WorldWideScience

Sample records for modeling excess gas

  1. Molecular simulation of excess isotherm and excess enthalpy change in gas-phase adsorption.

    Science.gov (United States)

    Do, D D; Do, H D; Nicholson, D

    2009-01-29

    We present a new approach to calculating excess isotherm and differential enthalpy of adsorption on surfaces or in confined spaces by the Monte Carlo molecular simulation method. The approach is very general and, most importantly, is unambiguous in its application to any configuration of solid structure (crystalline, graphite layer or disordered porous glass), to any type of fluid (simple or complex molecule), and to any operating conditions (subcritical or supercritical). The behavior of the adsorbed phase is studied using the partial molar energy of the simulation box. However, to characterize adsorption for comparison with experimental data, the isotherm is best described by the excess amount, and the enthalpy of adsorption is defined as the change in the total enthalpy of the simulation box with the change in the excess amount, keeping the total number (gas + adsorbed phases) constant. The excess quantities (capacity and energy) require a choice of a reference gaseous phase, which is defined as the adsorptive gas phase occupying the accessible volume and having a density equal to the bulk gas density. The accessible volume is defined as the mean volume space accessible to the center of mass of the adsorbate under consideration. With this choice, the excess isotherm passes through a maximum but always remains positive. This is in stark contrast to the literature where helium void volume is used (which is always greater than the accessible volume) and the resulting excess can be negative. Our definition of enthalpy change is equivalent to the difference between the partial molar enthalpy of the gas phase and the partial molar enthalpy of the adsorbed phase. There is no need to assume ideal gas or negligible molar volume of the adsorbed phase as is traditionally done in the literature. We illustrate this new approach with adsorption of argon, nitrogen, and carbon dioxide under subcritical and supercritical conditions.

  2. Kinetic model of excess activated sludge thermohydrolysis.

    Science.gov (United States)

    Imbierowicz, Mirosław; Chacuk, Andrzej

    2012-11-01

    Thermal hydrolysis of excess activated sludge suspensions was carried at temperatures ranging from 423 K to 523 K and under pressure 0.2-4.0 MPa. Changes of total organic carbon (TOC) concentration in a solid and liquid phase were measured during these studies. At the temperature 423 K, after 2 h of the process, TOC concentration in the reaction mixture decreased by 15-18% of the initial value. At 473 K total organic carbon removal from activated sludge suspension increased to 30%. It was also found that the solubilisation of particulate organic matter strongly depended on the process temperature. At 423 K the transfer of TOC from solid particles into liquid phase after 1 h of the process reached 25% of the initial value, however, at the temperature of 523 K the conversion degree of 'solid' TOC attained 50% just after 15 min of the process. In the article a lumped kinetic model of the process of activated sludge thermohydrolysis has been proposed. It was assumed that during heating of the activated sludge suspension to a temperature in the range of 423-523 K two parallel reactions occurred. One, connected with thermal destruction of activated sludge particles, caused solubilisation of organic carbon and an increase of dissolved organic carbon concentration in the liquid phase (hydrolysate). The parallel reaction led to a new kind of unsolvable solid phase, which was further decomposed into gaseous products (CO(2)). The collected experimental data were used to identify unknown parameters of the model, i.e. activation energies and pre-exponential factors of elementary reactions. The mathematical model of activated sludge thermohydrolysis appropriately describes the kinetics of reactions occurring in the studied system. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. ATLAS Z Excess in Minimal Supersymmetric Standard Model

    International Nuclear Information System (INIS)

    Lu, Xiaochuan; Terada, Takahiro

    2015-06-01

    Recently the ATLAS collaboration reported a 3 sigma excess in the search for the events containing a dilepton pair from a Z boson and large missing transverse energy. Although the excess is not sufficiently significant yet, it is quite tempting to explain this excess by a well-motivated model beyond the standard model. In this paper we study a possibility of the minimal supersymmetric standard model (MSSM) for this excess. Especially, we focus on the MSSM spectrum where the sfermions are heavier than the gauginos and Higgsinos. We show that the excess can be explained by the reasonable MSSM mass spectrum.

  4. Variation in excess oxidant factor in combustion products of MHD generator. [Natural gas fuel

    Energy Technology Data Exchange (ETDEWEB)

    Pinkhasik, M S; Mironov, V D; Zakharko, Yu A; Plavinskii, A I

    1977-12-01

    Methods and difficulties associated with determining the excess oxidant factor for natural gas-fired MHD generators are discussed. The measurement of this factor is noted to be essential for the optimization of the combustion chamber and operation of MHD generators. A gas analyzer of electrochemical type is considered as a quick - response sensor capable of analyzing the composition of the combustion products and thus determining accurately the excess oxidant factor. The principle of operation of this sensor is discussed and the dependence of the electrochemical sensor emf on excess oxidant factor is shown. Three types of sensors are illustrated and tables of test results are provided.

  5. A model for the LHC diboson excess

    Energy Technology Data Exchange (ETDEWEB)

    Buen-Abad, Manuel; Cohen, Andrew G.; Schmaltz, Martin [Physics Department, Boston University,Boston, MA 02215 (United States)

    2016-05-18

    The first run of the LHC showed hints of a new resonance with mass near 1.9 TeV decaying into electroweak gauge boson pairs as well as into dijets. While Run 2 has neither confirmed nor ruled out such a resonance, it has yielded new constraints on models attempting to explain these decays. Additionally in W{sup ′} models where this new resonance is a charged vector boson that is a weak isospin singlet there is the potential for conflict with the electroweak precision T parameter. We construct variants of a W{sup ′} resonance model that provide an excellent fit to both Run 1 and Run 2 data, as well as electroweak precision measurements. The model also predicts a neutral vector boson, a Z{sup ′}, with mass close to 3 TeV. This Z{sup ′} is compatible with the intriguing Run 2 observation of a dielectron pair with invariant mass of 2.9 TeV at CMS.

  6. H_2 production by the steam reforming of excess boil off gas on LNG vessels

    International Nuclear Information System (INIS)

    Fernández, Ignacio Arias; Gómez, Manuel Romero; Gómez, Javier Romero; López-González, Luis M.

    2017-01-01

    Highlights: • BOG excess in LNG vessels is burned in the GCU without energy use. • The gas management plants need to be improved to increase efficiency. • BOG excess in LNG vessels is used for H_2 production by steam reforming. • The availability of different fuels increases the versatility of the ship. - Abstract: The gas management system onboard LNG (Liquid Natural Gas) vessels is crucial, since the exploitation of the BOG (Boil Off Gas) produced is of utmost importance for the overall efficiency of the plant. At present, LNG ships with no reliquefaction plant consume the BOG generated in the engines, and the excess is burned in the GCU (Gas Combustion Unit) without any energy use. The need to improve the gas management system, therefore, is evident. This paper proposes hydrogen production through a steam reforming plant, using the excess BOG as raw material and thus avoiding it being burned in the GCU. To test the feasibility of integrating the plant, an actual study of the gas management process on an LNG vessel with 4SDF (4 Stroke Dual Fuel) propulsion and with no reliquefaction plant was conducted, along with a thermodynamic simulation of the reforming plant. With the proposed gas management system, the vessel disposes of different fuels, including H_2, a clean fuel with zero ozone-depleting emissions. The availability of H_2 on board in areas with strict anti-pollution regulations, such as ECAs (Emission Control Area), means that the vessel may be navigated without using fossil fuels which generate CO_2 and SO_X emissions. Moreover, while at port, Cold Ironing is avoided, which entails high costs. Thus it is demonstrated that the installation of a reforming plant is both energetically viable and provides greater versatility to the ship.

  7. Asymmetric Dark Matter Models and the LHC Diphoton Excess

    DEFF Research Database (Denmark)

    Frandsen, Mads T.; Shoemaker, Ian M.

    2016-01-01

    The existence of dark matter (DM) and the origin of the baryon asymmetry are persistent indications that the SM is incomplete. More recently, the ATLAS and CMS experiments have observed an excess of diphoton events with invariant mass of about 750 GeV. One interpretation of this excess is decays...... have for models of asymmetric DM that attempt to account for the similarity of the dark and visible matter abundances....

  8. Integration of multiple, excess, backup, and expected covering models

    OpenAIRE

    M S Daskin; K Hogan; C ReVelle

    1988-01-01

    The concepts of multiple, excess, backup, and expected coverage are defined. Model formulations using these constructs are reviewed and contrasted to illustrate the relationships between them. Several new formulations are presented as is a new derivation of the expected covering model which indicates more clearly the relationship of the model to other multi-state covering models. An expected covering model with multiple time standards is also presented.

  9. Calculating excess lifetime risk in relative risk models

    International Nuclear Information System (INIS)

    Vaeth, M.; Pierce, D.A.

    1990-01-01

    When assessing the impact of radiation exposure it is common practice to present the final conclusions in terms of excess lifetime cancer risk in a population exposed to a given dose. The present investigation is mainly a methodological study focusing on some of the major issues and uncertainties involved in calculating such excess lifetime risks and related risk projection methods. The age-constant relative risk model used in the recent analyses of the cancer mortality that was observed in the follow-up of the cohort of A-bomb survivors in Hiroshima and Nagasaki is used to describe the effect of the exposure on the cancer mortality. In this type of model the excess relative risk is constant in age-at-risk, but depends on the age-at-exposure. Calculation of excess lifetime risks usually requires rather complicated life-table computations. In this paper we propose a simple approximation to the excess lifetime risk; the validity of the approximation for low levels of exposure is justified empirically as well as theoretically. This approximation provides important guidance in understanding the influence of the various factors involved in risk projections. Among the further topics considered are the influence of a latent period, the additional problems involved in calculations of site-specific excess lifetime cancer risks, the consequences of a leveling off or a plateau in the excess relative risk, and the uncertainties involved in transferring results from one population to another. The main part of this study relates to the situation with a single, instantaneous exposure, but a brief discussion is also given of the problem with a continuous exposure at a low-dose rate

  10. Gamma-ray excess and the minimal dark matter model

    International Nuclear Information System (INIS)

    Duerr, Michael; Fileviez Perez, Pavel; Smirnov, Juri

    2015-10-01

    We point out that the gamma-ray excesses in the galactic center and in the dwarf galaxy Reticulum II can both be well explained within the simplest dark matter model. We find that the corresponding region of parameter space will be tested by direct and indirect dark matter searches in the near future.

  11. Analytical expressions for transition edge sensor excess noise models

    International Nuclear Information System (INIS)

    Brandt, Daniel; Fraser, George W.

    2010-01-01

    Transition edge sensors (TESs) are high-sensitivity thermometers used in cryogenic microcalorimeters which exploit the steep gradient in resistivity with temperature during the superconducting phase transition. Practical TES devices tend to exhibit a white noise of uncertain origin, arising inside the device. We discuss two candidate models for this excess noise, phase slip shot noise (PSSN) and percolation noise. We extend the existing PSSN model to include a magnetic field dependence and derive a basic analytical model for percolation noise. We compare the predicted functional forms of the noise current vs. resistivity curves of both models with experimental data and provide a set of equations for both models to facilitate future experimental efforts to clearly identify the source of excess noise.

  12. ATLAS diboson excesses from the stealth doublet model

    Directory of Open Access Journals (Sweden)

    Wei Chao

    2016-02-01

    Full Text Available The ATLAS Collaboration has reported excesses in diboson invariant mass searches of new resonances around 2 TeV, which might be a prediction of new physics around that mass range. We interpret these results in the context of a modified stealth doublet model where the extra Higgs doublet has a Yukawa interaction with the first generation quarks, and show that the heavy CP-even Higgs boson can naturally explain the excesses in the WW and ZZ channels with a small Yukawa coupling, ξ∼0.15, and a tiny mixing angle with the SM Higgs boson, α∼0.05. Furthermore, the model satisfies constraints from colliders and electroweak precision measurements.

  13. Verification for excess reactivity on beginning equilibrium core of RSG GAS

    International Nuclear Information System (INIS)

    Daddy Setyawan; Budi Rohman

    2011-01-01

    BAPETEN is an institution authorized to control the use of nuclear energy in Indonesia. Control for the use of nuclear energy is carried out through three pillars: regulation, licensing, and inspection. In order to assure the safety of the operating research reactors, the assessment unit of BAPETEN is carrying out independent assessment in order to verify safety related parameters in the SAR including neutronic aspect. The work includes verification to the Power Peaking Factor in the equilibrium silicide core of RSG GAS reactor by computational method using MCNP-ORIGEN. This verification calculation results for is 9.4 %. Meanwhile, the RSG-GAS safety analysis report shows that the excess reactivity on equilibrium core of RSG GAS is 9.7 %. The verification calculation results show a good agreement with the report. (author)

  14. Constrained convex minimization via model-based excessive gap

    OpenAIRE

    Tran Dinh, Quoc; Cevher, Volkan

    2014-01-01

    We introduce a model-based excessive gap technique to analyze first-order primal- dual methods for constrained convex minimization. As a result, we construct new primal-dual methods with optimal convergence rates on the objective residual and the primal feasibility gap of their iterates separately. Through a dual smoothing and prox-function selection strategy, our framework subsumes the augmented Lagrangian, and alternating methods as special cases, where our rates apply.

  15. The di-photon excess in a perturbative SUSY model

    Energy Technology Data Exchange (ETDEWEB)

    Benakli, Karim, E-mail: kbenakli@lpthe.jussieu.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 7589, LPTHE, F-75005, Paris (France); CNRS, UMR 7589, LPTHE, F-75005, Paris (France); Darmé, Luc, E-mail: darme@lpthe.jussieu.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 7589, LPTHE, F-75005, Paris (France); CNRS, UMR 7589, LPTHE, F-75005, Paris (France); Sorbonne Universités, Institut Lagrange de Paris (ILP), 98 bis Boulevard Arago, 75014 Paris (France); Goodsell, Mark D., E-mail: goodsell@lpthe.jussieu.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 7589, LPTHE, F-75005, Paris (France); CNRS, UMR 7589, LPTHE, F-75005, Paris (France); Harz, Julia, E-mail: jharz@lpthe.jussieu.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 7589, LPTHE, F-75005, Paris (France); CNRS, UMR 7589, LPTHE, F-75005, Paris (France); Sorbonne Universités, Institut Lagrange de Paris (ILP), 98 bis Boulevard Arago, 75014 Paris (France)

    2016-10-15

    We show that a 750 GeV di-photon excess as reported by the ATLAS and CMS experiments can be reproduced by the Minimal Dirac Gaugino Supersymmetric Standard Model (MDGSSM) without the need of any ad-hoc addition of new states. The scalar resonance is identified with the spin-0 partner of the Dirac bino. We perform a thorough analysis of constraints coming from the mixing of the scalar with the Higgs boson, the stability of the vacuum and the requirement of perturbativity of the couplings up to very high energy scales. We exhibit examples of regions of the parameter space that respect all the constraints while reproducing the excess. We point out how trilinear couplings that are expected to arise in supersymmetry-breaking mediation scenarios, but were ignored in the previous literature on the subject, play an important role.

  16. A fission gas release model

    Energy Technology Data Exchange (ETDEWEB)

    Denis, A; Piotrkowski, R [Argentine Atomic Energy Commission, Buenos Aires (Argentina)

    1997-08-01

    The hypothesis contained in the model developed in this work are as follows. The UO{sub 2} is considered as a collection of spherical grains. Nuclear reactions produce fission gases, mainly Xe and Kr, within the grains. Due to the very low solubility of these gases in UO{sub 2}, intragranular bubbles are formed, of a few nanometers is size. The bubbles are assumed to be immobile and to act as traps which capture gas atoms. Free atoms diffuse towards the grain boundaries, where they give origin to intergranular, lenticular bubbles, of the order of microns. The gas atoms in bubbles, either inter or intragranular, can re-enter the matrix through the mechanism of resolution induced by fission fragment impact. The amount of gas stored in intergranular bubbles grows up to a saturation value. Once saturation is reached, intergranular bubbles inter-connect and the gas in excess is released through different channels to the external surface of the fuel. The resolution of intergranular bubbles particularly affects the region of the grain adjacent to the grain boundary. During grain growth, the grain boundary traps the gas atoms, either free or in intragranular bubbles, contained in the swept volume. The grain boundary is considered as a perfect sink, i.e. the gas concentration is zero at that surface of the grain. Due to the spherical symmetry of the problem, the concentration gradient is null at the centre of the grain. The diffusion equation was solved using the implicit finite difference method. The initial solution was analytically obtained by the Laplace transform. The calculations were performed at different constant temperatures and were compared with experimental results. They show the asymptotic growth of the grain radius as a function of burnup, the gas distribution within the grain at every instant, the growth of the gas content at the grain boundary up to the saturation value and the fraction of gas released by the fuel element referred to the total gas generated

  17. Background model systematics for the Fermi GeV excess

    Energy Technology Data Exchange (ETDEWEB)

    Calore, Francesca; Cholis, Ilias; Weniger, Christoph

    2015-03-01

    The possible gamma-ray excess in the inner Galaxy and the Galactic center (GC) suggested by Fermi-LAT observations has triggered a large number of studies. It has been interpreted as a variety of different phenomena such as a signal from WIMP dark matter annihilation, gamma-ray emission from a population of millisecond pulsars, or emission from cosmic rays injected in a sequence of burst-like events or continuously at the GC. We present the first comprehensive study of model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy and their impact on the inferred properties of the excess emission at Galactic latitudes 2° < |b| < 20° and 300 MeV to 500 GeV. We study both theoretical and empirical model systematics, which we deduce from a large range of Galactic diffuse emission models and a principal component analysis of residuals in numerous test regions along the Galactic plane. We show that the hypothesis of an extended spherical excess emission with a uniform energy spectrum is compatible with the Fermi-LAT data in our region of interest at 95% CL. Assuming that this excess is the extended counterpart of the one seen in the inner few degrees of the Galaxy, we derive a lower limit of 10.0° (95% CL) on its extension away from the GC. We show that, in light of the large correlated uncertainties that affect the subtraction of the Galactic diffuse emission in the relevant regions, the energy spectrum of the excess is equally compatible with both a simple broken power-law of break energy E(break) = 2.1 ± 0.2 GeV, and with spectra predicted by the self-annihilation of dark matter, implying in the case of bar bb final states a dark matter mass of m(χ)=49(+6.4)(-)(5.4)  GeV.

  18. Methodology to determine the appropriate amount of excess air for the operation of a gas turbine in a wet environment

    Energy Technology Data Exchange (ETDEWEB)

    Lugo-Leyte, R.; Zamora-Mata, J.M.; Torres-Aldaco, A. [Universidad Autonoma Metropolitana-Iztapalapa, Departamento de Ingenieria de Procesos e Hidraulica, San Rafael Atlixco 186, Col Vicentina 09340, Iztapalapa, Mexico, D.F. (Mexico); Toledo-Velazquez, M. [Instituto Politecnico Nacional, Escuela Superior de Ingenieria Mecanica y Electrica, Seccion de Estudios de Posgrado e Investigacion, Laboratorio de Ingenieria Termica e Hidraulica Aplicada, Unidad Profesional Adolfo Lopez Mateos, Edificio 5, 3er piso SEPI-ESIME, C.P. 07738, Col. Lindavista, Mexico D.F. (Mexico); Salazar-Pereyra, M. [Tecnologico de Estudios Superiores de Ecatepec, Division de Ingenieria Mecatronica e Industrial, Posgrado en Ciencias en Ingenieria Mecatronica, Av. Tecnologico s/n, Col. Valle de Anahuac, C.P. 55210, Ecatepec de Morelos, Estado de Mexico (Mexico)

    2010-02-15

    This paper addresses the impact of excess air on turbine inlet temperature, power, and thermal efficiency at different pressure ratios. An explicit relationship is developed to determine the turbine inlet temperature as a function of excess air, pressure ratio and relative humidity. The effect of humidity on the calculation of excess air to achieve a pre-established power output is analyzed and presented. Likewise it is demonstrated that dry air calculations provide a valid upper bound for the performance of a gas turbine under a wet environment. (author)

  19. Modelling of excess noise attnuation by grass and forest | Onuu ...

    African Journals Online (AJOL)

    , guinea grass (panicum maximum) and forest which comprises iroko (milicia ezcelea) and white afara (terminalia superba) trees in the ratio of 2:1 approximately. Excess noise attenuation spectra have been plotted for the grass and forest for ...

  20. An extended rational thermodynamics model for surface excess fluxes

    NARCIS (Netherlands)

    Sagis, L.M.C.

    2012-01-01

    In this paper, we derive constitutive equations for the surface excess fluxes in multiphase systems, in the context of an extended rational thermodynamics formalism. This formalism allows us to derive Maxwell–Cattaneo type constitutive laws for the surface extra stress tensor, the surface thermal

  1. THERMODYNAMIC MODEL OF GAS HYDRATES

    OpenAIRE

    Недоступ, В. И.; Недоступ, О. В.

    2015-01-01

    The interest to gas hydrates grows last years. Therefore working out of reliable settlement-theoretical methods of definition of their properties is necessary. The thermodynamic model of gas hydrates in which the central place occupies a behaviour of guest molecule in cell is described. The equations of interaction of molecule hydrate formative gas with cell are received, and also an enthalpy and energy of output of molecule from a cell are determined. The equation for calculation of thermody...

  2. Decision model for evaluating reactor disposition of excess plutonium

    International Nuclear Information System (INIS)

    Edmunds, T.

    1995-02-01

    The US Department of Energy is currently considering a range of technologies for disposition of excess weapon plutonium. Use of plutonium fuel in fission reactors to generate spent fuel is one class of technology options. This report describes the inputs and results of decision analyses conducted to evaluate four evolutionary/advanced and three existing fission reactor designs for plutonium disposition. The evaluation incorporates multiple objectives or decision criteria, and accounts for uncertainty. The purpose of the study is to identify important and discriminating decision criteria, and to identify combinations of value judgments and assumptions that tend to favor one reactor design over another

  3. Modelling isothermal fission gas release

    International Nuclear Information System (INIS)

    Uffelen, P. van

    2002-01-01

    The present paper presents a new fission gas release model consisting of two coupled modules. The first module treats the behaviour of the fission gas atoms in spherical grains with a distribution of grain sizes. This module considers single atom diffusion, trapping and fission induced re-solution of gas atoms associated with intragranular bubbles, and re-solution from the grain boundary into a few layers adjacent to the grain face. The second module considers the transport of the fission gas atoms along the grain boundaries. Four mechanisms are incorporated: diffusion controlled precipitation of gas atoms into bubbles, grain boundary bubble sweeping, re-solution of gas atoms into the adjacent grains and gas flow through open porosity when grain boundary bubbles are interconnected. The interconnection of the intergranular bubbles is affected both by the fraction of the grain face occupied by the cavities and by the balance between the bubble internal pressure and the hydrostatic pressure surrounding the bubbles. The model is under validation. In a first step, some numerical routines have been tested by means of analytic solutions. In a second step, the fission gas release model has been coupled with the FTEMP2 code of the Halden Reactor Project for the temperature distribution in the pellets. A parametric study of some steady-state irradiations and one power ramp have been simulated successfully. In particular, the Halden threshold for fission gas release and two simplified FUMEX cases have been computed and are summarised. (author)

  4. Overconsumption of Energy and Excessive Discretionary Food Intake Inflates Dietary Greenhouse Gas Emissions in Australia.

    Science.gov (United States)

    Hendrie, Gilly A; Baird, Danielle; Ridoutt, Brad; Hadjikakou, Michalis; Noakes, Manny

    2016-10-31

    Population dietary guidelines have started to include information about the environmental impacts of food choices, but more quantifiable evidence is needed, particularly about the impacts associated with discretionary foods. This paper utilised the 2011-2012 Australian Health Survey food intake data along with a highly disaggregated input-output model to estimate the greenhouse gas emissions (GHGe) of Australians' dietary intake, and compare current patterns of eating which vary in diet quality and GHGe to the recommended diet. The average dietary GHGe were 18.72 ± 12.06 and 13.73 ± 8.72 kg CO₂e/day for male and female adults, respectively. The correlation between total energy and GHGe was r = 0.54 ( p nutritional benefit at little environmental expense. Public health messages that promote healthy eating, eating to one's energy needs and improved diet quality will also contribute to lowering GHGe.

  5. DUST AND GAS IN THE MAGELLANIC CLOUDS FROM THE HERITAGE HERSCHEL KEY PROJECT. I. DUST PROPERTIES AND INSIGHTS INTO THE ORIGIN OF THE SUBMILLIMETER EXCESS EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, Karl D.; Roman-Duval, Julia; Meixner, Margaret [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bot, Caroline [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l Université, F-67000 Strasbourg (France); Babler, Brian [Department of Astronomy, 475 North Charter Street, University of Wisconsin, Madison, WI 53706 (United States); Bernard, Jean-Philippe [CESR, Université de Toulouse, UPS, 9 Avenue du Colonel Roche, F-31028 Toulouse, Cedex 4 (France); Bolatto, Alberto; Jameson, Katherine [Department of Astronomy, Lab for Millimeter-wave Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Boyer, Martha L. [Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Clayton, Geoffrey C. [Department of Physics and Astronomy, Louisiana State University, 233-A Nicholson Hall, Tower Drive, Baton Rouge, LA 70803 (United States); Engelbracht, Charles [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Fukui, Yasuo [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan); Galametz, Maud [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching-bei-Mnchen (Germany); Galliano, Frederic; Hony, Sacha; Lebouteiller, Vianney [CEA, Laboratoire AIM, Irfu/SAp, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Hughes, Annie [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Indebetouw, Remy [Department of Astronomy, University of Virginia, and National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Israel, Frank P. [Sterrewacht Leiden, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Kawamura, Akiko [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo, 181-8588 (Japan); and others

    2014-12-20

    The dust properties in the Large and Small Magellanic clouds (LMC/SMC) are studied using the HERITAGE Herschel Key Project photometric data in five bands from 100 to 500 μm. Three simple models of dust emission were fit to the observations: a single temperature blackbody modified by a power-law emissivity (SMBB), a single temperature blackbody modified by a broken power-law emissivity (BEMBB), and two blackbodies with different temperatures, both modified by the same power-law emissivity (TTMBB). Using these models, we investigate the origin of the submillimeter excess, defined as the submillimeter emission above that expected from SMBB models fit to observations <200 μm. We find that the BEMBB model produces the lowest fit residuals with pixel-averaged 500 μm submillimeter excesses of 27% and 43% for the LMC and SMC, respectively. Adopting gas masses from previous works, the gas-to-dust ratios calculated from our fitting results show that the TTMBB fits require significantly more dust than are available even if all the metals present in the interstellar medium (ISM) were condensed into dust. This indicates that the submillimeter excess is more likely to be due to emissivity variations than a second population of colder dust. We derive integrated dust masses of (7.3 ± 1.7) × 10{sup 5} and (8.3 ± 2.1) × 10{sup 4} M {sub ☉} for the LMC and SMC, respectively. We find significant correlations between the submillimeter excess and other dust properties; further work is needed to determine the relative contributions of fitting noise and ISM physics to the correlations.

  6. Gas Turbine Engine Behavioral Modeling

    OpenAIRE

    Meyer, Richard T; DeCarlo, Raymond A.; Pekarek, Steve; Doktorcik, Chris

    2014-01-01

    This paper develops and validates a power flow behavioral model of a gas tur- bine engine with a gas generator and free power turbine. “Simple” mathematical expressions to describe the engine’s power flow are derived from an understand- ing of basic thermodynamic and mechanical interactions taking place within the engine. The engine behavioral model presented is suitable for developing a supervisory level controller of an electrical power system that contains the en- gine connected to a gener...

  7. Overconsumption of Energy and Excessive Discretionary Food Intake Inflates Dietary Greenhouse Gas Emissions in Australia

    Directory of Open Access Journals (Sweden)

    Gilly A. Hendrie

    2016-10-01

    Full Text Available Population dietary guidelines have started to include information about the environmental impacts of food choices, but more quantifiable evidence is needed, particularly about the impacts associated with discretionary foods. This paper utilised the 2011–2012 Australian Health Survey food intake data along with a highly disaggregated input–output model to estimate the greenhouse gas emissions (GHGe of Australians’ dietary intake, and compare current patterns of eating which vary in diet quality and GHGe to the recommended diet. The average dietary GHGe were 18.72 ± 12.06 and 13.73 ± 8.72 kg CO2e/day for male and female adults, respectively. The correlation between total energy and GHGe was r = 0.54 (p < 0.001. Core foods contributed 68.4% and discretionary foods 29.4%. Within core foods, fresh meat and alternatives (33.9% was the greatest contributor. The modelling of current dietary patterns showed the contribution of discretionary foods to GHGe was 121% greater in the average diet and 307% greater in the “lower quality, higher GHGe” diet compared to the recommended diet. Reducing discretionary food intake would allow for small increases in emissions from core foods (in particular vegetables, dairy and grains, thereby providing a nutritional benefit at little environmental expense. Public health messages that promote healthy eating, eating to one’s energy needs and improved diet quality will also contribute to lowering GHGe.

  8. Aeroelastic modelling without the need for excessive computing power

    Energy Technology Data Exchange (ETDEWEB)

    Infield, D. [Loughborough Univ., Centre for Renewable Energy Systems Technology, Dept. of Electronic and Electrical Engineering, Loughborough (United Kingdom)

    1996-09-01

    The aeroelastic model presented here was developed specifically to represent a wind turbine manufactured by Northern Power Systems which features a passive pitch control mechanism. It was considered that this particular turbine, which also has low solidity flexible blades, and is free yawing, would provide a stringent test of modelling approaches. It was believed that blade element aerodynamic modelling would not be adequate to properly describe the combination of yawed flow, dynamic inflow and unsteady aerodynamics; consequently a wake modelling approach was adopted. In order to keep computation time limited, a highly simplified, semi-free wake approach (developed in previous work) was used. a similarly simple structural model was adopted with up to only six degrees of freedom in total. In order to take account of blade (flapwise) flexibility a simple finite element sub-model is used. Good quality data from the turbine has recently been collected and it is hoped to undertake model validation in the near future. (au)

  9. Modelling gas markets - a survey

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    This report reviews research of relevance to the analysis of present and future developments of the European natural gas market. The research activities considered are confined to (1) numerical models for gas markets, (2) analyses of energy demand, and (3) analyses of behaviour and cost structures in the transmission and distribution sector. Most of the market models are strictly micro economic and assume perfect competition or a game-theoretical equilibrium. They use sophisticated solution concepts, but very simplified specifications of supply and demand functions. Most of the research on demand is econometric analyses. These have more detailed model specification than have the aggregated market models. It is found, however, that the econometric literature based on neo-classical economics has not yielded unambiguous results and the specifications disregard important real world aspects of gas demand. The section on demand concludes that the extent of the gas grid is an important determinant for gas demand, but there has been virtually no research on what determines this variable. Data about transmission and distribution of gas in Europe is scarce and only a few non-econometric and virtually no econometric analyses are available. However, some conclusions can be made from relevant North American literature: (1) there has been significant autonomous technical progress in the transmission industry, (2) distribution costs strongly depend on geographical and other conditions, and (3) ownership, whether private or public, may be important for distribution costs and pricing policies. 56 refs., 3 figs., 1 tab.

  10. Modelling gas markets - a survey

    International Nuclear Information System (INIS)

    1997-01-01

    This report reviews research of relevance to the analysis of present and future developments of the European natural gas market. The research activities considered are confined to (1) numerical models for gas markets, (2) analyses of energy demand, and (3) analyses of behaviour and cost structures in the transmission and distribution sector. Most of the market models are strictly micro economic and assume perfect competition or a game-theoretical equilibrium. They use sophisticated solution concepts, but very simplified specifications of supply and demand functions. Most of the research on demand is econometric analyses. These have more detailed model specification than have the aggregated market models. It is found, however, that the econometric literature based on neo-classical economics has not yielded unambiguous results and the specifications disregard important real world aspects of gas demand. The section on demand concludes that the extent of the gas grid is an important determinant for gas demand, but there has been virtually no research on what determines this variable. Data about transmission and distribution of gas in Europe is scarce and only a few non-econometric and virtually no econometric analyses are available. However, some conclusions can be made from relevant North American literature: (1) there has been significant autonomous technical progress in the transmission industry, (2) distribution costs strongly depend on geographical and other conditions, and (3) ownership, whether private or public, may be important for distribution costs and pricing policies. 56 refs., 3 figs., 1 tab

  11. Gas-Filled Capillary Model

    International Nuclear Information System (INIS)

    Steinhauer, L. C.; Kimura, W. D.

    2006-01-01

    We have developed a 1-D, quasi-steady-state numerical model for a gas-filled capillary discharge that is designed to aid in selecting the optimum capillary radius in order to guide a laser beam with the required intensity through the capillary. The model also includes the option for an external solenoid B-field around the capillary, which increases the depth of the parabolic density channel in the capillary, thereby allowing for propagation of smaller laser beam waists. The model has been used to select the parameters for gas-filled capillaries to be utilized during the Staged Electron Laser Acceleration -- Laser Wakefield (STELLA-LW) experiment

  12. Can we determine what controls the spatio-temporal distribution of d-excess and 17O-excess in precipitation using the LMDZ general circulation model?

    Directory of Open Access Journals (Sweden)

    C. Risi

    2013-09-01

    Full Text Available Combined measurements of the H218O and HDO isotopic ratios in precipitation, leading to second-order parameter D-excess, have provided additional constraints on past climates compared to the H218O isotopic ratio alone. More recently, measurements of H217O have led to another second-order parameter: 17O-excess. Recent studies suggest that 17O-excess in polar ice may provide information on evaporative conditions at the moisture source. However, the processes controlling the spatio-temporal distribution of 17O-excess are still far from being fully understood. We use the isotopic general circulation model (GCM LMDZ to better understand what controls d-excess and 17O-excess in precipitation at present-day (PD and during the last glacial maximum (LGM. The simulation of D-excess and 17O-excess is evaluated against measurements in meteoric water, water vapor and polar ice cores. A set of sensitivity tests and diagnostics are used to quantify the relative effects of evaporative conditions (sea surface temperature and relative humidity, Rayleigh distillation, mixing between vapors from different origins, precipitation re-evaporation and supersaturation during condensation at low temperature. In LMDZ, simulations suggest that in the tropics convective processes and rain re-evaporation are important controls on precipitation D-excess and 17O-excess. In higher latitudes, the effect of distillation, mixing between vapors from different origins and supersaturation are the most important controls. For example, the lower d-excess and 17O-excess at LGM simulated at LGM are mainly due to the supersaturation effect. The effect of supersaturation is however very sensitive to a parameter whose tuning would require more measurements and laboratory experiments. Evaporative conditions had previously been suggested to be key controlling factors of d-excess and 17O-excess, but LMDZ underestimates their role. More generally, some shortcomings in the simulation of 17O-excess

  13. Hydrodynamic behaviour and comparison of technologies for the removal of excess biomass in gas-phase biofilters.

    Science.gov (United States)

    Mendoza, J A; Prado, O J; Veiga, M C; Kennes, C

    2004-01-01

    The hydrodynamic behaviour of a biofilter fed toluene and packed with an inert carrier was evaluated on start-up and after long-term operation, using both methane and styrene as tracers in Residence Time Distribution experiments. Results indicated some deviation from ideal plug flow behaviour after 2-year operation. It was also observed that the retention time of VOCs gradually increased with time and was significantly longer than the average residence time of the bulk gas phase. Non-ideal hydrodynamic behaviour in packed beds may be due to excess biomass accumulation and affects both reactor modeling and performance. Therefore, several methods were studied for the removal of biomass after long-term biofilter operation: filling with water and draining, backwashing, and air sparging. Several flow rates and temperatures (20-60 degrees C) were applied using either water or different chemicals (NaOH, NaOCl, HTAB) in aqueous solution. Usually, higher flow rates and higher temperatures allowed the removal of more biomass, but the efficiency of biomass removal was highly dependent on the pressure drop reached before the treatment. The filling/draining method was the least efficient for biomass removal, although the treatment did basically not generate any biological inhibition. The efficiency of backwashing and air sparging was relatively similar and was more effective when adding chemicals. However, treatments with chemicals resulted in a significant decrease of the biofilter's performance immediately after applying the treatment, needing periods of several days to recover the original performance. The effect of manually mixing the packing material was also evaluated in duplicate experiments. Quite large amounts of biomass were removed but disruption of the filter bed was observed. Batch assays were performed simultaneously in order to support and quantify the observed inhibitory effects of the different chemicals and temperatures used during the treatments.

  14. The optical/ultraviolet excess of isolated neutron stars in the resonant cyclotron scattering model

    Science.gov (United States)

    Tong, Hao; Xu, Ren-Xin; Song, Li-Ming

    2011-12-01

    X-ray dim isolated neutron stars are peculiar pulsar-like objects, characterized by their Planck-like spectrum. In studying their spectral energy distributions, optical/ultraviolet (UV) excess is a long standing problem. Recently Kaplan et al. measured the optical/UV excess for all seven sources, which is understandable in the resonant cyclotron scattering (RCS) model previously addressed. The RCS model calculations show that the RCS process can account for the observed optical/UV excess for most sources. The flat spectrum of RX J2143.0+0654 may be due to contributions from the bremsstrahlung emission of the electron system in addition to the RCS process.

  15. Extension of the segment-based Wilson and NRTL models for correlation of excess molar enthalpies of polymer solutions

    International Nuclear Information System (INIS)

    Sadeghi, Rahmat

    2005-01-01

    The polymer Wilson model and the polymer NRTL model have been extended for the representation of the excess enthalpy of multicomponent polymer solutions. Applicability of obtained equations in the correlation of the excess enthalpies of polymer solutions has been examined. It is found that the both models are suitable models in representing the published excess enthalpy data for the tested polymer solutions

  16. Denitrification rates and excess nitrogen gas concentrations in the Arabian Sea oxygen deficient zone

    Digital Repository Service at National Institute of Oceanography (India)

    Devol, A; Uhlenhopp, A; Naqvi, S.W.A; Brandes, J.A; Jayakumar, D.A; Naik, H.; Gaurin, S.; Codispoti, L.A.; Yoshinari, T.

    Rates of canonical, i.e. heterotrophic, water-column denitrification were measured by sup(15)N incubation techniques at a number of coastal and open ocean stations in the Arabian Sea. Measurements of N2 :Ar gas ratios were also made to obtain...

  17. Perumusan Model Moneter Berdasarkan Perilaku Gas Ideal

    Directory of Open Access Journals (Sweden)

    Rachmad Resmiyanto

    2014-04-01

    Full Text Available Telah disusun sebuah model moneter yang berdasarkan perilaku gas ideal. Model disusun dengan menggunakan metode kias/analogi. Model moneter gas ideal mengiaskan jumlah uang beredar dengan volume gas, daya beli dengan tekanan gas dan produksi barang dengan suhu gas. Model ini memiliki formulasi yang berbeda dengan Teori Kuantitas Uang (Quantity Theory of Money yang dicetuskan oleh Irving Fisher, model moneter Marshal-Pigou dari Cambridge serta model moneter ala Keynes. Selama ini 3 model tersebut dianggap sebagai model yang mapan dalam teori moneter pada buku-buku teks ekonomi. Model moneter gas ideal dapat menjadi cara pandang baru terhadap sistem moneter.

  18. Observation of an Excess in the Search for the Standard Model Higgs Boson at ALEPH

    CERN Document Server

    Barate, R.; Ghez, Philippe; Goy, C.; Jezequel, S.; Lees, J.P.; Martin, F.; Merle, E.; Minard, M.N.; Pietrzyk, B.; Bravo, S.; Casado, M.P.; Chmeissani, M.; Crespo, J.M.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll.; Grauges, E.; Lopez, J.; Martinez, M.; Merino, G.; Miquel, R.; Mir, L.M.; Pacheco, A.; Paneque, D.; Ruiz, H.; Colaleo, A.; Creanza, D.; De Filippis, N.; de Palma, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Nuzzo, S.; Ranieri, A.; Raso, G.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Tricomi, A.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Abbaneo, D.; Azzurri, P.; Barklow, T.; Boix, G.; Buchmuller, O.; Cattaneo, M.; Cerutti, F.; Clerbaux, B.; Dissertori, G.; Drevermann, H.; Forty, R.W.; Frank, M.; Gianotti, F.; Greening, T.C.; Hansen, J.B.; Harvey, John; Hutchcroft, D.E.; Janot, P.; Jost, B.; Kado, M.; Lemaitre, V.; Maley, P.; Mato, P.; Minten, A.; Moutoussi, A.; Ranjard, F.; Rolandi, Gigi; Schlatter, D.; Schmitt, M.; Schneider, O.; Spagnolo, P.; Tejessy, W.; Teubert, F.; Tournefier, E.; Valassi, A.; Ward, J.J.; Wright, A.E.; Ajaltouni, Z.; Badaud, F.; Dessagne, S.; Falvard, A.; Fayolle, D.; Gay, P.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.C.; Pallin, D.; Pascolo, J.M.; Perret, P.; Podlyski, F.; Hansen, J.D.; Hansen, J.R.; Hansen, P.H.; Nilsson, B.S.; Waananen, A.; Daskalakis, G.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Vayaki, A.; Blondel, A.; Brient, J.C.; Machefert, F.; Rouge, A.; Swynghedauw, M.; Tanaka, R.; Videau, H.; Focardi, E.; Parrini, G.; Zachariadou, K.; Antonelli, A.; Antonelli, M.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Chiarella, V.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G.P.; Passalacqua, L.; Pepe-Altarelli, M.; Chalmers, M.; Halley, A.W.; Kennedy, J.; Lynch, J.G.; Negus, P.; O'Shea, V.; Raeven, B.; Smith, D.; Teixeira-Dias, P.; Thompson, A.S.; Cavanaugh, R.; Dhamotharan, S.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E.E.; Leibenguth, G.; Putzer, A.; Tittel, K.; Werner, S.; Wunsch, M.; Beuselinck, R.; Binnie, D.M.; Cameron, W.; Davies, G.; Dornan, P.J.; Girone, M.; Marinelli, N.; Nowell, J.; Przysiezniak, H.; Sedgbeer, J.K.; Thompson, J.C.; Thomson, Evelyn J.; White, R.; Ghete, V.M.; Girtler, P.; Kneringer, E.; Kuhn, D.; Rudolph, G.; Bouhova-Thacker, E.; Bowdery, C.K.; Clarke, D.P.; Ellis, G.; Finch, A.J.; Foster, F.; Hughes, G.; Jones, R.W.L.; Pearson, M.R.; Robertson, N.A.; Smizanska, M.; Giehl, I.; Holldorfer, F.; Jakobs, K.; Kleinknecht, K.; Krocker, M.; Muller, A.S.; Nurnberger, H.A.; Quast, G.; Renk, B.; Rohne, E.; Sander, H.G.; Schmeling, S.; Wachsmuth, H.; Zeitnitz, C.; Ziegler, T.; Bonissent, A.; Carr, J.; Coyle, P.; Curtil, C.; Ealet, A.; Fouchez, D.; Leroy, O.; Kachelhoffer, T.; Payre, P.; Rousseau, D.; Tilquin, A.; Aleppo, M.; Gilardoni, Simone S.; Ragusa, F.; David, A.; Dietl, H.; Ganis, G.; Heister, A.; Huttmann, K.; Lutjens, G.; Mannert, C.; Manner, W.; Moser, H.G.; Schael, S.; Settles, R.; Stenzel, H.; Wolf, G.; Boucrot, J.; Callot, O.; Davier, M.; Duflot, L.; Grivaz, J.F.; Heusse, P.; Jacholkowska, A.; Serin, L.; Veillet, J.J.; Videau, I.; de Vivie de Regie, J.B.; Yuan, C.; Zerwas, D.; Bagliesi, Giuseppe; Boccali, T.; Calderini, G.; Ciulli, V.; Foa, L.; Giammanco, A.; Giassi, A.; Ligabue, F.; Messineo, A.; Palla, F.; Rizzo, G.; Sanguinetti, G.; Sciaba, A.; Sguazzoni, G.; Tenchini, R.; Venturi, A.; Verdini, P.G.; Blair, G.A.; Coles, J.; Cowan, G.; Green, M.G.; Jones, L.T.; Medcalf, T.; Strong, J.A.; Clifft, R.W.; Edgecock, T.R.; Norton, P.R.; Tomalin, I.R.; Bloch-Devaux, Brigitte; Boumediene, D.; Colas, P.; Fabbro, B.; Lancon, E.; Lemaire, M.C.; Locci, E.; Perez, P.; Rander, J.; Renardy, J.F.; Rosowsky, A.; Seager, P.; Trabelsi, A.; Tuchming, B.; Vallage, B.; Konstantinidis, N.; Loomis, C.; Litke, A.M.; Taylor, G.; Booth, C.N.; Cartwright, S.; Combley, F.; Hodgson, P.N.; Lehto, M.; Thompson, L.F.; Affholderbach, K.; Boehrer, Armin; Brandt, S.; Grupen, C.; Hess, J.; Misiejuk, A.; Prange, G.; Sieler, U.; Borean, C.; Giannini, G.; Gobbo, B.; He, H.; Putz, J.; Rothberg, J.; Wasserbaech, S.; Armstrong, S.R.; Cranmer, K.; Elmer, P.; Ferguson, D.P.S.; Gao, Y.; Gonzalez, S.; Hayes, O.J.; Hu, H.; Jin, S.; Kile, J.; McNamara, P.A., III; Nielsen, J.; Orejudos, W.; Pan, Y.B.; Saadi, Y.; Scott, I.J.; Shao, N.; von Wimmersperg-Toeller, J.H.; Walsh, J.; Wiedenmann, W.; Wu, J.; Wu, Sau Lan; Wu, X.; Zobernig, G.

    2000-01-01

    A search has been performed for the Standard Model Higgs boson in the data sample collected with the ALEPH detector at LEP, at centre-of-mass energies up to 209 GeV. An excess of 3 $\\sigma$ beyond the background expectation is found, consistent with the production of the Higgs boson with a mass near 114 GeV=c^2 . Much of this excess is seen in the four-jet analyses, where three high purity events are selected.

  19. Percolation model of excess electrical noise in transition-edge sensors

    International Nuclear Information System (INIS)

    Lindeman, M.A.; Anderson, M.B.; Bandler, S.R.; Bilgri, N.; Chervenak, J.; Gwynne Crowder, S.; Fallows, S.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.; Kilbourne, C.A.; Lai, T.; Man, J.; McCammon, D.; Nelms, K.L.; Porter, F.S.; Rocks, L.E.; Saab, T.; Sadleir, J.; Vidugiris, G.

    2006-01-01

    We present a geometrical model to describe excess electrical noise in transition-edge sensors (TESs). In this model, a network of fluctuating resistors represents the complex dynamics inside a TES. The fluctuations can cause several resistors in series to become superconducting. Such events short out part of the TES and generate noise because much of the current percolates through low resistance paths. The model predicts that excess white noise increases with decreasing TES bias resistance (R/R N ) and that perpendicular zebra stripes reduce noise and alpha of the TES by reducing percolation

  20. A Structural Equation Model on Korean Adolescents' Excessive Use of Smartphones.

    Science.gov (United States)

    Lee, Hana; Kim, JooHyun

    2018-03-31

    We develop a unified structural model that defines multi-relationships between systematic factors causing excessive use of smartphones and the corresponding results. We conducted a survey with adolescents who live in Seoul, Pusan, Gangneung, Donghae, and Samcheok from Feb. to Mar. 2016. We utilized SPSS Ver. 22 and Amos Ver. 22 to analyze the survey result at a 0.05 significance level. To investigate demographic characteristics of the participants and their variations, we employed descriptive analysis. We adopted the maximum likelihood estimate method to verify the fitness of the hypothetical model and the hypotheses therein. We used χ 2 statistics, GFI, AGFI, CFI, NFI, IFI, RMR, and RMSEA to verify the fitness of our structural model. (1) Our proposed structural model demonstrated a fine fitness level. (2) Our proposed structural model could describe the excessive use of a smartphone with 88.6% accuracy. (3) The absence of the family function and relationship between friends, impulsiveness, and low self-esteem were confirmed as key factors that cause excessive use of smartphones. (4) Further, impulsiveness and low self-esteem are closely related to the absence of family functions and relations between friends by 68.3% and 54.4%, respectively. We suggest that nursing intervention programs from various angles are required to reduce adolescents' excessive use of smartphones. For example, family communication programs would be helpful for both parents and children. Consultant programs about friend relationship also meaningful for the program. Copyright © 2018. Published by Elsevier B.V.

