokyo Gas Co. `Catalytic technology for decomposing dioxin generated by incinerator to make it harmless` of Osaka Gas Co. `Newly developed strong and kindly shower head` of Tokyo Gas Co. By laying fish on a sensor in a grill and appropriately setting upper and lower heating levers, user can skillfully broil fish only by pushing an ignition button. A temperature sensor attached to the center of a grill catches a change in surface temperature of fish, and automatically sets an appropriate broiling time according to the kind and volume of fish. A finish buzzer and automatic extinction mechanism are prepared. The technology decomposes dioxin in exhaust gas of incinerators to make it harmless. The catalyst is prepared by dispersing noble metal or oxide of several angstroms into activated carbon fibers. The shower head can switch hot water power by a control handle

Irradiation behavior of U{sub 6}Mn-Al dispersion fuel elements

Energy Technology Data Exchange (ETDEWEB)

Meyer, M.K. E-mail: mitchell.meyer@anl.gov; Wiencek, T.C.; Hayes, S.L.; Hofman, G.L

2000-04-01

Irradiation testing of U{sub 6}Mn-Al dispersion fuel miniplates was conducted in the Oak Ridge Research Reactor (ORR). Post-irradiation examination showed that U{sub 6}Mn in an unrestrained plate configuration performs similarly to U{sub 6}Fe under irradiation, forming extensive and interlinked fission gas bubbles at a fission density of approximately 3x10{sup 27} m{sup -3}. Fuel plate failure occurs by fission gas pressure driven 'pillowing' on continued irradiation.

Transmission electron microscopy characterization of irradiated U-7Mo/Al-2Si dispersion fuel

International Nuclear Information System (INIS)

Gan, J.; Keiser, D.D.; Wachs, D.M.; Robinson, A.B.; Miller, B.D.; Allen, T.R.

2010-01-01

The plate-type dispersion fuels, with the atomized U(Mo) fuel particles dispersed in the Al or Al alloy matrix, are being developed for use in research and test reactors worldwide. It is found that the irradiation performance of a plate-type dispersion fuel depends on the radiation stability of the various phases in a fuel plate. Transmission electron microscopy was performed on a sample (peak fuel mid-plane temperature ∼109 deg. C and fission density ∼4.5 x 10 27 f m -3 ) taken from an irradiated U-7Mo dispersion fuel plate with Al-2Si alloy matrix to investigate the role of Si addition in the matrix on the radiation stability of the phase(s) in the U-7Mo fuel/matrix interaction layer. A similar interaction layer that forms in irradiated U-7Mo dispersion fuels with pure Al matrix has been found to exhibit poor irradiation stability, likely as a result of poor fission gas retention. The interaction layer for both U-7Mo/Al-2Si and U-7Mo/Al fuels is observed to be amorphous. However, unlike the latter, the amorphous layer for the former was found to effectively retain fission gases in areas with high Si concentration. When the Si concentration becomes relatively low, the fission gas bubbles agglomerate into fewer large pores. Within the U-7Mo fuel particles, a bubble superlattice ordered as fcc structure and oriented parallel to the bcc metal lattice was observed where the average bubble size and the superlattice constant are 3.5 nm and 11.5 nm, respectively. The estimated fission gas inventory in the bubble superlattice correlates well with the fission density in the fuel.

INFLUENCE OF FUEL-MATRIX INTERACTION ON THE BREAKAWAY SWELLING OF U-MO DISPERSION FUEL IN AL

OpenAIRE

HO JIN RYU; YEON SOO KIM

2014-01-01

In order to advance understanding of the breakaway swelling behavior of U-Mo/Al dispersion fuel under a high-power irradiation condition, the effects of fuel-matrix interaction on the fuel performance of U-Mo/Al dispersion fuel were investigated. Fission gas release into large interfacial pores between interaction layers and the Al matrix was analyzed using both mechanistic models and observations of the post-irradiation examination results of U-Mo dispersion fuels. Using the model prediction...

Compound Method to Disperse CaCO3 Nanoparticles to Nano-Size in Water.

Science.gov (United States)

Gu, Sui; Cai, Jihua; Wang, Jijun; Yuan, Ye; Chang, Dewu; Chikhotkin, Viktor F

2015-12-01

The invalidation of CaCO3 nanoparticles (nCaCO3) is often caused by the fact of agglomeration and inhomogeneous dispersion which limits its application into water-based drilling muds for low permeability reservoirs such as coalbed methane reservoir and shale gas/oil reservoir. Effective methods to disperse nCaCO3 to nano-size (≤ 100 nm) in water have seldom been reported. Here we developed a compound method containing mechanical stirring, ultrasonic treatment, the use of surfactant and stabilizer to disperse nCaCO3 in water. It comprises the steps adding 2% nCaCO3, 1% sodium dodecyl sulfonate (SDS), 2% cetyltrimethyl ammonium bromide (CTAB), 2% OP-10, 3% to 4% biopolymer (XC) in water successively, stirring it at a shear rate of 6000 to 8000 r/min for 15 minutes and treating it with ultrasonic at a frequency of 28 KHz for 30 to 40 minutes. The dispersed nCaCO3 was characterized with scanning electron microscope (SEM), transmission electron microscope (TEM) and particle size distribution (PSD) tests. We found that nCaCO3 could be dispersed to below 100 nm in water and the medium value of nCaCO3 was below 50 nm. This method paved the way for the utilization of nCaCO3 in drilling fluid and completion fluid for low permeability reservoirs such as coal seams and shale gas/oil formations.

Dispersant testing : a study on analytical test procedures

International Nuclear Information System (INIS)

Fingas, M.F.; Fieldhouse, B.; Wang, Z.; Environment Canada, Ottawa, ON

2004-01-01

Crude oil is a complex mixture of hydrocarbons, ranging from small, volatile compounds to very large, non-volatile compounds. Analysis of the dispersed oil is crucial. This paper described Environment Canada's ongoing studies on various traits of dispersants. In particular, it describes small studies related to dispersant effectiveness and methods to improve analytical procedures. The study also re-evaluated the analytical procedure for the Swirling Flask Test, which is now part of the ASTM standard procedure. There are new and improved methods for analyzing oil-in-water using gas chromatography (GC). The methods could be further enhanced by integrating the entire chromatogram rather than just peaks. This would result in a decrease in maximum variation from 5 per cent to about 2 per cent. For oil-dispersant studies, the surfactant-dispersed oil hydrocarbons consist of two parts: GC-resolved hydrocarbons and GC-unresolved hydrocarbons. This study also tested a second feature of the Swirling Flask Test in which the side spout was tested and compared with a new vessel with a septum port instead of a side spout. This decreased the variability as well as the energy and mixing in the vessel. Rather than being a variation of the Swirling Flask Test, it was suggested that a spoutless vessel might be considered as a completely separate test. 7 refs., 2 tabs., 4 figs

Investigation of Factors Influencing Dispersion of Liquid Hydrocarbons in Porous Media

Directory of Open Access Journals (Sweden)

Hussain Ali Baker

2016-08-01

Full Text Available An experimental work has been done to study the major factors that affect the axial dispersion of some hydrocarbons during liquid-liquid miscible displacement. Kerosene and gas oil are used as displacing phase while seven liquid hydrocarbons of high purity represent the displaced phase, three of the liquids are aromatics and the rest are of paraffinic base. In conducting the experiments, two packed beds of different porosity and permeability are used as porous media. The results showed that the displacement process is not a piston flow, breakthrough of displacing fluids are shown before one pore volume has been injected. The processes are stable with no evidence of viscous fingering. Dispersion model as adapted by Brigham et.al (1961 is used to determine the axial dispersion coefficient of displacing fluid. The results show an increasing in dispersion coefficient as the interstitial velocity and viscosity ratio increases.

Effect of the Duration of Meteorological Data Collection on the Atmospheric Dispersion Assessment

International Nuclear Information System (INIS)

Choi, Yoo-mi; Kim, Eun-hee

2017-01-01

This study regards the duration of meteorological data record for a prospective assessment of the environmental impact of gas release from Kori nuclear power plant under normal operation. We compared the atmospheric dispersion factors obtained by employing the meteorological data from 2- and 5-year durations with the corresponding values obtained by employing yearly meteorological data in the period of 2001 to 2008. Influence of the duration of meteorological data collection on short-term atmospheric dispersion factors was previously studied. In this study, long-term dispersion factors were assessed to investigate the influence of the duration of meteorological data collection on the assessment of environmental impact by gas release from Kori nuclear power plant under normal operation. We counted how many yearly meteorological conditions would be represented by 2 or 5 years of long-term data collection. The distribution of shaded cells in Tables I and II indicated that some of the yearly meteorological condition could be properly represented by the conditions averaged over 2- or 5-year durations.

Gas kinematics in FIRE simulated galaxies compared to spatially unresolved H I observations

Science.gov (United States)

El-Badry, Kareem; Bradford, Jeremy; Quataert, Eliot; Geha, Marla; Boylan-Kolchin, Michael; Weisz, Daniel R.; Wetzel, Andrew; Hopkins, Philip F.; Chan, T. K.; Fitts, Alex; Kereš, Dušan; Faucher-Giguère, Claude-André

2018-06-01

The shape of a galaxy's spatially unresolved, globally integrated 21-cm emission line depends on its internal gas kinematics: galaxies with rotationally supported gas discs produce double-horned profiles with steep wings, while galaxies with dispersion-supported gas produce Gaussian-like profiles with sloped wings. Using mock observations of simulated galaxies from the FIRE project, we show that one can therefore constrain a galaxy's gas kinematics from its unresolved 21-cm line profile. In particular, we find that the kurtosis of the 21-cm line increases with decreasing V/σ and that this trend is robust across a wide range of masses, signal-to-noise ratios, and inclinations. We then quantify the shapes of 21-cm line profiles from a morphologically unbiased sample of ˜2000 low-redshift, H I-detected galaxies with Mstar = 107-11 M⊙ and compare to the simulated galaxies. At Mstar ≳ 1010 M⊙, both the observed and simulated galaxies produce double-horned profiles with low kurtosis and steep wings, consistent with rotationally supported discs. Both the observed and simulated line profiles become more Gaussian like (higher kurtosis and less-steep wings) at lower masses, indicating increased dispersion support. However, the simulated galaxies transition from rotational to dispersion support more strongly: at Mstar = 108-10 M⊙, most of the simulations produce more Gaussian-like profiles than typical observed galaxies with similar mass, indicating that gas in the low-mass simulated galaxies is, on average, overly dispersion supported. Most of the lower-mass-simulated galaxies also have somewhat lower gas fractions than the median of the observed population. The simulations nevertheless reproduce the observed line-width baryonic Tully-Fisher relation, which is insensitive to rotational versus dispersion support.

Fate of dispersants associated with the deepwater horizon oil spill.

Science.gov (United States)

Kujawinski, Elizabeth B; Kido Soule, Melissa C; Valentine, David L; Boysen, Angela K; Longnecker, Krista; Redmond, Molly C

2011-02-15

Response actions to the Deepwater Horizon oil spill included the injection of ∼771,000 gallons (2,900,000 L) of chemical dispersant into the flow of oil near the seafloor. Prior to this incident, no deepwater applications of dispersant had been conducted, and thus no data exist on the environmental fate of dispersants in deepwater. We used ultrahigh resolution mass spectrometry and liquid chromatography with tandem mass spectrometry (LC/MS/MS) to identify and quantify one key ingredient of the dispersant, the anionic surfactant DOSS (dioctyl sodium sulfosuccinate), in the Gulf of Mexico deepwater during active flow and again after flow had ceased. Here we show that DOSS was sequestered in deepwater hydrocarbon plumes at 1000-1200 m water depth and did not intermingle with surface dispersant applications. Further, its concentration distribution was consistent with conservative transport and dilution at depth and it persisted up to 300 km from the well, 64 days after deepwater dispersant applications ceased. We conclude that DOSS was selectively associated with the oil and gas phases in the deepwater plume, yet underwent negligible, or slow, rates of biodegradation in the affected waters. These results provide important constraints on accurate modeling of the deepwater plume and critical geochemical contexts for future toxicological studies.

Investigation of natural gas plume dispersion using mobile observations and large eddy simulations

Science.gov (United States)

Caulton, Dana R.; Li, Qi; Golston, Levi; Pan, Da; Bou-Zeid, Elie; Fitts, Jeff; Lane, Haley; Lu, Jessica; Zondlo, Mark A.

2016-04-01

Recent work suggests the distribution of methane emissions from fracking operations is skewed with a small percentage of emitters contributing a large proportion of the total emissions. These sites are known as 'super-emitters.' The Marcellus shale, the most productive natural gas shale field in the United States, has received less intense focus for well-level emissions and is here used as a test site for targeted analysis between current standard trace-gas advection practices and possible improvements via advanced modeling techniques. The Marcellus shale is topographically complex, making traditional techniques difficult to implement and evaluate. For many ground based mobile studies, the inverse Gaussian plume method (IGM) is used to produce emission rates. This method is best applied to well-mixed plumes from strong point sources and may not currently be well-suited for use with disperse weak sources, short-time frame measurements or data collected in complex terrain. To assess the quality of IGM results and to improve source-strength estimations, a robust study that combines observational data with a hierarchy of models of increasing complexity will be presented. The field test sites were sampled with multiple passes using a mobile lab as well as a stationary tower. This mobile lab includes a Garmin GPS unit, Vaisala weather station (WTX520), LICOR 7700 CH4 open path sensor and LICOR 7500 CO2/H2O open path sensor. The sampling tower was constructed consisting of a Metek uSonic-3 Class A sonic anemometer, and an additional LICOR 7700 and 7500. Data were recorded for at least one hour at these sites. The modeling will focus on large eddy simulations (LES) of the wind and CH4 concentration fields for these test sites. The LES model used 2 m horizontal and 1 m vertical resolution and was integrated in time for 45 min for various test sites under stable, neutral and unstable conditions. It is here considered as the reference to which various IGM approaches can be

DEVELOPMENT OF MORE-EFFICIENT GAS FLOODING APPLICABLE TO SHALLOW RESERVOIRS

Energy Technology Data Exchange (ETDEWEB)

William R. Rossen; Russell T. Johns; Gary A. Pope

2003-08-21

The objective of this research is to widen the applicability of gas flooding to shallow oil reservoirs by reducing the pressure required for miscibility using gas enrichment and increasing sweep efficiency with foam. Task 1 examines the potential for improved oil recovery with enriched gases. Subtask 1.1 examines the effect of dispersion processes on oil recovery and the extent of enrichment needed in the presence of dispersion. Subtask 1.2 develops a fast, efficient method to predict the extent of enrichment needed for crude oils at a given pressure. Task 2 develops improved foam processes to increase sweep efficiency in gas flooding. Subtask 2.1 comprises mechanistic experimental studies of foams with N2 gas. Subtask 2.2 conducts experiments with CO{sub 2} foam. Subtask 2.3 develops and applies a simulator for foam processes in field application.

Experiments on melt dispersion with lateral failure in the bottom head of the pressure vessel

Energy Technology Data Exchange (ETDEWEB)

Meyer, L.; Gargallo, M. [Forschungszentrum Karlsruhe, Institut fur Kern-und Energietechnik, Karlsruhe (Germany)

2001-07-01

Melt dispersion experiments with lateral failure in the bottom head were carried out in a 1:18 scaled annular cavity design under low pressure conditions. Water and a bismuth alloy were used as melt simulant material and nitrogen as driving gas. With lateral breaches the liquid height in the lower head relative to the upper and lower edge of the breach is an additional parameter for the dispersion process. Shifting the break from the central position towards the side of the lower head leads to smaller melt dispersion, and a larger breach size does not necessarily lead to a larger dispersed melt fraction. (author)

Improvements in or relating to handling of flue gas

International Nuclear Information System (INIS)

Ingham, R.V.

1986-01-01

The patent describes improvements in the method for handling flue gas from the burning of fossil fuels. The method relates to cleaning the flue gas, from which the sulphur compounds are removed. The gas in then heated by heat derived from a nuclear source, which may be nuclear waste. The heat treatment gives efficient atmospheric dispersion from the chimney. (U.K.)

Coal beneficiation by gas agglomeration

Science.gov (United States)

Wheelock, Thomas D.; Meiyu, Shen

2003-10-14

Coal beneficiation is achieved by suspending coal fines in a colloidal suspension of microscopic gas bubbles in water under atmospheric conditions to form small agglomerates of the fines adhered by the gas bubbles. The agglomerates are separated, recovered and resuspended in water. Thereafter, the pressure on the suspension is increased above atmospheric to deagglomerate, since the gas bubbles are then re-dissolved in the water. During the deagglomeration step, the mineral matter is dispersed, and when the pressure is released, the coal portion of the deagglomerated gas-saturated water mixture reagglomerates, with the small bubbles now coming out of the solution. The reagglomerate can then be separated to provide purified coal fines without the mineral matter.

Determination of valproic acid in human plasma using dispersive liquid-liquid microextraction followed by gas chromatography-flame ionization detection

Science.gov (United States)

Fazeli-Bakhtiyari, Rana; Panahi-Azar, Vahid; Sorouraddin, Mohammad Hossein; Jouyban, Abolghasem

2015-01-01

Objective(s): Dispersive liquid-liquid microextraction coupled with gas chromatography (GC)-flame ionization detector was developed for the determination of valproic acid (VPA) in human plasma. Materials and Methods: Using a syringe, a mixture of suitable extraction solvent (40 µl chloroform) and disperser (1 ml acetone) was quickly added to 10 ml of diluted plasma sample containing VPA (pH, 1.0; concentration of NaCl, 4% (w/v)), resulting in a cloudy solution. After centrifugation (6000 rpm for 6 min), an aliquot (1 µl) of the sedimented organic phase was removed using a 1-µl GC microsyringe and injected into the GC system for analysis. One variable at a time optimization method was used to study various parameters affecting the extraction efficiency of target analyte. Then, the developed method was fully validated for its accuracy, precision, recovery, stability, and robustness. Results: Under the optimum extraction conditions, good linearity range was obtained for the calibration graph, with correlation coefficient higher than 0.998. Limit of detection and lower limit of quantitation were 3.2 and 6 μg/ml, respectively. The relative standard deviations of intra and inter-day analysis of examined compound were less than 11.5%. The relative recoveries were found in the range of 97 to 107.5%. Finally, the validated method was successfully applied to the analysis of VPA in patient sample. Conclusion: The presented method has acceptable levels of precision, accuracy and relative recovery and could be used for therapeutic drug monitoring of VPA in human plasma. PMID:26730332

Matrix solid-phase dispersion followed by gas chromatography tandem mass spectrometry for the determination of benzotriazole UV absorbers in sediments.

Science.gov (United States)

Carpinteiro, I; Abuín, B; Ramil, M; Rodríguez, I; Cela, R

2012-01-01

A cost-effective and low solvent consumption method, based on the matrix solid-phase dispersion (MSPD) technique, for the determination of six benzotriazole UV absorbers in sediments is presented. Sieved samples (0.5 g) were first mixed in a mortar with a solid sorbent and then transferred to a polypropylene syringe containing a layer of clean-up co-sorbent. Analytes were eluted with a suitable solvent and further determined by gas chromatography with tandem mass spectrometry (GC-MS/MS). Under final conditions, diatomaceous earth and silica, deactivated to 10%, were used as inert dispersant and clean-up co-sorbent, respectively. Analytes were recovered using just 5 mL of dichloromethane, and this extract was concentrated and exchanged to 1 mL of isooctane. Further removal of co-extracted sulphur was achieved adding activated copper powder to final extracts, which were stored overnight, before injection in the GC-MS/MS system. The accuracy of the method was assessed with river and marine sediment samples showing different carbon contents and spiked at different concentrations in the range from 40 to 500 ng g(-1). Recoveries varied between 78% and 110% with associated standard deviations below 14%. The limits of quantification of the method stayed between 3 and 15 ng g(-1). Levels of target compounds in sediment samples ranged from not detected up to a maximum of 56 ng g(-1) for Tinuvin 328.

Mechanical and Tribological Characteristics of TIG Hardfaced Dispersive Layer by Reinforced with Particles Extruded Aluminium

Directory of Open Access Journals (Sweden)

R. Dimitrova

2017-05-01

Full Text Available The article presents the results of the implemented technology for generation of hardfaced dispersive layers obtained by additive material containing reinforcing phase of non-metal particles. The wear resistant coatings are deposited on pure aluminium metal matrix by shielded gas metal-arc welding applying tungsten inert gas (TIG with extruded aluminium wire reinforced by particles as additive material. Wire filler is produced by extrusion of a pack containing metalized and plated by flux micro/nano SiC particles. The metalized particles implanting in the metal matrix and its dispersive hardfacing are realized by solid-state welding under conditions of hot plastic deformation. Tribological characteristics are studied of the hardfaced layers of dispersive reinforced material on pure aluminium metal matrix with and without flux. Hardness profiles of the hardfaced layers are determined by nanoindentation. The surface layers are studied by means of Scanning Electron Microscopy (SEM and Energy Dispersive X-ray (EDX analysis. Increase by 15-31 % of the wear resistance of the hardfaced layers and 30-40 % of their hardness was found, which is due to the implanted in the layer reinforcing phase of metalized micro/nano SiC particles.

Spatial stochasticity and non-continuum effects in gas flows

Energy Technology Data Exchange (ETDEWEB)

Dadzie, S. Kokou, E-mail: k.dadzie@glyndwr.ac.uk [Mechanical and Aeronautical Engineering, Glyndwr University, Mold Road, Wrexham LL11 2AW (United Kingdom); Reese, Jason M., E-mail: jason.reese@strath.ac.uk [Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom)

2012-02-06

We investigate the relationship between spatial stochasticity and non-continuum effects in gas flows. A kinetic model for a dilute gas is developed using strictly a stochastic molecular model reasoning, without primarily referring to either the Liouville or the Boltzmann equations for dilute gases. The kinetic equation, a stochastic version of the well-known deterministic Boltzmann equation for dilute gas, is then associated with a set of macroscopic equations for the case of a monatomic gas. Tests based on a heat conduction configuration and sound wave dispersion show that spatial stochasticity can explain some non-continuum effects seen in gases. -- Highlights: ► We investigate effects of molecular spatial stochasticity in non-continuum regime. ► Present a simplify spatial stochastic kinetic equation. ► Present a spatial stochastic macroscopic flow equations. ► Show effects of the new model on sound wave dispersion prediction. ► Show effects of the new approach in density profiles in a heat conduction.

Dispersions of silica nanoparticles in ionic liquids investigated with advanced rheology

International Nuclear Information System (INIS)

Wittmar, Alexandra; Ruiz-Abad, David; Ulbricht, Mathias

2012-01-01

The colloidal stabilities of dispersions of unmodified and surface-functionalized SiO 2 nanoparticles in hydrophobic and hydrophilic imidazolium-based ionic liquids were studied with advanced rheology at three temperatures (25, 100, and 200 °C). The rheological behavior of the dispersions was strongly affected by the ionic liquids hydrophilicity, by the nanoparticles surface, by the concentration of the nanoparticles in the dispersion as well as by the temperature. The unmodified hydrophilic nanoparticles showed a better compatibility with the hydrophilic ionic liquid. The SiO 2 surface functionalization with hydrophobic groups clearly improved the colloidal stability of the dispersions in the hydrophobic ionic liquid. The temperature increase was found to lead to a destabilization in all studied systems, especially at higher concentrations. The results of this study imply that ionic liquids with tailored properties could be used in absorbers directly after reactors for gas-phase synthesis of nanoparticles or/and as solvents for their further surface functionalization without agglomeration or aggregation.

Surface functionalization of microwave plasma-synthesized silica nanoparticles for enhancing the stability of dispersions

Science.gov (United States)

Sehlleier, Yee Hwa; Abdali, Ali; Schnurre, Sophie Marie; Wiggers, Hartmut; Schulz, Christof

2014-08-01

Gas phase-synthesized silica nanoparticles were functionalized with three different silane coupling agents (SCAs) including amine, amine/phosphonate and octyltriethoxy functional groups and the stability of dispersions in polar and non-polar dispersing media such as water, ethanol, methanol, chloroform, benzene, and toluene was studied. Fourier transform infrared spectroscopy showed that all three SCAs are chemically attached to the surface of silica nanoparticles. Amine-functionalized particles using steric dispersion stabilization alone showed limited stability. Thus, an additional SCA with sufficiently long hydrocarbon chains and strong positively charged phosphonate groups was introduced in order to achieve electrosteric stabilization. Steric stabilization was successful with hydrophobic octyltriethoxy-functionalized silica nanoparticles in non-polar solvents. The results from dynamic light scattering measurements showed that in dispersions of amine/phosphonate- and octyltriethoxy-functionalized silica particles are dispersed on a primary particle level. Stable dispersions were successfully prepared from initially agglomerated nanoparticles synthesized in a microwave plasma reactor by designing the surface functionalization.

Method for the simultaneous determination of monoaromatic and polycyclic aromatic hydrocarbons in industrial effluents using dispersive liquid-liquid microextraction with gas chromatography-mass spectrometry.

Science.gov (United States)

Makoś, Patrycja; Fernandes, André; Boczkaj, Grzegorz

2018-02-23

We present a new method for simultaneous determination of 22 monoaromatic and polycyclic aromatic hydrocarbons in postoxidative effluents from the production of petroleum bitumen using dispersive liquid-liquid microextraction coupled to gas chromatography and mass spectrometry. The eight extraction parameters including the type and volume of extraction and disperser solvent, pH, salting out effect, extraction, and centrifugation time were optimized. The low detection limit ranging from 0.36 to 28 μg/L, limit of quantitation (1.1-84 μg/L), good reproducibility, and wide linear ranges, as well as the recoveries ranging from 71.74 to 114.67% revealed that the new method allows the determination of aromatic hydrocarbons at low concentration levels in industrial effluents having a very complex composition. The developed method was applied to the determination of content of mono- and polycyclic aromatic hydrocarbons in samples of raw postoxidative effluents in which 15 compounds were identified at concentrations ranging from 1.21 to 1017.0 μg/L as well as in effluents after chemical treatment. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of fuel-matrix interaction on the breakaway swelling of U-Mo dispersion fuel in Al

Energy Technology Data Exchange (ETDEWEB)

Ryu, Ho Jin [Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Yeon Soo [Nuclear Engineering Division, Argonne National Laboratory, Arogonne (United States)

2014-04-15

In order to advance understanding of the breakaway swelling behavior of U-Mo/Al dispersion fuel under a high-power irradiation condition, the effects of fuel-matrix interaction on the fuel performance of U-Mo/Al dispersion fuel were investigated. Fission gas release into large interfacial pores between interaction layers and the Al matrix was analyzed using both mechanistic models and observations of the post-irradiation examination results of U-Mo dispersion fuels. Using the model predictions, advantageous fuel design parameters are recommended to prevent breakaway swelling.

A numerical model of heavy gas dispersion

International Nuclear Information System (INIS)

Bidokhtti, A.A.

1993-01-01

A simple mathematical model describing the motion of a dense gas released continuously into and environment is presented. The model correctly predicts the laboratory experiments which were carried out by Britter and Snyder (1987). It is an entrainment model better known as box model. In this model, the effects of temperature change and phase change are not considered and it is for a steady-state case. Further work is required for including these effects which are often associated with the mechanisms involved in accidental or natural release of heavy gases in the environment. The results of such a model will be extended to the practical situations which are and will be common to the nuclear industry at the Atomic Energy Organization of Iran. The applicability of such studies to these situations will be discussed

Turbulence modification due to bubbles and particles in dispersed two-phase upflows in a vertical pipe

International Nuclear Information System (INIS)

Hosokawa, Shigeo; Tomiyama, Akio

1999-01-01

One of the key issues in two-phase turbulence modeling is the turbulence modification due to the momentum exchange between the dispersed and continuous phases. As for the gas-liquid two-phase flows in vertical pipes, Serizawa and Kataoka carried out detailed measurement of turbulence intensity and detected the turbulence modification. Gore and Crowe pointed out that the modification is well correlated with the ratio of a particle diameter to a turbulence length scale (d/l t ). However the modification may depend on not only the length scales but also the eddy viscosities of shear-induced and particle-induced turbulence. Hosokawa et al. proposed the ratio φ of the eddy viscosity induced by a dispersed phase to the shear-induced eddy viscosity and confirmed that measured turbulence modification was well correlated with φ for a gas-solid two-phase flow. In this study, we examine whether or not φ is also applicable to gas-liquid and solid-liquid two-phase dispersed upflows in vertical pipes. Using the eddy viscosity ratio instead of d/l t , we could obtain much better correlation. The critical point at which no modification occurred was close to φ = 1, irrespective of a type of a two-phase dispersed flow. Consequently, we could confirm that the eddy viscosity ratio is a more appropriate parameter for correlating the turbulent modification than the conventional critical parameter d/l t . (author)

Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Rieken, Joel [Iowa State Univ., Ames, IA (United States)

2011-12-13

Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O₂) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand the kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from

Glyoxal and methylglyoxal as urinary markers of diabetes. Determination using a dispersive liquid-liquid microextraction procedure combined with gas chromatography-mass spectrometry.

Science.gov (United States)

Pastor-Belda, M; Fernández-García, A J; Campillo, N; Pérez-Cárceles, M D; Motas, M; Hernández-Córdoba, M; Viñas, P

2017-08-04

Glyoxal (GO) and methylglyoxal (MGO) are α-oxoaldehydes that can be used as urinary diabetes markers. In this study, their levels were measured using a sample preparation procedure based on salting-out assisted liquid-liquid extraction (SALLE) and dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-mass spectrometry (GC-MS). The effect of the derivatization reaction with 2,3-diaminonaphthalene, the addition of acetonitrile and sodium chloride to urine, and the DLLME step using the acetonitrile extract as dispersant solvent and carbon tetrachloride as extractant solvent were carefully optimized. Quantification was performed by the internal standard method, using 5-bromo-2-chloroanisole. The intraday and interday precisions were lower than 6%. Limits of detection were 0.12 and 0.06ngmL -1 , and enrichment factors 140 and 130 for GO and MGO, respectively. The concentrations of these α-oxoaldehydes in urine were between 0.9 and 35.8ngg -1 levels (creatinine adjusted). A statistical comparison of the analyte contents of urine samples from non-diabetic and diabetic patients pointed to significant differences (P=0.046, 24 subjects investigated), particularly regarding MGO, which was higher in diabetic patients. The novelty of this study compared with previous procedures lies in the treatment of the urine sample by SALLE based on the addition of acetonitrile and sodium chloride to the urine. The DLLME procedure is performed with a sedimented drop of the extractant solvent, without a surfactant reagent, and using acetonitrile as dispersant solvent. Separation of the analytes was performed using GC-MS detection, being the analytes unequivocal identified. The proposed procedure is the first microextraction method applied to the analysis of urine samples from diabetic and non-diabetic patients that allows a clear differentiation between both groups using a simple analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Description of dedusting in wet flue gas scrubbers with purposeful utilization of the secondary dispersion; Detailliertere Simulation der Staubabscheidung in Nasswaeschern durch Beruecksichtigung der Sekundaerdispersion

Energy Technology Data Exchange (ETDEWEB)

Feldkamp, M.; Lessmann, B.; Neumann, J.; Fahlenkamp, H. [Dortmund Univ. (Germany). Lehrstuhl Umwelttechnik

2003-07-01

Modern wet gas scrubbers are used in the power plant technology for the flue gas desulphurisation of coal-fired plants. For this the washing liquid is sprayed by numerous nozzles. The specific arrangement of the nozzles in several levels makes it possible for the spray to penetrate mutually. The penetration and overlapping of the spray in the wet scrubber causes the effect of secondary dispersion. This effect can be used effectively to improve the efficiency of the atomisation and to improve the absorption of the pollution gases in a flue gas desulphurisation scrubber. Analyses show that the cleaning efficiency of a wet scrubber depends on the distribution and the size of the drops. (orig.) [German] Moderne Gaswaescher werden in der Kraftwerkstechnik fuer die Rauchgasentschwefelung kohlebefeuerter Anlagen eingesetzt. Hierzu wird Waschfluessigkeit mit Hilfe zahlreicher Duesen zerstaeubt. Eine gezielte Anordnung der Duesen in mehreren Spruehebenen ermoeglicht es den Sprays der Duesen, sich gegenseitig zu durchdringen. Der Effekt der Sekundaerdisperson, der beim Ueberschneiden und Durchdringen der Sprays waehrend der Zerstaeubung im Rauchgaswaescher auftritt, laesst sich wirksam zur Verbesserung des Wirkungsgrades einer Rauchgasentschwefelungsanlage nutzen. Durchgefuehrte Untersuchungen zeigen, dass die Reinigungsleistung eines nassen REA-Waeschers von der Verteilung und der Groesse der Tropfen abhaengt. (orig.)

Analysis of hydrodynamic regimes of operation of a gas pipeline from the Samotlor field to the Nizhnevartovsk gas refinery

Energy Technology Data Exchange (ETDEWEB)

Al' tshular, S A; Bragunov, N I; Ivanov, V N; Izmaylov, I Ye; Koroleva, L N

1979-01-01

Results are presented from studying the hydraulic losses of a gas-transport system. Oil gas in the first stage of separation of the Samotlor field according to the plan is transported on two gas pipelines to the Nizhnevartovsk and Belozersk gas refinery. On the route of the first gas pipeline in order to remove the released condensate, 12 gas-separator and condensate-settling tanks are installed. The second gas pipeline in the beginning, middle and end has asemblies for additional separation (separation (separator, drop-separator, condensate-collector). The studied material is presented in the form of the dependence of actual calculatedcoefficients of hydraulic resistance on the rate of gas supply in the range 80,000-230,000 m/sup 3//h (Re-(0.82.0) X 10/sup -6/. It has been established that with Re=1.6 X 10/sup -6/ the calculated and actual coeffic-ients of resistance become the same, while with smaller values of Re, the actual values exceed the calculated by 20-40%. In the opinion of the authors this difference is due to the effect of the liquid phase with low velocities of gas and the formation of stable foam. As a result of transillumination it was also established that the regime of flow on the ascending part is dispersion-ring and dispersion-semiring, and on the descending part stratified. Analysis of the transport of the gas-condensate stream with ring regime of flow permitted the authors to hypothesize transporting of gas without removal of the condensate. A certain increase in the coefficients of resistance for the case where the condensate is not removed from the gas pipeline is noted with experimental realization of the proposed variant. It is explained by the low velocities of gas in the beginning of the gas pipeline. It is stressed that the actual and calculated pressure differentials are distinguished less than the calculated and actual coefficients of resistance and that this indicates the practical preservation of the throughput of the gas pipeline.

Experimental station for gas phase fluorescence spectroscopy

International Nuclear Information System (INIS)

Stankiewicz, M.; Garcia, E. Melero; Ruiz, J. Alvarez; Erman, P.; Hatherly, P.A.; Kivimaeki, A.; Rachlew, E.; Rius i Riu, J.

2004-01-01

The details of an experimental setup for gas phase atomic and molecular fluorescence measurements using synchrotron radiation are described in this article. The most significant part of the apparatus is an optical arrangement, which allows for simultaneous measurements of dispersed as well as total fluorescence intensity using an effusive gas jet and an inbuilt gas cell assembled in a convenient plug and measure configuration. The first measurements concerning fluorescence of the N 2 molecule around the N 1s edge obtained with this setup are presented

Compression of turbulent magnetized gas in giant molecular clouds

Science.gov (United States)

Birnboim, Yuval; Federrath, Christoph; Krumholz, Mark

2018-01-01

Interstellar gas clouds are often both highly magnetized and supersonically turbulent, with velocity dispersions set by a competition between driving and dissipation. This balance has been studied extensively in the context of gases with constant mean density. However, many astrophysical systems are contracting under the influence of external pressure or gravity, and the balance between driving and dissipation in a contracting, magnetized medium has yet to be studied. In this paper, we present three-dimensional magnetohydrodynamic simulations of compression in a turbulent, magnetized medium that resembles the physical conditions inside molecular clouds. We find that in some circumstances the combination of compression and magnetic fields leads to a rate of turbulent dissipation far less than that observed in non-magnetized gas, or in non-compressing magnetized gas. As a result, a compressing, magnetized gas reaches an equilibrium velocity dispersion much greater than would be expected for either the hydrodynamic or the non-compressing case. We use the simulation results to construct an analytic model that gives an effective equation of state for a coarse-grained parcel of the gas, in the form of an ideal equation of state with a polytropic index that depends on the dissipation and energy transfer rates between the magnetic and turbulent components. We argue that the reduced dissipation rate and larger equilibrium velocity dispersion has important implications for the driving and maintenance of turbulence in molecular clouds and for the rates of chemical and radiative processes that are sensitive to shocks and dissipation.

Randomly dispersed particle fuel model in the PSG Monte Carlo neutron transport code

International Nuclear Information System (INIS)

Leppaenen, J.

2007-01-01

High-temperature gas-cooled reactor fuels are composed of thousands of microscopic fuel particles, randomly dispersed in a graphite matrix. The modelling of such geometry is complicated, especially using continuous-energy Monte Carlo codes, which are unable to apply any deterministic corrections in the calculation. This paper presents the geometry routine developed for modelling randomly dispersed particle fuels using the PSG Monte Carlo reactor physics code. The model is based on the delta-tracking method, and it takes into account the spatial self-shielding effects and the random dispersion of the fuel particles. The calculation routine is validated by comparing the results to reference MCNP4C calculations using uranium and plutonium based fuels. (authors)

Method to produce combustible gas with low tar content out of biomass. Foerfarande foer att ur biomassa framstaella en tjaerfattig braennbar gas

Energy Technology Data Exchange (ETDEWEB)

Lindman, N

1988-01-11

The gas is led in a controlled flow to a vertical reactor shaft with a circulating fluidized bed containing dispersed calcined limestone. The biomass is pyrolyzed by means of the reactor heat in order to produce tarry gas and charcoal. While the gas flows upward in the reactor shaft the tar is gasified in a heterogeneous catalytic reaction with limestone. Charcoal and limestone are separated from the gas at the top of the reactor shaft and brought back to the fluidized bed for combustion. (L.F.).

Modelling of non-catalytic reactors in a gas-solid trickle flow reactor: Dry, regenerative flue gas desulphurization using a silica-supported copper oxide sorbent

NARCIS (Netherlands)

Kiel, J.H.A.; Kiel, J.H.A.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

1992-01-01

A one-dimensional, two-phase dispersed plug flow model has been developed to describe the steady-state performance of a relatively new type of reactor, the gas-solid trickle flow reactor (GSTFR). In this reactor, an upward-flowing gas phase is contacted with as downward-flowing dilute solids phase

A constraint on the velocity dispersion of the missing mass in the solar neighborhood

International Nuclear Information System (INIS)

Nakamura, Takashi

1978-01-01

The stability of an N-component stellar disk with finite thickness is examined with the gas dynamical approximation. The dispersion relation for marginal stability is obtained. This dispersion relation for N = 2 is applied to the missing mass problem in the solar neighborhood, where two components represent the observed mass component and the missing mass component in the solar neighborhood. From the requirement that the Galactic disk should be locally stable, it is found that the velocity dispersion of the missing mass component should be greater than about 25km/sec. The stability of an infinitesimally thin disk is also investigated and compared with the disk of finite thickness. (auth.)

Investigation of the propagation characteristics in turbulent dispersed two-phase flow

International Nuclear Information System (INIS)

Sami, S.M.

1980-01-01

The propagation characteristics of turbulent dispersed two-phase flows have been studied experimentally using the Pitot tube associated with a conical hot-film anemometer. It is found that the mixture velocity increases with decreasing volumetric mixing ratio of the air and water. The void fraction distribution shows homogeneity across the test section in the special case of fully developed boundary layer two-phase flow. An expression is obtained which relates the local mixture velocity to the local void fraction, gas and liquid densities, and volumetric gas-liquid ratio

Detailed analysis of uranium silicide dispersion fuel swelling

International Nuclear Information System (INIS)

Hofmann, G.L.; Ryu, Woo-Seog

1991-01-01

Swelling of U 3 Si and U 3 Si 2 is analyzed. The growth of fission gas bubbles appears to be affected by fission rate, fuel loading, and micro structural change taking place in the fuel compounds during irradiation. Several mechanisms are explored to explain the observations. The present work is aimed at a better understanding of the basic swelling phenomenon in order to accurately model irradiation behavior of uranium silicide dispersion fuel. (orig.)

Accelerating Gas Adsorption on 3D Percolating Carbon Nanotubes.

Science.gov (United States)

Li, Hui; Wen, Chenyu; Zhang, Youwei; Wu, Dongping; Zhang, Shi-Li; Qiu, Zhi-Jun

2016-02-18

In the field of electronic gas sensing, low-dimensional semiconductors such as single-walled carbon nanotubes (SWCNTs) can offer high detection sensitivity owing to their unprecedentedly large surface-to-volume ratio. The sensitivity and responsivity can further improve by increasing their areal density. Here, an accelerated gas adsorption is demonstrated by exploiting volumetric effects via dispersion of SWCNTs into a percolating three-dimensional (3D) network in a semiconducting polymer. The resultant semiconducting composite film is evaluated as a sensing membrane in field effect transistor (FET) sensors. In order to attain reproducible characteristics of the FET sensors, a pulsed-gate-bias measurement technique is adopted to eliminate current hysteresis and drift of sensing baseline. The rate of gas adsorption follows the Langmuir-type isotherm as a function of gas concentration and scales with film thickness. This rate is up to 5 times higher in the composite than only with an SWCNT network in the transistor channel, which in turn results in a 7-fold shorter time constant of adsorption with the composite. The description of gas adsorption developed in the present work is generic for all semiconductors and the demonstrated composite with 3D percolating SWCNTs dispersed in functional polymer represents a promising new type of material for advanced gas sensors.

Aspects of the dispersion of denser-than-air vapours relevant to gas cloud explosions

International Nuclear Information System (INIS)

Wheatley, C.J.; Webber, D.M.