  1. A conceptual model of psychosocial risk and protective factors for excessive gestational weight gain.

    Science.gov (United States)

    Hill, Briony; Skouteris, Helen; McCabe, Marita; Milgrom, Jeannette; Kent, Bridie; Herring, Sharon J; Hartley-Clark, Linda; Gale, Janette

    2013-02-01

    nearly half of all women exceed the guideline recommended pregnancy weight gain for their Body Mass Index (BMI) category. Excessive gestational weight gain (GWG) is correlated positively with postpartum weight retention and is a predictor of long-term, higher BMI in mothers and their children. Psychosocial factors are generally not targeted in GWG behaviour change interventions, however, multifactorial, conceptual models that include these factors, may be useful in determining the pathways that contribute to excessive GWG. We propose a conceptual model, underpinned by health behaviour change theory, which outlines the psychosocial determinants of GWG, including the role of motivation and self-efficacy towards healthy behaviours. This model is based on a review of the existing literature in this area. there is increasing evidence to show that psychosocial factors, such as increased depressive symptoms, anxiety, lower self-esteem and body image dissatisfaction, are associated with excessive GWG. What is less known is how these factors might lead to excessive GWG. Our conceptual model proposes a pathway of factors that affect GWG, and may be useful for understanding the mechanisms by which interventions impact on weight management during pregnancy. This involves tracking the relationships among maternal psychosocial factors, including body image concerns, motivation to adopt healthy lifestyle behaviours, confidence in adopting healthy lifestyle behaviours for the purposes of weight management, and actual behaviour changes. health-care providers may improve weight gain outcomes in pregnancy if they assess and address psychosocial factors in pregnancy. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. The BERR gas market model

    International Nuclear Information System (INIS)

    2007-10-01

    Security of supply is one of the key objectives in the UK's department of Business Enterprise and Regulatory Reform (BERR) gas market model. BERR found that a useful way to measure energy security was to estimate future 'expected energy unserved'. This comprises a combination of possible levels of shortfall between supply and demand and other probabilities to give a probability-weighted amount of unserved demand. BERR has also studied the conditions (inputs) that are likely to result in lower expected energy unserved, i.e. it has identified the drivers of security of supply and has developed a framework for categorising these drivers

  3. A SUSY inspired simplified model for the 750 GeV diphoton excess

    Energy Technology Data Exchange (ETDEWEB)

    Gabrielli, E. [Dipart. di Fisica Teorica, Università di Trieste, Strada Costiera 11, I-34151 Trieste (Italy); INFN, Sezione di Trieste, Via Valerio 2, I-34127 Trieste (Italy); NICPB, Rävala 10, Tallinn 10143 (Estonia); Kannike, K., E-mail: kannike@cern.ch [NICPB, Rävala 10, Tallinn 10143 (Estonia); Mele, B. [INFN, Sezione di Roma, c/o Dipart. di Fisica, Università di Roma “La Sapienza”, Piazzale Aldo Moro 2, I-00185 Rome (Italy); Raidal, M. [NICPB, Rävala 10, Tallinn 10143 (Estonia); Institute of Physics, University of Tartu (Estonia); Spethmann, C.; Veermäe, H. [NICPB, Rävala 10, Tallinn 10143 (Estonia)

    2016-05-10

    The evidence for a new neutral scalar particle from the 750 GeV diphoton excess, and the absence of any other signal of new physics at the LHC so far, suggests the existence of new coloured scalars. To study this possibility, we propose a supersymmetry inspired simplified model, extending the Standard Model with a singlet scalar and with heavy scalar fields carrying both colour and electric charges – new scalar quarks. To allow the latter to decay, and to generate the dark matter of the Universe, we also add a neutral fermion to the particle content. We show that this model provides a two-parameter fit to the observed diphoton excess consistently with cosmology, while the allowed parameter space is bounded by the consistency of the model. In the context of our simplified model this implies the existence of other supersymmetric particles accessible at the LHC, rendering this scenario falsifiable.

  4. Correction of Excessive Precipitation over Steep Mountains in a General Circulation Model (GCM)

    Science.gov (United States)

    Chao, Winston C.

    2012-01-01

    Excessive precipitation over steep and high mountains (EPSM) is a well-known problem in GCMs and regional climate models even at a resolution as high as 19km. The affected regions include the Andes, the Himalayas, Sierra Madre, New Guinea and others. This problem also shows up in some data assimilation products. Among the possible causes investigated in this study, we found that the most important one, by far, is a missing upward transport of heat out of the boundary layer due to the vertical circulations forced by the daytime subgrid-scale upslope winds, which in turn is forced by heated boundary layer on the slopes. These upslope winds are associated with large subgrid-scale topographic variance, which is found over steep mountains. Without such subgrid-scale heat ventilation, the resolvable-scale upslope flow in the boundary layer generated by surface sensible heat flux along the mountain slopes is excessive. Such an excessive resolvable-scale upslope flow in the boundary layer combined with the high moisture content in the boundary layer results in excessive moisture transport toward mountaintops, which in turn gives rise to excessive precipitation over the affected regions. We have parameterized the effects of subgrid-scale heated-slope-induced vertical circulation (SHVC) by removing heat from the boundary layer and depositing it in the layers higher up when topographic variance exceeds a critical value. Test results using NASA/Goddard's GEOS-5 GCM have shown that the EPSM problem is largely solved.

  5. Off gas condenser performance modelling

    International Nuclear Information System (INIS)

    Cains, P.W.; Hills, K.M.; Waring, S.; Pratchett, A.G.

    1989-12-01

    A suite of three programmes has been developed to model the ruthenium decontamination performance of a vitrification plant off-gas condenser. The stages of the model are: condensation of water vapour, NO x absorption in the condensate, RuO 4 absorption in the condensate. Juxtaposition of these stages gives a package that may be run on an IBM-compatible desktop PC. Experimental work indicates that the criterion [HNO 2 ] > 10 [RuO 4 ] used to determine RuO 4 destruction in solution is probably realistic under condenser conditions. Vapour pressures of RuO 4 over aqueous solutions at 70 o -90 o C are slightly lower than the values given by extrapolating the ln K p vs. T -1 relation derived from lower temperature data. (author)

  6. Modeling the Excess Cell Surface Stored in a Complex Morphology of Bleb-Like Protrusions.

    Directory of Open Access Journals (Sweden)

    Maryna Kapustina

    2016-03-01

    Full Text Available Cells transition from spread to rounded morphologies in diverse physiological contexts including mitosis and mesenchymal-to-amoeboid transitions. When these drastic shape changes occur rapidly, cell volume and surface area are approximately conserved. Consequently, the rounded cells are suddenly presented with a several-fold excess of cell surface whose area far exceeds that of a smooth sphere enclosing the cell volume. This excess is stored in a population of bleb-like protrusions (BLiPs, whose size distribution is shown by electron micrographs to be skewed. We introduce three complementary models of rounded cell morphologies with a prescribed excess surface area. A 2D Hamiltonian model provides a mechanistic description of how discrete attachment points between the cell surface and cortex together with surface bending energy can generate a morphology that satisfies a prescribed excess area and BLiP number density. A 3D random seed-and-growth model simulates efficient packing of BLiPs over a primary rounded shape, demonstrating a pathway for skewed BLiP size distributions that recapitulate 3D morphologies. Finally, a phase field model (2D and 3D posits energy-based constitutive laws for the cell membrane, nematic F-actin cortex, interior cytosol, and external aqueous medium. The cell surface is equipped with a spontaneous curvature function, a proxy for the cell surface-cortex couple, that is a priori unknown, which the model "learns" from the thin section transmission electron micrograph image (2D or the "seed and growth" model image (3D. Converged phase field simulations predict self-consistent amplitudes and spatial localization of pressure and stress throughout the cell for any posited stationary morphology target and cell compartment constitutive properties. The models form a general framework for future studies of cell morphological dynamics in a variety of biological contexts.

  7. Analysis Influence of Mixing Gd2O3 in the Silicide Fuel Element to Core Excess Reactivity of RSG-GAS

    International Nuclear Information System (INIS)

    Susilo, Jati

    2004-01-01

    Gadolinium (Gd 2 O 3 ) is a burnable poison material mixed in the pin fuel element of the LWR core used to decrease core excess reactivity. In this research, analysis influence of mixing Gd 2 O 3 in the silicide fuel element to excess reactivity of the RSG-GAS core had been done. Equivalent cell of the equilibrium core developed by L.E.Strawbridge from Westing House Co. burn-up calculation has been done using SRAC-PIJ computer code achieve infinite multiplication factor (k x ). Value of Gd 2 O 3 concentration in the fuel element (pcm) showed by mass ratio of Gd 2 O 3 (gram) to that U 3 Si 2 (gram) times 10 5 , that is 0 pcm ∼ 100 pcm. From the calculation results analysis showed that Gd 2 O 3 concentration added should be considered. because a large number of Gd 2 O 3 will result in not achieving criticality at the Beginning Of Cycle. The maximum concentration of Gd 2 O 3 for RSG-GAS equilibrium fueled silicide 2.96 grU/cc is 80 pcm or 52.02 mgram/fuel plate. Maximum reduction of core excess reactivity due to mixing of Gd 2 O 3 in the RSG-GAS silicide fuels was around 1.502 %Δk/k, and hence not achieving the standard nominal excess reactivity for RSG-GAS core using high density of U 3 Si 2 -Al fuel. (author)

  8. Analytical models of probability distribution and excess noise factor of solid state photomultiplier signals with crosstalk

    International Nuclear Information System (INIS)

    Vinogradov, S.

    2012-01-01

    Silicon Photomultipliers (SiPM), also called Solid State Photomultipliers (SSPM), are based on Geiger mode avalanche breakdown that is limited by a strong negative feedback. An SSPM can detect and resolve single photons due to the high gain and ultra-low excess noise of avalanche multiplication in this mode. Crosstalk and afterpulsing processes associated with the high gain introduce specific excess noise and deteriorate the photon number resolution of the SSPM. The probabilistic features of these processes are widely studied because of its significance for the SSPM design, characterization, optimization and application, but the process modeling is mostly based on Monte Carlo simulations and numerical methods. In this study, crosstalk is considered to be a branching Poisson process, and analytical models of probability distribution and excess noise factor (ENF) of SSPM signals based on the Borel distribution as an advance on the geometric distribution models are presented and discussed. The models are found to be in a good agreement with the experimental probability distributions for dark counts and a few photon spectrums in a wide range of fired pixels number as well as with observed super-linear behavior of crosstalk ENF.

  9. A model explaining neutrino masses and the DAMPE cosmic ray electron excess

    Science.gov (United States)

    Fan, Yi-Zhong; Huang, Wei-Chih; Spinrath, Martin; Tsai, Yue-Lin Sming; Yuan, Qiang

    2018-06-01

    We propose a flavored U(1)eμ neutrino mass and dark matter (DM) model to explain the recent DArk Matter Particle Explorer (DAMPE) data, which feature an excess on the cosmic ray electron plus positron flux around 1.4 TeV. Only the first two lepton generations of the Standard Model are charged under the new U(1)eμ gauge symmetry. A vector-like fermion ψ, which is our DM candidate, annihilates into e± and μ± via the new gauge boson Z‧ exchange and accounts for the DAMPE excess. We have found that the data favors a ψ mass around 1.5 TeV and a Z‧ mass around 2.6 TeV, which can potentially be probed by the next generation lepton colliders and DM direct detection experiments.

  10. A model explaining neutrino masses and the DAMPE cosmic ray electron excess

    DEFF Research Database (Denmark)

    Fan, Yi Zhong; Huang, Wei Chih; Spinrath, Martin

    2018-01-01

    We propose a flavored U(1)eμ neutrino mass and dark matter (DM) model to explain the recent DArk Matter Particle Explorer (DAMPE) data, which feature an excess on the cosmic ray electron plus positron flux around 1.4 TeV. Only the first two lepton generations of the Standard Model are charged under...... the new U(1)eμ gauge symmetry. A vector-like fermion ψ, which is our DM candidate, annihilates into e± and μ± via the new gauge boson Z′ exchange and accounts for the DAMPE excess. We have found that the data favors a ψ mass around 1.5 TeV and a Z′ mass around 2.6 TeV, which can potentially be probed...

  11. Modeling Gas Dynamics in California Sea Lions

    Science.gov (United States)

    2015-09-30

    W. and Fahlman, A. (2009). Could beaked whales get the bends?. Effect of diving behaviour and physiology on modelled gas exchange for three species...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Modeling Gas Dynamics in California Sea Lions Andreas...to update a current gas dynamics model with recently acquired data for respiratory compliance (P-V), and body compartment size estimates in

  12. Low scale composite Higgs model and 1.8 ˜2 TeV diboson excess

    Science.gov (United States)

    Bian, Ligong; Liu, Da; Shu, Jing

    2018-04-01

    We consider a simple solution to explain the recent diboson excess observed by ATLAS and CMS Collaborations in models with custodial symmetry SU(2)L × SU(2)R → SU(2)c. The SU(2)L triplet vector boson ρ with mass range of 1.8 ˜ 2 TeV would be produced through the Drell-Yan process with sizable diboson decay branching to account for the excess. The other SU(2)L × SU(2)R bidoublet axial vector boson a would cancel all deviations of electroweak obervables induced by ρ even if the SM fermions mix with some heavy vector-like (composite) fermions which couple to ρ (“nonuniversally partially composite”), therefore allows arbitrary couplings between each SM fermion and ρ. We present our model in the “General Composite Higgs” framework with SO(5) × U(1)X → SO(4) × U(1)X breaking at scale f and demand the first Weinberg sum rule and positive gauge boson form factors as the theoretical constraints. We find that our model can fit the diboson excess very well if the left-handed SM light quarks, charged leptons and tops have zero, zero/moderately small and moderate/large composite components for reasonable values of gρ and f. The correlation between tree level S parameter and the h → Zγ suggest a large a contribution to h → Zγ and it is indeed a 𝒪(1) effect in our parameter space which provides a strong hint for our scenario if this diboson excess is confirmed by the 13 ˜ 14 TeV LHC Run II.

  13. COLUMBUS. A global gas market model

    Energy Technology Data Exchange (ETDEWEB)

    Hecking, Harald; Panke, Timo

    2012-03-15

    A model of the global gas market is presented which in its basic version optimises the future development of production, transport and storage capacities as well as the actual gas flows around the world assuming perfect competition. Besides the transport of natural gas via pipelines also the global market for liquefied natural gas (LNG) is modelled using a hub-and-spoke approach. While in the basic version of the model an inelastic demand and a piecewise-linear supply function are used, both can be changed easily, e.g. to a Golombek style production function or a constant elasticity of substitution (CES) demand function. Due to the usage of mixed complementary programming (MCP) the model additionally allows for the simulation of strategic behaviour of different players in the gas market, e.g. the gas producers.

  14. Lattice Model for Production of Gas

    KAUST Repository

    Marder, M.

    2017-12-01

    We define a lattice model for rock, absorbers, and gas that makes it possible to examine the flow of gas to a complicated absorbing boundary over long periods of time. The motivation is to deduce the geometry of the boundary from the time history of gas absorption. We find a solution to this model using Green\\'s function techniques, and apply the solution to three absorbing networks of increasing complexity.

  15. Lattice Model for Production of Gas

    OpenAIRE

    Marder, M.; Eftekhari, Behzad; Patzek, Tadeusz W

    2017-01-01

    We define a lattice model for rock, absorbers, and gas that makes it possible to examine the flow of gas to a complicated absorbing boundary over long periods of time. The motivation is to deduce the geometry of the boundary from the time history of gas absorption. We find a solution to this model using Green's function techniques, and apply the solution to three absorbing networks of increasing complexity.

  16. Analysis of an effective solution to excessive heat supply in a city primary heating network using gas-fired boilers for peak-load compensation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hai-Chao; Jiao, Wen-Ling; Zou, Ping-Hua; Liu, Jing-Cheng [School of Municipal and Environmental Engineering, Harbin Institute of Technology, mail box 2645, 202 Haihe Road, Nangang District, Harbin 150090 (China)

    2010-11-15

    Through investigation of the Dengfeng heating network in the city of Daqing, China, for the 2007-2008 heating season, we found serious problems of excessive heat supply in the primary heating network. Therefore, we propose the application of gas-fired boilers in underperforming heating substations as peak-load heat sources to effectively adapt to the regulation demands of seasonal heat-load fluctuations and reduce the excessive heat supply. First, we calculated the excessive heat supply rates (EHSRs) of five substations using detailed investigative data. We then discussed the feasibility of the proposed scheme providing energy savings from both energetic and exergetic points of view. The results showed that the average EHSR of the five substations between January and March was 20.57% of the gross heat production but consequently reduced to 6.24% with the installation of the gas-fired boilers. Therefore, the combined heating scheme with coal as the basic heat-source and gas-fired boilers as peak-load heat sources is energy-efficient to some extent, although requires the use of natural gas. Meanwhile, the exergy decreased by 10.97%, which indicates that the combined heating scheme effectively reduces the primary energy consumption and pollutant emission of the heating systems. (author)

  17. Animal models of cerebral arterial gas embolism

    NARCIS (Netherlands)

    Weenink, Robert P.; Hollmann, Markus W.; van Hulst, Robert A.

    2012-01-01

    Cerebral arterial gas embolism is a dreaded complication of diving and invasive medical procedures. Many different animal models have been used in research on cerebral arterial gas embolism. This review provides an overview of the most important characteristics of these animal models. The properties

  18. Correction of Excessive Precipitation Over Steep and High Mountains in a General Circulation Model

    Science.gov (United States)

    Chao, Winston C.

    2012-01-01

    Excessive precipitation over steep and high mountains (EPSM) is a well-known problem in GCMs and meso-scale models. This problem impairs simulation and data assimilation products. Among the possible causes investigated in this study, we found that the most important one, by far, is a missing upward transport of heat out of the boundary layer due to the vertical circulations forced by the daytime upslope winds, which are forced by the heated boundary layer on subgrid-scale slopes. These upslope winds are associated with large subgrid-scale topographic variation, which is found over steep and high mountains. Without such subgridscale heat ventilation, the resolvable-scale upslope flow in the boundary layer generated by surface sensible heat flux along the mountain slopes is excessive. Such an excessive resolvablescale upslope flow combined with the high moisture content in the boundary layer results in excessive moisture transport toward mountaintops, which in turn gives rise to EPSM. Other possible causes of EPSM that we have investigated include 1) a poorly-designed horizontal moisture flux in the terrain-following coordinates, 2) the condition for cumulus convection being too easily satisfied at mountaintops, 3) the presence of conditional instability of the computational kind, and 4) the absence of blocked flow drag. These are all minor or inconsequential. We have parameterized the ventilation effects of the subgrid-scale heated-slope-induced vertical circulation (SHVC) by removing heat from the boundary layer and depositing it in layers higher up when the topographic variance exceeds a critical value. Test results using NASA/Goddard's GEOS-S GCM have shown that this largely solved the EPSM problem.

  19. Partitioning of excess mortality in population-based cancer patient survival studies using flexible parametric survival models

    Directory of Open Access Journals (Sweden)

    Eloranta Sandra

    2012-06-01

    Full Text Available Abstract Background Relative survival is commonly used for studying survival of cancer patients as it captures both the direct and indirect contribution of a cancer diagnosis on mortality by comparing the observed survival of the patients to the expected survival in a comparable cancer-free population. However, existing methods do not allow estimation of the impact of isolated conditions (e.g., excess cardiovascular mortality on the total excess mortality. For this purpose we extend flexible parametric survival models for relative survival, which use restricted cubic splines for the baseline cumulative excess hazard and for any time-dependent effects. Methods In the extended model we partition the excess mortality associated with a diagnosis of cancer through estimating a separate baseline excess hazard function for the outcomes under investigation. This is done by incorporating mutually exclusive background mortality rates, stratified by the underlying causes of death reported in the Swedish population, and by introducing cause of death as a time-dependent effect in the extended model. This approach thereby enables modeling of temporal trends in e.g., excess cardiovascular mortality and remaining cancer excess mortality simultaneously. Furthermore, we illustrate how the results from the proposed model can be used to derive crude probabilities of death due to the component parts, i.e., probabilities estimated in the presence of competing causes of death. Results The method is illustrated with examples where the total excess mortality experienced by patients diagnosed with breast cancer is partitioned into excess cardiovascular mortality and remaining cancer excess mortality. Conclusions The proposed method can be used to simultaneously study disease patterns and temporal trends for various causes of cancer-consequent deaths. Such information should be of interest for patients and clinicians as one way of improving prognosis after cancer is

  20. Mathematical models of natural gas consumption

    International Nuclear Information System (INIS)

    Sabo, Kristian; Scitovski, Rudolf; Vazler, Ivan; Zekic-Susac, Marijana

    2011-01-01

    In this paper we consider the problem of natural gas consumption hourly forecast on the basis of hourly movement of temperature and natural gas consumption in the preceding period. There are various methods and approaches for solving this problem in the literature. Some mathematical models with linear and nonlinear model functions relating to natural gas consumption forecast with the past natural gas consumption data, temperature data and temperature forecast data are mentioned. The methods are tested on concrete examples referring to temperature and natural gas consumption for the area of the city of Osijek (Croatia) from the beginning of the year 2008. The results show that most acceptable forecast is provided by mathematical models in which natural gas consumption and temperature are related explicitly.

  1. A tale of tails: Dark matter interpretations of the Fermi GeV excess in light of background model systematics

    NARCIS (Netherlands)

    Calore, F.; Cholis, I.; McCabe, C.; Weniger, C.

    2015-01-01

    Several groups have identified an extended excess of gamma rays over the modeled foreground and background emissions towards the Galactic center (GC) based on observations with the Fermi Large Area Telescope. This excess emission is compatible in morphology and spectrum with a telltale sign from

  2. A radiative neutrino mass model in light of DAMPE excess with hidden gauged U(1) symmetry

    Science.gov (United States)

    Nomura, Takaaki; Okada, Hiroshi; Wu, Peiwen

    2018-05-01

    We propose a one-loop induced neutrino mass model with hidden U(1) gauge symmetry, in which we successfully involve a bosonic dark matter (DM) candidate propagating inside a loop diagram in neutrino mass generation to explain the e+e‑ excess recently reported by the DArk Matter Particle Explorer (DAMPE) experiment. In our scenario dark matter annihilates into four leptons through Z' boson as DM DM → Z' Z' (Z' → l+ l‑) and Z' decays into leptons via one-loop effect. We then investigate branching ratios of Z' taking into account lepton flavor violations and neutrino oscillation data.

  3. Thermodynamic modelling of acid gas removal from natural gas using the Extended UNIQUAC model

    DEFF Research Database (Denmark)

    Sadegh, Negar; Stenby, Erling Halfdan; Thomsen, Kaj

    2017-01-01

    Thermodynamics of natural gas sweetening process needs to be known for proper design of natural gas treating plants. Absorption with aqueous N-Methyldiethanolamine is currently the most commonly used process for removal of acid gas (CO2 and H2S) impurities from natural gas. Model parameters...... for the Extended UNIQUAC model have already been determined by the same authors to calculate single acid gas solubility in aqueous MDEA. In this study, the model is further extended to estimate solubility of CO2 and H2S and their mixture in aqueous MDEA at high pressures with methane as a makeup gas....

  4. Development and validation of a predictive model for excessive postpartum blood loss: A retrospective, cohort study.

    Science.gov (United States)

    Rubio-Álvarez, Ana; Molina-Alarcón, Milagros; Arias-Arias, Ángel; Hernández-Martínez, Antonio

    2018-03-01

    postpartum haemorrhage is one of the leading causes of maternal morbidity and mortality worldwide. Despite the use of uterotonics agents as preventive measure, it remains a challenge to identify those women who are at increased risk of postpartum bleeding. to develop and to validate a predictive model to assess the risk of excessive bleeding in women with vaginal birth. retrospective cohorts study. "Mancha-Centro Hospital" (Spain). the elaboration of the predictive model was based on a derivation cohort consisting of 2336 women between 2009 and 2011. For validation purposes, a prospective cohort of 953 women between 2013 and 2014 were employed. Women with antenatal fetal demise, multiple pregnancies and gestations under 35 weeks were excluded METHODS: we used a multivariate analysis with binary logistic regression, Ridge Regression and areas under the Receiver Operating Characteristic curves to determine the predictive ability of the proposed model. there was 197 (8.43%) women with excessive bleeding in the derivation cohort and 63 (6.61%) women in the validation cohort. Predictive factors in the final model were: maternal age, primiparity, duration of the first and second stages of labour, neonatal birth weight and antepartum haemoglobin levels. Accordingly, the predictive ability of this model in the derivation cohort was 0.90 (95% CI: 0.85-0.93), while it remained 0.83 (95% CI: 0.74-0.92) in the validation cohort. this predictive model is proved to have an excellent predictive ability in the derivation cohort, and its validation in a latter population equally shows a good ability for prediction. This model can be employed to identify women with a higher risk of postpartum haemorrhage. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Modelling intragranular fission gas release in irradiation of sintered LWR UO2 fuel

    International Nuclear Information System (INIS)

    Loesoenen, Pekka

    2002-01-01

    A model for the release of stable fission gases by diffuion from sintered LWR UO 2 fuel grains is presented. The model takes into account intragranular gas bubble behaviour as a function of grain radius. The bubbles are assumed to be immobile and the gas migrates to grain boundaries by diffusion of single gas atoms. The intragranular bubble population in the model at low burn-ups or temperatures consists of numerous small bubbles. The presence of the bubbles attenuates the effective gas atom diffusion coefficient. Rapid coarsening of the bubble population in increased burn-up at elevated temperatures weakens significantly the attenuation of the effective diffusion coefficient. The solution method introduced in earlier papers, locally accurate method, is enhanced to allow accurate calculation of the intragranular gas behaviour in time varying conditions without excessive computing time. Qualitatively the detailed model can predict the gas retention in the grain better than a more simple model

  6. Access, excess, and ethics--towards a sustainable distribution model for antibiotics.

    Science.gov (United States)

    Heyman, Gabriel; Cars, Otto; Bejarano, Maria-Teresa; Peterson, Stefan

    2014-05-01

    The increasing antibiotic resistance is a global threat to health care as we know it. Yet there is no model of distribution ready for a new antibiotic that balances access against excessive or inappropriate use in rural settings in low- and middle-income countries (LMICs) where the burden of communicable diseases is high and access to quality health care is low. Departing from a hypothetical scenario of rising antibiotic resistance among pneumococci, 11 stakeholders in the health systems of various LMICs were interviewed one-on-one to give their view on how a new effective antibiotic should be distributed to balance access against the risk of inappropriate use. Transcripts were subjected to qualitative 'framework' analysis. The analysis resulted in four main themes: Barriers to rational access to antibiotics; balancing access and excess; learning from other communicable diseases; and a system-wide intervention. The tension between access to antibiotics and rational use stems from shortcomings found in the health systems of LMICs. Constructing a sustainable yet accessible model of antibiotic distribution for LMICs is a task of health system-wide proportions, which is why we strongly suggest using systems thinking in future research on this issue.

  7. Lattice Model for Production of Gas

    KAUST Repository

    Marder, M.; Eftekhari, Behzad; Patzek, Tadeusz

    2017-01-01

    We define a lattice model for rock, absorbers, and gas that makes it possible to examine the flow of gas to a complicated absorbing boundary over long periods of time. The motivation is to deduce the geometry of the boundary from the time history

  8. Decision support models for natural gas dispatch

    International Nuclear Information System (INIS)

    Chin, L.; Vollmann, T.E.

    1992-01-01

    A decision support model is presented which will give utilities the support tools to manage the purchasing of natural gas supplies in the most cost effective manner without reducing winter safety stocks to below minimum levels. In Business As Usual (BAU) purchasing quantities vary with the daily forecasts. With Material Requirements Planning (MRP) and Linear Programming (LP), two types of factors are used: seasonal weather and decision rule. Under current practices, BAU simulation uses the least expensive gas source first, then adding successively more expensive sources. Material Requirements Planning is a production planning technique which uses a parent item master production schedule to determine time phased requirements for component points. Where the MPS is the aggregate gas demand forecasts for the contract year. This satisfies daily demand with least expensive gas and uses more expensive when necessary with automatic computation of available-to-promise (ATP) gas a dispacher knows daily when extra gas supplies may be ATP. Linear Programming is a mathematical algorithm used to determine optimal allocations of scarce resources to achieve a desired result. The LP model determines optimal daily gas purchase decisions with respect to supply cost minimization. Using these models, it appears possible to raise gross income margins 6 to 10% with minimal additions of customers and no new gas supply

  9. Decision support models for natural gas dispatch

    Energy Technology Data Exchange (ETDEWEB)

    Chin, L. (Bentley College, Waltham, MA (United States)); Vollmann, T.E. (International Inst. for Management Development, Lausanne (Switzerland))

    A decision support model is presented which will give utilities the support tools to manage the purchasing of natural gas supplies in the most cost effective manner without reducing winter safety stocks to below minimum levels. In Business As Usual (BAU) purchasing quantities vary with the daily forecasts. With Material Requirements Planning (MRP) and Linear Programming (LP), two types of factors are used: seasonal weather and decision rule. Under current practices, BAU simulation uses the least expensive gas source first, then adding successively more expensive sources. Material Requirements Planning is a production planning technique which uses a parent item master production schedule to determine time phased requirements for component points. Where the MPS is the aggregate gas demand forecasts for the contract year. This satisfies daily demand with least expensive gas and uses more expensive when necessary with automatic computation of available-to-promise (ATP) gas a dispacher knows daily when extra gas supplies may be ATP. Linear Programming is a mathematical algorithm used to determine optimal allocations of scarce resources to achieve a desired result. The LP model determines optimal daily gas purchase decisions with respect to supply cost minimization. Using these models, it appears possible to raise gross income margins 6 to 10% with minimal additions of customers and no new gas supply.

  10. Computational modeling of intraocular gas dynamics

    International Nuclear Information System (INIS)

    Noohi, P; Abdekhodaie, M J; Cheng, Y L

    2015-01-01

    The purpose of this study was to develop a computational model to simulate the dynamics of intraocular gas behavior in pneumatic retinopexy (PR) procedure. The presented model predicted intraocular gas volume at any time and determined the tolerance angle within which a patient can maneuver and still gas completely covers the tear(s). Computational fluid dynamics calculations were conducted to describe PR procedure. The geometrical model was constructed based on the rabbit and human eye dimensions. SF_6 in the form of pure and diluted with air was considered as the injected gas. The presented results indicated that the composition of the injected gas affected the gas absorption rate and gas volume. After injection of pure SF_6, the bubble expanded to 2.3 times of its initial volume during the first 23 h, but when diluted SF_6 was used, no significant expansion was observed. Also, head positioning for the treatment of retinal tear influenced the rate of gas absorption. Moreover, the determined tolerance angle depended on the bubble and tear size. More bubble expansion and smaller retinal tear caused greater tolerance angle. For example, after 23 h, for the tear size of 2 mm the tolerance angle of using pure SF_6 is 1.4 times more than that of using diluted SF_6 with 80% air. Composition of the injected gas and conditions of the tear in PR may dramatically affect the gas absorption rate and gas volume. Quantifying these effects helps to predict the tolerance angle and improve treatment efficiency. (paper)

  11. Two-state model of excess electron relaxation and geminate recombination in water and aqueous solutions

    International Nuclear Information System (INIS)

    Fedorenko, S.G.

    2010-01-01

    Graphical abstract: After photo-induced ionization a free electron suffers a quick conversion to a solvated state, and then recombines with the parent atom or ion. However, high mobility and reactivity of a free electron can allow the electron to delocalize and recombine in the free state. The theory of two channel processes of geminate electron recombination is developed and applied to the experiment of three-pulse generation of excess electrons in water. - Abstract: After photo-induced ionization a free electron suffers a quick conversion to a solvated state, and then can recombine with the parent atom or ion. However, high mobility and reactivity of a free electron can allow the electron to delocalize and recombine in the free state. The theory of two channel processes of geminate electron recombination is developed here for the general type of the Markovian motion of reactants. A contact model is used for analytical solution of the problem of geminate recombination of neutral and charged reactants. The theory is applied to the experiment of three-pulse generation of excess electrons in water.

  12. Modelling gas generation in radioactive waste repositories

    International Nuclear Information System (INIS)

    Agg, P.J.

    1993-02-01

    In a repository containing low- and intermediate-level waste, gas generation will occur principally by the coupled processes of metal corrosion and microbial degradation of cellulosic waste. This Paper describes a mathematical model design to address gas generation by these mechanisms. The metal corrosion model incorporates a three-stage process encompassing both aerobic and anaerobic corrosion regimes; the microbial degradation model simulates the activities of eight different microbial populations, which are maintained as functions both of pH and of the concentrations of particular chemical species. Gas concentrations have been measured over a period of three years in large-scale drum experiments designed to simulate repository conditions. Model predictions are confirmed against the experimental measurements, and a prediction is then made of gas concentrations and generation rates over an assessment period of one million years in a radioactive waste repository. (author)

  13. Phase transition in the hadron gas model

    International Nuclear Information System (INIS)

    Gorenstein, M.I.; Petrov, V.K.; Zinov'ev, G.M.

    1981-01-01

    A class of statistical models of hadron gas allowing an analytical solution is considered. A mechanism of a possible phase transition in such a system is found and conditions for its occurence are determined [ru

  14. Modelling gas generation in radioactive waste repositories

    International Nuclear Information System (INIS)

    Agg, P.J.

    1992-07-01

    In a repository containing low- and intermediate-level waste, gas generation will occur principally by the coupled processes of metal corrosion and microbial degradation of cellulosic waste. This paper describes a mathematical model designed to address gas generation by these mechanisms. The metal corrosion model incorporates a three-stage process encompassing both aerobic and anaerobic corrosion regimes; the microbial degradation model simulates the activities of eight different microbial populations, which are maintained as functions both of pH and of the concentrations of particular chemical species. Gas concentrations have been measured over a period of three years in large-scale drum experiments designed to simulate repository conditions. Model predictions are confirmed against the experimental measurements, and a prediction is then made of gas concentrations and generation rates over an assessment period of one million years in a radioactive waste repository. (Author)

  15. Natural gas supply in Denmark - A model of natural gas transmission and the liberalized gas market

    International Nuclear Information System (INIS)

    Bregnbaek, L.

    2005-01-01

    In the wake of the liberalization of European energy markets a large area of research has spawned. This area includes the development of mathematical models to analyze the impact of liberalization with respect to efficiency, supply security and environment, to name but a few subjects. This project describes the development of such a model. In Denmark the parallel liberalization of the markets of natural gas and electricity and the existence of an abundance of de-centralized combined heat and power generators of which most are natural gas fired, leads to the natural assumption that the future holds a greater deal of interdependency for these markets. A model is developed describing network flows in the natural gas transmission system, the main arteries of natural gas supply, from a technical viewpoint. This yields a technical bounding on the supply available in different parts of the country. Additionally the economic structure of the Danish natural gas market is formulated mathematically giving a description of the transmission, distribution and storage options available to the market. The supply and demand of natural gas is put into a partial equilibrium context by integrating the developed model with the Balmorel model, which describes the markets for electricity and district heat. Specifically on the demand side the consumption of natural gas for heat and power generation is emphasized. General results and three demonstration cases are presented to illustrate how the developed model can be used to analyze various energy policy issues, and to disclose the strengths and weaknesses in the formulation. (au)

  16. 77 FR 5472 - Pipeline Safety: Expanding the Use of Excess Flow Valves in Gas Distribution Systems to...

    Science.gov (United States)

    2012-02-03

    ..., Regulatory Certainty, and Job Creation Act of 2011 (PL112-90), have imposed additional demands on their... DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration 49 CFR Part 192 [Docket ID PHMSA-2011-0009] RIN 2137-AE71 Pipeline Safety: Expanding the Use of Excess Flow Valves...

  17. Theoretical models for recombination in expanding gas

    International Nuclear Information System (INIS)

    Avron, Y.; Kahane, S.

    1978-09-01

    In laser isotope separation of atomic uranium, one is confronted with the theoretical problem of estimating the concentration of thermally ionized uranium atoms. To investigate this problem theoretical models for recombination in an expanding gas and in the absence of local thermal equilibrium have been constructed. The expansion of the gas is described by soluble models of the hydrodynamic equation, and the recombination by rate equations. General results for the freezing effect for the suitable ranges of the gas parameters are obtained. The impossibility of thermal equilibrium in expanding two-component systems is proven

  18. Description of the Lewin Natural Gas Model

    International Nuclear Information System (INIS)

    Kuuskraa, V.; Godec, M.

    1989-01-01

    This paper provides a brief description of the Lewin Natural Gas Model, shows how this model differs in key features from the other models participating in EMF-9, and describes how the different modeling scenarios analyzed in EMF-9 were implemented in the Lewin model. This background helps explain the key results that have been gained from applying the Lewin model to the EMF scenarios

  19. Modelling emissions from natural gas flaring

    Directory of Open Access Journals (Sweden)

    G. Ezaina Umukoro

    2017-04-01

    Full Text Available The world today recognizes the significance of environmental sustainability to the development of nations. Hence, the role oil and gas industry plays in environmental degrading activities such as gas flaring is of global concern. This study presents material balance equations and predicts results for non-hydrocarbon emissions such as CO2, CO, NO, NO2, and SO2 etc. from flaring (combustion of 12 natural gas samples representing composition of natural gas of global origin. Gaseous emission estimates and pattern were modelled by coding material balance equations for six reaction types and combustion conditions with a computer program. On the average, anticipated gaseous emissions from flaring natural gas with an average annual global flaring rate 126 bcm per year (between 2000 and 2011 in million metric tonnes (mmt are 560 mmt, 48 mmt, 91 mmt, 93 mmt and 50 mmt for CO2, CO, NO, NO2 and SO2 respectively. This model predicted gaseous emissions based on the possible individual combustion types and conditions anticipated in gas flaring operation. It will assist in the effort by environmental agencies and all concerned to track and measure the extent of environmental pollution caused by gas flaring operations in the oil and gas industry.

  20. Adsorption Model for Off-Gas Separation

    Energy Technology Data Exchange (ETDEWEB)

    Veronica J. Rutledge

    2011-03-01

    The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed in gPROMS software. Inputs include gas stream constituents, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. It models dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions for a multiple component gas stream. The simulation outputs component concentrations along the column length as a function of time from which the breakthrough data is obtained. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data will be input into the adsorption model to develop a model specific for iodine adsorption on silver mordenite as well as model(s) specific for krypton and xenon adsorption. The model will be validated with experimental breakthrough curves. Another future off-gas modeling goal is to develop a model for the unit operation absorption. The off-gas models will be made available via the server or web for evaluation by customers.

  1. Excesses of muon g−2, RD(⁎, and RK(⁎ in a leptoquark model

    Directory of Open Access Journals (Sweden)

    Chuan-Hung Chen

    2017-11-01

    Full Text Available In this study, we investigate muon g−2, RK(⁎, and RD(⁎ anomalies in a specific model with one doublet, one triplet, and one singlet scalar leptoquark (LQ. When the strict limits from the ℓ′→ℓγ, ΔB=2, Bs→μ+μ−, and B+→K+νν¯ processes are considered, it is difficult to use one scalar LQ to explain all of the anomalies due to the strong correlations among the constraints and observables. After ignoring the constraints and small couplings, the muon g−2 can be explained by the doublet LQ alone due to the mt enhancement, whereas the measured and unexpected smaller RK(⁎ requires the combined effects of the doublet and triplet LQs, and the RD and RD⁎ excesses depend on the singlet LQ through scalar- and tensor-type interactions.

  2. Integrated economic and life cycle assessment of thermochemical production of bioethanol to reduce production cost by exploiting excess of greenhouse gas savings

    International Nuclear Information System (INIS)

    Reyes Valle, C.; Villanueva Perales, A.L.; Vidal-Barrero, F.; Ollero, P.

    2015-01-01

    Highlights: • Assessment of economics and sustainability of thermochemical ethanol production. • Exploitation of excess CO 2 saving by either importing fossil energy or CO 2 trading. • Significant increase in alcohol production by replacing biomass with natural gas. • CO 2 emission trading is not cost-competitive versus import of fossil energy. • Lowest ethanol production cost for partial oxidation as reforming technology. - Abstract: In this work, two options are investigated to enhance the economics of the catalytic production of bioethanol from biomass gasification by exploiting the excess of CO 2 emission saving: (i) to import fossil energy, in the form of natural gas and electricity or (ii) to trade CO 2 emissions. To this end, an integrated life cycle and economic assessment is carried out for four process configurations, each using a different light hydrocarbon reforming technology: partial oxidation, steam methane reforming, tar reforming and autothermal reforming. The results show that for all process configurations the production of bioethanol and other alcohols significantly increases when natural gas displaces biomass, maintaining the total energy content of the feedstock. The economic advantage of the partial substitution of biomass by natural gas depends on their prices and this is explored by carrying out a sensitivity analysis, taking historical prices into account. It is also concluded that the trade of CO 2 emissions is not cost-competitive compared to the import of natural gas if the CO 2 emission price remains within historical European prices. The CO 2 emission price would have to double or even quadruple the highest CO 2 historical price for CO 2 emission trading to be a cost-competitive option

  3. Combustion modeling in advanced gas turbine systems

    Energy Technology Data Exchange (ETDEWEB)

    Smoot, L.D.; Hedman, P.O.; Fletcher, T.H. [Brigham Young Univ., Provo, UT (United States)] [and others

    1995-10-01

    The goal of the U.S. Department of Energy`s Advanced Turbine Systems (ATS) program is to help develop and commercialize ultra-high efficiency, environmentally superior, and cost competitive gas turbine systems for base-load applications in the utility, independent power producer, and industrial markets. Combustion modeling, including emission characteristics, has been identified as a needed, high-priority technology by key professionals in the gas turbine industry.

  4. On modelling the market for natural gas

    International Nuclear Information System (INIS)

    Mathiesen, Lars

    2001-12-01

    Several features may separately or in combination influence conduct and performance of an industry, e.g. the numbers of sellers or buyers, the degree of economies of scale in production and distribution, the temporal and spatial dimensions, etc. Our main focus is on how to model market power. In particular, we demonstrate the rather different solutions obtained from the price-taking behavior versus the oligopolistic Coumot behavior. We also consider two approaches to model the transportation of natural gas. Finally, there is a brief review of previous modeling efforts of the European natural gas industry. (author)

  5. Gas Modelling in the Disc of HD 163296

    Science.gov (United States)

    Tilling, I.; Woitke, P.; Meeus, G.; Mora, A.; Montesinos, B.; Riviere-Marichalar, P.; Eiroa, C.; Thi, W. -F.; Isella, A.; Roberge, A.; hide

    2011-01-01

    We present detailed model fits to observations of the disc around the Herbig Ae star HD 163296. This well-studied object has an age of approx. 4Myr, with evidence of a circumstellar disc extending out to approx. 540AU. We use the radiation thermo-chemical disc code ProDiMo to model the gas and dust in the circumstellar disc of HD 163296, and attempt to determine the disc properties by fitting to observational line and continuum data. These include new Herschel/PACS observations obtained as part of the open-time key program GASPS (Gas in Protoplanetary Systems), consisting of a detection of the [Oi] 63 m line and upper limits for several other far infrared lines. We complement this with continuum data and ground-based observations of the CO-12 3-2, 2-1 and CO-13 J=1-0 line transitions, as well as the H2 S(1) transition. We explore the effects of stellar ultraviolet variability and dust settling on the line emission, and on the derived disc properties. Our fitting efforts lead to derived gas/dust ratios in the range 9-100, depending on the assumptions made. We note that the line fluxes are sensitive in general to the degree of dust settling in the disc, with an increase in line flux for settled models. This is most pronounced in lines which are formed in the warm gas in the inner disc, but the low excitation molecular lines are also affected. This has serious implications for attempts to derive the disc gas mass from line observations. We derive fractional PAH abundances between 0.007 and 0.04 relative to ISM levels. Using a stellar and UV excess input spectrum based on a detailed analysis of observations, we find that the all observations are consistent with the previously assumed disc geometry

  6. Flow Management to Control Excessive Growth of Macrophytes - An Assessment Based on Habitat Suitability Modeling.

    Science.gov (United States)

    Ochs, Konstantin; Rivaes, Rui P; Ferreira, Teresa; Egger, Gregory

    2018-01-01

    Mediterranean rivers in intensive agricultural watersheds usually display outgrowths of macrophytes - notably alien species - due to a combination of high concentrations of nutrients in the water runoff and low flows resulting from water abstraction for irrigation. Standard mechanical and chemical control is used to mitigate the problems associated with excessive growth of plant biomass: mainly less drainage capacity and higher flood risk. However, such control measures are cost and labor-intensive and do not present long-term efficiency. Although the high sensitivity of aquatic vegetation to instream hydraulic conditions is well known, management approaches based on flow management remain relatively unexplored. The aim of our study was therefore to apply physical habitat simulation techniques promoted by the Instream Flow Incremental Method (IFIM) to aquatic macrophytes - the first time it has been applied in this context - in order to model shifts in habitat suitability under different flow scenarios in the Sorraia river in central Portugal. We used this approach to test whether the risk of invasion and channel encroachment by nuisance species can be controlled by setting minimum annual flows. We used 960 randomly distributed survey points to analyze the habitat suitability for the most important aquatic species (including the invasive Brazilian milfoil Myriophyllum aquaticum , Sparganium erectum , and Potamogeton crispus ) in regard to the physical parameters 'flow velocity,' 'water depth,' and 'substrate size'. We chose the lowest discharge period of the year in order to assess the hydraulic conditions while disturbances were at a low-point, thus allowing aquatic vegetation establishment and subsistence. We then used the two-dimensional hydraulic River2D software to model the potential habitat availability for different flow conditions based on the site-specific habitat suitability index for each physical parameter and species. Our results show that the growth

  7. Flow Management to Control Excessive Growth of Macrophytes – An Assessment Based on Habitat Suitability Modeling

    Science.gov (United States)

    Ochs, Konstantin; Rivaes, Rui P.; Ferreira, Teresa; Egger, Gregory

    2018-01-01

    Mediterranean rivers in intensive agricultural watersheds usually display outgrowths of macrophytes – notably alien species – due to a combination of high concentrations of nutrients in the water runoff and low flows resulting from water abstraction for irrigation. Standard mechanical and chemical control is used to mitigate the problems associated with excessive growth of plant biomass: mainly less drainage capacity and higher flood risk. However, such control measures are cost and labor-intensive and do not present long-term efficiency. Although the high sensitivity of aquatic vegetation to instream hydraulic conditions is well known, management approaches based on flow management remain relatively unexplored. The aim of our study was therefore to apply physical habitat simulation techniques promoted by the Instream Flow Incremental Method (IFIM) to aquatic macrophytes – the first time it has been applied in this context – in order to model shifts in habitat suitability under different flow scenarios in the Sorraia river in central Portugal. We used this approach to test whether the risk of invasion and channel encroachment by nuisance species can be controlled by setting minimum annual flows. We used 960 randomly distributed survey points to analyze the habitat suitability for the most important aquatic species (including the invasive Brazilian milfoil Myriophyllum aquaticum, Sparganium erectum, and Potamogeton crispus) in regard to the physical parameters ‘flow velocity,’ ‘water depth,’ and ‘substrate size’. We chose the lowest discharge period of the year in order to assess the hydraulic conditions while disturbances were at a low-point, thus allowing aquatic vegetation establishment and subsistence. We then used the two-dimensional hydraulic River2D software to model the potential habitat availability for different flow conditions based on the site-specific habitat suitability index for each physical parameter and species. Our results show

  8. A Physically Based Analytical Model to Describe Effective Excess Charge for Streaming Potential Generation in Water Saturated Porous Media

    Science.gov (United States)

    Guarracino, L.; Jougnot, D.

    2018-01-01

    Among the different contributions generating self-potential, the streaming potential is of particular interest in hydrogeology for its sensitivity to water flow. Estimating water flux in porous media using streaming potential data relies on our capacity to understand, model, and upscale the electrokinetic coupling at the mineral-solution interface. Different approaches have been proposed to predict streaming potential generation in porous media. One of these approaches is the flux averaging which is based on determining the excess charge which is effectively dragged in the medium by water flow. In this study, we develop a physically based analytical model to predict the effective excess charge in saturated porous media using a flux-averaging approach in a bundle of capillary tubes with a fractal pore size distribution. The proposed model allows the determination of the effective excess charge as a function of pore water ionic concentration and hydrogeological parameters like porosity, permeability, and tortuosity. The new model has been successfully tested against different set of experimental data from the literature. One of the main findings of this study is the mechanistic explanation to the empirical dependence between the effective excess charge and the permeability that has been found by several researchers. The proposed model also highlights the link to other lithological properties, and it is able to reproduce the evolution of effective excess charge with electrolyte concentrations.

  9. A SIMULATION MODEL OF THE GAS COMPLEX

    Directory of Open Access Journals (Sweden)

    Sokolova G. E.

    2016-06-01

    Full Text Available The article considers the dynamics of gas production in Russia, the structure of sales in the different market segments, as well as comparative dynamics of selling prices on these segments. Problems of approach to the creation of the gas complex using a simulation model, allowing to estimate efficiency of the project and determine the stability region of the obtained solutions. In the presented model takes into account the unit repayment of the loan, allowing with the first year of simulation to determine the possibility of repayment of the loan. The model object is a group of gas fields, which is determined by the minimum flow rate above which the project is cost-effective. In determining the minimum source flow rate for the norm of discount is taken as a generalized weighted average percentage on debt and equity taking into account risk premiums. He also serves as the lower barrier to internal rate of return below which the project is rejected as ineffective. Analysis of the dynamics and methods of expert evaluation allow to determine the intervals of variation of the simulated parameters, such as the price of gas and the exit gas complex at projected capacity. Calculated using the Monte Carlo method, for each random realization of the model simulated values of parameters allow to obtain a set of optimal for each realization of values minimum yield of wells, and also allows to determine the stability region of the solution.

  10. New model of universal gas-filled neutron tube

    International Nuclear Information System (INIS)

    Bespalov, D.F.; Bessarabskii, I.G.; Voitsik, L.R.; Mints, A.Z.