1985-01-01

The essential aim of the study presented here is to improve upon the understanding and prediction of the atmospheric dispersion of denser-than-air vapours, and thereby reduce the uncertainties in predicting hazards which might arise from the accidental release of a dense, flammable vapour cloud. In the first phase of the study, models for dispersion in the atmosphere of denser-than-air vapours are reviewed. It is found that a significant source of uncertainty in predictions of all models is the calculation of dilution caused by turbulence. This is due to spreading and stratification caused by the excess density of the cloud and to the interaction of the cloud motion with the ambient flow field. These effects lead to a complex field of turbulence. An additional, significant source of uncertainty is found to be present in '3D' models due to the use of coarse computational grids. A number of experimental tests are proposed which permit fundamental discrimination between the models with the object of reducing uncertainties. In the second phase of the study, a new 'box' model is proposed (A 'box' model is one in which only gross properties of the flow are predicted). All sources of turbulence are included in a way consistent with laboratory studies of entrainment in stratified flows. The prescribed concentration distribution models the initial 'mixed layer'/'gravity spreading' phase and the final 'passive' phase of dispersion with a smooth transition between the two. In the third phase of the study, implications of dispersion of denser-than-air flammable vapour clouds in open terrain for flame speeds following ignition by a weak source are assessed. It is concluded that flame speeds sufficient to cause significant overpressures cannot occur in unobstructed terrain. (author)

The effect of the environment conditions on the prediction of flammable cloud dispersion

OpenAIRE

Schleder, Adriana; Martins, Marcelo; Pastor Ferrer, Elsa; Planas Cuchi, Eulàlia

2014-01-01

In order to quantify the damage caused by undesired events involving leakages of flammable materials, specific models are used to analyze the spills or jets of gas and liquid, gas dispersion, explosions and fires. The main step of this analysis is to estimate the concentration, in space and time, of the vapor cloud of hazardous substances released into the atmosphere; the purpose is to determine the area where a fire or explosion might occur and the quantity of flam...

Attenuation and velocity dispersion in the exploration seismic frequency band

Science.gov (United States)

Sun, Langqiu

In an anelastic medium, seismic waves are distorted by attenuation and velocity dispersion, which depend on petrophysical properties of reservoir rocks. The effective attenuation and velocity dispersion is a combination of intrinsic attenuation and apparent attenuation due to scattering, transmission response, and data acquisition system. Velocity dispersion is usually neglected in seismic data processing partly because of insufficient observations in the exploration seismic frequency band. This thesis investigates the methods of measuring velocity dispersion in the exploration seismic frequency band and interprets the velocity dispersion data in terms of petrophysical properties. Broadband, uncorrelated vibrator data are suitable for measuring velocity dispersion in the exploration seismic frequency band, and a broad bandwidth optimizes the observability of velocity dispersion. Four methods of measuring velocity dispersion in uncorrelated vibrator VSP data are investigated, which are the sliding window crosscorrelation (SWCC) method, the instantaneous phase method, the spectral decomposition method, and the cross spectrum method. Among them, the SWCC method is a new method and has satisfactory robustness, accuracy, and efficiency. Using the SWCC method, velocity dispersion is measured in the uncorrelated vibrator VSP data from three areas with different geological settings, i.e., Mallik gas hydrate zone, McArthur River uranium mines, and Outokumpu crystalline rocks. The observed velocity dispersion is fitted to a straight line with respect to log frequency for a constant (frequency-independent) Q value. This provides an alternative method for calculating Q. A constant Q value does not directly link to petrophysical properties. A modeling study is implemented for the Mallik and McArthur River data to interpret the velocity dispersion observations in terms of petrophysical properties. The detailed multi-parameter petrophysical reservoir models are built according to

A method for simulating the release of natural gas from the rupture of high-pressure pipelines in any terrain.

Science.gov (United States)

Deng, Yajun; Hu, Hongbing; Yu, Bo; Sun, Dongliang; Hou, Lei; Liang, Yongtu

2018-01-15

The rupture of a high-pressure natural gas pipeline can pose a serious threat to human life and environment. In this research, a method has been proposed to simulate the release of natural gas from the rupture of high-pressure pipelines in any terrain. The process of gas releases from the rupture of a high-pressure pipeline is divided into three stages, namely the discharge, jet, and dispersion stages. Firstly, a discharge model is established to calculate the release rate of the orifice. Secondly, an improved jet model is proposed to obtain the parameters of the pseudo source. Thirdly, a fast-modeling method applicable to any terrain is introduced. Finally, based upon these three steps, a dispersion model, which can take any terrain into account, is established. Then, the dispersion scenarios of released gas in four different terrains are studied. Moreover, the effects of pipeline pressure, pipeline diameter, wind speed and concentration of hydrogen sulfide on the dispersion scenario in real terrain are systematically analyzed. The results provide significant guidance for risk assessment and contingency planning of a ruptured natural gas pipeline. Copyright © 2017. Published by Elsevier B.V.

Computational fluid dynamics simulation of wind-driven inter-unit dispersion around multi-storey buildings: Upstream building effect

DEFF Research Database (Denmark)

Ai, Zhengtao; Mak, C.M.; Dai, Y.W.

2017-01-01

of such changed airflow patterns on inter-unit dispersion characteristics around a multi-storey building due to wind effect. Computational fluid dynamics (CFD) method in the framework of Reynolds-averaged Navier-stokes modelling was employed to predict the coupled outdoor and indoor airflow field, and the tracer...... gas technique was used to simulate the dispersion of infectious agents between units. Based on the predicted concentration field, a mass conservation based parameter, namely re-entry ratio, was used to evaluate quantitatively the inter-unit dispersion possibilities and thus assess risks along...

Interplay between absorption, dispersion and refraction in high-order harmonic generation

International Nuclear Information System (INIS)

Dachraoui, H; Helmstedt, A; Bartz, P; Michelswirth, M; Mueller, N; Pfeiffer, W; Heinzmann, U; Auguste, T; Salieres, P

2009-01-01

We report a detailed experimental and theoretical study on high-order harmonic generation of a femtosecond Ti-sapphire laser focused at an intensity of around 10 15 W cm -2 onto a high-pressure (50-210 mbar) neon gas cell of variable length (1-3 mm). Using thorough three-dimensional simulations, we discuss the interplay between the different factors influencing the harmonic-generation efficiency, i.e. phase matching determined by the electronic and atomic dispersions, re-absorption of the harmonics by the medium and refraction of the generating laser beam. Generically, we find that, in our generation conditions, the emission yield of harmonics from the plateau region of the spectrum is absorption limited, whereas the emission from harmonics in the cut-off is strongly reduced due to both electron dispersion and ionization-induced refraction of the laser beam. A good agreement between the numerical results and the experimental data is obtained for the harmonic yield dependence on the various generation parameters (gas pressure, medium length and laser intensity).

New particle formation in the fresh flue-gas plume from a coal-fired power plant: effect of flue-gas cleaning

Science.gov (United States)

Mylläri, Fanni; Asmi, Eija; Anttila, Tatu; Saukko, Erkka; Vakkari, Ville; Pirjola, Liisa; Hillamo, Risto; Laurila, Tuomas; Häyrinen, Anna; Rautiainen, Jani; Lihavainen, Heikki; O'Connor, Ewan; Niemelä, Ville; Keskinen, Jorma; Dal Maso, Miikka; Rönkkö, Topi

2016-06-01

Atmospheric emissions, including particle number and size distribution, from a 726 MWth coal-fired power plant were studied experimentally from a power plant stack and flue-gas plume dispersing in the atmosphere. Experiments were conducted under two different flue-gas cleaning conditions. The results were utilized in a plume dispersion and dilution model taking into account particle formation precursor (H2SO4 resulted from the oxidation of emitted SO2) and assessment related to nucleation rates. The experiments showed that the primary emissions of particles and SO2 were effectively reduced by flue-gas desulfurization and fabric filters, especially the emissions of particles smaller than 200 nm in diameter. Primary pollutant concentrations reached background levels in 200-300 s. However, the atmospheric measurements indicated that new particles larger than 2.5 nm are formed in the flue-gas plume, even in the very early phases of atmospheric ageing. The effective number emission of nucleated particles were several orders of magnitude higher than the primary particle emission. Modelling studies indicate that regardless of continuing dilution of the flue gas, nucleation precursor (H2SO4 from SO2 oxidation) concentrations remain relatively constant. In addition, results indicate that flue-gas nucleation is more efficient than predicted by atmospheric aerosol modelling. In particular, the observation of the new particle formation with rather low flue-gas SO2 concentrations changes the current understanding of the air quality effects of coal combustion. The results can be used to evaluate optimal ways to achieve better air quality, particularly in polluted areas like India and China.

Method of storing radioactive rare gas. [gas occupies spaces in the zeolite crystal lattice

Energy Technology Data Exchange (ETDEWEB)

Nagao, H; Miharada, H; Takiguchi, Y; Kanazawa, T; Soya, M

1975-05-15

A method is provided to prevent dispersion of radioactive rare gas atoms by sealing them in a pressurised state within zeolite and thereby confining them in position within the zeolite crystal lattice. Radioactive rare gas is separated from exhaust gas and concentrated by using a low temperature adsorption means or liquefaction distillation means and necessary accessory means, and then it is temporarily stored in a gas holder. When a predetermined quantity of storage is reached, the gas is led to a sealing tank containing zeolite heated to 300 to 400/sup 0/C and held at 3,000 to 4,000 atmospheres, and under this condition radioactive rare gas is brought to occupy the spaces in the zeolite crystal lattice. After equilibrium pressure is reached by the pressure in the tank at that temperature, the gas is cooled in the pressurised state down to room temperature. Subsequently, the rare gas remaining in the tank and duct is recovered by a withdrawal pump into the gas holder. Thereafter, the zeolite with radioactive rare gas sealed in it is taken out from the tank and sealed within a long period storage container, which is then housed in a predetermined place for storage.

Determination of selected UV filters in indoor dust by matrix solid-phase dispersion and gas chromatography-tandem mass spectrometry.

Science.gov (United States)

Negreira, N; Rodríguez, I; Rubí, E; Cela, R

2009-07-31

A simple, inexpensive sample preparation procedure, based on the matrix solid-phase dispersion (MSPD) technique, for the determination of six UV filters: 2-ethylhexyl salicylate (EHS), 3,3,5-trimethylcyclohexyl salicylate (Homosalate, HMS), 3-(4-methylbenzylidene) camphor (4-MBC), isoamyl-p-methoxycinnamate (IAMC), 2-ethylhexyl-p-methoxycinnamate (EHMC) and octocrylene (OCR), in dust from indoor environments is presented and the influence of several operational parameters on the extraction performance discussed. Under the final working conditions, sieved samples (0.5 g) were mixed with the same amount of anhydrous sodium sulphate and dispersed with 2 g of octadecyl bonded silica (C18) in a mortar with a pestle. This blend was transferred to a polypropylene solid-phase extraction cartridge containing 2 g of activated silica, as the clean-up co-sorbent. The cartridge was first rinsed with 5 mL of n-hexane and the analytes were then recovered with 4 mL of acetonitrile. This extract was adjusted to 1 mL, filtered and the compounds were determined by gas chromatography combined with tandem mass spectrometry (GC-MS/MS). Recoveries for samples spiked at two different concentrations ranged between 77% and 99%, and the limits of quantification (LOQs) of the method between 10 and 40 ng g(-1). Analysis of settled dust from different indoor areas, including private flats, public buildings and vehicle cabins, showed that EHMC and OCR were ubiquitous in this matrix, with maximum concentrations of 15 and 41 microg g(-1), respectively. Both UV filters were also quantified in dust reference material SRM 2585 for first time. EHS, 4-MBC and IAMC were detected in some of the analyzed samples, although at lower concentrations than EHMC and OCR.

Particle dispersing system and method for testing semiconductor manufacturing equipment

Science.gov (United States)

Chandrachood, Madhavi; Ghanayem, Steve G.; Cantwell, Nancy; Rader, Daniel J.; Geller, Anthony S.

1998-01-01

The system and method prepare a gas stream comprising particles at a known concentration using a particle disperser for moving particles from a reservoir of particles into a stream of flowing carrier gas. The electrostatic charges on the particles entrained in the carrier gas are then neutralized or otherwise altered, and the resulting particle-laden gas stream is then diluted to provide an acceptable particle concentration. The diluted gas stream is then split into a calibration stream and the desired output stream. The particles in the calibration stream are detected to provide an indication of the actual size distribution and concentration of particles in the output stream that is supplied to a process chamber being analyzed. Particles flowing out of the process chamber within a vacuum pumping system are detected, and the output particle size distribution and concentration are compared with the particle size distribution and concentration of the calibration stream in order to determine the particle transport characteristics of a process chamber, or to determine the number of particles lodged in the process chamber as a function of manufacturing process parameters such as pressure, flowrate, temperature, process chamber geometry, particle size, particle charge, and gas composition.

Hairy root culture in a liquid-dispersed bioreactor: characterization of spatial heterogeneity.

Science.gov (United States)

Williams, G R; Doran, P M

2000-01-01

A liquid-dispersed reactor equipped with a vertical mesh cylinder for inoculum support was developed for culture of Atropa belladonna hairy roots. The working volume of the culture vessel was 4.4 L with an aspect ratio of 1.7. Medium was dispersed as a spray onto the top of the root bed, and the roots grew radially outward from the central mesh cylinder to the vessel wall. Significant benefits in terms of liquid drainage and reduced interstitial liquid holdup were obtained using a vertical rather than horizontal support structure for the biomass and by operating the reactor with cocurrent air and liquid flow. With root growth, a pattern of spatial heterogeneity developed in the vessel. Higher local biomass densities, lower volumes of interstitial liquid, lower sugar concentrations, and higher root atropine contents were found in the upper sections of the root bed compared with the lower sections, suggesting a greater level of metabolic activity toward the top of the reactor. Although gas-liquid oxygen transfer to the spray droplets was very rapid, there was evidence of significant oxygen limitations in the reactor. Substantial volumes of non-free-draining interstitial liquid accumulated in the root bed. Roots near the bottom of the vessel trapped up to 3-4 times their own weight in liquid, thus eliminating the advantages of improved contact with the gas phase offered by liquid-dispersed culture systems. Local nutrient and product concentrations in the non-free-draining liquid were significantly different from those in the bulk medium, indicating poor liquid mixing within the root bed. Oxygen enrichment of the gas phase improved neither growth nor atropine production, highlighting the greater importance of liquid-solid compared with gas-liquid oxygen transfer resistance. The absence of mechanical or pneumatic agitation and the tendency of the root bed to accumulate liquid and impede drainage were identified as the major limitations to reactor performance. Improved

Study of abrasive wear process of lining of grinding chamber of vortex-acoustic disperser

Science.gov (United States)

Perelygin, D. N.

2018-03-01

The theoretical and experimental studies of the process of gas-abrasive wear of the lining of a vortex-acoustic disperser made it possible to establish the conditions and patterns of their occurrence and also to develop proposals for its reduction.

The effect of a tall tower on flow and dispersion through a model urban neighborhood: part 2. Pollutant dispersion.

Science.gov (United States)

Brixey, Laurie A; Heist, David K; Richmond-Bryant, Jennifer; Bowker, George E; Perry, Steven G; Wiener, Russell W

2009-12-01

This article is the second in a two-paper series presenting results from wind tunnel and computational fluid dynamics (CFD) simulations of flow and dispersion in an idealized model urban neighborhood. Pollutant dispersion results are presented and discussed for a model neighborhood that was characterized by regular city blocks of three-story row houses with a single 12-story tower located at the downwind edge of one of these blocks. The tower had three significant effects on pollutant dispersion in the surrounding street canyons: drawing the plume laterally towards the tower, greatly enhancing the vertical dispersion of the plume in the wake of the tower, and significantly decreasing the residence time of pollutants in the wake of the tower. In the wind tunnel, tracer gas released in the avenue lee of the tower, but several blocks away laterally, was pulled towards the tower and lifted in the wake of the tower. The same lateral movement of the pollutant was seen in the next avenue, which was approximately 2.5 tower heights downwind of the tower. The tower also served to ventilate the street canyon directly in its wake more rapidly than the surrounding areas. This was evidenced by CFD simulations of concentration decay where the residence time of pollutants lee of the 12-story tower was found to be less than half the residence time behind a neighboring three-story building. This same phenomenon of rapid vertical dispersion lee of a tower among an array of smaller buildings was also demonstrated in a separate set of wind tunnel experiments using an array of cubical blocks. A similar decrease in the residence time was observed when the height of one block was increased.

A laboratory dispersant effectiveness test which reflects dispersant efficiency in the field

International Nuclear Information System (INIS)

Lunel, T.; Wood, P.

1996-01-01

Oil dispersion efficiencies of surfactants, from laboratory dispersion tests and field data were compared and calibrated. Data from an oil spill, where dispersants were used as a major part of the response, was analysed. The data was accumulated through the monitoring of the dispersant operation of the Sea Empress spill incident, in which Forties Blend oil was spilled at sea. This detailed data set was used to calibrate existing laboratory dispersant tests, and to devise a new International Dispersant Effectiveness Test. The objective was to create a comprehensive guide to decision making on whether and when to start a dispersant spraying operation. The dispersion efficiencies obtained from the laboratory dispersant tests were compared with field data. Flume tests produced the highest percentage of dispersed oil for all the dispersal tests. However, it was emphasised that the total percentage of oil dispersed should not be the only measure of dispersant effectiveness, since it does not distinguish between the contribution of natural and chemically enhanced dispersion. 9 refs., 1 tab., 9 figs

Wetting in a colloidal liquid-gas system

NARCIS (Netherlands)

Wijting, W.K.; Besseling, N.A.M.; Cohen Stuart, M.A.

2003-01-01

We present first observations of wetting phenomena in depletion interaction driven, phase separated colloidal dispersions (coated silica-cyclohexane-polydimethylsiloxane). The contact angle of the colloidal liquid-gas interface at a solid substrate (coated glass) was determined for a series of

Dispersion and Stabilization of Photocatalytic TiO2 Nanoparticles in Aqueous Suspension for Coatings Applications

Directory of Open Access Journals (Sweden)

Siti Hajar Othman

2012-01-01

Full Text Available To produce titanium dioxide (TiO2 nanoparticle coatings, it is desirable that the nanoparticles are dispersed into a liquid solution and remain stable for a certain period of time. Controlling the dispersion and aggregation of the nanoparticles is crucial to exploit the advantages of the nanometer-sized TiO2 particles. In this work, TiO2 nanoparticles were dispersed and stabilized in aqueous suspensions using two common dispersants which were polyacrylic acid (PAA and ammonium polymethacrylate (Darvan C. The effect of parameters such as ultrasonication amplitude and type and amount of dispersants on the dispersibility and stability of the TiO2 aqueous suspensions were examined. Rupture followed by erosion was determined to be the main break up mechanisms when ultrasonication was employed. The addition of dispersant was found to produce more dispersed and more stabilized aqueous suspension. 3 wt.% of PAA with average molecular weight (Mw of 2000 g/mol (PAA 2000 was determined to produce the best and most stable dispersion. The suspensions were then coated on quartz glass, whereby the photocatalytic activity of the coatings was studied via the degradation of formaldehyde gas under UV light. The coatings were demonstrated to be photocatalytically active.

Ultrasound-assisted leaching-dispersive solid-phase extraction followed by liquid-liquid microextraction for the determination of polybrominated diphenyl ethers in sediment samples by gas chromatography-tandem mass spectrometry.

Science.gov (United States)

Fontana, Ariel R; Lana, Nerina B; Martinez, Luis D; Altamirano, Jorgelina C

2010-06-30

Ultrasound-assisted leaching-dispersive solid-phase extraction followed by dispersive liquid-liquid microextraction (USAL-DSPE-DLLME) technique has been developed as a new analytical approach for extracting, cleaning up and preconcentrating polybrominated diphenyl ethers (PBDEs) from sediment samples prior gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. In the first place, PBDEs were leached from sediment samples by using acetone. This extract was cleaned-up by DSPE using activated silica gel as sorbent material. After clean-up, PBDEs were preconcentrated by using DLLME technique. Thus, 1 mL acetone extract (disperser solvent) and 60 microL carbon tetrachloride (extraction solvent) were added to 5 mL ultrapure water and a DLLME technique was applied. Several variables that govern the proposed technique were studied and optimized. Under optimum conditions, the method detection limits (MDLs) of PBDEs calculated as three times the signal-to-noise ratio (S/N) were within the range 0.02-0.06 ng g(-1). The relative standard deviations (RSDs) for five replicates were or =0.9991. Validation of the methodology was carried out by standard addition method at two concentration levels (0.25 and 1 ng g(-1)) and by comparing with a reference Soxhlet technique. Recovery values were > or =80%, which showed a satisfactory robustness of the analytical methodology for determination of low PBDEs concentration in sediment samples. Copyright 2010 Elsevier B.V. All rights reserved.

DART model for irradiation-induced swelling of dispersion fuel elements including aluminum-fuel interaction

International Nuclear Information System (INIS)

Rest, J.; Hofman, G.L.

1997-01-01

The Dispersion Analysis Research Tool (DART) contains models for fission-gas-induced fuel swelling, interaction of fuel with the matrix aluminum, for the resultant reaction-product swelling, and for the calculation of the stress gradient within the fuel particle. The effects of an aluminide shell on fuel particle swelling are evaluated. Validation of the model is demonstrated by a comparison of DART calculations of fuel swelling of U 3 SiAl-Al and U 3 Si 2 -Al for various dispersion fuel element designs with the data

Murgabskaya Oblast, a promising gas region of Central Asia

Energy Technology Data Exchange (ETDEWEB)

Amanniyazov, K.N.; Abdyyev, A.A.

1981-01-01

Gas fields of the Murgabskiy region are multiple-bed. The industrial gas content is associated with the sandy-terrigenous formations of the Shatlyk productive level of the lower Goterivskiy stage. The gas formation is anticlinal, occasionally floating. A map is compiled for the dispersal of the Shatlyk level which isolates the lithological composition, thickness, zones of dispersal of sandstone, etc. A description is provided for the map plan of the Shatlyk level. Alternation of sandy-argillaceous and carbonate rocks created favorable prerequisites for the development in the deposits of the Neocomian of lithological-physical pairs of ''collectors-mantles'', the basis for trap formation in structures and zones of lithological substitution. Within the Murgabskiy region, the greatest outlook for discovering new gas fields is confined to the Shatlyk level. It is associated with the central part of the Murgabskiy Basin where major deposits have already been discovered. A group of structures in the eastern submersion of the Kopetdag trough at the junction of the Murgabskiy Basin is important. The structures at the junction of East Kopetdag and the Murgabskiy Basin may be promising. The outlook for possible gas is associated with deposits of the lower cretaceous and Sharaplinksiy level. The main task must be comprehensive in investigation of the suprasaline apt-Neocomian and Kimmeridgian-Tithonian deposits as possible multiple-bed gas and oil containing masses.

Airfoil lance apparatus for homogeneous humidification and sorbent dispersion in a gas stream

Science.gov (United States)

Myers, Robert B.; Yagiela, Anthony S.

1990-12-25

An apparatus for spraying an atomized mixture into a gas stream comprises a stream line airfoil member having a large radius leading edge and a small radius trailing edge. A nozzle assembly pierces the trailing edge of the airfoil member and is concentrically surrounded by a nacelle which directs shielding gas from the interior of the airfoil member around the nozzle assembly. Flowable medium to be atomized and atomizing gas for atomizing the medium are supplied in concentric conduits to the nozzle. A plurality of nozzles each surrounded by a nacelle are spaced along the trailing edge of the airfoil member.

Energy-Saving Vibration Impulse Coal Degradation at Finely Dispersed Coal-Water Slurry Preparation

Directory of Open Access Journals (Sweden)

Moiseev V.A.

2015-01-01

Full Text Available Theoretical and experimental research results of processes of finely dispersed coal-water slurry preparation for further generation of energetic gas in direct flow and vortex gas generator plants have been presented. It has been stated that frequency parameters of parabolic vibration impulse mill influence degradation degree. Pressure influence on coal parameters in grinding cavity has been proven. Experimental researches have proven efficiency of vibration impulse mill with unbalanced mass vibrator generator development. Conditions of development on intergranular walls of coal cracks have been defined.

Dispersion in a thermal plasma including arbitrary degeneracy and quantum recoil.

Science.gov (United States)

Melrose, D B; Mushtaq, A

2010-11-01

The longitudinal response function for a thermal electron gas is calculated including two quantum effects exactly, degeneracy, and the quantum recoil. The Fermi-Dirac distribution is expanded in powers of a parameter that is small in the nondegenerate limit and the response function is evaluated in terms of the conventional plasma dispersion function to arbitrary order in this parameter. The infinite sum is performed in terms of polylogarithms in the long-wavelength and quasistatic limits, giving results that apply for arbitrary degeneracy. The results are applied to the dispersion relations for Langmuir waves and to screening, reproducing known results in the nondegenerate and completely degenerate limits, and generalizing them to arbitrary degeneracy.

Gas-partitioning tracer test to qualify trapped gas during recharge

Science.gov (United States)

Heilweil, Victor M.; Kip, Solomon D.; Perkins, Kim S.; Ellett, Kevin M.

2004-01-01

Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.

Gas-partitioning tracer test to quantify trapped gas during recharge

Science.gov (United States)

Heilweil, V.M.; Solomon, D.K.; Perkins, K.S.; Ellett, K.M.

2004-01-01

Dissolved helium and bromide tracers were used to evaluate trapped gas during an infiltration pond experiment. Dissolved helium preferentially partitioned into trapped gas bubbles, or other pore air, because of its low solubility in water. This produced observed helium retardation factors of as much as 12 relative to bromide. Numerical simulations of helium breakthrough with both equilibrium and kinetically limited advection/dispersion/retardation did not match observed helium concentrations. However, better fits were obtained by including a decay term representing the diffusive loss of helium through interconnected, gas-filled pores. Calculations indicate that 7% to more than 26% of the porosity beneath the pond was filled with gas. Measurements of laboratory hydraulic properties indicate that a 10% decrease in saturation would reduce the hydraulic conductivity by at least one order of magnitude in the well-sorted sandstone, but less in the overlying soils. This is consistent with in situ measurements during the experiment, which show steeper hydraulic gradients in sandstone than in soil. Intrinsic permeability of the soil doubled during the first six months of the experiment, likely caused by a combination of dissolution and thermal contraction of trapped gas. Managers of artificial recharge basins may consider minimizing the amount of trapped gas by using wet, rather than dry, tilling to optimize infiltration rates, particularly in well-sorted porous media in which reintroduced trapped gas may cause substantial reductions in permeability. Trapped gas may also inhibit the amount of focused infiltration that occurs naturally during ephemeral flood events along washes and playas.

Development of dispersion interferometer for magnetic confinement plasmas and high-pressure plasmas

Science.gov (United States)

Akiyama, T.; Yasuhara, R.; Kawahata, K.; Nakayama, K.; Okajima, S.; Urabe, K.; Terashima, K.; Shirai, N.

2015-09-01

A CO2 laser dispersion interferometer (DI) has been developed for both magnetically fusion plasmas and high pressure industrial plasmas. The DI measures the phase shift caused by dispersion in a medium. Therefore, it is insensitive to the mechanical vibrations and changes in the neutral gas density, which degrade the resolution of the electron density measurement. We installed the DI on the Large Helical Device (LHD) and demonstrated a high density resolution of 2× 1017 m-3 without any vibration-free bench. The measured electron density with the DI shows good agreement with results of the existing far infrared laser (a wavelength of 119 μ m) interferometer. The DI system is also applied to the electron density measurement of high-pressure small-scale plasmas. The significant suppression of the phase shift caused by the neutral gas is proven. The achieved density resolution was 1.5× 1019 m-3 with a response time of 100 μ s. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics

On the impact of trees on dispersion processes of traffic emissions in street canyons

NARCIS (Netherlands)

Gromke, C.B.; Ruck, B.

2009-01-01

Wind-tunnel studies of dispersion processes of traffic exhaust in urban street canyons with tree planting were performed and tracer gas concentrations using electron capture detection (ECD) and flow fields using laser Doppler velocimetry (LDV) were measured. It was found that tree planting reduces

Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas

International Nuclear Information System (INIS)

Perali, A.; Palestini, F.; Pieri, P.; Strinati, G. C.; Stewart, J. T.; Gaebler, J. P.; Drake, T. E.; Jin, D. S.

2011-01-01

Wave-vector resolved radio frequency spectroscopy data for an ultracold trapped Fermi gas are reported for several couplings at T c , and extensively analyzed in terms of a pairing-fluctuation theory. We map the evolution of a strongly interacting Fermi gas from the pseudogap phase into a fully gapped molecular Bose gas as a function of the interaction strength, which is marked by a rapid disappearance of a remnant Fermi surface in the single-particle dispersion. We also show that our theory of a pseudogap phase is consistent with a recent experimental observation as well as with quantum Monte Carlo data of thermodynamic quantities of a unitary Fermi gas above T c .

Synthesis of mono-dispersed nanofluids using solution plasma

Energy Technology Data Exchange (ETDEWEB)

Heo, Yong Kang, E-mail: yk@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Bratescu, Maria Antoaneta, E-mail: maria@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Knowledge Hub Aichi, Yakusa-cho, Nagakute-ku, Toyota (Japan); Ueno, Tomonaga, E-mail: tomo@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); CREST, Japan Science and Technology Agency, Goban-cho, Chiyoda-ku, Tokyo (Japan); Saito, Nagahiro, E-mail: hiro@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Knowledge Hub Aichi, Yakusa-cho, Nagakute-ku, Toyota (Japan); Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); CREST, Japan Science and Technology Agency, Goban-cho, Chiyoda-ku, Tokyo (Japan)

2014-07-14

Small-sized and well-dispersed gold nanoparticles (NPs) for nanofluidics have been synthesized by electrical discharge in liquid environment using termed solution plasma processing (SPP). Electrons and the hydrogen radicals are reducing the gold ions to the neutral form in plasma gas phase and liquid phase, respectively. The gold NPs have the smallest diameter of 4.9 nm when the solution temperature was kept at 20 °C. Nucleation and growth theory describe the evolution of the NP diameter right after the reduction reaction in function of the system temperature, NP surface energy, dispersion energy barrier, and nucleation rate. Negative charges on the NPs surface during and after SPP generate repulsive forces among the NPs avoiding their agglomeration in solution. Increasing the average energy in the SPP determines a decrease of the zeta potential and an increase of the NPs diameter. An important enhancement of the thermal conductivity of 9.4% was measured for the synthesized nanofluids containing NPs with the smallest size.

Dispersion bias, dispersion effect, and the aerosol-cloud conundrum

International Nuclear Information System (INIS)

Liu Yangang; Daum, Peter H; Guo Huan; Peng Yiran

2008-01-01

This work examines the influences of relative dispersion (the ratio of the standard deviation to the mean radius of the cloud droplet size distribution) on cloud albedo and cloud radiative forcing, derives an analytical formulation that accounts explicitly for the contribution from droplet concentration and relative dispersion, and presents a new approach to parameterize relative dispersion in climate models. It is shown that inadequate representation of relative dispersion in climate models leads to an overestimation of cloud albedo, resulting in a negative bias of global mean shortwave cloud radiative forcing that can be comparable to the warming caused by doubling CO 2 in magnitude, and that this dispersion bias is likely near its maximum for ambient clouds. Relative dispersion is empirically expressed as a function of the quotient between cloud liquid water content and droplet concentration (i.e., water per droplet), yielding an analytical formulation for the first aerosol indirect effect. Further analysis of the new expression reveals that the dispersion effect not only offsets the cooling from the Twomey effect, but is also proportional to the Twomey effect in magnitude. These results suggest that unrealistic representation of relative dispersion in cloud parameterization in general, and evaluation of aerosol indirect effects in particular, is at least in part responsible for several outstanding puzzles of the aerosol-cloud conundrum: for example, overestimation of cloud radiative cooling by climate models compared to satellite observations; large uncertainty and discrepancy in estimates of the aerosol indirect effect; and the lack of interhemispheric difference in cloud albedo.

Polymeric dispersants for control of steam generator fouling

International Nuclear Information System (INIS)

Balakrishnan, P.V.; Klimas, S.J.; Lepine, L.; Turner, C.W.

1999-05-01

Fouling of steam generators by corrosion products from the feedtrain leads to loss of heat-transfer efficiency, disturbances in thermalhydraulics, and potential corrosion problems resulting from the development of sites for localized accumulation of aggressive chemicals. This report summarizes studies of the use of polymeric dispersants for the control of fouling, which were conducted at the Chalk River Laboratories. High-temperature settling studies on magnetite suspensions were performed to screen available generic dispersants, and the dispersants were ranked in terms of their dispersion efficiency; polyacrylic acid (PAA) and the phosphonate, HEDP, were ranked as the most efficient. Polyacrylic acid was considered more suitable than HEDP for nuclear steam generators, and more emphasis was given to the former in these studies. The dispersants had no effect on the particle deposition rates under single-phase forced-convective flow, but did reduce the deposition rates under flow-boiling conditions. The extent to which the deposition rates were reduced increased in proportion to the dispersant concentration. Preliminary corrosion tests indicated that pitting or general corrosion of steam generator tube materials in the presence of PAA was negligible. Corrosion of carbon steel, although higher in a magnetite-packed crevice under heat flux than in bulk water, was lower in the presence of PAA than in its absence. Some impurities (e.g., sulphate, sodium) were observed in commercially available PAA products at small, though significant concentrations, making these products unacceptable for use in nuclear plants. However, the PAA could be purified by ion exchange. Preliminary experiments, to assess the thermal stability of PAA at steam generator operating temperature, showed the polymer to break down in deaerated solutions and under argon cover to give hydrogen and carbon dioxide as the two major products in the gas phase and variable concentrations of acetate and formate

Statistical Physics of Colloidal Dispersions.

Science.gov (United States)

Canessa, E.

changes of the depletion attraction with free polymer concentration. Chapter IV deals with the contributions of pairwise additive and volume dependent forces to the free energy of charge stabilized colloidal dispersions. To a first approximation the extra volume dependent contributions due to the chemical equilibrium and counterion-macroion coupling are treated in a one-component plasma approach. Added salt is treated as an ionized gas within the Debye-Huckel theory of electrolytes. In order to set this approach on a quantitative basis the existence of an equilibrium lattice with a small shear modulus is examined. Structural phase transitions in these systems are also analysed theoretically as a function of added electrolyte.

Dispersion, sorption and photodegradation of petroleum hydrocarbons in dispersant-seawater-sediment systems.

Science.gov (United States)

Zhao, Xiao; Liu, Wen; Fu, Jie; Cai, Zhengqing; O'Reilly, S E; Zhao, Dongye

2016-08-15

This work examined effects of model oil dispersants on dispersion, sorption and photodegradation of petroleum hydrocarbons in simulated marine systems. Three dispersants (Corexit 9500A, Corexit 9527A and SPC 1000) were used to prepare dispersed water accommodated oil (DWAO). While higher doses of dispersants dispersed more n-alkanes and PAHs, Corexit 9500A preferentially dispersed C11-C20 n-alkanes, whereas Corexit 9527A was more favorable for smaller alkanes (C10-C16), and SPC 1000 for C12-C28 n-alkanes. Sorption of petroleum hydrocarbons on sediment was proportional to TPH types/fractions in the DWAOs. Addition of 18mg/L of Corexit 9500A increased sediment uptake of 2-3 ring PAHs, while higher dispersant doses reduced the uptake, due to micelle-enhanced solubilization effects. Both dispersed n-alkanes and PAHs were susceptible to photodegradation under simulated sunlight. For PAHs, both photodegradation and photo-facilitated alkylation were concurrently taking place. The information can facilitate sounder assessment of fate and distribution of dispersed oil hydrocarbons in marine systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Method for high temperature mercury capture from gas streams

Science.gov (United States)

Granite, Evan J [Wexford, PA; Pennline, Henry W [Bethel Park, PA

2006-04-25

A process to facilitate mercury extraction from high temperature flue/fuel gas via the use of metal sorbents which capture mercury at ambient and high temperatures. The spent sorbents can be regenerated after exposure to mercury. The metal sorbents can be used as pure metals (or combinations of metals) or dispersed on an inert support to increase surface area per gram of metal sorbent. Iridium and ruthenium are effective for mercury removal from flue and smelter gases. Palladium and platinum are effective for mercury removal from fuel gas (syngas). An iridium-platinum alloy is suitable for metal capture in many industrial effluent gas streams including highly corrosive gas streams.

Fission gas in thoria

Energy Technology Data Exchange (ETDEWEB)

Kuganathan, Navaratnarajah, E-mail: n.kuganathan@imperial.ac.uk [Department of Materials, Faculty of Engineering, Imperial College, London, SW7 2AZ (United Kingdom); Ghosh, Partha S. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Galvin, Conor O.T. [Department of Materials, Faculty of Engineering, Imperial College, London, SW7 2AZ (United Kingdom); Arya, Ashok K. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Dutta, Bijon K. [Homi Bhabha National Institute, Trombay, Mumbai 400 094 (India); Dey, Gautam K. [Material Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Grimes, Robin W. [Department of Materials, Faculty of Engineering, Imperial College, London, SW7 2AZ (United Kingdom)

2017-03-15

The fission gases Xe and Kr, formed during normal reactor operation, are known to degrade fuel performance, particularly at high burn-up. Using first-principles density functional theory together with a dispersion correction (DFT + D), in ThO{sub 2} we calculate the energetics of neutral and charged point defects, the di-vacancy (DV), different neutral tri-vacancies (NTV), the charged tetravacancy (CTV) defect cluster geometries and their interaction with Xe and Kr. The most favourable incorporation point defect site for Xe or Kr in defective ThO{sub 2} is the fully charged thorium vacancy. The lowest energy NTV in larger supercells of ThO{sub 2} is NTV3, however, a single Xe atom is most stable when accommodated within a NTV1. The di-vacancy (DV) is a significantly less favoured incorporation site than the NTV1 but the CTV offers about the same incorporation energy. Incorporation of a second gas atom in a NTV is a high energy process and more unfavourable than accommodation within an existing Th vacancy. The bi-NTV (BNTV) cluster geometry studied will accommodate one or two gas atoms with low incorporation energies but the addition of a third gas atom incurs a high energy penalty. The tri-NTV cluster (TNTV) forms a larger space which accommodates three gas atoms but again there is a penalty to accommodate a fourth gas atom. By considering the energy to form the defect sites, solution energies were generated showing that in ThO{sub 2−x} the most favourable solution equilibrium site is the NTV1 while in ThO{sub 2} it is the DV. - Highlights: • We have considered Xe and Kr in point defects and defect clusters (neutral and charged) using Density Functional Theory (DFT) with a dispersion correction. • The most favourable charge state for a point defect (vacancy or interstitial) is that with full ionic charge and we have found that in all cases gas atoms occupy the fully charged vacancy sites. • The number of fission gas atoms accommodated in ThO{sub 2} is

Study on the irradiation swelling of U3Si2-Al dispersion fuel

International Nuclear Information System (INIS)

Xing Zhonghu; Ying Shihao

2001-01-01

The dominant modeling mechanisms on irradiation swelling of U 3 Si 2 -Al dispersion fuel are introduced. The core of dispersion fuel is looked to as micro-fuel elements of continuous matrix. The formation processes of gas bubbles in the fuel phase are described through the behavior mechanisms of fission gases. The swelling in the fuel phase causes the interaction between fuel particles and metal matrix, and the metal matrix can restrain the irradiation swelling of fuel particles. The developed code can predict irradiation-swelling values according to the parameters of fuel elements and irradiation conditions, and the predicted values are in agreement with the measured results

Resistive sensing of gaseous nitrogen dioxide using a dispersion of single-walled carbon nanotubes in an ionic liquid

Energy Technology Data Exchange (ETDEWEB)

Mishra, Prabhash [Solidstate Electronics Research Laboratory (SERL), Faculty of Engineering and Technology, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025 (India); Department of Nanoengineering, Samara State Aerospace University, 443086 Samara (Russian Federation); Pavelyev, V.S. [Department of Nanoengineering, Samara State Aerospace University, 443086 Samara (Russian Federation); Patel, Rajan [Center for Interdisciplinary Research in Basic Sciences (CIRBSc), Jamia Millia Islamia, Jamia Nagar, New Delhi 110025 (India); Islam, S.S., E-mail: sislam@jmi.ac.in [Solidstate Electronics Research Laboratory (SERL), Faculty of Engineering and Technology, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025 (India)

2016-06-15

Graphical abstract: Ionic liquid ([C6-mim]PF6) used as dispersant agent for SWCNTs: An investigations were carried out to find the structural quality and surface modification for sensor application. - Highlights: • An effective technique based on Ionic liquids (IL) and their use as a dispersant. • Electron microscopy and spectroscopy for structure characterization. • Covalent linkage of ILs with SWNTs and dispersion of SWCNTs. • The IL-wrapped sensing film, capable for detecting trace levels of gas. - Abstract: Single-walled carbon nanotubes (SWCNTs) were dispersed in an imidazolium-based ionic liquid (IL) and investigated in terms of structural quality, surface functionalization and inter-CNT force. Analysis by field emission electron microscopy and transmission electron microscopy shows the IL layer to coat the SWNTs, and FTIR and Raman spectroscopy confirm strong binding of the ILs to the SWNTs. Two kinds of resistive sensors were fabricated, one by drop casting of IL-wrapped SWCNTs, the other by conventional dispersion of SWCNTs. Good response and recovery to NO{sub 2} is achieved with the IL-wrapped SWCNTs material upon UV-light exposure, which is needed because decrease the desorption energy barrier to increase the gas molecule desorption. NO{sub 2} can be detected in the 1–20 ppm concentration range. The sensor is not interfered by humidity due to the hydrophobic tail of PF6 (ionic liquid) that makes our sensor highly resistant to moisture.