    1985-01-01

    The UNG-1 gas-filled neutron tube is serially produced. In type UNG neutron generators, the tube operates in the pulsed mode in the high voltage doubling circuit arrangement. During extended operation, its advantages were discovered: long operating time, fairly stable neutron yield, and simplicity of use and operation. However, the mean neutron yield (approx.10 7 s -1 ) generated by the tube in the optimal mode at the present time proved to be inadequate in solving numerous geophysical problems. So a model of a neutron tube, model UNG-2, was designed, ensuring an enhanced neutron yield of 10 8 s -1 in the continuous-operating mode. When the tube is connected to the high voltage doubling circuit, the mean neutron yield is only somewhat in excess of the neutron yield from the UNG-1 tube

  11. Geochemical modeling of magmatic gas scrubbing

    Directory of Open Access Journals (Sweden)

    B. Gambardella

    2005-06-01

    Full Text Available The EQ3/6 software package, version 7.2 was successfully used to model scrubbing of magmatic gas by pure water at 0.1 MPa, in the liquid and liquid-plus-gas regions. Some post-calculations were necessary to account for gas separation effects. In these post-calculations, redox potential was considered to be fixed by precipitation of crystalline a-sulfur, a ubiquitous and precocious process. As geochemical modeling is constrained by conservation of enthalpy upon water-gas mixing, the enthalpies of the gas species of interest were reviewed, adopting as reference state the liquid phase at the triple point. Our results confirm that significant emissions of highly acidic gas species (SO2(g, HCl(g, and HF(g are prevented by scrubbing, until dry conditions are established, at least locally. Nevertheless important outgassing of HCl(g can take place from acid, HCl-rich brines. Moreover, these findings support the rule of thumb which is generally used to distinguish SO2-, HCl-, and HF-bearing magmatic gases from SO2-, HCl-, and HF-free hydrothermal gases.

  12. Characterization of Mixtures. Part 2: QSPR Models for Prediction of Excess Molar Volume and Liquid Density Using Neural Networks.

    Science.gov (United States)

    Ajmani, Subhash; Rogers, Stephen C; Barley, Mark H; Burgess, Andrew N; Livingstone, David J

    2010-09-17

    In our earlier work, we have demonstrated that it is possible to characterize binary mixtures using single component descriptors by applying various mixing rules. We also showed that these methods were successful in building predictive QSPR models to study various mixture properties of interest. Here in, we developed a QSPR model of an excess thermodynamic property of binary mixtures i.e. excess molar volume (V(E) ). In the present study, we use a set of mixture descriptors which we earlier designed to specifically account for intermolecular interactions between the components of a mixture and applied successfully to the prediction of infinite-dilution activity coefficients using neural networks (part 1 of this series). We obtain a significant QSPR model for the prediction of excess molar volume (V(E) ) using consensus neural networks and five mixture descriptors. We find that hydrogen bond and thermodynamic descriptors are the most important in determining excess molar volume (V(E) ), which is in line with the theory of intermolecular forces governing excess mixture properties. The results also suggest that the mixture descriptors utilized herein may be sufficient to model a wide variety of properties of binary and possibly even more complex mixtures. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Modeling internal ballistics of gas combustion guns.

    Science.gov (United States)

    Schorge, Volker; Grossjohann, Rico; Schönekess, Holger C; Herbst, Jörg; Bockholdt, Britta; Ekkernkamp, Axel; Frank, Matthias

    2016-05-01

    Potato guns are popular homemade guns which work on the principle of gas combustion. They are usually constructed for recreational rather than criminal purposes. Yet some serious injuries and fatalities due to these guns are reported. As information on the internal ballistics of homemade gas combustion-powered guns is scarce, it is the aim of this work to provide an experimental model of the internal ballistics of these devices and to investigate their basic physical parameters. A gas combustion gun was constructed with a steel tube as the main component. Gas/air mixtures of acetylene, hydrogen, and ethylene were used as propellants for discharging a 46-mm caliber test projectile. Gas pressure in the combustion chamber was captured with a piezoelectric pressure sensor. Projectile velocity was measured with a ballistic speed measurement system. The maximum gas pressure, the maximum rate of pressure rise, the time parameters of the pressure curve, and the velocity and path of the projectile through the barrel as a function of time were determined according to the pressure-time curve. The maximum gas pressure was measured to be between 1.4 bar (ethylene) and 4.5 bar (acetylene). The highest maximum rate of pressure rise was determined for hydrogen at (dp/dt)max = 607 bar/s. The muzzle energy was calculated to be between 67 J (ethylene) and 204 J (acetylene). To conclude, this work provides basic information on the internal ballistics of homemade gas combustion guns. The risk of injury to the operator or bystanders is high, because accidental explosions of the gun due to the high-pressure rise during combustion of the gas/air mixture may occur.

  14. Gas analysis modeling system forecast for the Energy Modeling Forum North American Natural Gas Market Study

    International Nuclear Information System (INIS)

    Mariner-Volpe, B.; Trapmann, W.

    1989-01-01

    The Gas Analysis Modeling System is a large computer-based model for analyzing the complex US natural gas industry, including production, transportation, and consumption activities. The model was developed and first used in 1982 after the passage of the NGPA, which initiated a phased decontrol of most natural gas prices at the wellhead. The categorization of gas under the NGPA and the contractual nature of the natural gas market, which existed at the time, were primary factors in the development of the basic structure of the model. As laws and regulations concerning the natural gas market have changed, the model has evolved accordingly. Recent increases in competition in the wellhead market have also led to changes in the model. GAMS produces forecasts of natural gas production, consumption, and prices annually through 2010. It is an engineering-economic model that incorporates several different mathematical structures in order to represent the interaction of the key groups involved in the natural gas market. GAMS has separate supply and demand components that are equilibrated for each year of the forecast by means of a detailed transaction network

  15. The development of multi-objective optimization model for excess bagasse utilization: A case study for Thailand

    International Nuclear Information System (INIS)

    Buddadee, Bancha; Wirojanagud, Wanpen; Watts, Daniel J.; Pitakaso, Rapeepan

    2008-01-01

    In this paper, a multi-objective optimization model is proposed as a tool to assist in deciding for the proper utilization scheme of excess bagasse produced in sugarcane industry. Two major scenarios for excess bagasse utilization are considered in the optimization. The first scenario is the typical situation when excess bagasse is used for the onsite electricity production. In case of the second scenario, excess bagasse is processed for the offsite ethanol production. Then the ethanol is blended with an octane rating of 91 gasoline by a portion of 10% and 90% by volume respectively and the mixture is used as alternative fuel for gasoline vehicles in Thailand. The model proposed in this paper called 'Environmental System Optimization' comprises the life cycle impact assessment of global warming potential (GWP) and the associated cost followed by the multi-objective optimization which facilitates in finding out the optimal proportion of the excess bagasse processed in each scenario. Basic mathematical expressions for indicating the GWP and cost of the entire process of excess bagasse utilization are taken into account in the model formulation and optimization. The outcome of this study is the methodology developed for decision-making concerning the excess bagasse utilization available in Thailand in view of the GWP and economic effects. A demonstration example is presented to illustrate the advantage of the methodology which may be used by the policy maker. The methodology developed is successfully performed to satisfy both environmental and economic objectives over the whole life cycle of the system. It is shown in the demonstration example that the first scenario results in positive GWP while the second scenario results in negative GWP. The combination of these two scenario results in positive or negative GWP depending on the preference of the weighting given to each objective. The results on economics of all scenarios show the satisfied outcomes

  16. A Model of Solid State Gas Sensors

    Science.gov (United States)

    Woestman, J. T.; Brailsford, A. D.; Shane, M.; Logothetis, E. M.

    1997-03-01

    Solid state gas sensors are widely used to measure the concentrations of gases such as CO, CH_4, C_3H_6, H_2, C_3H8 and O2 The applications of these sensors range from air-to-fuel ratio control in combustion processes including those in automotive engines and industrial furnaces to leakage detection of inflammable and toxic gases in domestic and industrial environments. As the need increases to accurately measure smaller and smaller concentrations, problems such as poor selectivity, stability and response time limit the use of these sensors. In an effort to overcome some of these limitations, a theoretical model of the transient behavior of solid state gas sensors has been developed. In this presentation, a model for the transient response of an electrochemical gas sensor to gas mixtures containing O2 and one reducing species, such as CO, is discussed. This model accounts for the transport of the reactive species to the sampling electrode, the catalyzed oxidation/reduction reaction of these species and the generation of the resulting electrical signal. The model will be shown to reproduce the results of published steady state models and to agree with experimental steady state and transient data.

  17. Experimental excess molar properties of binary mixtures of (3-amino-1-propanol + isobutanol, 2-propanol) at T = (293.15 to 333.15) K and modelling the excess molar volume by Prigogine–Flory–Patterson theory

    International Nuclear Information System (INIS)

    Kermanpour, F.; Niakan, H.Z.

    2012-01-01

    Highlights: ► Density and viscosity of binary mixtures of propanol derivatives were measured at T = (293.15 to 333.15) K. ► The excess molar properties were calculated from these experimental data and correlated by Redlich–Kister equation. ► The PFP model was applied for correlating the excess molar volumes. - Abstract: Density and viscosity of binary mixtures of (x 1 3-amino-1-propanol + x 2 isobutanol) and (x 1 3-amino-1-propanol + x 2 2-propanol) were measured over the entire composition range and from temperatures (293.15 to 333.15) K at ambient pressure. The excess molar volumes and viscosity deviations were calculated and correlated by the Redlich–Kister (RK) equation. The thermal expansion coefficient and its excess value, isothermal coefficient of excess molar enthalpy, and excess partial molar volumes were determined by using the experimental values of density and are described as a function of composition and temperature. The excess molar volumes are negative over the entire mole fraction range for both mixtures and increase with increasing temperature. The excess molar volumes obtained were correlated by the Prigogine–Flory–Patterson (PFP) model. The viscosity deviations of the binary mixtures are negative over the entire composition range and decrease with increasing temperature.

  18. Fetal programming of adrenal androgen excess: lessons from a nonhuman primate model of polycystic ovary syndrome

    OpenAIRE

    Abbott, David H; Zhou, Rao; Bird, Ian M; Dumesic, Daniel A; Conley, Alan J

    2008-01-01

    Adrenal androgen excess is found in adult female rhesus monkeys previously exposed to androgen treatment during early gestation. In adulthood, such prenatally androgenized female monkeys exhibit elevated basal circulating levels of DHEAS, typical of PCOS women with adrenal androgen excess. Further androgen and glucocorticoid abnormalities in PA female monkeys are revealed by acute ACTH stimulation: DHEA, androstenedione and corticosterone responses are all elevated compared to responses in co...

  19. Simulation Model of Membrane Gas Separator Using Aspen Custom Modeler

    Energy Technology Data Exchange (ETDEWEB)

    Song, Dong-keun [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of); Shin, Gahui; Yun, Jinwon; Yu, Sangseok [Chungnam Nat’l Univ., Daejeon (Korea, Republic of)

    2016-12-15

    Membranes are used to separate pure gas from gas mixtures. In this study, three different types of mass transport through a membrane were developed in order to investigate the gas separation capabilities of a membrane. The three different models typically used are a lumped model, a multi-cell model, and a discretization model. Despite the multi-cell model producing similar results to a discretization model, the discretization model was selected for this investigation, due to the cell number dependence of a multi-cell model. The mass transport model was then used to investigate the effects of pressure difference, flow rate, total exposed area, and permeability. The results showed that the pressure difference increased with the stage cut, but the selectivity was a trade-off for the increasing pressure difference. Additionally, even though permeability is an important parameter, the selectivity and stage cut of the membrane converged as permeability increased.

  20. Testing warm Comptonization models for the origin of the soft X-ray excess in AGNs

    Science.gov (United States)

    Petrucci, P.-O.; Ursini, F.; De Rosa, A.; Bianchi, S.; Cappi, M.; Matt, G.; Dadina, M.; Malzac, J.

    2018-03-01

    The X-ray spectra of many active galactic nuclei (AGNs) show a soft X-ray excess below 1-2 keV on top of the extrapolated high-energy power law. The origin of this component is uncertain. It could be a signature of relativistically blurred, ionized reflection or the high-energy tail of thermal Comptonization in a warm (kT 1 keV), optically thick (τ ≃ 10-20) corona producing the optical/UV to soft X-ray emission. The purpose of the present paper is to test the warm corona model on a statistically significant sample of unabsorbed, radio-quiet AGNs with XMM-Newton archival data, providing simultaneous optical/UV and X-ray coverage. The sample has 22 objects and 100 observations. We use two thermal Comptonization components to fit the broadband spectra, one for the warm corona emission and one for the high-energy continuum. In the optical/UV, we also include the reddening, the small blue bump, and the Galactic extinction. In the X-rays, we include a warm absorber and a neutral reflection. The model gives a good fit (reduced χ2 uniformly distributed in the 0.1-1 keV range, while the optical depth is in the range 10-40. These values are consistent with a warm corona covering a large fraction of a quasi-passive accretion disk, i.e., that mostly reprocesses the warm corona emission. The disk intrinsic emission represents no more than 20% of the disk total emission. According to this interpretation, most of the accretion power would be released in the upper layers of the accretion flow.

  1. Effect of excess dietary salt on calcium metabolism and bone mineral in a spaceflight rat model

    Science.gov (United States)

    Navidi, Meena; Wolinsky, Ira; Fung, Paul; Arnaud, Sara B.

    1995-01-01

    High levels of salt promote urinary calcium (UCa) loss and have the potential to cause bone mineral deficits if intestinal Ca absorption does not compensate for these losses. To determine the effect of excess dietary salt on the osteopenia that follows skeletal unloading, we used a spaceflight model that unloads the hindlimbs of 200-g rats by tail suspension (S). Rats were studied for 2 wk on diets containing high salt (4 and 8%) and normal calcium (0.45%) and for 4 wk on diets containing 8% salt (HiNa) and 0.2% Ca (LoCa). Final body weights were 9-11% lower in S than in control rats (C) in both experiments, reflecting lower growth rates in S than in C during pair feeding. UCa represented 12% of dietary Ca on HiNA diets and was twofold higher in S than in C transiently during unloading. Net intestinal Ca absorption was consistently 11-18% lower in S than in C. Serum 1,25-dihydroxyvitamin D was unaffected by either LoCa or HiNa diets in S but was increased by LoCa and HiNa diets in C. Despite depressed intestinal Ca absoption in S and a sluggish response of the Ca endocrine system to HiNa diets, UCa loss did not appear to affect the osteopenia induced by unloading. Although any deficit in bone mineral content from HiNa diets may have been too small to detect or the duration of the study too short to manifest, there were clear differences in Ca metabolism from control levels in the response of the spaceflight model to HiNa diets, indicated by depression of intestinal Ca absorption and its regulatory hormone.

  2. A physically-based analytical model to describe effective excess charge for streaming potential generation in saturated porous media

    Science.gov (United States)

    Jougnot, D.; Guarracino, L.

    2016-12-01

    The self-potential (SP) method is considered by most researchers the only geophysical method that is directly sensitive to groundwater flow. One source of SP signals, the so-called streaming potential, results from the presence of an electrical double layer at the mineral-pore water interface. When water flows through the pore space, it gives rise to a streaming current and a resulting measurable electrical voltage. Different approaches have been proposed to predict streaming potentials in porous media. One approach is based on the excess charge which is effectively dragged in the medium by the water flow. Following a recent theoretical framework, we developed a physically-based analytical model to predict the effective excess charge in saturated porous media. In this study, the porous media is described by a bundle of capillary tubes with a fractal pore-size distribution. First, an analytical relationship is derived to determine the effective excess charge for a single capillary tube as a function of the pore water salinity. Then, this relationship is used to obtain both exact and approximated expressions for the effective excess charge at the Representative Elementary Volume (REV) scale. The resulting analytical relationship allows the determination of the effective excess charge as a function of pore water salinity, fractal dimension and hydraulic parameters like porosity and permeability, which are also obtained at the REV scale. This new model has been successfully tested against data from the literature of different sources. One of the main finding of this study is that it provides a mechanistic explanation to the empirical dependence between the effective excess charge and the permeability that has been found by various researchers. The proposed petrophysical relationship also contributes to understand the role of porosity and water salinity on effective excess charge and will help to push further the use of streaming potential to monitor groundwater flow.

  3. Modeling U-Shaped Exposure-Response Relationships for Agents that Demonstrate Toxicity Due to Both Excess and Deficiency.

    Science.gov (United States)

    Milton, Brittany; Farrell, Patrick J; Birkett, Nicholas; Krewski, Daniel

    2017-02-01

    Essential elements such as copper and manganese may demonstrate U-shaped exposure-response relationships due to toxic responses occurring as a result of both excess and deficiency. Previous work on a copper toxicity database employed CatReg, a software program for categorical regression developed by the U.S. Environmental Protection Agency, to model copper excess and deficiency exposure-response relationships separately. This analysis involved the use of a severity scoring system to place diverse toxic responses on a common severity scale, thereby allowing their inclusion in the same CatReg model. In this article, we present methods for simultaneously fitting excess and deficiency data in the form of a single U-shaped exposure-response curve, the minimum of which occurs at the exposure level that minimizes the probability of an adverse outcome due to either excess or deficiency (or both). We also present a closed-form expression for the point at which the exposure-response curves for excess and deficiency cross, corresponding to the exposure level at which the risk of an adverse outcome due to excess is equal to that for deficiency. The application of these methods is illustrated using the same copper toxicity database noted above. The use of these methods permits the analysis of all available exposure-response data from multiple studies expressing multiple endpoints due to both excess and deficiency. The exposure level corresponding to the minimum of this U-shaped curve, and the confidence limits around this exposure level, may be useful in establishing an acceptable range of exposures that minimize the overall risk associated with the agent of interest. © 2016 Society for Risk Analysis.

  4. Modeling Greenhouse Gas Emissions from Enteric Fermentation

    NARCIS (Netherlands)

    Kebreab, E.; Tedeschi, L.; Dijkstra, J.; Ellis, J.L.; Bannink, A.; France, J.

    2016-01-01

    Livestock directly contribute to greenhouse gas (GHG) emissions mainly through methane (CH4) and nitrous oxide (N2O) emissions. For cost and practicality reasons, quantification of GHG has been through development of various types of mathematical models. This chapter addresses the utility and

  5. Neutral gas transport modeling with DEGAS 2

    International Nuclear Information System (INIS)

    Karney, C.; Stotler, D.

    1993-01-01

    The authors are currently re-writing the neutral gas transport code, DEGAS, with a view to making it both faster and easier to include new physics. They present model calculations including ionization and charge exchange illustrating the way that reactions are included into DEGAS 2 and its operation on a distributed network of workstations

  6. A strategic model of European gas supply

    International Nuclear Information System (INIS)

    Holz, Franziska; Hirschhausen, Christian von; Kemfert, Claudia

    2005-01-01

    Structural changes in the European natural gas market such as liberalization, increasing demand, and growing import dependency have triggered new attempts to model these markets accurately. This paper proposes a model of the European natural gas supply including the possibility of strategic behavior of the agents along the value-added chain. We structure it as a two-stage-game of successive natural gas exports to Europe (first stage) and wholesale trade within Europe (second stage). In the case of non-cooperative Cournot competition at both stages, which is the most realistic scenario, this yields a market outcome with double marginalization, that is suppliers at both stages generate a mark-up, at the expense of the final customers. Our results suggest that the main suppliers of natural gas to Europe remain dominant (Norway, the Netherlands), although some lose market shares (Algeria, UK, and especially Russia). Traditional exports will be complemented in the future by overseas supplies of LNG from the Middle East, Nigeria, Trinidad and Tobago which are becoming competitive. The model also enables us to identify transport infrastructure bottlenecks; we find that transport capacity on the upstream market is sufficient but the capacity constraint is binding for many intra-EU trade relations. (Author)

  7. Individual Diet Modeling Shows How to Balance the Diet of French Adults with or without Excessive Free Sugar Intakes.

    Science.gov (United States)

    Lluch, Anne; Maillot, Matthieu; Gazan, Rozenn; Vieux, Florent; Delaere, Fabien; Vaudaine, Sarah; Darmon, Nicole

    2017-02-20

    Dietary changes needed to achieve nutritional adequacy for 33 nutrients were determined for 1719 adults from a representative French national dietary survey. For each individual, an iso-energy nutritionally adequate diet was generated using diet modeling, staying as close as possible to the observed diet. The French food composition table was completed with free sugar (FS) content. Results were analyzed separately for individuals with FS intakes in their observed diets ≤10% or >10% of their energy intake (named below FS-ACCEPTABLE and FS-EXCESS, respectively). The FS-EXCESS group represented 41% of the total population (average energy intake of 14.2% from FS). Compared with FS-ACCEPTABLE individuals, FS-EXCESS individuals had diets of lower nutritional quality and consumed more energy (2192 vs. 2123 kcal/day), particularly during snacking occasions (258 vs. 131 kcal/day) (all p -values diets were significant increases in fresh fruits, starchy foods, water, hot beverages and plain yogurts; and significant decreases in mixed dishes/sandwiches, meat/eggs/fish and cheese. For FS-EXCESS individuals only, the optimization process significantly increased vegetables and significantly decreased sugar-sweetened beverages, sweet products and fruit juices. The diets of French adults with excessive intakes of FS are of lower nutritional quality, but can be optimized via specific dietary changes.

  8. Fetal programming of adrenal androgen excess: lessons from a nonhuman primate model of polycystic ovary syndrome.

    Science.gov (United States)

    Abbott, David H; Zhou, Rao; Bird, Ian M; Dumesic, Daniel A; Conley, Alan J

    2008-01-01

    Adrenal androgen excess is found in adult female rhesus monkeys previously exposed to androgen treatment during early gestation. In adulthood, such prenatally androgenized female monkeys exhibit elevated basal circulating levels of dehydroepiandrosterone sulfate (DHEAS), typical of polycystic ovary syndrome (PCOS) women with adrenal androgen excess. Further androgen and glucocorticoid abnormalities in PA female monkeys are revealed by acute ACTH stimulation: DHEA, androstenedione and corticosterone responses are all elevated compared to responses in controls. Pioglitazone treatment, however, diminishes circulating DHEAS responses to ACTH in both prenatally androgenized and control female monkeys, while increasing the 17-hydroxyprogesterone response and reducing the DHEA to 17-hydroxyprogesterone ratio. Since 60-min post-ACTH serum values for 17-hydroxyprogesterone correlate negatively with basal serum insulin levels (all female monkeys on pioglitazone and placebo treatment combined), while similar DHEAS values correlate positively with basal serum insulin levels, circulating insulin levels may preferentially support adrenal androgen biosynthesis in both prenatally androgenized and control female rhesus monkeys. Overall, our findings suggest that differentiation of the monkey adrenal cortex in a hyperandrogenic fetal environment may permanently upregulate adult adrenal androgen biosynthesis through specific elevation of 17,20-lyase activity in the zona fasciculata-reticularis. As adult prenatally androgenized female rhesus monkeys closely emulate PCOS-like symptoms, excess fetal androgen programming may contribute to adult adrenal androgen excess in women with PCOS.

  9. Multisite Interactions in Lattice-Gas Models

    Science.gov (United States)

    Einstein, T. L.; Sathiyanarayanan, R.

    For detailed applications of lattice-gas models to surface systems, multisite interactions often play at least as significant a role as interactions between pairs of adatoms that are separated by a few lattice spacings. We recall that trio (3-adatom, non-pairwise) interactions do not inevitably create phase boundary asymmetries about half coverage. We discuss a sophisticated application to an experimental system and describe refinements in extracting lattice-gas energies from calculations of total energies of several different ordered overlayers. We describe how lateral relaxations complicate matters when there is direct interaction between the adatoms, an issue that is important when examining the angular dependence of step line tensions. We discuss the connector model as an alternative viewpoint and close with a brief account of recent work on organic molecule overlayers.

  10. 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

  11. Managing the reactivity excess of the gas turbine-modular helium reactor by burnable poison and control rods

    International Nuclear Information System (INIS)

    Talamo, Alberto

    2006-01-01

    The gas turbine-modular helium reactor coupled to the deep burn in-core fuel management strategy offers the extraordinary capability to incinerate over 50% of the initial inventory of fissile material. This extraordinary feature, coming from an advanced and well tested fuel element design, which takes advantage of the TRISO particles technology, is maintained while the reactor is loaded with the most different types of fuels. In the present work, we assumed the reactor operating at the equilibrium of the fuel composition, obtained by a 6 years irradiation of light water reactor waste, and we investigated the effects of the introduction of the burnable poison and the control rods; we equipped the core with all the three types of control rods: operational, startup and shutdown ones. We employed as burnable poison natural erbium, due to the 167 Er increasing neutron capture microscopic cross-section in the energy range where the neutron spectrum exhibits the thermal peak; in addition, we utilized boron carbide, with 90% enrichment in 1 B, as the absorption material of the control rods. Concerning the burnable poison studies, we focused on the k eff value, the 167 Er mass during burnup, the influence of modifying the radius of the BISO particles kernel and the fuel and moderator coefficients of temperature. Concerning the control rods studies, we investigated the reactivity worth, the changes in the neutron flux profile due to a partial insertion, the influence of modifying the radius of the BISO particles kernel and the β eff , at the beginning of the operation

  12. Managing the reactivity excess of the gas turbine-modular helium reactor by burnable poison and control rods

    Energy Technology Data Exchange (ETDEWEB)

    Talamo, Alberto [Department of Nuclear and Reactor Physics, Royal Institute of Technology, Roslagstullsbacken 21, S-10691, Stockholm (Sweden)]. E-mail: alby@neutron.kth.se

    2006-01-15

    The gas turbine-modular helium reactor coupled to the deep burn in-core fuel management strategy offers the extraordinary capability to incinerate over 50% of the initial inventory of fissile material. This extraordinary feature, coming from an advanced and well tested fuel element design, which takes advantage of the TRISO particles technology, is maintained while the reactor is loaded with the most different types of fuels. In the present work, we assumed the reactor operating at the equilibrium of the fuel composition, obtained by a 6 years irradiation of light water reactor waste, and we investigated the effects of the introduction of the burnable poison and the control rods; we equipped the core with all the three types of control rods: operational, startup and shutdown ones. We employed as burnable poison natural erbium, due to the {sup 167}Er increasing neutron capture microscopic cross-section in the energy range where the neutron spectrum exhibits the thermal peak; in addition, we utilized boron carbide, with 90% enrichment in {sup 1}B, as the absorption material of the control rods. Concerning the burnable poison studies, we focused on the k {sub eff} value, the {sup 167}Er mass during burnup, the influence of modifying the radius of the BISO particles kernel and the fuel and moderator coefficients of temperature. Concerning the control rods studies, we investigated the reactivity worth, the changes in the neutron flux profile due to a partial insertion, the influence of modifying the radius of the BISO particles kernel and the {beta} {sub eff}, at the beginning of the operation.

  13. Adrenal hyperandrogenism is induced by fetal androgen excess in a rhesus monkey model of polycystic ovary syndrome.

    Science.gov (United States)

    Zhou, Rao; Bird, Ian M; Dumesic, Daniel A; Abbott, David H

    2005-12-01

    Adrenal androgen excess is found in approximately 25-60% of women with polycystic ovary syndrome (PCOS), but the mechanisms underlying PCOS-related adrenal androgen excess are unclear. The objective of this study was to determine whether adrenal androgen excess is manifest in a nonhuman primate model for PCOS. Six prenatally androgenized (PA) and six control female rhesus monkeys of similar age, body weight, and body mass index were studied during d 2-6 of two menstrual cycles or anovulatory 30-d periods. Predexamethasone adrenal steroid levels were assessed in the first cycle (cycle 1). In a subsequent cycle (cycle 2), occurring one to three cycles after cycle 1, adrenal steroids were determined 14.5-16.0 h after an i.m. injection of 0.5 mg/kg dexamethasone (postdexamethasone levels) and after an i.v. injection of 50 microg ACTH-(1-39). Both before and after dexamethasone, serum levels of dehydroepiandrosterone (DHEA) in PA females exceeded those in controls. After ACTH injection, PA females exhibited higher circulating levels of DHEA, androstenedione, and corticosterone but comparable levels of 17alpha-hydroxyprogesterone, cortisol, the sulfoconjugate of DHEA, and testosterone compared with controls. Enhanced basal and ACTH-stimulated adrenal androgen levels in PA female monkeys may reflect up-regulation of 17,20 lyase activity in the adrenal zona reticularis, causing adrenal androgen excess comparable with that found in PCOS women with adrenal androgen excess. These findings open the possibility that PCOS adrenal hyperandrogenism may have its origins in fetal androgen excess reprogramming of adrenocortical function.

  14. Numerical modeling of fires on gas pipelines

    International Nuclear Information System (INIS)

    Zhao Yang; Jianbo Lai; Lu Liu

    2011-01-01

    When natural gas is released through a hole on a high-pressure pipeline, it disperses in the atmosphere as a jet. A jet fire will occur when the leaked gas meets an ignition source. To estimate the dangerous area, the shape and size of the fire must be known. The evolution of the jet fire in air is predicted by using a finite-volume procedure to solve the flow equations. The model is three-dimensional, elliptic and calculated by using a compressibility corrected version of the k - ξ turbulence model, and also includes a probability density function/laminar flamelet model of turbulent non-premixed combustion process. Radiation heat transfer is described using an adaptive version of the discrete transfer method. The model is compared with the experiments about a horizontal jet fire in a wind tunnel in the literature with success. The influence of wind and jet velocity on the fire shape has been investigated. And a correlation based on numerical results for predicting the stoichiometric flame length is proposed. - Research highlights: → We developed a model to predict the evolution of turbulent jet diffusion flames. → Measurements of temperature distributions match well with the numerical predictions. → A correlation has been proposed to predict the stoichiometric flame length. → Buoyancy effects are higher in the numerical results. → The radiative heat loss is bigger in the experimental results.

  15. Modelling and Simulation of Gas Engines Using Aspen HYSYS

    Directory of Open Access Journals (Sweden)

    M. C. Ekwonu

    2013-12-01

    Full Text Available In this paper gas engine model was developed in Aspen HYSYS V7.3 and validated with Waukesha 16V275GL+ gas engine. Fuel flexibility, fuel types and part load performance of the gas engine were investigated. The design variability revealed that the gas engine can operate on poor fuel with low lower heating value (LHV such as landfill gas, sewage gas and biogas with biogas offering potential integration with bottoming cycles when compared to natural gas. The result of the gas engine simulation gave an efficiency 40.7% and power output of 3592kW.

  16. Interpreting the 750 GeV diphoton excess by the singlet extension of the Manohar-Wise model

    Science.gov (United States)

    Cao, Junjie; Han, Chengcheng; Shang, Liangliang; Su, Wei; Yang, Jin Min; Zhang, Yang

    2016-04-01

    The evidence of a new scalar particle X from the 750 GeV diphoton excess, and the absence of any other signal of new physics at the LHC so far suggest the existence of new colored scalars, which may be moderately light and thus can induce sizable Xgg and Xγγ couplings without resorting to very strong interactions. Motivated by this speculation, we extend the Manohar-Wise model by adding one gauge singlet scalar field. The resulting theory then predicts one singlet dominated scalar ϕ as well as three kinds of color-octet scalars, which can mediate through loops the ϕgg and ϕγγ interactions. After fitting the model to the diphoton data at the LHC, we find that in reasonable parameter regions the excess can be explained at 1σ level by the process gg → ϕ → γγ, and the best points predict the central value of the excess rate with χmin2 = 2.32, which corresponds to a p-value of 0.68. We also consider the constraints from various LHC Run I signals, and we conclude that, although these constraints are powerful in excluding the parameter space of the model, the best points are still experimentally allowed.

  17. Impact of excessive groundwater pumping on rejuvenation processes in the Bandung basin (Indonesia) as determined by hydrogeochemistry and modeling

    Science.gov (United States)

    Taufiq, Ahmad; Hosono, Takahiro; Ide, Kiyoshi; Kagabu, Makoto; Iskandar, Irwan; Effendi, Agus J.; Hutasoit, Lambok M.; Shimada, Jun

    2017-12-01

    In the Bandung basin, Indonesia, excessive groundwater pumping caused by rapid increases in industrialization and population growth has caused subsurface environmental problems, such as excessive groundwater drawdown and land subsidence. In this study, multiple hydrogeochemical techniques and numerical modeling have been applied to evaluate the recharge processes and groundwater age (rejuvenation). Although all the groundwater in the Bandung basin is recharged at the same elevation at the periphery of the basin, the water type and residence time of the shallow and deep groundwater could be clearly differentiated. However, there was significant groundwater drawdown in all the depression areas and there is evidence of groundwater mixing between the shallow and deep groundwater. The groundwater mixing was traced from the high dichlorodifluoromethane (CFC-12) concentrations in some deep groundwater samples and by estimating the rejuvenation ratio (R) in some representative observation wells. The magnitude of CFC-12 concentration, as an indicator of young groundwater, showed a good correlation with R, determined using 14C activity in samples taken between 2008 and 2012. These correlations were confirmed with the estimation of vertical downward flux from shallower to deeper aquifers using numerical modeling. Furthermore, the change in vertical flux is affected by the change in groundwater pumping. Since the 1970s, the vertical flux increased significantly and reached approximately 15% of the total pumping amount during the 2000s, as it compensated the groundwater pumping. This study clearly revealed the processes of groundwater impact caused by excessive groundwater pumping using a combination of hydrogeochemical methods and modeling.

  18. Excessive growth.

    Science.gov (United States)

    Narayanaswamy, Vasudha; Rettig, Kenneth R; Bhowmick, Samar K

    2008-09-01

    Tall stature and excessive growth syndrome are a relatively rare concern in pediatric practice. Nevertheless, it is important to identify abnormal accelerated growth patterns in children, which may be the clue in the diagnosis of an underlying disorder. We present a case of pituitary gigantism in a 2 1/2-year-old child and discuss the signs, symptoms, laboratory findings, and the treatment. Brief discussions on the differential diagnosis of excessive growth/tall stature have been outlined. Pituitary gigantism is very rare in the pediatrics age group; however, it is extremely rare in a child that is less than 3 years of age. The nature of pituitary adenoma and treatment options in children with this condition have also been discussed.

  19. Modeling greenhouse gas emissions from dairy farms.

    Science.gov (United States)

    Rotz, C Alan

    2017-11-15

    Dairy farms have been identified as an important source of greenhouse gas emissions. Within the farm, important emissions include enteric CH 4 from the animals, CH 4 and N 2 O from manure in housing facilities during long-term storage and during field application, and N 2 O from nitrification and denitrification processes in the soil used to produce feed crops and pasture. Models using a wide range in level of detail have been developed to represent or predict these emissions. They include constant emission factors, variable process-related emission factors, empirical or statistical models, mechanistic process simulations, and life cycle assessment. To fully represent farm emissions, models representing the various emission sources must be integrated to capture the combined effects and interactions of all important components. Farm models have been developed using relationships across the full scale of detail, from constant emission factors to detailed mechanistic simulations. Simpler models, based upon emission factors and empirical relationships, tend to provide better tools for decision support, whereas more complex farm simulations provide better tools for research and education. To look beyond the farm boundaries, life cycle assessment provides an environmental accounting tool for quantifying and evaluating emissions over the full cycle, from producing the resources used on the farm through processing, distribution, consumption, and waste handling of the milk and dairy products produced. Models are useful for improving our understanding of farm processes and their interacting effects on greenhouse gas emissions. Through better understanding, they assist in the development and evaluation of mitigation strategies for reducing emissions and improving overall sustainability of dairy farms. The Authors. Published by the Federation of Animal Science Societies and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article

  20. Discussion of gas trade model (GTM) results

    International Nuclear Information System (INIS)

    Manne, A.

    1989-01-01

    This is in response to your invitation to comment on the structure of GTM and also upon the differences between its results and those of other models participating in EMF9. First a word upon the structure. GTM was originally designed to provide both regional and sectoral detail within the North American market for natural gas at a single point in time, e.g. the year 2000. It is a spatial equilibrium model in which a solution is obtained by maximizing a nonlinear function, the sum of consumers and producers surplus. Since transport costs are included in producers cost, this formulation automatically ensures that geographical price differentials will not differ by more than transport costs. For purposes of EMF9, GTM was modified to allow for resource development and depletion over time

  1. Modeling of greenhouse gas emission from livestock

    Directory of Open Access Journals (Sweden)

    Sanjo eJose

    2016-04-01

    Full Text Available The effects of climate change on humans and other living ecosystems is an area of on-going research. The ruminant livestock sector is considered to be one of the most significant contributors to the existing greenhouse gas (GHG pool. However the there are opportunities to combat climate change by reducing the emission of GHGs from ruminants. Methane (CH4 and nitrous oxide (N2O are emitted by ruminants via anaerobic digestion of organic matter in the rumen and manure, and by denitrification and nitrification processes which occur in manure. The quantification of these emissions by experimental methods is difficult and takes considerable time for analysis of the implications of the outputs from empirical studies, and for adaptation and mitigation strategies to be developed. To overcome these problems computer simulation models offer substantial scope for predicting GHG emissions. These models often include all farm activities while accurately predicting the GHG emissions including both direct as well as indirect sources. The models are fast and efficient in predicting emissions and provide valuable information on implementing the appropriate GHG mitigation strategies on farms. Further, these models help in testing the efficacy of various mitigation strategies that are employed to reduce GHG emissions. These models can be used to determine future adaptation and mitigation strategies, to reduce GHG emissions thereby combating livestock induced climate change.

  2. Excessive folate synthesis limits lifespan in the C. elegans: E. coli aging model

    Directory of Open Access Journals (Sweden)

    Virk Bhupinder

    2012-07-01

    Full Text Available Abstract Background Gut microbes influence animal health and thus, are potential targets for interventions that slow aging. Live E. coli provides the nematode worm Caenorhabditis elegans with vital micronutrients, such as folates that cannot be synthesized by animals. However, the microbe also limits C. elegans lifespan. Understanding these interactions may shed light on how intestinal microbes influence mammalian aging. Results Serendipitously, we isolated an E. coli mutant that slows C. elegans aging. We identified the disrupted gene to be aroD, which is required to synthesize aromatic compounds in the microbe. Adding back aromatic compounds to the media revealed that the increased C. elegans lifespan was caused by decreased availability of para-aminobenzoic acid, a precursor to folate. Consistent with this result, inhibition of folate synthesis by sulfamethoxazole, a sulfonamide, led to a dose-dependent increase in C. elegans lifespan. As expected, these treatments caused a decrease in bacterial and worm folate levels, as measured by mass spectrometry of intact folates. The folate cycle is essential for cellular biosynthesis. However, bacterial proliferation and C. elegans growth and reproduction were unaffected under the conditions that increased lifespan. Conclusions In this animal:microbe system, folates are in excess of that required for biosynthesis. This study suggests that microbial folate synthesis is a pharmacologically accessible target to slow animal aging without detrimental effects.

  3. Limitations of heterogeneous models of liquid dynamics: very slow rate exchange in the excess wing.

    Science.gov (United States)

    Samanta, Subarna; Richert, Ranko

    2014-02-07

    For several molecular glass formers, the nonlinear dielectric effects (NDE's) are investigated for the so-called excess wing regime, i.e., for the relatively high frequencies between 10(2) and 10(7) times the peak loss frequency. It is found that significant nonlinear behavior persists across the entire frequency window of this study, and that its magnitude traces the temperature dependence of the activation energy. A time resolved measurement of the dielectric loss at fields up to 480 kV/cm across tens of thousands of periods reveals that it takes an unexpectedly long time for the steady state NDE to develop. For various materials and at different temperatures and frequencies, it is found that the average structural relaxation with time scale τα governs the equilibration of these fast modes that are associated with time constants τ which are up to 10(7) times shorter than τα. It is argued that true indicators of structural relaxation (such as rate exchange and aging) of these fast modes are slaved to macroscopic softening on the time scale of τα, and thus many orders of magnitude slower than the time constant of the mode itself.

  4. Detailed modelling of a flue-gas desulfurisation plant

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, A.; Fueyo, N.; Tomas, A. [University of Zaragoza, Zaragoza (Spain)

    2007-11-15

    This paper presents a CFD model for a flue-gas desulfurisation plant, and its application to an operating plant. The FGD plant is of the wet-scrubber type, with co-current and counter-current sections. The sorbent used is limestone, and, after cleaning the flue gases, the limestone slurry is collected in an oxidation tank for the production of gypsum. The model uses an Eulerian-Eulerian treatment of the multiphase flow in the absorber and the tank. The essential mass-transfer mechanisms (such as SO{sub 2} and O{sub 2} absorption and CO{sub 2} desorption) are accounted for, as are also the main chemical kinetics leading to the formation of gypsum. Given the different nature of the flow in the absorber and tank, two separate simulations are conducted for each of these domains, and the solutions are iteratively coupled through boundary conditions during the calculations. The model is applied to the FGD plant of the Teruel powerstation located in Andorra (Teruel, Spain). The powerstation is fired with a high-sulfur coal (up to 4.5 percent), and the FGD system has been designed for a desulfurisation capacity of 1.4 million N m{sup 3}/hr for a desulfurisation efficiency in excess of 90 percent. Validation of the model is conducted by comparison with available plant data for two design coals and two desulfurisation efficiencies. The model accuracy is reasonable, given the complexity of the aero/hydrodynamical and thermo-chemical phenomena involved.

  5. Reservoir Models for Gas Hydrate Numerical Simulation

    Science.gov (United States)

    Boswell, R.

    2016-12-01

    Scientific and industrial drilling programs have now providing detailed information on gas hydrate systems that will increasingly be the subject of field experiments. The need to carefully plan these programs requires reliable prediction of reservoir response to hydrate dissociation. Currently, a major emphasis in gas hydrate modeling is the integration of thermodynamic/hydrologic phenomena with geomechanical response for both reservoir and bounding strata. However, also critical to the ultimate success of these efforts is the appropriate development of input geologic models, including several emerging issues, including (1) reservoir heterogeneity, (2) understanding of the initial petrophysical characteristics of the system (reservoirs and seals), the dynamic evolution of those characteristics during active dissociation, and the interdependency of petrophysical parameters and (3) the nature of reservoir boundaries. Heterogeneity is ubiquitous aspect of every natural reservoir, and appropriate characterization is vital. However, heterogeneity is not random. Vertical variation can be evaluated with core and well log data; however, core data often are challenged by incomplete recovery. Well logs also provide interpretation challenges, particularly where reservoirs are thinly-bedded due to limitation in vertical resolution. This imprecision will extend to any petrophysical measurements that are derived from evaluation of log data. Extrapolation of log data laterally is also complex, and should be supported by geologic mapping. Key petrophysical parameters include porosity, permeability and it many aspects, and water saturation. Field data collected to date suggest that the degree of hydrate saturation is strongly controlled by/dependant upon reservoir quality and that the ratio of free to bound water in the remaining pore space is likely also controlled by reservoir quality. Further, those parameters will also evolve during dissociation, and not necessary in a simple

  6. Marginalized multilevel hurdle and zero-inflated models for overdispersed and correlated count data with excess zeros.

    Science.gov (United States)

    Kassahun, Wondwosen; Neyens, Thomas; Molenberghs, Geert; Faes, Christel; Verbeke, Geert

    2014-11-10

    Count data are collected repeatedly over time in many applications, such as biology, epidemiology, and public health. Such data are often characterized by the following three features. First, correlation due to the repeated measures is usually accounted for using subject-specific random effects, which are assumed to be normally distributed. Second, the sample variance may exceed the mean, and hence, the theoretical mean-variance relationship is violated, leading to overdispersion. This is usually allowed for based on a hierarchical approach, combining a Poisson model with gamma distributed random effects. Third, an excess of zeros beyond what standard count distributions can predict is often handled by either the hurdle or the zero-inflated model. A zero-inflated model assumes two processes as sources of zeros and combines a count distribution with a discrete point mass as a mixture, while the hurdle model separately handles zero observations and positive counts, where then a truncated-at-zero count distribution is used for the non-zero state. In practice, however, all these three features can appear simultaneously. Hence, a modeling framework that incorporates all three is necessary, and this presents challenges for the data analysis. Such models, when conditionally specified, will naturally have a subject-specific interpretation. However, adopting their purposefully modified marginalized versions leads to a direct marginal or population-averaged interpretation for parameter estimates of covariate effects, which is the primary interest in many applications. In this paper, we present a marginalized hurdle model and a marginalized zero-inflated model for correlated and overdispersed count data with excess zero observations and then illustrate these further with two case studies. The first dataset focuses on the Anopheles mosquito density around a hydroelectric dam, while adolescents' involvement in work, to earn money and support their families or themselves, is

  7. Development of a natural Gas Systems Analysis Model (GSAM)

    International Nuclear Information System (INIS)

    Godec, M.; Haas, M.; Pepper, W.; Rose, J.

    1993-01-01

    Recent dramatic changes in natural gas markets have significant implications for the scope and direction of DOE's upstream as well as downstream natural gas R ampersand D. Open access transportation changes the way gas is bought and sold. The end of the gas deliverability surplus requires increased reserve development above recent levels. Increased gas demand for power generation and other new uses changes the overall demand picture in terms of volumes, locations and seasonality. DOE's Natural Gas Strategic Plan requires that its R ampersand D activities be evaluated for their ability to provide adequate supplies of reasonably priced gas. Potential R ampersand D projects are to be evaluated using a full fuel cycle, benefit-cost approach to estimate likely market impact as well as technical success. To assure R ampersand D projects are evaluated on a comparable basis, METC has undertaken the development of a comprehensive natural gas technology evaluation framework. Existing energy systems models lack the level of detail required to estimate the impact of specific upstream natural gas technologies across the known range of geological settings and likely market conditions. Gas Systems Analysis Model (GSAM) research during FY 1993 developed and implemented this comprehensive, consistent natural gas system evaluation framework. Rather than a isolated research activity, however, GSAM represents the integration of many prior and ongoing natural gas research efforts. When complete, it will incorporate the most current resource base description, reservoir modeling, technology characterization and other geologic and engineering aspects developed through recent METC and industry gas R ampersand D programs

  8. Brownian gas models for extreme-value laws

    International Nuclear Information System (INIS)

    Eliazar, Iddo

    2013-01-01

    In this paper we establish one-dimensional Brownian gas models for the extreme-value laws of Gumbel, Weibull, and Fréchet. A gas model is a countable collection of independent particles governed by common diffusion dynamics. The extreme-value laws are the universal probability distributions governing the affine scaling limits of the maxima and minima of ensembles of independent and identically distributed one-dimensional random variables. Using the recently introduced concept of stationary Poissonian intensities, we construct two gas models whose global statistical structures are stationary, and yield the extreme-value laws: a linear Brownian motion gas model for the Gumbel law, and a geometric Brownian motion gas model for the Weibull and Fréchet laws. The stochastic dynamics of these gas models are studied in detail, and closed-form analytical descriptions of their temporal correlation structures, their topological phase transitions, and their intrinsic first-passage-time fluxes are presented. (paper)

  9. High-Frequency Stimulation at the Subthalamic Nucleus Suppresses Excessive Self-Grooming in Autism-Like Mouse Models.

    Science.gov (United States)

    Chang, Andrew D; Berges, Victoria A; Chung, Sunho J; Fridman, Gene Y; Baraban, Jay M; Reti, Irving M

    2016-06-01

    Approximately one quarter of individuals with an autism spectrum disorder (ASD) display self-injurious behavior (SIB) ranging from head banging to self-directed biting and punching. Sometimes, these behaviors are extreme and unresponsive to pharmacological and behavioral therapies. We have found electroconvulsive therapy (ECT) can produce life-changing results, with more than 90% suppression of SIB frequency. However, these patients typically require frequent maintenance ECT (mECT), as often as every 5 days, to sustain the improvement gained during the acute course. Long-term consequences of such frequent mECT started as early as childhood in some cases are unknown. Accordingly, there is a need for alternative forms of chronic stimulation for these patients. To explore the feasibility of deep brain stimulation (DBS) for intractable SIB seen in some patients with an ASD, we utilized two genetically distinct mouse models demonstrating excessive self-grooming, namely the Viaat-Mecp2(-/y) and Shank3B(-/-) lines, and administered high-frequency stimulation (HFS) via implanted electrodes at the subthalamic nucleus (STN-HFS). We found that STN-HFS significantly suppressed excessive self-grooming in both genetic lines. Suppression occurs both acutely when stimulation is switched on, and persists for several days after HFS is stopped. This effect was not explained by a change in locomotor activity, which was unaffected by STN-HFS. Likewise, social interaction deficits were not corrected by STN-HFS. Our data show STN-HFS suppresses excessive self-grooming in two autism-like mouse models, raising the possibility DBS might be used to treat intractable SIB associated with ASDs. Further studies are required to explore the circuitry engaged by STN-HFS, as well as other potential stimulation sites. Such studies might also yield clues about pathways, which could be modulated by non-invasive stimulatory techniques.

  10. Excess hall effect in epitaxial YBCO film under moderate magnetic fields, approached by renormalized superconducting fluctuations model

    International Nuclear Information System (INIS)

    Puica, I.; Lang, W.; Goeb, W.; Sobolewski, R.

    2002-01-01

    Full text: Measurements of the Hall effect and the resistivity on precisely-patterned YBCO thin film in moderate magnetic fields B from 0.5 to 6 T oriented parallel to the crystallographic c axis reveal a sign reversal of the Hall coefficient for B < 3 T. The data are confronted with the full quantitative expressions given by the renormalized fluctuation model for the excess Hall conductivity. The model offers a satisfactory quantitative approach to the experimental results, for moderate fields and temperatures near the critical region, provided the inhomogeneity of the critical temperature distribution is also taken into account. For lower fields and temperatures, the adequacy of the model is altered by vortex pinning. (author)

  11. Explaining the DAMPE e+e- excess using the Higgs triplet model with a vector dark matter

    Science.gov (United States)

    Chen, Chuan-Hung; Chiang, Cheng-Wei; Nomura, Takaaki

    2018-03-01

    We explain the e+e- excess observed by the DAMPE Collaboration using a dark matter model based upon the Higgs triplet model and an additional hidden S U (2 )X gauge symmetry. Two of the S U (2 )X gauge bosons are stable due to a residual discrete symmetry and serve as the dark matter candidate. We search the parameter space for regions that can explain the observed relic abundance, and compute the flux of e+e- coming from a nearby dark matter subhalo. With the inclusion of background cosmic rays, we show that the model can render a good fit to the entire energy spectrum covering the AMS-02, Fermi-LAT, CALET and DAMPE data.

  12. Computational Models Describing Possible Mechanisms for Generation of Excessive Beta Oscillations in Parkinson's Disease.

    Directory of Open Access Journals (Sweden)

    Alex Pavlides

    2015-12-01

    Full Text Available In Parkinson's disease, an increase in beta oscillations within the basal ganglia nuclei has been shown to be associated with difficulty in movement initiation. An important role in the generation of these oscillations is thought to be played by the motor cortex and by a network composed of the subthalamic nucleus (STN and the external segment of globus pallidus (GPe. Several alternative models have been proposed to describe the mechanisms for generation of the Parkinsonian beta oscillations. However, a recent experimental study of Tachibana and colleagues yielded results which are challenging for all published computational models of beta generation. That study investigated how the presence of beta oscillations in a primate model of Parkinson's disease is affected by blocking different connections of the STN-GPe circuit. Due to a large number of experimental conditions, the study provides strong constraints that any mechanistic model of beta generation should satisfy. In this paper we present two models consistent with the data of Tachibana et al. The first model assumes that Parkinsonian beta oscillation are generated in the cortex and the STN-GPe circuits resonates at this frequency. The second model additionally assumes that the feedback from STN-GPe circuit to cortex is important for maintaining the oscillations in the network. Predictions are made about experimental evidence that is required to differentiate between the two models, both of which are able to reproduce firing rates, oscillation frequency and effects of lesions carried out by Tachibana and colleagues. Furthermore, an analysis of the models reveals how the amplitude and frequency of the generated oscillations depend on parameters.

  13. A simple operational gas release and swelling model. Pt. 1

    International Nuclear Information System (INIS)

    Wood, M.H.; Matthews, J.R.

    1980-01-01

    A new and simple model of fission gas release and swelling has been developed for oxide nuclear fuel under operational conditions. The model, which is to be incorporated into a fuel element behaviour code, is physically based and applicable to fuel at both thermal and fast reactor ratings. In this paper we present that part of the model describing the behaviour of intragranular gas: a future paper will detail the treatment of the grain boundary gas. The results of model calculations are compared with recent experimental observations of intragranular bubble concentrations and sizes, and gas release from fuel irradiated under isothermal conditions. Good agreement is found between experiment and theory. (orig.)

  14. Development of a Gas Systems Analysis Model (GSAM)

    International Nuclear Information System (INIS)

    Becker, A.B.; Pepper, W.J.

    1995-01-01

    Objective of developing this model (GSAM) is to create a comprehensive, nonproprietary, PC-based model of domestic gas industry activity. The system can assess impacts of various changes in the natural gas system in North America; individual and collective impacts due to changes in technology and economic conditions are explicitly modeled in GSAM. Major gas resources are all modeled, including conventional, tight, Devonian Shale, coalbed methane, and low-quality gas sources. The modeling system assesses all key components of the gas industry, including available resources, exploration, drilling, completion, production, and processing practices. Distribution, storage, and utilization of natural gas in a dynamic market-gased analytical structure is assessed. GSAM is designed to provide METC managers with a tool to project impacts of future research, development, and demonstration benefits

  15. Volcano and ship tracks indicate excessive aerosol-induced cloud water increases in a climate model.

    Science.gov (United States)

    Toll, Velle; Christensen, Matthew; Gassó, Santiago; Bellouin, Nicolas

    2017-12-28

    Aerosol-cloud interaction is the most uncertain mechanism of anthropogenic radiative forcing of Earth's climate, and aerosol-induced cloud water changes are particularly poorly constrained in climate models. By combining satellite retrievals of volcano and ship tracks in stratocumulus clouds, we compile a unique observational dataset and confirm that liquid water path (LWP) responses to aerosols are bidirectional, and on average the increases in LWP are closely compensated by the decreases. Moreover, the meteorological parameters controlling the LWP responses are strikingly similar between the volcano and ship tracks. In stark contrast to observations, there are substantial unidirectional increases in LWP in the Hadley Centre climate model, because the model accounts only for the decreased precipitation efficiency and not for the enhanced entrainment drying. If the LWP increases in the model were compensated by the decreases as the observations suggest, its indirect aerosol radiative forcing in stratocumulus regions would decrease by 45%.

  16. Additive effects of dietary glycotoxins and androgen excess on the kidney of a female rat model

    Directory of Open Access Journals (Sweden)

    Sotiria Palimeri

    2016-06-01

    Conclusions: The above mentioned data suggest that dietary glycotoxins, in combination with increased androgen exposure, exert a more profound negative impact on the kidney of an androgenized female rat model that mimics the metabolic characteristics of polycystic ovary syndrome.

  17. Modelling a deep water oil/gas spill under conditions of gas hydrate formation and decomposition

    International Nuclear Information System (INIS)

    Zheng, L.; Yapa, P.D.

    2000-01-01

    A model for the behavior of oil and gas spills at deepwater locations was presented. Such spills are subjected to pressures and temperatures that can convert gases to gas hydrates which are lighter than water. Knowing the state of gases as they rise with the plume is important in predicting the fate of an oil or gas plume released in deepwater. The objective of this paper was to develop a comprehensive jet/plume model which includes computational modules that simulate the gas hydrate formation/decomposition of gas bubbles. This newly developed model is based on the kinetics of hydrate formation and decomposition coupled with mass and heat transfer phenomena. The numerical model was successfully tested using results of experimental data from the Gulf of Mexico. Hydrate formation and decomposition are integrated with an earlier model by Yapa and Zheng for underwater oil or gas jets and plumes. The effects of hydrate on the behavior of an oil or gas plume was simulated to demonstrate the models capabilities. The model results indicate that in addition to thermodynamics, the kinetics of hydrate formation/decomposition should be considered when studying the behavior of oil and gas spills. It was shown that plume behavior changes significantly depending on whether or not the local conditions force the gases to form hydrates. 25 refs., 4 tabs., 12 figs

  18. Modelling combustion reactions for gas flaring and its resulting emissions

    Directory of Open Access Journals (Sweden)

    O. Saheed Ismail

    2016-07-01

    Full Text Available Flaring of associated petroleum gas is an age long environmental concern which remains unabated. Flaring of gas maybe a very efficient combustion process especially steam/air assisted flare and more economical than utilization in some oil fields. However, it has serious implications for the environment. This study considered different reaction types and operating conditions for gas flaring. Six combustion equations were generated using the mass balance concept with varying air and combustion efficiency. These equations were coded with a computer program using 12 natural gas samples of different chemical composition and origin to predict the pattern of emission species from gas flaring. The effect of key parameters on the emission output is also shown. CO2, CO, NO, NO2 and SO2 are the anticipated non-hydrocarbon emissions of environmental concern. Results show that the quantity and pattern of these chemical species depended on percentage excess/deficiency of stoichiometric air, natural gas type, reaction type, carbon mass content, impurities, combustion efficiency of the flare system etc. These emissions degrade the environment and human life, so knowing the emission types, pattern and flaring conditions that this study predicts is of paramount importance to governments, environmental agencies and the oil and gas industry.

  19. GASCAP: Wellhead Gas Productive Capacity Model documentation, June 1993

    International Nuclear Information System (INIS)

    1993-01-01

    The Wellhead Gas Productive Capacity Model (GASCAP) has been developed by EIA to provide a historical analysis of the monthly productive capacity of natural gas at the wellhead and a projection of monthly capacity for 2 years into the future. The impact of drilling, oil and gas price assumptions, and demand on gas productive capacity are examined. Both gas-well gas and oil-well gas are included. Oil-well gas productive capacity is estimated separately and then combined with the gas-well gas productive capacity. This documentation report provides a general overview of the GASCAP Model, describes the underlying data base, provides technical descriptions of the component models, diagrams the system and subsystem flow, describes the equations, and provides definitions and sources of all variables used in the system. This documentation report is provided to enable users of EIA projections generated by GASCAP to understand the underlying procedures used and to replicate the models and solutions. This report should be of particular interest to those in the Congress, Federal and State agencies, industry, and the academic community, who are concerned with the future availability of natural gas

  20. Modelling of hot surface ignition within gas turbines subject to flammable gas in the intake

    DEFF Research Database (Denmark)

    Pedersen, Lea Duedahl; Nielsen, Kenny Krogh; Yin, Chungen

    2017-01-01

    Controlling risks associated with fires and explosions from leaks of flammable fluids at oil and gas facilities is paramount to ensuring safe operations. The gas turbine is a significant potential source of ignition; however, the residual risk is still not adequately understood. A model has been...... but decreases with increase in initial mixture temperature and pressure. The model shows a great potential in reliable prediction of the risk of hot surface ignition within gas turbines in the oil and gas industry. In the future, a dedicated experimental study will be performed not only to improve...

  1. Radicals excess in the retina: A model for light flashes in space

    International Nuclear Information System (INIS)

    Narici, L.; De Martino, A.; Brunetti, V.; Rinaldi, A.; Sannita, W.G.; Paci, M.

    2009-01-01

    The risk due to cosmic radiation is a major issue in planning future missions to the Moon or Mars and would be critical if inadequately addressed. Functional risks must also be considered. The perception of light flashes reported by astronauts in space, and ascribed mostly to the action of ionizing radiation in the eye (retina), is an evidence for radiation functional interaction. No detailed model of the ion/retina interaction is yet available. Here we present the first model for a generation mechanism compatible with light flashes in space, and the results of in vitro tests supporting it. The model can be a common end point for the interactions between ionizing radiation and visual system in space. It would also support the assessment of functional radiation risks in space.

  2. Excess molar volumes of (an alkanol plus a branched chain ether) at the temperature 298.15 K and the application of the ERAS model

    CSIR Research Space (South Africa)

    Letcher, TM

    1997-12-01

    Full Text Available Phase Equilibria 140 (1997) 207-220 The excess molar the temperature volumes of (an alkanol + a branched chain ether) at 298.15 K and the application of the ERAS model Trevor M. Letcher * , Penny U. Govender ? Drpartnwnt... V,,? results presented here, together with the previously reported data for the molar excess enthalpy Hi, has been used to test the Extended Real Associated Solution (ERAS) model. 0 1997 Elsevier Science B.V. Ke...

  3. Macroscopic calculational model of fission gas release from water reactor fuels

    International Nuclear Information System (INIS)

    Uchida, Masaki

    1993-01-01

    Existing models for estimating fission gas release rate usually have fuel temperature as independent variable. Use of fuel temperature, however, often brings an excess ambiguity in the estimation because it is not a rigorously definable quantity as a function of heat generation rate and burnup. To derive a mathematical model that gives gas release rate explicitly as a function of design and operational parameters, the Booth-type diffusional model was modified by changing the character of the diffusion constant from physically meaningful quantity into a mere mathematical parameter, and also changing its temperature dependency into power dependency. The derived formula was found, by proper choice of arbitrary constants, to satisfactorily predict the release rates under a variety of irradiation histories up to a burnup of 60,000 MWd/t. For simple power histories, the equation can be solved analytically by defining several transcendental functions, which enables simple calculation of release rate using graphs. (author)

  4. Gas migration mechanism of saturated dense bentonite and its modeling

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko; Kudo, Koji

    2007-01-01

    In the current concept of repository for nuclear waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside the engineered barrier by anaerobic corrosion of metals used for containers, etc. If the gas generation rate exceeds the diffusion rate of gas molecules inside of the engineered barrier, gas will accumulate in the void space inside of the engineered barrier until its pressure becomes large enough for it to enter the bentonite as a discrete gaseous phase. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Therefore it is necessary to investigate the following subjects: a) Effect of the accumulated gas pressure on surrounding objects such as concrete lining, rock mass. b) Effect of gas breakthrough on the barrier function of bentonite. c) Revealing and modeling gas migration mechanism for overcoming the scale effects in laboratory specimen test. Therefore in this study, gas migration tests for compacted and saturated bentonite to investigate and to model the mechanism of gas migration phenomenon. Firstly, the following conclusions were obtained through by the results of the gas migration tests which are conducted in this study: 1) Bubbles appear in the semitransparent drainage tube at first when the total gas is equal to the initial total axial stress or somewhat smaller. By increasing the gas pressure more, breakthrough of gas migration, which is defined as a sudden increase of amount of emission gas, occurred. When the total gas pressure exceeds the initial total axial stress, the total axial stress is always equal to the total gas pressure because specimens shrink in the axial direction with causing the clearance between the end of the specimen and porous metal. 2) Effective gas conductivity after breakthrough of gas migration is times larger than that

  5. Influence of georeference for saturated excess overland flow modelling using 3D volumetric soft geo-objects

    Science.gov (United States)

    Izham, Mohamad Yusoff; Muhamad Uznir, Ujang; Alias, Abdul Rahman; Ayob, Katimon; Wan Ruslan, Ismail

    2011-04-01

    Existing 2D data structures are often insufficient for analysing the dynamism of saturation excess overland flow (SEOF) within a basin. Moreover, all stream networks and soil surface structures in GIS must be preserved within appropriate projection plane fitting techniques known as georeferencing. Inclusion of 3D volumetric structure of the current soft geo-objects simulation model would offer a substantial effort towards representing 3D soft geo-objects of SEOF dynamically within a basin by visualising saturated flow and overland flow volume. This research attempts to visualise the influence of a georeference system towards the dynamism of overland flow coverage and total overland flow volume generated from the SEOF process using VSG data structure. The data structure is driven by Green-Ampt methods and the Topographic Wetness Index (TWI). VSGs are analysed by focusing on spatial object preservation techniques of the conformal-based Malaysian Rectified Skew Orthomorphic (MRSO) and the equidistant-based Cassini-Soldner projection plane under the existing geodetic Malaysian Revised Triangulation 1948 (MRT48) and the newly implemented Geocentric Datum for Malaysia (GDM2000) datum. The simulated result visualises deformation of SEOF coverage under different georeference systems via its projection planes, which delineate dissimilar computation of SEOF areas and overland flow volumes. The integration of Georeference, 3D GIS and the saturation excess mechanism provides unifying evidence towards successful landslide and flood disaster management through envisioning the streamflow generating process (mainly SEOF) in a 3D environment.

  6. Excess Properties of Aqueous Mixtures of Methanol: Simple Models Versus Experiment

    Czech Academy of Sciences Publication Activity Database

    Vlček, Lukáš; Nezbeda, Ivo

    roč. 131-132, - (2007), s. 158-162 ISSN 0167-7322. [International Conference on Solution Chemistry /29./. Portorož, 21.08.2005-25.08.2005] R&D Projects: GA AV ČR(CZ) IAA4072303; GA AV ČR(CZ) 1ET400720409 Institutional research plan: CEZ:AV0Z40720504 Keywords : aqueous mixtures * primitive models * water-alcohol mixtures Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.982, year: 2007

  7. Porter Five Forces Model Pada PT. Ruci Gas

    OpenAIRE

    Riky, Alfonsus

    2014-01-01

    Penelitian ini akan membahas mengenai analisis lima model utama kekuatan Porter pada Perusahaan keluarga PT.Ruci Gas. Tujuan dari penelitian ini penulis ingin menganalis tentang struktur industri PT. Ruci Gas yang dikaitkan dengan teori lima model kekuatan utama yang dikembangkan oleh Porter. Selain itu penulis ingin menganalisis mengenai tingkat atraktif investasi gas di Indonesia. Jenis dari penelitian ini adalah kualitatif deskriptif.Dengan pengumpulan data dengan metode wawancara dan obse...

  8. Adjusting for overdispersion in piecewise exponential regression models to estimate excess mortality rate in population-based research.

    Science.gov (United States)

    Luque-Fernandez, Miguel Angel; Belot, Aurélien; Quaresma, Manuela; Maringe, Camille; Coleman, Michel P; Rachet, Bernard

    2016-10-01

    In population-based cancer research, piecewise exponential regression models are used to derive adjusted estimates of excess mortality due to cancer using the Poisson generalized linear modelling framework. However, the assumption that the conditional mean and variance of the rate parameter given the set of covariates x i are equal is strong and may fail to account for overdispersion given the variability of the rate parameter (the variance exceeds the mean). Using an empirical example, we aimed to describe simple methods to test and correct for overdispersion. We used a regression-based score test for overdispersion under the relative survival framework and proposed different approaches to correct for overdispersion including a quasi-likelihood, robust standard errors estimation, negative binomial regression and flexible piecewise modelling. All piecewise exponential regression models showed the presence of significant inherent overdispersion (p-value regression modelling, with either a quasi-likelihood or robust standard errors, was the best approach as it deals with both, overdispersion due to model misspecification and true or inherent overdispersion.

  9. Coulomb-gas scaling, superfluid films, and the XY model

    International Nuclear Information System (INIS)

    Minnhagen, P.; Nylen, M.

    1985-01-01

    Coulomb-gas-scaling ideas are invoked as a link between the superfluid density of two-dimensional 4 He films and the XY model; the Coulomb-gas-scaling function epsilon(X) is extracted from experiments and is compared with Monte Carlo simulations of the XY model. The agreement is found to be excellent

  10. Fission-gas bubble modeling for LMFBR accidents

    International Nuclear Information System (INIS)

    Ostensen, R.W.

    1977-01-01

    The behavior of fission-gas bubbles in unrestructured oxide fuel can have a dominant effect on the course of a core disruptive accident in an LMFBR. The paper describes a simplified model of bubble behavior and presents results of that model in analyzing the relevant physical assumptions and predicting gas behavior in molten fuel

  11. A weakly compressible formulation for modelling liquid-gas sloshing

    CSIR Research Space (South Africa)

    Heyns, Johan A

    2012-09-01

    Full Text Available This study presents the development and extension of free-surface modelling techniques with the purpose of improving the modelling accuracy for liquid-gas sloshing. Considering high density ratio fluids under low Mach number conditions...

  12. Prospects of type-II seesaw models at future colliders in light of the DAMPE e+e- excess

    Science.gov (United States)

    Sui, Yicong; Zhang, Yongchao

    2018-05-01

    The DAMPE e+e- excess at around 1.4 TeV could be explained in the type-II seesaw model with a scalar dark mater D which is stabilized by a discrete Z2 symmetry. The simplest scenario is the annihilation D D →H++H- followed by the subsequent decay H±±→e±e±, with both the DM and triplet scalars roughly 3 TeV with a small mass splitting. In addition to the Drell-Yan process at future 100 TeV hadron colliders, the doubly charged components could also be produced at lepton colliders like ILC and CLIC in the off shell mode and mediate lepton flavor violating processes e+e-→ℓi±ℓj∓ (with i ≠j ). A wide range of parameter space of the type-II seesaw could be probed, which are well below the current stringent lepton flavor constraints.

  13. Excessive activity of cathepsin K is associated with cartilage defects in a zebrafish model of mucolipidosis II

    Directory of Open Access Journals (Sweden)

    Aaron C. Petrey

    2012-03-01

    The severe pediatric disorder mucolipidosis II (ML-II; also known as I-cell disease is caused by defects in mannose 6-phosphate (Man-6-P biosynthesis. Patients with ML-II exhibit multiple developmental defects, including skeletal, craniofacial and joint abnormalities. To date, the molecular mechanisms that underlie these clinical manifestations are poorly understood. Taking advantage of a zebrafish model of ML-II, we previously showed that the cartilage morphogenesis defects in this model are associated with altered chondrocyte differentiation and excessive deposition of type II collagen, indicating that aspects of development that rely on proper extracellular matrix homeostasis are sensitive to decreases in Man-6-P biosynthesis. To further investigate the molecular bases for the cartilage phenotypes, we analyzed the transcript abundance of several genes in chondrocyte-enriched cell populations isolated from wild-type and ML-II zebrafish embryos. Increased levels of cathepsin and matrix metalloproteinase (MMP transcripts were noted in ML-II cell populations. This increase in transcript abundance corresponded with elevated and sustained activity of several cathepsins (K, L and S and MMP-13 during early development. Unlike MMP-13, for which higher levels of protein were detected, the sustained activity of cathepsin K at later stages seemed to result from its abnormal processing and activation. Inhibition of cathepsin K activity by pharmacological or genetic means not only reduced the activity of this enzyme but led to a broad reduction in additional protease activity, significant correction of the cartilage morphogenesis phenotype and reduced type II collagen staining in ML-II embryos. Our findings suggest a central role for excessive cathepsin K activity in the developmental aspects of ML-II cartilage pathogenesis and highlight the utility of the zebrafish system to address the biochemical underpinnings of metabolic disease.

  14. Stability and special solutions to the conducting dusty gas model

    International Nuclear Information System (INIS)

    Calmelet, C.J.

    1987-01-01

    Models of the flow of a dusty, conducting and non-conducting gas are examined. Exact solutions for a conducting dusty gas model in the presence of a magnetic field are developed for two different flow domains. The exact solutions are calculated in the cases of negligible and non-negligible induced magnetic field. Stability theorems are developed which depend on the flow parameters of the dusty gas and the magnetic field. In particular, a universal stability theorem is obtained when the dusty gas flow is electrically conducting in the presence of an applied magnetic field, and the dust particles are non-uniformly distributed

  15. Excess wind power

    DEFF Research Database (Denmark)

    Østergaard, Poul Alberg

    2005-01-01

    Expansion of wind power is an important element in Danish climate change abatement policy. Starting from a high penetration of approx 20% however, momentary excess production will become an important issue in the future. Through energy systems analyses using the EnergyPLAN model and economic...... analyses it is analysed how excess productions are better utilised; through conversion into hydrogen of through expansion of export connections thereby enabling sales. The results demonstrate that particularly hydrogen production is unviable under current costs but transmission expansion could...

  16. Response of Renal Podocytes to Excessive Hydrostatic Pressure: a Pathophysiologic Cascade in a Malignant Hypertension Model

    Directory of Open Access Journals (Sweden)

    Ramzia Abu Hamad

    2017-12-01

    Full Text Available Background/Aims: Renal injuries induced by increased intra-glomerular pressure coincide with podocyte detachment from the glomerular basement membrane (GBM. In previous studies, it was demonstrated that mesangial cells have a crucial role in the pathogenesis of malignant hypertension. However, the exact pathophysiological cascade responsible for podocyte detachment and its relationship with mesangial cells has not been fully elucidated yet and this was the aim of the current study. Methods: Rat renal mesangial or podocytes were exposed to high hydrostatic pressure in an in-vitro model of malignant hypertension. The resulted effects on podocyte detachment, apoptosis and expression of podocin and integrinβ1 in addition to Angiotensin-II and TGF-β1 generation were evaluated. To simulate the paracrine effect podocytes were placed in mesangial cell media pre-exposed to pressure, or in media enriched with Angiotensin-II, TGF-β1 or receptor blockers. Results: High pressure resulted in increased Angiotensin-II levels in mesangial and podocyte cells. Angiotensin-II via the AT1 receptors reduced podocin expression and integrinβ1, culminating in detachment of both viable and apoptotic podocytes. Mesangial cells exposed to pressure had a greater increase in Angiotensin-II than pressure-exposed podocytes. The massively increased concentration of Angiotensin-II by mesangial cells, together with increased TGF-β1 production, resulted in increased apoptosis and detachment of non-viable apoptotic podocytes. Unlike the direct effect of pressure on podocytes, the mesangial mediated effects were not related to changes in adhesion proteins expression. Conclusions: Hypertension induces podocyte detachment by autocrine and paracrine effects. In a direct response to pressure, podocytes increase Angiotensin-II levels. This leads, via AT1 receptors, to structural changes in adhesion proteins, culminating in viable podocyte detachment. Paracrine effects of

  17. LHC di-photon excess and gauge coupling unification in extra Z{sup '} heterotic-string derived models

    Energy Technology Data Exchange (ETDEWEB)

    Ashfaque, J. [University of Liverpool, Department of Mathematical Sciences, Liverpool (United Kingdom); Delle Rose, L. [University of Southampton, School of Physics and Astronomy, Southampton (United Kingdom); Faraggi, A.E. [Rutherford Appleton Laboratory, Department of Particle Physics, Chilton, Didcot (United Kingdom); Marzo, C. [Universita del Salento, Dipartimento di Matematica e Fisica ' ' Ennio De Giorgi' ' , Lecce (Italy); INFN, Lecce (Italy)

    2016-10-15

    A di-photon excess at the LHC can be explained as a Standard Model singlet that is produced and decays by heavy vector-like colour triplets and electroweak doublets in one-loop diagrams. The characteristics of the required spectrum are well motivated in heterotic-string constructions that allow for a light Z{sup '}. Anomaly cancellation of the U(1){sub Z'} symmetry requires the existence of the Standard Model singlet and vector-like states in the vicinity of the U(1){sub Z'} breaking scale. In this paper we show that the agreement with the gauge coupling data at one-loop is identical to the case of the Minimal Supersymmetric Standard Model, owing to cancellations between the additional states. We further show that effects arising from heavy thresholds may push the supersymmetric spectrum beyond the reach of the LHC, while maintaining the agreement with the gauge coupling data. We show that the string-inspired model can indeed produce an observable signal and discuss the feasibility of obtaining viable scalar mass spectrum. (orig.)

  18. A statistical regression model for the estimation of acrylamide concentrations in French fries for excess lifetime cancer risk assessment.

    Science.gov (United States)

    Chen, Ming-Jen; Hsu, Hui-Tsung; Lin, Cheng-Li; Ju, Wei-Yuan

    2012-10-01

    Human exposure to acrylamide (AA) through consumption of French fries and other foods has been recognized as a potential health concern. Here, we used a statistical non-linear regression model, based on the two most influential factors, cooking temperature and time, to estimate AA concentrations in French fries. The R(2) of the predictive model is 0.83, suggesting the developed model was significant and valid. Based on French fry intake survey data conducted in this study and eight frying temperature-time schemes which can produce tasty and visually appealing French fries, the Monte Carlo simulation results showed that if AA concentration is higher than 168 ppb, the estimated cancer risk for adolescents aged 13-18 years in Taichung City would be already higher than the target excess lifetime cancer risk (ELCR), and that by taking into account this limited life span only. In order to reduce the cancer risk associated with AA intake, the AA levels in French fries might have to be reduced even further if the epidemiological observations are valid. Our mathematical model can serve as basis for further investigations on ELCR including different life stages and behavior and population groups. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Serviceability limit state related to excessive lateral deformations to account for infill walls in the structural model

    Directory of Open Access Journals (Sweden)

    G. M. S. ALVA

    Full Text Available Brazilian Codes NBR 6118 and NBR 15575 provide practical values for interstory drift limits applied to conventional modeling in order to prevent negative effects in masonry infill walls caused by excessive lateral deformability, however these codes do not account for infill walls in the structural model. The inclusion of infill walls in the proposed model allows for a quantitative evaluation of structural stresses in these walls and an assessment of cracking in these elements (sliding shear diagonal tension and diagonal compression cracking. This paper presents the results of simulations of single-story one-bay infilled R/C frames. The main objective is to show how to check the serviceability limit states under lateral loads when the infill walls are included in the modeling. The results of numerical simulations allowed for an evaluation of stresses and the probable cracking pattern in infill walls. The results also allowed an identification of some advantages and limitations of the NBR 6118 practical procedure based on interstory drift limits.

  20. Modeling the Phase Composition of Gas Condensate in Pipelines

    Science.gov (United States)

    Dudin, S. M.; Zemenkov, Yu D.; Shabarov, A. B.

    2016-10-01

    Gas condensate fields demonstrate a number of thermodynamic characteristics to be considered when they are developed, as well as when gas condensate is transported and processed. A complicated phase behavior of the gas condensate system, as well as the dependence of the extracted raw materials on the phase state of the deposit other conditions being equal, is a key aspect. Therefore, when designing gas condensate lines the crucial task is to select the most appropriate methods of calculating thermophysical properties and phase equilibrium of the transported gas condensate. The paper describes a physical-mathematical model of a gas-liquid flow in the gas condensate line. It was developed based on balance equations of conservation of mass, impulse and energy of the transported medium within the framework of a quasi-1D approach. Constitutive relationships are given separately, and practical recommendations on how to apply the research results are provided as well.

  1. Model documentation: Natural gas transmission and distribution model of the National Energy Modeling System. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-02-17

    The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of integrated Analysis and Forecasting of the Energy information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The methodology employed allows the analysis of impacts of regional capacity constraints in the interstate natural gas pipeline network and the identification of pipeline capacity expansion requirements. There is an explicit representation of core and noncore markets for natural gas transmission and distribution services, and the key components of pipeline tariffs are represented in a pricing algorithm. Natural gas pricing and flow patterns are derived by obtaining a market equilibrium across the three main elements of the natural gas market: the supply element, the demand element, and the transmission and distribution network that links them. The NGTDM consists of four modules: the Annual Flow Module, the Capacity F-expansion Module, the Pipeline Tariff Module, and the Distributor Tariff Module. A model abstract is provided in Appendix A.

  2. Model documentation: Natural gas transmission and distribution model of the National Energy Modeling System. Volume 1

    International Nuclear Information System (INIS)

    1995-01-01

    The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of integrated Analysis and Forecasting of the Energy information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The methodology employed allows the analysis of impacts of regional capacity constraints in the interstate natural gas pipeline network and the identification of pipeline capacity expansion requirements. There is an explicit representation of core and noncore markets for natural gas transmission and distribution services, and the key components of pipeline tariffs are represented in a pricing algorithm. Natural gas pricing and flow patterns are derived by obtaining a market equilibrium across the three main elements of the natural gas market: the supply element, the demand element, and the transmission and distribution network that links them. The NGTDM consists of four modules: the Annual Flow Module, the Capacity F-expansion Module, the Pipeline Tariff Module, and the Distributor Tariff Module. A model abstract is provided in Appendix A

  3. A Gas Scheduling Optimization Model for Steel Enterprises

    Directory of Open Access Journals (Sweden)

    Niu Honghai

    2017-01-01

    Full Text Available Regarding the scheduling problems of steel enterprises, this research designs the gas scheduling optimization model according to the rules and priorities. Considering different features and the process changes of the gas unit in the process of actual production, the calculation model of process state and gas consumption soft measurement together with the rules of scheduling optimization is proposed to provide the dispatchers with real-time gas using status of each process, then help them to timely schedule and reduce the gas volume fluctuations. In the meantime, operation forewarning and alarm functions are provided to avoid the abnormal situation in the scheduling, which has brought about very good application effect in the actual scheduling and ensures the safety of the gas pipe network system and the production stability.

  4. A global fit of the γ-ray galactic center excess within the scalar singlet Higgs portal model

    International Nuclear Information System (INIS)

    Cuoco, Alessandro; Eiteneuer, Benedikt; Heisig, Jan; Krämer, Michael

    2016-01-01

    We analyse the excess in the γ-ray emission from the center of our galaxy observed by Fermi-LAT in terms of dark matter annihilation within the scalar Higgs portal model. In particular, we include the astrophysical uncertainties from the dark matter distribution and allow for unspecified additional dark matter components. We demonstrate through a detailed numerical fit that the strength and shape of the γ-ray spectrum can indeed be described by the model in various regions of dark matter masses and couplings. Constraints from invisible Higgs decays, direct dark matter searches, indirect searches in dwarf galaxies and for γ-ray lines, and constraints from the dark matter relic density reduce the parameter space to dark matter masses near the Higgs resonance. We find two viable regions: one where the Higgs-dark matter coupling is of O(10"−"2), and an additional dark matter component beyond the scalar WIMP of our model is preferred, and one region where the Higgs-dark matter coupling may be significantly smaller, but where the scalar WIMP constitutes a significant fraction or even all of dark matter. Both viable regions are hard to probe in future direct detection and collider experiments.

  5. Negotiation model in gas industry; Modelos de negociacao na industria de gas

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    It is presented two negotiation models (Bilateral and Poolco) that are being used by natural gas industry at the present time. The main differences are characterized between these models. Basically, these differences can be found in the nature of the transactions and in the way as they are coordinated by the gas market and also by the transport market. The Bilateral model is based on decentralized bilateral transactions, by other hand in the Poolco model the transactions are coordinated by just one entity. So, in this model all transactions are centralized.

  6. Modelling of Rotor-gas bearings for Feedback Controller Design

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Niemann, Hans Henrik

    2014-01-01

    Controllable rotor-gas bearings are popular oering adaptability, high speed operation, low friction and clean operation. Rotor-gas bearings are however highly sensitive to disturbances due to the low friction of the injected gas. These undesirable damping properties call for controllers, which ca...... and are shown to accurately describe the dynamical behaviour of the rotor-gas bearing. Design of a controller using the identied models is treated and experiments verify the improvement of the damping properties of the rotor-gas bearing.......Controllable rotor-gas bearings are popular oering adaptability, high speed operation, low friction and clean operation. Rotor-gas bearings are however highly sensitive to disturbances due to the low friction of the injected gas. These undesirable damping properties call for controllers, which can...... be designed from suitable models describing the relation from actuator input to measured shaft position. Current state of the art models of controllable gas bearings however do not provide such relation, which calls for alternative strategies. The present contribution discusses the challenges for feedback...

  7. A concise review of Harwell modelling of fission gas behaviour

    International Nuclear Information System (INIS)

    Wood, M.H.; Hayns, M.R.

    1976-07-01

    A review is presented of recent theoretical studies, performed at AERE Harwell, of fission gas behaviour in nuclear fuels. This includes a brief description of the rather sophisticated model approach and a discussion of the application of these models to predicting fission gas release and swelling in both normal operational and transient regimes. These studies have resulted in the derivation of more computationally efficient models which are also described. (author)

  8. Graphite-MicroMégas, a tool for DNA modeling

    OpenAIRE

    Hornus , Samuel; Larivière , Damien

    2011-01-01

    National audience; MicroMégas is the current state of an ongoing effort to develop tools for modeling biological assembly of molecules. We here present its DNA modeling part. MicroMégas is implemented as a plug-in to Graphite, which is a research plat- form for computer graphics, 3D modeling and numerical geometry that is developed by members of the ALICE team of INRIA.; Nous décrivons l'outils MicroMégas et les techniques qu'il met en jeu pour la modélisation d'assemblage de molécule, en par...

  9. Dense-gas dispersion advection-diffusion model

    International Nuclear Information System (INIS)

    Ermak, D.L.

    1992-07-01

    A dense-gas version of the ADPIC particle-in-cell, advection- diffusion model was developed to simulate the atmospheric dispersion of denser-than-air releases. In developing the model, it was assumed that the dense-gas effects could be described in terms of the vertically-averaged thermodynamic properties and the local height of the cloud. The dense-gas effects were treated as a perturbation to the ambient thermodynamic properties (density and temperature), ground level heat flux, turbulence level (diffusivity), and windfield (gravity flow) within the local region of the dense-gas cloud. These perturbations were calculated from conservation of energy and conservation of momentum principles along with the ideal gas law equation of state for a mixture of gases. ADPIC, which is generally run in conjunction with a mass-conserving wind flow model to provide the advection field, contains all the dense-gas modifications within it. This feature provides the versatility of coupling the new dense-gas ADPIC with alternative wind flow models. The new dense-gas ADPIC has been used to simulate the atmospheric dispersion of ground-level, colder-than-ambient, denser-than-air releases and has compared favorably with the results of field-scale experiments

  10. Modeling of Thermal Behavior of Raw Natural Gas Air Coolers

    Science.gov (United States)

    Scherbinin, S. V.; Prakhova, M. Yu; Krasnov, A. N.; Khoroshavina, E. A.

    2018-05-01

    When gas is being prepared for a long-range transportation, it passes through air cooling units (ACUs) after compressing; there, hot gas passing through finned tubes is cooled with air streams. ACU's mode of operation shall ensure a certain value of gas temperature at the ACU's outlet. At that, when cooling raw gas, temperature distribution along all the tubes shall be known to prevent local hydrate formation. The paper proposes a mathematical model allowing one to obtain a thermal field distribution inside the ACU and study influence of various factors onto it.

  11. Modelling and simulation of gas explosions in complex geometries

    Energy Technology Data Exchange (ETDEWEB)

    Saeter, Olav

    1998-12-31

    This thesis presents a three-dimensional Computational Fluid Dynamics (CFD) code (EXSIM94) for modelling and simulation of gas explosions in complex geometries. It gives the theory and validates the following sub-models : (1) the flow resistance and turbulence generation model for densely packed regions, (2) the flow resistance and turbulence generation model for single objects, and (3) the quasi-laminar combustion model. It is found that a simple model for flow resistance and turbulence generation in densely packed beds is able to reproduce the medium and large scale MERGE explosion experiments of the Commission of European Communities (CEC) within a band of factor 2. The model for a single representation is found to predict explosion pressure in better agreement with the experiments with a modified k-{epsilon} model. This modification also gives a slightly improved grid independence for realistic gas explosion approaches. One laminar model is found unsuitable for gas explosion modelling because of strong grid dependence. Another laminar model is found to be relatively grid independent and to work well in harmony with the turbulent combustion model. The code is validated against 40 realistic gas explosion experiments. It is relatively grid independent in predicting explosion pressure in different offshore geometries. It can predict the influence of ignition point location, vent arrangements, different geometries, scaling effects and gas reactivity. The validation study concludes with statistical and uncertainty analyses of the code performance. 98 refs., 96 figs, 12 tabs.

  12. Hierarchy of simulation models for a turbofan gas engine

    Science.gov (United States)

    Longenbaker, W. E.; Leake, R. J.

    1977-01-01

    Steady-state and transient performance of an F-100-like turbofan gas engine are modeled by a computer program, DYNGEN, developed by NASA. The model employs block data maps and includes about 25 states. Low-order nonlinear analytical and linear techniques are described in terms of their application to the model. Experimental comparisons illustrating the accuracy of each model are presented.

  13. Spectral element modelling of seismic wave propagation in visco-elastoplastic media including excess-pore pressure development

    Science.gov (United States)

    Oral, Elif; Gélis, Céline; Bonilla, Luis Fabián; Delavaud, Elise

    2017-12-01

    Numerical modelling of seismic wave propagation, considering soil nonlinearity, has become a major topic in seismic hazard studies when strong shaking is involved under particular soil conditions. Indeed, when strong ground motion propagates in saturated soils, pore pressure is another important parameter to take into account when successive phases of contractive and dilatant soil behaviour are expected. Here, we model 1-D seismic wave propagation in linear and nonlinear media using the spectral element numerical method. The study uses a three-component (3C) nonlinear rheology and includes pore-pressure excess. The 1-D-3C model is used to study the 1987 Superstition Hills earthquake (ML 6.6), which was recorded at the Wildlife Refuge Liquefaction Array, USA. The data of this event present strong soil nonlinearity involving pore-pressure effects. The ground motion is numerically modelled for different assumptions on soil rheology and input motion (1C versus 3C), using the recorded borehole signals as input motion. The computed acceleration-time histories show low-frequency amplification and strong high-frequency damping due to the development of pore pressure in one of the soil layers. Furthermore, the soil is found to be more nonlinear and more dilatant under triaxial loading compared to the classical 1C analysis, and significant differences in surface displacements are observed between the 1C and 3C approaches. This study contributes to identify and understand the dominant phenomena occurring in superficial layers, depending on local soil properties and input motions, conditions relevant for site-specific studies.

  14. Wet gas flow modeling for a vertically mounted Venturi meter

    International Nuclear Information System (INIS)

    Xu, Lijun; Zhou, Wanlu; Li, Xiaomin

    2012-01-01

    Venturi meters are playing an increasingly important role in wet gas metering in natural gas and oil industries. Due to the effect of liquid in a wet gas, the differential pressure over the converging section of a Venturi meter is higher than that when a pure gas flows through with the same flow rate. This phenomenon is referred to as over-reading. Thus, a correction for the over-reading is required. Most of the existing wet gas models are more suitable for higher pressure (>2 MPa) than lower pressure ( 0.5) than lower quality (<0.5) in recent years. However, conditions of lower pressure and lower quality also widely exist in the gas and oil industries. By comparing the performances of eight existing wet gas models in low-pressure range of 0.26–0.86 MPa and low-quality range of 0.07–0.36 with a vertically mounted Venturi meter of diameter ratio 0.45, de Leeuw's model was proven to perform best. Derived from de Leeuw's model, a modified model with better performance for the low-pressure and low-quality ranges was obtained. Experimental data showed that the root mean square of the relative errors of the over-reading was 2.30%. (paper)

  15. Modelling and Identification for Control of Gas Bearings

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Niemann, Hans Henrik; Santos, Ilmar

    2015-01-01

    Gas bearings are popular for their high speed capabilities, low friction and clean operation, but suffer from poor damping, which poses challenges for safe operation in presence of disturbances. Enhanced damping can be achieved through active lubrication techniques using feedback control laws....... Such control design requires models with low complexity, able to describe the dominant dynamics from actuator input to sensor output over the relevant range of operation. The mathematical models based on first principles are not easy to obtain, and in many cases, they cannot be directly used for control design...... to industrial rotating machinery with gas bearings and to allow for subsequent control design. The paper shows how piezoelectric actuators in a gas bearing are efficiently used to perturb the gas film for identification over relevant ranges of rotational speed and gas injection pressure. Parameter...

  16. RAETRAD MODEL OF RADON GAS GENERATION, TRANSPORT, AND INDOOR ENTRY

    Science.gov (United States)

    The report describes the theoretical basis, implementation, and validation of the Radon Emanation and Transport into Dwellings (RAETRAD) model, a conceptual and mathematical approach for simulating radon (222Rn) gas generation and transport from soils and building foundations to ...

  17. Overview of the EPRI CONTRACTMIX model for natural gas applications

    International Nuclear Information System (INIS)

    1993-09-01

    The Contract Mix Model (CONTRACTMIX) is designed to assist gas supply planners in analyzing the costs and risks of alternative supply strategies. By explicitly incorporating uncertainty about gas demand and market conditions into the analysis, the methodology permits the analyst to compare contracting strategies on the basis of cost and risk and to assess the value of flexible strategies and contracts. The model is applicable to purchase decisions for natural gas and other fuels. CONTRACTMIX may be used at all phases of supply decision-making, from broad strategy formulation to detailed contract design and evaluation. This document introduces the prospective user to the model's capability for analysis of gas supply contracting decisions. The document describes the types of problems CONTRACTMIX is designed to address as well as the model's structure, inputs, outputs, and unique features

  18. Thermodynamic Modeling of Natural Gas Systems Containing Water

    DEFF Research Database (Denmark)

    Karakatsani, Eirini K.; Kontogeorgis, Georgios M.

    2013-01-01

    As the need for dew point specifications remains very urgent in the natural gas industry, the development of accurate thermodynamic models, which will match experimental data and will allow reliable extrapolations, is needed. Accurate predictions of the gas phase water content in equilibrium...... with a heavy phase were previously obtained using cubic plus association (CPA) coupled with a solid phase model in the case of hydrates, for the binary systems of water–methane and water–nitrogen and a few natural gas mixtures. In this work, CPA is being validated against new experimental data, both water...... content and phase equilibrium data, and solid model parameters are being estimated for four natural gas main components (methane, ethane, propane, and carbon dioxide). Different tests for the solid model parameters are reported, including vapor-hydrate-equilibria (VHE) and liquid-hydrate-equilibria (LHE...

  19. Numerical modeling of underground storage system for natural gas

    Science.gov (United States)

    Ding, J.; Wang, S.

    2017-12-01

    Natural gas is an important type of base-load energy, and its supply needs to be adjusted according to different demands in different seasons. For example, since natural gas is increasingly used to replace coal for winter heating, the demand for natural gas in winter is much higher than that in other seasons. As storage systems are the essential tools for balancing seasonal supply and demand, the design and simulation of natural gas storage systems form an important research direction. In this study, a large-scale underground storage system for natural gas is simulated based on theoretical analysis and finite element modeling.It is proven that the problem of axi-symmetric Darcy porous flow of ideal gas is governed by the Boussinesq equation. In terms of the exact solution to the Boussinesq equation, the basic operating characteristics of the underground storage system is analyzed, and it is demonstrated that the propagation distance of the pore pressure is proportional to the 1/4 power of the mass flow rate and to the 1/2 power of the propagation time. This quantitative relationship can be used to guide the overall design of natural gas underground storage systems.In order to fully capture the two-way coupling between pore pressure and elastic matrix deformation, a poro-elastic finite element model for natural gas storage is developed. Based on the numerical model, the dynamic processes of gas injection, storage and extraction are simulated, and the corresponding time-dependent surface deformations are obtained. The modeling results not only provide a theoretical basis for real-time monitoring for the operating status of the underground storage system through surface deformation measurements, but also demonstrate that a year-round balance can be achieved through periodic gas injection and extraction.This work is supported by the CAS "100 talents" Program and the National Natural Science Foundation of China (41371090).

  20. Phase space analysis of some interacting Chaplygin gas models

    Energy Technology Data Exchange (ETDEWEB)

    Khurshudyan, M. [Academy of Sciences of Armenia, Institute for Physical Research, Ashtarak (Armenia); Tomsk State University of Control Systems and Radioelectronics, Laboratory for Theoretical Cosmology, Tomsk (Russian Federation); Tomsk State Pedagogical University, Department of Theoretical Physics, Tomsk (Russian Federation); Myrzakulov, R. [Eurasian National University, Eurasian International Center for Theoretical Physics, Astana (Kazakhstan)

    2017-02-15

    In this paper we discuss a phase space analysis of various interacting Chaplygin gas models in general relativity. Linear and nonlinear sign changeable interactions are considered. For each case appropriate late time attractors of field equations are found. The Chaplygin gas is one of the dark fluids actively considered in modern cosmology due to the fact that it is a joint model of dark energy and dark matter. (orig.)

  1. Decline Curve Based Models for Predicting Natural Gas Well Performance

    OpenAIRE

    Kamari, Arash; Mohammadi, Amir H.; Lee, Moonyong; Mahmood, Tariq; Bahadori, Alireza

    2016-01-01

    The productivity of a gas well declines over its production life as cannot cover economic policies. To overcome such problems, the production performance of gas wells should be predicted by applying reliable methods to analyse the decline trend. Therefore, reliable models are developed in this study on the basis of powerful artificial intelligence techniques viz. the artificial neural network (ANN) modelling strategy, least square support vector machine (LSSVM) approach, adaptive neuro-fuzzy ...

  2. Excess water dynamics in hydrotalcite: QENS study

    Indian Academy of Sciences (India)

    dynamics of excess water in hydrotalcite sample with varied content of excess water are reported. Translational motion of excess water can be best described by random transla- tional jump diffusion model. The observed increase in translational diffusivity with increase in the amount of excess water is attributed to the ...

  3. Modeling Data with Excess Zeros and Measurement Error: Application to Evaluating Relationships between Episodically Consumed Foods and Health Outcomes

    KAUST Repository

    Kipnis, Victor

    2009-03-03

    Dietary assessment of episodically consumed foods gives rise to nonnegative data that have excess zeros and measurement error. Tooze et al. (2006, Journal of the American Dietetic Association 106, 1575-1587) describe a general statistical approach (National Cancer Institute method) for modeling such food intakes reported on two or more 24-hour recalls (24HRs) and demonstrate its use to estimate the distribution of the food\\'s usual intake in the general population. In this article, we propose an extension of this method to predict individual usual intake of such foods and to evaluate the relationships of usual intakes with health outcomes. Following the regression calibration approach for measurement error correction, individual usual intake is generally predicted as the conditional mean intake given 24HR-reported intake and other covariates in the health model. One feature of the proposed method is that additional covariates potentially related to usual intake may be used to increase the precision of estimates of usual intake and of diet-health outcome associations. Applying the method to data from the Eating at America\\'s Table Study, we quantify the increased precision obtained from including reported frequency of intake on a food frequency questionnaire (FFQ) as a covariate in the calibration model. We then demonstrate the method in evaluating the linear relationship between log blood mercury levels and fish intake in women by using data from the National Health and Nutrition Examination Survey, and show increased precision when including the FFQ information. Finally, we present simulation results evaluating the performance of the proposed method in this context.

  4. Modeling and forecasting natural gas demand in Bangladesh

    International Nuclear Information System (INIS)

    Wadud, Zia; Dey, Himadri S.; Kabir, Md. Ashfanoor; Khan, Shahidul I.

    2011-01-01

    Natural gas is the major indigenous source of energy in Bangladesh and accounts for almost one-half of all primary energy used in the country. Per capita and total energy use in Bangladesh is still very small, and it is important to understand how energy, and natural gas demand will evolve in the future. We develop a dynamic econometric model to understand the natural gas demand in Bangladesh, both in the national level, and also for a few sub-sectors. Our demand model shows large long run income elasticity - around 1.5 - for aggregate demand for natural gas. Forecasts into the future also show a larger demand in the future than predicted by various national and multilateral organizations. Even then, it is possible that our forecasts could still be at the lower end of the future energy demand. Price response was statistically not different from zero, indicating that prices are possibly too low and that there is a large suppressed demand for natural gas in the country. - Highlights: → Natural gas demand is modeled using dynamic econometric methods, first of its kind in Bangladesh. → Income elasticity for aggregate natural gas demand in Bangladesh is large-around 1.5. → Demand is price insensitive, indicating too low prices and/or presence of large suppressed demand. → Demand forecasts reveal large divergence from previous estimates, which is important for planning. → Attempts to model demand for end-use sectors were successful only for the industrial sector.