Optimized Feature Extraction for Temperature-Modulated Gas Sensors

Directory of Open Access Journals (Sweden)

Alexander Vergara

2009-01-01

Full Text Available One of the most serious limitations to the practical utilization of solid-state gas sensors is the drift of their signal. Even if drift is rooted in the chemical and physical processes occurring in the sensor, improved signal processing is generally considered as a methodology to increase sensors stability. Several studies evidenced the augmented stability of time variable signals elicited by the modulation of either the gas concentration or the operating temperature. Furthermore, when time-variable signals are used, the extraction of features can be accomplished in shorter time with respect to the time necessary to calculate the usual features defined in steady-state conditions. In this paper, we discuss the stability properties of distinct dynamic features using an array of metal oxide semiconductors gas sensors whose working temperature is modulated with optimized multisinusoidal signals. Experiments were aimed at measuring the dispersion of sensors features in repeated sequences of a limited number of experimental conditions. Results evidenced that the features extracted during the temperature modulation reduce the multidimensional data dispersion among repeated measurements. In particular, the Energy Signal Vector provided an almost constant classification rate along the time with respect to the temperature modulation.

Electron density measurement of non-equilibrium atmospheric pressure plasma using dispersion interferometer

Science.gov (United States)

Yoshimura, Shinji; Kasahara, Hiroshi; Akiyama, Tsuyoshi

2017-10-01

Medical applications of non-equilibrium atmospheric plasmas have recently been attracting a great deal of attention, where many types of plasma sources have been developed to meet the purposes. For example, plasma-activated medium (PAM), which is now being studied for cancer treatment, has been produced by irradiating non-equilibrium atmospheric pressure plasma with ultrahigh electron density to a culture medium. Meanwhile, in order to measure electron density in magnetic confinement plasmas, a CO2 laser dispersion interferometer has been developed and installed on the Large Helical Device (LHD) at the National Institute for Fusion Science, Japan. The dispersion interferometer has advantages that the measurement is insensitive to mechanical vibrations and changes in neutral gas density. Taking advantage of these properties, we applied the dispersion interferometer to electron density diagnostics of atmospheric pressure plasmas produced by the NU-Global HUMAP-WSAP-50 device, which is used for producing PAM. This study was supported by the Grant of Joint Research by the National Institutes of Natural Sciences (NINS).

Effects of chemical dispersants on oil physical properties and dispersion. Volume 1

International Nuclear Information System (INIS)

Khelifa, A.; Fingas, M.; Hollebone, B.P.; Brown, C.E.; Pjontek, D.

2007-01-01

Laboratory and field testing have shown that the dispersion of oil spilled in water is influenced by chemical dispersants via the modification of the interfacial properties of the oil, such as oil-brine interfacial tension (IFT). This study focused on new laboratory experiments that measured the effects on the physical properties and dispersion of oil, with particular reference to the effects of chemical dispersants on IFT and oil viscosity and the subsequent effects on oil droplet formation. Experiments were conducted at 15 degrees C using Arabian Medium, Alaska North Slope and South Louisiana crude and Corexit 9500 and Corexit 9527 chemical dispersants. The dispersants were denser than the 3 oils. The effect of IFT reduction on oil dispersion was measured and showed substantial reduction in the size and enhancement of the concentration of oil droplets in the water column. It was shown that the brine-oil IFT associated with the 3 crudes reduced to less than 3.6 mN/m with the application of the chemical dispersants, even at a low dispersant-to-oil ratio (DOR) value of 1:200. The use of chemical dispersants increased the viscosity of the dispersant-oil mixture up to 40 per cent over the neat crude oil. It was shown that for each mixing condition, an optimum value of DOR exists that provides for maximal dispersant effectiveness. The IFT reaches maximum reduction at optimum DOR. It was suggested that oil spill modelling can be improved with further study of IFT reduction with DOR and variations of critical micelle concentration with the type and solubility of chemical dispersant, oil type and oil to water ratio. 13 refs., 3 tabs., 7 figs

Experimental and theoretical investigations on the release and propagation of heavy gas; Experimentelle und theoretische Untersuchungen zur Schwergasfreisetzung und -ausbreitung

Energy Technology Data Exchange (ETDEWEB)

Rauchegger, Christian

2013-06-01

The hazardous potential of accidental heavy gas releases, especially those involving flammable and toxic gases, is widely known. In order to predict the area in which these gases are in hazardous concentrations, an estimation of the dispersion of these gases must be carried out. While the hazardous area for flammable heavy gases is determined by the lower explosion limit (ca. > 1 vol.%), the release of toxic heavy gases can result in a much larger hazardous area, as toxic gases, even in very low concentrations (ca. < 3000 ppm), have the potential to be highly damaging. The VDI guideline 3783, which is considered as state-of-the-art in Germany, can be used to estimate the dispersion of heavy gases. However, VDI 3783 gives no method for the prediction of the height and width of a heavy gas cloud, which are both required for quantitative risk analysis as well as for a possible coupling of a Lagrangian particle model with the VDI 3783 heavy gas dispersion model. Therefore, further calculation methods were used to describe these dimensions and were evaluated against, experimental studies of the length, width and height of the heavy and neutral gas field. The influence of the source height on the heavy gas dispersion was also investigated. It was found that elevating the source leads to a reduction of the length of the heavy gas area. Once the source reaches a critical height, a heavy gas area at ground level no longer exists. Therefore, for release heights above the critical height, heavy gas dispersion effects can be neglected and the calculation of the heavy gas area according to VDI 3783 part 2 is therefore no longer necessary. The release of heavy gases can occur from a process plant as well as from a standard gas bottle. For the release of heavy gases from standard gas bottles, a mathematical model has been developed to predict the time-dependent mass flow. This model takes into account the time-dependent temperature distribution of the bottle wall, and contains a

Gas sensing application of nanocrystalline zinc oxide thin films ...

Indian Academy of Sciences (India)

Experimental data revealed the sensors to be more selective to NO2 gas with satisfactory response and recovery time. .... energy-dispersive X-ray spectroscopy (EDS, JEOL Model ... nm line of argon ion laser was used for excitation. 3.

Measurement of liquid holdup and axial dispersion in trickle bed reactors using radiotracer technique

International Nuclear Information System (INIS)

Pant, H.J.; Saroha, A.K.; Nikam, K.D.P.

2000-01-01

The holdup and axial dispersion of aqueous phase has been measured in trickle bed reactors as a function of liquid and gas flow rates using radioisotope tracer technique. Experiments were carried out in the glass column of inner diameter of 15.2x10 -2 m column for air-water system using three different types of packings i.e. non-porous glass beads, porous catalyst of tablet and extrudate shape. The range of liquid and gas flow rates used were 8.3x10 -5 - 3.3x1- -4 m 3 /s and 0 - 6.67x10 -4 m 3 /s, respectively. Residence time distributions of liquid phase and gas phase were measured and mean residence times were determined. The values of liquid holdup were calculated from the measured mean residence times. It was observed that the liquid holdup increases with increase in liquid flow rates and was independent of increase in gas flow rates used in the study. Two-parameter axial dispersion model was used to simulate measured residence time distribution data and values of mean residence time and Peclet number were obtained. It was observed that the values of Peclet number increases with increase in liquid flow rate for glass beads and tablets and remains almost constant for extrudates. The values of mean residence time obtained from model simulation were found to be in good agreement with the values measured experimentally. (author)

The effect of the computational grid size on the prediction of a flammable cloud dispersion

OpenAIRE

Schleder, Adriana; Martins, Marcelon; Pastor Ferrer, Elsa; Planas Cuchi, Eulàlia

2014-01-01

The consequence analysis is used to define the extent and nature of effects caused by undesired events being of great help when quantifying the damage caused by such events. For the case of leaking of flammable and/or toxic materials, effects are analyzed for explosions, fires and toxicity. Specific models are used to analyze the spills or jets of gas or liquids, gas dispersions, explosions and fires. The central step in the analysis of consequences in such cases is to de...

CFD Study of Gas Dispersion and Jet Fires in Complex Geometries

DEFF Research Database (Denmark)

Osenbroch, Jørgen

(Hall 1997, McQuaid & Roebuck 1985) and (Sklavonuos & Rigas 2004). The Composite Radiosity Gap radiation model has been implemented in EXSIM. The predicted heat fluxes obtained from horizontally released natural gas jet fires have been compared to experimental findings reported by Johnson et al. (1994...

Optimal sensor locations for the backward Lagrangian stochastic technique in measuring lagoon gas emission

Science.gov (United States)

This study evaluated the impact of gas concentration and wind sensor locations on the accuracy of the backward Lagrangian stochastic inverse-dispersion technique (bLS) for measuring gas emission rates from a typical lagoon environment. Path-integrated concentrations (PICs) and 3-dimensional (3D) wi...

TOXRISK, Toxic Gas Release Accident Analysis

International Nuclear Information System (INIS)

Bennett, D.E.; Chanin, D.I.; Shiver, A.W.

1993-01-01

1 - Description of program or function: TOXRISK is an interactive program developed to aid in the evaluation of nuclear power plant control room habitability in the event of a nearby toxic material release. The program uses a model which is consistent with the approach described in the NRC Regulatory Guide 1.78. Release of the gas is treated as an initial puff followed by a continuous plume. The relative proportions of these as well as the plume release rate are supplied by the user. Transport of the gas is modeled as a Gaussian distribution and occurs through the action of a constant velocity, constant direction wind. Great flexibility is afforded the user in specifying the release description, meteorological conditions, relative geometry of the accident and plant, and the plant ventilation system characteristics. Two types of simulation can be performed: multiple case (parametric) studies and probabilistic analyses. Upon execution, TOXRISK presents a menu, and the user chooses between the Data Base Manager, the Multiple Case program, and the Probabilistic Study Program. The Data Base Manager provides a convenient means of storing, retrieving, and modifying blocks of data required by the analysis programs. The Multiple Case program calculates resultant gas concentrations inside the control room and presents a summary of information that describes the event for each set of conditions given. Optimally, a time history profile of inside and outside concentrations can also be produced. The Probabilistic Study program provides a means for estimating the annual probability of operator incapacitation due to toxic gas accidents on surrounding transportation routes and storage sites. 2 - Method of solution: Dispersion or diffusion of the gas during transport is described by modified Pasquill-Gifford dispersion coefficients

Removal of Disperse Blue 56 and Disperse Red 135 dyes from aqueous dispersions by modified montmorillonite nanoclay

Directory of Open Access Journals (Sweden)

Ahmadishoar Javad

2017-01-01

Full Text Available In this study modified montmorillonite was used as an adsorbent for the removal of two selected disperse dyes i.e., Disperse Blue 56 (DB and Disperse Red 135 (DR from dye dispersions. The adsorption equilibrium data of dyes adsorption were investigated by using Nernst, Freundlich and Langmuir isotherm models. The adsorption kinetics was analyzed by using different models including pseudo-first-order, pseudo-second-order, Elovich and Intraparticle diffusion model. The Freundlich isotherm was found to be the most appropriate model for describing the sorption of the dyes on modified nanoclay. The best fit to the experimental results was obtained by using the pseudo-second-order kinetic equation, which satisfactorily described the process of dye adsorption. Although different kinetic models may control the rate of the adsorption process, the results indicated that the main rate limiting step was the intraparticle diffusion. The results showed that the proposed modified montmorillonite could be used as an effective adsorbent for the removal of disperse dyes even from highly concentrated dispersions.

A new approximation of the dispersion relations occurring in the sound-attenuation problem of turbofan aircraft engines

Directory of Open Access Journals (Sweden)

Robert SZABO

2011-12-01

Full Text Available The dispersion relations, appearing in the analysis of the stability of a gas flow in a straight acoustically-lined duct with respect to perturbations produced by a time harmonic source, beside the wave number and complex frequency contain the solution of a boundary value problem of the Pridmore-Brown equation depending on the wave number and frequency. For this reason, in practice the dispersion relations are rarely simple enough for carried out the zeros. The determination of zeros of these dispersion relations is crucial for the prediction of the perturbation attenuation or amplification. In this paper an approximation of the dispersion relations is given. Our approach preserves the general character of the mean flow, the general Pridmore-Brown equation and it’s only in the shear flow that we replace the exact solution of the boundary value problem with its Taylor polynomial approximate. In this way new approximate dispersion relations are obtained which zero’s can be found by computer.

Dispersion in thermal plasma including arbitrary degeneracy and quantum recoil

International Nuclear Information System (INIS)

Mushtaq, A.; Melrose, D.B.

2012-01-01

The longitudinal response function for a thermal electron gas was calculated including two quantum effects exactly, degeneracy and the quantum recoil. The Fermi-Dirac distribution was expanded in powers of a parameter that is small in the non-degenerate limit and the response function was evaluated in terms of the conventional plasma dispersion function to arbitrary order in this parameter. The infinite sum was performed in terms of poly logarithms in the long-wavelength and quasi-static limits, giving results that apply for arbitrary degeneracy. The results were applied to the dispersion relations for Langmuir waves and to screening, reproducing known results in the non-degenerate and completely degenerate limits], and generalizing them to arbitrary degeneracy. The occupation number for the completely degenerate limit is shown. The importance of the results regarding to semiconductor plasmas were highlighted. (orig./A.B.)

Dynamic simulation of dispersed gas-liquid two-phase flow using a discrete bubble model.

NARCIS (Netherlands)

Delnoij, E.; Lammers, F.A.; Kuipers, J.A.M.; van Swaaij, Willibrordus Petrus Maria

1997-01-01

In this paper a detailed hydrodynamic model for gas-liquid two-phase flow will be presented. The model is based on a mixed Eulerian-Lagrangian approach and describes the time-dependent two-dimensional motion of small, spherical gas bubbles in a bubble column operating in the homogeneous regime. The

Analysis of the physical atomic forces between noble gas atoms, alkali ions and halogen ions

Science.gov (United States)

Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

1986-01-01

The physical forces between atoms and molecules are important in a number of processes of practical importance, including line broadening in radiative processes, gas and crystal properties, adhesion, and thin films. The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base for the dispersion forces is developed from the literature based on evaluations with the harmonic oscillator dispersion model for higher order coefficients. The Zener model of the repulsive core is used in the context of the recent asymptotic wave functions of Handler and Smith; and an effective ionization potential within the Handler and Smith wave functions is defined to analyze the two body potential data of Waldman and Gordon, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

Computational Fluid Dynamics Simulations of Gas-Phase Radial Dispersion in Fixed Beds with Wall Effects

Directory of Open Access Journals (Sweden)

Anthony G. Dixon

2017-10-01

Full Text Available The effective medium approach to radial fixed bed dispersion models, in which radial dispersion of mass is superimposed on axial plug flow, is based on a constant effective dispersion coefficient, DT. For packed beds of a small tube-to-particle diameter ratio (N, the experimentally-observed decrease in this parameter near the tube wall is accounted for by a lumped resistance located at the tube wall, the wall mass transfer coefficient km. This work presents validated computational fluid dynamics (CFD simulations to obtain detailed radial velocity and concentration profiles for eight different computer-generated packed tubes of spheres in the range 5.04 ≤ N ≤ 9.3 and over a range of flow rates 87 ≤ Re ≤ 870 where Re is based on superficial velocity and the particle diameter dp. Initial runs with pure air gave axial velocity profiles vz(r averaged over the length of the packing. Then, simulations with the tube wall coated with methane yielded radial concentration profiles. A model with only DT could not describe the radial concentration profiles. The two-parameter model with DT and km agreed better with the bed-center concentration profiles, but not with the sharp decreases in concentration close to the tube wall. A three-parameter model based on classical two-layer mixing length theory, with a wall-function for the decrease in transverse radial convective transport in the near-wall region, showed greatly improved ability to reproduce the near-wall concentration profiles.

The application of a microstrip gas counter to energy-dispersive x-ray fluorescence analysis

International Nuclear Information System (INIS)

Veloso, J.F.C.A.; Santos, J.M.F. dos; Conde, C.A.N.

1996-01-01

Performance characteristics of a microstrip gas counter operated as a x-ray fluorescence spectrometer are reported. Gas amplification as a function of microstrip anode-cathode voltage was measured, and the breakdown threshold voltage was determined in pure xenon. The detector temporal stability and the effect of gas purity were assessed. Energy resolution and linearity, detection efficiency, and uniformity of spatial response in the 2- to 60-keV x-ray energy range were determined from the pulse-height distributions of the fluorescence x-ray spectra induced in a variety of single- and multi-element sample materials. Energy resolution similar to conventional proportional counters was achieved at 6 keV

Functionalized carbon nanotubes mixed matrix membranes of polymers of intrinsic microporosity for gas separation.

Science.gov (United States)

Khan, Muntazim Munir; Filiz, Volkan; Bengtson, Gisela; Shishatskiy, Sergey; Rahman, Mushfequr; Abetz, Volker

2012-09-06

The present work reports on the gas transport behavior of mixed matrix membranes (MMM) which were prepared from multi-walled carbon nanotubes (MWCNTs) and dispersed within polymers of intrinsic microporosity (PIM-1) matrix. The MWCNTs were chemically functionalized with poly(ethylene glycol) (PEG) for a better dispersion in the polymer matrix. MMM-incorporating functionalized MWCNTs (f-MWCNTs) were fabricated by dip-coating method using microporous polyacrylonitrile membrane as a support and were characterized for gas separation performance. Gas permeation measurements show that MMM incorporated with pristine or functionalized MWCNTs exhibited improved gas separation performance compared to pure PIM-1. The f-MWCNTs MMM show better performance in terms of permeance and selectivity in comparison to pristine MWCNTs. The gas permeances of the derived MMM are increased to approximately 50% without sacrificing the selectivity at 2 wt.% of f-MWCNTs' loading. The PEG groups on the MWCNTs have strong interaction with CO2 which increases the solubility of polar gas and limit the solubility of nonpolar gas, which is advantageous for CO2/N2 selectivity. The addition of f-MWCNTs inside the polymer matrix also improved the long-term gas transport stability of MMM in comparison with PIM-1. The high permeance, selectivity, and long term stability of the fabricated MMM suggest that the reported approach can be utilized in practical gas separation technology.

Development of a new microextraction method based on elevated temperature dispersive liquid-liquid microextraction for determination of triazole pesticides residues in honey by gas chromatography-nitrogen phosphorus detection.

Science.gov (United States)

Farajzadeh, Mir Ali; Mogaddam, Mohammad Reza Afshar; Ghorbanpour, Houshang

2014-06-20

In the present study, a rapid, highly efficient, and reliable sample preparation method named "elevated temperature dispersive liquid-liquid microextraction" followed by gas chromatography-nitrogen-phosphorus detection was developed for the extraction, preconcentration, and determination of five triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, and difenoconazole) in honey samples. In this method the temperature of high-volume aqueous phase was adjusted at an elevated temperature and then a disperser solvent containing an extraction solvent was rapidly injected into the aqueous phase. After cooling to room temperature, the phase separation was accelerated by centrifugation. Various parameters affecting the extraction efficiency such as type and volume of the extraction and disperser solvents, temperature, salt addition, and pH were evaluated. Under the optimum extraction conditions, the method resulted in low limits of detection and quantification within the range 0.05-0.21ngg(-1) in honey (15-70ngL(-1) in solution) and 0.15-1.1ngg(-1) in honey (45-210ngL(-1) in solution), respectively. Enrichment factors and extraction recoveries were in the ranges of 1943-1994 and 97-100%, respectively. The method precision was evaluated at 1.5ngg(-1) of each analyte, and the relative standard deviations were found to be less than 4% for intra-day (n=6) and less than 6% for inter-days. The method was successfully applied to the analysis of honey samples and difenoconazole was determined at ngg(-1) levels. Copyright © 2014 Elsevier B.V. All rights reserved.

Response of a relativistic quantum magnetized electron gas

International Nuclear Information System (INIS)

Melrose, Donald B; Weise, Jeanette I

2009-01-01

The response 4-tensor is derived for a spin-independent, relativistic magnetized quantum electron gas. The sum over spins is carried out both directly and using a procedure due to Ritus. The 4-tensor components are written in terms of a sum over the two solutions of the resonance condition for the particle 4-momentum. It is shown that the dispersive properties may be described in terms of a single plasma dispersion function, for arbitrary occupation numbers for electrons and positrons in each Landau level. The plasma dispersion function is evaluated explicitly in the completely degenerate and nondegenerate thermal limits. The perpendicular wave number appears in the arguments of J-functions, which are proportional to generalized Laguerre polynomials, but not in the plasma dispersion function. The result generalizes a known form for the response tensor for parallel propagation (in the completely degenerate case), when the J-functions are either zero or unity, to arbitrary angles of propagation.

Nanocomposites from Stable Dispersions of Carbon Nanotubes in Polymeric Matrices Using Dispersion Interaction

Science.gov (United States)

Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Kang, Jin Ho (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor)

2016-01-01

Stable dispersions of carbon nanotubes (CNTs) in polymeric matrices include CNTs dispersed in a host polymer or copolymer whose monomers have delocalized electron orbitals, so that a dispersion interaction results between the host polymer or copolymer and the CNTs dispersed therein. Nanocomposite products, which are presented in bulk, or when fabricated as a film, fiber, foam, coating, adhesive, paste, or molding, are prepared by standard means from the present stable dispersions of CNTs in polymeric matrices, employing dispersion interactions, as presented hereinabove.

Evaluation of twin-head electrospray nanoparticle disperser for nanotoxicity study

Science.gov (United States)

Liu, Qiaoling; Budiman, Thomas; Chen, Da-Ren

2014-08-01

With the rapid development of nanotechnology, nanoparticles with various sizes and compositions have been synthesized and proposed for industrial applications. At the same time, the health effects and environmental impacts of nanoparticles become an emerging concern to be addressed. Both in vitro and in vivo studies are of importance to better understand the toxicity of nanoparticles. It is thus essential to have a nanoparticle disperser capable of dispersing individual nanoparticles for these studies. A twin-head electrospray (THES) nanoparticle disperser for animal inhalation exposure studies has recently become commercially available from TSE Systems Inc. Different from the cone-jet electrospray method used in the majority of literature, this particular disperser operates at the multi-jet mode. In this study, we reported our finding on the performance evaluation of the THES disperser with respect to its mass throughput and quality of size distribution of aerosol produced. Three different nanomaterials (TiO2, ZnO, and NiO) were used in this study. It is found that the maximal mass throughput of the studied disperser was achieved by keeping the distance between two opposite spray capillary tips at 3.0 cm, operating the primary carrier-to-capillary sheath flow rates at the ratio of 4:3, and feeding spray suspensions at a flow rate of 20 µl/min. Under the above settings and operations, the highest mass concentration for nano-ZnO was measured at 14.56 mg/m3. Nanoparticle streams with higher concentrations can be further produced by lowering the total carrier gas flow rate and spraying suspensions of higher nanomaterial concentrations. Our study also found that the particle mass throughput of the studied disperser had a good linear relationship with the mass concentration of spray suspension. In addition, the spatial uniformity of nano aerosol distribution in a TSE head-nose-only exposure chamber was investigated. An acceptable nano aerosol uniformity result was

IN-SYNC. II. VIRIAL STARS FROM SUBVIRIAL CORES—THE VELOCITY DISPERSION OF EMBEDDED PRE-MAIN-SEQUENCE STARS IN NGC 1333

International Nuclear Information System (INIS)

Foster, Jonathan B.; Cottaar, Michiel; Meyer, Michael R.; Covey, Kevin R.; Arce, Héctor G.; Nidever, David L.; Stassun, Keivan G.; Tan, Jonathan C.; Da Rio, Nicola; Chojnowski, S. Drew; Majewski, Steven R.; Skrutskie, Michael; Wilson, John C.; Flaherty, Kevin M.; Rebull, Luisa; Frinchaboy, Peter M.; Zasowski, Gail

2015-01-01

The initial velocity dispersion of newborn stars is a major unconstrained aspect of star formation theory. Using near-infrared spectra obtained with the APOGEE spectrograph, we show that the velocity dispersion of young (1-2 Myr) stars in NGC 1333 is 0.92 ± 0.12 km s –1 after correcting for measurement uncertainties and the effect of binaries. This velocity dispersion is consistent with the virial velocity of the region and the diffuse gas velocity dispersion, but significantly larger than the velocity dispersion of the dense, star-forming cores, which have a subvirial velocity dispersion of 0.5 km s –1 . Since the NGC 1333 cluster is dynamically young and deeply embedded, this measurement provides a strong constraint on the initial velocity dispersion of newly formed stars. We propose that the difference in velocity dispersion between stars and dense cores may be due to the influence of a 70 μG magnetic field acting on the dense cores or be the signature of a cluster with initial substructure undergoing global collapse

Mixer Assembly for a Gas Turbine Engine

Science.gov (United States)

Dai, Zhongtao (Inventor); Cohen, Jeffrey M. (Inventor); Fotache, Catalin G. (Inventor); Smith, Lance L. (Inventor); Hautman, Donald J. (Inventor)

2018-01-01

A mixer assembly for a gas turbine engine is provided, including a main mixer with fuel injection holes located between at least one radial swirler and at least one axial swirler, wherein the fuel injected into the main mixer is atomized and dispersed by the air flowing through the radial swirler and the axial swirler.

Wetting in a Colloidal Liquid-Gas System

Science.gov (United States)

Wijting, W. K.; Besseling, N. A.; Stuart, M. A.

2003-05-01

We present first observations of wetting phenomena in depletion interaction driven, phase separated colloidal dispersions (coated silica cyclohexane-polydimethylsiloxane). The contact angle of the colloidal liquid-gas interface at a solid substrate (coated glass) was determined for a series of compositions. Upon approach to the critical point, a transition occurs from partial to complete wetting.

Wetting in a colloidal liquid-gas system

OpenAIRE

Wijting, W.K.; Besseling, N.A.M.; Cohen Stuart, M.A.

2003-01-01

We present first observations of wetting phenomena in depletion interaction driven, phase separated colloidal dispersions (coated silica-cyclohexane-polydimethylsiloxane). The contact angle of the colloidal liquid-gas interface at a solid substrate (coated glass) was determined for a series of compositions. Upon approach to the critical point, a transition occurs from partial to complete wetting.

Noncommutative field gas driven inflation

Energy Technology Data Exchange (ETDEWEB)

Barosi, Luciano; Brito, Francisco A [Departamento de Fisica, Universidade Federal de Campina Grande, Caixa Postal 10071, 58109-970 Campina Grande, Paraiba (Brazil); Queiroz, Amilcar R, E-mail: lbarosi@ufcg.edu.br, E-mail: fabrito@df.ufcg.edu.br, E-mail: amilcarq@gmail.com [Centro Internacional de Fisica da Materia Condensada, Universidade de Brasilia, Caixa Postal 04667, Brasilia, DF (Brazil)

2008-04-15

We investigate early time inflationary scenarios in a Universe filled with a dilute noncommutative bosonic gas at high temperature. A noncommutative bosonic gas is a gas composed of a bosonic scalar field with noncommutative field space on a commutative spacetime. Such noncommutative field theories were recently introduced as a generalization of quantum mechanics on a noncommutative spacetime. Key features of these theories are Lorentz invariance violation and CPT violation. In the present study we use a noncommutative bosonic field theory that, besides the noncommutative parameter {theta}, shows up a further parameter {sigma}. This parameter {sigma} controls the range of the noncommutativity and acts as a regulator for the theory. Both parameters play a key role in the modified dispersion relations of the noncommutative bosonic field, leading to possible striking consequences for phenomenology. In this work we obtain an equation of state p = {omega}({sigma},{theta};{beta}){rho} for the noncommutative bosonic gas relating pressure p and energy density {rho}, in the limit of high temperature. We analyse possible behaviours for these gas parameters {sigma}, {theta} and {beta}, so that -1{<=}{omega}<-1/3, which is the region where the Universe enters an accelerated phase.

Chemoresistive gas sensor

Science.gov (United States)

Hirschfeld, T.B.

1987-06-23

A chemoresistive gas sensor is provided which has improved sensitivity. A layer of organic semiconductor is disposed between two electrodes which, in turn, are connected to a voltage source. High conductivity material is dispersed within the layer of organic semiconductor in the form of very small particles, or islands. The average interisland spacing is selected so that the predominant mode of current flow is by way of electron funneling. Adsorption of gaseous contaminant onto the layer of organic semiconductor modulates the tunneling current in a quantitative manner. 2 figs.

Determination of ten pyrethroids in various fruit juices: comparison of dispersive liquid-liquid microextraction sample preparation and QuEChERS method combined with dispersive liquid-liquid microextraction.

Science.gov (United States)

Zhang, Yaohai; Zhang, Xuelian; Jiao, Bining

2014-09-15

Dispersive liquid-liquid microextraction (DLLME) sample preparation and the quick, easy, cheap, effective, rugged and safe (QuEChERS) method combined with DLLME were developed and compared for the analysis of ten pyrethroids in various fruit juices using gas chromatography-electron capture detection (GC-ECD). QuEChERS-DLLME method has found its widespread applications to all the fruit juices including those samples with more complex matrices (orange, lemon, kiwi and mango) while DLLME was confined to the fruit juices with simpler matrices (apple, pear, grape and peach). The two methods provided acceptable recoveries and repeatability. In addition, the applicabilities of two methods were demonstrated with the real samples and further confirmed by gas chromatography-mass spectrometry (GC-MS). Copyright © 2014. Published by Elsevier Ltd.

Dispersive microextraction based on water-coated Fe₃O₄ followed by gas chromatography-mass spectrometry for determination of 3-monochloropropane-1,2-diol in edible oils.

Science.gov (United States)

Zhao, Qin; Wei, Fang; Xiao, Neng; Yu, Qiong-Wei; Yuan, Bi-Feng; Feng, Yu-Qi

2012-06-01

In the present work, we developed a novel dispersive microextraction technique by combining the advantages of liquid-phase microextraction (LPME) and magnetic solid-phase extraction (MSPE). In this method, trace amount of water directly absorbed on bare Fe₃O₄ to form water-coated Fe₃O₄ (W-Fe₃O₄) and rapid extraction can be achieved while W-Fe₃O₄ dispersed in the sample solution. The analyte adsorbed W-Fe₃O₄ can be easily collected and isolated from sample solution by application of a magnet. It was worth noting that in the proposed method water was used as extractant and Fe₃O₄ served as the supporter and retriever of water. The performance of the method was evaluated by extraction of 3-monochloropropane-1,2-diol (3-MCPD) from edible oils. The extracted 3-MCPD was then derived by a silylanization reagent (1-trimethylsilylimidazole) before gas chromatography-mass spectrometry (GC-MS) analysis. Several parameters that affected the extraction and derivatization efficiency were investigated. Our results showed that the limit of detection for 3-MCPD was 1.1 ng/g. The recoveries in spiked oil samples were in the range of 70.0-104.9% with the RSDs less than 5.6% (intra-day) and 6.4% (inter-day). Taken together, the simple, rapid and cost-effective method developed in current study, offers a potential application for the extraction and preconcentration of hydrophilic analytes from complex fatty samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Evaluation of ground level concentration of pollutant due to gas flaring by computer simulation: A case study of Niger - Delta area of Nigeria

Directory of Open Access Journals (Sweden)

A. S. ABDULKAREEM

2005-01-01

Full Text Available The disposal of associated gases through flaring has been a major problem for the Nigerian oil and gas industries and most of theses gases are flared due to the lack of commercial out lets. The resultant effects of gas flaring are the damaging effect of the environment due to acid rain formation, green house effect, global warming and ozone depletion.This writes up is aimed at evaluating ground level concentration of CO2, SO2, NO2 and total hydrocarbon (THC, which are product of gas flared in oil producing areas. Volumes of gas flared at different flow station were collected as well as geometrical parameters. The results of simulation of model developed based on the principles of gaseous dispersion by Gaussian showed a good agreement with dispersion pattern.The results showed that the dispersion pattern of pollutants at ground level depends on the volume of gas flared, wind speed, velocity of discharge and nearness to the source of flaring. The results shows that continuous gas flaring irrespective of the quantity deposited in the immediate environment will in long run lead to change in the physicochemical properties of soil.

Small angle elastic scattering of electrons by noble gas atoms

International Nuclear Information System (INIS)

Wagenaar, R.W.

1984-01-01

In this thesis, measurements are carried out to obtain small angle elastic differential cross sections in order to check the validity of Kramers-Kronig dispersion relations for electrons scattered by noble gas atoms. First, total cross sections are obtained for argon, krypton and xenon. Next, a parallel plate electrostatic energy analyser for the simultaneous measurement of doubly differential cross section for small angle electron scattering is described. Also absolute differential cross sections are reported. Finally the forward dispersion relation for electron-helium collisions is dealt with. (Auth.)

Irradiation behavior of uranium-silicide dispersion fuels

International Nuclear Information System (INIS)

Hofman, G.L.; Neimark, L.A.

1984-01-01

This paper describes and analyzes the irradiation behavior of experimental fuel plates containing U 3 Si, U 3 Si-1.5 w/o Al, and U 3 Si 2 particulate fuel dispersed and clad in aluminum. The fuel is nominally 19.9%-enriched 235 U and the fuel volume fraction in the central ''meat'' section of the plates is approximately 33%. Sets of fuel plates were removed from the Oak Ridge Research reactor at burnup levels of 35, 83, and 94% 235 U depletion and examined at the Alpha-Gamma Hot-Cell Facility at Argonne National Laboratory. The results of the examination may be summarized as follows. The dimensional stability of the U 3 Si 2 and pure U 3 Si fuel was excellent throughout the entire burnup range, with uniform plate thickness increases up to a maximum of 4 mils at the highest burnup level (94% 235 U depletion). This corresponds to a meat volume increase of 11%. The swelling was partially due to solid fission products but to a larger extent to fission gas bubbles. The fission gas bubbles in U 3 Si 2 were small (submicrometer size) and very uniformly distributed, indicating great stability. To a large extent this was also the case for U 3 Si; however, larger bubbles ( 3 Si-1.5 w/o Al fuel became unstable at the higher burnup levels. Fission gas bubbles were larger than in the other two fuels and were present throughout the fuel particles. At 94% 235 U depletion, the formation of fission gas bubbles with diameters up to 20 mils caused the plates to pillow. It is proposed that aluminum in U 3 Si destabilizes fission gas bubble formation to the point of severe breakaway swelling in the prealloyed silicide fuel. (author)

Dispersion Forces

CERN Document Server

Buhmann, Stefan Yoshi

2012-01-01

In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

Spatially Extended and High-Velocity Dispersion Molecular Component in Spiral Galaxies: Single-Dish Versus Interferometric Observations

Science.gov (United States)

Caldú-Primo, Anahi; Schruba, Andreas; Walter, Fabian; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

2015-02-01

Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%-74% for NGC 4736 and 81%-92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ˜(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(˜1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (˜3″ or ˜100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

Effect of air turbulence on gas transport in soil; comparison of approaches

Science.gov (United States)

Pourbakhtiar, Alireza; Papadikis, Konstantinos; Poulsen, Tjalfe; Bridge, Jonathan; Wilkinson, Stephen

2017-04-01

Greenhouse gases are playing the key role in global warming. Soil is a source of greenhouse gases such as methane (CH4). Radon (Rn) which is a radioactive gas can emit form subsurface into the atmosphere and leads to health concerns in urban areas. Temperature, humidity, air pressure and vegetation of soil can affect gas emissions inside soil (Oertel et al., 2016). It's shown in many cases that wind induced fluctuations is an important factor in transport of gas through soil and other porous media. An example is: landfill gas emissions (Poulsen et al., 2001). We applied an experimental equipment for measuring controlled air turbulence on gas transport in soil in relation to the depth of sample. Two approaches for measurement of effect of wind turbulence on gas transport were applied and compared. Experiments were carried out with diffusion of CO2 and air as tracer gases with average vertical wind speeds of 0 to 0.83 m s-1. In approach A, Six different sample thicknesses from 5 to 30 cm were selected and total of 4 different wind conditions with different speed and fluctuations were applied. In approach B, a sample with constant depth was used. Five oxygen sensors were places inside sample at different depths. Total of 111 experiments were carried out. Gas transport is described by advection-dispersion equation. Gas transport is quantified as a dispersion coefficient. Oxygen breakthrough curves as a function of distance to the surface of the sample exposed to wind were derived numerically with an explicit forward time, central space finite-difference based model to evaluate gas transport. We showed that wind turbulence-induced fluctuations is an important factor in gas transport that can increase gas transport with average of 45 times more than molecular diffusion under zero wind condition. Comparison of two strategies for experiments, indicated that, constant deep samples (Approach B) are more reliable for measurement of gas transport under influence of wind

Void fraction fluctuations in two-phase gas-liquid flow

International Nuclear Information System (INIS)

Ulbrich, R.

1987-01-01

Designs of the apparatus in which two-phase gas-liquid flow occurs are usually based on the mean value of parameters such as pressure drop and void fraction. The flow of two-phase mixtures generally presents a very complicated flow structure, both in terms of the unsteady formation on the interfacial area and in terms of the fluctuations of the velocity, pressure and other variables within the flow. When the gas void fraction is near 0 or 1 / bubble or dispersed flow regimes / then oscillations of void fraction are very small. The intermittent flow such as plug and slug/ froth is characterized by alternately flow portions of liquid and gas. It influences the change of void fractions in time. The results of experimental research of gas void fraction fluctuations in two-phase adiabatic gas-liquid flow in a vertical pipe are presented

Hydrodesulphurization of Light Gas Oil using hydrogen from the Water Gas Shift Reaction

Science.gov (United States)

Alghamdi, Abdulaziz

2009-12-01

The production of clean fuel faces the challenges of high production cost and complying with stricter environmental regulations. In this research, the ability of using a novel technology of upgrading heavy oil to treat Light Gas Oil (LGO) will be investigated. The target of this project is to produce cleaner transportation fuel with much lower cost of production. Recently, a novel process for upgrading of heavy oil has been developed at University of Waterloo. It is combining the two essential processes in bitumen upgrading; emulsion breaking and hydroprocessing into one process. The water in the emulsion is used to generate in situ hydrogen from the Water Gas Shift Reaction (WGSR). This hydrogen can be used for the hydrogenation and hydrotreating reaction which includes sulfur removal instead of the expensive molecular hydrogen. This process can be carried out for the upgrading of the bitumen emulsion which would improve its quality. In this study, the hydrodesulphurization (HDS) of LGO was conducted using in situ hydrogen produced via the Water Gas Shift Reaction (WGSR). The main objective of this experimental study is to evaluate the possibility of producing clean LGO over dispersed molybdenum sulphide catalyst and to evaluate the effect of different promoters and syn-gas on the activity of the dispersed Mo catalyst. Experiments were carried out in a 300 ml Autoclave batch reactor under 600 psi (initially) at 391°C for 1 to 3 hours and different amounts of water. After the hydrotreating reaction, the gas samples were collected and the conversion of carbon monoxide to hydrogen via WGSR was determined using a refinery gas analyzer. The sulphur content in liquid sample was analyzed via X-Ray Fluorescence. Experimental results showed that using more water will enhance WGSR but at the same time inhibits the HDS reaction. It was also shown that the amount of sulfur removed depends on the reaction time. The plan is to investigate the effect of synthesis gas (syngas

Magnetic matrix solid phase dispersion assisted dispersive liquid liquid microextraction of ultra trace polychlorinated biphenyls in water prior to GC-ECD determination

International Nuclear Information System (INIS)

Diao, Chunpeng; Li, Cong; Yang, Xiao; Sun, Ailing; Liu, Renmin

2016-01-01

Magnetic matrix solid phase dispersion (MMSPD) assisted dispersive liquid liquid microextraction (DLLME) was applied to extract ultra traces of polychlorinated biphenyls (PCBs) from water samples prior to gas chromatography with electron capture detection. PCBs in water were adsorbed by micro particles of magnetic bamboo charcoal and then transferred into the elution solvent. PCBs in the elution solvent of the MMSPD were further concentrated into trace volume extraction solvent of the DLLME procedure. Under optimized conditions, good linearity in the range of 0.2–100 ng L"−"1 was obtained with regression coefficients (r) higher than 0.9987. Based on a signal-noise ratio of 3, the limits of detection (LODs) range from 0.05–0.1 ng L"−"1. These LODs are much lower than those of MMSPD or DLLME alone. Relative standard deviations are between 4.9–8.2 %. The method was successfully applied to the determination of PCBs in lake and river water. Relative recoveries were 85.5–117.4 % for the spiked environmental water samples. (author)

Theory of dispersive microlenses

Science.gov (United States)

Herman, B.; Gal, George

1993-01-01

A dispersive microlens is a miniature optical element which simultaneously focuses and disperses light. Arrays of dispersive mircolenses have potential applications in multicolor focal planes. They have a 100 percent optical fill factor and can focus light down to detectors of diffraction spot size, freeing up areas on the focal plane for on-chip analog signal processing. Use of dispersive microlenses allows inband color separation within a pixel and perfect scene registration. A dual-color separation has the potential for temperature discrimination. We discuss the design of dispersive microlenses and present sample results for efficient designs.

Modeled heating and surface erosion comparing motile (gas borne) and stationary (surface coating) inert particle additives

International Nuclear Information System (INIS)

Buckingham, A.C.; Siekhaus, W.J.

1982-01-01

The unsteady, non-similar, chemically reactive, turbulent boundary layer equations are modified for gas plus dispersed solid particle mixtures, for gas phase turbulent combustion reactions and for heterogeneous gas-solid surface erosive reactions. The exterior (ballistic core) edge boundary conditions for the solutions are modified to include dispersed particle influences on core propellant combustion-generated turbulence levels, combustion reactants and products, and reaction-induced, non-isentropic mixture states. The wall surface (in this study it is always steel) is considered either bare or coated with a fixed particle coating which is conceptually non-reactive, insulative, and non-ablative. Two families of solutions are compared. These correspond to: (1) consideration of gas-borne, free-slip, almost spontaneously mobile (motile) solid particle additives which influence the turbulent heat transfer at the uncoated steel surface and, in contrast, (2) consideration of particle-free, gas phase turbulent heat transfer to the insulated surface coated by stationary particles. Significant differences in erosive heat transfer are found in comparing the two families of solutions over a substantial range of interior ballistic flow conditions. The most effective influences on reducing erosive heat transfer appear to favor mobile, gas-borne particle additives

Cefuroxime axetil solid dispersions prepared using solution enhanced dispersion by supercritical fluids.

Science.gov (United States)

Jun, Seoung Wook; Kim, Min-Soo; Jo, Guk Hyun; Lee, Sibeum; Woo, Jong Soo; Park, Jeong-Sook; Hwang, Sung-Joo

2005-12-01

Cefuroxime axetil (CA) solid dispersions with HPMC 2910/PVP K-30 were prepared using solution enhanced dispersion by supercritical fluids (SEDS) in an effort to increase the dissolution rate of poorly water-soluble drugs. Their physicochemical properties in solid state were characterized by differential scanning calorimeter (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared spectrometry (FT-IR) and scanning electron microscopy. No endothermic and characteristic diffraction peaks corresponding to CA were observed for the solid dispersions in DSC and PXRD. FTIR analysis demonstrated the presence of intermolecular hydrogen bonds between CA and HPMC 2910/PVP K-30 in solid dispersions, resulting in the formation of amorphous or non-crystalline CA. Dissolution studies indicated that the dissolution rates were remarkably increased in solid dispersions compared with those in the physical mixture and drug alone. In conclusion, an amorphous or non-crystalline CA solid dispersion prepared using SEDS could be very useful for the formulation of solid dosage forms.

An approach for estimating toxic releases of H2S-containing natural gas.

Science.gov (United States)

Jianwen, Zhang; Da, Lei; Wenxing, Feng

2014-01-15

China is well known being rich in sulfurous natural gas with huge deposits widely distributed all over the country. Due to the toxic nature, the release of hydrogen sulfide-containing natural gas from the pipelines intends to impose serious threats to the human, society and environment around the release sources. CFD algorithm is adopted to simulate the dispersion process of gas, and the results prove that Gaussian plume model is suitable for determining the affected region of the well blowout of sulfide hydrogen-containing natural gas. In accordance with the analysis of release scenarios, the present study proposes a new approach for estimating the risk of hydrogen sulfide poisoning hazards, as caused by sulfide-hydrogen-containing natural gas releases. Historical accident-statistical data from the EGIG (European Gas Pipeline Incident Data Group) and the Britain Gas Transco are integrated into the approach. Also, the dose-load effect is introduced to exploit the hazards' effects by two essential parameters - toxic concentration and exposure time. The approach was applied to three release scenarios occurring on the East-Sichuan Gas Transportation Project, and the individual risk and societal risk are classified and discussed. Results show that societal risk varies significantly with different factors, including population density, distance from pipeline, operating conditions and so on. Concerning the dispersion process of hazardous gas, available safe egress time was studied from the perspective of individual fatality risks. The present approach can provide reliable support for the safety management and maintenance of natural gas pipelines as well as evacuations that may occur after release incidents. Copyright © 2013 Elsevier B.V. All rights reserved.

Gas chromatography-flame ionization determination of benzaldehyde in non-steroidal anti-inflammatory drug injectable formulations using new ultrasound-assisted dispersive liquid-liquid micro extraction

International Nuclear Information System (INIS)

Mashayekhi, H.A.; Pourshamsian, K.

2012-01-01

Summary: In this study, simple and efficient ultrasound-assisted dispersive liquid-liquid micro extraction combined with gas chromatography (GC) was developed for the preconcentration and determination of benzaldehyde in injectable formulations of the non-steroidal anti-inflammatory drugs, diclofenac, Vitamin B-complex and Voltaren injection solutions. Fourteen microliters of toluene was injected slowly into 10 mL home-designed centrifuge glass vial containing an aqueous sample without salt addition that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and 2 macro L of separated toluene was injected into a gas chromatographic system equipped with a flame ionization detector (GC-FID) for analysis. Several factors influencing the extraction efficiency as the nature and volume of organic solvent, extraction temperature, ionic strength and centrifugation time were investigated and optimized. Using optimum extraction conditions a detection limit of 0.3 macro g L/sup -1/ and a good linearity in a calibration range of 2.0-1000 macro g L/sup -1/ were achieved for analyte. This proposed method was successfully applied to the analysis of benzaldehyde in three injection formulations and relative standard deviation (RSD) of analysis (n=3), before spiking with standard benzaldehyde were 3.3, 2.0 and 1.3% for Na-diclofenac, vitamin B-complex and voltaren, respectively and after spiking of standard benzaldehyde (0.3 mg L/sup -1/), the RSD were 6.5, 3.6 and 2.8% for Na-diclofenac, vitamin B-complex and voltaren, respectively. (author)

A sensitivity analysis of volcanic aerosol dispersion in the stratosphere. [Mt. Fuego, Guatemala eruptions

Science.gov (United States)

Butler, C. F.

1979-01-01

A computer sensitivity analysis was performed to determine the uncertainties involved in the calculation of volcanic aerosol dispersion in the stratosphere using a 2 dimensional model. The Fuego volcanic event of 1974 was used. Aerosol dispersion processes that were included are: transport, sedimentation, gas phase sulfur chemistry, and aerosol growth. Calculated uncertainties are established from variations in the stratospheric aerosol layer decay times at 37 latitude for each dispersion process. Model profiles are also compared with lidar measurements. Results of the computer study are quite sensitive (factor of 2) to the assumed volcanic aerosol source function and the large variations in the parameterized transport between 15 and 20 km at subtropical latitudes. Sedimentation effects are uncertain by up to a factor of 1.5 because of the lack of aerosol size distribution data. The aerosol chemistry and growth, assuming that the stated mechanisms are correct, are essentially complete in several months after the eruption and cannot explain the differences between measured and modeled results.

77 FR 441 - Measurement and Control of Combustible Gas Generation and Dispersal

Science.gov (United States)

2012-01-05

... hydrogen that could be generated in different severe accident scenarios.'' The petitioner states that the... different severe accident scenarios.'' The petitioner states that the total quantity of hydrogen could... onset of a severe accident, combustible gas monitoring systems be functional within a timeframe that...

Wave-equation dispersion inversion

KAUST Repository

Li, Jing; Feng, Zongcai; Schuster, Gerard T.

2016-01-01

We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained

Outflow Kinematics Manifested by the Hα Line: Gas Outflows in Type 2 AGNs. IV

Energy Technology Data Exchange (ETDEWEB)

Kang, Daeun; Woo, Jong-Hak; Bae, Hyun-Jin, E-mail: woo@astro.snu.ac.kr [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of)

2017-08-20

Energetic ionized gas outflows driven by active galactic nuclei (AGNs) have been studied as a key phenomenon related to AGN feedback. To probe the kinematics of the gas in the narrow-line region, [O iii] λ 5007 has been utilized in a number of studies showing nonvirial kinematic properties due to AGN outflows. In this paper, we statistically investigate whether the H α emission line is influenced by AGN-driven outflows by measuring the kinematic properties based on the H α line profile and comparing them with those of [O iii]. Using the spatially integrated spectra of ∼37,000 Type 2 AGNs at z < 0.3 selected from the Sloan Digital Sky Survey DR7, we find a nonlinear correlation between H α velocity dispersion and stellar velocity dispersion that reveals the presence of the nongravitational component, especially for AGNs with a wing component in H α . The large H α velocity dispersion and velocity shift of luminous AGNs are clear evidence of AGN outflow impacts on hydrogen gas, while relatively smaller kinematic properties compared to those of [O iii] imply that the observed outflow effect on the H α line is weaker than the case of [O iii].

Stability studies of colloidal silica dispersions in binary solvent mixtures

International Nuclear Information System (INIS)

Bean, Keith Howard

1997-01-01

A series of monodispersed colloidal silica dispersions, of varying radii, has been prepared. These particles are hydrophilic in nature due to the presence of surface silanol groups. Some of the particles have been rendered hydrophobic by terminally grafting n-alkyl (C 18 ) chains to the surface. The stability of dispersions of these various particles has been studied in binary mixtures of liquids, namely (i) ethanol and cyclohexane, and (ii) benzene and n-heptane. The ethanol - cyclohexane systems have been studied using a variety of techniques. Adsorption excess isotherms have been established and electrophoretic mobility measurements have been made. The predicted stability of the dispersions from D.V.L.O. calculations is compared to the observed stability. The hydrophilic silica particles behave as predicted by the calculations, with the zeta potential decreasing and the van der Waals attraction increasing with increasing cyclohexane concentration. The hydrophobic particles behave differently than expected, and the stability as a function of solvent mixture composition does not show a uniform trend. The effect of varying the coverage of C 18 chains on the surface and the effect of trace water in the systems has also been investigated. Organophilic silica dispersions in benzene - n-heptane solvent mixtures show weak aggregation and phase separation into a diffuse 'gas-like' phase and a more concentrated 'liquid-like' phase, analogous to molecular condensation processes. Calculations of the van der Waals potential as a function of solvent mixture composition show good agreement with the observed stability. Determination of the number of particles in each phase at equilibrium allows the energy of flocculation to be determined using a simple thermodynamic relationship. Finally, the addition of an AB block copolymer to organophilic silica particles in benzene n-heptane solvent mixtures has been shown to have a marked effect on the dispersion stability. This stability

Broadband Seismic Studies at the Mallik Gas Hydrate Research Well

Science.gov (United States)

Sun, L. F.; Huang, J.; Lyons-Thomas, P.; Qian, W.; Milkereit, B.; Schmitt, D. R.

2005-12-01

The JAPEX/JNOC/GSC et al. Mallik 3L-38, 4L-38 and 5L-38 scientific wells were drilled in the MacKenzie Delta, NWT, Canada in early 2002 primarily for carrying out initial tests of the feasibility of producing methane gas from the large gas hydrate deposits there [1]. As part of this study, high resolution seismic profiles, a pseudo-3D single fold seismic volume and broadband (8~180Hz) multi-offset vertical seismic profiles (VSP) were acquired at the Mallik site. Here, we provide details on the acquisition program, present the results of the 2D field profile, and discuss the potential implications of these observations for the structure of the permafrost and gas hydrate zones. These zones have long been problematic in seismic imaging due to the lateral heterogeneities. Conventional seismic data processing usually assume a stratified, weak-contrast elastic earth model. However, in permafrost and gas hydrate zones this approximation often becomes invalid. This leads to seismic wave scattering caused by multi-scale perturbation of elastic properties. A 3D viscoelastic finite difference modeling algorithm was employed to simulate wave propagation in a medium with strong contrast. Parameters in this modeling analysis are based on the borehole geophysical log data. In addition, an uncorrelated Vibroseis VSP data set was studied to investigate frequency-dependent absorption and velocity dispersion. Our results indicate that scattering and velocity dispersion are important for a better understanding of attenuation mechanisms in heterogeneous permafrost and gas hydrate zones. [1] Dallimore, S.R., Collett, T.S., Uchida, T., and Weber, M., 2005, Overview of the science program for the Mallik 2002 Gas Hydrate Production Research Well Program; in Scientific Results from Mallik 2002 Gas Hydrate production Research Well Program, MacKenzie Delta, Northwest Territories, Canada, (ed.) S.R. Dallimore and T.S. Collett; Geological Survey of Canada, Bulletin 585, in press.

Hydrodynamics of annular-dispersed flow

International Nuclear Information System (INIS)

Ishii, M.; Kataoka, I.

1982-01-01

The interfacial drag, droplet entrainment, and droplet size distributions are important for detailed mechanistic modeling of annular dispersed two-phase flow. In view of this, recently developed correlations for these parameters are presented and discussed in this paper. The drag correlations for multiple fluid particle systems have been developed from a similarity hypothesis based on the mixture viscosity model. The results show that the drag coefficient depends on the particle Reynolds number and droplet concentration. The onset on droplet entrainment significantly alters the mechanisms of mass, momentum, and energy transfer between the film and gas core flow as well as the transfer between the two-phase mixture and the wall. By assuming the roll wave entrainment mechanism, the correlations for the amount of entrained droplet as well as for the droplet size distribution have been obtained from a simple model in collaboration with a large number of data

Seed dispersal in fens

NARCIS (Netherlands)

Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and

Waves in strong centrifugal fields: dissipationless gas

Science.gov (United States)

Bogovalov, S. V.; Kislov, V. A.; Tronin, I. V.

2015-04-01

Linear waves are investigated in a rotating gas under the condition of strong centrifugal acceleration of the order 106 g realized in gas centrifuges for separation of uranium isotopes. Sound waves split into three families of the waves under these conditions. Dispersion equations are obtained. The characteristics of the waves strongly differ from the conventional sound waves on polarization, velocity of propagation and distribution of energy of the waves in space for two families having frequencies above and below the frequency of the conventional sound waves. The energy of these waves is localized in rarefied region of the gas. The waves of the third family were not specified before. They propagate exactly along the rotational axis with the conventional sound velocity. These waves are polarized only along the rotational axis. Radial and azimuthal motions are not excited. Energy of the waves is concentrated near the wall of the rotor where the density of the gas is largest.

An approach for estimating toxic releases of H{sub 2}S-containing natural gas

Energy Technology Data Exchange (ETDEWEB)

Jianwen, Zhang, E-mail: zhangjw@mail.buct.edu.cn [Lab of Fluid Flow and Heat Transfer, Beijing University of Chemical Technology, Beijing 100029 (China); Institute of Safety Management, Beijing University of Chemical Technology, Beijing 100029 (China); Da, Lei [Lab of Fluid Flow and Heat Transfer, Beijing University of Chemical Technology, Beijing 100029 (China); College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Wenxing, Feng [Pipeline Research Center of PetroChina Company Lmited, 51 Golden Road, Langfang 065000 (China)

2014-01-15

Highlights: • Behavior of H{sub 2}S-containing natural gas exhibits appearance of neutral gas by CFD. • The poisoning hazards of H{sub 2}S by gas pipeline releases are successfully estimated. • An assessment method for available safe egress time is proposed. -- Abstract: China is well known being rich in sulfurous natural gas with huge deposits widely distributed all over the country. Due to the toxic nature, the release of hydrogen sulfide-containing natural gas from the pipelines intends to impose serious threats to the human, society and environment around the release sources. CFD algorithm is adopted to simulate the dispersion process of gas, and the results prove that Gaussian plume model is suitable for determining the affected region of the well blowout of sulfide hydrogen-containing natural gas. In accordance with the analysis of release scenarios, the present study proposes a new approach for estimating the risk of hydrogen sulfide poisoning hazards, as caused by sulfide-hydrogen-containing natural gas releases. Historical accident-statistical data from the EGIG (European Gas Pipeline Incident Data Group) and the Britain Gas Transco are integrated into the approach. Also, the dose-load effect is introduced to exploit the hazards’ effects by two essential parameters – toxic concentration and exposure time. The approach was applied to three release scenarios occurring on the East-Sichuan Gas Transportation Project, and the individual risk and societal risk are classified and discussed. Results show that societal risk varies significantly with different factors, including population density, distance from pipeline, operating conditions and so on. Concerning the dispersion process of hazardous gas, available safe egress time was studied from the perspective of individual fatality risks. The present approach can provide reliable support for the safety management and maintenance of natural gas pipelines as well as evacuations that may occur after

Method for the determination of carboxylic acids in industrial effluents using dispersive liquid-liquid microextraction with injection port derivatization gas chromatography-mass spectrometry.

Science.gov (United States)

Makoś, Patrycja; Fernandes, Andre; Boczkaj, Grzegorz

2017-09-29

The paper presents a new method for the determination of 15 carboxylic acids in samples of postoxidative effluents from the production of petroleum bitumens using ion-pair dispersive liquid-liquid microextraction and gas chromatography coupled to mass spectrometry with injection port derivatization. Several parameters related to the extraction and derivatization efficiency were optimized. Under optimized experimental conditions, the obtained limit of detection and quantification ranged from 0.0069 to 1.12μg/mL and 0.014 to 2.24μg/mL, respectively. The precision (RSD ranged 1.29-6.42%) and recovery (69.43-125.79%) were satisfactory. Nine carboxylic acids at concentrations ranging from 0.10μg/mL to 15.06μg/mL were determined in the raw wastewater and in samples of effluents treated by various oxidation methods. The studies revealed a substantial increase of concentration of benzoic acids, in samples of wastewater after treatment, which confirms the need of carboxylic acids monitoring during industrial effluent treatment processes. Copyright © 2017 Elsevier B.V. All rights reserved.

A new understanding of inert gas narcosis

International Nuclear Information System (INIS)

Zhang Meng; Gao Yi; Fang Haiping

2016-01-01

Anesthetics are extremely important in modern surgery to greatly reduce the patient’s pain. The understanding of anesthesia at molecular level is the preliminary step for the application of anesthetics in clinic safely and effectively. Inert gases, with low chemical activity, have been found to cause anesthesia for centuries, but the mechanism is unclear yet. In this review, we first summarize the progress of theories about general anesthesia, especially for inert gas narcosis, and then propose a new hypothesis that the aggregated rather than the dispersed inert gas molecules are the key to trigger the narcosis to explain the steep dose-response relationship of anesthesia. (topical review)

Fuel Development For Gas-Cooled Fast Reactors

Energy Technology Data Exchange (ETDEWEB)

M. K. Meyer

2006-06-01

The Generation IV Gas-cooled Fast Reactor (GFR) concept is proposed to combine the advantages of high-temperature gas-cooled reactors (such as efficient direct conversion with a gas turbine and the potential for application of high-temperature process heat), with the sustainability advantages that are possible with a fast-spectrum reactor. The latter include the ability to fission all transuranics and the potential for breeding. The GFR is part of a consistent set of gas-cooled reactors that includes a medium-term Pebble Bed Modular Reactor (PBMR)-like concept, or concepts based on the Gas Turbine Modular Helium Reactor (GT-MHR), and specialized concepts such as the Very High Temperature Reactor (VHTR), as well as actinide burning concepts [ ]. To achieve the necessary high power density and the ability to retain fission gas at high temperature, the primary fuel concept proposed for testing in the United States is a dispersion coated fuel particles in a ceramic matrix. Alternative fuel concepts considered in the U.S. and internationally include coated particle beds, ceramic clad fuel pins, and novel ceramic ‘honeycomb’ structures. Both mixed carbide and mixed nitride-based solid solutions are considered as fuel phases.

Chemical countermeasures: Dispersants overview of dispersant use (including application) and research issues

International Nuclear Information System (INIS)

Butler, J.N.

1992-01-01

I will attempt in twenty minutes to summarize the state of research on oil spill dispersants as I perceive it. The expertise I bring to this task includes 20 years of experience with the fate and effects of petroleum in the marine environment, including participation in the 1973 and 1981 NRC studies and three years as chairman of the NRC committee on oil spill dispersants. I More recently I served on a committee of the International Maritime Organization which reviewed the open-quotes Impact of oil and related chemicals and wastes on the marine environment.close quotes That report will be published this year. However, my statements in this paper are not made as a representative of either NRC or IMO. They are my own interpretation of scientific literature cited in the above reviews. Dispersants are chemical formulations, which include surface active agents, designed to decrease the interfacial tension between oil and water. Because the first attempts to disperse oil on a large scale, at the Torrey Canyon spill of 1967, used highly toxic degreasing agents, dispersants have an undeserved reputation for toxicity. In fact, for twenty years dispersant formulations have been developed with an emphasis on reducing their toxicity to marine life. The dispersal of oil in water has been documented in the laboratory by dozens of papers (see references in NRC 1989, pp 70-79), and in the field by dozens of studies (NRC 1989, pp 165- 193). The toxicity of commercial dispersant formulations (NRC 1989, pp 81-123) and dispersed oil (NRC 1989, pp 123-147) has been tested on a wide variety of marine organisms ranging from algae to salmonid fishes. The NRC review has been updated by the IMO/GESAMP (1992) study, but the conclusions remain unchanged

Dispersing powders in liquids

CERN Document Server

Nelson, RD

1988-01-01

This book provides powder technologists with laboratory procedures for selecting dispersing agents and preparing stable dispersions that can then be used in particle size characterization instruments. Its broader goal is to introduce industrial chemists and engineers to the phenomena, terminology, physical principles, and chemical considerations involved in preparing and handling dispersions on a commercial scale. The book introduces novices to: - industrial problems due to improper degree of dispersion; - the nomenclature used in describing particles; - the basic physica

Electron Gas Dynamic Conductivity Tensor on the Nanotube Surface in Magnetic Field

Directory of Open Access Journals (Sweden)

A. M. Ermolaev

2011-01-01

Full Text Available Kubo formula was derived for the electron gas conductivity tensor on the nanotube surface in longitudinal magnetic field considering spatial and time dispersion. Components of the degenerate and nondegenerate electron gas conductivity tensor were calculated. The study has showed that under high electron density, the conductivity undergoes oscillations of de Haas-van Alphen and Aharonov-Bohm types with the density of electrons and magnetic field changes.

Optical absorption in a degenerate Bose-Einstein gas

International Nuclear Information System (INIS)

Yip, S.K.

2002-01-01

We develop a theory on optical absorption in a dilute Bose-Einstein gas at low temperatures. This theory is motivated by the Bogoliubov theory of elementary excitations for this system, and takes into account explicitly the modification of the nature and dispersion of elementary excitations due to Bose-Einstein condensation. Our results show important differences from existing theories

Correlating Gas Transport Parameters and X-ray Computed Tomography Measurements in Porous Media

DEFF Research Database (Denmark)

Naveed, Muhammad; Hamamoto, Shoichiro; Kawamoto, Ken

2013-01-01

physical processes. The objective of this study was to characterize the relationships between gas transport parameters and soil-pore geometry revealed by X-ray CT. Sands of different shapes with a mean particle diameter (d50) ranging from 0.19 to 1.51 mm were used as porous media under both air...... was found between α and tortuosity calculated from gas transport parameters (Equation (Uncited) Image Tools), indicating that gas dispersivity has a linear and inverse relationship with gas diffusivity. A linear relationship was also found between ka and d50/TUMS2, indicating a strong dependency of ka...

Prediction of U3SI2-Al burn-up and SiC/p-AI composition effects on its thermal conductivity using metal matrix composite (MMC) model containing progressive sub-dispersion

International Nuclear Information System (INIS)

Suwardi

2000-01-01

The model takes into account the evolution of constituent volume fraction. Sub-dispersion of disperse contains fission gas bubbles that increase with bum-up. The metal matrix could contain pore and void, a different type of disperse that vary wth time. The model is previously aimed to dispersion-nuclear fuel element. The model consists of a combination of different conductance constituent of both matrix and sub-matrix. Application is carried out to predict the fuel swelling effect on thermal conductivity of U 3 SI 2 -Al dispersion, and to volume fraction effect on conductivity of SiC-particulate reinforced AI matrix. The model shows that both fuel fraction and fission gas swelling decrease the thermal conductivity. During the start-up period of swelling the conductivity increases as aluminum pore close. then decreases most linearly. SiC/p-AI conductivity decreases most linearly with particulate volume fraction, attains 57.6% of pure AI at 50 % v/v. The author conclude that the model developed is applicable for more general MMC. (author)

A dispersion safety factor for LNG vapor clouds

Energy Technology Data Exchange (ETDEWEB)

Vílchez, Juan A. [TIPs – Trámites, Informes y Proyectos, SL, Llenguadoc 10, 08030 Barcelona (Spain); Villafañe, Diana [Centre d’Estudis del Risc Tecnològic (CERTEC), Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Catalonia (Spain); Casal, Joaquim, E-mail: joaquim.casal@upc.edu [Centre d’Estudis del Risc Tecnològic (CERTEC), Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Catalonia (Spain)

2013-02-15

Highlights: ► We proposed a new parameter: the dispersion safety factor (DSF). ► DSF is the ratio between the distance reached by the LFL and that reached by the visible cloud. ► The results for the DSF agree well with the evidence from large scale experiments. ► Two expressions have been proposed to calculate DSF as a function of H{sub R}. ► The DSF may help in indicating the danger of ignition of a LNG vapor cloud. -- Abstract: The growing importance of liquefied natural gas (LNG) to global energy demand has increased interest in the possible hazards associated with its storage and transportation. Concerning the event of an LNG spill, a study was performed on the relationship between the distance at which the lower flammability limit (LFL) concentration occurs and that corresponding to the visible contour of LNG vapor clouds. A parameter called the dispersion safety factor (DSF) has been defined as the ratio between these two lengths, and two expressions are proposed to estimate it. During an emergency, the DSF can be a helpful parameter to indicate the danger of cloud ignition and flash fire.

A dispersion safety factor for LNG vapor clouds

International Nuclear Information System (INIS)

Vílchez, Juan A.; Villafañe, Diana; Casal, Joaquim

2013-01-01

Highlights: ► We proposed a new parameter: the dispersion safety factor (DSF). ► DSF is the ratio between the distance reached by the LFL and that reached by the visible cloud. ► The results for the DSF agree well with the evidence from large scale experiments. ► Two expressions have been proposed to calculate DSF as a function of H R . ► The DSF may help in indicating the danger of ignition of a LNG vapor cloud. -- Abstract: The growing importance of liquefied natural gas (LNG) to global energy demand has increased interest in the possible hazards associated with its storage and transportation. Concerning the event of an LNG spill, a study was performed on the relationship between the distance at which the lower flammability limit (LFL) concentration occurs and that corresponding to the visible contour of LNG vapor clouds. A parameter called the dispersion safety factor (DSF) has been defined as the ratio between these two lengths, and two expressions are proposed to estimate it. During an emergency, the DSF can be a helpful parameter to indicate the danger of cloud ignition and flash fire

Gas hydrates forming and decomposition conditions analysis

Directory of Open Access Journals (Sweden)

А. М. Павленко

2017-07-01

Full Text Available The concept of gas hydrates has been defined; their brief description has been given; factors that affect the formation and decomposition of the hydrates have been reported; their distribution, structure and thermodynamic conditions determining the gas hydrates formation disposition in gas pipelines have been considered. Advantages and disadvantages of the known methods for removing gas hydrate plugs in the pipeline have been analyzed, the necessity of their further studies has been proved. In addition to the negative impact on the process of gas extraction, the hydrates properties make it possible to outline the following possible fields of their industrial use: obtaining ultrahigh pressures in confined spaces at the hydrate decomposition; separating hydrocarbon mixtures by successive transfer of individual components through the hydrate given the mode; obtaining cold due to heat absorption at the hydrate decomposition; elimination of the open gas fountain by means of hydrate plugs in the bore hole of the gushing gasser; seawater desalination, based on the hydrate ability to only bind water molecules into the solid state; wastewater purification; gas storage in the hydrate state; dispersion of high temperature fog and clouds by means of hydrates; water-hydrates emulsion injection into the productive strata to raise the oil recovery factor; obtaining cold in the gas processing to cool the gas, etc.

Effects of nickel-oxide nanoparticle pre-exposure dispersion status on bioactivity in the mouse lung.

Science.gov (United States)

Sager, Tina; Wolfarth, Michael; Keane, Michael; Porter, Dale; Castranova, Vincent; Holian, Andrij

2016-01-01

Nanotechnology is emerging as one of the world's most promising new technologies. From a toxicology perspective, nanoparticles possess two features that promote their bioactivity. The first involves physical-chemical characteristics of the nanoparticle, which include the surface area of the nanoparticle. The second feature is the ability of the nanoparticle to traverse cell membranes. These two important nanoparticle characteristics are greatly influenced by placing nanoparticles in liquid medium prior to animal exposure. Nanoparticles tend to agglomerate and clump in suspension, making it difficult to reproducibly deliver them for in vivo or in vitro experiments, possibly affecting experimental variability. Thus, we hypothesize that nanoparticle dispersion status will correlate with the in vivo bioactivity/toxicity of the particle. To test our hypothesis, nano-sized nickel oxide was suspended in four different dispersion media (phosphate-buffered saline (PBS), dispersion medium (DM), a combination of dipalmitoyl-phosphatidyl choline (DPPC) and albumin in concentrations that mimic diluted alveolar lining fluid), Survanta®, or pluronic (Pluronic F-68). Well-dispersed and poorly dispersed suspensions were generated in each media by varying sonication time on ice utilizing a Branson Sonifer 450 (25W continuous output, 20 min or 5 min, respectively). Mice (male, C57BL/6J, 7-weeks-old) were given 0-80 µg/mouse of nano-sized nickel oxide in the different states of dispersion via pharyngeal aspiration. At 1 and 7 d post-exposure, mice underwent whole lung lavage to assess pulmonary inflammation and injury as a function of dispersion status, dose and time. The results show that pre-exposure dispersion status correlates with pulmonary inflammation and injury. These results indicate that a greater degree of pre-exposure dispersion increases pulmonary inflammation and cytotoxicity, as well as decreases in the integrity of the blood-gas barrier in the lung.

Seed dispersal in fens

Science.gov (United States)

Middleton, B.; Van Diggelen, R.; Jensen, K.

2006-01-01

Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

Wave-equation dispersion inversion

KAUST Repository

Li, Jing

2016-12-08

We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.

Greenhouse gas emission quantification from wastewater treatment plants, using a tracer gas dispersion method

DEFF Research Database (Denmark)

Delre, Antonio; Mønster, Jacob; Scheutz, Charlotte

2017-01-01

Plant-integrated methane (CH4) and nitrous oxide (N2O) emission quantifications were performed at five Scandinavian wastewater treatment plants, using a ground-based remote sensing approach that combines a controlled release of tracer gas from the plant with downwind concentration measurements. CH4...... emission factors were between 1 and 21% of CH4 production, and between 0.2 and 3.2% of COD influent. The main CH4 emitting sources at the five plants were sludge treatment and energy production units. The lowest CH4 emission factors were obtained at plants with enclosed sludge treatment and storage units...... in international guidelines. This study showed that measured CH4 and N2O emission rates from wastewater treatment plants were plant-specific and that emission rates estimated using models in current guidelines, mainly meant for reporting emissions on the country scale, were unsuitable for Scandinavian plant...

The Norwegian Sea trial 1995 - offshore testing of two dispersant application systems and simulation of an underwater pipeline leakage - a summary paper

International Nuclear Information System (INIS)

Brandvik, P.J.; Strom-Kristiansen, T.; Lewis, A.; Daling, P.S.; Reed, M.; Rye, H.; Jensen, H.

1996-01-01

A summary of the major findings from several reports regarding oil spills at sea, was presented. Topics included oil weathering, remote sensing, underwater plume behaviour, oil spill drifters and underwater oil concentrations. To study plume behaviour, oil was released from 100 metres depth. The objective of the underwater release was to simulate a pipeline leakage without gas and high pressure and to study the behaviour of the rising plume. The different methods of applying dispersants were evaluated to determine their effectiveness. It was concluded that, if correctly applied, a dispersant is capable of dispersing the thick oil totally into the seawater within 10 to 30 minutes after treatment. A slick treated with dispersant applied from a helicopter bucket was most effective. 19 refs., 6 figs

Spurious dispersion effects at FLASH

International Nuclear Information System (INIS)

Prat, Eduard

2009-07-01

The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

Spurious dispersion effects at FLASH

Energy Technology Data Exchange (ETDEWEB)

Prat, Eduard

2009-07-15

The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

Spatially extended and high-velocity dispersion molecular component in spiral galaxies: Single-dish versus interferometric observations

International Nuclear Information System (INIS)

Caldú-Primo, Anahi; Walter, Fabian; Schruba, Andreas; Leroy, Adam; Bolatto, Alberto D.; Vogel, Stuart

2015-01-01

Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%–74% for NGC 4736 and 81%–92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ∼(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(∼1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (∼3″ or ∼100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

Metapopulation extinction risk: dispersal's duplicity.

Science.gov (United States)

Higgins, Kevin

2009-09-01

Metapopulation extinction risk is the probability that all local populations are simultaneously extinct during a fixed time frame. Dispersal may reduce a metapopulation's extinction risk by raising its average per-capita growth rate. By contrast, dispersal may raise a metapopulation's extinction risk by reducing its average population density. Which effect prevails is controlled by habitat fragmentation. Dispersal in mildly fragmented habitat reduces a metapopulation's extinction risk by raising its average per-capita growth rate without causing any appreciable drop in its average population density. By contrast, dispersal in severely fragmented habitat raises a metapopulation's extinction risk because the rise in its average per-capita growth rate is more than offset by the decline in its average population density. The metapopulation model used here shows several other interesting phenomena. Dispersal in sufficiently fragmented habitat reduces a metapopulation's extinction risk to that of a constant environment. Dispersal between habitat fragments reduces a metapopulation's extinction risk insofar as local environments are asynchronous. Grouped dispersal raises the effective habitat fragmentation level. Dispersal search barriers raise metapopulation extinction risk. Nonuniform dispersal may reduce the effective fraction of suitable habitat fragments below the extinction threshold. Nonuniform dispersal may make demographic stochasticity a more potent metapopulation extinction force than environmental stochasticity.

a Real-Time GIS Platform for High Sour Gas Leakage Simulation, Evaluation and Visualization

Science.gov (United States)

Li, M.; Liu, H.; Yang, C.

2015-07-01

The development of high-sulfur gas fields, also known as sour gas field, is faced with a series of safety control and emergency management problems. The GIS-based emergency response system is placed high expectations under the consideration of high pressure, high content, complex terrain and highly density population in Sichuan Basin, southwest China. The most researches on high hydrogen sulphide gas dispersion simulation and evaluation are used for environmental impact assessment (EIA) or emergency preparedness planning. This paper introduces a real-time GIS platform for high-sulfur gas emergency response. Combining with real-time data from the leak detection systems and the meteorological monitoring stations, GIS platform provides the functions of simulating, evaluating and displaying of the different spatial-temporal toxic gas distribution patterns and evaluation results. This paper firstly proposes the architecture of Emergency Response/Management System, secondly explains EPA's Gaussian dispersion model CALPUFF simulation workflow under high complex terrain and real-time data, thirdly explains the emergency workflow and spatial analysis functions of computing the accident influencing areas, population and the optimal evacuation routes. Finally, a well blow scenarios is used for verify the system. The study shows that GIS platform which integrates the real-time data and CALPUFF models will be one of the essential operational platforms for high-sulfur gas fields emergency management.

Dye-assisted dispersion of single-walled carbon nanotubes for solution fabrication of NO2 sensors

Directory of Open Access Journals (Sweden)

M. M. Ramli

2012-09-01

Full Text Available Direct golden orange dye molecules were used as a dispersing agent to produce suspensions of single-walled carbon nanotubes (SWCNTs in water. Uniform, thin film networks were fabricated by vacuum filtration using different concentrations of SWCNT and transferred subsequently to glass substrates. The dispersion efficiency was compared to other surfactants. Measurement of the sheet resistance as a function of SWCNT concentration showed a transition from 2D percolation to 3D conduction behaviour when the concentration of SWCNTs exceeded 0.001 mg/mL. The electrical response to NO2 gas exposure was investigated as a function of temperature and an optimum response was observed at 200°C.

Identification and elucidation of anthropogenic source contribution in PM10 pollutant: Insight gain from dispersion and receptor models.

Science.gov (United States)

Roy, Debananda; Singh, Gurdeep; Yadav, Pankaj

2016-10-01

Source apportionment study of PM 10 (Particulate Matter) in a critically polluted area of Jharia coalfield, India has been carried out using Dispersion model, Principle Component Analysis (PCA) and Chemical Mass Balance (CMB) techniques. Dispersion model Atmospheric Dispersion Model (AERMOD) was introduced to simplify the complexity of sources in Jharia coalfield. PCA and CMB analysis indicates that monitoring stations near the mining area were mainly affected by the emission from open coal mining and its associated activities such as coal transportation, loading and unloading of coal. Mine fire emission also contributed a considerable amount of particulate matters in monitoring stations. Locations in the city area were mostly affected by vehicular, Liquid Petroleum Gas (LPG) & Diesel Generator (DG) set emissions, residential, and commercial activities. The experimental data sampling and their analysis could aid understanding how dispersion based model technique along with receptor model based concept can be strategically used for quantitative analysis of Natural and Anthropogenic sources of PM 10 . Copyright © 2016. Published by Elsevier B.V.

A simple and sensitive approach to quantify methyl farnesoate in whole arthropods by matrix-solid phase dispersion and gas chromatography-mass spectrometry.

Science.gov (United States)

Montes, Rosa; Rodil, Rosario; Neuparth, Teresa; Santos, Miguel M; Cela, Rafael; Quintana, José Benito

2017-07-28

Methyl farnesoate (MF) is an arthropod hormone that plays a key role in the physiology of several arthropods' classes being implicated in biological processes such as molting and reproduction. The development of an analytical technique to quantify the levels of this compound in biological tissues can be of major importance for the field of aquaculture/apiculture conservation and in endocrine disruption studies. Therefore, the aim of this study was to develop a simple and sensitive method to measure native levels of MF in the tissue of three representative species from different arthropods classes with environmental and/or economic importance. Thus, a new approach using whole organisms and the combination of matrix solid-phase dispersion with gas chromatography coupled to mass spectrometry was developed. This method allows quantifying endogenous MF at low levels (LOQs in the 1.2-3.1ng/g range) in three arthropod species, and could be expanded to additional arthropod classes. The found levels ranged between 2 and 12ng/g depending on the studied species and gender. The overall recovery of the method was evaluated and ranged between 69 and 96%. Copyright © 2017 Elsevier B.V. All rights reserved.

Dispersion stability of thermal nanofluids

Directory of Open Access Journals (Sweden)

Fan Yu

2017-10-01

Full Text Available Thermal nanofluids, the engineered fluids with dispersed functional nanoparticles, have exhibited extraordinary thermophysical properties and added functionalities, and thus have enabled a broad range of important applications. The poor dispersion stability of thermal nanofluids, however, has been considered as a long-existing issue that limits their further development and practical application. This review overviews the recent efforts and progresses in improving the dispersion stability of thermal nanofluids such as mechanistic understanding of dispersion behavior of nanofluids, examples of both water-based and oil-based nanofluids, strategies to stabilize nanofluids, and characterization techniques for dispersion behavior of nanofluids. Finally, on-going research needs, and possible solutions to research challenges and future research directions in exploring stably dispersed thermal nanofluids are discussed. Keywords: Thermal nanofluids, Dispersion, Aggregation, Electrostatic stabilization, Steric stabilization

Characterization of nanocarbons (nanotubes and nanofibers) by Inverse Gas Chromatography

Energy Technology Data Exchange (ETDEWEB)

DIaz, E [Department of Chemical Engineering and Environmental Technology, University of Oviedo, Julian ClaverIa s/n, 33006 Oviedo (Spain); Ordonez, S [Department of Chemical Engineering and Environmental Technology, University of Oviedo, Julian ClaverIa s/n, 33006 Oviedo (Spain); Vega, A [Department of Chemical Engineering and Environmental Technology, University of Oviedo, Julian ClaverIa s/n, 33006 Oviedo (Spain)

2007-04-15

The adsorption of different alkanes (linear and cyclic), aromatics and chlorohydrocarbons on non-microporous carbons-carbon nanotubes (CNTs) and carbon nanofibres (CNFs)- was studied in this work by inverse gas chromatography (IGC). Capacity of adsorption was derived from the isotherms of adsorption, whereas thermodynamic properties (enthalpy of adsorption, surface free energy characteristics) have been determined from chromatographic retention data. CNTs present the highest adsorption capacity. From surface free energy data, enthalpies of adsorption of polar compounds were divided into dispersive and specific contributions. The interactions of cyclic (benzene and cyclohexane) and chlorinated compounds (trichloroethylene, tetrachloroethylene and chloroform) with the surfaces are mainly dispersive over all the carbons tested, being CNTs the material with the highest dispersive contribution. Adsorption parameters were correlated with morphological and chemical properties of the materials.

Hydrodynamic disperser

Energy Technology Data Exchange (ETDEWEB)

Bulatov, A.I.; Chernov, V.S.; Prokopov, L.I.; Proselkov, Yu.M.; Tikhonov, Yu.P.

1980-01-15

A hydrodynamic disperser is suggested which contains a housing, slit nozzles installed on a circular base arranged opposite from each other, resonators secured opposite the nozzle and outlet sleeve. In order to improve the effectiveness of dispersion by throttling the flow, each resonator is made in the form of a crimped plate with crimpings that decrease in height in a direction towards the nozzle.

Mapping the Fluid Pathways and Permeability Barriers of a Large Gas Hydrate Reservoir

Science.gov (United States)

Campbell, A.; Zhang, Y. L.; Sun, L. F.; Saleh, R.; Pun, W.; Bellefleur, G.; Milkereit, B.

2012-12-01

An understanding of the relationship between the physical properties of gas hydrate saturated sedimentary basins aids in the detection, exploration and monitoring one of the world's upcoming energy resources. A large gas hydrate reservoir is located in the MacKenzie Delta of the Canadian Arctic and geophysical logs from the Mallik test site are available for the gas hydrate stability zone (GHSZ) between depths of approximately 850 m to 1100 m. The geophysical data sets from two neighboring boreholes at the Mallik test site are analyzed. Commonly used porosity logs, as well as nuclear magnetic resonance, compressional and Stoneley wave velocity dispersion logs are used to map zones of elevated and severely reduced porosity and permeability respectively. The lateral continuity of horizontal permeability barriers can be further understood with the aid of surface seismic modeling studies. In this integrated study, the behavior of compressional and Stoneley wave velocity dispersion and surface seismic modeling studies are used to identify the fluid pathways and permeability barriers of the gas hydrate reservoir. The results are compared with known nuclear magnetic resonance-derived permeability values. The aim of investigating this heterogeneous medium is to map the fluid pathways and the associated permeability barriers throughout the gas hydrate stability zone. This provides a framework for an understanding of the long-term dissociation of gas hydrates along vertical and horizontal pathways, and will improve the knowledge pertaining to the production of such a promising energy source.

Dispersal and metapopulation stability

Directory of Open Access Journals (Sweden)

Shaopeng Wang

2015-10-01

Full Text Available Metapopulation dynamics are jointly regulated by local and spatial factors. These factors may affect the dynamics of local populations and of the entire metapopulation differently. Previous studies have shown that dispersal can stabilize local populations; however, as dispersal also tends to increase spatial synchrony, its net effect on metapopulation stability has been controversial. Here we present a simple metapopulation model to study how dispersal, in interaction with other spatial and local processes, affects the temporal variability of metapopulations in a stochastic environment. Our results show that in homogeneous metapopulations, the local stabilizing and spatial synchronizing effects of dispersal cancel each other out, such that dispersal has no effect on metapopulation variability. This result is robust to moderate heterogeneities in local and spatial parameters. When local and spatial dynamics exhibit high heterogeneities, however, dispersal can either stabilize or destabilize metapopulation dynamics through various mechanisms. Our findings have important theoretical and practical implications. We show that dispersal functions as a form of spatial intraspecific mutualism in metapopulation dynamics and that its effect on metapopulation stability is opposite to that of interspecific competition on local community stability. Our results also suggest that conservation corridors should be designed with appreciation of spatial heterogeneities in population dynamics in order to maximize metapopulation stability.