  5. Decline curve based models for predicting natural gas well performance

    Directory of Open Access Journals (Sweden)

    Arash Kamari

    2017-06-01

    Full Text Available The productivity of a gas well declines over its production life as cannot cover economic policies. To overcome such problems, the production performance of gas wells should be predicted by applying reliable methods to analyse the decline trend. Therefore, reliable models are developed in this study on the basis of powerful artificial intelligence techniques viz. the artificial neural network (ANN modelling strategy, least square support vector machine (LSSVM approach, adaptive neuro-fuzzy inference system (ANFIS, and decision tree (DT method for the prediction of cumulative gas production as well as initial decline rate multiplied by time as a function of the Arps' decline curve exponent and ratio of initial gas flow rate over total gas flow rate. It was concluded that the results obtained based on the models developed in current study are in satisfactory agreement with the actual gas well production data. Furthermore, the results of comparative study performed demonstrates that the LSSVM strategy is superior to the other models investigated for the prediction of both cumulative gas production, and initial decline rate multiplied by time.

  6. Modeling and forecasting natural gas demand in Bangladesh

    Energy Technology Data Exchange (ETDEWEB)

    Wadud, Zia, E-mail: ziawadud@yahoo.com [Bangladesh University of Engineering and Technology (Bangladesh); Dey, Himadri S. [University of Notre Dame (United States); Kabir, Md. Ashfanoor; Khan, Shahidul I. [Bangladesh University of Engineering and Technology (Bangladesh)

    2011-11-15

    Natural gas is the major indigenous source of energy in Bangladesh and accounts for almost one-half of all primary energy used in the country. Per capita and total energy use in Bangladesh is still very small, and it is important to understand how energy, and natural gas demand will evolve in the future. We develop a dynamic econometric model to understand the natural gas demand in Bangladesh, both in the national level, and also for a few sub-sectors. Our demand model shows large long run income elasticity - around 1.5 - for aggregate demand for natural gas. Forecasts into the future also show a larger demand in the future than predicted by various national and multilateral organizations. Even then, it is possible that our forecasts could still be at the lower end of the future energy demand. Price response was statistically not different from zero, indicating that prices are possibly too low and that there is a large suppressed demand for natural gas in the country. - Highlights: > Natural gas demand is modeled using dynamic econometric methods, first of its kind in Bangladesh. > Income elasticity for aggregate natural gas demand in Bangladesh is large-around 1.5. > Demand is price insensitive, indicating too low prices and/or presence of large suppressed demand. > Demand forecasts reveal large divergence from previous estimates, which is important for planning. > Attempts to model demand for end-use sectors were successful only for the industrial sector.

  7. Evaluating fugacity models for trace components in landfill gas

    Energy Technology Data Exchange (ETDEWEB)

    Shafi, Sophie [Integrated Waste Management Centre, Sustainable Systems Department, Building 61, School of Industrial and Manufacturing Science, Cranfield University, Cranfield, Bedfordshire MK43 0AL (United Kingdom); Sweetman, Andrew [Department of Environmental Science, Lancaster University, Lancaster LA1 4YQ (United Kingdom); Hough, Rupert L. [Integrated Waste Management Centre, Sustainable Systems Department, Building 61, School of Industrial and Manufacturing Science, Cranfield University, Cranfield, Bedfordshire MK43 0AL (United Kingdom); Smith, Richard [Integrated Waste Management Centre, Sustainable Systems Department, Building 61, School of Industrial and Manufacturing Science, Cranfield University, Cranfield, Bedfordshire MK43 0AL (United Kingdom); Rosevear, Alan [Science Group - Waste and Remediation, Environment Agency, Reading RG1 8DQ (United Kingdom); Pollard, Simon J.T. [Integrated Waste Management Centre, Sustainable Systems Department, Building 61, School of Industrial and Manufacturing Science, Cranfield University, Cranfield, Bedfordshire MK43 0AL (United Kingdom)]. E-mail: s.pollard@cranfield.ac.uk

    2006-12-15

    A fugacity approach was evaluated to reconcile loadings of vinyl chloride (chloroethene), benzene, 1,3-butadiene and trichloroethylene in waste with concentrations observed in landfill gas monitoring studies. An evaluative environment derived from fictitious but realistic properties such as volume, composition, and temperature, constructed with data from the Brogborough landfill (UK) test cells was used to test a fugacity approach to generating the source term for use in landfill gas risk assessment models (e.g. GasSim). SOILVE, a dynamic Level II model adapted here for landfills, showed greatest utility for benzene and 1,3-butadiene, modelled under anaerobic conditions over a 10 year simulation. Modelled concentrations of these components (95 300 {mu}g m{sup -3}; 43 {mu}g m{sup -3}) fell within measured ranges observed in gas from landfills (24 300-180 000 {mu}g m{sup -3}; 20-70 {mu}g m{sup -3}). This study highlights the need (i) for representative and time-referenced biotransformation data; (ii) to evaluate the partitioning characteristics of organic matter within waste systems and (iii) for a better understanding of the role that gas extraction rate (flux) plays in producing trace component concentrations in landfill gas. - Fugacity for trace component in landfill gas.

  8. Reliability modelling - PETROBRAS 2010 integrated gas supply chain

    Energy Technology Data Exchange (ETDEWEB)

    Faertes, Denise; Heil, Luciana; Saker, Leonardo; Vieira, Flavia; Risi, Francisco; Domingues, Joaquim; Alvarenga, Tobias; Carvalho, Eduardo; Mussel, Patricia

    2010-09-15

    The purpose of this paper is to present the innovative reliability modeling of Petrobras 2010 integrated gas supply chain. The model represents a challenge in terms of complexity and software robustness. It was jointly developed by PETROBRAS Gas and Power Department and Det Norske Veritas. It was carried out with the objective of evaluating security of supply of 2010 gas network design that was conceived to connect Brazilian Northeast and Southeast regions. To provide best in class analysis, state of the art software was used to quantify the availability and the efficiency of the overall network and its individual components.

  9. Gas Atomization of Aluminium Melts: Comparison of Analytical Models

    Directory of Open Access Journals (Sweden)

    Georgios Antipas

    2012-06-01

    Full Text Available A number of analytical models predicting the size distribution of particles during atomization of Al-based alloys by N2, He and Ar gases were compared. Simulations of liquid break up in a close coupled atomizer revealed that the finer particles are located near the center of the spray cone. Increasing gas injection pressures led to an overall reduction of particle diameters and caused a migration of the larger powder particles towards the outer boundary of the flow. At sufficiently high gas pressures the spray became monodisperse. The models also indicated that there is a minimum achievable mean diameter for any melt/gas system.

  10. Natural gas leak mapper

    Science.gov (United States)

    Reichardt, Thomas A [Livermore, CA; Luong, Amy Khai [Dublin, CA; Kulp, Thomas J [Livermore, CA; Devdas, Sanjay [Albany, CA

    2008-05-20

    A system is described that is suitable for use in determining the location of leaks of gases having a background concentration. The system is a point-wise backscatter absorption gas measurement system that measures absorption and distance to each point of an image. The absorption measurement provides an indication of the total amount of a gas of interest, and the distance provides an estimate of the background concentration of gas. The distance is measured from the time-of-flight of laser pulse that is generated along with the absorption measurement light. The measurements are formated into an image of the presence of gas in excess of the background. Alternatively, an image of the scene is superimosed on the image of the gas to aid in locating leaks. By further modeling excess gas as a plume having a known concentration profile, the present system provides an estimate of the maximum concentration of the gas of interest.

  11. Validation of spectral gas radiation models under oxyfuel conditions

    Energy Technology Data Exchange (ETDEWEB)

    Becher, Johann Valentin

    2013-05-15

    Combustion of hydrocarbon fuels with pure oxygen results in a different flue gas composition than combustion with air. Standard computational-fluid-dynamics (CFD) spectral gas radiation models for air combustion are therefore out of their validity range in oxyfuel combustion. This thesis provides a common spectral basis for the validation of new spectral models. A literature review about fundamental gas radiation theory, spectral modeling and experimental methods provides the reader with a basic understanding of the topic. In the first results section, this thesis validates detailed spectral models with high resolution spectral measurements in a gas cell with the aim of recommending one model as the best benchmark model. In the second results section, spectral measurements from a turbulent natural gas flame - as an example for a technical combustion process - are compared to simulated spectra based on measured gas atmospheres. The third results section compares simplified spectral models to the benchmark model recommended in the first results section and gives a ranking of the proposed models based on their accuracy. A concluding section gives recommendations for the selection and further development of simplified spectral radiation models. Gas cell transmissivity spectra in the spectral range of 2.4 - 5.4 {mu}m of water vapor and carbon dioxide in the temperature range from 727 C to 1500 C and at different concentrations were compared in the first results section at a nominal resolution of 32 cm{sup -1} to line-by-line models from different databases, two statistical-narrow-band models and the exponential-wide-band model. The two statistical-narrow-band models EM2C and RADCAL showed good agreement with a maximal band transmissivity deviation of 3 %. The exponential-wide-band model showed a deviation of 6 %. The new line-by-line database HITEMP2010 had the lowest band transmissivity deviation of 2.2% and was therefore recommended as a reference model for the

  12. Modeling Data with Excess Zeros and Measurement Error: Application to Evaluating Relationships between Episodically Consumed Foods and Health Outcomes

    KAUST Repository

    Kipnis, Victor; Midthune, Douglas; Buckman, Dennis W.; Dodd, Kevin W.; Guenther, Patricia M.; Krebs-Smith, Susan M.; Subar, Amy F.; Tooze, Janet A.; Carroll, Raymond J.; Freedman, Laurence S.

    2009-01-01

    Dietary assessment of episodically consumed foods gives rise to nonnegative data that have excess zeros and measurement error. Tooze et al. (2006, Journal of the American Dietetic Association 106, 1575-1587) describe a general statistical approach

  13. Static and dynamic modelling of gas turbines in advanced cycles

    Energy Technology Data Exchange (ETDEWEB)

    Gustafsson, Jan-Olof

    1998-12-01

    Gas turbines have been in operation for at least 50 years. The engine is used for propulsion of aircraft and high speed ships. It is used for power production in remote locations and for peak load and emergency situations. Gas turbines have been used in combined cycles for 20 to 30 years. Highly efficient power plants based on gas turbines are a competitive option for the power industry today. The thermal efficiency of the simple cycle gas turbine has increased due to higher turbine inlet temperatures and improved compressor and expander designs. Equally important are the improved cycles in which the gas turbine operates. One example is the combined cycle that uses steam for turbine cooling. Steam is extracted from the bottoming cycle, then used as airfoil coolant in a closed loop and returned to the bottoming cycle. The Evaporative Gas Turbine (EvGT), also known as the Humid Air Turbine (HAT), is another advanced cycle. A mixture of air and water vapour is used as working media. Air from the compressor outlet is humidified and then preheated in a recuperator prior to combustion. The static and dynamic performance is changed when the gas turbine is introduced in an evaporative cycle. The cycle is gaining in popularity, but so far it has not been demonstrated. A Swedish joint program to develop the cycle has been in operation since 1993. As part of the program, a small pilot plant is being erected at the Lund Institute of Technology (LTH). The plant is based on a 600 kW gas turbine, and demonstration of the EvGT cycle started autumn 1998 and will continue, in the present phase, for one year. This thesis presents static and dynamic models for traditional gas turbine components, such as, the compressor, combustor, expander and recuperator. A static model for the humidifier is presented, based on common knowledge for atmospheric humidification. All models were developed for the pilot plant at LTH with the objective to support evaluation of the process and individual

  14. Experimental Grey Box Model Identification of an Active Gas Bearing

    DEFF Research Database (Denmark)

    Theisen, Lukas Roy Svane; Pierart Vásquez, Fabián Gonzalo; Niemann, Hans Henrik

    2014-01-01

    in a dynamic model of an active gas bearing and subsequent control loop design. A grey box model is determined based on experiments where piezo actuated valves are used to perturb the journal and hence excite the rotor-bearing system. Such modelling from actuator to output is shown to effciently support...

  15. Models of Tidally Induced Gas Filaments in the Magellanic Stream

    Science.gov (United States)

    Pardy, Stephen A.; D’Onghia, Elena; Fox, Andrew J.

    2018-04-01

    The Magellanic Stream and Leading Arm of H I that stretches from the Large and Small Magellanic Clouds (LMC and SMC) and over 200° of the Southern sky is thought to be formed from multiple encounters between the LMC and SMC. In this scenario, most of the gas in the Stream and Leading Arm is stripped from the SMC, yet recent observations have shown a bifurcation of the Trailing Arm that reveals LMC origins for some of the gas. Absorption measurements in the Stream also reveal an order of magnitude more gas than in current tidal models. We present hydrodynamical simulations of the multiple encounters between the LMC and SMC at their first pass around the Milky Way, assuming that the Clouds were more extended and gas-rich in the past. Our models create filamentary structures of gas in the Trailing Stream from both the LMC and SMC. While the SMC trailing filament matches the observed Stream location, the LMC filament is offset. In addition, the total observed mass of the Stream in these models is underestimated by a factor of four when the ionized component is accounted for. Our results suggest that there should also be gas stripped from both the LMC and SMC in the Leading Arm, mirroring the bifurcation in the Trailing Stream. This prediction is consistent with recent measurements of spatial variation in chemical abundances in the Leading Arm, which show that gas from multiple sources is present, although its nature is still uncertain.

  16. NATGAS. A Model of the European Natural Gas Market

    International Nuclear Information System (INIS)

    Mulder, M; Zwart, G.

    2006-02-01

    The NATural GAS model is an integrated model of the European wholesale gas market providing long-run projections of supply, transport, storage and consumption patterns in the model region, aggregated in 5-year periods, distinguishing two seasons (winter and summer). Model results include levels of investment in the various branches, output and consumption, depletion of reserves and price levels. The NATGAS model computes long-term effects of policy measures on future gas production and gas prices in Europe. NATGAS is an equilibrium model describing behaviour of gas producers, investors in infrastructure (pipeline, LNG capacity, as well as storage), traders and consumers. NATGAS covers the main European demand regions, including the United Kingdom, Germany, the Netherlands and Italy. Moreover, it covers the main origins of supply on the European market, such as Russia, Norway, Algeria, the Netherlands, the United Kingdom and LNG. In this memorandum, we first discuss the theoretical background as well as the model specifications. Afterwards, we describe the data we used, present some results and assess validity by computing sensitivities and comparing with current developments

  17. Constitutive modeling of a nickel base superalloy -with a focus on gas turbine applications

    Energy Technology Data Exchange (ETDEWEB)

    Almroth, Per

    2003-05-01

    Gas turbines are used where large amounts of energy is needed, typically as engines in aircraft, ferries and power plants. From an efficiency point of view it is desirable to increase the service temperature as much as possible. One of the limiting factors is then the maximum allowable metal temperatures in the turbine stages, primarily in the blades of the first stage, that are exposed to the highest gas temperatures. Specially designed materials are used to cope with these severe conditions, such as the nickel base superalloy IN792. In order to be able to design the components for higher temperatures and tighter tolerances, a detailed understanding and computationel models of the material behaviour is needed. The models presented in this work have been developed with the objective of being physically well motivated, and with the intention of avoiding excessive numbers of parameters. The influence of the parameters should also be as easy as possible to interpret. The models are to describe the behaviour of IN792, under conditions typically found for a gas turbine blade. Specifically the high- and intermediate temperature isothermal modelling of IN792 have been addressed. One main issue when characterising the material and calibrating the models is the use of relevant tests, that are representative of component conditions. Therefore isothermal tests with an eye on the typical environment of a turbine blade have been planned and performed. Using numerical optimization techniques the material parameters for the isothermal behaviour of IN792 at 650 deg and 850 deg have been estimated. The good overall calibration results for these specific temperatures, using the presented modeling concept and nonstandard constitutive tests, suggests that the model can describe the behaviour of IN792 in gas turbine hot part applications.

  18. A lattice gas model on a tangled chain

    International Nuclear Information System (INIS)

    Mejdani, R.

    1993-04-01

    We have used a model of a lattice gas defined on a tangled chain to study the enzyme kinetics by a modified transfer matrix method. By using a simple iterative algorithm we have obtained different kinds of saturation curves for different configurations of the tangled chain and different types of the additional interactions. In some special cases of configurations and interactions we have found the same equations for the saturation curves, which we have obtained before studying the lattice gas model with nearest neighbor interactions or the lattice gas model with alternate nearest neighbor interactions, using different techniques as the correlated walks' theory, the partition point technique or the transfer matrix model. This more general model and the new results could be useful for the experimental investigations. (author). 20 refs, 6 figs

  19. Energetics and dynamics of excess electrons in simple fluids

    International Nuclear Information System (INIS)

    Space, B.

    1992-01-01

    Excess electronic dynamical and equilibrium properties are modeled in both polarizable and nonpolarizable noble gas fluids. Explicit dynamical calculations are carried out for excess electrons in fluid helium, where excess electronic eigenstates are localized. Energetics and dynamics are considered for fluids which span the entire range of polarizability present in the rare gases. Excess electronic eigenstates and eigenvalues are calculated for fluids of helium, argon and xenon. Both equilibrium and dynamical information is obtained from the calculation of these wavefunctions. A surface hopping trajectory method for studying nonadiabatic excess electronic relaxation in condensed systems is used to explore the nonadiabatic relaxation after photoexciting an equilibrated excess electron in dense fluid helium. The different types on nonadiabatic phenomena which are important in excess electronic relaxation are surveyed. The same surface hopping trajectory method is also used to study the rapid nonadiabatic relaxation after an excess electron is injected into unperturbed fluid helium. Several distinctively different relaxation processes, characterized by their relative importance at different times during the relaxation to a localized equilibrium state, are detailed. Though the dynamical properties of excess electrons under the conditions considered here have never been studied before, the behavior is remarkably similar to that observed in both experimental and theoretical studies of electron hydration dynamics, indicating that the processes described may be very general relaxation mechanisms for localization and trapping in fluids. Additionally, ground state energies of an excess electron, e 0 , are computed as a function of solvent density using model electron-atom pseudopotentials in fluid helium, argon, and xenon. The nonuniqueness of the pseudopotential description of electron-molecule interactions is demonstrated

  20. Excess Entropy and Diffusivity

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. Excess Entropy and Diffusivity. Excess entropy scaling of diffusivity (Rosenfeld,1977). Analogous relationships also exist for viscosity and thermal conductivity.

  1. HEAVY-DUTY GREENHOUSE GAS EMISSIONS MODEL ...

    Science.gov (United States)

    Class 2b-8 vocational truck manufacturers and Class 7/8 tractor manufacturers would be subject to vehicle-based fuel economy and emission standards that would use a truck simulation model to evaluate the impact of the truck tires and/or tractor cab design on vehicle compliance with any new standards. The EPA has created a model called “GHG Emissions Model (GEM)”, which is specifically tailored to predict truck GHG emissions. As the model is designed for the express purpose of vehicle compliance demonstration, it is less configurable than similar commercial products and its only outputs are GHG emissions and fuel consumption. This approach gives a simple and compact tool for vehicle compliance without the overhead and costs of a more sophisticated model. Evaluation of both fuel consumption and CO2 emissions from heavy-duty highway vehicles through a whole-vehicle operation simulation model.

  2. Shallow layer modelling of dense gas clouds

    Energy Technology Data Exchange (ETDEWEB)

    Ott, S.; Nielsen, M.

    1996-11-01

    The motivation for making shallow layer models is that they can deal with the dynamics of gravity driven flow in complex terrain at a modest computational cost compared to 3d codes. The main disadvantage is that the air-cloud interactions still have to be added `by hand`, where 3d models inherit the correct dynamics from the fundamental equations. The properties of the inviscid shallow water equations are discussed, focusing on existence and uniqueness of solutions. It is demonstrated that breaking waves and fronts pose severe problems, that can only be overcome if the hydrostatic approximation is given up and internal friction is added to the model. A set of layer integrated equations is derived starting from the Navier-Stokes equations. The various steps in the derivation are accompanied by plausibility arguments. These form the scientific basis of the model. The principle of least action is introduced as a means of generating consistent models, and as a tool for making discrete equations for numerical models, which automatically obey conservation laws. A numerical model called SLAM (Shallow LAyer Model) is presented. SLAM has some distinct features compared to other shallow layer models: A Lagrangian, moving grid; Explicit account for the turbulent kinetic energy budget; The entrainment rate is estimated on the basis of the local turbulent kinetic energy; Non-hydrostatic pressure; and Numerical methods respect conservation laws even for coarse grids. Thorney Island trial 8 is used as a reference case model tuning. The model reproduces the doughnut shape of the cloud and yield concentrations in reasonable agreement with observations, even when a small number of cells (e.g. 16) is used. It is concluded that lateral exchange of matter within the cloud caused by shear is important, and that the model should be improved on this point. (au) 16 ills., 38 refs.

  3. The World gas model. A multi-period mixed complementarity model for the global natural gas market

    International Nuclear Information System (INIS)

    Egging, Ruud; Holz, Franziska; Gabriel, Steven A.

    2010-01-01

    We provide the description, mathematical formulation and illustrative results of the World Gas Model, a multi-period complementarity model for the global natural gas market with explicit consideration of market power in the upstream market. Market players include producers, traders, pipeline and storage operators, LNG (liquefied natural gas) liquefiers and regasifiers as well as marketers. The model data set contains more than 80 countries and regions and covers 98% of world wide natural gas production and consumption. We also include a detailed representation of cross-border natural gas pipelines and constraints imposed by long-term contracts in the LNG market. The model is calibrated to match production and consumption projections from the PRIMES [EC. European energy and transport: trends to 2030-update 2007. Brussels: European Commission; 2008] and POLES models [EC. World energy technology outlook - 2050 (WETO-H2). Brussels: European Commission; 2006] up to 2030. The results of our numerical simulations illustrate how the supply shares of pipeline and LNG in various regions in the world develop very differently over time. LNG will continue to play a major role in the Asian market, also for new importers like China and India. Europe will expand its pipeline import capacities benefiting from its relative proximity to major gas suppliers. (author)

  4. Gas dynamics models for an oscillating gaseous core fission reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kuijper, J.C.; Dam, H. van; Hoogenboom, J.E. (Interuniversitair Reactor Inst., Delft (Netherlands))

    1991-01-01

    Two one-dimensional models are developed for the investigation of the gas dynamical behaviour of the fuel gas in a cylindrical gaseous core fission reactor. By numerical and analytical calculations, it is shown that, for the case where a direct energy extraction mechanism (such as magneto-hydrodynamics (MHD)) is not present, increasing density oscillations occur in the gas. Also an estimate is made of the attainable direct energy conversion efficiency, for the case where a direct energy extraction mechanism is present. (author).

  5. 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.

  6. Statistical models of a gas diffusion electrode: II. Current resistent

    Energy Technology Data Exchange (ETDEWEB)

    Proksch, D B; Winsel, O W

    1965-07-01

    The authors describe an apparatus for measuring the flow resistance of gas diffusion electrodes which is a mechanical analog of the Wheatstone bridge for measuring electric resistance. The flow resistance of a circular DSK electrode sheet, consisting of two covering layers and a working layer between them, was measured as a function of the gas pressure. While the pressure first was increased and then decreased, a hysteresis occurred, which is discussed and explained by a statistical model of a porous electrode.

  7. Statistical model of a gas diffusion electrode. III. Photomicrograph study

    Energy Technology Data Exchange (ETDEWEB)

    Winsel, A W

    1965-12-01

    A linear section through a gas diffusion electrode produces a certain distribution function of sinews with the pores. From this distribution function some qualities of the pore structure are derived, and an automatic device to determine the distribution function is described. With a statistical model of a gas diffusion electrode the behavior of a DSK electrode is discussed and compared with earlier measurements of the flow resistance of this material.

  8. Coulomb sum rules in the relativistic Fermi gas model

    International Nuclear Information System (INIS)

    Do Dang, G.; L'Huillier, M.; Nguyen Giai, Van.

    1986-11-01

    Coulomb sum rules are studied in the framework of the Fermi gas model. A distinction is made between mathematical and observable sum rules. Differences between non-relativistic and relativistic Fermi gas predictions are stressed. A method to deduce a Coulomb response function from the longitudinal response is proposed and tested numerically. This method is applied to the 40 Ca data to obtain the experimental Coulomb sum rule as a function of momentum transfer

  9. Simulation modelling for new gas turbine fuel controller creation.

    Science.gov (United States)

    Vendland, L. E.; Pribylov, V. G.; Borisov, Yu A.; Arzamastsev, M. A.; Kosoy, A. A.

    2017-11-01

    State of the art gas turbine fuel flow control systems are based on throttle principle. Major disadvantage of such systems is that they require high pressure fuel intake. Different approach to fuel flow control is to use regulating compressor. And for this approach because of controller and gas turbine interaction a specific regulating compressor is required. Difficulties emerge as early as the requirement definition stage. To define requirements for new object, his properties must be known. Simulation modelling helps to overcome these difficulties. At the requirement definition stage the most simplified mathematical model is used. Mathematical models will get more complex and detailed as we advance in planned work. If future adjusting of regulating compressor physical model to work with virtual gas turbine and physical control system is planned.

  10. A self-consistent model of cosmic-ray fluxes and positron excess: roles of nearby pulsars and a sub-dominant source population

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Jagdish C.; Razzaque, Soebur, E-mail: jjagdish@uj.ac.za, E-mail: srazzaque@uj.ac.za [Department of Physics, University of Johannesburg, P. O. Box 524, Auckland Park 2006 (South Africa)

    2017-09-01

    The cosmic-ray positron flux calculated using the cosmic-ray nuclei interactions in our Galaxy cannot explain observed data above 10 GeV. An excess in the measured positron flux is therefore open to interpretation. Nearby pulsars, located within sub-kiloparsec range of the Solar system, are often invoked as plausible sources contributing to the excess. We show that an additional, sub-dominant population of sources together with the contributions from a few nearby pulsars can explain the latest positron excess data from the Alpha Magnetic Spectrometer (AMS). We simultaneously model, using the DRAGON code, propagation of cosmic-ray proton, Helium, electron and positron and fit their respective flux data. Our fit to the Boron to Carbon ratio data gives a diffusion spectral index of 0.45, which is close to the Kraichnan turbulent spectrum.

  11. Evaluation of green house gas emissions models.

    Science.gov (United States)

    2014-11-01

    The objective of the project is to evaluate the GHG emissions models used by transportation agencies and industry leaders. Factors in the vehicle : operating environment that may affect modal emissions, such as, external conditions, : vehicle fleet c...

  12. Ecological model of the interprise danger of gas

    International Nuclear Information System (INIS)

    Sadygov, A.B.

    2009-01-01

    It has been looked into the basic problems for establishment of ecological model of the enterprise danger of gas. There have been established mathematical model in the base of equation of Novye-Stoks which consists of private reproductive second row differential equation system of three

  13. Effective-Medium Models for Marine Gas Hydrates, Mallik Revisited

    Science.gov (United States)

    Terry, D. A.; Knapp, C. C.; Knapp, J. H.

    2011-12-01

    Hertz-Mindlin type effective-medium dry-rock elastic models have been commonly used for more than three decades in rock physics analysis, and recently have been applied to assessment of marine gas hydrate resources. Comparisons of several effective-medium models with derivative well-log data from the Mackenzie River Valley, Northwest Territories, Canada (i.e. Mallik 2L-38 and 5L-38) were made several years ago as part of a marine gas hydrate joint industry project in the Gulf of Mexico. The matrix/grain supporting model (one of the five models compared) was clearly a better representation of the Mallik data than the other four models (2 cemented sand models; a pore-filling model; and an inclusion model). Even though the matrix/grain supporting model was clearly better, reservations were noted that the compressional velocity of the model was higher than the compressional velocity measured via the sonic logs, and that the shear velocities showed an even greater discrepancy. Over more than thirty years, variations of Hertz-Mindlin type effective medium models have evolved for unconsolidated sediments and here, we briefly review their development. In the past few years, the perfectly smooth grain version of the Hertz-Mindlin type effective-medium model has been favored over the infinitely rough grain version compared in the Gulf of Mexico study. We revisit the data from the Mallik wells to review assertions that effective-medium models with perfectly smooth grains are a better predictor than models with infinitely rough grains. We briefly review three Hertz-Mindlin type effective-medium models, and standardize nomenclature and notation. To calibrate the extended effective-medium model in gas hydrates, we use a well accepted framework for unconsolidated sediments through Hashin-Shtrikman bounds. We implement the previously discussed effective-medium models for saturated sediments with gas hydrates and compute theoretical curves of seismic velocities versus gas hydrate

  14. Potential biodefense model applications for portable chlorine dioxide gas production.

    Science.gov (United States)

    Stubblefield, Jeannie M; Newsome, Anthony L

    2015-01-01

    Development of decontamination methods and strategies to address potential infectious disease outbreaks and bioterrorism events are pertinent to this nation's biodefense strategies and general biosecurity. Chlorine dioxide (ClO2) gas has a history of use as a decontamination agent in response to an act of bioterrorism. However, the more widespread use of ClO2 gas to meet current and unforeseen decontamination needs has been hampered because the gas is too unstable for shipment and must be prepared at the application site. Newer technology allows for easy, onsite gas generation without the need for dedicated equipment, electricity, water, or personnel with advanced training. In a laboratory model system, 2 unique applications (personal protective equipment [PPE] and animal skin) were investigated in the context of potential development of decontamination protocols. Such protocols could serve to reduce human exposure to bacteria in a decontamination response effort. Chlorine dioxide gas was capable of reducing (2-7 logs of vegetative and spore-forming bacteria), and in some instances eliminating, culturable bacteria from difficult to clean areas on PPE facepieces. The gas was effective in eliminating naturally occurring bacteria on animal skin and also on skin inoculated with Bacillus spores. The culturable bacteria, including Bacillus spores, were eliminated in a time- and dose-dependent manner. Results of these studies suggested portable, easily used ClO2 gas generation systems have excellent potential for protocol development to contribute to biodefense strategies and decontamination responses to infectious disease outbreaks or other biothreat events.

  15. A multiple-location model for natural gas forward curves

    International Nuclear Information System (INIS)

    Buffington, J.C.

    1999-06-01

    This thesis presents an approach for financial modelling of natural gas in which connections between locations are incorporated and the complexities of forward curves in natural gas are considered. Apart from electricity, natural gas is the most volatile commodity traded. Its price is often dependent on the weather and price shocks can be felt across several geographic locations. This modelling approach incorporates multiple risk factors that correspond to various locations. One of the objectives was to determine if the model could be used for closed-form option prices. It was suggested that an adequate model for natural gas must consider 3 statistical properties: volatility term structure, backwardation and contango, and stochastic basis. Data from gas forward prices at Chicago, NYMEX and AECO were empirically tested to better understand these 3 statistical properties at each location and to verify if the proposed model truly incorporates these properties. In addition, this study examined the time series property of the difference of two locations (the basis) and determines that these empirical properties are consistent with the model properties. Closed-form option solutions were also developed for call options of forward contracts and call options on forward basis. The options were calibrated and compared to other models. The proposed model is capable of pricing options, but the prices derived did not pass the test of economic reasonableness. However, the model was able to capture the effect of transportation as well as aspects of seasonality which is a benefit over other existing models. It was determined that modifications will be needed regarding the estimation of the convenience yields. 57 refs., 2 tabs., 7 figs., 1 append

  16. Chemical equilibrium models of interstellar gas clouds

    International Nuclear Information System (INIS)

    Freeman, A.

    1982-10-01

    This thesis contains work which helps towards our understanding of the chemical processes and astrophysical conditions in interstellar clouds, across the whole range of cloud types. The object of the exercise is to construct a mathematical model representing a large system of two-body chemical reactions in order to deduce astrophysical parameters and predict molecular abundances and chemical pathways. Comparison with observations shows that this type of model is valid but also indicates that our knowledge of some chemical reactions is incomplete. (author)

  17. An Equilibrium-Based Model of Gas Reaction and Detonation

    International Nuclear Information System (INIS)

    Trowbridge, L.D.

    2000-01-01

    During gaseous diffusion plant operations, conditions leading to the formation of flammable gas mixtures may occasionally arise. Currently, these could consist of the evaporative coolant CFC-114 and fluorinating agents such as F2 and ClF3. Replacement of CFC-114 with a non-ozone-depleting substitute is planned. Consequently, in the future, the substitute coolant must also be considered as a potential fuel in flammable gas mixtures. Two questions of practical interest arise: (1) can a particular mixture sustain and propagate a flame if ignited, and (2) what is the maximum pressure that can be generated by the burning (and possibly exploding) gas mixture, should it ignite? Experimental data on these systems, particularly for the newer coolant candidates, are limited. To assist in answering these questions, a mathematical model was developed to serve as a tool for predicting the potential detonation pressures and for estimating the composition limits of flammability for these systems based on empirical correlations between gas mixture thermodynamics and flammability for known systems. The present model uses the thermodynamic equilibrium to determine the reaction endpoint of a reactive gas mixture and uses detonation theory to estimate an upper bound to the pressure that could be generated upon ignition. The model described and documented in this report is an extended version of related models developed in 1992 and 1999

  18. Environmental control implications of generating electric power from coal. 1977 technology status report. Appendix D. Assessment of NO/sub x/ control technology for coal fired utility boilers. [Low-excess-air, staged combustion, flu gas recirculation and burner design

    Energy Technology Data Exchange (ETDEWEB)

    1977-12-01

    An NOx control technology assessment study was conducted to examine the effectiveness of low-excess-air firing, staged combustion, flue gas recirculation, and current burner/boiler designs as applied to coal-fired utility boilers. Significant variations in NOx emissions exist with boiler type, firing method, and coal type, but a relative comparison of emissions control performance, cost, and operational considerations is presented for each method. The study emphasized the numerous operational factors that are of major importance to the user in selecting and implementing a combustion modification technique. Staged combustion and low-excess-air operation were identified as the most cost-effective methods for existing units. Close control of local air/fuel ratios and rigorous combustion equipment maintenance are essential to the success of both methods. Flue gas recirculation is relatively ineffective and has the added concern of tube erosion. More research is needed to resolve potential corrosion concerns with low-NOx operating modes. Low-NOx burners in conjunction with a compartmentalized windbox are capable of meeting a 0.6-lb/million Btu emission level on new units. Advanced burner designs are being developed to meet research emission goals of approximately 0.25 lb/MBtu.

  19. Model documentation Natural Gas Transmission and Distribution Model of the National Energy Modeling System. Volume 1

    International Nuclear Information System (INIS)

    1996-01-01

    The Natural Gas Transmission and Distribution Model (NGTDM) of the National Energy Modeling System is developed and maintained by the Energy Information Administration (EIA), Office of Integrated Analysis and Forecasting. This report documents the archived version of the NGTDM that was used to produce the natural gas forecasts presented in the Annual Energy Outlook 1996, (DOE/EIA-0383(96)). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic approach, and provides detail on the methodology employed. Previously this report represented Volume I of a two-volume set. Volume II reported on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues

  20. Model documentation Natural Gas Transmission and Distribution Model of the National Energy Modeling System. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-02-26

    The Natural Gas Transmission and Distribution Model (NGTDM) of the National Energy Modeling System is developed and maintained by the Energy Information Administration (EIA), Office of Integrated Analysis and Forecasting. This report documents the archived version of the NGTDM that was used to produce the natural gas forecasts presented in the Annual Energy Outlook 1996, (DOE/EIA-0383(96)). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic approach, and provides detail on the methodology employed. Previously this report represented Volume I of a two-volume set. Volume II reported on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues.

  1. Development of a natural Gas Systems Analysis Model (GSAM)

    International Nuclear Information System (INIS)

    1994-02-01

    Lacking a detailed characterization of the resource base and a comprehensive borehole-to-burnertip evaluation model of the North American natural gas system, past R ampersand D, tax and regulatory policies have been formulated without a full understanding of their likely direct and indirect impacts on future gas supply and demand. The recent disappearance of the deliverability surplus, pipeline deregulation, and current policy debates about regulatory initiatives in taxation, environmental compliance and leasing make the need for a comprehensive gas evaluation system critical. Traditional econometric or highly aggregated energy models are increasingly regarded as unable to incorporate available geologic detail and explicit technology performance and costing algorithms necessary to evaluate resource-technology-economic interactions in a market context. The objective of this research is to create a comprehensive, non-proprietary, microcomputer model of the North American natural gas system. GSAM explicitly evaluates the key components of the natural gas system, including resource base, exploration and development, extraction technology performance and costs, transportation and storage and end use. The primary focus is the detailed characterization of the resource base at the reservoir and sub-reservoir level and the impact of alternative extraction technologies on well productivity and economics. GSAM evaluates the complex interactions of current and alternative future technology and policy initiatives in the context of the evolving gas markets. Scheduled for completion in 1995, a prototype is planned for early 1994. ICF Resources reviewed relevant natural gas upstream, downstream and market models to identify appropriate analytic capabilities to incorporate into GSAM. We have reviewed extraction technologies to better characterize performance and costs in terms of GSAM parameters

  2. Considerations in modeling fission gas release during normal operation

    International Nuclear Information System (INIS)

    Rumble, E.T.; Lim, E.Y.; Stuart, R.G.

    1977-01-01

    The EPRI LWR fuel rod modeling code evaluation program analyzed seven fuel rods with experimental fission gas release data. In these cases, rod-averged burnups are less than 20,000 MWD/MTM, while the fission gas release fractions range roughly from 2 to 27%. Code results demonstrate the complexities in calculating fission gas release in certain operating regimes. Beyond this work, the behavior of a pre-pressurized PWR rod is simulated to average burnups of 40,000 MWD/MTM using GAPCON-THERMAL-2. Analysis of the sensitivity of fission gas release to power histories and release correlations indicate the strong impact that LMFBR type release correlations induce at high burnup. 15 refs

  3. 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)

  4. Exhaust gas recirculation – Zero dimensional modelling and characterization for transient diesel combustion control

    International Nuclear Information System (INIS)

    Asad, Usman; Tjong, Jimi; Zheng, Ming

    2014-01-01

    Highlights: • Zero-dimensional EGR model for transient diesel combustion control. • Detailed analysis of EGR effects on intake, cylinder charge and exhaust properties. • Intake oxygen validated as an operating condition-independent measure of EGR. • Quantified EGR effectiveness in terms of NOx emission reduction. • Twin lambda sensor technique for estimation of EGR/in-cylinder parameters. - Abstract: The application of exhaust gas recirculation (EGR) during transient engine operation is a challenging task since small fluctuations in EGR may cause larger than acceptable spikes in NOx/soot emissions or deterioration in the combustion efficiency. Moreover, the intake charge dilution at any EGR ratio is a function of engine load and intake pressure, and typically changes during transient events. Therefore, the management of EGR during transient engine operation or advanced combustion cycles (that are inherently less stable) requires a fundamental understanding of the transient EGR behaviour and its impact on the intake charge development. In this work, a zero-dimensional EGR model is described to estimate the transient (cycle-by-cycle) progression of EGR and the time (engine cycles) required for its stabilization. The model response is tuned to a multi-cylinder engine by using an overall engine system time-constant and shown to effectively track the transient EGR changes. The impact of EGR on the actual air–fuel ratio of the cylinder charge is quantified by defining an in-cylinder excess-air ratio that accounts for the oxygen in the recycled exhaust gas. Furthermore, a twin lambda sensor (TLS) technique is implemented for tracking the intake dilution and in-cylinder excess-air ratio in real-time. The modelling and analysis results are validated against a wide range of engine operations, including transient and steady-state low temperature combustion tests

  5. A structural comparison of the responses of US natural gas models

    International Nuclear Information System (INIS)

    Huntington, H.G.

    1989-01-01

    The EMF 9 scenarios were designed to elicit insights about possible future natural gas market conditions under alternative resource, demand, and oil price trends. These cases are also useful for probing the models themselves because the reported results for the different scenarios reveal important information about the behavioral responses represented in each model. This paper compares these responses in order to explain why they differ and what are the implications of these differences for analyzing gas markets. The integrating framework for this model comparison is a rudimentary supply-demand analysis of market forces that has been successfully applied to many commodity markets. A central theme in this approach is that supply and demand imbalances will eventually be rectified through an adjustment in prices that eliminates excess supply or demand. While this approach abstracts from the important regulatory and institutional constraints, it focuses attention on the growing importance of price determination in a gas market that has fast become integrated nationally as well as internationally. The recently signed and ratified Canadian-US Free Trade Agreement commits both governments not to restrict energy imports or exports or to impose minimum export price requirements, except under special conditions. As competitive forces become more important within the gas industry, this paradigm appears appropriate for probing key long-term relationships critical to this fuel's future. This paper focuses on the responses in total consumption, production, average wellhead price, and average delivered price in the United States for the eight models reporting these variables. Results are reported for 2000, which represent mid- to long-term adjustments for the most part. Responses for other years are shown in Appendix B and those for Canada in Appendix D

  6. Model simulation for high-temperature gas desulphurization processes

    Energy Technology Data Exchange (ETDEWEB)

    Tonini; Zaccagnini; Berg; Vitolo; Tartarelli; Zeppi (Struttura Informatica, Florence (Italy))

    1993-01-01

    Metal oxides such as zinc ferrite, zinc titanate and tin oxide have been identified as promising adsorbent materials in the removal of sulphur compounds from hot coal gas in power generation operations. A mathematical model for the sulfidation phase in fixed, moving and fluidised bed reactors has been developed. This paper presents kinetic models of spherical sorbent particles applicable to all reactor configurations and a mathematical model limited to the moving bed reactor. 10 refs., 5 figs.

  7. Understanding the effect of an excessive cold tongue bias on projecting the tropical Pacific SST warming pattern in CMIP5 models

    Science.gov (United States)

    Ying, Jun; Huang, Ping; Lian, Tao; Tan, Hongjian

    2018-05-01

    An excessive cold tongue is a common bias among current climate models, and considered an important source of bias in projections of tropical Pacific climate change under global warming. Specifically, the excessive cold tongue bias is closely related to the tropical Pacific SST warming (TPSW) pattern. In this study, we reveal that two processes are the critical mechanisms by which the excessive cold tongue bias influences the projection of the TPSW pattern, based on 32 models from phase 5 of Coupled Model Intercomparison Projection (CMIP5). On the one hand, by assuming that the shortwave (SW) radiation to SST feedback is linearly correlated to the cold tongue SST, the excessive cold tongue bias can induce an overly weak negative SW-SST feedback in the central Pacific, which can lead to a positive SST warming bias in the central to western Pacific (around 150°E-140°W). Moreover, the overly weak local atmospheric dynamics response to SST is a key process of the overly weak SW-SST feedback, compared with the cloud response to atmospheric dynamics and the SW radiation response to cloud. On the other hand, the overly strong ocean zonal overturning circulation associated with the excessive cold tongue bias results in an overestimation of the ocean dynamical thermostat effect, with enhanced ocean stratification under global warming, leading to a negative SST warming bias in the central and eastern Pacific (around 170°W-120°W). These two processes jointly form a positive SST warming bias in the western Pacific, contributing to a La Niña-like warming bias. Therefore, we suggest a more realistic climatological cold tongue SST is needed for a more reliable projection of the TPSW pattern.

  8. How rapidly does the excess risk of lung cancer decline following quitting smoking? A quantitative review using the negative exponential model.

    Science.gov (United States)

    Fry, John S; Lee, Peter N; Forey, Barbara A; Coombs, Katharine J

    2013-10-01

    The excess lung cancer risk from smoking declines with time quit, but the shape of the decline has never been precisely modelled, or meta-analyzed. From a database of studies of at least 100 cases, we extracted 106 blocks of RRs (from 85 studies) comparing current smokers, former smokers (by time quit) and never smokers. Corresponding pseudo-numbers of cases and controls (or at-risk) formed the data for fitting the negative exponential model. We estimated the half-life (H, time in years when the excess risk becomes half that for a continuing smoker) for each block, investigated model fit, and studied heterogeneity in H. We also conducted sensitivity analyses allowing for reverse causation, either ignoring short-term quitters (S1) or considering them smokers (S2). Model fit was poor ignoring reverse causation, but much improved for both sensitivity analyses. Estimates of H were similar for all three analyses. For the best-fitting analysis (S1), H was 9.93 (95% CI 9.31-10.60), but varied by sex (females 7.92, males 10.71), and age (<50years 6.98, 70+years 12.99). Given that reverse causation is taken account of, the model adequately describes the decline in excess risk. However, estimates of H may be biased by factors including misclassification of smoking status. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  9. 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.

  10. 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)

  11. A heuristic model to quantify the impact of excess cyclodextrin on oral drug absorption from aqueous solution

    DEFF Research Database (Denmark)

    Olesen, Niels Erik; Westh, Peter; Holm, René

    2016-01-01

    , the cyclodextrin concentration in the drug product must be higher than the amount needed to solubilise the compound, due to the displacement of the drug from the cyclodextrin cavity by bile salts in the intestinal lumen. On the other hand, dosing cyclodextrin at View the MathML source>DtotSC is expected to result...... the implication of having excess cyclodextrin in an oral solution....

  12. Off-gas adsorption model and simulation - OSPREY

    Energy Technology Data Exchange (ETDEWEB)

    Rutledge, V.J. [Idaho National Laboratory, P. O. Box 1625, Idaho Falls, ID (United States)

    2013-07-01

    A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes is expected to provide substantial cost savings and many technical benefits. To support this capability, a modeling effort focused on the off-gas treatment system of a used nuclear fuel recycling facility is in progress. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed within Multi-physics Object Oriented Simulation Environment (MOOSE) developed at the Idaho National Laboratory (INL). Off-gas Separation and Recovery (OSPREY) models the adsorption of offgas constituents for dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions. Inputs to the model include gas composition, sorbent and column properties, equilibrium and kinetic data, and inlet conditions. The simulation outputs component concentrations along the column length as a function of time from which breakthrough data can be obtained. The breakthrough data can be used to determine bed capacity, which in turn can be used to size columns. In addition to concentration data, the model predicts temperature along the column length as a function of time and pressure drop along the column length. A description of the OSPREY model, results from krypton adsorption modeling and plans for modeling the behavior of iodine, xenon, and tritium will be discussed. (author)

  13. A Statistical Model for the Estimation of Natural Gas Consumption

    Czech Academy of Sciences Publication Activity Database

    Vondráček, Jiří; Pelikán, Emil; Konár, Ondřej; Čermáková, Jana; Eben, Kryštof; Malý, Marek; Brabec, Marek

    2008-01-01

    Roč. 85, c. 5 (2008), s. 362-370 ISSN 0306-2619 R&D Projects: GA AV ČR 1ET400300513 Institutional research plan: CEZ:AV0Z10300504 Keywords : nonlinear regression * gas consumption modeling Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 1.371, year: 2008

  14. 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

  15. Model-based dynamic control and optimization of gas networks

    Energy Technology Data Exchange (ETDEWEB)

    Hofsten, Kai

    2001-07-01

    This work contributes to the research on control, optimization and simulation of gas transmission systems to support the dispatch personnel at gas control centres for the decision makings in the daily operation of the natural gas transportation systems. Different control and optimization strategies have been studied. The focus is on the operation of long distance natural gas transportation systems. Stationary optimization in conjunction with linear model predictive control using state space models is proposed for supply security, the control of quality parameters and minimization of transportation costs for networks offering transportation services. The result from the stationary optimization together with a reformulation of a simplified fluid flow model formulates a linear dynamic optimization model. This model is used in a finite time control and state constrained linear model predictive controller. The deviation from the control and the state reference determined from the stationary optimization is penalized quadratically. Because of the time varying status of infrastructure, the control space is also generally time varying. When the average load is expected to change considerably, a new stationary optimization is performed, giving a new state and control reference together with a new dynamic model that is used for both optimization and state estimation. Another proposed control strategy is a control and output constrained nonlinear model predictive controller for the operation of gas transmission systems. Here, the objective is also the security of the supply, quality control and minimization of transportation costs. An output vector is defined, which together with a control vector are both penalized quadratically from their respective references in the objective function. The nonlinear model predictive controller can be combined with a stationary optimization. At each sampling instant, a non convex nonlinear programming problem is solved giving a local minimum

  16. An integration scheme for stiff solid-gas reactor models

    Directory of Open Access Journals (Sweden)

    Bjarne A. Foss

    2001-04-01

    Full Text Available Many dynamic models encounter numerical integration problems because of a large span in the dynamic modes. In this paper we develop a numerical integration scheme for systems that include a gas phase, and solid and liquid phases, such as a gas-solid reactor. The method is based on neglecting fast dynamic modes and exploiting the structure of the algebraic equations. The integration method is suitable for a large class of industrially relevant systems. The methodology has proven remarkably efficient. It has in practice performed excellent and been a key factor for the success of the industrial simulator for electrochemical furnaces for ferro-alloy production.

  17. Microeconomics of the ideal gas like market models

    Science.gov (United States)

    Chakrabarti, Anindya S.; Chakrabarti, Bikas K.

    2009-10-01

    We develop a framework based on microeconomic theory from which the ideal gas like market models can be addressed. A kinetic exchange model based on that framework is proposed and its distributional features have been studied by considering its moments. Next, we derive the moments of the CC model (Eur. Phys. J. B 17 (2000) 167) as well. Some precise solutions are obtained which conform with the solutions obtained earlier. Finally, an output market is introduced with global price determination in the model with some necessary modifications.