Ammonia Gas Sensing Behavior of Tanninsulfonic Acid Doped Polyaniline-TiO2 Composite

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Venu Gopal Bairi

2015-10-01

Full Text Available A highly active tannin doped polyaniline-TiO2 composite ammonia gas sensor was developed and the mechanism behind the gas sensing activity was reported for the first time. A tanninsulfonic acid doped polyaniline (TANIPANI-titanium dioxide nanocomposite was synthesized by an in situ polymerization of aniline in the presence of tanninsulfonic acid and titanium dioxide nanoparticles. X-ray diffraction and thermogravimetric analysis were utilized to determine the incorporation of TiO2 in TANIPANI matrix. UV-Visible and infrared spectroscopy studies provided information about the electronic interactions among tannin, polyaniline, and TiO2. Scanning electron microscopy (SEM along with energy dispersive X-ray spectroscopy (EDS and atomic force microscopy (AFM surface analysis techniques were used to investigate the metal oxide dispersions inside polyaniline matrix. Gas sensors were prepared by spin coating solutions of TANIPANI-TiO2 and TANIPANI composites onto glass slides. Sensors were tested at three different concentrations (20 ppm, 40 ppm, and 60 ppm of ammonia gas at ambient temperature conditions by measuring the changes in surface resistivity of the films with respect to time. Ammonia gas sensing plots are presented showing the response values, response times and recovery times. The TANIPANI-TiO2 composite exhibited better response and shorter recovery times when compared to TANIPANI control and other polyaniline composites that have been reported in the literature. For the first time a proposed mechanism of gas sensing basing on the polaron band localization and its effects on the gas sensing behavior of polyaniline are reported.

CRUNCH, Dispersion Model for Continuous Dense Vapour Release in Atmosphere

International Nuclear Information System (INIS)

Jagger, S.F.

1987-01-01

1 - Description of program or function: The situation modelled is as follows. A dense gas emerges from a source such that it can be considered to emerge through a rectangular area, placed in the vertical plane and perpendicular to the plume direction, which assumes that of the ambient wind. The gas flux at the source, and in every plane perpendicular to the plume direction, is constant in time and a stationary flow field has been attained. For this to apply, the characteristic time of release must be much larger than that for dispersal of the contaminant. The plume can be thought to consist of a number of rectangular elements or 'puffs' emerging from the source at regular time intervals. The model follows the development of these puffs at a series of downwind points. These puffs are immediately assumed to advect with the ambient wind at their half-height. The plume also slumps due to the action of gravity and is allowed to entrain air through its sides and top surface. Spreading of a fluid element is caused by pressure differences across this element and since the pressure gradient in the wind direction is small, the resulting pressure differences and slumping velocities are small also, thus permitting this convenient approximation. Initially, as the plume slumps, its vertical dimension decreases and with it the slumping velocity and advection velocity. Thus the plume advection velocity varies as a function of downwind distance. With the present steady state modelling, and to satisfy continuity constraints, there must be consequent adjustment of plume height. Calculation of this parameter from the volume flux ensures this occurs. As the cloud height begins to grow, the advection velocity increases and the plume height decreases accordingly. With advection downwind, the cloud gains buoyancy by entraining air and, if the cloud is cold, by absorbing heat from the ground. Eventually the plume begins to disperse as would a passive pollutant, through the action of

Dispersion of multi-walled carbon nanotubes in biocompatible dispersants

International Nuclear Information System (INIS)

Piret, J.-P.; Detriche, S.; Vigneron, R.; Vankoningsloo, S.; Rolin, S.; Mejia Mendoza, J. H.; Masereel, B.; Lucas, S.; Delhalle, J.; Luizi, F.; Saout, C.; Toussaint, O.

2010-01-01

Owing to their phenomenal electrical and mechanical properties, carbon nanotubes (CNT) have been an area of intense research since their discovery in 1991. Different applications for these nanoparticles have been proposed, among others, in electronics and optics but also in the medical field. In parallel, emerging studies have suggested potential toxic effects of CNT while others did not, generating some conflicting outcomes. These discrepancies could be, in part, due to different suspension approaches used and to the agglomeration state of CNT in solution. In this study, we described a standardized protocol to obtain stable CNT suspensions, using two biocompatible dispersants (Pluronic F108 and hydroxypropylcellulose) and to estimate the concentration of CNT in solution. CNT appear to be greatly individualized in these two dispersants with no detection of remaining bundles or agglomerates after sonication and centrifugation. Moreover, CNT remained perfectly dispersed when added to culture medium used for in vitro cell experiments. We also showed that Pluronic F108 is a better dispersant than hydroxypropylcellulose. In conclusion, we have developed a standardized protocol using biocompatible surfactants to obtain reproducible and stable multi-walled carbon nanotubes suspensions which can be used for in vitro or in vivo toxicological studies.

Enhanced Dispersion and Removal of Ammonia Emitted from a Poultry House with a Vegetative Environmental Buffer

Directory of Open Access Journals (Sweden)

Kyoung S. Ro

2018-03-01

Full Text Available Vegetative environmental buffers (VEBs, which are composed of tolerant trees, shrubs, and tall grasses, can be used to control and reduce the transport of ammonia (NH3 emissions from animal feeding operations (AFOs. However, the effectiveness of VEBs has not been quantitated. In this study, we measure the dispersion and removal of NH3 in simulated emissions from a small broiler house that was equipped with a VEB. The dispersion enhancement due to the VEB was estimated by comparing the measured downwind concentration of the co-released tracer gas, methane (CH4, to the theoretical CH4 concentrations at the same distance downwind without the VEB. The accuracy of the theoretical downwind concentrations calculated using the forward Lagrangian stochastic (fLS technique was 95%, which was validated by comparing the measured and calculated CH4 concentrations in a separate experiment without the VEB. The VEB enhanced the dispersion of CH4 and reduced the downwind concentration to 63% of the theoretical concentration. In addition to dispersion, the VEB removed another 22% of the NH3, resulting in a net 51% decrease of the theoretical downwind concentration. These results clearly demonstrated that the VEB was effective both in dispersing and removing NH3 emitted from the broiler house.

Data Assimilation in Air Contaminant Dispersion Using a Particle Filter and Expectation-Maximization Algorithm

Directory of Open Access Journals (Sweden)

Rongxiao Wang

2017-09-01

Full Text Available The accurate prediction of air contaminant dispersion is essential to air quality monitoring and the emergency management of contaminant gas leakage incidents in chemical industry parks. Conventional atmospheric dispersion models can seldom give accurate predictions due to inaccurate input parameters. In order to improve the prediction accuracy of dispersion models, two data assimilation methods (i.e., the typical particle filter & the combination of a particle filter and expectation-maximization algorithm are proposed to assimilate the virtual Unmanned Aerial Vehicle (UAV observations with measurement error into the atmospheric dispersion model. Two emission cases with different dimensions of state parameters are considered. To test the performances of the proposed methods, two numerical experiments corresponding to the two emission cases are designed and implemented. The results show that the particle filter can effectively estimate the model parameters and improve the accuracy of model predictions when the dimension of state parameters is relatively low. In contrast, when the dimension of state parameters becomes higher, the method of particle filter combining the expectation-maximization algorithm performs better in terms of the parameter estimation accuracy. Therefore, the proposed data assimilation methods are able to effectively support air quality monitoring and emergency management in chemical industry parks.

Subtracted Dispersion Relations for In-medium Meson Correlators in QCD Sum Rules

Energy Technology Data Exchange (ETDEWEB)

Florkowski, W; Broniowski, W [The H. Niewodniczanski Institute of Nuclear Physics, Cracow (Poland)

1999-01-01

We analyze subtracted dispersion relations for meson correlators at finite baryon density and temperature. Such relations are needed for QCD sum rules. We point out that importance of scattering terms, as well as finite, well-defined subtraction constants. Both are necessary for consistency, in particular for the equality of the longitudinal and transverse correlators in the limit of the vanishing three-momentum of mesons relative to the medium. We present detailed calculations in various mesonic channels of the Fermi gas of nucleons. (author)

Method and apparatus for producing synthesis gas

Science.gov (United States)

Hemmings, John William; Bonnell, Leo; Robinson, Earl T.

2010-03-03

A method and apparatus for reacting a hydrocarbon containing feed stream by steam methane reforming reactions to form a synthesis gas. The hydrocarbon containing feed is reacted within a reactor having stages in which the final stage from which a synthesis gas is discharged incorporates expensive high temperature materials such as oxide dispersed strengthened metals while upstream stages operate at a lower temperature allowing the use of more conventional high temperature alloys. Each of the reactor stages incorporate reactor elements having one or more separation zones to separate oxygen from an oxygen containing feed to support combustion of a fuel within adjacent combustion zones, thereby to generate heat to support the endothermic steam methane reforming reactions.

Tracer dispersion - experiment and CFD

International Nuclear Information System (INIS)

Zitny, R.

2004-01-01

Description of tracer distribution by means of dispersion models is a method successfully used in process engineering for fifty years. Application of dispersion models in reactor engineering for characterization of flows in column apparatus, heat exchangers, etc. is summarized and experimental tracer techniques as well as CFD methods for dispersion coefficients evaluation are discussed. Possible extensions of thermal axial dispersion model (ADM) and a core-wall ADM model suitable for description of tracer dispersion in laminar flows are suggested as well as CFD implementation as 1D finite elements. (author)

Quantum mechanics of the fractional-statistics gas: Random-phase approximation

International Nuclear Information System (INIS)

Dai, Q.; Levy, J.L.; Fetter, A.L.; Hanna, C.B.; Laughlin, R.B.

1992-01-01

A description of the fractional-statistics gas based on the complete summation of Hartree, Fock, ladder and bubble diagrams is presented. The superfluid properties identified previously in the random-phase-approximation (RPA) calculation of Fetter, Hanna, and Laughlin [Phys. Rev. B 39, 9679 (1989)] are substantially confirmed. The discrepancy between the RPA sound speed and the Hartree-Fock bulk modulus is found to be eliminated. The unusual Hall-effect behavior is found to vanish for the Bose gas test case but not for the fractional-statistics gas, implying that it is physically correct. Excellent agreement is obtained with the collective-mode dispersion obtained numerically by Xie, He, and Das Sarma [Phys. Rev. Lett. 65, 649 (1990)

Gas dynamics in strong centrifugal fields

OpenAIRE

Bogovalov, S. V.; Kislov, V. A.; Tronin, I. V.

2017-01-01

Dynamics of waves generated by scopes in gas centrifuges (GC) for isotope separation is considered. The centrifugal acceleration in the GC reaches values of the order of $10^6$g. The centrifugal and Coriolis forces modify essentially the conventional sound waves. Three families of the waves with different polarisation and dispersion exist in these conditions. Dynamics of the flow in the model GC Iguasu is investigated numerically. Comparison of the results of the numerical modelling of the wa...

Numerical Analysis of Molten Corium Dispersion during Hypothetical High-Pressure Accidents in APR1400 Nuclear Power Plant

International Nuclear Information System (INIS)

Kim, Jong Tae; Ha, Kwang Soon; Kim, Sang Baik; Kim, Hee Dong; Jeong, Jae Sik

2010-01-01

is not clearly known. During the evaluation of containment integrity by DCH in KNGR (synonym of APR1400), the dispersion correlation developed from experiments for Young-Gang 3 and 4 and Kori-1 cavity geometries was applied in a two-cell equilibrium (TCE) modeling. As can be expected, the benefit of the convolute cavity geometry of APR1400 could not be resolved once the correlation is used. In order to verify that using the correlation for APR1400 is conservative in view of the evaluation of the containment integrity by DCH, corium dispersion in the APR1400 containment was simulated by using MC3D code. The MC3D code is a two-phase analysis code based on Eulerian four-fields for melt jet, melt droplets, water and gas mixture of vapor and noncondensable gas. The dispersion rates of the corium melt depending on the RPV pressure were obtained from the MC3D analyses and the values specific to the APR1400 cavity geometry were compared to the correlation

Meteorological perspective on intermediate range atmospheric dispersion

International Nuclear Information System (INIS)

Van der Hoven, I.

1981-01-01

The intermediate range of atmospheric transport and diffusion is defined as those dispersion processes which take place at downwind distances of 10 to 100 kilometers from pollutant sources. Meteorologists often define this range as the mesoscale. It is the range of distances where certain environmental assessments are of concern such as the determination of significant deterioration of visibility, the effect of effluent releases from tall stacks, and the effect of pollutant sources in rural settings upon the more distant urban centers. Atmospheric diffusion theory is based on steady state conditions and spatial homogeniety. Techniques must be developed to measure the inhomogenieties, models must be devised to account for the complexities, and a data base consisting of appropriate measured meteorological parameters concurrent with tracer gas concentrations should be collected

Influence of leakage flow on the behaviour of gas behind a blockage in LMFBR subassembly geometry

International Nuclear Information System (INIS)

Fukuzawa, Y.

1980-07-01

Observations were made of the behaviour of gas behind a uniform porous 21% corner blockage within a pin-bundle of LMFBR subassembly geometry. The main parameter of the experiment was the leakage flow rate through the blockage. The behaviour of gas is significantly influenced by the leakage flow rate. The measured size and residence time of a gas cavity formed behind the blockage are shown and the mechanisms of the gas cavity dispersion by the leakage flow discussed by using a simple model of the liquid flow distribution behind the blockage. (orig.) [de

Numerical predictions of particle dispersed two-phase flows, using the LSD and SSF models

International Nuclear Information System (INIS)

Avila, R.; Cervantes de Gortari, J.; Universidad Nacional Autonoma de Mexico, Mexico City. Facultad de Ingenieria)

1988-01-01

A modified version of a numerical scheme which is suitable to predict parabolic dispersed two-phase flow, is presented. The original version of this scheme was used to predict the test cases discussed during the 3rd workshop on TPF predictions in Belgrade, 1986. In this paper, two particle dispersion models are included which use the Lagrangian approach predicting test case 1 and 3 of the 4th workshop. For the prediction of test case 1 the Lagrangian Stochastic Deterministic model (LSD) is used providing acceptable good results of mean and turbulent quantities for both solid and gas phases; however, the computed void fraction distribution is not in agreement with the measurements at locations away from the inlet, especially near the walls. Test case 3 is predicted using both the LSD and the Stochastic Separated Flow (SSF) models. It was found that the effects of turbulence modulation are large when the LSD model is used, whereas the particles have a negligible influence on the continuous phase if the SSF model is utilized for the computations. Predictions of gas phase properties based on both models agree well with measurements; however, the agreement between calculated and measured solid phase properties is less satisfactory. (orig.)

Characterization of the Microstructure of Irradiated U-Mo Dispersion Fuel with a Matrix that Contains Si

International Nuclear Information System (INIS)

Keiser, Jr. D.D.; Robinson, A.B.; Jue, J.F.; Medvedev, P.; Finlay, M.R.

2009-01-01

RERTR U-Mo dispersion fuel plates are being developed for application in research reactors throughout the world. Of particular interest is the irradiation performance of U-Mo dispersion fuels with Si added to the Al matrix. Si is added to improve the performance of U-Mo dispersion fuels. Microstructural examinations have been performed on fuel plates with Al-2Si matrix after irradiation to around 50% LEU burnup. Si-rich layers were observed in many areas around the various U-7Mo fuel particles. In one local area of one of the samples, where the Si-rich layer had developed into a layer devoid of Si, relatively large fission gas bubbles were observed in the interaction phase. There may be a connection between the growth of these bubbles and the amount of Si present in the interaction layer. Overall, it was found that having Si-rich layers around the fuel particles after fuel plate fabrication positively impacted the overall performance of the fuel plate

The SAMI Galaxy Survey: gas content and interaction as the drivers of kinematic asymmetry

Science.gov (United States)

Bloom, J. V.; Croom, S. M.; Bryant, J. J.; Schaefer, A. L.; Bland-Hawthorn, J.; Brough, S.; Callingham, J.; Cortese, L.; Federrath, C.; Scott, N.; van de Sande, J.; D'Eugenio, F.; Sweet, S.; Tonini, C.; Allen, J. T.; Goodwin, M.; Green, A. W.; Konstantopoulos, I. S.; Lawrence, J.; Lorente, N.; Medling, A. M.; Owers, M. S.; Richards, S. N.; Sharp, R.

2018-05-01

In order to determine the causes of kinematic asymmetry in the Hα gas in the SAMI (Sydney-AAO Multi-object IFS) Galaxy Survey sample, we investigate the comparative influences of environment and intrinsic properties of galaxies on perturbation. We use spatially resolved Hα velocity fields from the SAMI Galaxy Survey to quantify kinematic asymmetry (\\overline{v_asym}) in nearby galaxies and environmental and stellar mass data from the Galaxy And Mass Assembly survey. We find that local environment, measured as distance to nearest neighbour, is inversely correlated with kinematic asymmetry for galaxies with log (M*/M⊙) > 10.0, but there is no significant correlation for galaxies with log (M*/M⊙) < 10.0. Moreover, low-mass galaxies [log (M*/M⊙) < 9.0] have greater kinematic asymmetry at all separations, suggesting a different physical source of asymmetry is important in low-mass galaxies. We propose that secular effects derived from gas fraction and gas mass may be the primary causes of asymmetry in low-mass galaxies. High gas fraction is linked to high σ _m/V (where σm is Hα velocity dispersion and V the rotation velocity), which is strongly correlated with \\overline{v_asym}, and galaxies with log (M*/M⊙) < 9.0 have offset \\overline{σ _m/V} from the rest of the sample. Further, asymmetry as a fraction of dispersion decreases for galaxies with log (M*/M⊙) < 9.0. Gas mass and asymmetry are also inversely correlated in our sample. We propose that low gas masses in dwarf galaxies may lead to asymmetric distribution of gas clouds, leading to increased relative turbulence.

Comparison of spray drying, electroblowing and electrospinning for preparation of Eudragit E and itraconazole solid dispersions.

Science.gov (United States)

Sóti, Péter Lajos; Bocz, Katalin; Pataki, Hajnalka; Eke, Zsuzsanna; Farkas, Attila; Verreck, Geert; Kiss, Éva; Fekete, Pál; Vigh, Tamás; Wagner, István; Nagy, Zsombor K; Marosi, György

2015-10-15

Three solvent based methods: spray drying (SD), electrospinning (ES) and air-assisted electrospinning (electroblowing; EB) were used to prepare solid dispersions of itraconazole and Eudragit E. Samples with the same API/polymer ratios were prepared in order to make the three technologies comparable. The structure and morphology of solid dispersions were identified by scanning electron microscopy and solid phase analytical methods such as, X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and Raman chemical mapping. Moreover, the residual organic solvents of the solid products were determined by static headspace-gas chromatography/mass spectroscopy measurements and the wettability of samples was characterized by contact angle measurement. The pharmaceutical performance of the three dispersion type, evaluated by dissolution tests, proved to be very similar. According to XRPD and DSC analyses, made after the production, all the solid dispersions were free of any API crystal clusters but about 10 wt% drug crystallinity was observed after three months of storage in the case of the SD samples in contrast to the samples produced by ES and EB in which the polymer matrix preserved the API in amorphous state. Copyright © 2015 Elsevier B.V. All rights reserved.

Simple Technique of Exfoliation and Dispersion of Multilayer Graphene from Natural Graphite by Ozone-Assisted Sonication.

Science.gov (United States)

Lin, Zaw; Karthik, Paneer Selvam; Hada, Masaki; Nishikawa, Takeshi; Hayashi, Yasuhiko

2017-05-27

Owing to its unique properties, graphene has attracted tremendous attention in many research fields. There is a great space to develop graphene synthesis techniques by an efficient and environmentally friendly approach. In this paper, we report a facile method to synthesize well-dispersed multilayer graphene (MLG) without using any chemical reagents or organic solvents. This was achieved by the ozone-assisted sonication of the natural graphite in a water medium. The frequency or number of ozone treatments plays an important role for the dispersion in the process. The possible mechanism of graphene exfoliation and the introduction of functional groups have been postulated. The experimental setup is unique for ozone treatment and enables the elimination of ozone off-gas. The heat generated by the dissipation of ultrasonic waves was used as it is, and no additional heat was supplied. The graphene dispersion was stable, and no evidence of aggregation was observed---even after several months. The characterization results show that well-dispersed MLG was successfully synthesized without any significant damage to the overall structure. The graphene obtained by this method has potential applications in composite materials, conductive coatings, energy storage, and electronic devices.

Simple Technique of Exfoliation and Dispersion of Multilayer Graphene from Natural Graphite by Ozone-Assisted Sonication

Directory of Open Access Journals (Sweden)

Zaw Lin

2017-05-01

Full Text Available Owing to its unique properties, graphene has attracted tremendous attention in many research fields. There is a great space to develop graphene synthesis techniques by an efficient and environmentally friendly approach. In this paper, we report a facile method to synthesize well-dispersed multilayer graphene (MLG without using any chemical reagents or organic solvents. This was achieved by the ozone-assisted sonication of the natural graphite in a water medium. The frequency or number of ozone treatments plays an important role for the dispersion in the process. The possible mechanism of graphene exfoliation and the introduction of functional groups have been postulated. The experimental setup is unique for ozone treatment and enables the elimination of ozone off-gas. The heat generated by the dissipation of ultrasonic waves was used as it is, and no additional heat was supplied. The graphene dispersion was stable, and no evidence of aggregation was observed---even after several months. The characterization results show that well-dispersed MLG was successfully synthesized without any significant damage to the overall structure. The graphene obtained by this method has potential applications in composite materials, conductive coatings, energy storage, and electronic devices.

LaCrO{sub 3}-dispersed Cr for metallic interconnect of planar SOFC

Energy Technology Data Exchange (ETDEWEB)

Song, Rak-Hyun; Shin, Dong Ryul [Korea Institute of Energy Research, Taejon (Korea, Republic of); Dokiya, Masayuki [National Institute of Materials and Chemical Research, Ibaraki (Japan)

1996-12-31

In the planar SOFC, the interconnect materials plays two roles as an electrical connection and as a gas separation plate in a cell stack. The interconnect materials must be chemically stable in reducing and oxidizing environments, and have high electronic conductivity, high thermal conductivity, matching thermal expansion with an electrolyte, high mechanical strength, good fabricability, and gas tightness. Lanthanum chromite so far has been mainly used as interconnect materials in planar SOFC. However, the ceramic materials are very weak in mechanical strength and have poor machining property as compared with metal. Also the metallic materials have high electronic conductivity and high thermal conductivity. Recently some researchers have studied metallic interconnects such as Al{sub 2}O{sub 3}/Inconel 600 cermet, Ni-20Cr coated with (LaSr)CoO{sub 3}, and Y{sub 2}O{sub 3-} or La{sub 2}O{sub 3}-dispersed Cr alloy. These alloys have still some problems because Ni-based alloys have high thermal expansion, the added Al{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and La{sub 2}O{sub 3} to metals have no electronic conductivity, and the oxide formed on the surface of Cr alloy has high volatility. To solve these problems, in this study, LaCrO{sub 3}-dispersed Cr for metallic interconnect of planar SOFC was investigated. The LaCrO{sub 3}-dispersed Cr can be one candidate of metallic interconnect because LaCrO{sub 3} possesses electronic conductivity and Cr metal has relatively low thermal expansion. The content of 25 vol.% LaCrO{sub 3} Was selected on the basis of a theoretically calculated thermal expansion. The thermal expansion, electrical and oxidation properties were examined and the results were discussed as related to SOFC requirements.

Spectral phase shift and residual angular dispersion of an accousto-optic programme dispersive filter

International Nuclear Information System (INIS)

Boerzsoenyi, A.; Meroe, M.

2010-01-01

Complete text of publication follows. There is an increasing demand for active and precise dispersion control of ultrashort laser pulses. In chirped pulse amplification (CPA) laser systems, the dispersion of the optical elements of the laser has to be compensated at least to the fourth order to obtain high temporal contrast compressed pulses. Nowadays the most convenient device for active and programmable control of spectral phase and amplitude of broadband laser pulses is the acousto-optic programmable dispersive filter (AOPDF), claimed to be able to adjust the spectral phase up to the fourth order. Although it has been widely used, surprisingly enough there has been only a single, low resolution measurement reported on the accuracy of the induced spectral phase shift of the device. In our paper we report on the first systematic experiment aiming at the precise characterization of an AOPDF device. In the experiment the spectral phase shift of the AOPDF device was measured by spectrally and spatially resolved interferometry, which is especially powerful tool to determine small dispersion values with high accuracy. Besides the spectral phase dispersion, we measured both the propagation direction angular dispersion (PDAD) and the phase front angular dispersion (PhFAD). Although the two quantities are equal for plane waves, there may be noticeable difference for Gaussian pulses. PDAD was determined simply by focusing the beam on the slit of an imaging spectrograph, while PhFAD was measured by the use of an inverted Mach-Zehnder interferometer and an imaging spectrograph. In the measurements, the spectral phase shift and both types of angular dispersion have been recorded upon the systematic change of all the accessible functions of the acousto-optic programmable dispersive filter. The measured values of group delay dispersion (GDD) and third order dispersion (TOD) have been found to agree with the preset values within the error of the measurement (1 fs 2 and 10 fs 3

Screening apatites for (U-Th)/He thermochronometry via continuous ramped heating: He age components and implications for age dispersion

Science.gov (United States)

McDannell, Kalin T.; Zeitler, Peter K.; Janes, Darwin G.; Idleman, Bruce D.; Fayon, Annia K.

2018-02-01

Old slowly-cooled apatites often yield dispersed (U-Th)/He ages for a variety of reasons, some well understood and some not. Analytical protocols like careful grain selection can reduce the impact of this dispersion but add costs in time and resources and too often have proven insufficient. We assess a new analytical protocol that utilizes static-gas measurement during continuous ramped heating (CRH) as a means to rapidly screen apatite samples. In about the time required for a conventional total-gas analysis, this method can discriminate between samples showing expected volume-diffusion behavior and those showing anomalous release patterns inconsistent with their direct use in thermochronologic applications. This method also appears able to discriminate between the radiogenic and extraneous 4He fractions released by a sample, potentially allowing ages to be corrected. Well-behaved examples such as the Durango standard and other apatites with good age reproducibility show the expected smooth, sigmoidal gas-release curves predicted for volume diffusion using typical apatite kinetics, with complete exhaustion by ∼900 °C for linear heating at 20 °C/min. Secondary factors such as U and Th zoning and alpha-loss distribution have a relatively minor impact on such profiles. In contrast, samples having greater age dispersion show significant He release in the form of outgassing spikes and He release deferred to higher temperatures. Screening results for a range of samples permit us to assess the degree to which CRH screening can identify misbehaving grains, give insight into the source of extraneous He, and suggest that in some cases it may be possible to correct ages for the presence of such components.

Gas Content and Kinematics in Clumpy, Turbulent Star-forming Disks

International Nuclear Information System (INIS)

White, Heidi A.; Abraham, Roberto G.; Fisher, David B.; Glazebrook, Karl; Murray, Norman; Bolatto, Alberto D.; Green, Andrew W.; Mentuch Cooper, Erin; Obreschkow, Danail

2017-01-01

We present molecular gas-mass estimates for a sample of 13 local galaxies whose kinematic and star-forming properties closely resemble those observed in z ≈ 1.5 main-sequence galaxies. Plateau de Bure observations of the CO[1-0] emission line and Herschel Space Observatory observations of the dust emission both suggest molecular gas-mass fractions of ∼20%. Moreover, dust emission modeling finds T dust < 30 K, suggesting a cold dust distribution compared to their high infrared luminosity. The gas-mass estimates argue that z ∼ 0.1 DYNAMO galaxies not only share similar kinematic properties with high- z disks, but they are also similarly rich in molecular material. Pairing the gas-mass fractions with existing kinematics reveals a linear relationship between f gas and σ / v c , consistent with predictions from stability theory of a self-gravitating disk. It thus follows that high gas-velocity dispersions are a natural consequence of large gas fractions. We also find that the systems with the lowest t dep (∼0.5 Gyr) have the highest ratios of σ / v c and more pronounced clumps, even at the same high molecular gas fraction.

Stages of Gas-Hydrate Evolution on the Northern Cascadia Margin

Directory of Open Access Journals (Sweden)

the IODP Expedition 311 Scientists

2006-09-01

Full Text Available Natural gas hydrate occurs beneath many continental slopes and in arctic permafrost areas. Recent studies have indicated that the largest deposits of gas hydrate might lie in nearly horizontal layers several hundred meters beneath the seafloor of continental slopes, especially in the large, accretionary sedimentary prisms of subduction zones. Expedition 311 of the Integrated Ocean Drilling Program (IODP investigated the formation of gas hydrate in the accretionary prism of the Cascadia subduction zone (Fig. 1. The primary objectives of Expedition 311 were to test and constraingeological models of gas hydrate formation by upward fluidand methane transport in accretionary prisms. We specifi -cally sought to (a determine the mechanisms that controlthe nature, magnitude, and distribution of the gas hydrate,(b find the pathways of the fluid migration required to formlarge concentrations of gas hydrate, (c examine the effectsof gas hydrate on the physical properties of the host sediment,and (d investigate the microbiology and geochemistryassociated with the occurrence of gas hydrate. Furthermore,we concentrated on the contrast between methane transportby focused fl ow in fault zones and by dispersed pervasiveupward flow at various scales of permeability.

Gas Content and Kinematics in Clumpy, Turbulent Star-forming Disks

Energy Technology Data Exchange (ETDEWEB)

White, Heidi A.; Abraham, Roberto G. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON, M5S 3H8 (Canada); Fisher, David B.; Glazebrook, Karl [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122 (Australia); Murray, Norman [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto ON M5S 3H8 (Canada); Bolatto, Alberto D. [Department of Astronomy and Joint Space Institute, University of Maryland, College Park, MD 20642 (United States); Green, Andrew W. [Australian Astronomical Observatory, P.O. Box 970, North Ryde, NSW 1670 (Australia); Mentuch Cooper, Erin [Astronomy Department, University of Texas at Austin, Austin, TX 78712 (United States); Obreschkow, Danail [International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, M468, Crawley, WA 6009 (Australia)

2017-09-01

We present molecular gas-mass estimates for a sample of 13 local galaxies whose kinematic and star-forming properties closely resemble those observed in z ≈ 1.5 main-sequence galaxies. Plateau de Bure observations of the CO[1-0] emission line and Herschel Space Observatory observations of the dust emission both suggest molecular gas-mass fractions of ∼20%. Moreover, dust emission modeling finds T {sub dust} < 30 K, suggesting a cold dust distribution compared to their high infrared luminosity. The gas-mass estimates argue that z ∼ 0.1 DYNAMO galaxies not only share similar kinematic properties with high- z disks, but they are also similarly rich in molecular material. Pairing the gas-mass fractions with existing kinematics reveals a linear relationship between f {sub gas} and σ / v {sub c}, consistent with predictions from stability theory of a self-gravitating disk. It thus follows that high gas-velocity dispersions are a natural consequence of large gas fractions. We also find that the systems with the lowest t {sub dep} (∼0.5 Gyr) have the highest ratios of σ / v{sub c} and more pronounced clumps, even at the same high molecular gas fraction.

Gas holdup in a reciprocating plate bioreactor: Non-Newtonian - liquid phase

Directory of Open Access Journals (Sweden)

Naseva Olivera S.

2002-01-01

Full Text Available The gas holdup was studied in non-newtonian liquids in a gas-liquid and gas-liquid-solid reciprocating plate bioreactor. Aqueous solutions of carboxy methyl cellulose (CMC; Lucel, Lučane, Yugoslavia of different degrees of polymerization (PP 200 and PP 1000 and concentration (0,5 and 1%, polypropylene spheres (diameter 8.3 mm; fraction of spheres: 3.8 and 6.6% by volume and air were used as the liquid, solid and gas phase. The gas holdup was found to be dependent on the vibration rate, the superficial gas velocity, volume fraction of solid particles and Theological properties of the liquid ohase. Both in the gas-liquid and gas-liquid-solid systems studied, the gas holdup increased with increasing vibration rate and gas flow rate. The gas holdup was higher in three-phase systems than in two-phase ones under otter operating conditions being the same. Generally the gas holdup increased with increasing the volume fraction of solid particles, due to the dispersion action of the solid particles, and decreased with increasing non-Newtonian behaviour (decreasing flow index i.e. with increasing degree of polymerization and solution concentration of CMC applied, as a result of gas bubble coalescence.

Design and development of a dust dispersion chamber to quantify the dispersibility of rock dust.

Science.gov (United States)

Perera, Inoka E; Sapko, Michael J; Harris, Marcia L; Zlochower, Isaac A; Weiss, Eric S

2016-01-01

Dispersible rock dust must be applied to the surfaces of entries in underground coal mines in order to inert the coal dust entrained or made airborne during an explosion and prevent propagating explosions. 30 CFR. 75.2 states that "… [rock dust particles] when wetted and dried will not cohere to form a cake which will not be dispersed into separate particles by a light blast of air …" However, a proper definition or quantification of "light blast of air" is not provided. The National Institute for Occupational Safety and Health (NIOSH) has, consequently, designed a dust dispersion chamber to conduct quantitative laboratory-scale dispersibility experiments as a screening tool for candidate rock dusts. A reproducible pulse of air is injected into the chamber and across a shallow tray of rock dust. The dust dispersed and carried downwind is monitored. The mass loss of the dust tray and the airborne dust measurements determine the relative dispersibility of the dust with respect to a Reference rock dust. This report describes the design and the methodology to evaluate the relative dispersibility of rock dusts with and without anti-caking agents. Further, the results of this study indicate that the dispersibility of rock dusts varies with particle size, type of anti-caking agent used, and with the untapped bulk density. Untreated rock dusts, when wetted and dried forming a cake that was much less dispersible than the reference rock dust used in supporting the 80% total incombustible content rule.

PP and PS seismic response from fractured tight gas reservoirs: a case study

International Nuclear Information System (INIS)

Jianming, Tang; Shaonan, Zhang; Li, Xiang-Yang

2008-01-01

In this paper, we present an example of using PP and PS converted-wave data recorded by digital micro-eletro-mechanical-systems (MEMS) to evaluate a fractured tight gas reservoir from the Xinchang gas field in Sichuan, China. For this, we analyse the variations in converted shear-wave splitting, Vp/Vs ratio and PP and PS impedance, as well as other attributes based on absorption and velocity dispersion. The reservoir formation is tight sandstone, buried at a depth of about 5000 m, and the converted-wave data reveal significant shear-wave splitting over the reservoir formation. We utilize a rotation technique to extract the shear-wave polarization and time delay from the data, and a small-window correlation method to build time-delay spectra that allow the generation of a time-delay section. At the reservoir formation, the shear-wave time delay is measured at 20 ms, about 15% shear-wave anisotropy, correlating with the known gas reservoirs. Furthermore, the splitting anomalies are consistent with the characteristics of other attributes such as Vp/Vs ratio and P- and S-wave acoustic and elastic impedance. The P-wave shows consistent low impedance over the reservoir formation, whilst the S-wave impedance shows relatively high impedance. The calculated gas indicator based on absorption and velocity dispersion yields a high correlation with the gas bearing formations. This confirms the benefit of multicomponent seismic data from digital MEMS sensors

Dispersal kernel estimation: A comparison of empirical and modelled particle dispersion in a coastal marine system

Science.gov (United States)

Hrycik, Janelle M.; Chassé, Joël; Ruddick, Barry R.; Taggart, Christopher T.

2013-11-01

Early life-stage dispersal influences recruitment and is of significance in explaining the distribution and connectivity of marine species. Motivations for quantifying dispersal range from biodiversity conservation to the design of marine reserves and the mitigation of species invasions. Here we compare estimates of real particle dispersion in a coastal marine environment with similar estimates provided by hydrodynamic modelling. We do so by using a system of magnetically attractive particles (MAPs) and a magnetic-collector array that provides measures of Lagrangian dispersion based on the time-integration of MAPs dispersing through the array. MAPs released as a point source in a coastal marine location dispersed through the collector array over a 5-7 d period. A virtual release and observed (real-time) environmental conditions were used in a high-resolution three-dimensional hydrodynamic model to estimate the dispersal of virtual particles (VPs). The number of MAPs captured throughout the collector array and the number of VPs that passed through each corresponding model location were enumerated and compared. Although VP dispersal reflected several aspects of the observed MAP dispersal, the comparisons demonstrated model sensitivity to the small-scale (random-walk) particle diffusivity parameter (Kp). The one-dimensional dispersal kernel for the MAPs had an e-folding scale estimate in the range of 5.19-11.44 km, while those from the model simulations were comparable at 1.89-6.52 km, and also demonstrated sensitivity to Kp. Variations among comparisons are related to the value of Kp used in modelling and are postulated to be related to MAP losses from the water column and (or) shear dispersion acting on the MAPs; a process that is constrained in the model. Our demonstration indicates a promising new way of 1) quantitatively and empirically estimating the dispersal kernel in aquatic systems, and 2) quantitatively assessing and (or) improving regional hydrodynamic

Trace Atmospheric Gas Analyzer (TAGA) Dispersant Data for BP Spil/Deepwater Horizon - August 2010

Data.gov (United States)

U.S. Environmental Protection Agency — The Trace Atmospheric Gas Analyzer (TAGA) buses are self-contained mobile laboratories that conduct instant-result monitoring of air quality at particular locations....

Irradiation behavior of the interaction product of U-Mo fuel particle dispersion in an Al matrix

Energy Technology Data Exchange (ETDEWEB)

Kim, Yeon Soo, E-mail: yskim@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Hofman, G.L. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

2012-06-15

Highlights: Black-Right-Pointing-Pointer We in-pile tested U-Mo dispersion in Al matrix. Black-Right-Pointing-Pointer We observed interaction layer growth between U-Mo and Al and pore formation there. Black-Right-Pointing-Pointer Pores degrades thermal conductivity and structural integrity of the fueled zone. Black-Right-Pointing-Pointer The amorphous behavior of interaction layers is thought to be the main reason for unstable large pore growth. Black-Right-Pointing-Pointer A mechanism for pore formation and possible remedy to prevent it are proposed. - Abstract: Irradiation performance of U-Mo fuel particles dispersed in Al matrix is stable in terms of fuel swelling and is suitable for the conversion of research and test reactors from highly enriched uranium (HEU) to low enriched uranium (LEU). However, tests of the fuel at high temperatures and high burnups revealed obstacles caused by the interaction layers forming between the fuel particle and matrix. In some cases, fission gas filled pores grow and interconnect in the interdiffusion layer resulting in fuel plate failure. Postirradiation observations are made to examine the behavior of the interdiffusion layers. The interdiffusion layers show a fluid-like behavior characteristic of amorphous materials. In the amorphous interdiffusion layers, fission gas diffusivity is high and the material viscosity is low so that the fission gas pores readily form and grow. Based on the observations, a pore formation mechanism is proposed and potential remedies to suppress the pore growth are also introduced.

Atmospheric Dispersion of Various Types of Iodine in UAE in February and August

Energy Technology Data Exchange (ETDEWEB)

Kim, Sungyeop; Beeley, Philip A. [Khalifa Univ. of Science, Abu Dhabi (United Arab Emirates); Kim, Sungyeop; Chang, Soonheung; Lee, Kunjai [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2013-05-15

The distribution ratio of these three types of iodine being released to the atmosphere under accident scenario is still not clearly reported because of its complex kinetics of chemical and physical process in the accidental condition. In this research, the dispersion behaviors of three kinds of iodine in the atmosphere have been considered in the UAE environment in winter and summer situations. Higher ground level concentration on the same downwind distance from the source appears in summer because of lower wind speed than that of winter. More lateral spreading of vertical downwind direction in summer has been confirmed because of less stable air than that of winter. Higher ground level concentrations have been appeared in order of particle type, organic gas type and elemental gas type of I-131 with given assumptions.

Dispersive liquid-liquid microextraction combined with gas chromatography-electron capture detection for the determination of polychlorinated biphenyls in soils

International Nuclear Information System (INIS)

Hu Jia; Fu Lingyan; Zhao Xinna; Liu Xiujuan; Wang Huili; Wang Xuedong; Dai Liyan

2009-01-01

In this article, dispersive liquid-liquid microextraction (DLLME) and gas chromatography-electron capture detection (GC-ECD) were presented for the extraction and determination of five polychlorinated biphenyls (PCBs) in soil samples. Acetone was used as extraction solvent for the extraction of PCBs from soil samples. In DLLME, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to chlorobenzene when the extraction process began. The main advantages of this method are quick speed, high enrichment factor, high recovery and good repeatability. Under the optimum conditions, the method yields a linear calibration curve in the concentration range from 2 to 2000 μg kg -1 for PCB 52, and 0.4 to 400 μg kg -1 for other target analytes. Coefficients of correlation (r 2 ) ranged from 0.9993 to 0.9999. The repeatability was tested by spiking soil samples at a concentration level of 10 μg kg -1 for PCBs. The relative standard deviations (RSDs, n = 11) varied between 2.2% and 6.4%. The limits of detection (LODs), based on signal-to-noise (S/N) of 3, were between 0.20 and 0.50 μg kg -1 . The relative recoveries of the five PCBs from soil S1, S2 and S3 at spiking levels of 10, 20 and 50 μg kg -1 were in the range of 88.70-103.8%, 82.50-106.3% and 82.30-113.6%, respectively. Therefore, DLLME combined with GC-ECD can be successfully applied for the determination of trace PCB residues in real soil samples.

Laser control of natural disperse systems

Science.gov (United States)

Vlasova, Olga L.; Bezrukova, Alexandra G.

2003-10-01

Different water disperse systems were studied by integral (spectroturbidemetry) and differential light scattering method with a laser as a source of light. The investigation done concerns the state of kaolin dispersions at storage and under dilution as an example of mineral dispersion systems such as natural water. The role of some light scattering parameters for an optical analysis of water dispersions, like the dispersion of erythrocytes and bacterial cells -Escherichia coli is discussed. The results obtained can help to elaborate the methods for on-line optical control fo natural disperse systems (water, air) with mineral and biological particles.