  18. Natural Gas Transmission and Distribution Model of the National Energy Modeling System. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-01-01

    The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. The NGTDM is the model within the NEMS that represents the transmission, distribution, and pricing of natural gas. The model also includes representations of the end-use demand for natural gas, the production of domestic natural gas, and the availability of natural gas traded on the international market based on information received from other NEMS models. The NGTDM determines the flow of natural gas in an aggregate, domestic pipeline network, connecting domestic and foreign supply regions with 12 demand regions. The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic design, provides detail on the methodology employed, and describes the model inputs, outputs, and key assumptions. Subsequent chapters of this report provide: an overview of NGTDM; a description of the interface between the NEMS and NGTDM; an overview of the solution methodology of the NGTDM; the solution methodology for the Annual Flow Module; the solution methodology for the Distributor Tariff Module; the solution methodology for the Capacity Expansion Module; the solution methodology for the Pipeline Tariff Module; and a description of model assumptions, inputs, and outputs.

  19. Model documentation: Natural Gas Transmission and Distribution Model of the National Energy Modeling System; Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1994-02-24

    The Natural Gas Transmission and Distribution Model (NGTDM) is a component of the National Energy Modeling System (NEMS) used to represent the domestic natural gas transmission and distribution system. NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the Energy Information Administration (EIA) and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. This report documents the archived version of NGTDM that was used to produce the natural gas forecasts used in support of the Annual Energy Outlook 1994, DOE/EIA-0383(94). The purpose of this report is to provide a reference document for model analysts, users, and the public that defines the objectives of the model, describes its basic design, provides detail on the methodology employed, and describes the model inputs, outputs, and key assumptions. It is intended to fulfill the legal obligation of the EIA to provide adequate documentation in support of its models (Public Law 94-385, Section 57.b.2). This report represents Volume 1 of a two-volume set. (Volume 2 will report on model performance, detailing convergence criteria and properties, results of sensitivity testing, comparison of model outputs with the literature and/or other model results, and major unresolved issues.) Subsequent chapters of this report provide: (1) an overview of the NGTDM (Chapter 2); (2) a description of the interface between the National Energy Modeling System (NEMS) and the NGTDM (Chapter 3); (3) an overview of the solution methodology of the NGTDM (Chapter 4); (4) the solution methodology for the Annual Flow Module (Chapter 5); (5) the solution methodology for the Distributor Tariff Module (Chapter 6); (6) the solution methodology for the Capacity Expansion Module (Chapter 7); (7) the solution methodology for the Pipeline Tariff Module (Chapter 8); and (8) a description of model assumptions, inputs, and outputs (Chapter 9).

  20. A heterogeneous lattice gas model for simulating pedestrian evacuation

    Science.gov (United States)

    Guo, Xiwei; Chen, Jianqiao; Zheng, Yaochen; Wei, Junhong

    2012-02-01

    Based on the cellular automata method (CA model) and the mobile lattice gas model (MLG model), we have developed a heterogeneous lattice gas model for simulating pedestrian evacuation processes in an emergency. A local population density concept is introduced first. The update rule in the new model depends on the local population density and the exit crowded degree factor. The drift D, which is one of the key parameters influencing the evacuation process, is allowed to change according to the local population density of the pedestrians. Interactions including attraction, repulsion, and friction between every two pedestrians and those between a pedestrian and the building wall are described by a nonlinear function of the corresponding distance, and the repulsion forces increase sharply as the distances get small. A critical force of injury is introduced into the model, and its effects on the evacuation process are investigated. The model proposed has heterogeneous features as compared to the MLG model or the basic CA model. Numerical examples show that the model proposed can capture the basic features of pedestrian evacuation, such as clogging and arching phenomena.

  1. Towards the simplest hydrodynamic lattice-gas model.

    Science.gov (United States)

    Boghosian, Bruce M; Love, Peter J; Meyer, David A

    2002-03-15

    It has been known since 1986 that it is possible to construct simple lattice-gas cellular automata whose hydrodynamics are governed by the Navier-Stokes equations in two dimensions. The simplest such model heretofore known has six bits of state per site on a triangular lattice. In this work, we demonstrate that it is possible to construct a model with only five bits of state per site on a Kagome lattice. Moreover, the model has a simple, deterministic set of collision rules and is easily implemented on a computer. In this work, we derive the equilibrium distribution function for this lattice-gas automaton and carry out the Chapman-Enskog analysis to determine the form of the Navier-Stokes equations.

  2. Environmental Parametric Cost Model in Oil and Gas EPC Contracts

    Directory of Open Access Journals (Sweden)

    Madjid Abbaspour

    2018-01-01

    Full Text Available This study aims at identifying the parameters that govern the environmental costs in oil and gas projects. An initial conceptual model was proposed. Next, the costs of environmental management work packages were estimated, separately and were applied in project control tools (WBS/CBS. Then, an environmental parametric cost model was designed to determine the environmental costs and relevant weighting factors. The suggested model can be considered as an innovative approach to designate the environmental indicators in oil and gas projects. The validity of variables was investigated based on Delphi method. The results indicated that the project environmental management’s weighting factor is 0.87% of total project’s weighting factor.

  3. Neural network models for biological waste-gas treatment systems.

    Science.gov (United States)

    Rene, Eldon R; Estefanía López, M; Veiga, María C; Kennes, Christian

    2011-12-15

    This paper outlines the procedure for developing artificial neural network (ANN) based models for three bioreactor configurations used for waste-gas treatment. The three bioreactor configurations chosen for this modelling work were: biofilter (BF), continuous stirred tank bioreactor (CSTB) and monolith bioreactor (MB). Using styrene as the model pollutant, this paper also serves as a general database of information pertaining to the bioreactor operation and important factors affecting gas-phase styrene removal in these biological systems. Biological waste-gas treatment systems are considered to be both advantageous and economically effective in treating a stream of polluted air containing low to moderate concentrations of the target contaminant, over a rather wide range of gas-flow rates. The bioreactors were inoculated with the fungus Sporothrix variecibatus, and their performances were evaluated at different empty bed residence times (EBRT), and at different inlet styrene concentrations (C(i)). The experimental data from these bioreactors were modelled to predict the bioreactors performance in terms of their removal efficiency (RE, %), by adequate training and testing of a three-layered back propagation neural network (input layer-hidden layer-output layer). Two models (BIOF1 and BIOF2) were developed for the BF with different combinations of easily measurable BF parameters as the inputs, that is concentration (gm(-3)), unit flow (h(-1)) and pressure drop (cm of H(2)O). The model developed for the CSTB used two inputs (concentration and unit flow), while the model for the MB had three inputs (concentration, G/L (gas/liquid) ratio, and pressure drop). Sensitivity analysis in the form of absolute average sensitivity (AAS) was performed for all the developed ANN models to ascertain the importance of the different input parameters, and to assess their direct effect on the bioreactors performance. The performance of the models was estimated by the regression

  4. Reaction of a phospholipid monolayer with gas-phase ozone at the air-water interface: measurement of surface excess and surface pressure in real time.

    Science.gov (United States)

    Thompson, Katherine C; Rennie, Adrian R; King, Martin D; Hardman, Samantha J O; Lucas, Claire O M; Pfrang, Christian; Hughes, Brian R; Hughes, Arwel V

    2010-11-16

    The reaction between gas-phase ozone and monolayers of the unsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC, on aqueous solutions has been studied in real time using neutron reflection and surface pressure measurements. The reaction between ozone and lung surfactant, which contains POPC, leads to decreased pulmonary function, but little is known about the changes that occur to the interfacial material as a result of oxidation. The results reveal that the initial reaction of ozone with POPC leads to a rapid increase in surface pressure followed by a slow decrease to very low values. The neutron reflection measurements, performed on an isotopologue of POPC with a selectively deuterated palmitoyl strand, reveal that the reaction leads to loss of this strand from the air-water interface, suggesting either solubilization of the product lipid or degradation of the palmitoyl strand by a reactive species. Reactions of (1)H-POPC on D(2)O reveal that the headgroup region of the lipids in aqueous solution is not dramatically perturbed by the reaction of POPC monolayers with ozone supporting degradation of the palmitoyl strand rather than solubilization. The results are consistent with the reaction of ozone with the oleoyl strand of POPC at the air-water interface leading to the formation of OH radicals. The highly reactive OH radicals produced can then go on to react with the saturated palmitoyl strands leading to the formation of oxidized lipids with shorter alkyl tails.

  5. Modelling of gas generation in deep geological repositories after closure

    International Nuclear Information System (INIS)

    Poller, A.; Mayer, G.; Darcis M; Smith, P.

    2016-12-01

    In deep geological repositories for radioactive waste, significant quantities of gases will be generated in the long term as a result of various processes, notably the anaerobic corrosion of metals and the degradation of organic materials. Therefore, the impact of gas production on post-closure safety of the repositories needs to be assessed as part of a safety case. The present report provides a comprehensive description of the quantitative modelling of gas generation and associated water consumption during the post-closure phase of deep geological repositories in Opalinus Clay based on current scientific knowledge and on current preliminary repository designs. This includes a presentation of the modelling basis, namely the conceptual and mathematical models, the input data used, the computer tools developed, the relevant uncertainties and principal programme / design options, as well as the derivation, analysis and discussion of specific assessment cases. The modelling is carried out separately for the two main sources of gas, which are the emplaced waste including the disposal containers; and the construction materials. The contribution of construction materials to gas generation rates in emplacement tunnels for spent fuel (SF) and vitrified high-level waste (HLW) is significant during several thousand years after closure. In the long term, however, the corrosion of the disposal canisters, which are in the reference case assumed to be fabricated of carbon steel, accounts for the vast majority of the total gas produced in these tunnels. The contribution of construction materials in emplacement caverns for long lived intermediate-level waste (ILW) and low- and intermediate-level waste (L/ILW) to gas generation is generally small. In ILW emplacement caverns, gas generation is generally dominated by hydrogen generation from the corrosion of cast iron Mosaik-II waste containers for PWR internals and from the corrosion of aluminium in operational waste from the

  6. Modelling of gas generation in deep geological repositories after closure

    Energy Technology Data Exchange (ETDEWEB)

    Poller, A. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); Mayer, G.; Darcis M [AF-Consult Switzerland Ltd, Baden-Dättwil, (Switzerland); Smith, P. [Safety Assessment Management Ltd, Henley-On-Thames, Oxfordshire (United Kingdom)

    2016-12-15

    In deep geological repositories for radioactive waste, significant quantities of gases will be generated in the long term as a result of various processes, notably the anaerobic corrosion of metals and the degradation of organic materials. Therefore, the impact of gas production on post-closure safety of the repositories needs to be assessed as part of a safety case. The present report provides a comprehensive description of the quantitative modelling of gas generation and associated water consumption during the post-closure phase of deep geological repositories in Opalinus Clay based on current scientific knowledge and on current preliminary repository designs. This includes a presentation of the modelling basis, namely the conceptual and mathematical models, the input data used, the computer tools developed, the relevant uncertainties and principal programme / design options, as well as the derivation, analysis and discussion of specific assessment cases. The modelling is carried out separately for the two main sources of gas, which are the emplaced waste including the disposal containers; and the construction materials. The contribution of construction materials to gas generation rates in emplacement tunnels for spent fuel (SF) and vitrified high-level waste (HLW) is significant during several thousand years after closure. In the long term, however, the corrosion of the disposal canisters, which are in the reference case assumed to be fabricated of carbon steel, accounts for the vast majority of the total gas produced in these tunnels. The contribution of construction materials in emplacement caverns for long lived intermediate-level waste (ILW) and low- and intermediate-level waste (L/ILW) to gas generation is generally small. In ILW emplacement caverns, gas generation is generally dominated by hydrogen generation from the corrosion of cast iron Mosaik-II waste containers for PWR internals and from the corrosion of aluminium in operational waste from the

  7. Off-Gas Adsorption Model Capabilities and Recommendations

    Energy Technology Data Exchange (ETDEWEB)

    Lyon, Kevin L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Welty, Amy K. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Law, Jack [Idaho National Lab. (INL), Idaho Falls, ID (United States); Ladshaw, Austin [Georgia Inst. of Technology, Atlanta, GA (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-03-01

    Off-gas treatment is required to reduce emissions from aqueous fuel reprocessing. Evaluating the products of innovative gas adsorption research requires increased computational simulation capability to more effectively transition from fundamental research to operational design. Early modeling efforts produced the Off-Gas SeParation and REcoverY (OSPREY) model that, while efficient in terms of computation time, was of limited value for complex systems. However, the computational and programming lessons learned in development of the initial model were used to develop Discontinuous Galerkin OSPREY (DGOSPREY), a more effective model. Initial comparisons between OSPREY and DGOSPREY show that, while OSPREY does reasonably well to capture the initial breakthrough time, it displays far too much numerical dispersion to accurately capture the real shape of the breakthrough curves. DGOSPREY is a much better tool as it utilizes a more stable set of numerical methods. In addition, DGOSPREY has shown the capability to capture complex, multispecies adsorption behavior, while OSPREY currently only works for a single adsorbing species. This capability makes DGOSPREY ultimately a more practical tool for real world simulations involving many different gas species. While DGOSPREY has initially performed very well, there is still need for improvement. The current state of DGOSPREY does not include any micro-scale adsorption kinetics and therefore assumes instantaneous adsorption. This is a major source of error in predicting water vapor breakthrough because the kinetics of that adsorption mechanism is particularly slow. However, this deficiency can be remedied by building kinetic kernels into DGOSPREY. Another source of error in DGOSPREY stems from data gaps in single species, such as Kr and Xe, isotherms. Since isotherm data for each gas is currently available at a single temperature, the model is unable to predict adsorption at temperatures outside of the set of data currently

  8. Solid-Gas Coupling Model for Coal-Rock Mass Deformation and Pressure Relief Gas Flow in Protection Layer Mining

    OpenAIRE

    Zhu, Zhuohui; Feng, Tao; Yuan, Zhigang; Xie, Donghai; Chen, Wei

    2018-01-01

    The solid-gas coupling model for mining coal-rock mass deformation and pressure relief gas flow in protection layer mining is the key to determine deformation of coal-rock mass and migration law of pressure relief gas of protection layer mining in outburst coal seams. Based on the physical coupling process between coal-rock mass deformation and pressure-relief gas migration, the coupling variable of mining coal-rock mass, a part of governing equations of gas seepage field and deformation fiel...

  9. Gas Generation in Radioactive Wastes - MAGGAS Predictive Life Cycle Model

    International Nuclear Information System (INIS)

    Streatfield, R.E.; Hebditch, D.J.; Swift, B.T.; Hoch, A.R.; Constable, M.

    2006-01-01

    Gases may form from radioactive waste in quantities posing different potential hazards throughout the waste package life cycle. The latter includes surface storage, transport, placing in an operating repository, storage in the repository prior to backfill, closure and the post-closure stage. Potentially hazardous situations involving gas include fire, flood, dropped packages, blocked package vents and disruption to a sealed repository. The MAGGAS (Magnox Gas generation) model was developed to assess gas formation for safety assessments during all stages of the waste package life cycle. This is a requirement of the U.K. regulatory authorities and Nirex and progress in this context is discussed. The processes represented in the model include: Corrosion, microbial degradation, radiolysis, solid-state diffusion, chemico-physical degradation and pressurisation. The calculation was split into three time periods. First the 'aerobic phase' is used to model the periods of surface storage, transport and repository operations including storage in the repository prior to backfill. The second and third periods were designated 'anaerobic phase 1' and 'anaerobic phase 2' and used to model the waste packages in the post-closure phase of the repository. The various significant gas production processes are modeled in each phase. MAGGAS (currently Version 8) is mounted on an Excel spreadsheet for ease of use and speed, has 22 worksheets and is operated routinely for assessing waste packages (e.g. for ventilation of stores and pressurisation of containers). Ten operational and decommissioning generic nuclear power station waste streams were defined as initial inputs, which included ion exchange materials, sludges and concentrates, fuel element debris, graphite debris, activated components, contaminated items, desiccants and catalysts. (authors)

  10. Sorption Modeling and Verification for Off-Gas Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Tavlarides, Lawrence [Syracuse Univ., NY (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Georgia Inst. of Technology, Atlanta, GA (United States); Gabitto, Jorge [Prairie View Texas A& M; DePaoli, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-12-20

    This project was successfully executed to provide valuable adsorption data and improve a comprehensive model developed in previous work by the authors. Data obtained were used in an integrated computer program to predict the behavior of adsorption columns. The model is supported by experimental data and has been shown to predict capture of off gas similar to that evolving during the reprocessing of nuclear waste. The computer program structure contains (a) equilibrium models of off-gases with the adsorbate; (b) mass-transfer models to describe off-gas mass transfer to a particle, diffusion through the pores of the particle, and adsorption on the active sites of the particle; and (c) incorporation of these models into fixed bed adsorption modeling, which includes advection through the bed. These models are being connected with the MOOSE (Multiphysics Object-Oriented Simulation Environment) software developed at the Idaho National Laboratory through DGOSPREY (Discontinuous Galerkin Off-gas SeParation and REcoverY) computer codes developed in this project. Experiments for iodine and water adsorption have been conducted on reduced silver mordenite (Ag0Z) for single layered particles. Adsorption apparatuses have been constructed to execute these experiments over a useful range of conditions for temperatures ranging from ambient to 250°C and water dew points ranging from -69 to 19°C. Experimental results were analyzed to determine mass transfer and diffusion of these gases into the particles and to determine which models best describe the single and binary component mass transfer and diffusion processes. The experimental results were also used to demonstrate the capabilities of the comprehensive models developed to predict single-particle adsorption and transients of the adsorption-desorption processes in fixed beds. Models for adsorption and mass transfer have been developed to mathematically describe adsorption kinetics and transport via diffusion and advection

  11. Modeling and analysis of the Rimfire gas switch

    International Nuclear Information System (INIS)

    Gahl, John M.; Kemp, Mark A.; Struve, Kenneth William; Curry, Randy D.; McDonald, Ken F.

    2005-01-01

    Many accelerators at Sandia National Laboratories utilize the Rimfire gas switch for high-voltage, high-power switching. Future accelerators will have increased performance requirements for switching elements. When designing improved versions of the Rimfire switch, there is a need for quick and accurate simulation of the electrical effects of geometry changes. This paper presents an advanced circuit model of the Rimfire switch that can be used for these simulations. The development of the model is shown along with comparisons to past models and experimental results.

  12. Gas leak detection in infrared video with background modeling

    Science.gov (United States)

    Zeng, Xiaoxia; Huang, Likun

    2018-03-01

    Background modeling plays an important role in the task of gas detection based on infrared video. VIBE algorithm is a widely used background modeling algorithm in recent years. However, the processing speed of the VIBE algorithm sometimes cannot meet the requirements of some real time detection applications. Therefore, based on the traditional VIBE algorithm, we propose a fast prospect model and optimize the results by combining the connected domain algorithm and the nine-spaces algorithm in the following processing steps. Experiments show the effectiveness of the proposed method.

  13. Version 2.0 of the European Gas Model. Changes and their impact on the German gas sector

    International Nuclear Information System (INIS)

    Balmert, David; Petrov, Konstantin

    2015-01-01

    In January 2015 ACER, the European Agency for the Cooperation of Energy Regulators, presented an updated version of its target model for the inner-European natural gas market, also referred to as version 2.0 of the Gas Target Model. During 2014 the existing model, originally developed by the Council of European Energy Regulators (CEER) and launched in 2011, had been analysed, revised and updated in preparation of the new version. While it has few surprises to offer, the new Gas Target Model contains specifies and goes into greater detail on many elements of the original model. Some of the new content is highly relevant to the German gas sector, not least the deliberations on the current key issues, which are security of supply and the ability of the gas markets to function.

  14. Study on Fluid-solid Coupling Mathematical Models and Numerical Simulation of Coal Containing Gas

    Science.gov (United States)

    Xu, Gang; Hao, Meng; Jin, Hongwei

    2018-02-01

    Based on coal seam gas migration theory under multi-physics field coupling effect, fluid-solid coupling model of coal seam gas was build using elastic mechanics, fluid mechanics in porous medium and effective stress principle. Gas seepage behavior under different original gas pressure was simulated. Results indicated that residual gas pressure, gas pressure gradient and gas low were bigger when original gas pressure was higher. Coal permeability distribution decreased exponentially when original gas pressure was lower than critical pressure. Coal permeability decreased rapidly first and then increased slowly when original pressure was higher than critical pressure.

  15. Streptococcus mutans forms xylitol-resistant biofilm on excess adhesive flash in novel ex-vivo orthodontic bracket model.

    Science.gov (United States)

    Ho, Cindy S F; Ming, Yue; Foong, Kelvin W C; Rosa, Vinicius; Thuyen, Truong; Seneviratne, Chaminda J

    2017-04-01

    During orthodontic bonding procedures, excess adhesive is invariably left on the tooth surface at the interface between the bracket and the enamel junction; it is called excess adhesive flash (EAF). We comparatively evaluated the biofilm formation of Streptococcus mutans on EAF produced by 2 adhesives and examined the therapeutic efficacy of xylitol on S mutans formed on EAF. First, we investigated the biofilm formation of S mutans on 3 orthodontic bracket types: stainless steel preadjusted edgewise, ceramic preadjusted edgewise, and stainless steel self-ligating. Subsequently, tooth-colored Transbond XT (3M Unitek, Monrovia, Calif) and green Grengloo (Ormco, Glendora, Calif) adhesives were used for bonding ceramic brackets to extracted teeth. S mutans biofilms on EAF produced by the adhesives were studied using the crystal violet assay and scanning electron microscopy. Surface roughness and surface energy of the EAF were examined. The therapeutic efficacies of different concentrations of xylitol were tested on S mutans biofilms. Significantly higher biofilms were formed on the ceramic preadjusted edgewise brackets (P = 0.003). Transbond XT had significantly higher S mutans biofilms compared with Grengloo surfaces (P = 0.007). There was no significant difference in surface roughness between Transbond XT and Grengloo surfaces (P >0.05). Surface energy of Transbond XT had a considerably smaller contact angle than did Grengloo, suggesting that Transbond XT is a more hydrophilic material. Xylitol at low concentrations had no significant effect on the reduction of S mutans biofilms on orthodontic adhesives (P = 0.016). Transbond XT orthodontic adhesive resulted in more S mutans biofilm compared with Grengloo adhesive on ceramic brackets. Surface energy seemed to play a more important role than surface roughness for the formation of S mutans biofilm on EAF. Xylitol does not appear to have a therapeutic effect on mature S mutans biofilm. Copyright © 2017 American

  16. Computer modelling of HT gas metabolism in humans

    International Nuclear Information System (INIS)

    Peterman, B.F.

    1982-01-01

    A mathematical model was developed to simulate the metabolism of HT gas in humans. The rate constants of the model were estimated by fitting the calculated curves to the experimental data by Pinson and Langham in 1957. The calculations suggest that the oxidation of HT gas (which probably occurs as a result of the enzymatic action of hydrogenase present in bacteria of human gut) occurs at a relatively low rate with a half-time of 10-12 hours. The inclusion of the dose due to the production of the HT oxidation product (HTO) in the soft tissues lowers the value of derived air concentration by about 50%. Furthermore the relationship between the concentration of HTO in urine and the dose to the lung from HT in the air in lungs is linear after short HT exposures, and hence HTO concentrations in urine can be used to estimate the upper limits on the lung dose from HT exposures. (author)

  17. Gas Storage Valuation and Hedging: A Quantification of Model Risk

    Directory of Open Access Journals (Sweden)

    Patrick Hénaff

    2018-03-01

    Full Text Available This paper focuses on the valuation and hedging of gas storage facilities, using a spot-based valuation framework coupled with a financial hedging strategy implemented with futures contracts. The contributions of this paper are two-fold. Firstly, we propose a model that unifies the dynamics of the futures curve and spot price, and accounts for the main stylized facts of the US natural gas market such as seasonality and the presence of price spikes in the spot market. Secondly, we evaluate the associated model risk, and show not only that the valuation is strongly dependent upon the dynamics of the spot price, but more importantly that the hedging strategy commonly used in the industry leaves the storage operator with significant residual price risk.

  18. The Virtual Diphoton Excess

    CERN Document Server

    Stolarski, Daniel

    2016-01-01

    Interpreting the excesses around 750 GeV in the diphoton spectra to be the signal of a new heavy scalar decaying to photons, we point out the possibility of looking for correlated signals with virtual photons. In particular, we emphasize that the effective operator that generates the diphoton decay will also generate decays to two leptons and a photon, as well as to four leptons, independently of the new resonance couplings to $Z\\gamma$ and $ZZ$. Depending on the relative sizes of these effective couplings, we show that the virtual diphoton component can make up a sizable, and sometimes dominant, contribution to the total $2\\ell \\gamma$ and $4\\ell$ partial widths. We also discuss modifications to current experimental cuts in order to maximize the sensitivity to these virtual photon effects. Finally, we briefly comment on prospects for channels involving other Standard Model fermions as well as more exotic decay possibilities of the putative resonance.

  19. Development of odorous gas model using municipal solid waste emission

    International Nuclear Information System (INIS)

    Mohd Nahar bin Othman; Muhd Noor Muhd Yunus; Ku Halim Ku Hamid

    2010-01-01

    The impact of ambient odour in the vicinity of the Semenyih MSW processing plant, commonly known as RDF plant, can be very negative to the nearby population, causing public restlessness and consequently affecting the business operation and sustainability of the plant. The precise source of the odour, types, emission level and the meteorological conditions are needed to predict and established the ambient odour level at the perimeter fence of the plant and address it with respect to the ambient standards. To develop the odour gas model for the purpose of treatment is very compulsory because in MSW odour it contain many component of chemical that contribute the smell. Upon modelling using an established package as well as site measurements, the odour level at the perimeter fence of the plant was deduced and found to be marginally high, above the normal ambient level. Based on this issue, a study was made to model odour using Ausplume Model. This paper will address and discuss the measurement of ambient gas odour, the dispersion modelling to establish the critical ambient emission level, as well as experimental validation using a simulated odour. The focus will be made on exploring the use of Ausplume modelling to develop the pattern of odour concentrations for various condition and times, as well as adapting the model for MSW odour controls. (author)

  20. Local lattice-gas model for immiscible fluids

    International Nuclear Information System (INIS)

    Chen, S.; Doolen, G.D.; Eggert, K.; Grunau, D.; Loh, E.Y.

    1991-01-01

    We present a lattice-gas model for two-dimensional immiscible fluid flows with surface tension that uses strictly local collision rules. Instead of using a local total color flux as Somers and Rem [Physica D 47, 39 (1991)], we use local colored holes to be the memory of particles of the same color. Interactions between walls and fluids are included that produce arbitrary contact angles

  1. Modeling of modification experiments involving neutral-gas release

    International Nuclear Information System (INIS)

    Bernhardt, P.A.

    1983-01-01

    Many experiments involve the injection of neutral gases into the upper atmosphere. Examples are critical velocity experiments, MHD wave generation, ionospheric hole production, plasma striation formation, and ion tracing. Many of these experiments are discussed in other sessions of the Active Experiments Conference. This paper limits its discussion to: (1) the modeling of the neutral gas dynamics after injection, (2) subsequent formation of ionosphere holes, and (3) use of such holes as experimental tools

  2. Heat conduction in caricature models of the Lorentz gas

    International Nuclear Information System (INIS)

    Kramli, A.; Simanyi, N.; Szasz, D.

    1987-01-01

    Heat transport coefficients are calculated for various random walks with internal states (the Markov partition of the Sinai billiard connects these walks with the Lorentz gas among a periodic configuration of scatterers). Models with reflecting or absorbing barriers and also those without or with local thermal equilibrium are investigated. The method is unified and is based on the Keldysh expansion of the resolvent of a matrix polynomial

  3. Planning the network of gas pipelines through modeling tools

    Energy Technology Data Exchange (ETDEWEB)

    Sucupira, Marcos L.L.; Lutif Filho, Raimundo B. [Companhia de Gas do Ceara (CEGAS), Fortaleza, CE (Brazil)

    2009-07-01

    Natural gas is a source of non-renewable energy used by different sectors of the economy of Ceara. Its use may be industrial, residential, commercial, as a source of automotive fuel, as a co-generation of energy and as a source for generating electricity from heat. For its practicality this energy has a strong market acceptance and provides a broad list of clients to fit their use, which makes it possible to reach diverse parts of the city. Its distribution requires a complex network of pipelines that branches throughout the city to meet all potential clients interested in this source of energy. To facilitate the design, analysis, expansion and location of bottlenecks and breaks in the distribution network, a modeling software is used that allows the network manager of the net to manage the various information about the network. This paper presents the advantages of modeling the gas distribution network of natural gas companies in Ceara, showing the tool used, the steps necessary for the implementation of the models, the advantages of using the software and the findings obtained with its use. (author)

  4. Excessive Daytime Sleepiness

    Directory of Open Access Journals (Sweden)

    Yavuz Selvi

    2016-06-01

    Full Text Available Excessive daytime sleepiness is one of the most common sleep-related patient symptoms, with preva-lence in the community estimated to be as high as 18%. Patients with excessive daytime sleepiness may exhibit life threatening road and work accidents, social maladjustment, decreased academic and occupational performance and have poorer health than comparable adults. Thus, excessive daytime sleepiness is a serious condition that requires investigation, diagnosis and treatment primarily. As with most medical condition, evaluation of excessive daytime sleepiness begins a precise history and various objective and subjective tools have been also developed to assess excessive daytime sleepiness. The most common causes of excessive daytime sleepiness are insufficient sleep hygiene, chronic sleep deprivation, medical and psychiatric conditions and sleep disorders, such as obstructive sleep apnea, medications, and narcolepsy. Treatment option should address underlying contributors and promote sleep quantity by ensuring good sleep hygiene. [Psikiyatride Guncel Yaklasimlar - Current Approaches in Psychiatry 2016; 8(2: 114-132

  5. Estimation of excess mortality due to long-term exposure to PM2.5 in Japan using a high-resolution model for present and future scenarios

    Science.gov (United States)

    Goto, Daisuke; Ueda, Kayo; Ng, Chris Fook Sheng; Takami, Akinori; Ariga, Toshinori; Matsuhashi, Keisuke; Nakajima, Teruyuki

    2016-09-01

    Particulate matter with a diameter of less than 2.5 μm, known as PM2.5, can affect human health, especially in elderly people. Because of the imminent aging of society in the near future in most developed countries, the human health impacts of PM2.5 must be evaluated. In this study, we used a global-to-regional atmospheric transport model to simulate PM2.5 in Japan with a high-resolution stretched grid system (∼10 km for the high-resolution model, HRM) for the present (the 2000) and the future (the 2030, as proposed by the Representative Concentrations Pathway 4.5, RCP4.5). We also used the same model with a low-resolution uniform grid system (∼100 km for the low-resolution model, LRM). These calculations were conducted by nudging meteorological fields obtained from an atmosphere-ocean coupled model and providing emission inventories used in the coupled model. After correcting for bias, we calculated the excess mortality due to long-term exposure to PM2.5 among the elderly (over 65 years old) based on different minimum PM2.5 concentration (MINPM) levels to account for uncertainty using the simulated PM2.5 distributions to express the health effect as a concentration-response function. As a result, we estimated the excess mortality for all of Japan to be 31,300 (95% confidence intervals: 20,700 to 42,600) people in 2000 and 28,600 (95% confidence intervals: 19,000 to 38,700) people in 2030 using the HRM with a MINPM of 5.8 μg/m3. In contrast, the LRM resulted in underestimates of approximately 30% (for PM2.5 concentrations in the 2000 and 2030), approximately 60% (excess mortality in the 2000) and approximately 90% (excess mortality in 2030) compared to the HRM results. We also found that the uncertainty in the MINPM value, especially for low PM2.5 concentrations in the future (2030) can cause large variability in the estimates, ranging from 0 (MINPM of 15 μg/m3 in both HRM and LRM) to 95,000 (MINPM of 0 μg/m3 in HRM) people.

  6. Lattice gas cellular automata and lattice Boltzmann models an introduction

    CERN Document Server

    Wolf-Gladrow, Dieter A

    2000-01-01

    Lattice-gas cellular automata (LGCA) and lattice Boltzmann models (LBM) are relatively new and promising methods for the numerical solution of nonlinear partial differential equations. The book provides an introduction for graduate students and researchers. Working knowledge of calculus is required and experience in PDEs and fluid dynamics is recommended. Some peculiarities of cellular automata are outlined in Chapter 2. The properties of various LGCA and special coding techniques are discussed in Chapter 3. Concepts from statistical mechanics (Chapter 4) provide the necessary theoretical background for LGCA and LBM. The properties of lattice Boltzmann models and a method for their construction are presented in Chapter 5.

  7. Study of deformation of droplet in external force field by using liquid-gas model of lattice-gas

    International Nuclear Information System (INIS)

    Ebihara, Ken-ichi; Watanabe, Tadashi

    2000-10-01

    The deformation of the droplet by the external force which is assumed to be gravity is studied by using the liquid-gas model of lattice-gas. Two types of liquid-gas models, one is the minimal model and the other is the maximal model, which are distinguished from each other by the added long-range interactions are used for the simulation of the droplet deformation. The difference of the droplet deformation between the maximal model and the minimal model was observed. While the droplet of the minimal model elongates in the direction of the external force, the droplet of the maximal model elongates in the perpendicular direction to the external force. Therefore the droplet deformation in the external force field of the maximal model is more similar to the droplet deformation which is observed in experiments than that of the minimal model. (author)

  8. Thermodynamic modeling of a gas micro turbine power system; Modelagem termodinamica de uma microturbina a gas

    Energy Technology Data Exchange (ETDEWEB)

    Venson, Giuliano Gardolinski [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Mecanica], e-mail: venson@ufmg.br; Barros, Jose Eduardo Mautone; Pereira, Josemar Figueiredo [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET-MG), Belo Horizonte, MG (Brazil)], e-mail: mautone@des.cefetmg.br, e-mail: josemar_cefet@yahoo.com.br

    2006-07-01

    This work presents the modeling of a gas microturbine power generator. The microturbine consists in a small thermo-electrical power unit, design for combined heat and power generation. The unit has an electric generator, coaxially connected with a turbocharger, which one is driven by a fuel burner. The system also incorporates an air regenerator, used for pre-heat the combustion air, and a heat exchanger, used for water heating. The objective of the modeling is the attainment of the electrical performance and the operational limits for the microturbine in function of the subsystems operational conditions. The modeling is based on the first law of the thermodynamic, using specific models for each component. In the combustion chamber is used a model that takes the fuel injection properties, as absolute pressure and temperature. A semi-empirical model, based in the modified Euler equation, is used in the turbocharger. In the air regenerator and heat exchanger, the method of mean logarithmic temperature difference is used. Through the modeling of a commercial microturbine, reference values obtained were used in some subsystems of a new microturbine. The results for this new microturbine in development, based in automotive turbochargers, indicate a nominal electrical power of 38 kW with electrical efficiency of 33% and global efficiency of 73%. (author)

  9. Optimal control in a micro gas grid of prosumers using Model Predictive Control

    NARCIS (Netherlands)

    Alkano, Desti; Nefkens, W.J.; Scherpen, Jacqueline M.A.; Volkerts, M.

    This paper studies the optimal control of a micro grid of biogas prosumers equipped with local storage devices. Excess biogas can be upgraded and injected into the low- pressure gas grid or, alternatively, shipped per lorry to be used elsewhere in an effort to create revenue. The aim of the control

  10. Modeling beam-front dynamics at low gas pressures

    International Nuclear Information System (INIS)

    Briggs, R.J.; Yu, S.

    1982-01-01

    The dynamics of space charge neutralization at the front of an intense self-focused electron beam pulse exhibits important differences in different gas pressure regimes. At very low pressures, the beam front is in the so-called ion-focused regime (IFR) where all secondary electrons are expelled from the beam region by the radial electric field without causing significant additional ionization. We estimate the upper pressure boundary of this regime by considering the distance scale length for cascade (avalanche) ionization. Data from the FX-25 diode experiments indicate a critical transition pressure (P/sub c/) that agrees with this estimate and with its scaling among various gas types. Normal mobility-limited treatments (local conductivity models) of the secondary electrons at the beam front are not justified until the gas pressure is 10 to 50 times higher than P/sub c/, due to runaway of these secondary electrons in the strong space-charge electric field at the lower pressures. The main conclusion of this study is that a non-local phase space (Boltzmann) treatment of the secondary electrons is required to accurately describe these different beam front regimes and the transitions between them; such a code model is currently under development

  11. Study and mathematical model of ultra-low gas burner

    International Nuclear Information System (INIS)

    Gueorguieva, A.

    2001-01-01

    The main objective of this project is prediction and reduction of NOx and CO 2 emissions under levels recommended from European standards for gas combustion processes. A mathematical model of burner and combustion chamber is developed based on interacting fluid dynamics processes: turbulent flow, gas phase chemical reactions, heat and radiation transfer The NOx prediction model for prompt and thermal NOx is developed. The validation of CFD (Computer fluid-dynamics) simulations corresponds to 5 MWI burner type - TEA, installed on CASPER boiler. This burner is three-stream air distribution burner with swirl effect, designed by ENEL to meet future NOx emission standards. For performing combustion computer modelling, FLUENT CFD code is preferred, because of its capabilities to provide accurately description of large number of rapid interacting processes: turbulent flow, phase chemical reactions and heat transfer and for its possibilities to present wide range of calculation and graphical output reporting data The computational tool used in this study is FLUENT version 5.4.1, installed on fs 8200 UNIX systems The work includes: study the effectiveness of low-NOx concepts and understand the impact of combustion and swirl air distribution and flue gas recirculation on peak flame temperatures, flame structure and fuel/air mixing. A finite rate combustion model: Eddy-Dissipation (Magnussen-Hjertager) Chemical Model for 1, 2 step Chemical reactions of bi-dimensional (2D) grid is developed along with NOx and CO 2 predictions. The experimental part of the project consists of participation at combustion tests on experimental facilities located in Livorno. The results of the experiments are used, to obtain better vision for combustion process on small-scaled design and to collect the necessary input data for further Fluent simulations

  12. Thermodynamic modelling of an onsite methanation reactor for upgrading producer gas from commercial small scale biomass gasifiers.

    Science.gov (United States)

    Vakalis, S; Malamis, D; Moustakas, K

    2018-06-15

    Small scale biomass gasifiers have the advantage of having higher electrical efficiency in comparison to other conventional small scale energy systems. Nonetheless, a major drawback of small scale biomass gasifiers is the relatively poor quality of the producer gas. In addition, several EU Member States are seeking ways to store the excess energy that is produced from renewables like wind power and hydropower. A recent development is the storage of energy by electrolysis of water and the production of hydrogen in a process that is commonly known as "power-to-gas". The present manuscript proposes an onsite secondary reactor for upgrading producer gas by mixing it with hydrogen in order to initiate methanation reactions. A thermodynamic model has been developed for assessing the potential of the proposed methanation process. The model utilized input parameters from a representative small scale biomass gasifier and molar ratios of hydrogen from 1:0 to 1:4.1. The Villar-Cruise-Smith algorithm was used for minimizing the Gibbs free energy. The model returned the molar fractions of the permanent gases, the heating values and the Wobbe Index. For mixtures of hydrogen and producer gas on a 1:0.9 ratio the increase of the heating value is maximized with an increase of 78%. For ratios higher than 1:3, the Wobbe index increases significantly and surpasses the value of 30 MJ/Nm 3 . Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Modeling of Hybrid Permanent Magnetic-Gas Bearings

    DEFF Research Database (Denmark)

    Morosi, Stefano; Santos, Ilmar

    2009-01-01

    Modern turbomachinery applications require nowadays ever-growing rotational speeds and high degree of reliability. It then becomes natural to focus the attention of the research to contact-free bearings elements. The present alternatives focus on gas lubricated journal bearings or magnetic bearings....... In the present paper, a detailed mathematical modeling of the gas bearing based on the compressible form of the Reynolds equation is presented. Perturbation theory is applied in order to identify the dynamic characteristic of the bearing. Due to the simple design of the magnetic bearings elements - being...... the rotor equilibrium position can be made independent on the rotational speed and applied load; it becomes function of the passive magnetic bearing offset. By adjusting the offset it is possible to significantly influence the dynamic coefficients of the hybrid bearing....

  14. Analytical modeling of wet compression of gas turbine systems

    International Nuclear Information System (INIS)

    Kim, Kyoung Hoon; Ko, Hyung-Jong; Perez-Blanco, Horacio

    2011-01-01

    Evaporative gas turbine cycles (EvGT) are of importance to the power generation industry because of the potential of enhanced cycle efficiencies with moderate incremental cost. Humidification of the working fluid to result in evaporative cooling during compression is a key operation in these cycles. Previous simulations of this operation were carried out via numerical integration. The present work is aimed at modeling the wet-compression process with approximate analytical solutions instead. A thermodynamic analysis of the simultaneous heat and mass transfer processes that occur during evaporation is presented. The transient behavior of important variables in wet compression such as droplet diameter, droplet mass, gas and droplet temperature, and evaporation rate is investigated. The effects of system parameters on variables such as droplet evaporation time, compressor outlet temperature and input work are also considered. Results from this work exhibit good agreement with those of previous numerical work.

  15. Gas

    International Nuclear Information System (INIS)

    1996-01-01

    The French government has decided to modify the conditions of extension of local natural gas authorities to neighbouring districts. The European Union is studying the conditions of internal gas market with the objective of more open markets although considering public service requirements

  16. Sorption Modeling and Verification for Off-Gas Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Tavlarides, Lawrence L. [Syracuse Univ., NY (United States); Lin, Ronghong [Syracuse Univ., NY (United States); Nan, Yue [Syracuse Univ., NY (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Georgia Inst. of Technology, Atlanta, GA (United States); Ladshaw, Austin [Georgia Inst. of Technology, Atlanta, GA (United States); Sharma, Ketki [Georgia Inst. of Technology, Atlanta, GA (United States); Gabitto, Jorge [Prairie View A & M Univ., Prairie View, TX (United States); DePaoli, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-04-29

    The project has made progress toward developing a comprehensive modeling capability for the capture of target species in off gas evolved during the reprocessing of nuclear fuel. The effort has integrated experimentation, model development, and computer code development for adsorption and absorption processes. For adsorption, a modeling library has been initiated to include (a) equilibrium models for uptake of off-gas components by adsorbents, (b) mass transfer models to describe mass transfer to a particle, diffusion through the pores of the particle and adsorption on the active sites of the particle, and (c) interconnection of these models to fixed bed adsorption modeling which includes advection through the bed. For single-component equilibria, a Generalized Statistical Thermodynamic Adsorption (GSTA) code was developed to represent experimental data from a broad range of isotherm types; this is equivalent to a Langmuir isotherm in the two-parameter case, and was demonstrated for Kr on INL-engineered sorbent HZ PAN, water sorption on molecular sieve A sorbent material (MS3A), and Kr and Xe capture on metal-organic framework (MOF) materials. The GSTA isotherm was extended to multicomponent systems through application of a modified spreading pressure surface activity model and generalized predictive adsorbed solution theory; the result is the capability to estimate multicomponent adsorption equilibria from single-component isotherms. This advance, which enhances the capability to simulate systems related to off-gas treatment, has been demonstrated for a range of real-gas systems in the literature and is ready for testing with data currently being collected for multicomponent systems of interest, including iodine and water on MS3A. A diffusion kinetic model for sorbent pellets involving pore and surface diffusion as well as external mass transfer has been established, and a methodology was developed for determining unknown diffusivity parameters from transient

  17. Sorption Modeling and Verification for Off-Gas Treatment

    International Nuclear Information System (INIS)

    Tavlarides, Lawrence L.; Lin, Ronghong; Nan, Yue; Yiacoumi, Sotira; Tsouris, Costas; Ladshaw, Austin; Sharma, Ketki; Gabitto, Jorge; DePaoli, David

    2015-01-01

    The project has made progress toward developing a comprehensive modeling capability for the capture of target species in off gas evolved during the reprocessing of nuclear fuel. The effort has integrated experimentation, model development, and computer code development for adsorption and absorption processes. For adsorption, a modeling library has been initiated to include (a) equilibrium models for uptake of off-gas components by adsorbents, (b) mass transfer models to describe mass transfer to a particle, diffusion through the pores of the particle and adsorption on the active sites of the particle, and (c) interconnection of these models to fixed bed adsorption modeling which includes advection through the bed. For single-component equilibria, a Generalized Statistical Thermodynamic Adsorption (GSTA) code was developed to represent experimental data from a broad range of isotherm types; this is equivalent to a Langmuir isotherm in the two-parameter case, and was demonstrated for Kr on INL-engineered sorbent HZ PAN, water sorption on molecular sieve A sorbent material (MS3A), and Kr and Xe capture on metal-organic framework (MOF) materials. The GSTA isotherm was extended to multicomponent systems through application of a modified spreading pressure surface activity model and generalized predictive adsorbed solution theory; the result is the capability to estimate multicomponent adsorption equilibria from single-component isotherms. This advance, which enhances the capability to simulate systems related to off-gas treatment, has been demonstrated for a range of real-gas systems in the literature and is ready for testing with data currently being collected for multicomponent systems of interest, including iodine and water on MS3A. A diffusion kinetic model for sorbent pellets involving pore and surface diffusion as well as external mass transfer has been established, and a methodology was developed for determining unknown diffusivity parameters from transient

  18. The Geopolitical Impact of Shale Gas : The Modelling Approach

    NARCIS (Netherlands)

    Auping, W.L.; De Jong, S.; Pruyt, E.; Kwakkel, J.H.

    2014-01-01

    The US’ shale gas revolution, a spectacular increase in natural gas extraction from previously unconventional sources, has led to considerable lower gas prices in North America. This study focusses on consequences of the shale gas revolution on state stability of traditional oil and gas exporting

  19. Galactic bulge preferred over dark matter for the Galactic centre gamma-ray excess

    Science.gov (United States)

    Macias, Oscar; Gordon, Chris; Crocker, Roland M.; Coleman, Brendan; Paterson, Dylan; Horiuchi, Shunsaku; Pohl, Martin

    2018-05-01

    An anomalous gamma-ray excess emission has been found in the Fermi Large Area Telescope data1 covering the centre of the Galaxy2,3. Several theories have been proposed for this `Galactic centre excess'. They include self-annihilation of dark-matter particles4, an unresolved population of millisecond pulsars5, an unresolved population of young pulsars6, or a series of burst events7. Here, we report on an analysis that exploits hydrodynamical modelling to register the position of interstellar gas associated with diffuse Galactic gamma-ray emission. We find evidence that the Galactic centre excess gamma rays are statistically better described by the stellar over-density in the Galactic bulge and the nuclear stellar bulge, rather than a spherical excess. Given its non-spherical nature, we argue that the Galactic centre excess is not a dark-matter phenomenon but rather associated with the stellar population of the Galactic bulge and the nuclear bulge.

  20. Mathematical Modeling of Metal Active Gas (MAG) Arc Welding

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In the present paper, a numerical model for MAG (metal active gas) arc welding of thin plate has been developed. In MAG arc welding, the electrode wire is melted and supplied into the molten pool intermittently. Accordingly, it is assumed on the modeling that the thermal energy enters the base-plates through two following mechanisms, i.e., direct heating from arc plasma and “indirect” heating from the deposited metal. In the second part of the paper, MAG arc welding process is numerically analyzed by using the model, and the calculated weld bead dimension and surface profile have been compared with the experimental MAG welds on steel plate. As the result, it is made clear that the model is capable of predicting the bead profile of thin-plate MAG arc welding , including weld bead with undercutting.

  1. A theoretical model for gas permeability in a composite membrane

    International Nuclear Information System (INIS)

    Serrano, D. A

    2009-01-01

    We present in this work an analytical expression for permeability in a two-layer composite membrane, which was derived assuming the same hypothesis as those of Adzumi model for permeability in a homogeneous membrane. Whereas in Adzumi model permeability shows a linear dependence on the mean pressure, our model for a composite membrane related permeability to pressure through a rather complex expression, which covers the whole range of flow, from molecular-Knudsen to viscous-Poiseuille regimes. The expression obtained for permeability contained information of membrane structural properties as pore size, porosity and thickness of each layer, as well as gas nature and operational conditions. Our two-layer-model expression turns into Adzumi formula when the structure of the layers approach to each other. [es

  2. Conformal field theories, Coulomb gas picture and integrable models

    International Nuclear Information System (INIS)

    Zuber, J.B.

    1988-01-01

    The aim of the study is to present the links between some results of conformal field theory, the conventional Coulomb gas picture in statistical mechanics and the approach of integrable models. It is shown that families of conformal theories, related by the coset construction to the SU(2) Kac-Moody algebra, may be regarded as obtained from some free field, and modified by the coupling of its winding numbers to floating charges. This representation reflects the procedure of restriction of the corresponding integrable lattice models. The work may be generalized to models based on the coset construction with higher rank algebras. The corresponding integrable models are identified. In the conformal field description, generalized parafermions appear, and are coupled to free fields living on a higher-dimensional torus. The analysis is not as exhaustive as in the SU(2) case: all the various restrictions have not been identified, nor the modular invariants completely classified

  3. A complementarity model for the European natural gas market

    International Nuclear Information System (INIS)

    Egging, Ruud; Gabriel, Steven A.; Holz, Franziska; Zhuang, Jifang

    2008-01-01

    In this paper, we present a detailed and comprehensive complementarity model for computing market equilibrium values in the European natural gas system. Market players include producers and their marketing arms which we call 'traders', pipeline and storage operators, marketers, LNG liquefiers, regasifiers, tankers, and three end-use consumption sectors. The economic behavior of producers, traders, pipeline and storage operators, liquefiers and regasifiers is modeled via optimization problems whose Karush-Kuhn-Tucker (KKT) optimality conditions in combination with market-clearing conditions form the complementarity system. The LNG tankers, marketers and consumption sectors are modeled implicitly via appropriate cost functions, aggregate demand curves, and ex post calculations, respectively. The model is run on several case studies that highlight its capabilities, including a simulation of a disruption of Russian supplies via Ukraine

  4. Gas-Grain Models for Interstellar Anion Chemistry

    Science.gov (United States)

    Cordiner, M. A.; Charnely, S. B.