Graphene oxide for gas detection under standard humidity conditions

International Nuclear Information System (INIS)

Donarelli, Maurizio; Prezioso, Stefano; Perrozzi, Francesco; Ottaviano, Luca; Giancaterini, Luca; Cantalini, Carlo; Treossi, Emanuele; Palermo, Vincenzo; Santucci, Sandro

2015-01-01

Graphene oxide (GO) synthesis is the easiest way to functionalize graphene, preserving the high graphene surface to volume ratio. Therefore, GO is a promising candidate for gas sensing applications. In this paper, an easy-to-fabricate and high sensitivity GO-based gas sensor is proposed. The device is fabricated by drop-casting a solution of GO flakes dispersed in water on a prepatterned Si 3 N 4 substrate with 30 μm spaced Pt electrodes. The sensing material has been studied using scanning electron microscopy and x-ray photoelectron spectroscopy. The large lateral dimensions of the flakes (tens of microns) allow single GO flake to bridge adjacent electrodes. The high quality of the synthesized flakes results in the gas sensor high sensitivity to and low detection limit (20 ppb) of NO 2 . The gas sensor response to NO 2 has been studied in various relative humidity environments and it is demonstrated not to be affected by the presence of water vapor. Finally, the gas sensor responses to acetone, toluene, ethanol, and ammonia are reported. (paper)

Activity and selectivity regulation of synthesis gas reaction over supported ruthenium catalysts

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, K; Nobusawa, T; Fukushima, T; Tominaga, H

1985-01-01

The catalytic activities of supported ruthenium for synthesis-gas conversion to hydrocarbons was found to be in the following order: TiOS > Nb2O3 > ZrO2 > SiO2 > Ta2O5 > Al2O3 > V2O5 > MoO3 > WO3 > MnO2 > ZnO. Turnover frequencies of the supported ruthenium increased with decrease in dispersion of the metal particles for every carrier material. Even the activities per unit weight of metals were higher for low-dispersion ruthenium of Al2O3, TiO2, and ZrO2. The chain-growth probability of a hydrocarbon product, which is characterized by the Schulz-Flory distribution, increased markedly with decrease in the metal dispersion irrespective of the carrier material. The catalytic activity of ruthenium particles with a dispersed ruthenium increased almost linearly with an increase in reaction pressure (up to at least 2.0 MPa). 23 references, 10 figures, 3 tables.

Effect of SnO2/SiO2 nano particle dispersant on the performance characteristic of complex multi-doped composite coating produced through electrodeposition on oil and gas storage tap

Science.gov (United States)

Anawe, P. A. L.; Fayomi, O. S. I.; Ayoola, A. A.; Popoola, A. P. I.

2018-06-01

The effect of SnO2/SiO2 nano particle dispersant on the performance characteristic of complex zinc multi-doped composite coating produced through electrodeposition is studied. The degradation behaviour in term of wear and chemical corrosion activities were considered as a major factor in service. The wear mass loss was carried out with the help of reciprocating tester. The electrochemical corrosion characteristics were investigated using linear polarization technique in 3.5% simulated sodium chloride media. The outcome of the analysis shows that the developed coating was seen to provide a sound anti wear characteristics in its multidoped state. The corrosion resistance properties were observed to be massive compared to the binary based sample. It is expected that this characteristic will impact on the performance life span of storage tap in oil and gas.

Contributions of gas flaring to a global air pollution hotspot : spatial and temporal variations, impacts and alleviation

OpenAIRE

Anejionu, Obinna; Whyatt, Duncan; Blackburn, George Alan; Price, Catheryn

2015-01-01

Studies of environmental impacts of gas flaring in the Niger Delta are hindered by limited access to official flaring emissions records and a paucity of reliable ambient monitoring data. This study uses a combination of geospatial technologies and dispersion modelling techniques to evaluate air pollution impacts of gas flaring on human health and natural ecosystems in the region. Results indicate that gas flaring is a major contributor to air pollution across the region, with concentrations e...

Fickian dispersion is anomalous

Science.gov (United States)

Cushman, John H.; O'Malley, Dan

2015-12-01

The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

SILP catalysis in gas-phase hydroformylation and carbonylation

Energy Technology Data Exchange (ETDEWEB)

Riisager, A.; Fehrmann, R. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Chemistry; Haumann, M.; Wasserscheid, P. [Univ. Erlangen-Nuernberg (Germany). Lehrstuhl fuer Chemische Reaktionstechnik

2006-07-01

Supported ionic liquid phase (SILP) catalysts are new materials consisting of an ionic liquid-metal catalyst solution highly dispersed on a porous support. The use of a non-volatile, ionic liquid catalyst phase in SILP catalysts results in a stable heterogeneous-type material with selectivity and efficiency like homogeneous catalysts. The silica-supported SILP Rh-bisphosphine hydroformylation catalyst exhibited good activities and excellent selectivities in gas phase hydroformylation with stability exceeding 700 hours time-on-stream. Spectroscopic and kinetic data confirmed the homogeneous nature of the catalyst. In the Rh- SILP catalysed carbonylation of methanol the formation of undesired by-products could be suppressed by variation of residence time and gas pressure. (orig.)

Composite Chern-Simons gauge boson in anyon gas

International Nuclear Information System (INIS)

Nguyen Van Hieu; Nguyen Hung Son.

1990-08-01

It was shown that in a free anyon gas there exists a composite vector gauge field with the effective action containing a Chern-Simons term. The momentum dependence of the energy of the composite boson was found. The mixing between Chern-Simons boson and photon gives rise to the appearance of new quasiparticles - Chern-Simons polaritons. The dispersion equations of Chern-Simons polaritons were derived. (author). 14 refs

Does an ant-dispersed plant, Viola reichenbachiana, suffer from reduced seed dispersal under inundation disturbances?

NARCIS (Netherlands)

Prinzing, A.; Dauber, J.; Hammer, E.; Hammouti, N.; Bohning-Gaese, K.

2008-01-01

Many plant species use ants as seed dispersers. This dispersal mode is considered to be susceptible to disturbances, but the effect of natural, small-scale disturbances is still unknown. We investigated how small-scale disturbances due to inundation affect seed dispersal in Viola reichenbachiana, a

Clock synchronization and dispersion

International Nuclear Information System (INIS)

Giovannetti, Vittorio; Lloyd, Seth; Maccone, Lorenzo; Wong, Franco N C

2002-01-01

We present a method to defeat effects of dispersion of timing signals when synchronizing clocks. It is based on the recently proposed 'conveyor belt synchronization' scheme and on the quantum dispersion cancellation effect

Nozzle for electric dispersion reactor

Science.gov (United States)

Sisson, W.G.; Basaran, O.A.; Harris, M.T.

1995-11-07

A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode. 4 figs.

Gas and aerosol radionuclide transfers in complex environments: experimental studies of atmospheric dispersion and interfaces exchanges

International Nuclear Information System (INIS)

Maro, Denis

2011-01-01

In situations of chronic or accidental releases, the atmosphere is the main pathway of radioactive releases from nuclear facilities to the environment and, consequently, to humans. It is therefore necessary to have sufficient information on this pathway to accurately assess the radiological impact on man and his environment. Institute for Radioprotection and Nuclear Safety develops its own tools of dispersion and atmospheric transfer for its expertise, under normal operation conditions of a facility, but especially in crisis or post-accident. These tools must have a national and international recognition in particular through scientific validation against benchmark experiments performed internationally, nationally or within the IRSN. The Radioecology Laboratory of Cherbourg-Octeville provides, and will increasingly make, a significant contribution to the scientific influence of the Institute in this field. The work presented in this report has contributed to the development or improvement of experimental techniques in the fields of atmospheric dispersion of radionuclides and transfer at interfaces, in complex environments (complex topography, urban area). These experimental techniques, applied during field campaigns, have allowed to acquire new data in order to get a better understanding of radionuclide transfers in the form of gases and aerosols. (author)

Analytical study of solids-gas two phase flow

International Nuclear Information System (INIS)

Hosaka, Minoru

1977-01-01

Fundamental studies were made on the hydrodynamics of solids-gas two-phase suspension flow, in which very small solid particles are mixed in a gas flow to enhance the heat transfer characteristics of gas cooled high temperature reactors. Especially, the pressure drop due to friction and the density distribution of solid particles are theoretically analyzed. The friction pressure drop of two-phase flow was analyzed based on the analytical result of the single-phase friction pressure drop. The calculated values of solid/gas friction factor as a function of solid/gas mass loading are compared with experimental results. Comparisons are made for Various combinations of Reynolds number and particle size. As for the particle density distribution, some factors affecting the non-uniformity of distribution were considered. The minimum of energy dispersion was obtained with the variational principle. The suspension density of particles was obtained as a function of relative distance from wall and was compared with experimental results. It is concluded that the distribution is much affected by the particle size and that the smaller particles are apt to gather near the wall. (Aoki, K.)

Measurement of phase interaction in dispersed gas-particle two-phase flow by phase-doppler anemometry

OpenAIRE

Mergheni Ali Mohamed; Ben Ticha Hmaied; Sautet Jen-Charles; Godard Gille; Ben Nasrallah Sassi

2008-01-01

For simultaneous measurement of size and velocity distributions of continuous and dispersed phases in a two-phase flow a technique phase-Doppler anemometry was used. Spherical glass particles with a particle diameter range from 102 up to 212 µm were used. In this two-phase flow an experimental results are presented which indicate a significant influence of the solid particles on the flow characteristics. The height of influence of these effects depends on the local position in the jet. Near t...

Electrodynamic modeling applied to micro-strip gas chambers

International Nuclear Information System (INIS)

Fang, R.

1998-01-01

Gas gain variations as functions of time, counting rate and substrate resistivity have been observed with Micro-Strip Gas Chambers (MSGC). Such a chamber is here treated as a system of 2 dielectrics, gas and substrate, with finite resistivities. Electric charging between their interface results in variations of the electric field and the gas gain. The electrodynamic equations (including time dependence) for such a system are proposed. A Rule of Charge Accumulation (RCA) is then derived which allows to determine the quantity and sign of charges accumulated on the surface at equilibrium. In order to apply the equations and the rule to MSGCs, a model of gas conductance induced by ionizing radiation is proposed, and a differential equation and some formulae are derived to calculate the rms dispersion and the spatial distribution of electrons (ions) in inhomogeneous electric fields. RCA coupled with a precise simulation of the electric fields gives the first quantitative explanation of gas gain variations of MSGCs. Finally an electrodynamic simulation program is made to reproduce the dynamic process of gain variation due to surface charging with an uncertainty of at most 15% relative to experimental data. As a consequence, the methods for stabilizing operation of MSGCs are proposed. (author)

Numerical modeling of disperse material evaporation in axisymmetric thermal plasma reactor

Directory of Open Access Journals (Sweden)

Stefanović Predrag Lj.

2003-01-01

Full Text Available A numerical 3D Euler-Lagrangian stochastic-deterministic (LSD model of two-phase flow laden with solid particles was developed. The model includes the relevant physical effects, namely phase interaction, panicle dispersion by turbulence, lift forces, particle-particle collisions, particle-wall collisions, heat and mass transfer between phases, melting and evaporation of particles, vapour diffusion in the gas flow. It was applied to simulate the processes in thermal plasma reactors, designed for the production of the ceramic powders. Paper presents results of extensive numerical simulation provided (a to determine critical mechanism of interphase heat and mass transfer in plasma flows, (b to show relative influence of some plasma reactor parameters on solid precursor evaporation efficiency: 1 - inlet plasma temperature, 2 - inlet plasma velocity, 3 - particle initial diameter, 4 - particle injection angle a, and 5 - reactor wall temperature, (c to analyze the possibilities for high evaporation efficiency of different starting solid precursors (Si, Al, Ti, and B2O3 powder, and (d to compare different plasma reactor configurations in conjunction with disperse material evaporation efficiency.

Statistical Thermodynamics of Disperse Systems

DEFF Research Database (Denmark)

Shapiro, Alexander

1996-01-01

Principles of statistical physics are applied for the description of thermodynamic equilibrium in disperse systems. The cells of disperse systems are shown to possess a number of non-standard thermodynamic parameters. A random distribution of these parameters in the system is determined....... On the basis of this distribution, it is established that the disperse system has an additional degree of freedom called the macro-entropy. A large set of bounded ideal disperse systems allows exact evaluation of thermodynamic characteristics. The theory developed is applied to the description of equilibrium...

Geometry of physical dispersion relations

International Nuclear Information System (INIS)

Raetzel, Dennis; Rivera, Sergio; Schuller, Frederic P.

2011-01-01

To serve as a dispersion relation, a cotangent bundle function must satisfy three simple algebraic properties. These conditions are derived from the inescapable physical requirements that local matter field dynamics must be predictive and allow for an observer-independent notion of positive energy. Possible modifications of the standard relativistic dispersion relation are thereby severely restricted. For instance, the dispersion relations associated with popular deformations of Maxwell theory by Gambini-Pullin or Myers-Pospelov are not admissible. Dispersion relations passing the simple algebraic checks derived here correspond to physically admissible Finslerian refinements of Lorentzian geometry.

Quantifying greenhouse gas emissions from waste treatment facilities

DEFF Research Database (Denmark)

Mønster, Jacob

to be in-stalled in any vehicle and thereby enabling measurements wherever there were roads. The validation of the measurement method was done by releasing a controlled amount of methane and quantifying the emission using the release of tracer gas. The validation test showed that even in areas with large...... treatment plants. The PhD study reviewed and evaluated previously used methane measurement methods and found the tracer dispersion method promising. The method uses release of tracer gas and the use of mobile equipment with high analytical sensitivity, to measure the downwind plumes of methane and tracer...... ranged from 10 to 92 kg per hour and was found to change in even short timescales of a few hours. The periods with large emissions correlated with a drop in methane utilization, indicating that emissions came from the digesters tanks or gas storage/use. The measurements indicated that the main emissions...

Influence of Fuel-Matrix Interaction on the Deformation of U-Mo Dispersion Fuel

Energy Technology Data Exchange (ETDEWEB)

Ryu, Ho Jin [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Yeon Soo [Argonne National Laboratory, Chicago (United States)

2014-05-15

In order to predict the fuel plate failure leading to breakaway swelling in the meat, an understanding of the effects of the fuel-matrix interaction behavior on the deformation of fuel meat is necessary. However, the effects of IL formation on the development of breakaway swelling have not been studied thoroughly. A mechanism that explains large pore growth that leads to breakaway swelling has not been included in the existing fuel performance models. In this study, the effect of the fuel-matrix interaction on large interfacial porosity development at the IL-Al interface is analyzed using both mechanistic correlations and observations from the post-irradiation examination results of U-Mo Dispersion fuels. The effects of fuel-matrix interaction on the fuel performance of U-Mo/Al Dispersion fuel were investigated. Fuel-matrix interaction bears the causes for breakaway swelling that can lead to a fuel failure under a high-power irradiation condition. Fission gas atoms are released from U-Mo particles to the interaction layer via diffusion and recoil. The fission gases released from the U-Mo and produced in the ILs are further released to the IL-Al interface by diffusion in the IL and recoil. Large pore formation at the IL-Al interface is attributed to the active diffusion of fission gas atoms in the ILs and coalescence between the small bubbles there. A model calculation showed that IL growth increases the probability of forming a breakaway swelling condition. ILs are connected to each other and the Al matrix decreases as ILs grow. When more ILs are interconnected, breakaway swelling can occur when the effective stress from the fission gas pressure in the IL-Al interfacial pore becomes larger than the yield strength of the Al matrix.

Development of a tritium dispersion code

International Nuclear Information System (INIS)

Bell, R.P.; Davis, M.W.; Joseph, S.; Wong, K.Y.

1985-01-01

This paper describes the development and verification of a computer code designed to calculate the radiation dose to man following acute or chronic atmospheric releases of tritium gas and oxide from a point source. The Ontario Hydro Tritium Dispersion Code calculates tritium concentrations in air, soil, and vegetation and doses to man resulting from inhalation/immersion and ingestion of food, milk meat and water. The deposition of HT to soil, conversion of HT to HTO by soil enzymes and resuspension of HTO to air have been incorporated into the terrestrial compartment model and are unique features of the code. Sensitivity analysis has identified the HT deposition velocity and the equivalent water depth of the vegetation compartment as two parameters which have a strong influence on dose calculations. Tritium concentrations in vegetation and soil calculated by the code were in reasonable agreement with experimental results. The radiological significance of including the mechanisms of HT to HTO conversion and resuspension of HTO to air is illustrated

Experimental and theoretical investigation of droplet dispersion in venturi scrubbers with axial liquid injection

Energy Technology Data Exchange (ETDEWEB)

Mokhtarian, N.; Talaei, A.; Karimikhosroabadi, M. [Islamic Azad University, Shahreza Branch, Shahreza (Iran); Sadeghi, F. [Chemical Engineering Department, University of Isfahan, Isfahan (Iran); Talaie, M.R.

2009-05-15

Droplet dispersion in a Venturi scrubber with axial liquid injection was investigated both experimentally and theoretically. The main objective of this study was to develop a mathematical model to predict droplet dispersion in a Venturi scrubber with axial liquid injection. The effects of the Peclet number and droplet size distribution on droplet dispersion were studied using the developed model. Sampling of the droplets was carried out, isokinetically, in 16 positions at the end of the throat section. The experimental data were used to find the parameters of the developed model, such as the Peclet number. From the results of this study, it was found that the Peclet number was not constant across the cross section of the scrubber channel. In order to achieve a better agreement between the results of the model and the experimental data, it was required to consider Peclet number variations across the Venturi channel. It was also revealed that the parameter representing the width of the Rosin-Rammler distribution of droplet size could not be considered constant and it was influenced significantly by the operating parameters such as liquid flow rate and gas velocity. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

3D analysis of the gas dynamic loads in the KKB containment resulting from combustion of radiolysis gas

International Nuclear Information System (INIS)

Kotchourko, A.; Breitung, W.; Dorofeev, S.; Ohlmeyer, H.

2003-01-01

The radiolysis gas explosion in the KKB power plant was recalculated in 3D simulations as followed: The total energy released was limited as far as possible. - Pressure generation and dispersion across the containment was calculated for three different initial energies. - Loads in the near field were simulated assuming the most probable total energy (about 14 MJ) and using three different models of the explosion process. The calculation with direct simulation of detonation inside the tube provided realistic results, according to the authors. - Transient local pressure and temperature loads were recorded in specified local points and evaluated in further damage analyses. The results showed that modern 3D flow and combustion calculations provide valuable information on pressure and temperature loads resulting from radiolysis gas reactions in big complex safety containments. (orig.) [de

Estimating Predictive Variance for Statistical Gas Distribution Modelling

International Nuclear Information System (INIS)

Lilienthal, Achim J.; Asadi, Sahar; Reggente, Matteo

2009-01-01

Recent publications in statistical gas distribution modelling have proposed algorithms that model mean and variance of a distribution. This paper argues that estimating the predictive concentration variance entails not only a gradual improvement but is rather a significant step to advance the field. This is, first, since the models much better fit the particular structure of gas distributions, which exhibit strong fluctuations with considerable spatial variations as a result of the intermittent character of gas dispersal. Second, because estimating the predictive variance allows to evaluate the model quality in terms of the data likelihood. This offers a solution to the problem of ground truth evaluation, which has always been a critical issue for gas distribution modelling. It also enables solid comparisons of different modelling approaches, and provides the means to learn meta parameters of the model, to determine when the model should be updated or re-initialised, or to suggest new measurement locations based on the current model. We also point out directions of related ongoing or potential future research work.

Determination of dispersity of crushed granite

International Nuclear Information System (INIS)

Liu Dejun; Fan Xianhua; Zhang Yingjie; Yao Jun; Zhou Duo; Wang Yong

2004-01-01

The experimental crushed granite column breakthrough curves, using 99 Tc as spike tracer and 3 H as invariant tracer, are analyzed by different linear regression techniques. Dispersity of crushed granite and retardation factor of 99 TcO 4 - on the crushed granite are determined simultaneously by one linear regression technique. Dispersity of crushed granite is also obtained with 3 H as invariant tracer by the other linear regression technique. The dispersities found by spike source and invariant source methods are compared. The experimental results show that the dispersity found by spike source method is close to that found by invariant source method. It indicates that dispersity is only the characteristic of dispersion medium

Determination of dispersity of crushed granite

International Nuclear Information System (INIS)

Liu, D.J.; Fan, X.H.

2005-01-01

Experimental crushed granite column breakthrough curves, using 99 Tc as spike tracer and 3 H as invariant tracer, were analyzed by different linear regression techniques. Dispersity of crushed granite and the retardation factor of 99 TcO 4 - on the crushed granite were determined simultaneously by one linear regression. Dispersity of crushed granite was also obtained with 3 H as invariant tracer by the other linear regression. The dispersities found by spike source and invariant source methods are compared. Experimental results show that the dispersity found by the spike source method is close to that found by the invariant source method. This indicates that dispersity is only a characteristic of the dispersion medium. (author)

Dispersive shock waves in systems with nonlocal dispersion of Benjamin-Ono type

Science.gov (United States)

El, G. A.; Nguyen, L. T. K.; Smyth, N. F.

2018-04-01

We develop a general approach to the description of dispersive shock waves (DSWs) for a class of nonlinear wave equations with a nonlocal Benjamin-Ono type dispersion term involving the Hilbert transform. Integrability of the governing equation is not a pre-requisite for the application of this method which represents a modification of the DSW fitting method previously developed for dispersive-hydrodynamic systems of Korteweg-de Vries (KdV) type (i.e. reducible to the KdV equation in the weakly nonlinear, long wave, unidirectional approximation). The developed method is applied to the Calogero-Sutherland dispersive hydrodynamics for which the classification of all solution types arising from the Riemann step problem is constructed and the key physical parameters (DSW edge speeds, lead soliton amplitude, intermediate shelf level) of all but one solution type are obtained in terms of the initial step data. The analytical results are shown to be in excellent agreement with results of direct numerical simulations.

HGSYSTEMUF6, Simulating Dispersion Due to Atmospheric Release of Uranium Hexafluoride (UF6)

International Nuclear Information System (INIS)

Hanna, G; Chang, J.C.; Zhang, J.X.; Bloom, S.G.; Goode, W.D. Jr; Lombardi, D.A.; Yambert, M.W.

2001-01-01

, for a given time step, the equations governing the processes of dispersion, chemical reaction, and thermodynamics can be solved sequentially and independently. Here, a Runge-Kutta solver is employed to solve the equations governing dispersion, a simple, first-order forward finite difference scheme is used to solve the rate equations for the consumption and production of reactants, while the proprietary nonlinear algebraic equation solver NAESOL, developed by Shell Research LTD. is used to solve equations governing thermodynamic balances of molar fraction, enthalpy and molar flow rate of HF. Conversely, for simulating downwind dispersion of a passive, ideal gas, the WAKE component employs equations based on advanced empirical formulations of wind tunnel data in conjunction with the standard gaussian plume model formation. 3 - Restriction on the complexity of the problem: HGSYSTEMUF6 is designed for a single user on a single personal computer. Array dimensions have been initially set to reflect realistic, limiting values. By modification of these limits the user may create executable versions of model files that are limited only by the hardware configuration of their machine. HGSYSTEMUF6 is designed specifically for the simulation of atmospheric releases of Uranium Hexafluoride and its reaction products. For other simulations which involve the dispersion of vapour from gas, liquid or two-phase releases including multi-component mixtures, HGSYSTEM, is available at no charge from the official shell Research LTD HGSYSTEM Web site: http://www.users.virtual-chester.com/hgsystem or email HGSystem at OPC.shell.com

The role of ventilation in controlling the dispersion of radon gas from a cellar in a domestic house

International Nuclear Information System (INIS)

Ward, I.C.; Wang, F.; Sharples, S.; Pitts, A.C.

1994-01-01

In certain parts of the United Kingdom where radon gas seeps from the ground into the basement of domestic housing, normal methods of removing this gas by using under floor extract ventilation is not appropriate. In this situation the radon gas enters the basement through the side walls of the cellar and hence into the house. Using mechanical ventilation to either pressurise or de-pressurise the cellar may be an appropriate solution to this problem, however, before installing such a system in a house a ventilation strategy must be established. This paper sets out a ventilation strategy for minimising the ingress of radon into a domestic house, which has been established by simulating the air movement within a domestic house using Breeze Version 6 for a range of environmental conditions. The results of this analysis show that in winter when the emission of radon gas is most strong de-pressurisation of the basement can improve the ingress of the gas to the rest of the house. (author)

Optimizing optical pre-dispersion using transmit DSP for mitigation of Kerr nonlinearities in dispersion managed cables

Science.gov (United States)

Hopkins, James; Gaudette, Jamie; Mehta, Priyanth

2013-10-01

With the advent of digital signal processing (DSP) in optical transmitters and receivers, the ability to finely tune the ratio of pre and post dispersion compensation can be exploited to best mitigate the nonlinear penalties caused by the Kerr effect. A portion of the nonlinear penalty in optical communication channels has been explained by an increase in peak to average power ratio (PAPR) inherent in highly dispersed signals. The standard approach for minimizing these impairments applies 50% pre dispersion compensation and 50% post dispersion compensation, thereby decreasing average PAPR along the length of the cable, as compared with either 100% pre or post dispersion compensation. In this paper we demonstrate that simply considering the net accumulated dispersion, and applying 50/50 pre/post dispersion is not necessarily the best way to minimize PAPR and subsequent Kerr nonlinearities. Instead, we consider the cumulative dispersion along the entire length of the cable, and, taking into account this additional information, derive an analytic formula for the minimization of PAPR. Alignment with simulation and experimental measurements is presented using a commercially available 100Gb/s dual-polarization binary phase-shift-keying (DP-BPSK) coherent modem, with transmitter and receiver DSP. Measurements are provided from two different 5000km dispersion managed Submarine test-beds, as well as a 3800km terrestrial test-bed with a mixture of SMF-28 and TWRS optical fiber. This method is shown to deviate significantly from the conventional 50/50 method described above, in dispersion managed communications systems, and more closely aligns with results obtained from simulation and data collected from laboratory test-beds.

Synthesis of superparamagnetic nanoparticles dispersed in spherically shaped carbon nanoballs

Energy Technology Data Exchange (ETDEWEB)

Ibrahim, E.M.M., E-mail: e.ibrahim@science.sohag.edu.eg; Hampel, Silke; Thomas, Juergen; Haase, Diana; Wolter, A. U. B.; Khavrus, Vyacheslav O.; Taeschner, Christine; Leonhardt, Albrecht; Buechner, Bernd [Leibniz Institute of Solid State and Material Research (Germany)

2012-09-15

In this work, carbon nanoballs in spherical shape with diameter 70 {+-} 2 nm containing well-dispersed superparamagnetic magnetite/maghemite Fe{sub 3}O{sub 4}/{gamma}-Fe{sub 2}O{sub 3} nanoparticles of 5-10 nm in size were synthesised by a facile route using the radio frequency (rf) plasma in order to assist the pyrolysis of ferrocene. Ferrocene was placed in an inductively coupled rf plasma field without additional thermal heating to activate simultaneous sublimation and pre-pyrolysis processes. During this plasma activation, the resultant derivatives were carried by an argon gas stream into the hot zone of a resistance furnace (600 Degree-Sign C) for complete thermal decomposition. The deposition of the nanoballs could be observed in the hot zone of the furnace at a temperature of 600 Degree-Sign C. The synthesised nanoballs are highly dispersible in solvents that make them particularly suitable for different applications. Their morphology, composition and structure were characterized by high-resolution scanning and transmission electron microscopy, including selected area electron diffraction, electron energy loss spectroscopy and X-ray diffraction. Magnetic measurements demonstrated that the nanoballs possess superparamagnetic characteristics.

Increases of QT dispersion, corrected QT dispersion and QT interval in young healthy individuals during Ramadan fasting

Directory of Open Access Journals (Sweden)

Moradmand S

2003-06-01

Full Text Available Ramadan fasting is one of the most important religious duties of Muslims, that its effect on the heart has not been determined yet. Our objective was to evaluate the effect of Ramadan fasting on ventricular repolarization as assessed by QT interval, corrected QT interval, QT dispersion or corrected QT dispersion. Sixthy healthy subjects aged 20 to 35 years were dispersion included in this study. QT interval, corrected QT interval (QTc QT dispersion QTc dispersion, RR interval and QRS axis were measured in 12-lead surface electrocardiogram, once during fasting (10 to 11.5 hours of absolute fasting from food and liquid and another time, 15 tp 60 minutes after eating food at sunset, All of the subjects had been fasting 11 to 12 hours each day at least for 25 days during Ramadan. The study was performed at Amir Alam hospital in the year 2000. Maximal QT interval, mean QT interval and RR-interval, were longer during fasting (P<0.05, and both QT dispersion and QTc dispersion were increased (P<0.05. (QT dispersion: mean ±SD= 57.2±20.1 ms during fasting Vs 41.6±15.1 ms after meal, QTc dispersion=75.4±24.6 ms during fasting Vs 64.1±22.8 ms after meal. But mean QTc interval maximal QTc interval and QRS axis showed no significant difference. Prolongation of QT interval and RR interval during fasting, instead of no significant changes in corrected QT interval may primarily suggest that prolongation of RR-interval causes QTc interval not to have significant difference. But increases of QT dispersion and corrected QT dispersion (QTc dispersion during fasting -that are more reliable indicators of ventricular repolarization-support the idea that ventricular repolarization may be changed during Ramadan fasting. QT dispersion in cardiac patients is showed to increase from normal values of 30-40 to 64-138 ms, but in our study their increases did not reach critical value.

Sensitivity of numerical dispersion modeling to explosive source parameters

International Nuclear Information System (INIS)

Baskett, R.L.; Cederwall, R.T.

1991-01-01

The calculation of downwind concentrations from non-traditional sources, such as explosions, provides unique challenges to dispersion models. The US Department of Energy has assigned the Atmospheric Release Advisory Capability (ARAC) at the Lawrence Livermore National Laboratory (LLNL) the task of estimating the impact of accidental radiological releases to the atmosphere anywhere in the world. Our experience includes responses to over 25 incidents in the past 16 years, and about 150 exercises a year. Examples of responses to explosive accidents include the 1980 Titan 2 missile fuel explosion near Damascus, Arkansas and the hydrogen gas explosion in the 1986 Chernobyl nuclear power plant accident. Based on judgment and experience, we frequently estimate the source geometry and the amount of toxic material aerosolized as well as its particle size distribution. To expedite our real-time response, we developed some automated algorithms and default assumptions about several potential sources. It is useful to know how well these algorithms perform against real-world measurements and how sensitive our dispersion model is to the potential range of input values. In this paper we present the algorithms we use to simulate explosive events, compare these methods with limited field data measurements, and analyze their sensitivity to input parameters. 14 refs., 7 figs., 2 tabs

Boltorn-Modified Poly(2,6-dimethyl-1,4,phenylene oxide) Gas Separation Membranes

NARCIS (Netherlands)

Sterescu, D.M.; Stamatialis, Dimitrios; Mendes, Eduardo; Kruse, Jan; Rätzke, Klaus; Faupel, Franz; Wessling, Matthias

2007-01-01

This paper describes the preparation, characterization and the permeation properties of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) dense polymer films containing aliphatic hyperbranched polyesters, Boltorn (H20, H30, and H40). The Boltorn are dispersed in PPO at various concentrations. The gas

Dispersion Distance and the Matter Distribution of the Universe in Dispersion Space.

Science.gov (United States)

Masui, Kiyoshi Wesley; Sigurdson, Kris

2015-09-18

We propose that "standard pings," brief broadband radio impulses, can be used to study the three-dimensional clustering of matter in the Universe even in the absence of redshift information. The dispersion of radio waves as they travel through the intervening plasma can, like redshift, be used as a cosmological distance measure. Because of inhomogeneities in the electron density along the line of sight, dispersion is an imperfect proxy for radial distance and we show that this leads to calculable dispersion-space distortions in the apparent clustering of sources. Fast radio bursts (FRBs) are a new class of radio transients that are the prototypical standard ping and, due to their high observed dispersion, have been interpreted as originating at cosmological distances. The rate of fast radio bursts has been estimated to be several thousand over the whole sky per day and, if cosmological, the sources of these events should trace the large-scale structure of the Universe. We calculate the dispersion-space power spectra for a simple model where electrons and FRBs are biased tracers of the large-scale structure of the Universe, and we show that the clustering signal could be measured using as few as 10 000 events. Such a survey is in line with what may be achieved with upcoming wide-field radio telescopes.

Improved gas distributor for coating HTGR fuel particles

International Nuclear Information System (INIS)

Lackey, W.J.; Stinton, D.P.; Sease, J.D.

1977-01-01

The important criteria to be considered in design of the gas distributor are: (1) The distributor should ideally spread or disperse the gas over the full area of the coating chamber to maximize the particle gas contact area and thereby increase both particle circulation and the percentage of the input gas that ends up as coating. (2) The gas should not heat up during its passage through the distributor. Otherwise the gas would partially decompose prematurely, causing excessive coating deposition within or on the distributor. (3) The distributor should be designed to minimize accidental drainage of particles from the furnace and blowover of particles into the effluent system. (4) The distributor should be capable of depositing both carbon and SiC coatings of high quality as regards to density, preferred orientation, permeability, defective fraction, and other product attributes. (5) The distributor should be amenable to use with large particle charges and short turnaround times and be simple, inexpensive, and reliable. We have devised a simple distributor that incorporates the five criteria listed above. The new design is termed a blind-hole frit. All the gas passes through the thinned blind-hole regions, and thus the gas velocity is considerably higher than for a flat frit of uniform thickness. Because of its high velocity, the gas does not have time to reach a high enough temperature to cause deposition within the frit. Also most of the resistance to gas flow is provided by the porous distributor and not by the particle bed; therefore, localized variations of the quantity of particles above any particular gas inlet do not significantly alter the flow rate through that inlet

Contribution to the study of second phases particles dispersion in polycrystalline uranium dioxide

International Nuclear Information System (INIS)

Peres, V.

1994-06-01

To reduce fission gas release of irradiated polycrystalline uranium dioxide, the dispersion of intragranular nanometric particles of second phase necessary to pin gas bubbles may complete the advantage of a large-grained fuel microstructure. Moreover, intergranular glass films may improve high temperatures mechanical properties of UO 2 . In this study, mixtures of additives composed of ''corindon'' structure oxides that enhance the fuel grain growth and composed of different oxides with variable solid solubilities in the UO 2 matrix were achieved. Additives with a negligible solubility inhibit grain boundaries motion except those, such as silica, that involve a liquid phase at the sintering temperature. Rare earth oxides that form stable solid solutions with UO 2 cannot lead to precipitation, but have no effect on the fuel grain growth doped with ''corindon'' type oxides. A chromium oxide excess allows the creation of a fuel microstructure described by large grains and intragranular spherical Cr 2 O 3 inclusions observed by scanning electron microscopy. Values for the bulk lattice diffusion coefficient of Cr 3+ cations in UO 2 can be deduced from the experimental growth of those dispersed particles by an Ostwald ripening mechanism. The formation of small precipitated metal particles inside the uranium dioxide matrix induced by the internal reduction of a solid solution has not been performed. However, direct reduction of insoluble chromium oxide particles is easy and produces metallic intragranular precipitates. (author). 119 refs., 112 figs., 33 tabs., 5 annexes

Normal-dispersion microresonator Kerr frequency combs

Directory of Open Access Journals (Sweden)

Xue Xiaoxiao

2016-06-01

Full Text Available Optical microresonator-based Kerr frequency comb generation has developed into a hot research area in the past decade. Microresonator combs are promising for portable applications due to their potential for chip-level integration and low power consumption. According to the group velocity dispersion of the microresonator employed, research in this field may be classified into two categories: the anomalous dispersion regime and the normal dispersion regime. In this paper, we discuss the physics of Kerr comb generation in the normal dispersion regime and review recent experimental advances. The potential advantages and future directions of normal dispersion combs are also discussed.

Dispersion modeling by kinematic simulation: Cloud dispersion model

International Nuclear Information System (INIS)

Fung, J C H; Perkins, R J

2008-01-01

A new technique has been developed to compute mean and fluctuating concentrations in complex turbulent flows (tidal current near a coast and deep ocean). An initial distribution of material is discretized into any small clouds which are advected by a combination of the mean flow and large scale turbulence. The turbulence can be simulated either by kinematic simulation (KS) or direct numerical simulation. The clouds also diffuse relative to their centroids; the statistics for this are obtained from a separate calculation of the growth of individual clouds in small scale turbulence, generated by KS. The ensemble of discrete clouds is periodically re-discretized, to limit the size of the small clouds and prevent overlapping. The model is illustrated with simulations of dispersion in uniform flow, and the results are compared with analytic, steady state solutions. The aim of this study is to understand how pollutants disperses in a turbulent flow through a numerical simulation of fluid particle motion in a random flow field generated by Fourier modes. Although this homogeneous turbulent is rather a 'simple' flow, it represents a building block toward understanding pollutant dispersion in more complex flow. The results presented here are preliminary in nature, but we expect that similar qualitative results should be observed in a genuine turbulent flow.

Determination of twelve herbicides in tobacco by a combination of solid–liquid–solid dispersive extraction using multi-walled carbon nanotubes, dispersive liquid-liquid micro-extraction, and detection by GC with triple quadrupole mass spectrometry

International Nuclear Information System (INIS)

Liao, Qie Gen; Zhou, Yao Min; Luo, Lin Guang; Wang, Li Bing; Feng, Xiao Hu

2014-01-01

We report on a method for the determination of twelve herbicides using solid–liquid–solid dispersive extraction (SLSDE), followed by dispersive liquid-liquid micro-extraction (DLLME) and quantitation by gas chromatography with triple quadrupole mass spectrometric detection. SLSDE was applied to the extraction of herbicides from tobacco samples using multi-walled carbon nanotubes (MWCNTs) as clean-up adsorbents. The effect of the quantity of MWCNTs on SLSDE, and of type and volume of extraction and disperser solvents and of salt effect on DLLME were optimized. Good linearity is obtained in the 5.0 - 500 μg kg −1 concentration range, with regression coefficients of >0.99. Intra-day and inter-day repeatability, expressed as relative standard deviations, are between 3 and 9 %. The recoveries in case of herbicide-spiked tobacco at concentration levels of 20.0, 50.0 and 100.0 g kg −1 ranged from 79 to 105 %, and LODs are between 1.5 and 6.1 μg kg −1 . All the tobacco samples were found to contain butralin and pendimethalin at levels ranging from 15.8 to 500.0 μg kg −1 . (author)

Small-scale electricity generating facilities from natural gas : a measure to mitigate the greenhouse effect; Microgeneracion de energia con gas natural: una medida efectiva para mitigar el cambio climatico

Energy Technology Data Exchange (ETDEWEB)

Gutierrez, A. M.

2002-07-01

The forthcoming liberalization of the gas and electricity markets in Europe, in conjunction with the increase of the global energy consumption in the near future are enabling the development of natural gas alternatives to traditional large-scale centralized power plants. They emerged from research suggesting that the use of small-scale electricity generating facilities dispersed throughout the electrical network, provides the electricity system with measurable technical, economic and environmental benefits. In this sense, the distributed generation powered by cogeneration systems offers the biggest measure to mitigate the greenhouse effect due to the carbon dioxide. (Author)

Rapidly locating sources and predicting contaminant dispersion in buildings

International Nuclear Information System (INIS)

Sohn, Michael D.; Reynolds, Pamela; Gadgil, Ashok J.; Sextro, Richard G.

2002-01-01

Contaminant releases in or near a building can lead to significant human exposures unless prompt response measures are taken. However, selecting the proper response depends in part on knowing the source locations, the amounts released, and the dispersion characteristics of the pollutants. We present an approach that estimates this information in real time. It uses Bayesian statistics to interpret measurements from sensors placed in the building yielding best estimates and uncertainties for the release conditions, including the operating state of the building. Because the method is fast, it continuously updates the estimates as measurements stream in from the sensors. We show preliminary results for characterizing a gas release in a three-floor, multi-room building at the Dugway Proving Grounds, Utah, USA

Novel highly dispersible, thermally stable core/shell proppants for geothermal applications

Energy Technology Data Exchange (ETDEWEB)

Childers, Ian M.; Endres, Mackenzie; Burns, Carolyne; Garcia, Benjamin J.; Liu, Jian; Wietsma, Thomas W.; Bonneville, Alain; Moore, Joseph; Leavy, Ian I.; Zhong, Lirong; Schaef, Herbert T.; Fu, Li; Wang, Hong-Fei; Fernandez, Carlos A.

2017-11-01

The use of proppants during reservoir stimulation in tight oil and gas plays requires the introduction of highly viscous fluids to transport the proppants (µm–mm) with the fracturing fluid. The highly viscous fluids required result in increased pump loads and energy costs. Furthermore, although proppant deployment with fracturing fluids is a standard practice for unconventional oil and gas stimulation operations, there are only a few examples in the US of the applying proppant technology to geothermal energy production. This is due to proppant dissolution, proppant flowback and loss of permeability associated with the extreme temperatures found in enhanced geothermal systems (EGS). This work demonstrates proof-of-concept of a novel, CO2-responsive, lightweight sintered-bauxite/polymer core/shell proppant. The polymer shell has two main roles; 1) increase the stability of the proppant dispersion in water without the addition of rheology modifiers, and 2) once at the fracture network react with CO2 to promote particle aggregation and prop fractures open. In this work, both of these roles are demonstrated together with the thermal and chemical stability of the materials showing the potential of these CO2-responsive proppants as an alternative proppant technology for geothermal and unconventional oil/gas applications.

Polymer-Particle Nanocomposites: Size and Dispersion Effects

Science.gov (United States)

Moll, Joseph

Polymer-particle nanocomposites are used in industrial processes to enhance a broad range of material properties (e.g. mechanical, optical, electrical and gas permeability properties). This dissertation will focus on explanation and quantification of mechanical property improvements upon the addition of nanoparticles to polymeric materials. Nanoparticles, as enhancers of mechanical properties, are ubiquitous in synthetic and natural materials (e.g. automobile tires, packaging, bone), however, to date, there is no thorough understanding of the mechanism of their action. In this dissertation, silica (SiO2) nanoparticles, both bare and grafted with polystyrene (PS), are studied in polymeric matrices. Several variables of interest are considered, including particle dispersion state, particle size, length and density of grafted polymer chains, and volume fraction of SiO2. Polymer grafted nanoparticles behave akin to block copolymers, and this is critically leveraged to systematically vary nanoparticle dispersion and examine its role on the mechanical reinforcement in polymer based nanocomposites in the melt state. Rheology unequivocally shows that reinforcement is maximized by the formation of a transient, but long-lived, percolating polymer-particle network with the particles serving as the network junctions. The effects of dispersion and weight fraction of filler on nanocomposite mechanical properties are also studied in a bare particle system. Due to the interest in directional properties for many different materials, different means of inducing directional ordering of particle structures are also studied. Using a combination of electron microscopy and x-ray scattering, it is shown that shearing anisotropic NP assemblies (sheets or strings) causes them to orient, one in front of the other, into macroscopic two-dimensional structures along the flow direction. In contrast, no such flow-induced ordering occurs for well dispersed NPs or spherical NP aggregates! This work

UV curable aqueous dispersions for wood coatings

International Nuclear Information System (INIS)

Peeters, S.; Bleus, J.P.; Wang, Z.J.; Arceneaux, J. A.; Hall, J.

1999-01-01

In this paper the characterisation of aqueous dispersions of UV curable resins is described. Two types of dispersions were used: dispersions that are tacky after water evaporation and tack - free before cure dispersions. The physical and rheological properties of these products have been determined and the performance of these dispersions in various formulations, especially for wood applications has been studied. With these dispersions, it is possible to produce coatings having a good cure speed, good surface hardness and good solvent -, chemical - and water resistance

Experimental and Numerical Investigation of Effect of Air Stability on Exhaled Air Dispersion

DEFF Research Database (Denmark)

Xu, Chunwen; Gong, Guangcai; Nielsen, Peter Vilhelm

2014-01-01

studies. As the thermal stratification under displacement ventilation blocks the vertical movement of exhaled air, the exhaled contaminant may be trapped between temperature stratifications. As the dispersion of contaminant is closely related to the health of human indoors, the temperature structure...... was used for experimental study, and a numerical person was built to simulate the manikin. The velocity, temperature and concentration of tracer gas in exhaled air are affected by air stability to different degrees. The similarity of this effect among these parameters can also be observed through numerical...

Catchment Dispersion Mechanisms in an Urban Context

Science.gov (United States)

Gironas, J. A.; Mejia, A.; Rossel, F.; Rinaldo, A.; Rodriguez, F.

2014-12-01

Dispersion mechanisms have been examined in-depth in natural catchments in previous studies. However, these dispersion mechanisms have been studied little in urban catchments, where artificial transport elements and morphological arrangements are expected to modify travel times and mobilize excess rainfall from spatially distributed impervious sites. Thus, these features can modify the variance of the catchment's travel times and hence the total dispersion. This work quantifies the dispersion mechanisms in an urban catchment using the theory of transport by travel times as represented by the Urban Morpho-climatic Instantaneous Unit Hydrograph (U-McIUH) model. This model computes travel times based on kinematic wave theory and accounts explicitly for the path heterogeneities and altered connectivity patterns characteristic of an urban drainage network. The analysis is illustrated using the Aubinière urban catchment (France) as a case study. We found that kinematic dispersion is dominant for small rainfall intensities, whereas geomorphologic dispersion becomes more dominant for larger intensities. The total dispersion scales with the drainage area in a power law fashion. The kinematic dispersion is dominant across spatial scales up to a threshold of approximately 2-3 km2, after which the geomorphologic dispersion becomes more dominant. Overall, overland flow is responsible for most of the dispersion, while conduits tend to counteract the increase of the geomorphologic dispersion with a negative kinematic dispersion. Further studies with other catchments are needed to assess whether the latter is a general feature of urban drainage networks.

Reactimeter dispersion equation

OpenAIRE

A.G. Yuferov

2016-01-01

The aim of this work is to derive and analyze a reactimeter metrological model in the form of the dispersion equation which connects reactimeter input/output signal dispersions with superimposed random noise at the inlet. It is proposed to standardize the reactimeter equation form, presenting the main reactimeter computing unit by a convolution equation. Hence, the reactimeter metrological characteristics are completely determined by this unit hardware function which represents a transient re...

Modification of Einstein A Coefficient in Dissipative Gas Medium

Science.gov (United States)

Cao, Chang-Qi; Cao, Hui; Qin, Ke-Cheng

1996-01-01

Spontaneous radiation in dissipative gas medium such as plasmas is investigated by Langevin equations and the modified Weisskopf-Wigner approximation. Since the refractive index of gas medium is expected to be nearly unity, we shall first neglect the medium polarization effect. We show that absorption in plasmas may in certain case modify the Einstein A coefficient significantly and cause a pit in the A coefficient-density curves for relatively low temperature plasmas and also a pit in the A coefficient-temperature curves. In the next, the effect of medium polarization is taken into account in addition. To our surprise, its effect in certain case is quite significant. The dispersive curves show different behaviors in different region of parameters.

Experience in producing LEU fuel elements for the RSG-GAS

International Nuclear Information System (INIS)

Suripto, A.; Soentono, S.

1991-01-01

To achieve a self-reliance in the operation of the 30 MW Multipurpose Research Reactor at Serpong (the RSG-GAS), a fuel element production facility has been constructed nearby. The main task of the facility is to produce MTR type fuel and control elements containing U 3 O 8 -Al dispersion LEU fuel for the RSG-GAS. The hot commissioning activity has started in early 1988 after completion of the cold commissioning using depleted uranium in 1987, marking the beginning of the real production activity. This paper briefly describes the main features of the fuel production facility, the production experience gained so far, and its current production activity. (orig.)

Multiple inert gas elimination technique by micropore membrane inlet mass spectrometry--a comparison with reference gas chromatography.

Science.gov (United States)

Kretzschmar, Moritz; Schilling, Thomas; Vogt, Andreas; Rothen, Hans Ulrich; Borges, João Batista; Hachenberg, Thomas; Larsson, Anders; Baumgardner, James E; Hedenstierna, Göran

2013-10-15

The mismatching of alveolar ventilation and perfusion (VA/Q) is the major determinant of impaired gas exchange. The gold standard for measuring VA/Q distributions is based on measurements of the elimination and retention of infused inert gases. Conventional multiple inert gas elimination technique (MIGET) uses gas chromatography (GC) to measure the inert gas partial pressures, which requires tonometry of blood samples with a gas that can then be injected into the chromatograph. The method is laborious and requires meticulous care. A new technique based on micropore membrane inlet mass spectrometry (MMIMS) facilitates the handling of blood and gas samples and provides nearly real-time analysis. In this study we compared MIGET by GC and MMIMS in 10 piglets: 1) 3 with healthy lungs; 2) 4 with oleic acid injury; and 3) 3 with isolated left lower lobe ventilation. The different protocols ensured a large range of normal and abnormal VA/Q distributions. Eight inert gases (SF6, krypton, ethane, cyclopropane, desflurane, enflurane, diethyl ether, and acetone) were infused; six of these gases were measured with MMIMS, and six were measured with GC. We found close agreement of retention and excretion of the gases and the constructed VA/Q distributions between GC and MMIMS, and predicted PaO2 from both methods compared well with measured PaO2. VA/Q by GC produced more widely dispersed modes than MMIMS, explained in part by differences in the algorithms used to calculate VA/Q distributions. In conclusion, MMIMS enables faster measurement of VA/Q, is less demanding than GC, and produces comparable results.

Dispersal and biogeography of silica-scaled chrysophytes

DEFF Research Database (Denmark)

Kristiansen, Jørgen

2008-01-01

The silica-scaled chrysophytes—here mainly represented by the freshwater genera Mallomonas and Synura—have special problems in dispersal from one habitat to another because they cannot tolerate desiccation. Their dispersal is limited by the fragile construction and aquatic habit. Dispersal from one...... water body to another involves dangerous changes of the environment, and the ability to avoid desiccation during transport is crucial. So, air-borne and ectozoic dispersal by birds or mammals can only work at short distances. This danger may be avoided by endozoic dispersal of thick-walled cysts; as far....... The distribution of a species at a given time depends on several factors: dispersal capacity—available vectors—suitable available habitats—and most important: sufficient time for dispersal. It is remarkable that the chrysophytes—in spite of their fragile cell construction and apparently low dispersal capacity...

A mechanistic Eulerian-Lagrangian model for dispersed flow film boiling

International Nuclear Information System (INIS)

Andreani, M.; Yadigaroglu, G.

1991-01-01

In this paper a new mechanistic model of heat transfer in the dispersed flow regime is presented. The usual assumptions that render most of the available models unsuitable for the analysis of the reflooding phase of the LOCA are discussed, and a two-dimensional time-independent numerical model is developed. The gas temperature field is solved in a fixed-grid (Eulerian) mesh, with the droplets behaving as mass and energy sources. The histories of a large number of computational droplets are followed in a Lagrangian frame, considering evaporation, break-up and interactions with the vapor and with the wall. comparisons of calculated wall and vapor temperatures with experimental data are shown for two reflooding tests

Adenine versus Guanine Quartets in Aqueous Solution. Dispersion-Corrected DFT Study on the Differences in π-Stacking and Hydrogen-Bonding Behavior

NARCIS (Netherlands)

Fonseca Guerra, C.; van der Wijst, T.; Poater, J.; Swart, M.; Bickelhaupt, F.M.

2010-01-01

We have investigated the performance of the dispersion-corrected density functionals (BLYP-D, BP86-D and PBE-D) and the widely used B3LYP functional for describing the hydrogen bonds and the stacking interactions in DNA base dimers. For the gas-phase situation, the bonding energies have been

Oak Dispersal Syndromes: Do Red and White Oaks Exhibit Different Dispersal Srategies?

Science.gov (United States)

Michael Steele; Peter Smallwood; William B. Terzaghi; John E. Carlson; Thomas conteras; Amy McEuen

2004-01-01

We provide an overview of the ecological and evolutionary interactions between oaks and several of their dispersal agents, and review a series of studies that demonstrate how various acorn characteristics affect feeding and caching decisions of these animals, which in turn may influence oak dispersal and establishment. We demonstrate that acorns of red oak species show...

The dispersion of SWCNTs treated by coupling and dispersing agents in fiber reinforced polymer composities

Science.gov (United States)

Duan, Yuexin; Yuan, Lu; Zhao, Yan; Guan, Fengxia

2007-07-01

It is an obstacle issue for Carbon nanotubes (CNTs) applied in fiber reinforced polymer composites that CNTs is dispersed in nano-level, particularly for single-wall Carbon nanotubes (SWCNTs). In this paper, SWCNTs were treated by the coupling agent like volan and dispersing agent as BYK to improve the dispersion in the Glass Fiber/Epoxy composites. The result of dispersion of SWCNTs in composites was observed by Scanning electron microscopy (SEM). Then the Glass Transition Temperature (Tg) of these kinds of composites with treated and untreated SWCNTs were obtained by Dynamic Mechanical Thermal Analysis (DMTA). Moreover, the bending properties of these composites were tested.

Extragalactic dispersion measures of fast radio bursts

International Nuclear Information System (INIS)

Xu, Jun; Han, J. L.

2015-01-01

Fast radio bursts show large dispersion measures, much larger than the Galactic dispersion measure foreground. Therefore, they evidently have an extragalactic origin. We investigate possible contributions to the dispersion measure from host galaxies. We simulate the spatial distribution of fast radio bursts and calculate the dispersion measures along the sightlines from fast radio bursts to the edge of host galaxies by using the scaled NE2001 model for thermal electron density distributions. We find that contributions to the dispersion measure of fast radio bursts from the host galaxy follow a skew Gaussian distribution. The peak and the width at half maximum of the dispersion measure distribution increase with the inclination angle of a spiral galaxy, to large values when the inclination angle is over 70°. The largest dispersion measure produced by an edge-on spiral galaxy can reach a few thousand pc cm −3 , while the dispersion measures from dwarf galaxies and elliptical galaxies have a maximum of only a few tens of pc cm −3 . Notice, however, that additional dispersion measures of tens to hundreds of pc cm −3 can be produced by high density clumps in host galaxies. Simulations that include dispersion measure contributions from the Large Magellanic Cloud and the Andromeda Galaxy are shown as examples to demonstrate how to extract the dispersion measure from the intergalactic medium. (paper)

THE SINS/zC-SINF SURVEY OF z ∼ 2GALAXY KINEMATICS: THE NATURE OF DISPERSION-DOMINATED GALAXIES

International Nuclear Information System (INIS)

Newman, Sarah F.; Genzel, Reinhard; Förster Schreiber, Natascha M.; Buschkamp, Peter; Davies, Ric; Eisenhauer, Frank; Kurk, Jaron; Lutz, Dieter; Shapiro Griffin, Kristen; Mancini, Chiara; Renzini, Alvio; Lilly, Simon J.; Carollo, C. Marcella; Peng, Yingjie; Bouché, Nicolas; Burkert, Andreas; Cresci, Giovanni; Genel, Shy; Hicks, Erin K. S.; Naab, Thorsten

2013-01-01

We analyze the spectra, spatial distributions, and kinematics of Hα, [N II], and [S II] emission in a sample of 38, z ∼ 2.2 UV/optically selected star-forming galaxies (SFGs) from the SINS and zC-SINF surveys, 34 of which were observed in the adaptive optics mode of SINFONI and 30 of those contain data presented for the first time here. This is supplemented by kinematic data from 43 z ∼ 1-2.5 galaxies from the literature. None of these 81 galaxies is an obvious major merger. We find that the kinematic classification of high-z SFGs as ''dispersion dominated'' or ''rotation dominated'' correlates most strongly with their intrinsic sizes. Smaller galaxies are more likely ''dispersion-dominated'' for two main reasons: (1) the rotation velocity scales linearly with galaxy size but intrinsic velocity dispersion does not depend on size or may even increase in smaller galaxies, and as such, their ratio is systematically lower for smaller galaxies, and (2) beam smearing strongly decreases large-scale velocity gradients and increases observed dispersion much more for galaxies with sizes at or below the resolution. Dispersion-dominated SFGs may thus have intrinsic properties similar to ''rotation-dominated'' SFGs, but are primarily more compact, lower mass, less metal enriched, and may have higher gas fractions, plausibly because they represent an earlier evolutionary state.

Standardization and software infrastructure for gas hydrate data communications

Energy Technology Data Exchange (ETDEWEB)

Kroenlein, K.; Chirico, R.D.; Kazakov, A.; Frenkel, M. [National Inst. of Standards and Technology, Boulder, CO (United States). Physical and Chemical Properties Div.; Lowner, R. [GeoForschungsZentrum Potsdam (Germany); Wang, W. [Chinese Academy of Science, Beijing (China). Computer Network Information Center; Smith, T. [MIT Systems, Flushing, NY (United States); Sloan, E.D. [Colorado School of Mines, Golden, CO (United States). Centre for Hydrate Research

2008-07-01

The perceived value of gas hydrates as an energy resource for the future has led to extensive hydrate research studies and experiments. The hydrate deposits are widely dispersed throughout the world, and many countries are now investigating methods of extracting gas hydrate resources. This paper described a gas hydrates markup language (GHML) developed as an international standard for data transfer and storage within the gas hydrates community. The language is related to a hydrates database developed to facilitate a greater understanding of naturally occurring hydrate interactions with geophysical processes, and aid in the development of hydrate technologies for resource recovery and storage. Recent updates to the GHML included the addition of ThermoML, a communication standard for thermodynamic data into the GHML schema. The standard will be used to represent all gas hydrates thermodynamic data. A new element for the description of crystal structures has also been developed, as well as a guided data capture tool. The tool is available free of charge and is publicly licensed for use by gas hydrate data producers. A web service has also been provided to ensure that access to GHML files for gas hydrates and data files are available for users. It was concluded that the tool will help to ensure data quality assurance for the conversion of data and meta-data within the database. 28 refs., 9 figs.

Longitudinal dispersion coefficient depending on superficial velocity of hydrogen isotopes flowing in column packed with zeolite pellets at 77.4 K

Energy Technology Data Exchange (ETDEWEB)

Kotoh, K. [Faculty of Engineering, Kyushu University, Nishi-ku, Fukuoka (Japan); Graduate School of Engineering, Kyushu University, Nishi-ku, Fukuoka (Japan); Kubo, K.; Takashima, S.; Moriyama, S.T. [Graduate School of Engineering, Kyushu University, Nishi-ku, Fukuoka (Japan); Tanaka, M. [National Institute for Fusion Science, Oroshi-cho, Toki, Gifu (Japan); Sugiyama, T. [Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan)

2015-03-15

Authors have been developing a cryogenic pressure swing adsorption system for hydrogen isotope separation. In the problem of its design and operation, it is necessary to predict the concentration profiles developing in packed beds of adsorbent pellets. The profiling is affected by the longitudinal dispersion of gas flowing in packed beds, in addition to the mass transfer resistance in porous media of adsorbent pellets. In this work, an equation is derived for estimating the packed-bed dispersion coefficient of hydrogen isotopes, by analyzing the breakthrough curves of trace D{sub 2} or HD replacing H{sub 2} adsorbed in synthetic zeolite particles packed columns at the liquefied nitrogen temperature 77.4 K. Since specialized for hydrogen isotopes, this equation can be considered to estimate the dispersion coefficients more reliable for the cryogenic hydrogen isotope adsorption process, than the existing equations. (authors)

Some results of a numerical calculation of plasma dispersion curves including collisions; Quelques resultats de calcul de courbes de dispersion avec collisions

Energy Technology Data Exchange (ETDEWEB)

Lepechinsky, D; Parlange, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

Dispersion curves including the effect of collisions have been calculated with a 7090 IBM computer for several types of laboratory hydrogen plasmas; Te = Ti = 1 eV; Te = 1 eV, Ti = 0,1 eV; Te = 10 eV, Ti = 2 eV; Te = 50 eV, Ti 10 eV, with neutral gas pressures of 10{sup -1}, 10{sup -3} and 10{sup -4} mmHg and electron densities of 10{sup 10}, 10{sup 13} and eventually 10{sup 15} el/cc. The corresponding collision frequencies with neutrals and between electrons and ions have been derived using appropriate relationships The dispersion equations used correspond to the macroscopic treatment. The real and imaginary parts of the wave number K are presented as a function of real values of the frequency {omega}, for electrostatic and electromagnetic waves and for e.m. waves propagating parallel to a permanent magnetic field of 500 gauss and 12.5 Kgauss. (authors) [French] Des courbes de dispersion tenant compte de l'effet des collisions ont ete calculees a l'aide d'un ordinateur IBM 7090 pour differents types de plasmas d'hydrogene se presentant au laboratoire; les temperatures electroniques et ioniques envisagees ont ete les suivantes: Te = Ti = 1 Ev; Te = 1 eV, Ti 0,1 eV; Te = 10 eV, Ti = 2 eV; Te = 50 eV, Ti = 10 eV; les pressions de neutres - de 10{sup -1}, 10{sup -3} et 10{sup -4} mmHg; les densites electroniques - de 10{sup 10}, 10{sup 13} et eventuellement de 10{sup 15} el/cc. Les frequences de collision avec les neutres et entre electrons et ions ont ete evaluees en fonction de ces donnees. Les equations, de dispersion utilisees correspondant au traitement macroscopique. On presente les valeurs des parties reelle et imaginaire du nombre d'ondes K en fonction de valeurs reelles de la frequence {omega} pour les ondes electrostatiques et electromagnetiques et pour les ondes e.m. se propageant parallelement a un champ magnetique permanent de 500 gauss et de 12,5 kgauss. (auteurs)

Dispersion of coupled mode-gap cavities

NARCIS (Netherlands)

Lian, Jin; Sokolov, Sergei; Yuce, E.; Combrie, S.; de Rossi, A.; Mosk, Allard

2015-01-01

The dispersion of a coupled resonator optical waveguide made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the inherent dispersive cavity

Discrete dispersion models and their Tweedie asymptotics

DEFF Research Database (Denmark)

Jørgensen, Bent; Kokonendji, Célestin C.

2016-01-01

The paper introduce a class of two-parameter discrete dispersion models, obtained by combining convolution with a factorial tilting operation, similar to exponential dispersion models which combine convolution and exponential tilting. The equidispersed Poisson model has a special place in this ap......The paper introduce a class of two-parameter discrete dispersion models, obtained by combining convolution with a factorial tilting operation, similar to exponential dispersion models which combine convolution and exponential tilting. The equidispersed Poisson model has a special place...... in this approach, whereas several overdispersed discrete distributions, such as the Neyman Type A, Pólya-Aeppli, negative binomial and Poisson-inverse Gaussian, turn out to be Poisson-Tweedie factorial dispersion models with power dispersion functions, analogous to ordinary Tweedie exponential dispersion models...... with power variance functions. Using the factorial cumulant generating function as tool, we introduce a dilation operation as a discrete analogue of scaling, generalizing binomial thinning. The Poisson-Tweedie factorial dispersion models are closed under dilation, which in turn leads to a Poisson...

Improved quantification of CO2 emission at Campi Flegrei by combined Lagrangian Stochastic and Eulerian dispersion modelling

Science.gov (United States)

Pedone, Maria; Granieri, Domenico; Moretti, Roberto; Fedele, Alessandro; Troise, Claudia; Somma, Renato; De Natale, Giuseppe

2017-12-01

This study investigates fumarolic CO2 emissions at Campi Flegrei (Southern Italy) and their dispersion in the lowest atmospheric boundary layer. We innovatively utilize a Lagrangian Stochastic dispersion model (WindTrax) combined with an Eulerian model (DISGAS) to diagnose the dispersion of diluted gas plumes over large and complex topographic domains. New measurements of CO2 concentrations acquired in February and October 2014 in the area of Pisciarelli and Solfatara, the two major fumarolic fields of Campi Flegrei caldera, and simultaneous measurements of meteorological parameters are used to: 1) test the ability of WindTrax to calculate the fumarolic CO2 flux from the investigated sources, and 2) perform predictive numerical simulations to resolve the mutual interference between the CO2 emissions of the two adjacent areas. This novel approach allows us to a) better quantify the CO2 emission of the fumarolic source, b) discriminate ;true; CO2 contributions for each source, and c) understand the potential impact of the composite CO2 plume (Pisciarelli ;plus; Solfatara) on the highly populated areas inside the Campi Flegrei caldera.

Mid-infrared frequency comb via coherent dispersive wave generation in silicon nitride nanophotonic waveguides

Science.gov (United States)

Guo, Hairun; Herkommer, Clemens; Billat, Adrien; Grassani, Davide; Zhang, Chuankun; Pfeiffer, Martin H. P.; Weng, Wenle; Brès, Camille-Sophie; Kippenberg, Tobias J.

2018-06-01

Mid-infrared optical frequency combs are of significant interest for molecular spectroscopy due to the large absorption of molecular vibrational modes on the one hand, and the ability to implement superior comb-based spectroscopic modalities with increased speed, sensitivity and precision on the other hand. Here, we demonstrate a simple, yet effective, method for the direct generation of mid-infrared optical frequency combs in the region from 2.5 to 4.0 μm (that is, 2,500-4,000 cm-1), covering a large fraction of the functional group region, from a conventional and compact erbium-fibre-based femtosecond laser in the telecommunication band (that is, 1.55 μm). The wavelength conversion is based on dispersive wave generation within the supercontinuum process in an unprecedented large-cross-section silicon nitride (Si3N4) waveguide with the dispersion lithographically engineered. The long-wavelength dispersive wave can perform as a mid-infrared frequency comb, whose coherence is demonstrated via optical heterodyne measurements. Such an approach can be considered as an alternative option to mid-infrared frequency comb generation. Moreover, it has the potential to realize compact dual-comb spectrometers. The generated combs also have a fine teeth-spacing, making them suitable for gas-phase analysis.

Single-particle dispersion in compressible turbulence

Science.gov (United States)

Zhang, Qingqing; Xiao, Zuoli

2018-04-01

Single-particle dispersion statistics in compressible box turbulence are studied using direct numerical simulation. Focus is placed on the detailed discussion of effects of the particle Stokes number and turbulent Mach number, as well as the forcing type. When solenoidal forcing is adopted, it is found that the single-particle dispersion undergoes a transition from the ballistic regime at short times to the diffusive regime at long times, in agreement with Taylor's particle dispersion argument. The strongest dispersion of heavy particles is announced when the Stokes number is of order 1, which is similar to the scenario in incompressible turbulence. The dispersion tends to be suppressed as the Mach number increases. When hybrid solenoidal and compressive forcing at a ratio of 1/2 is employed, the flow field shows apparent anisotropic property, characterized by the appearance of large shock wave structures. Accordingly, the single-particle dispersion shows extremely different behavior from the solenoidal forcing case.

Fabrication of Ni@Ti core-shell nanoparticles by modified gas aggregation source

Science.gov (United States)

Hanuš, J.; Vaidulych, M.; Kylián, O.; Choukourov, A.; Kousal, J.; Khalakhan, I.; Cieslar, M.; Solař, P.; Biederman, H.

2017-11-01

Ni@Ti core-shell nanoparticles were prepared by a vacuum based method using the gas aggregation source (GAS) of nanoparticles. Ni nanoparticles fabricated in the GAS were afterwards coated by a Ti shell. The Ti shell was deposited by means of magnetron sputtering. The Ni nanoparticles were decelerated in the vicinity of the magnetron to the Ar drift velocity in the second deposition chamber. X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy analysis of the nanoparticles showed the core-shell structure. It was shown that the thickness of the shell can be easily tuned by the process parameters with a maximum achieved thickness of the Ti shell ~2.5 nm. The core-shell structure was confirmed by the STEM analysis of the particles.

Efficient sample preparation method based on solvent-assisted dispersive solid-phase extraction for the trace detection of butachlor in urine and waste water samples.

Science.gov (United States)

Aladaghlo, Zolfaghar; Fakhari, Alireza; Behbahani, Mohammad

2016-10-01

In this work, an efficient sample preparation method termed solvent-assisted dispersive solid-phase extraction was applied. The used sample preparation method was based on the dispersion of the sorbent (benzophenone) into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre-concentration of the butachlor, the cloudy solution was centrifuged and butachlor in the sediment phase dissolved in ethanol and determined by gas chromatography with flame ionization detection. Under the optimized conditions (solution pH = 7.0, sorbent: benzophenone, 2%, disperser solvent: ethanol, 500 μL, centrifuged at 4000 rpm for 3 min), the method detection limit for butachlor was 2, 3 and 3 μg/L for distilled water, waste water, and urine sample, respectively. Furthermore, the preconcentration factor was 198.8, 175.0, and 174.2 in distilled water, waste water, and urine sample, respectively. Solvent-assisted dispersive solid-phase extraction was successfully used for the trace monitoring of butachlor in urine and waste water samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Proto-planetary disc evolution and dispersal

Science.gov (United States)

Rosotti, Giovanni Pietro

2015-05-01

Planets form from gas and dust discs in orbit around young stars. The timescale for planet formation is constrained by the lifetime of these discs. The properties of the formed planetary systems depend thus on the evolution and final dispersal of the discs, which is the main topic of this thesis. Observations reveal the existence of a class of discs called "transitional", which lack dust in their inner regions. They are thought to be the last stage before the complete disc dispersal, and hence they may provide the key to understanding the mechanisms behind disc evolution. X-ray photoevaporation and planet formation have been studied as possible physical mechanisms responsible for the final dispersal of discs. However up to now, these two phenomena have been studied separately, neglecting any possible feedback or interaction. In this thesis we have investigated what is the interplay between these two processes. We show that the presence of a giant planet in a photo-evaporating disc can significantly shorten its lifetime, by cutting the inner regions from the mass reservoir in the exterior of the disc. This mechanism produces transition discs that for a given mass accretion rate have larger holes than in models considering only X-ray photo-evaporation, constituting a possible route to the formation of accreting transition discs with large holes. These discs are found in observations and still constitute a puzzle for the theory. Inclusion of the phenomenon called "thermal sweeping", a violent instability that can destroy a whole disc in as little as 10 4 years, shows that the outer disc left can be very short-lived (depending on the X-ray luminosity of the star), possibly explaining why very few non accreting transition discs are observed. However the mechanism does not seem to be efficient enough to reconcile with observations. In this thesis we also show that X-ray photo-evaporation naturally explains the observed correlation between stellar masses and accretion

Physical modelling of the dispersion of heavy gases released in an accident for the assessment of hazardous areas in built-up terrain

International Nuclear Information System (INIS)

Marotzke, K.

1993-01-01

The report on experimental results which were obtained above all within the heavy gas dispersion phase of the clouds. This phase extends up to a distance from the source distance in which the initial heavy gas concentration has decreased to about 1% by volume of the source concentration. The lower ignition limit of all gases of interest for industrial applications is above this threshold; the ignition distances of combustible gases can therefore be determined directly in the physical model. The concentration field in the complex near field of the cloud is modelled physically. The results obtained in the wind tunnel serve as input data for a numeric model; the concentrations and the dose values at points in the far field can be calculated with the model. The main section contains a detailed dimensional analysis for the two fundamentally possible emission types, i.e. spontaneous and continuous emissions. An experimental program was developed on this basis. With the program, the heavy gas dispersion under the influence of 25 different obstacle configurations was investigated. The results were represented in diagrams. With the aid of the diagrams, the lower ignition distances can be determined for combustible gases; for toxic gases, the initial conditions for the numeric far field model. (orig./KW) [de

Nest-mediated seed dispersal

Science.gov (United States)

Robert J. Warren; Jason P. Love; Mark A. Bradford

2017-01-01

Many plant seeds travel on the wind and through animal ingestion or adhesion; however, an overlooked dispersal mode may lurk within those dispersal modes. Viable seeds may remain attached or embedded within materials birds gather for nest building. Our objective was to determine if birds inadvertently transport seeds when they forage for plant materials to...

Atmospheric dispersion of radioactive materials

International Nuclear Information System (INIS)

Chino, Masamichi

1988-01-01

The report describes currently available techniques for predicting the dispersion of accidentally released radioactive materials and techniques for visualization using computer graphics. A simulation study is also made on the dispersion of radioactive materials released from the Chernobyl plant. The simplest models include the Gauss plume model and the puff model, which cannot serve to analyze the effects of the topography, vertical wind shear, temperature inversion layer, etc. Numerical analysis methods using advection and dispersion equations are widely adopted for detailed evaluation of dispersion in an emergency. An objective analysis model or a hydrodynamical model is often used to calculate the air currents which are required to determine the advection. A small system based on the puff model is widely adopted in Europe, where the topography is considered to have only simple effects. A more sophisticated large-sized system is required in nuclear facilities located in an area with more complex topographic features. An emergency system for dispersion calculation should be equipped with a graphic display to serve for quick understanding of the radioactivity distribution. (Nogami, K.)

Gas turbine exhaust system silencing design

International Nuclear Information System (INIS)

Ozgur, D.

1991-01-01

Gas turbines are the preferred prime mover in many applications because of their high efficiency, fuel flexibility, and low environmental impact. A typical mid-size machine might have a power rating of 80 MW, a flow of about 1000 kg/hr, and an exhaust temperature of over 500C. The most powerful single source of noise is generally the exhaust, which may generate over a kilowatt of acoustic energy. This paper reports that there are two important ways in which exhaust systems can radiate noise. The first is through the discharge of the exhaust duct, with the exhaust gas. Because of the large quantity of hot gas, the duct exit is always oriented vertically; it may be fairly high in the air in order to promote dispersion of the exhaust plume. This source is almost always attenuated by means of a silencer located somewhere in the ductwork. The second source of noise is often called breakout; it is the radiation of exhaust noise through the walls of the ducting. Breakout is most important for those sections of the exhaust duct which lie upstream of the silencer, where sound levels inside the ducting are highest. Both exhaust duct exit noise and breakout noise can be calculated from the sound power level of the gas turbine exhaust and the sound transmission loss (TL) of the silencer and ducting

Reactor for tracking catalyst nanoparticles in liquid at high temperature under a high-pressure gas phase with X-ray absorption spectroscopy.

Science.gov (United States)

Nguyen, Luan; Tao, Franklin Feng

2018-02-01

Structure of catalyst nanoparticles dispersed in liquid phase at high temperature under gas phase of reactant(s) at higher pressure (≥5 bars) is important for fundamental understanding of catalytic reactions performed on these catalyst nanoparticles. Most structural characterizations of a catalyst performing catalysis in liquid at high temperature under gas phase at high pressure were performed in an ex situ condition in terms of characterizations before or after catalysis since, from technical point of view, access to the catalyst nanoparticles during catalysis in liquid phase at high temperature under high pressure reactant gas is challenging. Here we designed a reactor which allows us to perform structural characterization using X-ray absorption spectroscopy including X-ray absorption near edge structure spectroscopy and extended X-ray absorption fine structure spectroscopy to study catalyst nanoparticles under harsh catalysis conditions in terms of liquid up to 350 °C under gas phase with a pressure up to 50 bars. This reactor remains nanoparticles of a catalyst homogeneously dispersed in liquid during catalysis and X-ray absorption spectroscopy characterization.

Dispersant affects the cellular influences of single-wall carbon nanotube: the role of CNT as carrier of dispersants.

Science.gov (United States)

Horie, Masanori; Stowe, Mayumi; Tabei, Miki; Kato, Haruhisa; Nakamura, Ayako; Endoh, Shigehisa; Morimoto, Yasuo; Fujita, Katsuhide

2013-06-01

The application of carbon nanotube (CNT) as a functional material to engineering and life sciences is advanced. In order to evaluate the cytotoxicity of CNT in vitro, some chemical and biological reagents are used for dispersants. In the present study, the cellular influences of six kinds of chemical or biological reagents used as dispersants were examined. Pluronic F-127, Pluronic F-68, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), pulmonary surfactant preparation Surfacten®, bovine serum albumin (BSA) and Tween 80 were used in the preparation of CNT-medium dispersants. The influences of each reagent on cell viability in human lung carcinoma A549 cells were small. However, Pluronic F-127, DPPC, Surfacten® and Tween 80 induced an increase of intracellular reactive oxygen species (ROS) level. Next, CNT-medium dispersions were prepared, using each reagent as a dispersant and applied to A549 cells. The cellular influences depended on the kind of dispersant. Cells exposed to CNT dispersion including Pluronic® F-127, Surfacten®, DPPC and Tween 80 showed LDH release to the culture supernatant. Induction of intracellular ROS level was observed in cells exposed to CNT dispersion including each reagent except BSA. These results suggest that the adsorbed dispersant reagents on the surface of the CNT affect its cellular influences, particularly the induction of oxidative stress.

Significance of the molecular diffusion for chemical and isotopic separation during the formation and degradation of natural gas reservoirs

International Nuclear Information System (INIS)

Hermichen, W.D.; Schuetze, H.

1987-01-01

Investigations at natural gas fields as well as modelling experiments have pointed out that changes of the chemical and isotopic composition occur in the course of migration, accumulation and dispersion of natural gas. Dissolution and sorption processes as well as in particular the diffusion process are considered to be the elementary separation processes. The influences on dissolved and freely flowing gases and on stationary gas accumulation are described by differential equations. The simulation of the following phenomena is shown: (1) immigration of gas into the pore space which is hydrodynamically passive, (2) diffusive migration of gas into the environment of the accumulation, and (3) diffusive 'decompression' into the roof and the floor of a gas bed and a gas containing subsoil water stratum, respectively. (author)

Electric field driven plasmon dispersion in AlGaN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Tan Ren-Bing; Qin Hua; Zhang Xiao-Yu; Xu Wen

2013-01-01

We present a theoretical study on the electric field driven plasmon dispersion of the two-dimensional electron gas (2DEG) in AlGaN/GaN high electron mobility transistors (HEMTs). By introducing a drifted Fermi—Dirac distribution, we calculate the transport properties of the 2DEG in the AlGaN/GaN interface by employing the balance-equation approach based on the Boltzmann equation. Then, the nonequilibrium Fermi—Dirac function is obtained by applying the calculated electron drift velocity and electron temperature. Under random phase approximation (RPA), the electric field driven plasmon dispersion is investigated. The calculated results indicate that the plasmon frequency is dominated by both the electric field E and the angle between wavevector q and electric field E. Importantly, the plasmon frequency could be tuned by the applied source—drain bias voltage besides the gate voltage (change of the electron density)

Continuous gas-phase hydroformylation of 1-butene using supported ionic liquid phase (SILP) catalysts

DEFF Research Database (Denmark)

Haumann, Marco; Dentler, Katharina; Joni, Joni

2007-01-01

The concept of supported ionic liquid phase (SILP) catalysis has been extended to 1-butene hydroformylation. A rhodium-sulfoxantphos complex was dissolved in [BMIM][n-C8H17OSO3] and this solution was highly dispersed on silica. Continuous gas-phase experiments in a fixed-bed reactor revealed...

A new NAMA framework for dispersed energy end-use sectors

International Nuclear Information System (INIS)

Cheng, C.-C.

2010-01-01

This paper presents a new approach for a nationally appropriate mitigation actions (NAMA) framework that can unlock the huge potential for greenhouse gas mitigation in dispersed energy end-use sectors in developing countries; specifically, the building sector and the industrial sector. These two sectors make up the largest portions of energy consumption in developing countries. However, due to multiple barriers and lack of effective polices, energy efficiency in dispersed energy end-use sectors has not been effectively put into practice. The new NAMA framework described in this paper is designed to fulfill the demand for public policies and public sector investment in developing countries and thereby boost private sector investment through project based market mechanisms, such as CDM. The new NAMA framework is designed as a need-based mechanism which effectively considers the conditions of each developing country. The building sector is used as an example to demonstrate how NAMA measures can be registered and implemented. The described new NAMA framework has the ability to interface efficiently with Kyoto Protocol mechanisms and to facilitate a systematic uptake for GHG emission reduction investment projects. This is an essential step to achieve the global climate change mitigation target and support sustainable development in developing countries.

Solvent-assisted dispersive solid-phase extraction: A sample preparation method for trace detection of diazinon in urine and environmental water samples.

Science.gov (United States)

Aladaghlo, Zolfaghar; Fakhari, Alireza; Behbahani, Mohammad

2016-09-02

In this research, a sample preparation method termed solvent-assisted dispersive solid-phase extraction (SA-DSPE) was applied. The used sample preparation method was based on the dispersion of the sorbent into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was received by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre-concentration of the diazinon, the cloudy solution was centrifuged and diazinon in the sediment phase dissolved in ethanol and determined by gas chromatography-flame ionization detector. Under the optimized conditions (pH of solution=7.0, Sorbent: benzophenone, 2%, Disperser solvent: ethanol, 500μL, Centrifuge: centrifuged at 4000rpm for 3min), the method detection limit for diazinon was 0.2, 0.3, 0.3 and 0.3μgL(-1) for distilled water, lake water, waste water and urine sample, respectively. Furthermore, the pre-concentration factor was 363.8, 356.1, 360.7 and 353.38 in distilled water, waste water, lake water and urine sample, respectively. SA-DSPE was successfully used for trace monitoring of diazinon in urine, lake and waste water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Acid dispersion abatement: the use of flue gas desulphurisation in the UK

Energy Technology Data Exchange (ETDEWEB)

Longhurst, J.W.S.; Health, B.A.; Gibber, D.C. [Manchester Metropolitan University, Manchester (United Kingdom). Atmospheric Research and Information Centre, Dept. of Environmental and Geographical Sciences

1995-12-31

This paper reviews and evaluates the development of the UK flue gas desulphurisation (FGD) programme. This programme on establishment in 1986 represented a planned and coherent approach to acid deposition abatement which would progressively reduce emissions whilst maintaining the UK`s coal fired power generation capacity. It was anticipated that at least 12000 MW of electricity generating plant would be retrofitted with FGD. The programme has effectively been abandoned in favour of market based approach to emission control which sets the targets to be achieved but not the means. As a consequence the retrofitted capacity in 1995 is just 6000 MW. 17 refs., 1 tab.

Glass-liquid-glass reentrance in mono-component colloidal dispersions

International Nuclear Information System (INIS)

Ramirez-Gonzalez, P E; Medina-Noyola, M; Vizcarra-Rendon, A; Guevara-Rodriguez, F de J

2008-01-01

The self-consistent generalized Langevin equation (SCGLE) theory of colloid dynamics is employed to describe the ergodic-non-ergodic transition in model mono-disperse colloidal dispersions whose particles interact through hard-sphere plus short-ranged attractive forces. The ergodic-non-ergodic phase diagram in the temperature-concentration state space is determined for the hard-sphere plus attractive Yukawa model within the mean spherical approximation for the static structure factor by solving a remarkably simple equation for the localization length of the colloidal particles. Finite real values of this property signals non-ergodicity and determines the non-ergodic parameters f(k) and f s (k). The resulting phase diagram for this system, which involves the existence of reentrant (repulsive and attractive) glass states, is compared with the corresponding prediction of mode coupling theory. Although both theories coincide in the general features of this phase diagram, there are also clear qualitative differences. One of the most relevant is the SCGLE prediction that the ergodic-attractive glass transition does not preempt the gas-liquid phase transition, but always intersects the corresponding spinodal curve on its high-concentration side. We also calculate the ergodic-non-ergodic phase diagram for the sticky hard-sphere model to illustrate the dependence of the predicted SCGLE dynamic phase diagram on the choice of one important constituent element of the SCGLE theory

Glass-liquid-glass reentrance in mono-component colloidal dispersions

Energy Technology Data Exchange (ETDEWEB)

Ramirez-Gonzalez, P E; Medina-Noyola, M [Instituto de Fisica ' Manuel Sandoval Vallarta' , Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi, SLP (Mexico); Vizcarra-Rendon, A [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Paseo la Bufa y Calzada Solidaridad, 98600, Zacatecas, Zac. (Mexico); Guevara-Rodriguez, F de J [Coordinacion de IngenierIa Molecular, Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas 152, 07730 Mexico, DF (Mexico)

2008-05-21

The self-consistent generalized Langevin equation (SCGLE) theory of colloid dynamics is employed to describe the ergodic-non-ergodic transition in model mono-disperse colloidal dispersions whose particles interact through hard-sphere plus short-ranged attractive forces. The ergodic-non-ergodic phase diagram in the temperature-concentration state space is determined for the hard-sphere plus attractive Yukawa model within the mean spherical approximation for the static structure factor by solving a remarkably simple equation for the localization length of the colloidal particles. Finite real values of this property signals non-ergodicity and determines the non-ergodic parameters f(k) and f{sub s}(k). The resulting phase diagram for this system, which involves the existence of reentrant (repulsive and attractive) glass states, is compared with the corresponding prediction of mode coupling theory. Although both theories coincide in the general features of this phase diagram, there are also clear qualitative differences. One of the most relevant is the SCGLE prediction that the ergodic-attractive glass transition does not preempt the gas-liquid phase transition, but always intersects the corresponding spinodal curve on its high-concentration side. We also calculate the ergodic-non-ergodic phase diagram for the sticky hard-sphere model to illustrate the dependence of the predicted SCGLE dynamic phase diagram on the choice of one important constituent element of the SCGLE theory.