    2012-01-01

    Long-chain hydrocarbon anions C(sub n) H(-) (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n(sub H2) approx > / cubic cm). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H(-) anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment

  5. Gas turbine cooling modeling - Thermodynamic analysis and cycle simulations

    Energy Technology Data Exchange (ETDEWEB)

    Jordal, Kristin

    1999-02-01

    Considering that blade and vane cooling are a vital point in the studies of modern gas turbines, there are many ways to include cooling in gas turbine models. Thermodynamic methods for doing this are reviewed in this report, and, based on some of these methods, a number of model requirements are set up and a Cooled Gas Turbine Model (CGTM) for design-point calculations of cooled gas turbines is established. Thereafter, it is shown that it is possible to simulate existing gas turbines with the CGTM. Knowledge of at least one temperature in the hot part of the turbine (TET, TRIT or possibly TIT) is found to be vital for a complete heat balance over the turbine. The losses, which are caused by the mixing of coolant and main flow, are in the CGTM considered through a polytropic efficiency reduction factor S. Through the study of S, it can be demonstrated that there is more to gain from coolant reduction in a small and/or old turbine with poor aerodynamics, than there is to gain in a large, modern turbine, where the losses due to interaction between coolant and main flow are, relatively speaking, small. It is demonstrated, at the design point (TET=1360 deg C, {pi}=20) for the simple-cycle gas turbine, that heat exchanging between coolant and fuel proves to have a large positive impact on cycle efficiency, with an increase of 0.9 percentage points if all of the coolant passes through the heat exchanger. The corresponding improvement for humidified coolant is 0.8 percentage points. A design-point study for the HAT cycle shows that if all of the coolant is extracted after the humidification tower, there is a decrease in coolant requirements of 7.16 percentage points, from 19.58% to 12.52% of the compressed air, and an increase in thermal efficiency of 0.46 percentage points, from 53.46% to 53.92%. Furthermore, it is demonstrated with a TET-parameter variation, that the cooling of a simple-cycle gas turbine with humid air can have a positive effect on thermal efficiency

  6. CFD model of a spinning pipe gas lens

    CSIR Research Space (South Africa)

    Snedden, Glen C

    2006-07-01

    Full Text Available Slides on: Spinning Pipe Gas Lens; Focal Length; Refractive Index; Gas Dynamics; Guess at the gas dynamics; Density Profile; Flow Profile; Rosby Waves; Rayleigh–Taylor Instabilities...

  7. A dynamic model of a 100 kW micro gas turbine fuelled with natural gas and hydrogen blends and its application in a hybrid energy grid

    International Nuclear Information System (INIS)

    Di Gaeta, Alessandro; Reale, Fabrizio; Chiariello, Fabio; Massoli, Patrizio

    2017-01-01

    The paper deals with the development of a dynamic model of a commercial 100 kW Micro Gas Turbine (MGT) fuelled with mixtures of standard (i.e. natural gas or methane) and alternative fuels (i.e. hydrogen). The model consists of a first-order differential equation (ODE) describing the dominant dynamics of the MGT imposed by its own control system during production electrical power. The differential equation is coupled to a set of nonlinear maps derived numerically from a detailed 0D thermodynamic matching model of the MGT evaluated over a wide range of operating conditions (i.e. mechanical power, fraction of hydrogen and ambient temperature). The efficiency of the electrical machine with power inverter and power absorbed by auxiliary devices is also taken into account. The resulting model is experimentally validated for a sequence of power step responses of the MGT at different ambient conditions and with different fuel mixtures. The model is suited for simulation and control of hybrid energy grids (HEGs) which rely on advanced use of MGT and hydrogen as energy carrier. In this regard, the MGT model is used in the simulation of an HEG based on an appropriate mix of renewable (non-programmable) and non-renewable (programmable) energy sources with hydrogen storage and its reuse in the MGT. Here, the MGT is used as a programmable energy vector for compensating the deficits of renewable energies (such as solar and wind) with respect to user demand, while excess renewable energy is used to produce hydrogen via electrolysis of water. The simulated HEG comprises a solar PhotoVoltaic (PV) plant (300 kW), an MGT (100 kW) fuelled with natural gas and hydrogen blends, a water electrolyzer (WE) system (8 bar, 56 Nm 3 /h), a hydrogen tank (54 m 3 ), and an Energy Management Control System (EMCS). - Highlights: • A dynamic model of a commercial 100 kW MGT fuelled with natural gas and hydrogen blends is developed. • The model reproduces the electrical power generated by

  8. A strategic model of European gas supply (GASMOD)

    International Nuclear Information System (INIS)

    Holz, Franziska; Hirschhausen, Christian von; Kemfert, Claudia

    2008-01-01

    This paper presents a model of the European natural gas supply, GASMOD, which is structured as a two-stage-game of successive natural gas exports to Europe (upstream market) and wholesale trade within Europe (downstream market) and which explicitly includes infrastructure capacities. We compare three possible market scenarios: Cournot competition in both markets, perfect competition in both markets, and perfect competition in the downstream with Cournot competition in the upstream market (EU liberalization). We find that Cournot competition in both markets is the most accurate representation of today's European natural gas market, where suppliers at both stages generate a mark-up at the expense of the final customer (double marginalization). Our results yield a diversified supply portfolio with newly emerging (LNG) exporters gaining market shares. Enforcing competition in the European downstream market would lead to lower prices and higher quantities by avoiding the welfare-reducing effects of double marginalization. Binding infrastructure capacity restrictions strongly influence the results, and we identify bottlenecks mainly for intra-European trade relations whereas transport capacity in the upstream market is globally sufficient in the Cournot scenario. (author)

  9. Semiparametric profile likelihood estimation for continuous outcomes with excess zeros in a random-threshold damage-resistance model.

    Science.gov (United States)

    Rice, John D; Tsodikov, Alex

    2017-05-30

    Continuous outcome data with a proportion of observations equal to zero (often referred to as semicontinuous data) arise frequently in biomedical studies. Typical approaches involve two-part models, with one part a logistic model for the probability of observing a zero and some parametric continuous distribution for modeling the positive part of the data. We propose a semiparametric model based on a biological system with competing damage manifestation and resistance processes. This allows us to derive a closed-form profile likelihood based on the retro-hazard function, leading to a flexible procedure for modeling continuous data with a point mass at zero. A simulation study is presented to examine the properties of the method in finite samples. We apply the method to a data set consisting of pulmonary capillary hemorrhage area in lab rats subjected to diagnostic ultrasound. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  10. Strategies simulation model for the gas business chain MEGAS

    International Nuclear Information System (INIS)

    Gonzalez, S.M. de; Uzcategui, R.; Brea, E.; Diaz, R.

    1994-01-01

    MEGAS is a simulation model representing fundamental parameters of Corpoven's natural gas and NGL production, handling, processing, transportation and distribution systems in the Venezuelan mid-east, as well as its financial implications. Various strategies regarding development, prices, costs, new business opportunities, production scenarios, demand and energy policies can be evaluated through this model in order to determine, after analyzing the economics results, a set of strategies to follow in the mid and long term. MEGAS could be also used to make risk analysis studies, considering that probabilistic parameters and variables like gas quality, production, demand, plant shutdowns and others are to be represented by their distinctive function. It is possible to set up a probabilistic function for each economic indicator or operating variables with an appropriate experiment design. MEGAS is based on a dynamic simulation language, which facilitates both the real system components representation and the main variables statistical data accumulation. It also allows graphical representation of results and the simulation animation. Demand and price forecasts, new projects, costs and capabilities of the systems are some of the model input data. MEGAS should be considered as a tool that eases the strategic planning of the business, making it possible for the Corporation to foresee changes, both in the domestic and international market, to predict how these changes could affect its business affairs and to visualize different return scenarios

  11. Computer modeling of a small neon gas-puff pinch

    International Nuclear Information System (INIS)

    Ullschmied, J.

    1996-01-01

    The macroscopic dynamics of a cylindrical gas-puff pinch and conditions of radiation plasma collapse are studied by using a one-dimensional ('mechanical') computer model. Besides the Joule plasma heating, compressional heating, magnetic field freezing in a plasma and recombination losses, also the real temperature- and density-dependences of radiation plasma loss are taken into account. The results of calculations are compared with experimental data taken from a small neon-puff z-pinch experiment operated at the Institute of Plasma Physics in Prague. (author). 7 figs., 11 refs

  12. On The Modelling Of Hybrid Aerostatic - Gas Journal Bearings

    DEFF Research Database (Denmark)

    Morosi, Stefano; Santos, Ilmar

    2011-01-01

    modeling for hybrid lubrication of a compressible fluid film journal bearing. Additional forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving......Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...

  13. Development of a short-term model to predict natural gas demand, March 1989

    International Nuclear Information System (INIS)

    Lihn, M.L.

    1989-03-01

    Project management decisions for the Gas Research Institute (GRI) R and D program require an appreciation of the short-term outlook for gas consumption. This paper provides a detailed discussion of the methodology used to develop short-term models for the residential, commercial, industrial, and electric utility sectors. The relative success of the models in projecting gas demand, compared with actual gas demand, is reviewed for each major gas-consuming sector. The comparison of actual to projected gas demand has pointed out several problems with the model, and possible solutions to these problems are discussed

  14. Gas Hydrate Petroleum System Modeling in western Nankai Trough Area

    Science.gov (United States)

    Tanaka, M.; Aung, T. T.; Fujii, T.; Wada, N.; Komatsu, Y.

    2017-12-01

    Since 2003, we have been conducting Gas Hydrate (GH) petroleum system models covering the eastern Nankai Trough, Japan, and results of resource potential from regional model shows good match with the value depicted from seismic and log data. In this year, we have applied this method to explore GH potential in study area. In our study area, GH prospects have been identified with aid of bottom simulating reflector (BSR) and presence of high velocity anomalies above the BSR interpreted based on 3D migration seismic and high density velocity cubes. In order to understand the pathway of biogenic methane from source to GH prospects 1D-2D-3D GH petroleum system models are built and investigated. This study comprises lower Miocene to Pleistocene, deep to shallow marine sedimentary successions of Pliocene and Pleistocene layers overlain the basement. The BSR were interpreted in Pliocene and Pleistocene layers. Based on 6 interpreted sequence boundaries from 3D migration seismic and velocity data, construction of a depth 3D framework model is made and distributed by a conceptual submarine fan depositional facies model derived from seismic facies analysis and referring existing geological report. 1D models are created to analyze lithology sensitivity to temperature and vitrinite data from an exploratory well drilled in the vicinity of study area. The PSM parameters are applied in 2D and 3D modeling and simulation. Existing report of the explanatory well reveals that thermogenic origin are considered to exist. For this reason, simulation scenarios including source formations for both biogenic and thermogenic reaction models are also investigated. Simulation results reveal lower boundary of GH saturation zone at pseudo wells has been simulated with sensitivity of a few tens of meters in comparing with interpreted BSR. From sensitivity analysis, simulated temperature was controlled by different peak generation temperature models and geochemical parameters. Progressive folding

  15. Application of some geometrical and empirical models to excess molar volume for the multi-component mixtures at T = 298.15 K

    International Nuclear Information System (INIS)

    Iloukhani, H.; Khanlarzadeh, K.

    2012-01-01

    Highlights: ► Excess molar volume of quartenary mixtures of 1-chlorobutane, 2-chlorobutane, butylamine, and butylacetate was determined. ► The experimental data were correlated by some empirical and semi empirical models. ► A comparison with PFP theory has been successfully applied from binary data. - Abstract: Densities of the quaternary mixture consisting of {1-chlorobutane (1) + 2-chlorobutane (2) + butylamine (3) + butylacetate (4)} and related ternary mixtures of {1-chlorobutane (1) + 2-chlorobutane (2) + butylamine (3)}, {1-chlorobutane (1) + 2-chlorobutane (2) + butylacetate (4)}, {2-chlorobutane (2) + butylamine (3) + butylacetate (4)}, and binary systems of {1-chlorobutane (1) + 2-chlorobutane (2)}, {2-chlorobutane (2) + butylamine (3)}, were measured over the whole range of composition at T = 298.15 K and ambient pressure. Excess molar volumes, V m E , for the mixtures were derived and correlated as a function of mole fraction by using the Redlich–Kister and the Cibulka equations for binary and ternary mixtures, respectively. From the experimental data, partial molar volumes, V m,i and excess partial molar volumes, V m,i E were also calculated for binary systems. The experimental results of the constituted binary mixtures have been used to test the applicability of the Prigogine–Flory–Paterson (PFP) theory. A number of geometrical and empirical equations were also used to verify their ability to predict ternary and quaternary properties from their lower order mixtures. The experimental data were used to evaluate the nature and type of intermolecular interactions in multi-component mixtures.

  16. Modeling the transient security constraints of natural gas network in day-ahead power system scheduling

    DEFF Research Database (Denmark)

    Yang, Jingwei; Zhang, Ning; Kang, Chongqing

    2017-01-01

    The rapid deployment of gas-fired generating units makes the power system more vulnerable to failures in the natural gas system. To reduce the risk of gas system failure and to guarantee the security of power system operation, it is necessary to take the security constraints of natural gas...... accurately, they are hard to be embedded into the power system scheduling model, which consists of algebraic equations and inequations. This paper addresses this dilemma by proposing an algebraic transient model of natural gas network which is similar to the branch-node model of power network. Based...... pipelines into account in the day-ahead power generation scheduling model. However, the minute- and hour-level dynamic characteristics of gas systems prevents an accurate decision-making simply with the steady-state gas flow model. Although the partial differential equations depict the dynamics of gas flow...

  17. Operational modeling of a sustainable gas supply chain

    NARCIS (Netherlands)

    Bekkering, Jan; Broekhuis, A. A.; van Gemert, Wim

    2010-01-01

    Biogas production from codigestion of cattle manure and biomass can have a significant contribution to a sustainable gas supply when this gas is upgraded to specifications prescribed for injection into the national gas grid and injected into this grid. In this study, we analyzed such a gas supply

  18. Modeling of noble gas injection into tokamak plasmas

    International Nuclear Information System (INIS)

    Morozov, D.Kh.; Yurchenko, E.I.; Lukash, V.E.; Baronova, E.O.; Rozhansky, V.A.; Senichenkov, I.Yu.; Veselova, I.Yu.; Schneider, R.

    2005-01-01

    Noble gas injection for mitigation of the disruption in DIII-D is simulated. The simulation of the first two stages is performed: of the neutral gas jet penetration through the background plasmas, and of the thermal quench. In order to simulate the first stage the 1.5-dimensional numerical code LLP with improved radiation model for noble gas is used. It is demonstrated that the jet remains mainly neutral and thus is able to penetrate to the central region of the tokamak in accordance with experimental observations. Plasma cooling at this stage is provided by the energy exchange with the jet. The radiation is relatively small, and the plasma thermal energy is spent mainly on the jet expansion. The magnetic surfaces in contact with the jet are cooled significantly. The cooling front propagates towards the plasma center. The simulations of the plasma column dynamics in the presence of moving jet is performed by means of the free boundary transport modeling DINA code. It has been shown that the cooling front is accompanied by strongly localized 'shark fin-like' perturbation in toroidal current density profile. After few milliseconds the jet (together with the current perturbation) achieves the region where safety factor is slightly higher than unity and a new type of the non-local kink mode develops. The unstable kink perturbation is non-resonant for any magnetic surface, both inside the plasma column, and in the vacuum space. The mode disturbs mainly the core region. The growth time of the 'shark fin-like' mode is higher than the Alfven time by a factor of 100 for DIII-D parameters. Hence, the simulation describes the DIII-D experimental results, at least, qualitatively. (author)

  19. Excessive cytosolic DNA fragments as a potential trigger of Graves’ disease: an encrypted message sent by animal models

    Directory of Open Access Journals (Sweden)

    Yuqian Luo

    2016-11-01

    Full Text Available Graves’ hyperthyroidism is caused by autoantibodies directed against the thyroid stimulating hormone receptor (TSHR that mimic the action of TSH. The establishment of Graves’ hyperthyroidism in experimental animals has proven to be an important approach to dissect the mechanisms of self-tolerance breakdown that lead to the production of thyroid-stimulating TSHR autoantibodies (TSAbs. ‘Shimojo’s model was the first successful Graves’ animal model, wherein immunization with fibroblasts cells expressing TSHR and a major histocompatibility complex (MHC class II molecule, but not either alone, induced TSAb production in AKR/N (H-2k mice. This model highlights the importance of coincident MHC class II expression on TSHR-expressing cells in the development of Graves’ hyperthyroidism. These data are also in agreement with the observation that Graves’ thyrocytes often aberrantly express MHC class II antigens via mechanisms that remain unclear. Our group demonstrated that cytosolic self-genomic DNA fragments derived from sterile injured cells can induce aberrant MHC class II expression and production of multiple inflammatory cytokines and chemokines in thyrocytes in vitro, suggesting that severe cell injury may initiate immune responses in a way that is relevant to thyroid autoimmunity mediated by cytosolic DNA signaling. Furthermore, more recent successful Graves’ animal models were primarily established by immunizing mice with TSHR-expressing plasmids or adenovirus. In these models, double-stranded DNA vaccine contents presumably exert similar immune-activating effect in cells at inoculation sites and thus might pave the way toward successful Graves’ animal models. This review focuses on evidence suggesting that cell injury-derived self-DNA fragments could act as Graves’ disease triggers.

  20. Bidirectional enantioselective effects of the GABAB receptor agonist baclofen in two mouse models of excessive ethanol consumption.

    Science.gov (United States)

    Kasten, Chelsea R; Blasingame, Shelby N; Boehm, Stephen L

    2015-02-01

    The GABAB receptor agonist baclofen has been studied extensively in preclinical models of alcohol-use disorders, yet results on its efficacy have been uncertain. Racemic baclofen, which is used clinically, can be broken down into separate enantiomers of the drug. Baclofen has been shown to produce enantioselective effects in behavioral assays, including those modeling reflexive and sexual behavior. The current studies sought to characterize the enantioselective effects of baclofen in two separate models of ethanol consumption. The first was a Drinking-in-the-Dark procedure that provides "binge-like" ethanol access to mice by restricting access to a 2-h period, 3 h into the dark cycle. The second was a two-bottle choice procedure that utilized selectively bred High Alcohol Preferring 1 (HAP1) mice to model chronic ethanol access. HAP1 mice are selectively bred to consume pharmacologically relevant amounts of ethanol in a 24-h two-bottle choice paradigm. The results showed that baclofen yields enantioselective effects on ethanol intake in both models, and that these effects are bidirectional. Total ethanol intake was decreased by R(+)-baclofen, while total intake was increased by S(-)-baclofen in the binge-like and chronic drinking models. Whereas overall binge-like saccharin intake was significantly reduced by R(+)-baclofen, chronic intake was not significantly altered. S(-)-baclofen did not significantly alter saccharin intake. Neither enantiomer significantly affected locomotion during binge-like reinforcer consumption. Collectively, these results demonstrate that baclofen produces enantioselective effects on ethanol consumption. More importantly, the modulation of consumption is bidirectional. The opposing enantioselective effects may explain some of the variance seen in published baclofen literature. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Advanced modeling of oxy-fuel combustion of natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Chungen Yin

    2011-01-15

    The main goal of this small-scale project is to investigate oxy-combustion of natural gas (NG) through advanced modeling, in which radiation, chemistry and mixing will be reasonably resolved. 1) A state-of-the-art review was given regarding the latest R and D achievements and status of oxy-fuel technology. The modeling and simulation status and achievements in the field of oxy-fuel combustion were also summarized; 2) A computer code in standard c++, using the exponential wide band model (EWBM) to evaluate the emissivity and absorptivity of any gas mixture at any condition, was developed and validated in detail against data in literature. A new, complete, and accurate WSGGM, applicable to both air-fuel and oxy-fuel combustion modeling and applicable to both gray and non-gray calculation, was successfully derived, by using the validated EWBM code as the reference mode. The new WSGGM was implemented in CFD modeling of two different oxy-fuel furnaces, through which its great, unique advantages over the currently most widely used WSGGM were demonstrated. 3) Chemical equilibrium calculations were performed for oxy-NG flame and air-NG flame, in which dissociation effects were considered to different degrees. Remarkable differences in oxy-fuel and air-fuel combustion were revealed, and main intermediate species that play key roles in oxy-fuel flames were identified. Different combustion mechanisms are compared, e.g., the most widely used 2-step global mechanism, refined 4-step global mechanism, a global mechanism developed for oxy-fuel using detailed chemical kinetic modeling (CHEMKIN) as reference. 4) Over 15 CFD simulations were done for oxy-NG combustion, in which radiation, chemistry, mixing, turbulence-chemistry interactions, and so on were thoroughly investigated. Among all the simulations, RANS combined with 2-step and refined 4-step mechanism, RANS combined with CHEMKIN-based new global mechanism for oxy-fuel modeling, and LES combined with different combustion

  2. Hyperhidrosis (Excessive Sweating)

    Science.gov (United States)

    ... who have this type are otherwise healthy. In medical terminology, the word “primary” means that the cause is not another medical condition. Secondary hyperhidrosis In medical terminology, “secondary” means that the excessive sweating (hyperhidrosis) has ...

  3. Verification of Thermal Models of Internally Cooled Gas Turbine Blades

    Directory of Open Access Journals (Sweden)

    Igor Shevchenko

    2018-01-01

    Full Text Available Numerical simulation of temperature field of cooled turbine blades is a required element of gas turbine engine design process. The verification is usually performed on the basis of results of test of full-size blade prototype on a gas-dynamic test bench. A method of calorimetric measurement in a molten metal thermostat for verification of a thermal model of cooled blade is proposed in this paper. The method allows obtaining local values of heat flux in each point of blade surface within a single experiment. The error of determination of local heat transfer coefficients using this method does not exceed 8% for blades with radial channels. An important feature of the method is that the heat load remains unchanged during the experiment and the blade outer surface temperature equals zinc melting point. The verification of thermal-hydraulic model of high-pressure turbine blade with cooling allowing asymmetrical heat removal from pressure and suction sides was carried out using the developed method. An analysis of heat transfer coefficients confirmed the high level of heat transfer in the leading edge, whose value is comparable with jet impingement heat transfer. The maximum of the heat transfer coefficients is shifted from the critical point of the leading edge to the pressure side.

  4. Metabolic modeling of synthesis gas fermentation in bubble column reactors.

    Science.gov (United States)

    Chen, Jin; Gomez, Jose A; Höffner, Kai; Barton, Paul I; Henson, Michael A

    2015-01-01

    A promising route to renewable liquid fuels and chemicals is the fermentation of synthesis gas (syngas) streams to synthesize desired products such as ethanol and 2,3-butanediol. While commercial development of syngas fermentation technology is underway, an unmet need is the development of integrated metabolic and transport models for industrially relevant syngas bubble column reactors. We developed and evaluated a spatiotemporal metabolic model for bubble column reactors with the syngas fermenting bacterium Clostridium ljungdahlii as the microbial catalyst. Our modeling approach involved combining a genome-scale reconstruction of C. ljungdahlii metabolism with multiphase transport equations that govern convective and dispersive processes within the spatially varying column. The reactor model was spatially discretized to yield a large set of ordinary differential equations (ODEs) in time with embedded linear programs (LPs) and solved using the MATLAB based code DFBAlab. Simulations were performed to analyze the effects of important process and cellular parameters on key measures of reactor performance including ethanol titer, ethanol-to-acetate ratio, and CO and H2 conversions. Our computational study demonstrated that mathematical modeling provides a complementary tool to experimentation for understanding, predicting, and optimizing syngas fermentation reactors. These model predictions could guide future cellular and process engineering efforts aimed at alleviating bottlenecks to biochemical production in syngas bubble column reactors.

  5. A complementarity model for solving stochastic natural gas market equilibria

    International Nuclear Information System (INIS)

    Zhuang Jifang; Gabriel, Steven A.

    2008-01-01

    This paper presents a stochastic equilibrium model for deregulated natural gas markets. Each market participant (pipeline operators, producers, etc.) solves a stochastic optimization problem whose optimality conditions, when combined with market-clearing conditions give rise to a certain mixed complementarity problem (MiCP). The stochastic aspects are depicted by a recourse problem for each player in which the first-stage decisions relate to long-term contracts and the second-stage decisions relate to spot market activities for three seasons. Besides showing that such a market model is an instance of a MiCP, we provide theoretical results concerning long-term and spot market prices and solve the resulting MiCP for a small yet representative market. We also note an interesting observation for the value of the stochastic solution for non-optimization problems

  6. A complementarity model for solving stochastic natural gas market equilibria

    International Nuclear Information System (INIS)

    Jifang Zhuang; Gabriel, S.A.

    2008-01-01

    This paper presents a stochastic equilibrium model for deregulated natural gas markets. Each market participant (pipeline operators, producers, etc.) solves a stochastic optimization problem whose optimality conditions, when combined with market-clearing conditions give rise to a certain mixed complementarity problem (MiCP). The stochastic aspects are depicted by a recourse problem for each player in which the first-stage decisions relate to long-term contracts and the second-stage decisions relate to spot market activities for three seasons. Besides showing that such a market model is an instance of a MiCP, we provide theoretical results concerning long-term and spot market prices and solve the resulting MiCP for a small yet representative market. We also note an interesting observation for the value of the stochastic solution for non-optimization problems. (author)

  7. Conserved number fluctuations in a hadron resonance gas model

    International Nuclear Information System (INIS)

    Garg, P.; Mishra, D.K.; Netrakanti, P.K.; Mohanty, B.; Mohanty, A.K.; Singh, B.K.; Xu, N.

    2013-01-01

    Net-baryon, net-charge and net-strangeness number fluctuations in high energy heavy-ion collisions are discussed within the framework of a hadron resonance gas (HRG) model. Ratios of the conserved number susceptibilities calculated in HRG are being compared to the corresponding experimental measurements to extract information about the freeze-out condition and the phase structure of systems with strong interactions. We emphasize the importance of considering the actual experimental acceptances in terms of kinematics (pseudorapidity (η) and transverse momentum (p T )), the detected charge state, effect of collective motion of particles in the system and the resonance decay contributions before comparisons are made to the theoretical calculations. In this work, based on HRG model, we report that the net-baryon number fluctuations are least affected by experimental acceptances compared to the net-charge and net-strangeness number fluctuations

  8. Modeling of flowing gas diode pumped alkali lasers: dependence of the operation on the gas velocity and on the nature of the buffer gas.

    Science.gov (United States)

    Barmashenko, B D; Rosenwaks, S

    2012-09-01

    A simple, semi-analytical model of flowing gas diode pumped alkali lasers (DPALs) is presented. The model takes into account the rise of temperature in the lasing medium with increasing pump power, resulting in decreasing pump absorption and slope efficiency. The model predicts the dependence of power on the flow velocity in flowing gas DPALs and checks the effect of using a buffer gas with high molar heat capacity and large relaxation rate constant between the 2P3/2 and 2P1/2 fine-structure levels of the alkali atom. It is found that the power strongly increases with flow velocity and that by replacing, e.g., ethane by propane as a buffer gas the power may be further increased by up to 30%. Eight kilowatt is achievable for 20 kW pump at flow velocity of 20  m/s.

  9. An electricity price model with consideration to load and gas price effects.

    Science.gov (United States)

    Huang, Min-xiang; Tao, Xiao-hu; Han, Zhen-xiang

    2003-01-01

    Some characteristics of the electricity load and prices are studied, and the relationship between electricity prices and gas (fuel) prices is analyzed in this paper. Because electricity prices are strongly dependent on load and gas prices, the authors constructed a model for electricity prices based on the effects of these two factors; and used the Geometric Mean Reversion Brownian Motion (GMRBM) model to describe the electricity load process, and a Geometric Brownian Motion(GBM) model to describe the gas prices; deduced the price stochastic process model based on the above load model and gas price model. This paper also presents methods for parameters estimation, and proposes some methods to solve the model.

  10. Excess cash holdings and shareholder value

    OpenAIRE

    Lee, Edward; Powell, Ronan

    2011-01-01

    We examine the determinants of corporate cash holdings in Australia and the impact on shareholder wealth of holding excess cash. Our results show that a trade-off model best explains the level of a firm’s cash holdings in Australia. We find that 'transitory' excess cash firms earn significantly higher risk-adjusted returns compared to 'persistent' excess cash firms, suggesting that the market penalises firms that hoard cash. The marginal value of cash also declines with larger cash balances, ...

  11. Program for aerodynamic performance tests of helium gas compressor model of the gas turbine high temperature reactor (GTHTR300)

    International Nuclear Information System (INIS)

    Takada, Shoji; Takizuka, Takakazu; Kunimoto, Kazuhiko; Yan, Xing; Itaka, Hidehiko; Mori, Eiji

    2003-01-01

    Research and development program for helium gas compressor aerodynamics was planned for the power conversion system of the Gas Turbine High Temperature Reactor (GTHTR300). The axial compressor with polytropic efficiency of 90% and surge margin more than 30% was designed with 3-dimensional aerodynamic design. Performance and surge margin of the helium gas compressor tends to be lower due to the higher boss ratio which makes the tip clearance wide relative to the blade height, as well as due to a larger number of stages. The compressor was designed on the basis of methods and data for the aerodynamic design of industrial open-cycle gas-turbine. To validate the design of the helium gas compressor of the GTHTR300, aerodynamic performance tests were planned, and a 1/3-scale, 4-stage compressor model was designed. In the tests, the performance data of the helium gas compressor model will be acquired by using helium gas as a working fluid. The maximum design pressure at the model inlet is 0.88 MPa, which allows the Reynolds number to be sufficiently high. The present study is entrusted from the Ministry of Education, Culture, Sports, Science and Technology of Japan. (author)

  12. A model of gas generation and transport within TRU [transuranic] waste drums

    International Nuclear Information System (INIS)

    Smith, F.G. III.

    1987-01-01

    Gas generation from the radiolytic decomposition of organic material contaminated with plutonium is modeled. Concentrations of gas throughout the waste drum are determined using a diffusional transport model. The model accurately reproduces experimentally measured gas concentrations. With polyethylene waste in unvented drums, the model predicts that hydrogen gas can accumulate to concentrations greater than 4 mole percent (lower flammable limit) with about 5 Ci of plutonium. Polyethylene provides a worst case for combustible waste material. If the drum liner is punctured and a carbon composite filter vent is installed in the drum lid, the plutonium loading can be increased to 240 Ci without generating flammable gas mixtures. 5 refs., 7 figs., 4 tabs

  13. Gas-evolution oscillators. 10. A model based on a delay equation

    Energy Technology Data Exchange (ETDEWEB)

    Bar-Eli, K.; Noyes, R.M. [Univ. of Oregon, Eugene, OR (United States)

    1992-09-17

    This paper develops a simplified method to model the behavior of a gas-evolution oscillator with two differential delay equations in two unknowns consisting of the population of dissolved molecules in solution and the pressure of the gas.

  14. Gas-evolution oscillators. 10. A model based on a delay equation

    International Nuclear Information System (INIS)

    Bar-Eli, K.; Noyes, R.M.

    1992-01-01

    This paper develops a simplified method to model the behavior of a gas-evolution oscillator with two differential delay equations in two unknowns consisting of the population of dissolved molecules in solution and the pressure of the gas

  15. Economic analysis of using excess renewable electricity to displace heating fuels

    DEFF Research Database (Denmark)

    Pensini, Alessandro; Rasmussen, Claus Nygaard; Kempton, Willett

    2014-01-01

    . Because excess electricity appears to be cost-optimum, this raises the question as to whether the excess electricity, which in the case of wind power is predominately produced in colder weather, might displace other fuels for purposes such as heat. This study models using excess electricity for heating......, based on an analysis of electricity and heat use in a TSO in the North-Eastern part of the United States (PJM Interconnection). The heating system was modeled as heat pump based district heating (HPDH) with thermal energy storage (TES). Thus, excess electricity is transformed into heat, which is easy....... An algorithm that calculates the total cost of a unit of heat was used to determine the economically optimal size of the system’s main components and the influence that natural gas (NG) and electricity prices have on this optimum. It was found that a system based on heat pumps (HP) and centralized thermal...

  16. Natural gas transmission and distribution model of the National Energy Modeling System

    International Nuclear Information System (INIS)

    1997-02-01

    The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of Integrated Analysis and Forecasting of the Energy Information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. From 1982 through 1993, the Intermediate Future Forecasting System (IFFS) was used by the EIA for its analyses, and the Gas Analysis Modeling System (GAMS) was used within IFFS to represent natural gas markets. Prior to 1982, the Midterm Energy Forecasting System (MEFS), also referred to as the Project Independence Evaluation System (PIES), was employed. NEMS was developed to enhance and update EIA's modeling capability by internally incorporating models of energy markets that had previously been analyzed off-line. In addition, greater structural detail in NEMS permits the analysis of a broader range of energy issues. The time horizon of NEMS is the midterm period (i.e., through 2015). In order to represent the regional differences in energy markets, the component models of NEMS function at regional levels appropriate for the markets represented, with subsequent aggregation/disaggregation to the Census Division level for reporting purposes

  17. Natural gas transmission and distribution model of the National Energy Modeling System

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-02-01

    The Natural Gas Transmission and Distribution Model (NGTDM) is the component of the National Energy Modeling System (NEMS) that is used to represent the domestic natural gas transmission and distribution system. NEMS was developed in the Office of Integrated Analysis and Forecasting of the Energy Information Administration (EIA). NEMS is the third in a series of computer-based, midterm energy modeling systems used since 1974 by the EIA and its predecessor, the Federal Energy Administration, to analyze domestic energy-economy markets and develop projections. From 1982 through 1993, the Intermediate Future Forecasting System (IFFS) was used by the EIA for its analyses, and the Gas Analysis Modeling System (GAMS) was used within IFFS to represent natural gas markets. Prior to 1982, the Midterm Energy Forecasting System (MEFS), also referred to as the Project Independence Evaluation System (PIES), was employed. NEMS was developed to enhance and update EIA`s modeling capability by internally incorporating models of energy markets that had previously been analyzed off-line. In addition, greater structural detail in NEMS permits the analysis of a broader range of energy issues. The time horizon of NEMS is the midterm period (i.e., through 2015). In order to represent the regional differences in energy markets, the component models of NEMS function at regional levels appropriate for the markets represented, with subsequent aggregation/disaggregation to the Census Division level for reporting purposes.

  18. REVIEW ARTICLE: MODELLING AND ANALYSIS OF A GASOLINE ENGINE EXHAUST GAS SYSTEMS

    OpenAIRE

    Barhm Mohamad

    2018-01-01

    The engine exhaust gas behaviour is strongly influencing the engine performance. This paper presents the modelling and analysis of four stroke - gasoline engine exhaust gas systems. An automotive example is considered whereby the pulsating exhausts gas flow through an exhaust pipe and silencer are considered over a wide range of speeds. Analytical procedures are outlined enabling the general analysis and modelling of vehicle engine exhaust gas systems also in this paper present...

  19. Cellular Stress, Excessive Apoptosis, and the Effect of Metformin in a Mouse Model of Type 2 Diabetic Embryopathy

    Science.gov (United States)

    Wu, Yanqing; Wang, Fang; Fu, Mao; Wang, Cheng; Quon, Michael J.

    2015-01-01

    Increasing prevalence of type 2 diabetes in women of childbearing age has led to a higher incidence of diabetes-associated birth defects. We established a model of type 2 diabetic embryopathy by feeding 4-week-old female mice a high-fat diet (HFD) (60% fat). After 15 weeks on HFD, the mice showed characteristics of type 2 diabetes mellitus (DM) and were mated with lean male mice. During pregnancy, control dams fed a normal diet (10% fat) were maintained on either normal diet or HFD, serving as a control group with elevated circulating free fatty acids. DM dams produced offspring at a rate of 11.3% for neural tube defect (NTD) formation, whereas no embryos in the control groups developed NTDs. Elevated markers of oxidative stress, endoplasmic reticulum stress, caspase activation, and neuroepithelial cell apoptosis (causal events in type 1 diabetic embryopathy) were observed in embryos of DM dams. DM dams treated with 200 mg/kg metformin in drinking water ameliorated fasting hyperglycemia, glucose intolerance, and insulin resistance with consequent reduction of cellular stress, apoptosis, and NTDs in their embryos. We conclude that cellular stress and apoptosis occur and that metformin effectively reduces type 2 diabetic embryopathy in a useful rodent model. PMID:25720389

  20. A paradigm for modeling and computation of gas dynamics

    Science.gov (United States)

    Xu, Kun; Liu, Chang

    2017-02-01

    In the continuum flow regime, the Navier-Stokes (NS) equations are usually used for the description of gas dynamics. On the other hand, the Boltzmann equation is applied for the rarefied flow. These two equations are based on distinguishable modeling scales for flow physics. Fortunately, due to the scale separation, i.e., the hydrodynamic and kinetic ones, both the Navier-Stokes equations and the Boltzmann equation are applicable in their respective domains. However, in real science and engineering applications, they may not have such a distinctive scale separation. For example, around a hypersonic flying vehicle, the flow physics at different regions may correspond to different regimes, where the local Knudsen number can be changed significantly in several orders of magnitude. With a variation of flow physics, theoretically a continuous governing equation from the kinetic Boltzmann modeling to the hydrodynamic Navier-Stokes dynamics should be used for its efficient description. However, due to the difficulties of a direct modeling of flow physics in the scale between the kinetic and hydrodynamic ones, there is basically no reliable theory or valid governing equations to cover the whole transition regime, except resolving flow physics always down to the mean free path scale, such as the direct Boltzmann solver and the Direct Simulation Monte Carlo (DSMC) method. In fact, it is an unresolved problem about the exact scale for the validity of the NS equations, especially in the small Reynolds number cases. The computational fluid dynamics (CFD) is usually based on the numerical solution of partial differential equations (PDEs), and it targets on the recovering of the exact solution of the PDEs as mesh size and time step converging to zero. This methodology can be hardly applied to solve the multiple scale problem efficiently because there is no such a complete PDE for flow physics through a continuous variation of scales. For the non-equilibrium flow study, the direct

  1. Modelling of spark to ignition transition in gas mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Akram, M.

    1996-10-01

    This thesis pertains to the models for studying sparking in chemically inert gases. The processes taking place in a spark to flame transition can be segregated into physical and chemical processes, and this study is focused on physical processes. The plasma is regarded as a single-substance material. One and two-dimensional models are developed. The transfer of electrical energy into thermal energy of the gas and its redistribution in space and time along with the evolution of a plasma kernel is studied in the time domain ranging from 10 ns to 40 micros. In the case of ultra-fast sparks, the propagation of the shock and its reflection from a rigid wall is presented. The influence of electrode shape and the gap size on the flow structure development is found to be a dominating factor. It is observed that the flow structure that has developed in the early stage more or less prevails at later stages and strongly influences the shape and evolution of the hot kernel. The electrode geometry and configuration are responsible for the development of the flow structure. The strength of the vortices generated in the flow field is influenced by the power input to the gap and their location of emergence is dictated by the electrode shape and configuration. The heat transfer after 2 micros in the case of ultra-fast sparks is dominated by convection and diffusion. The strong mixing produced by hydrodynamic effects and the electrode geometry give the indication that the magnetic pinch effect might be negligible. Finally, a model for a multicomponent gas mixture is presented. The chemical kinetics mechanism for dissociation and ionization is introduced. 56 refs

  2. Modelling long run strategic behaviour on the liberalised European gas market

    International Nuclear Information System (INIS)

    Mulder, Machiel; Zwart, Gijsbert

    2005-01-01

    In gas markets, intertemporal constraints are of particular importance due to the finiteness of gas resources. In particular in the UK and the Netherlands, gas resources are expected to dry up on the medium term, giving rise to a positive resource rent of the gas. On shorter time scales, decisions on investments in production, transmission, storage and LNG terminal capacities affect short term output decisions in following years, while within the year prices across seasons are related through storage decisions. We develop a model of strategic behaviour on the European gas markets that incorporates such intertemporal relations. We take into account interactions between strategic producers of gas, price-taking transmission companies, and traders arbitraging the markets by transporting gas across borders, storing gas across seasons, and importing LNG. As a case study, we use the model to explore the impacts on producer behaviour and infrastructure investments of a cap on production from a large gas field in the Netherlands. (Author)

  3. Modeling of gas flow and deposition profile in HWCVD processes

    Energy Technology Data Exchange (ETDEWEB)

    Pflug, Andreas; Höfer, Markus; Harig, Tino; Armgardt, Markus; Britze, Chris; Siemers, Michael; Melzig, Thomas; Schäfer, Lothar

    2015-11-30

    Hot wire chemical vapor deposition (HWCVD) is a powerful technology for deposition of high quality films on large area, where drawbacks of plasma based technology such as defect generation by ion bombardment and high equipment costs are omitted. While processes for diamond coatings using H{sub 2} and CH{sub 4} as precursor have been investigated in detail since 1990 and have been transferred to industry, research also focuses on silicon based coatings with H{sub 2}, SiH{sub 4} and NH{sub 3} as process gases. HWCVD of silicon based coatings is a promising alternative for state-of-the-art radiofrequency-plasma enhanced chemical vapor deposition reactors. The film formation in HWCVD results from an interaction of several concurrent chemical reactions such as gas phase chemistry, film deposition, abstraction of surplus hydrogen bonds and etching by atomic hydrogen. Since there is no easy relation between process parameters and resulting deposition profiles, substantial experimental effort is required to optimize the process for a given film specification and the desired film uniformity. In order to obtain a deeper understanding of the underlying mechanisms and to enable an efficient way of process optimization, simulation methods come into play. While diamond deposition occurs at pressures in the range of several kPa HWCVD deposition of Si based coatings operates at pressures in the 0.1–30 Pa range. In this pressure regime, particle based simulation methods focused on solving the Boltzmann equation are computationally feasible. In comparison to computational fluid dynamics this yields improved accuracy even near small gaps or orifices, where characteristic geometric dimensions approach the order of the mean free path of gas molecules. At Fraunhofer IST, a parallel implementation of the Direct Simulation Monte Carlo (DSMC) method extended by a reactive wall chemistry model is developed. To demonstrate the feasibility of three-dimensional simulation of HWCVD processes

  4. Greenhouse Gas Source Attribution: Measurements Modeling and Uncertainty Quantification

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhen [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Safta, Cosmin [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sargsyan, Khachik [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Najm, Habib N. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); van Bloemen Waanders, Bart Gustaaf [Sandia National Lab. (SNL-CA), Livermore, CA (United States); LaFranchi, Brian W. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Ivey, Mark D. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Schrader, Paul E. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Michelsen, Hope A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Bambha, Ray P. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2014-09-01

    In this project we have developed atmospheric measurement capabilities and a suite of atmospheric modeling and analysis tools that are well suited for verifying emissions of green- house gases (GHGs) on an urban-through-regional scale. We have for the first time applied the Community Multiscale Air Quality (CMAQ) model to simulate atmospheric CO2 . This will allow for the examination of regional-scale transport and distribution of CO2 along with air pollutants traditionally studied using CMAQ at relatively high spatial and temporal resolution with the goal of leveraging emissions verification efforts for both air quality and climate. We have developed a bias-enhanced Bayesian inference approach that can remedy the well-known problem of transport model errors in atmospheric CO2 inversions. We have tested the approach using data and model outputs from the TransCom3 global CO2 inversion comparison project. We have also performed two prototyping studies on inversion approaches in the generalized convection-diffusion context. One of these studies employed Polynomial Chaos Expansion to accelerate the evaluation of a regional transport model and enable efficient Markov Chain Monte Carlo sampling of the posterior for Bayesian inference. The other approach uses de- terministic inversion of a convection-diffusion-reaction system in the presence of uncertainty. These approaches should, in principle, be applicable to realistic atmospheric problems with moderate adaptation. We outline a regional greenhouse gas source inference system that integrates (1) two ap- proaches of atmospheric dispersion simulation and (2) a class of Bayesian inference and un- certainty quantification algorithms. We use two different and complementary approaches to simulate atmospheric dispersion. Specifically, we use a Eulerian chemical transport model CMAQ and a Lagrangian Particle Dispersion Model - FLEXPART-WRF. These two models share the same WRF

  5. Modelling of Spherical Gas Bubble Oscillations and Sonoluminescence

    Science.gov (United States)

    Prosperetti, A.; Hao, Y.

    1999-01-01

    The discovery of single-bubble sonoluminescence has led to a renewed interest in the forced radial oscillations of gas bubbles. Many of the more recent studies devoted to this topic have used several simplifications in the modelling, and in particular in accounting for liquid compressibility and thermal processes in the bubble. In this paper the significance of these simplifications is explored by contrasting the results of Lohse and co-workers with those of a more detailed model. It is found that, even though there may be little apparent difference between the radius-versus time behaviour of the bubble as predicted by the two models, quantities such as the spherical stability boundary and the threshold for rectified diffusion are affected in a quantitatively significant way. These effects are a manifestation of the subtle dependence upon dissipative processes of the phase of radial motion with respect to the driving sound field. The parameter space region, where according to the theory of Lohse and co-workers, sonoluminescence should be observable, is recalculated with the new model and is found to be enlarged with respect to the earlier estimate. The dependence of this parameter region on sound frequency is also illustrated.

  6. Modeling the Gas Nitriding Process of Low Alloy Steels

    Science.gov (United States)

    Yang, M.; Zimmerman, C.; Donahue, D.; Sisson, R. D.

    2013-07-01

    The effort to simulate the nitriding process has been ongoing for the last 20 years. Most of the work has been done to simulate the nitriding process of pure iron. In the present work a series of experiments have been done to understand the effects of the nitriding process parameters such as the nitriding potential, temperature, and time as well as surface condition on the gas nitriding process for the steels. The compound layer growth model has been developed to simulate the nitriding process of AISI 4140 steel. In this paper the fundamentals of the model are presented and discussed including the kinetics of compound layer growth and the determination of the nitrogen diffusivity in the diffusion zone. The excellent agreements have been achieved for both as-washed and pre-oxided nitrided AISI 4140 between the experimental data and simulation results. The nitrogen diffusivity in the diffusion zone is determined to be constant and only depends on the nitriding temperature, which is ~5 × 10-9 cm2/s at 548 °C. It proves the concept of utilizing the compound layer growth model in other steels. The nitriding process of various steels can thus be modeled and predicted in the future.

  7. Modelling gas migration in compacted bentonite: GAMBIT Club Phase 2. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Swift, B.T.; Hoch, A.R.; Rodwell, W.R. [AEA Technology (United Kingdom)

    2001-01-01

    This report describes the second phase of a programme of work to develop a computational model of gas migration through highly compacted bentonite. Experimental data that have appeared since the earlier report are reviewed for the additional information they might provide on the mechanism of gas migration in bentonite. Experiments carried out by Horseman and Harrigton (British Geological Survey) continued to provide the main data sets used in model evaluation. The earlier work (POSIVA Report 98-08) had resulted in a preliminary model of gas migration whose main features are gas invasion by microcrack propagation, and dilation of the pathways formed with increasing gas pressure. New work was carried out to further explore the capabilities of this model. In addition, a feature was added to the model to simulate gas pathway creation by water displacement rather than crack propagation. The development of a new alternative gas migration model is described. This is based on a volume-averaged representation of gas migration rather than on a description of flow in discrete pathways. Evaluation of this alternative model showed that it can produce similar agreement with experimental results to the other models examined. The implications of flow geometry, confining conditions and flow boundary conditions on gas migration behaviour in bentonite are reviewed. Proposals are made for the development of the new model into a tool for simulating gas migration through a bentonite buffer around a waste canister, and for possible enhancements to the model that might remove some of its currently perceived deficiencies. (orig.)

  8. Ammonia concentration modeling based on retained gas sampler data

    International Nuclear Information System (INIS)

    Terrones, G.; Palmer, B.J.; Cuta, J.M.