Effectiveness of dispersants on thick oil slicks

International Nuclear Information System (INIS)

Ross, S.; Belore, R.

1993-01-01

Experiments were conducted to determine the relationship between dispersant effectiveness and oil slick thickness, and thereby determine the optimum time for applying dispersant onto spilled oil at sea. Tests were completed at a lab-scale level by varying the three parameters of oil type, dispersant application, and oil thickness. The tests were intended to be comparative only. The primary oils used were Alberta sweet mix blend and Hibernia B-27 crude. The dispersant, Corexit 9527, was applied either premixed with the oil, dropwise in one application, or dropwise in multiple applications to simulate a multi-hit aircraft operation. The apparatus used in the experiment was an oscillating hoop tank, with oil-containing rings used to obtain and maintain uniform slick thickness. The results indicate that the effectiveness potential of a chemical dispersant does not decrease as slick thickness increases. In fact, results of the tests involving Hibernia oil suggest that oils that tend to herd easily would be treated more effectively if dispersant were applied when the oil was relatively thick (1 mm or greater) to avoid herding problems. The oil slicks premixed with dispersant did not disperse well in the thick oil tests, not because of dispersant-oil interaction problems but because of reduced mixing energy. 6 refs., 4 figs., 1 tab

EVALUATION OF A PORTABLE FOURIER TRANSFORM INFRARED GAS ANALYZER FOR MEASUREMENTS OF AIR TOXICS IN POLLUTION PREVENTION RESEARCH

Science.gov (United States)

A portable Fourier transform infrared gas analyzer with a photoacoustic detector performed reliably during pollution prevention research at two industrial facilities. It exhibited good agreement (within approximately 6%) with other analytical instruments (dispersive infrared and ...

Dispersal Timing: Emigration of Insects Living in Patchy Environments.

Directory of Open Access Journals (Sweden)

Milica Lakovic

Full Text Available Dispersal is a life-history trait affecting dynamics and persistence of populations; it evolves under various known selective pressures. Theoretical studies on dispersal typically assume 'natal dispersal', where individuals emigrate right after birth. But emigration may also occur during a later moment within a reproductive season ('breeding dispersal'. For example, some female butterflies first deposit eggs in their natal patch before migrating to other site(s to continue egg-laying there. How breeding compared to natal dispersal influences the evolution of dispersal has not been explored. To close this gap we used an individual-based simulation approach to analyze (i the evolution of timing of breeding dispersal in annual organisms, (ii its influence on dispersal (compared to natal dispersal. Furthermore, we tested (iii its performance in direct evolutionary contest with individuals following a natal dispersal strategy. Our results show that evolution should typically result in lower dispersal under breeding dispersal, especially when costs of dispersal are low and population size is small. By distributing offspring evenly across two patches, breeding dispersal allows reducing direct sibling competition in the next generation whereas natal dispersal can only reduce trans-generational kin competition by producing highly dispersive offspring in each generation. The added benefit of breeding dispersal is most prominent in patches with small population sizes. Finally, the evolutionary contests show that a breeding dispersal strategy would universally out-compete natal dispersal.

Partitioning of fresh crude oil between floating, dispersed and sediment phases: Effect of exposure order to dispersant and granular materials.

Science.gov (United States)

Boglaienko, Daria; Tansel, Berrin

2016-06-15

When three or more high and low energy substrates are mixed, wetting order can significantly affect the behavior of the mixture. We analyzed the phase distribution of fresh floating Louisiana crude oil into dispersed, settled and floating phases depending on the exposure sequence to Corexit 9500A (dispersant) and granular materials. In the experiments artificial sea water at salinity 34‰ was used. Limestone (2.00-0.300 mm) and quartz sand (0.300-0.075 mm) were used as the natural granular materials. Dispersant Corexit 9500A increased the amount of dispersed oil up to 33.76 ± 7.04%. Addition of granular materials after the dispersant increased dispersion of oil to 47.96 ± 1.96%. When solid particles were applied on the floating oil before the dispersant, oil was captured as oil-particle aggregates and removed from the floating layer. However, dispersant addition led to partial release of the captured oil, removing it from the aggregated form to the dispersed and floating phases. There was no visible oil aggregation with the granular materials when quartz or limestone was at the bottom of the flask before the addition of oil and dispersant. The results show that granular materials can be effective when applied from the surface for aggregating or dispersing oil. However, the granular materials in the sediments are not effective neither for aggregating nor dispersing floating oil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Solitonic Dispersive Hydrodynamics: Theory and Observation

Science.gov (United States)

Maiden, Michelle D.; Anderson, Dalton V.; Franco, Nevil A.; El, Gennady A.; Hoefer, Mark A.

2018-04-01

Ubiquitous nonlinear waves in dispersive media include localized solitons and extended hydrodynamic states such as dispersive shock waves. Despite their physical prominence and the development of thorough theoretical and experimental investigations of each separately, experiments and a unified theory of solitons and dispersive hydrodynamics are lacking. Here, a general soliton-mean field theory is introduced and used to describe the propagation of solitons in macroscopic hydrodynamic flows. Two universal adiabatic invariants of motion are identified that predict trapping or transmission of solitons by hydrodynamic states. The result of solitons incident upon smooth expansion waves or compressive, rapidly oscillating dispersive shock waves is the same, an effect termed hydrodynamic reciprocity. Experiments on viscous fluid conduits quantitatively confirm the soliton-mean field theory with broader implications for nonlinear optics, superfluids, geophysical fluids, and other dispersive hydrodynamic media.

CASCADER: An M-chain gas-phase radionuclide transport and fate model

International Nuclear Information System (INIS)

Cawlfield, D.E.; Emer, D.F.; Lindstrom, F.T.; Shott, G.J.

1993-09-01

Chemicals and radionuclides move either in the gas-phase, liquid-phase, or both phases in soils. They may be acted upon by either biological or abiotic processes through advection and/or dispersion. Additionally during the transport of parent and daughter radionuclides in soil, radionuclide decay may occur. This version of CASCADER called CASCADR9 starts with the concepts presented in volumes one and three of this series. For a proper understanding of how the model works, the reader should read volume one first. Also presented in this volume is a set of realistic scenarios for buried sources of radon gas, and the input and output file structure for CASCADER9

Time-reversal focusing of an expanding soliton gas in disordered replicas

KAUST Repository

Fratalocchi, Andrea; Armaroli, A.; Trillo, S.

2011-01-01

We investigate the properties of time reversibility of a soliton gas, originating from a dispersive regularization of a shock wave, as it propagates in a strongly disordered environment. An original approach combining information measures and spin glass theory shows that time-reversal focusing occurs for different replicas of the disorder in forward and backward propagation, provided the disorder varies on a length scale much shorter than the width of the soliton constituents. The analysis is performed by starting from a new class of reflectionless potentials, which describe the most general form of an expanding soliton gas of the defocusing nonlinear Schrödinger equation.

Time-reversal focusing of an expanding soliton gas in disordered replicas

KAUST Repository

Fratalocchi, Andrea

2011-05-31

We investigate the properties of time reversibility of a soliton gas, originating from a dispersive regularization of a shock wave, as it propagates in a strongly disordered environment. An original approach combining information measures and spin glass theory shows that time-reversal focusing occurs for different replicas of the disorder in forward and backward propagation, provided the disorder varies on a length scale much shorter than the width of the soliton constituents. The analysis is performed by starting from a new class of reflectionless potentials, which describe the most general form of an expanding soliton gas of the defocusing nonlinear Schrödinger equation.

Measuring short distance dispersal of Alliaria petiolata and determining potential long distance dispersal mechanisms

Directory of Open Access Journals (Sweden)

Christopher A. Loebach

2018-03-01

Full Text Available Introduction Alliaria petiolata, an herbaceous plant, has invaded woodlands in North America. Its ecology has been thoroughly studied, but an overlooked aspect of its biology is seed dispersal distances and mechanisms. We measured seed dispersal distances in the field and tested if epizoochory is a potential mechanism for long-distance seed dispersal. Methods Dispersal distances were measured by placing seed traps in a sector design around three seed point sources, which consisted of 15 second-year plants transplanted within a 0.25 m radius circle. Traps were placed at intervals ranging from 0.25–3.25 m from the point source. Traps remained in the field until a majority of seeds were dispersed. Eight probability density functions were fitted to seed trap counts via maximum likelihood. Epizoochory was tested as a potential seed dispersal mechanism for A. petiolata through a combination of field and laboratory experiments. To test if small mammals transport A. petiolata seeds in their fur, experimental blocks were placed around dense A. petiolata patches. Each block contained a mammal inclusion treatment (MIT and control. The MIT consisted of a wood-frame (31 × 61× 31 cm covered in wire mesh, except for the two 31 × 31 cm ends, placed over a germination tray filled with potting soil. A pan filled with bait was placed in the center of the tray. The control frame (11 × 31 × 61 cm was placed over a germination tray and completely covered in wire mesh to exclude animal activity. Treatments were in the field for peak seed dispersal. In March, trays were moved to a greenhouse and A. petiolata seedlings were counted and then compared between treatments. To determine if A. petiolata seeds attach to raccoon (Procyon lotor and white-tailed deer (Odocoileus virginianus fur, wet and dry seeds were dropped onto wet and dry fur. Furs were rotated 180 degrees and the seeds that remained attached were counted. To measure seed retention, seeds

A Tale of Two Regions: Landscape Ecological Planning for Shale Gas Energy Futures

Science.gov (United States)

Murtha, T., Jr.; Schroth, O.; Orland, B.; Goldberg, L.; Mazurczyk, T.

2015-12-01

As we increasingly embrace deep shale gas deposits to meet global energy demands new and dispersed local and regional policy and planning challenges emerge. Even in regions with long histories of energy extraction, such as coal, shale gas and the infrastructure needed to produce the gas and transport it to market offers uniquely complex transformations in land use and landcover not previously experienced. These transformations are fast paced, dispersed and can overwhelm local and regional planning and regulatory processes. Coupled to these transformations is a structural confounding factor. While extraction and testing are carried out locally, regulation and decision-making is multilayered, often influenced by national and international factors. Using a geodesign framework, this paper applies a set of geospatial landscape ecological planning tools in two shale gas settings. First, we describe and detail a series of ongoing studies and tools that we have developed for communities in the Marcellus Shale region of the eastern United States, specifically the northern tier of Pennsylvania. Second, we apply a subset of these tools to potential gas development areas of the Fylde region in Lancashire, United Kingdom. For the past five years we have tested, applied and refined a set of place based and data driven geospatial models for forecasting, envisioning, analyzing and evaluating shale gas activities in northern Pennsylvania. These models are continuously compared to important landscape ecological planning challenges and priorities in the region, e.g. visual and cultural resource preservation. Adapting and applying these tools to a different landscape allow us to not only isolate and define important regulatory and policy exigencies in each specific setting, but also to develop and refine these models for broader application. As we continue to explore increasingly complex energy solutions globally, we need an equally complex comparative set of landscape ecological

Fundamentals of energy dispersive X-ray analysis

CERN Document Server

Russ, John C; Kiessling, R; Charles, J

1984-01-01

Fundamentals of Energy Dispersive X-ray Analysis provides an introduction to the fundamental principles of dispersive X-ray analysis. It presents descriptions, equations, and graphs to enable the users of these techniques to develop an intuitive and conceptual image of the physical processes involved in the generation and detection of X-rays. The book begins with a discussion of X-ray detection and measurement, which is accomplished by one of two types of X-ray spectrometer: energy dispersive or wavelength dispersive. The emphasis is on energy dispersive spectrometers, given their rather wid

The Physical Origin of Long Gas Depletion Times in Galaxies

Science.gov (United States)

Semenov, Vadim A.; Kravtsov, Andrey V.; Gnedin, Nickolay Y.

2017-08-01

We present a model that explains why galaxies form stars on a timescale significantly longer than the timescales of processes governing the evolution of interstellar gas. We show that gas evolves from a non-star-forming to a star-forming state on a relatively short timescale, and thus the rate of this evolution does not limit the star formation rate (SFR). Instead, the SFR is limited because only a small fraction of star-forming gas is converted into stars before star-forming regions are dispersed by feedback and dynamical processes. Thus, gas cycles into and out of a star-forming state multiple times, which results in a long timescale on which galaxies convert gas into stars. Our model does not rely on the assumption of equilibrium and can be used to interpret trends of depletion times with the properties of observed galaxies and the parameters of star formation and feedback recipes in simulations. In particular, the model explains how feedback self-regulates the SFR in simulations and makes it insensitive to the local star formation efficiency. We illustrate our model using the results of an isolated L *-sized galaxy simulation that reproduces the observed Kennicutt-Schmidt relation for both molecular and atomic gas. Interestingly, the relation for molecular gas is almost linear on kiloparsec scales, although a nonlinear relation is adopted in simulation cells. We discuss how a linear relation emerges from non-self-similar scaling of the gas density PDF with the average gas surface density.

The Physical Origin of Long Gas Depletion Times in Galaxies

International Nuclear Information System (INIS)

Semenov, Vadim A.; Kravtsov, Andrey V.; Gnedin, Nickolay Y.

2017-01-01

We present a model that explains why galaxies form stars on a timescale significantly longer than the timescales of processes governing the evolution of interstellar gas. We show that gas evolves from a non-star-forming to a star-forming state on a relatively short timescale, and thus the rate of this evolution does not limit the star formation rate (SFR). Instead, the SFR is limited because only a small fraction of star-forming gas is converted into stars before star-forming regions are dispersed by feedback and dynamical processes. Thus, gas cycles into and out of a star-forming state multiple times, which results in a long timescale on which galaxies convert gas into stars. Our model does not rely on the assumption of equilibrium and can be used to interpret trends of depletion times with the properties of observed galaxies and the parameters of star formation and feedback recipes in simulations. In particular, the model explains how feedback self-regulates the SFR in simulations and makes it insensitive to the local star formation efficiency. We illustrate our model using the results of an isolated L * -sized galaxy simulation that reproduces the observed Kennicutt–Schmidt relation for both molecular and atomic gas. Interestingly, the relation for molecular gas is almost linear on kiloparsec scales, although a nonlinear relation is adopted in simulation cells. We discuss how a linear relation emerges from non-self-similar scaling of the gas density PDF with the average gas surface density.

Dispersed-phase catalysis in coal liquefaction

International Nuclear Information System (INIS)

Utz, B.R.; Cugini, A.V.; Frommell, E.A.

1990-01-01

This paper reports that the specific reaction (activation) conditions for the conversion of catalyst precursors to unsupported catalyst have a direct effect on the catalytic activity and dispersion. The importance of reaction intermediates in decomposition of ammonium heptamolybdate and ammonium tetrathiomolybdate, and the sensitivity of these intermediates to reaction conditions, were studied in coal liquefaction systems. Recent results indicate that optimization of activation conditions facilitates the formation of a highly dispersed and active form of molybdenum disulfide for coal liquefaction. The use of the catalyst precursors ammonium heptamolybdate, ammonium tetrathiomolybdate, and molybdenum trisulfide for the conversion of coal to soluble products will be discussed. The use of an unsupported dispersed-phase catalyst for direct coal liquefaction is not a novel concept and has been employed in may studies with varying success. Dispersed-phase catalysts soluble and oil-soluble salts, and as finely divided powders. While some methods of catalyst introduction give higher dispersion of the catalyst and greater activity for the liquefaction of coal, all of the techniques allow the formation of a finely dispersed inorganic phase

Magnon dispersion in thin magnetic films

International Nuclear Information System (INIS)

Balashov, T; Wulfhekel, W; Buczek, P; Sandratskii, L; Ernst, A

2014-01-01

Although the dispersion of magnons has been measured in many bulk materials, few studies deal with the changes in the dispersion when the material is in the form of a thin film, a system that is of interest for applications. Here we review inelastic tunneling spectroscopy studies of magnon dispersion in Mn/Cu 3 Au(1 0 0) and present new studies on Co and Ni thin films on Cu(1 0 0). The dispersion in Mn and Co films closely follows the dispersion of bulk samples with negligible dependence on thickness. The lifetime of magnons depends slightly on film thickness, and decreases considerably as the magnon energy increases. In Ni/Cu(1 0 0) films the thickness dependence of dispersion is much more pronounced. The measurements indicate a considerable mode softening for thinner films. Magnon lifetimes decrease dramatically near the edge of the Brillouin zone due to a close proximity of the Stoner continuum. The experimental study is supported by first-principles calculations. (paper)

Magnon dispersion in thin magnetic films.

Science.gov (United States)

Balashov, T; Buczek, P; Sandratskii, L; Ernst, A; Wulfhekel, W

2014-10-01

Although the dispersion of magnons has been measured in many bulk materials, few studies deal with the changes in the dispersion when the material is in the form of a thin film, a system that is of interest for applications. Here we review inelastic tunneling spectroscopy studies of magnon dispersion in Mn/Cu3Au(1 0 0) and present new studies on Co and Ni thin films on Cu(1 0 0). The dispersion in Mn and Co films closely follows the dispersion of bulk samples with negligible dependence on thickness. The lifetime of magnons depends slightly on film thickness, and decreases considerably as the magnon energy increases. In Ni/Cu(1 0 0) films the thickness dependence of dispersion is much more pronounced. The measurements indicate a considerable mode softening for thinner films. Magnon lifetimes decrease dramatically near the edge of the Brillouin zone due to a close proximity of the Stoner continuum. The experimental study is supported by first-principles calculations.

Generalized dispersive wave emission in nonlinear fiber optics.

Science.gov (United States)

Webb, K E; Xu, Y Q; Erkintalo, M; Murdoch, S G

2013-01-15

We show that the emission of dispersive waves in nonlinear fiber optics is not limited to soliton-like pulses propagating in the anomalous dispersion regime. We demonstrate, both numerically and experimentally, that pulses propagating in the normal dispersion regime can excite resonant dispersive radiation across the zero-dispersion wavelength into the anomalous regime.

Dispersion Decay and Scattering Theory

CERN Document Server

Komech, Alexander

2012-01-01

A simplified, yet rigorous treatment of scattering theory methods and their applications Dispersion Decay and Scattering Theory provides thorough, easy-to-understand guidance on the application of scattering theory methods to modern problems in mathematics, quantum physics, and mathematical physics. Introducing spectral methods with applications to dispersion time-decay and scattering theory, this book presents, for the first time, the Agmon-Jensen-Kato spectral theory for the Schr?dinger equation, extending the theory to the Klein-Gordon equation. The dispersion decay plays a crucial role i

Delayed or No Feedback? Gas Outflows in Type 2 AGNs. III

Energy Technology Data Exchange (ETDEWEB)

Woo, Jong-Hak; Son, Donghoon; Bae, Hyun-Jin, E-mail: woo@astro.snu.ac.kr, E-mail: hjbae@galaxy.yonsei.ac.kr [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of)

2017-04-20

We present gas kinematics based on the [O iii] λ 5007 line and their connection to galaxy gravitational potential, active galactic nucleus (AGN) energetics, and star formation, using a large sample of ∼110,000 AGNs and star-forming (SF) galaxies at z < 0.3. Gas and stellar velocity dispersions are comparable to each other in SF galaxies, indicating that the ionized gas kinematics can be accounted by the gravitational potential of host galaxies. In contrast, AGNs clearly show non-gravitational kinematics, which is comparable to or stronger than the virial motion caused by the gravitational potential. The [O iii] velocity–velocity dispersion (VVD) diagram dramatically expands toward high values as a function of AGN luminosity, implying that the outflows are AGN-driven, while SF galaxies do not show such a trend. We find that the fraction of AGNs with a signature of outflow kinematics, steeply increases with AGN luminosity and Eddington ratio. In particular, the majority of luminous AGNs presents strong non-gravitational kinematics in the [O iii] profile. AGNs with strong outflow signatures show on average similar specific star formation rates (sSFRs) to those of star-forming galaxies. In contrast, AGNs with weak or no outflows have an order of magnitude lower sSFRs, suggesting that AGNs with current strong outflows do now show any negative AGN feedback and that it may take dynamical time to impact on star formation over galactic scales.

Improved new generation dispersants

International Nuclear Information System (INIS)

Anon.

1993-01-01

The use of dispersants to combat oil spills has attracted controversy over the years, and there has been a number of accusations of the chemicals involved doing more harm than good. A new study by the International Petroleum Industry Environmental Conservation Association discusses the positive and the negatives of dispersant use to be considered when drawing up spill contingency plans. (author)

Dispersal of forest insects

Science.gov (United States)

Mcmanus, M. L.

1979-01-01

Dispersal flights of selected species of forest insects which are associated with periodic outbreaks of pests that occur over large contiguous forested areas are discussed. Gypsy moths, spruce budworms, and forest tent caterpillars were studied for their massive migrations in forested areas. Results indicate that large dispersals into forested areas are due to the females, except in the case of the gypsy moth.

Interspecific nematode signals regulate dispersal behavior.

Directory of Open Access Journals (Sweden)

Fatma Kaplan

Full Text Available Dispersal is an important nematode behavior. Upon crowding or food depletion, the free living bacteriovorus nematode Caenorhabditis elegans produces stress resistant dispersal larvae, called dauer, which are analogous to second stage juveniles (J2 of plant parasitic Meloidogyne spp. and infective juveniles (IJs of entomopathogenic nematodes (EPN, e.g., Steinernema feltiae. Regulation of dispersal behavior has not been thoroughly investigated for C. elegans or any other nematode species. Based on the fact that ascarosides regulate entry in dauer stage as well as multiple behaviors in C. elegans adults including mating, avoidance and aggregation, we hypothesized that ascarosides might also be involved in regulation of dispersal behavior in C. elegans and for other nematodes such as IJ of phylogenetically related EPNs.Liquid chromatography-mass spectrometry analysis of C. elegans dauer conditioned media, which shows strong dispersing activity, revealed four known ascarosides (ascr#2, ascr#3, ascr#8, icas#9. A synthetic blend of these ascarosides at physiologically relevant concentrations dispersed C. elegans dauer in the presence of food and also caused dispersion of IJs of S. feltiae and J2s of plant parasitic Meloidogyne spp. Assay guided fractionation revealed structural analogs as major active components of the S. feltiae (ascr#9 and C. elegans (ascr#2 dispersal blends. Further analysis revealed ascr#9 in all Steinernema spp. and Heterorhabditis spp. infected insect host cadavers.Ascaroside blends represent evolutionarily conserved, fundamentally important communication systems for nematodes from diverse habitats, and thus may provide sustainable means for control of parasitic nematodes.

Physical simulation of gas reservoir formation in the Liwan 3-1 deep-water gas field in the Baiyun sag, Pearl River Mouth Basin

Directory of Open Access Journals (Sweden)

Gang Gao

2015-01-01

Full Text Available To figure out the process and controlling factors of gas reservoir formation in deep-waters, based on an analysis of geological features, source of natural gas and process of reservoir formation in the Liwan 3-1 gas field, physical simulation experiment of the gas reservoir formation process has been performed, consequently, pattern and features of gas reservoir formation in the Baiyun sag has been found out. The results of the experiment show that: ① the formation of the Liwan 3-1 faulted anticline gas field is closely related to the longstanding active large faults, where natural gas is composed of a high proportion of hydrocarbons, a small amount of non-hydrocarbons, and the wet gas generated during highly mature stage shows obvious vertical migration signs; ② liquid hydrocarbons associated with natural gas there are derived from source rock of the Enping & Zhuhai Formation, whereas natural gas comes mainly from source rock of the Enping Formation, and source rock of the Wenchang Formation made a little contribution during the early Eocene period as well; ③ although there was gas migration and accumulation, yet most of the natural gas mainly scattered and dispersed due to the stronger activity of faults in the early period; later as fault activity gradually weakened, gas started to accumulate into reservoirs in the Baiyun sag; ④ there is stronger vertical migration of oil and gas than lateral migration, and the places where fault links effective source rocks with reservoirs are most likely for gas accumulation; ⑤ effective temporal-spatial coupling of source-fault-reservoir in late stage is the key to gas reservoir formation in the Baiyun sag; ⑥ the nearer the distance from a trap to a large-scale fault and hydrocarbon source kitchen, the more likely gas may accumulate in the trap in late stage, therefore gas accumulation efficiency is much lower for the traps which are far away from large-scale faults and hydrocarbon source

Quantification of Single- and Multi-Phase Hydrodynamic Dispersion in Rocks Using Dynamic 3D PET Imaging

Science.gov (United States)

Pini, R.; Vandehey, N. T.; O'Neil, J.; Benson, S. M.

2015-12-01

We report results of an experimental investigation into the effects of small-scale (mm-cm) heterogeneities and hydrodynamic dispersion on miscible and immiscible displacements in a Berea Sandstone core. Pulse-radiotracer tests were carried out by measuring breakthrough curves at distinct flow rates and gas/water saturation ratios, while simultaneously imaging the internal displacement of the radioactive solution by [11C]PET. Dynamic multidimensional maps of the tracer concentration in the rock sample have been obtained with a spatial resolution of about 10 mm3 and provide evidence for significant macrodispersion effects caused by the presence of heterogeneities at the same scale. The numerical solution of the classic Advection-Dispersion Equation (ADE) applied in 1D form fails to describe the measured breakthrough curves and significantly overestimates longitudinal dispersivity. An excellent agreement with the experiments is attained by explicitly accounting for permeability heterogeneity, while reducing the contribution of "Fickian" dispersivity. Heterogeneity was introduced in the model by discretising the rock sample into independent parallel streamlines, which were generated based on a previously determined 3D permeability map, and by solving the 1D ADE for each of them. The use of streamlines is supported by direct quantitative observations from the PET scans; remarkably, this approach leads to an accurate representation of both the temporal behaviour and spatial distribution of the tracer concentration in the sample. It is shown that when the length-scale of permeability variations is similar in order as the size of the sample, the effect of the former can be as significant as hydrodynamic dispersion. The presence of a second immiscible fluid phase further complicates the flow field and, accordingly, the interpretation of the experiments. The ability to decouple these effects leads to the estimation of dispersion coefficients that aren't sample specific and

Sound Propagation in Gas-Vapor-Droplet Suspensions with Evaporation and Nonlinear Particle Relaxation

Science.gov (United States)

Kandula, Max

2012-01-01

The Sound attenuation and dispersion in saturated gas-vapor-droplet mixture in the presence of evaporation has been investigated theoretically. The theory is based on an extension of the work of Davidson to accommodate the effects of nonlinear particle relaxation processes of mass, momentum and energy transfer on sound attenuation and dispersion. The results indicate the existence of a spectral broadening effect in the attenuation coefficient (scaled with respect to the peak value) with a decrease in droplet mass concentration. It is further shown that for large values of the droplet concentration the scaled attenuation coefficient is characterized by a universal spectrum independent of droplet mass concentration.

Fabrication of High Gas Barrier Epoxy Nanocomposites: An Approach Based on Layered Silicate Functionalized by a Compatible and Reactive Modifier of Epoxy-Diamine Adduct

Directory of Open Access Journals (Sweden)

Ran Wei

2018-05-01

Full Text Available To solve the drawbacks of poor dispersion and weak interface in gas barrier nanocomposites, a novel epoxy-diamine adduct (DDA was synthesized by reacting epoxy monomer DGEBA with curing agent D400 to functionalize montmorillonite (MMT, which could provide complete compatibility and reactivity with a DGEBA/D400 epoxy matrix. Thereafter, sodium type montmorillonite (Na-MMT and organic-MMTs functionalized by DDA and polyether amines were incorporated with epoxy to manufacture nanocomposites. The effects of MMT functionalization on the morphology and gas barrier property of nanocomposites were evaluated. The results showed that DDA was successfully synthesized, terminating with epoxy and amine groups. By simulating the small-angle neutron scattering data with a sandwich structure model, the optimal dispersion/exfoliation of MMT was observed in a DDA-MMT/DGEBA nanocomposite with a mean radius of 751 Å, a layer thickness of 30.8 Å, and only two layers in each tactoid. Moreover, the DDA-MMT/DGEBA nanocomposite exhibited the best N2 barrier properties, which were about five times those of neat epoxy. Based on a modified Nielsen model, it was clarified that this excellent gas barrier property was due to the homogeneously dispersed lamellas with almost exfoliated structures. The improved morphology and barrier property confirmed the superiority of the adduct, which provides a general method for developing gas barrier nanocomposites.

Long-range interactions of excited He atoms with ground-state noble-gas atoms

KAUST Repository

Zhang, J.-Y.; Qian, Ying; Schwingenschlö gl, Udo; Yan, Z.-C.

2013-01-01

The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition

Characterization of volatile organic compounds emissions from municipal landfill and their dispersion in the environment; Caracterisation des emissions de composes organiques volatils issus des centre de stockage de dechets menagers et assimiles et de leur dispersion dans l'environnement

Energy Technology Data Exchange (ETDEWEB)

Chiriac, R.E.

2004-12-15

A municipal landfill causes atmospheric pollution by the emission of trace volatile organic compounds (VOCs) that are harmful for health and environment. Beyond the adsorption technique on sorbent tubes followed by solvent extraction and GC/MS analysis in the laboratory, a pre-concentrator-thermodesorption /micro-gas chromatograph coupling was developed for on-site monitoring of trace VOCs. To evaluate the environmental impact of this traces various studies were realized: 'Study of the emission of VOCs from landfill cells in use', 'Study of the formation of VOCs from a pilot-scale municipal landfill', 'Study of the dispersion of VOCs from a municipal landfill'. All the results permitted a closer appraisal of the emission and dispersion phenomena of VOCs from a municipal landfill. (author)

Dispersal of Engineered Male Aedes aegypti Mosquitoes.

Science.gov (United States)

Winskill, Peter; Carvalho, Danilo O; Capurro, Margareth L; Alphey, Luke; Donnelly, Christl A; McKemey, Andrew R

2015-11-01

Aedes aegypti, the principal vector of dengue fever, have been genetically engineered for use in a sterile insect control programme. To improve our understanding of the dispersal ecology of mosquitoes and to inform appropriate release strategies of 'genetically sterile' male Aedes aegypti detailed knowledge of the dispersal ability of the released insects is needed. The dispersal ability of released 'genetically sterile' male Aedes aegypti at a field site in Brazil has been estimated. Dispersal kernels embedded within a generalized linear model framework were used to analyse data collected from three large scale mark release recapture studies. The methodology has been applied to previously published dispersal data to compare the dispersal ability of 'genetically sterile' male Aedes aegypti in contrasting environments. We parameterised dispersal kernels and estimated the mean distance travelled for insects in Brazil: 52.8 m (95% CI: 49.9 m, 56.8 m) and Malaysia: 58.0 m (95% CI: 51.1 m, 71.0 m). Our results provide specific, detailed estimates of the dispersal characteristics of released 'genetically sterile' male Aedes aegypti in the field. The comparative analysis indicates that despite differing environments and recapture rates, key features of the insects' dispersal kernels are conserved across the two studies. The results can be used to inform both risk assessments and release programmes using 'genetically sterile' male Aedes aegypti.

Modelling and interpretation of gas detection using remote laser pointers.

Science.gov (United States)

Hodgkinson, J; van Well, B; Padgett, M; Pride, R D

2006-04-01

We have developed a quantitative model of the performance of laser pointer style gas leak detectors, which are based on remote detection of backscattered radiation. The model incorporates instrumental noise limits, the reflectivity of the target background surface and a mathematical description of gas leak dispersion in constant wind speed and turbulence conditions. We have investigated optimum instrument performance and limits of detection in simulated leak detection situations. We predict that the optimum height for instruments is at eye level or above, giving an operating range of 10 m or more for most background surfaces, in wind speeds of up to 2.5 ms(-1). For ground based leak sources, we find laser pointer measurements are dominated by gas concentrations over a short distance close to the target surface, making their readings intuitive to end users in most cases. This finding is consistent with the results of field trials.

THE SINS/zC-SINF SURVEY OF z {approx} 2GALAXY KINEMATICS: THE NATURE OF DISPERSION-DOMINATED GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Foerster Schreiber, Natascha M.; Buschkamp, Peter; Davies, Ric; Eisenhauer, Frank; Kurk, Jaron; Lutz, Dieter [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching (Germany); Shapiro Griffin, Kristen [Space Sciences Research Group, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Mancini, Chiara; Renzini, Alvio [Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, Padova I-35122 (Italy); Lilly, Simon J.; Carollo, C. Marcella; Peng, Yingjie [Institute of Astronomy, Department of Physics, Eidgenoessische Technische Hochschule, ETH Zuerich CH-8093 (Switzerland); Bouche, Nicolas [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France); Burkert, Andreas [Universitaets-Sternwarte Ludwig-Maximilians-Universitaet (USM), Scheinerstr. 1, Muenchen D-81679 (Germany); Cresci, Giovanni [Istituto Nazionale di Astrofisica Osservatorio Astronomico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hicks, Erin K. S. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Naab, Thorsten, E-mail: sfnewman@berkeley.edu [Max-Planck Institute for Astrophysics, Karl Schwarzschildstrasse 1, D-85748 Garching (Germany); and others

2013-04-20

We analyze the spectra, spatial distributions, and kinematics of H{alpha}, [N II], and [S II] emission in a sample of 38, z {approx} 2.2 UV/optically selected star-forming galaxies (SFGs) from the SINS and zC-SINF surveys, 34 of which were observed in the adaptive optics mode of SINFONI and 30 of those contain data presented for the first time here. This is supplemented by kinematic data from 43 z {approx} 1-2.5 galaxies from the literature. None of these 81 galaxies is an obvious major merger. We find that the kinematic classification of high-z SFGs as ''dispersion dominated'' or ''rotation dominated'' correlates most strongly with their intrinsic sizes. Smaller galaxies are more likely ''dispersion-dominated'' for two main reasons: (1) the rotation velocity scales linearly with galaxy size but intrinsic velocity dispersion does not depend on size or may even increase in smaller galaxies, and as such, their ratio is systematically lower for smaller galaxies, and (2) beam smearing strongly decreases large-scale velocity gradients and increases observed dispersion much more for galaxies with sizes at or below the resolution. Dispersion-dominated SFGs may thus have intrinsic properties similar to ''rotation-dominated'' SFGs, but are primarily more compact, lower mass, less metal enriched, and may have higher gas fractions, plausibly because they represent an earlier evolutionary state.

Confined zone dispersion flue gas desulfurization demonstration. Quarterly report No. 8, August 17, 1992--November 16, 1992

Energy Technology Data Exchange (ETDEWEB)

1993-09-27

The CZD process involves injecting a finely atomized slurry of reactive lime into the flue gas duct work of a coal-fired utility boiler. The principle of the confined zone is to form a wet zone of slurry droplets in the middle of the duct confined in an envelope of hot gas between the wet zone and the duct walls. The lime slurry reacts with part of the SO{sub 2} in the gas, and the reaction products dry to form solid particles. A solids collector, typically an electrostatic precipitator (ESP) downstream from the point of injection, captures the reaction products along with the fly ash entrained in the flue gas. The goal of this demonstration is to prove the technical and economic feasibility of the CZD technology on a commercial scale. The process is expected to achieve 50% SO{sub 2} removal at lower capital and O&M costs than other systems. To achieve its objectives, the project is divided into the following three phases: Phase 1: Design and Permitting, Phase 2: Construction and Start-up, Phase 3: Operation and Disposition. Phase 1 activities were completed on January 31, 1991. Phase 2 activities were essentially concluded on July 31, 1991, and Phase 3a, Parametric Testing, was initiated on July 1, 1991. This Quarterly Technical Progress Report covers Phase 3b activities from August 17, 1992 through November 16, 1992.

On the accuracy of DFT methods in reproducing ligand substitution energies for transition metal complexes in solution: The role of dispersive interactions

KAUST Repository

Jacobsen, Heiko

2011-12-23

The performance of a series of density functionals when tested on the prediction of the phosphane substitution energy of transition metal complexes is evaluated. The complexes Fe-BDA and Ru-COD (BDA=benzylideneacetone, COD=cyclooctadiene) serve as reference systems, and calculated values are compared with the experimental values in THF as obtained from calorimetry. Results clearly indicate that functionals specifically developed to include dispersion interactions usually outperform other functionals when BDA or COD substitution is considered. However, when phosphanes of different sizes are compared, functionals including dispersion interactions, at odd with experimental evidence, predict that larger phosphanes bind more strongly than smaller phosphanes, while functionals not including dispersion interaction reproduce the experimental trends with reasonable accuracy. In case of the DFT-D functionals, inclusion of a cut-off distance on the dispersive term resolves this issue, and results in a rather robust behavior whatever ligand substitution reaction is considered. Ne quid nimis: Describing chemical reactions in solution by computational techniques developed for gas-phase scenarios might produce erroneous results (see histogram). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dispersant effectiveness: Studies into the causes of effectiveness variations

International Nuclear Information System (INIS)

Fingas, M.F.; Kyle, D.; Tennyson, E.

1995-01-01

Effectiveness, a key issue of using dispersants, is affected by many interrelated factors. The principal factors involved are the oil composition, dispersant formulation, sea surface turbulence and dispersant quantity. Oil composition is a very strong determinant. Current dispersant formulation effectiveness correlates strongly with the amount of saturate component in the oil. The other components of the oil, the asphaltenes, resins or polars and aromatic fractions show a negative correlation with the dispersant effectiveness. Viscosity is also a predictor of dispersant effectiveness and may have an effect because it is in turn determined by oil composition. Dispersant composition is significant and interacts with oil composition. Dispersants show high effectiveness at HLB values near 10. Sea turbulence strongly affects dispersant effectiveness.Effectiveness rises with increasing turbulence to a maximum value. Effectiveness for current commercial dispersants is gaussian around a peak salinity value. Peak effectiveness is achieved at very high dispersant quantities--at a ratio of 1:5, dispersant-to-oil volume. Dispersant effectiveness for those oils tested and under the conditions measured, is approximately logarithmic with dispersant quantity and will reach about 50% of its peak value at a dispersant to oil ratio of about 1:20 and near zero at a ratio of about 1:50

Dispersion properties of photonic crystal fibres

DEFF Research Database (Denmark)

Bjarklev, Anders Overgaard; Broeng, Jes; Dridi, Kim

1998-01-01

Approximate dispersion and bending properties of all-silica two-dimensional photonic crystal fibres are characterised by the combination of an effective-index model and classical analysis tools for optical fibres. We believe for the first time to have predicted the dispersion properties of photonic...... crystal fibres. The results strongly indicate that these fibres have potential applications as dispersion managing components...

Dispersion-engineered and highly-nonlinear microstructured polymer optical fibres

DEFF Research Database (Denmark)

Frosz, Michael Henoch; Nielsen, Kristian; Hlubina, Petr

2009-01-01

We demonstrate dispersion-engineering of microstructured polymer optical fibres (mPOFs) made of poly(methyl methacrylate) (PMMA). A significant shift of the total dispersion from the material dispersion is confirmed through measurement of the mPOF dispersion using white-light spectral interferome......We demonstrate dispersion-engineering of microstructured polymer optical fibres (mPOFs) made of poly(methyl methacrylate) (PMMA). A significant shift of the total dispersion from the material dispersion is confirmed through measurement of the mPOF dispersion using white-light spectral...

Quantification of free and total bisphenol A and bisphenol B in human urine by dispersive liquid-liquid microextraction (DLLME) and heart-cutting multidimensional gas chromatography-mass spectrometry (MD-GC/MS).

Science.gov (United States)

Cunha, S C; Fernandes, J O

2010-11-15

A novel method combining dispersive liquid-liquid microextraction (DLLME) and heart-cutting multidimensional gas chromatography coupled to mass spectrometry was developed for the determination of free and total bisphenol A (BPA) and bisphenol B (BPB) in human urine samples. The DLLME procedure combines extraction, derivatization and concentration of the analytes into one step. Several important variables influencing the extraction efficiency and selectivity such as nature and volume of extractive and dispersive solvents as well as the amount of acetylating reagent were investigated. The temperature and time to hydrolyze BPA and BPB conjugates with a β-glucuronidase and sulfatase enzyme preparation were also studied. Under the optimized conditions good efficiency extraction (71-93%) and acceptable total DLLME yields (56-77%) were obtained for both analytes. Matrix-matched calibration curves were linear with correlation coefficients higher than 0.996 in the range level 0.1-5 μg/l, and the relative standard deviations (%RSD) were lower than 20% (n=6). The limits of detection were 0.03 and 0.05 μg/l for BPA and BPB, respectively. The applicability of the proposed method for determining urinary free and total BPA and BPB was assessed by analyzing the human urine of a group of 20 volunteers. Free BPA was detected in 45% of the sample whereas total BPA was detected in 85% of the samples at concentrations ranging between 0.39 and 4.99 μg/l. BPB was detected in conjugated form in two samples. Copyright © 2010 Elsevier B.V. All rights reserved.

The physiological effects of oil, dispersant and dispersed oil on the bay mussel, Mytilus trossulus, in Arctic/Subarctic conditions.