    1997-09-01

    The vertical ammonia concentration distributions determined by the retained gas sampler (RGS) apparatus were modeled for double-shell tanks (DSTs) AW-101, AN-103, AN-104, and AN-105 and single-shell tanks (SSTs) A-101, S-106, and U-103. One the vertical transport of ammonia in the tanks were used for the modeling. Transport in the non-convective settled solids and floating solids layers is assumed to occur primarily via some type of diffusion process, while transport in the convective liquid layers is incorporated into the model via mass transfer coefficients based on empirical correlations. Mass transfer between the top of the waste and the tank headspace and the effects of ventilation of the headspace are also included in the models. The resulting models contain a large number of parameters, but many of them can be determined from known properties of the waste configuration or can be estimated within reasonable bounds from data on the waste samples themselves. The models are used to extract effective diffusion coefficients for transport in the nonconvective layers based on the measured values of ammonia from the RGS apparatus. The modeling indicates that the higher concentrations of ammonia seen in bubbles trapped inside the waste relative to the ammonia concentrations in the tank headspace can be explained by a combination of slow transport of ammonia via diffusion in the nonconvective layers and ventilation of the tank headspace by either passive or active means. Slow transport by diffusion causes a higher concentration of ammonia to build up deep within the waste until the concentration gradients between the interior and top of the waste are sufficient to allow ammonia to escape at the same rate at which it is being generated in the waste

  9. A coupling model for gas diffusion and seepage in SRV section of shale gas reservoirs

    Directory of Open Access Journals (Sweden)

    Shusheng Gao

    2017-03-01

    Full Text Available A prerequisite to effective shale gas development is a complicated fracture network generated by extensive and massive fracturing, which is called SRV (stimulated reservoir volume section. Accurate description of gas flow behaviors in such section is fundamental for productivity evaluation and production performance prediction of shale gas wells. The SRV section is composed of bedrocks with varying sizes and fracture networks, which exhibit different flow behaviors – gas diffusion in bedrocks and gas seepage in fractures. According to the porosity and permeability and the adsorption, diffusion and seepage features of bedrocks and fractures in a shale gas reservoir, the material balance equations were built for bedrocks and fractures respectively and the continuity equations of gas diffusion and seepage in the SRV section were derived. For easy calculation, the post-frac bedrock cube was simplified to be a sphere in line with the principle of volume consistency. Under the assumption of quasi-steady flow behavior at the cross section of the sphere, the gas channeling equation was derived based on the Fick's laws of diffusion and the density function of gas in bedrocks and fractures. The continuity equation was coupled with the channeling equation to effectively characterize the complicated gas flow behavior in the SRV section. The study results show that the gas diffusivity in bedrocks and the volume of bedrocks formed by volume fracturing (or the scale of fracturing jointly determines the productivity and stable production period of a shale gas well. As per the actual calculation for the well field A in the Changning–Weiyuan Block in the Sichuan Basin, the matrix has low gas diffusivity – about 10−5 cm2/s and a large volume with an equivalent sphere radius of 6.2 m, hindering the gas channeling from bedrocks to fractures and thereby reducing the productivity of the shale gas well. It is concluded that larger scale of volume fracturing

  10. Modeling of Gas Production from Shale Reservoirs Considering Multiple Transport Mechanisms.

    Directory of Open Access Journals (Sweden)

    Chaohua Guo

    Full Text Available Gas transport in unconventional shale strata is a multi-mechanism-coupling process that is different from the process observed in conventional reservoirs. In micro fractures which are inborn or induced by hydraulic stimulation, viscous flow dominates. And gas surface diffusion and gas desorption should be further considered in organic nano pores. Also, the Klinkenberg effect should be considered when dealing with the gas transport problem. In addition, following two factors can play significant roles under certain circumstances but have not received enough attention in previous models. During pressure depletion, gas viscosity will change with Knudsen number; and pore radius will increase when the adsorption gas desorbs from the pore wall. In this paper, a comprehensive mathematical model that incorporates all known mechanisms for simulating gas flow in shale strata is presented. The objective of this study was to provide a more accurate reservoir model for simulation based on the flow mechanisms in the pore scale and formation geometry. Complex mechanisms, including viscous flow, Knudsen diffusion, slip flow, and desorption, are optionally integrated into different continua in the model. Sensitivity analysis was conducted to evaluate the effect of different mechanisms on the gas production. The results showed that adsorption and gas viscosity change will have a great impact on gas production. Ignoring one of following scenarios, such as adsorption, gas permeability change, gas viscosity change, or pore radius change, will underestimate gas production.

  11. Natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Fraser, J W

    1967-08-01

    This report on the natural gas industry of Canada includes: composition and uses of natural gas, production statistics, exploration and development, reserve estimates, natural gas processing, transportation, and marketing. For the Canadian natural gas industry, 1966 was a year of moderate expansion in all phases, with a strong demand continuing for sulfur and liquid hydrocarbons produced as by-products of gas processing. Value of natural gas production increased to $199 million and ranked sixth in terms of value of mineral ouput in Canada. Currently, natural gas provides over 70% of Canada's energy requirements. Proved remaining marketable reserves are estimated to be in excess of a 29-yr supply.

  12. Prenatal androgen excess negatively impacts body fat distribution in a nonhuman primate model of polycystic ovary syndrome.

    Science.gov (United States)

    Bruns, C M; Baum, S T; Colman, R J; Dumesic, D A; Eisner, J R; Jensen, M D; Whigham, L D; Abbott, D H

    2007-10-01

    Prenatally androgenized (PA) female rhesus monkeys share metabolic abnormalities in common with polycystic ovary syndrome (PCOS) women. Early gestation exposure (E) results in insulin resistance, impaired pancreatic beta-cell function and type 2 diabetes, while late gestation exposure (L) results in supranormal insulin sensitivity that declines with increasing body mass index (BMI). To determine whether PA females have altered body fat distribution. Five early-treated PA (EPA), five late-treated PA (LPA) and five control adult female monkeys underwent somatometrics, dual-X-ray absorptiometry (DXA) and abdominal computed tomography (CT). Five control and five EPA females underwent an intravenous glucose tolerance test to assess the relationship between body composition and glucoregulation. There were no differences in age, weight, BMI or somatometrics. LPA females had approximately 20% greater DXA-determined total fat and percent body fat, as well as total and percent abdominal fat than EPA or control females (Pandrogenization in female rhesus monkeys induces adiposity-dependent visceral fat accumulation, and late gestation androgenization causes increased total body and non-visceral fat mass. Early gestation androgenization induces visceral fat-dependent hyperinsulinemia. The relationship between the timing of prenatal androgen exposure and body composition phenotypes in this nonhuman primate model for PCOS may provide insight into the heterogeneity of metabolic defects found in PCOS women.

  13. Mechanisms and modelling of gas migration from deep radioactive waste repositories

    International Nuclear Information System (INIS)

    Rodwell, W.R.; Nash, P.J.

    1992-06-01

    This report discusses the mechanisms by which gas is able to migrate through the far-field. The mechanisms available are diffusion or advection of gas dissolved in groundwater or free gas phase flow as either bubbles or a continuous stream of gas. Modelling approaches adopted to assess the migration are (a) simple use of Darcy's law with an effective permeability to gas, (b) the development of a model based on the representation of the far-field rock as a bundle of capillaries with a suitable distribution of radii, and (c) the use of a numerical model of two-phase flow in porous media. Finally, surveys have been carried out of published work on gas escape from underground storage caverns and of literature relating to gas movement from underground hydrocarbon accumulations to determine whether these may be potential sources of data or understanding of underground gas migration relevant to that from deep waste repositories. (author)

  14. Modelling carbon membranes for gas and isotope separation.

    Science.gov (United States)

    Jiao, Yan; Du, Aijun; Hankel, Marlies; Smith, Sean C

    2013-04-14

    Molecular modelling has become a useful and widely applied tool to investigate separation and diffusion behavior of gas molecules through nano-porous low dimensional carbon materials, including quasi-1D carbon nanotubes and 2D graphene-like carbon allotropes. These simulations provide detailed, molecular level information about the carbon framework structure as well as dynamics and mechanistic insights, i.e. size sieving, quantum sieving, and chemical affinity sieving. In this perspective, we revisit recent advances in this field and summarize separation mechanisms for multicomponent systems from kinetic and equilibrium molecular simulations, elucidating also anomalous diffusion effects induced by the confining pore structure and outlining perspectives for future directions in this field.

  15. Polyakov loop and the hadron resonance gas model.

    Science.gov (United States)

    Megías, E; Arriola, E Ruiz; Salcedo, L L

    2012-10-12

    The Polyakov loop has been used repeatedly as an order parameter in the deconfinement phase transition in QCD. We argue that, in the confined phase, its expectation value can be represented in terms of hadronic states, similarly to the hadron resonance gas model for the pressure. Specifically, L(T)≈1/2[∑(α)g(α)e(-Δ(α)/T), where g(α) are the degeneracies and Δ(α) are the masses of hadrons with exactly one heavy quark (the mass of the heavy quark itself being subtracted). We show that this approximate sum rule gives a fair description of available lattice data with N(f)=2+1 for temperatures in the range 150 MeVmodels. For temperatures below 150 MeV different lattice results disagree. One set of data can be described if exotic hadrons are present in the QCD spectrum while other sets do not require such states.

  16. New models for success emerge for US natural gas industry

    International Nuclear Information System (INIS)

    Addy, W.M.; Hutchinson, R.A.

    1994-01-01

    Very few companies in the US natural gas industry are confident in their ability to compete effectively in the brave new world of deregulation. Boston Consulting Group recently conducted an internal study to help the industry think about its future and identify models for success in this new environment. The authors examined the historical performance of 800 companies using several shareholder-value indicators, including cash-flow returns on investment, a measure of cash returns on cash invested that correlates closely to share price. Based on that review and discussions with investment managers and industry analysts, the authors were able to focus on a handful of companies that actually have thrived and created value against the difficult landscape of the past decade. Interviews with their senior executives provided important strategic and operational insights

  17. Modeling of information flows in natural gas storage facility

    Science.gov (United States)

    Ranjbari, Leyla; Bahar, Arifah; Aziz, Zainal Abdul

    2013-09-01

    The paper considers the natural-gas storage valuation based on the information-based pricing framework of Brody-Hughston-Macrina (BHM). As opposed to many studies which the associated filtration is considered pre-specified, this work tries to construct the filtration in terms of the information provided to the market. The value of the storage is given by the sum of the discounted expectations of the cash flows under risk-neutral measure, conditional to the constructed filtration with the Brownian bridge noise term. In order to model the flow of information about the cash flows, we assume the existence of a fixed pricing kernel with liquid, homogenous and incomplete market without arbitrage.

  18. Measuring excess capital capacity in agricultural production

    NARCIS (Netherlands)

    Zhengfei, G.; Kumbhakar, S.C.; Myers, R.J.; Oude Lansink, A.G.J.M.

    2009-01-01

    We introduce the concept "excess capital capacity" and employ a stochastic input requirement frontier to measure excess capital capacity in agricultural production. We also propose a two-step estimation method that allows endogenous regressors in stochastic frontier models. The first step uses

  19. Superconductors with excess quasiparticles

    International Nuclear Information System (INIS)

    Elesin, V.F.; Kopaev, Y.V.

    1981-01-01

    This review presents a systematic kinetic theory of nonequilibrium phenomena in superconductors with excess quasiparticles created by electromagnetic or tunnel injection. The energy distributions of excess quasiparticles and of nonequilibrium phonons, dependence of the order parameter on the power and frequency (or intensity) of the electromagnetic field, magnetic properties of nonequilibrium superconductors, I-V curves of superconductor-insulator-superconductor junctions, and other properties are described in detail. The stability of superconducting states far from thermodynamic equilibrium is investigated and it is shown that characteristic instabilities leading to the formation of nonuniform states of a new type or phase transitions of the first kind are inherent to superconductors with excess quasiparticles. The results are compared with experimental data

  20. Multiscale model reduction for shale gas transport in fractured media

    KAUST Repository

    Akkutlu, I. Y.

    2016-05-18

    In this paper, we develop a multiscale model reduction technique that describes shale gas transport in fractured media. Due to the pore-scale heterogeneities and processes, we use upscaled models to describe the matrix. We follow our previous work (Akkutlu et al. Transp. Porous Media 107(1), 235–260, 2015), where we derived an upscaled model in the form of generalized nonlinear diffusion model to describe the effects of kerogen. To model the interaction between the matrix and the fractures, we use Generalized Multiscale Finite Element Method (Efendiev et al. J. Comput. Phys. 251, 116–135, 2013, 2015). In this approach, the matrix and the fracture interaction is modeled via local multiscale basis functions. In Efendiev et al. (2015), we developed the GMsFEM and applied for linear flows with horizontal or vertical fracture orientations aligned with a Cartesian fine grid. The approach in Efendiev et al. (2015) does not allow handling arbitrary fracture distributions. In this paper, we (1) consider arbitrary fracture distributions on an unstructured grid; (2) develop GMsFEM for nonlinear flows; and (3) develop online basis function strategies to adaptively improve the convergence. The number of multiscale basis functions in each coarse region represents the degrees of freedom needed to achieve a certain error threshold. Our approach is adaptive in a sense that the multiscale basis functions can be added in the regions of interest. Numerical results for two-dimensional problem are presented to demonstrate the efficiency of proposed approach. © 2016 Springer International Publishing Switzerland

  1. Estimating the decline in excess risk of chronic obstructive pulmonary disease following quitting smoking - a systematic review based on the negative exponential model.

    Science.gov (United States)

    Lee, Peter N; Fry, John S; Forey, Barbara A

    2014-03-01

    We quantified the decline in COPD risk following quitting using the negative exponential model, as previously carried out for other smoking-related diseases. We identified 14 blocks of RRs (from 11 studies) comparing current smokers, former smokers (by time quit) and never smokers, some studies providing sex-specific blocks. Corresponding pseudo-numbers of cases and controls/at risk formed the data for model-fitting. We estimated the half-life (H, time since quit when the excess risk becomes half that for a continuing smoker) for each block, except for one where no decline with quitting was evident, and H was not estimable. For the remaining 13 blocks, goodness-of-fit to the model was generally adequate, the combined estimate of H being 13.32 (95% CI 11.86-14.96) years. There was no heterogeneity in H, overall or by various studied sources. Sensitivity analyses allowing for reverse causation or different assumed times for the final quitting period little affected the results. The model summarizes quitting data well. The estimate of 13.32years is substantially larger than recent estimates of 4.40years for ischaemic heart disease and 4.78years for stroke, and also larger than the 9.93years for lung cancer. Heterogeneity was unimportant for COPD, unlike for the other three diseases. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  2. Estimating the decline in excess risk of cerebrovascular disease following quitting smoking--a systematic review based on the negative exponential model.

    Science.gov (United States)

    Lee, Peter N; Fry, John S; Thornton, Alison J

    2014-02-01

    We attempted to quantify the decline in stroke risk following quitting using the negative exponential model, with methodology previously employed for IHD. We identified 22 blocks of RRs (from 13 studies) comparing current smokers, former smokers (by time quit) and never smokers. Corresponding pseudo-numbers of cases and controls/at risk formed the data for model-fitting. We tried to estimate the half-life (H, time since quit when the excess risk becomes half that for a continuing smoker) for each block. The method failed to converge or produced very variable estimates of H in nine blocks with a current smoker RR <1.40. Rejecting these, and combining blocks by amount smoked in one study where problems arose in model-fitting, the final analyses used 11 blocks. Goodness-of-fit was adequate for each block, the combined estimate of H being 4.78(95%CI 2.17-10.50) years. However, considerable heterogeneity existed, unexplained by any factor studied, with the random-effects estimate 3.08(1.32-7.16). Sensitivity analyses allowing for reverse causation or differing assumed times for the final quitting period gave similar results. The estimates of H are similar for stroke and IHD, and the individual estimates similarly heterogeneous. Fitting the model is harder for stroke, due to its weaker association with smoking. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  3. Time series analysis based on two-part models for excessive zero count data to detect farm-level outbreaks of swine echinococcosis during meat inspections.

    Science.gov (United States)

    Adachi, Yasumoto; Makita, Kohei

    2017-12-01

    Echinococcus multilocularis is a parasite that causes highly pathogenic zoonoses and is maintained in foxes and rodents on Hokkaido Island, Japan. Detection of E. multilocularis infections in swine is epidemiologically important. In Hokkaido, administrative information is provided to swine producers based on the results of meat inspections. However, as the current criteria for providing administrative information often results in delays in providing information to producers, novel criteria are needed. Time series models were developed to monitor autocorrelations between data and lags using data collected from 84 producers at the Higashi-Mokoto Meat Inspection Center between April 2003 and November 2015. The two criteria were quantitatively compared using the sign test for the ability to rapidly detect farm-level outbreaks. Overall, the time series models based on an autoexponentially regressed zero-inflated negative binomial distribution with 60th percentile cumulative distribution function of the model detected outbreaks earlier more frequently than the current criteria (90.5%, 276/305, ppart model with autoexponential regression can adequately deal with data involving an excessive number of zeros and that the novel criteria overcome disadvantages of the current criteria to provide an earlier indication of increases in the rate of echinococcosis. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Critical comparison of hydrodynamic models for gas-solid fluidized beds - Part II: freely bubbling gas-solid fluidized beds

    NARCIS (Netherlands)

    Patil, D.J.; van Sint Annaland, M.; Kuipers, J.A.M.

    2005-01-01

    Correct prediction of spontaneous bubble formation in freely bubbling gas¿solid fluidized beds using Eulerian models, strongly depends on the description of the internal momentum transfer in the particulate phase. In this part, the comparison of the simple classical model, describing the solid phase

  5. The future of subsidence modelling: compaction and subsidence due to gas depletion of the Groningen gas field in the Netherlands

    NARCIS (Netherlands)

    Thienen-Visser, K. van; Fokker, P.A.

    2017-01-01

    The Groningen gas field has shown considerable compaction and subsidence since starting production in the early 1960s. The behaviour is understood from the geomechanical response of the reservoir pressure depletion. By integrating surface movement measurements and modelling, the model parameters can

  6. Method for mapping a natural gas leak

    Science.gov (United States)

    Reichardt, Thomas A [Livermore, CA; Luong, Amy Khai [Dublin, CA; Kulp, Thomas J [Livermore, CA; Devdas, Sanjay [Albany, CA

    2009-02-03

    A system is described that is suitable for use in determining the location of leaks of gases having a background concentration. The system is a point-wise backscatter absorption gas measurement system that measures absorption and distance to each point of an image. The absorption measurement provides an indication of the total amount of a gas of interest, and the distance provides an estimate of the background concentration of gas. The distance is measured from the time-of-flight of laser pulse that is generated along with the absorption measurement light. The measurements are formatted into an image of the presence of gas in excess of the background. Alternatively, an image of the scene is superimposed on the image of the gas to aid in locating leaks. By further modeling excess gas as a plume having a known concentration profile, the present system provides an estimate of the maximum concentration of the gas of interest.

  7. Predictors of excessive use of social media and excessive online gaming in Czech teenagers.

    Science.gov (United States)

    Spilková, Jana; Chomynová, Pavla; Csémy, Ladislav

    2017-12-01

    Background and aims Young people's involvement in online gaming and the use of social media are increasing rapidly, resulting in a high number of excessive Internet users in recent years. The objective of this paper is to analyze the situation of excessive Internet use among adolescents in the Czech Republic and to reveal determinants of excessive use of social media and excessive online gaming. Methods Data from secondary school students (N = 4,887) were collected within the 2015 European School Survey Project on Alcohol and Other Drugs. Logistic regression models were constructed to describe the individual and familial discriminative factors and the impact of the health risk behavior of (a) excessive users of social media and (b) excessive players of online games. Results The models confirmed important gender-specific distinctions - while girls are more prone to online communication and social media use, online gaming is far more prevalent among boys. The analysis did not indicate an influence of family composition on both the excessive use of social media and on excessive online gaming, and only marginal effects for the type of school attended. We found a connection between the excessive use of social media and binge drinking and an inverse relation between excessive online gaming and daily smoking. Discussion and conclusion The non-existence of significant associations between family environment and excessive Internet use confirmed the general, widespread of this phenomenon across the social and economic strata of the teenage population, indicating a need for further studies on the topic.

  8. A current induced diffusion model of gas sputtering

    International Nuclear Information System (INIS)

    Hotston, E.S.

    1980-01-01

    A model is proposed to explain the experimental results on deuteron trapping in stainless steel targets at low temperatures carried out at Garching and Culham. The model proposes that the ions are trapped in two kinds of sites: Deep sites with high activation energy and shallow sites of low activation energy. Trapped deuterons reach the surface of the target by being expelled from shallow sites by the action of the ion beam and migrate to nearby sites in a random way, thus moving by a bombardment induced diffusion. Ions diffusing to the target surface and being released are said to be sputtered from the target. It has been necessary to assume numerical values for sizes of some of the processes which occur. With a suitable choice of values the model successfully predicts the numbers of deuterons trapped per unit area of the target, the obserbed density profile of the trapped ions and the threshold at which sputtering starts. The model also successfully describes the replacement of the trapped deuterons by protons, when the deuteron beam is replaced by a proton beam. The collision cross-section for beam ions and ions trapped in shallow sites is too large, 4 x 10 -13 cm 2 , for a binary collision and it is tentatively suggested that the ions in the shallow sites may be in small voids in the target which may be connected with blister formation. Comparison of the present model with one being developed to describe the trapping of deuterons in carbon suggests that it may be possible to describe all gas sputtering experiments in terms of diffusion processes. (orig.)

  9. Theoretical modeling of Comptonized X-ray spectra of super-Eddington accretion flow: Origin of hard excess in ultraluminous X-ray sources

    Science.gov (United States)

    Kitaki, Takaaki; Mineshige, Shin; Ohsuga, Ken; Kawashima, Tomohisa

    2017-12-01

    X-ray continuum spectra of super-Eddington accretion flow are studied by means of Monte Carlo radiative transfer simulations based on the radiation hydrodynamic simulation data, in which both thermal- and bulk-Compton scatterings are taken into account. We compare the calculated spectra of accretion flow around black holes with masses of MBH = 10, 102, 103, and 104 M⊙ for a fixed mass injection rate (from the computational boundary at 103 rs) of 103 LEdd/c2 (with rs, LEdd, and c being the Schwarzschild radius, the Eddington luminosity, and the speed of light, respectively). The soft X-ray spectra exhibit mass dependence in accordance with the standard-disk relation; the maximum surface temperature is scaled as T ∝ M_{ BH}^{ -1/4}. The spectra in the hard X-ray band, by contrast with soft X-ray, look to be quite similar among different models, if we normalize the radiation luminosity by MBH. This reflects that the hard component is created by thermal- and bulk-Compton scatterings of soft photons originating from an accretion flow in the overheated and/or funnel regions, the temperatures of which have no dependence on mass. The hard X-ray spectra can be reproduced by a Wien spectrum with the temperature of T ˜ 3 keV accompanied by a hard excess at photon energy above several keV. The excess spectrum can be fitted well with a power law with a photon index of Γ ˜ 3. This feature is in good agreement with that of the recent NuSTAR observations of ULXs (ultra-luminous X-ray sources).

  10. Disposition of excess material

    International Nuclear Information System (INIS)

    Hall, J.C.

    1978-01-01

    This paper reviews briefly the means available to an enrichment customer to dispose of excess material scheduled for delivery under a fixed-commitment contract, other than through termination of the related separative work. The methods are as follows: (1) sales; (2) use in facilities covered by other DOE contracts; and (3) assignment

  11. HIV Excess Cancers JNCI

    Science.gov (United States)

    In 2010, an estimated 7,760 new cancers were diagnosed among the nearly 900,000 Americans known to be living with HIV infection. According to the first comprehensive study in the United States, approximately half of these cancers were in excess of what wo

  12. Mixing the Green-Ampt model and Curve Number method as an empirical tool for rainfall excess estimation in small ungauged catchments.

    Science.gov (United States)

    Grimaldi, S.; Petroselli, A.; Romano, N.

    2012-04-01

    The Soil Conservation Service - Curve Number (SCS-CN) method is a popular rainfall-runoff model that is widely used to estimate direct runoff from small and ungauged basins. The SCS-CN is a simple and valuable approach to estimate the total stream-flow volume generated by a storm rainfall, but it was developed to be used with daily rainfall data. To overcome this drawback, we propose to include the Green-Ampt (GA) infiltration model into a mixed procedure, which is referred to as CN4GA (Curve Number for Green-Ampt), aiming to distribute in time the information provided by the SCS-CN method so as to provide estimation of sub-daily incremental rainfall excess. For a given storm, the computed SCS-CN total net rainfall amount is used to calibrate the soil hydraulic conductivity parameter of the Green-Ampt model. The proposed procedure was evaluated by analyzing 100 rainfall-runoff events observed in four small catchments of varying size. CN4GA appears an encouraging tool for predicting the net rainfall peak and duration values and has shown, at least for the test cases considered in this study, a better agreement with observed hydrographs than that of the classic SCS-CN method.

  13. Mathematical Modeling of Nonstationary Separation Processes in Gas Centrifuge Cascade for Separation of Multicomponent Isotope Mixtures

    Directory of Open Access Journals (Sweden)

    Orlov Alexey

    2016-01-01

    Full Text Available This article presents results of development of the mathematical model of nonstationary separation processes occurring in gas centrifuge cascades for separation of multicomponent isotope mixtures. This model was used for the calculation parameters of gas centrifuge cascade for separation of germanium isotopes. Comparison of obtained values with results of other authors revealed that developed mathematical model is adequate to describe nonstationary separation processes in gas centrifuge cascades for separation of multicomponent isotope mixtures.

  14. Mathematical Modeling of Nonstationary Separation Processes in Gas Centrifuge Cascade for Separation of Multicomponent Isotope Mixtures

    OpenAIRE

    Orlov Alexey; Ushakov Anton; Sovach Victor

    2016-01-01

    This article presents results of development of the mathematical model of nonstationary separation processes occurring in gas centrifuge cascades for separation of multicomponent isotope mixtures. This model was used for the calculation parameters of gas centrifuge cascade for separation of germanium isotopes. Comparison of obtained values with results of other authors revealed that developed mathematical model is adequate to describe nonstationary separation processes in gas centrifuge casca...

  15. Mathematical model of nonstationary hydraulic processes in gas centrifuge cascade for separation of multicomponent isotope mixtures

    OpenAIRE

    Orlov, Aleksey Alekseevich; Ushakov, Anton; Sovach, Victor

    2017-01-01

    The article presents results of development of a mathematical model of nonstationary hydraulic processes in gas centrifuge cascade for separation of multicomponent isotope mixtures. This model was used for the calculation parameters of gas centrifuge cascade for separation of silicon isotopes. Comparison of obtained values with results of other authors revealed that developed mathematical model is adequate to describe nonstationary hydraulic processes in gas centrifuge cascades for separation...

  16. Universal model for water costs of gas exchange by animals and plants

    OpenAIRE

    Woods, H. Arthur; Smith, Jennifer N.

    2010-01-01

    For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface t...

  17. Dynamic modeling of gas turbines in integrated gasification fuel cell systems

    Science.gov (United States)

    Maclay, James Davenport

    2009-12-01

    Solid oxide fuel cell-gas turbine (SOFC-GT) hybrid systems for use in integrated gasification fuel cell (IGFC) systems operating on coal will stretch existing fossil fuel reserves, generate power with less environmental impact, while having a cost of electricity advantage over most competing technologies. However, the dynamic performance of a SOFC-GT in IGFC applications has not been previously studied in detail. Of particular importance is how the turbo-machinery will be designed, controlled and operated in such applications; this is the focus of the current work. Perturbation and dynamic response analyses using numerical SimulinkRTM models indicate that compressor surge is the predominant concern for safe dynamic turbo-machinery operation while shaft over-speed and excessive turbine inlet temperatures are secondary concerns. Fuel cell temperature gradients and anode-cathode differential pressures were found to be the greatest concerns for safe dynamic fuel cell operation. Two control strategies were compared, that of constant gas turbine shaft speed and constant fuel cell temperature, utilizing a variable speed gas turbine. Neither control strategy could eliminate all vulnerabilities during dynamic operation. Constant fuel cell temperature control ensures safe fuel cell operation, while constant speed control does not. However, compressor surge is more likely with constant fuel cell temperature control than with constant speed control. Design strategies that provide greater surge margin while utilizing constant fuel cell temperature control include increasing turbine design mass flow and decreasing turbine design inlet pressure, increasing compressor design pressure ratio and decreasing compressor design mass flow, decreasing plenum volume, decreasing shaft moment of inertia, decreasing fuel cell pressure drop, maintaining constant compressor inlet air temperature. However, these strategies in some cases incur an efficiency penalty. A broad comparison of cycles

  18. Laser-based investigations in gas turbine model combustors

    Science.gov (United States)

    Meier, W.; Boxx, I.; Stöhr, M.; Carter, C. D.

    2010-10-01

    Dynamic processes in gas turbine (GT) combustors play a key role in flame stabilization and extinction, combustion instabilities and pollutant formation, and present a challenge for experimental as well as numerical investigations. These phenomena were investigated in two gas turbine model combustors for premixed and partially premixed CH4/air swirl flames at atmospheric pressure. Optical access through large quartz windows enabled the application of laser Raman scattering, planar laser-induced fluorescence (PLIF) of OH, particle image velocimetry (PIV) at repetition rates up to 10 kHz and the simultaneous application of OH PLIF and PIV at a repetition rate of 5 kHz. Effects of unmixedness and reaction progress in lean premixed GT flames were revealed and quantified by Raman scattering. In a thermo-acoustically unstable flame, the cyclic variation in mixture fraction and its role for the feedback mechanism of the instability are addressed. In a partially premixed oscillating swirl flame, the cyclic variations of the heat release and the flow field were characterized by chemiluminescence imaging and PIV, respectively. Using phase-correlated Raman scattering measurements, significant phase-dependent variations of the mixture fraction and fuel distributions were revealed. The flame structures and the shape of the reaction zones were visualized by planar imaging of OH distribution. The simultaneous OH PLIF/PIV high-speed measurements revealed the time history of the flow field-flame interaction and demonstrated the development of a local flame extinction event. Further, the influence of a precessing vortex core on the flame topology and its dynamics is discussed.

  19. Performance evaluation of Maxwell and Cercignani-Lampis gas-wall interaction models in the modeling of thermally driven rarefied gas transport

    KAUST Repository

    Liang, Tengfei; Li, Qi; Ye, Wenjing

    2013-01-01

    A systematic study on the performance of two empirical gas-wall interaction models, the Maxwell model and the Cercignani-Lampis (CL) model, in the entire Knudsen range is conducted. The models are evaluated by examining the accuracy of key

  20. Overview: Understanding nucleation phenomena from simulations of lattice gas models

    International Nuclear Information System (INIS)

    Binder, Kurt; Virnau, Peter

    2016-01-01

    Monte Carlo simulations of homogeneous and heterogeneous nucleation in Ising/lattice gas models are reviewed with an emphasis on the general insight gained on the mechanisms by which metastable states decay. Attention is paid to the proper distinction of particles that belong to a cluster (droplet), that may trigger a nucleation event, from particles in its environment, a problem crucial near the critical point. Well below the critical point, the lattice structure causes an anisotropy of the interface tension, and hence nonspherical droplet shapes result, making the treatment nontrivial even within the conventional classical theory of homogeneous nucleation. For temperatures below the roughening transition temperature facetted crystals rather than spherical droplets result. The possibility to find nucleation barriers from a thermodynamic analysis avoiding a cluster identification on the particle level is discussed, as well as the question of curvature corrections to the interfacial tension. For the interpretation of heterogeneous nucleation at planar walls, knowledge of contact angles and line tensions is desirable, and methods to extract these quantities from simulations will be mentioned. Finally, also the problem of nucleation near the stability limit of metastable states and the significance of the spinodal curve will be discussed, in the light of simulations of Ising models with medium range interactions.

  1. Modelling the radiolysis of RSG-GAS primary cooling water

    Science.gov (United States)

    Butarbutar, S. L.; Kusumastuti, R.; Subekti, M.; Sunaryo, G. R.

    2018-02-01

    Water chemistry control for light water coolant reactor required a reliable understanding of radiolysis effect in mitigating corrosion and degradation of reactor structure material. It is known that oxidator products can promote the corrosion, cracking and hydrogen pickup both in the core and in the associated piping components of the reactor. The objective of this work is to provide the radiolysis model of RSG GAS cooling water and further more to predict the oxidator concentration which can lead to corrosion of reactor material. Direct observations or measurements of the chemistry in and around the high-flux core region of a nuclear reactor are difficult due to the extreme conditions of high temperature, pressure, and mixed radiation fields. For this reason, chemical models and computer simulations of the radiolysis of water under these conditions are an important route of investigation. FACSIMILE were used to calculate the concentration of O2 formed at relatively long-time by the pure water γ and neutron irradiation (pH=7) at temperature between 25 and 50 °C. This simulation method is based on a complex chemical reaction kinetic. In this present work, 300 MeV-proton were used to mimic γ-rays radiolysis and 2 MeV fast neutrons. Concentration of O2 were calculated at 10-6 - 106 s time scale.

  2. Interacting hadron resonance gas model in the K -matrix formalism

    Science.gov (United States)

    Dash, Ashutosh; Samanta, Subhasis; Mohanty, Bedangadas

    2018-05-01

    An extension of hadron resonance gas (HRG) model is constructed to include interactions using relativistic virial expansion of partition function. The noninteracting part of the expansion contains all the stable baryons and mesons and the interacting part contains all the higher mass resonances which decay into two stable hadrons. The virial coefficients are related to the phase shifts which are calculated using K -matrix formalism in the present work. We have calculated various thermodynamics quantities like pressure, energy density, and entropy density of the system. A comparison of thermodynamic quantities with noninteracting HRG model, calculated using the same number of hadrons, shows that the results of the above formalism are larger. A good agreement between equation of state calculated in K -matrix formalism and lattice QCD simulations is observed. Specifically, the lattice QCD calculated interaction measure is well described in our formalism. We have also calculated second-order fluctuations and correlations of conserved charges in K -matrix formalism. We observe a good agreement of second-order fluctuations and baryon-strangeness correlation with lattice data below the crossover temperature.

  3. ORNL neutral gas shielding model for pellet-plasma interactions

    International Nuclear Information System (INIS)

    Milora, S.L; Foster, C.A.

    1977-05-01

    A revised neutral molecule ablation model is derived to describe the evaporation of a solid hydrogen pellet in a tokamak plasma. The approach taken is based on the theory of Parks, Turnbull, and Foster who postulate that a cloud of molecular hydrogen surrounding the pellet shields the surface from incoming energetic electrons and, in so doing, regulates the evaporation rate. This treatment differs from an earlier model in that the hydrodynamic behavior of the molecular cloud is treated in a self-consistent manner. Numerical solutions of the fluid dynamic equations, which include the effects of strong electron heating locally in the gas, reveal that the flow of material away from the pellet is initially retarded by the heating and then rapidly accelerated and rarefied. This behavior is more pronounced for higher temperature plasmas and the net effect is that pellet lifetimes are prolonged slightly by including the heating effects. A comparison is made with the results of the recent pellet injection experiments on ORMAK and a simple injection depth scaling law is derived

  4. Accuracy improvement of the modified EDM model for non-premixed turbulent combustion in gas turbine

    Directory of Open Access Journals (Sweden)

    Qiong Li

    2015-09-01

    Full Text Available Eight bluff body and swirl turbulent diffusion flames resembling the flow field and combustion inside gas turbine combustors are simulated and the simulation results are compared with experimental data. It is revealed that the original modified EDM model could not predict the temperature profile accurately. A more accurate model is developed and validated for gas turbine combustion application. However, this model under predicts the flame temperature for the regular round jet flames indicating that no universal form of the modified EDM model could be achieved for the combustion simulation of both gas furnaces and gas turbines.

  5. Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Shenyang, E-mail: shenyang.hu@pnnl.gov; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie

    2016-10-15

    Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the formation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was developed. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn’t cause the gas bubble alignment, and fast 1-D migration of interstitials along 〈110〉 directions in the body-centered cubic U matrix causes the gas bubble alignment along 〈110〉 directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

  6. Evaluation of gas radiation models in CFD modeling of oxy-combustion

    International Nuclear Information System (INIS)

    Rajhi, M.A.; Ben-Mansour, R.; Habib, M.A.; Nemitallah, M.A.; Andersson, K.

    2014-01-01

    Highlights: • CFD modeling of a typical industrial water tube boiler is conducted. • Different combustion processes were considered including air and oxy-fuel combustion. • SGG, EWBM, Leckner, Perry and WSGG radiation models were considered in the study. • EWBM is the most accurate model and it’s considered to be the benchmark model. • Characteristics of oxy-fuel combustion are compared to those of air–fuel combustion. - Abstract: Proper determination of the radiation energy is very important for proper predictions of the combustion characteristics inside combustion devices using CFD modeling. For this purpose, different gas radiation models were developed and applied in the present work. These radiation models vary in their accuracy and complexity according to the application. In this work, a CFD model for a typical industrial water tube boiler was developed, considering three different combustion environments. The combustion environments are air–fuel combustion (21% O 2 and 79% N 2 ), oxy-fuel combustion (21% O 2 and 79% CO 2 ) and oxy-fuel combustion (27% O 2 and 73% CO 2 ). Simple grey gas (SGG), exponential wide band model (EWBM), Leckner, Perry and weighted sum of grey gases (WSGG) radiation models were examined and their influences on the combustion characteristics were evaluated. Among those radiation models, the EWBM was found to provide close results to the experimental data for the present boiler combustion application. The oxy-fuel combustion characteristics were analyzed and compared with those of air–fuel combustion

  7. Steady-state and transient fission gas release and swelling model for LIFE-4

    International Nuclear Information System (INIS)

    Villalobos, A.; Liu, Y.Y.; Rest, J.

    1984-06-01

    The fuel-pin modeling code LIFE-4 and the mechanistic fission gas behavior model FASTGRASS have been coupled and verified against gas release data from mixed-oxide fuels which were transient tested in the TREAT reactor. Design of the interface between LIFE-4 and FASTGRASS is based on an earlier coupling between an LWR version of LIFE and the GRASS-SST code. Fission gas behavior can significantly affect steady-state and transient fuel performance. FASTGRASS treats fission gas release and swelling in an internally consistent manner and simultaneously includes all major mechanisms thought to influence fission gas behavior. The FASTGRASS steady-state and transient analysis has evolved through comparisons of code predictions with fission-gas release and swelling data from both in- and ex-reactor experiments. FASTGRASS was chosen over other fission-gas behavior models because of its availability, its compatibility with the LIFE-4 calculational framework, and its predictive capability

  8. EVEGAS Project (European validation exercise of GAS migration model)

    Energy Technology Data Exchange (ETDEWEB)

    Manai, T. [Geostock S.A., Rueil-Malmaison (France)

    1995-03-01

    The EVEGAS project aims at the verification and validation of numerical codes suitable for simulating gas flow phenomenon in low permeability porous media. Physical phenomena involved in gas generation and gas flow are numerous, often complex, and may not be very well described. The existing numerical codes cannot represent all the occurring possible phenomena, but allow a good trade-off betwen simplicity and representativity of such phenomena. Two phase flow (Gas and Water) appear to be the most consequential phenomena in gas migration and pressure sizing. The project is organised in three major steps: (1) a simple problem with analytical solutions. (2) A few problems based on laboratory or in-situ experiments. (3) A 3-D repository scenarios involving the following aspects: a repository design; a source of gas; rock characteristics; and fluid characteristics.

  9. Thermodynamic Model for Updraft Gasifier with External Recirculation of Pyrolysis Gas

    Directory of Open Access Journals (Sweden)

    Fajri Vidian

    2016-01-01

    Full Text Available Most of the thermodynamic modeling of gasification for updraft gasifier uses one process of decomposition (decomposition of fuel. In the present study, a thermodynamic model which uses two processes of decomposition (decomposition of fuel and char is used. The model is implemented in modification of updraft gasifier with external recirculation of pyrolysis gas to the combustion zone and the gas flowing out from the side stream (reduction zone in the updraft gasifier. The goal of the model obtains the influences of amount of recirculation pyrolysis gas fraction to combustion zone on combustible gas and tar. The significant results of modification updraft are that the increases amount of recirculation of pyrolysis gas will increase the composition of H2 and reduce the composition of tar; then the composition of CO and CH4 is dependent on equivalence ratio. The results of the model for combustible gas composition are compared with previous study.

  10. Study protocol for a transversal study to develop a screening model for excessive gambling behaviours on a representative sample of users of French authorised gambling websites.

    Science.gov (United States)

    Perrot, Bastien; Hardouin, Jean-Benoit; Costes, Jean-Michel; Caillon, Julie; Grall-Bronnec, Marie; Challet-Bouju, Gaëlle

    2017-05-17

    Since the legalisation of online gambling in France in 2010, gambling operators must implement responsible gambling measures to prevent excessive gambling practices. However, actually there is no screening procedure for identifying problematic gamblers. Although several studies have already been performed using several data sets from online gambling operators, the authors deplored several methodological and clinical limits that prevent scientifically validating the existence of problematic gambling behaviour. The aim of this study is to develop a model for screening excessive gambling practices based on the gambling behaviours observed on French gambling websites, coupled with a clinical validation. The research is divided into three successive stages. All analyses will be performed for each major type of authorised online gambling in France. The first stage aims at defining a typology of users of French authorised gambling websites based on their gambling behaviour. This analysis will be based on data from the Authority for Regulating Online Gambling (ARJEL) and the Française Des Jeux (FDJ). For the second stage aiming at determining a score to predict whether a gambler is problematic or not, we will cross answers from the Canadian Problem Gambling Index with real gambling data. The objective of the third stage is to clinically validate the score previously developed. Results from the screening model will be compared (using sensitivity, specificity, area under the curve, and positive and negative predictive values) with the diagnosis obtained with a telephone clinical interview, including diagnostic criteria for gambling addiction. This study was approved by the local Research Ethics Committee (GNEDS) on 25 March 2015. Results will be presented in national and international conferences, submitted to peer-reviewed journals and will be part of a PhD thesis. A final report with the study results will be presented to the ARJEL, especially the final screening model

  11. Mathematical modeling of non-stationary gas flow in gas pipeline

    Science.gov (United States)

    Fetisov, V. G.; Nikolaev, A. K.; Lykov, Y. V.; Duchnevich, L. N.

    2018-03-01

    An analysis of the operation of the gas transportation system shows that for a considerable part of time pipelines operate in an unsettled regime of gas movement. Its pressure and flow rate vary along the length of pipeline and over time as a result of uneven consumption and selection, switching on and off compressor units, shutting off stop valves, emergence of emergency leaks. The operational management of such regimes is associated with difficulty of reconciling the operating modes of individual sections of gas pipeline with each other, as well as with compressor stations. Determining the grounds that cause change in the operating mode of the pipeline system and revealing patterns of these changes determine the choice of its parameters. Therefore, knowledge of the laws of changing the main technological parameters of gas pumping through pipelines in conditions of non-stationary motion is of great importance for practice.

  12. Developments in the US gas industry - no model for Europe

    Energy Technology Data Exchange (ETDEWEB)

    Maier, F H

    1988-09-01

    The deregulation measures in the USA have led to increased regulation in the gas industry. There is no reason why these measures should be adopted in Europe. After a few remarks on the beginning of state regulation in the USA gas industry, the article goes on to consider the consequences of this policy (supply bottlenecks as a result of cost-oriented regulation of gas prices, surplus supply as a result of regulation-induced price increases).

  13. Leakage detection of Marcellus Shale natural gas at an Upper Devonian gas monitoring well: a 3-d numerical modeling approach.

    Science.gov (United States)

    Zhang, Liwei; Anderson, Nicole; Dilmore, Robert; Soeder, Daniel J; Bromhal, Grant

    2014-09-16

    Potential natural gas leakage into shallow, overlying formations and aquifers from Marcellus Shale gas drilling operations is a public concern. However, before natural gas could reach underground sources of drinking water (USDW), it must pass through several geologic formations. Tracer and pressure monitoring in formations overlying the Marcellus could help detect natural gas leakage at hydraulic fracturing sites before it reaches USDW. In this study, a numerical simulation code (TOUGH 2) was used to investigate the potential for detecting leaking natural gas in such an overlying geologic formation. The modeled zone was based on a gas field in Greene County, Pennsylvania, undergoing production activities. The model assumed, hypothetically, that methane (CH4), the primary component of natural gas, with some tracer, was leaking around an existing well between the Marcellus Shale and the shallower and lower-pressure Bradford Formation. The leaky well was located 170 m away from a monitoring well, in the Bradford Formation. A simulation study was performed to determine how quickly the tracer monitoring could detect a leak of a known size. Using some typical parameters for the Bradford Formation, model results showed that a detectable tracer volume fraction of 2.0 × 10(-15) would be noted at the monitoring well in 9.8 years. The most rapid detection of tracer for the leak rates simulated was 81 days, but this scenario required that the leakage release point was at the same depth as the perforation zone of the monitoring well and the zones above and below the perforation zone had low permeability, which created a preferred tracer migration pathway along the perforation zone. Sensitivity analysis indicated that the time needed to detect CH4 leakage at the monitoring well was very sensitive to changes in the thickness of the high-permeability zone, CH4 leaking rate, and production rate of the monitoring well.

  14. An evaluation of gas release modelling approaches as to their applicability in fuel behaviour models

    International Nuclear Information System (INIS)

    Mattila, L.J.; Sairanen, R.T.

    1980-01-01

    The release of fission gas from uranium oxide fuel to the voids in the fuel rod affects in many ways the behaviour of LWR fuel rods both during normal operating conditions including anticipated transients and during off-normal and accident conditions. The current trend towards significantly increased discharge burnup of LWR fuel will increase the importance of fission gas release considerations both from the design and safety viewpoints. In the paper fission gas release models are classified to 5 categories on the basis of complexity and physical sophistication. For each category, the basic approach common to the models included in the category is described, a few representative models of the category are singled out and briefly commented in some cases, the advantages and drawbacks of the approach are listed and discussed and conclusions on the practical feasibility of the approach are drawn. The evaluation is based on both literature survey and our experience in working with integral fuel behaviour models. The work has included verification efforts, attempts to improve certain features of the codes and engineering applications. The classification of fission gas release models regarding their applicability in fuel behaviour codes can of course be done only in a coarse manner. The boundaries between the different categories are vague and a model may be well refined in a way which transfers it to a higher category. Some current trends in fuel behaviour research are discussed which seem to motivate further extensive efforts in fission product release modelling and are certain to affect the prioritizing of the efforts. (author)

  15. A probit- log- skew-normal mixture model for repeated measures data with excess zeros, with application to a cohort study of paediatric respiratory symptoms

    Directory of Open Access Journals (Sweden)

    Johnston Neil W

    2010-06-01

    Full Text Available Abstract Background A zero-inflated continuous outcome is characterized by occurrence of "excess" zeros that more than a single distribution can explain, with the positive observations forming a skewed distribution. Mixture models are employed for regression analysis of zero-inflated data. Moreover, for repeated measures zero-inflated data the clustering structure should also be modeled for an adequate analysis. Methods Diary of Asthma and Viral Infections Study (DAVIS was a one year (2004 cohort study conducted at McMaster University to monitor viral infection and respiratory symptoms in children aged 5-11 years with and without asthma. Respiratory symptoms were recorded daily using either an Internet or paper-based diary. Changes in symptoms were assessed by study staff and led to collection of nasal fluid specimens for virological testing. The study objectives included investigating the response of respiratory symptoms to respiratory viral infection in children with and without asthma over a one year period. Due to sparse data daily respiratory symptom scores were aggregated into weekly average scores. More than 70% of the weekly average scores were zero, with the positive scores forming a skewed distribution. We propose a random effects probit/log-skew-normal mixture model to analyze the DAVIS data. The model parameters were estimated using a maximum marginal likelihood approach. A simulation study was conducted to assess the performance of the proposed mixture model if the underlying distribution of the positive response is different from log-skew normal. Results Viral infection status was highly significant in both probit and log-skew normal model components respectively. The probability of being symptom free was much lower for the week a child was viral positive relative to the week she/he was viral negative. The severity of the symptoms was also greater for the week a child was viral positive. The probability of being symptom free was

  16. Shale gas technology innovation rate impact on economic Base Case – Scenario model benchmarks

    International Nuclear Information System (INIS)

    Weijermars, Ruud

    2015-01-01

    Highlights: • Cash flow models control which technology is affordable in emerging shale gas plays. • Impact of technology innovation on IRR can be as important as wellhead price hikes. • Cash flow models are useful for technology decisions that make shale gas plays economic. • The economic gap can be closed by appropriate technology innovation. - Abstract: Low gas wellhead prices in North America have put its shale gas industry under high competitive pressure. Rapid technology innovation can help companies to improve the economic performance of shale gas fields. Cash flow models are paramount for setting effective production and technology innovation targets to achieve positive returns on investment in all global shale gas plays. Future cash flow of a well (or cluster of wells) may either improve further or deteriorate, depending on: (1) the regional volatility in gas prices at the wellhead – which must pay for the gas resource extraction, and (2) the cost and effectiveness of the well technology used. Gas price is an externality and cannot be controlled by individual companies, but well technology cost can be reduced while improving production output. We assume two plausible scenarios for well technology innovation and model the return on investment while checking against sensitivity to gas price volatility. It appears well technology innovation – if paced fast enough – can fully redeem the negative impact of gas price decline on shale well profits, and the required rates are quantified in our sensitivity analysis

  17. Modeling syngas-fired gas turbine engines with two dilutants

    Science.gov (United States)

    Hawk, Mitchell E.

    2011-12-01

    Prior gas turbine engine modeling work at the University of Wyoming studied cycle performance and turbine design with air and CO2-diluted GTE cycles fired with methane and syngas fuels. Two of the cycles examined were unconventional and innovative. The work presented herein reexamines prior results and expands the modeling by including the impacts of turbine cooling and CO2 sequestration on GTE cycle performance. The simple, conventional regeneration and two alternative regeneration cycle configurations were examined. In contrast to air dilution, CO2 -diluted cycle efficiencies increased by approximately 1.0 percentage point for the three regeneration configurations examined, while the efficiency of the CO2-diluted simple cycle decreased by approximately 5.0 percentage points. For CO2-diluted cycles with a closed-exhaust recycling path, an optimum CO2-recycle pressure was determined for each configuration that was significantly lower than atmospheric pressure. Un-cooled alternative regeneration configurations with CO2 recycling achieved efficiencies near 50%, which was approximately 3.0 percentage points higher than the conventional regeneration cycle and simple cycle configurations that utilized CO2 recycling. Accounting for cooling of the first two turbine stages resulted in a 2--3 percentage point reduction in un-cooled efficiency, with air dilution corresponding to the upper extreme. Additionally, when the work required to sequester CO2 was accounted for, cooled cycle efficiency decreased by 4--6 percentage points, and was more negatively impacted when syngas fuels were used. Finally, turbine design models showed that turbine blades are shorter with CO2 dilution, resulting in fewer design restrictions.

  18. Carbon dioxide corrosion: Modelling and experimental work applied to natural gas pipelines

    Energy Technology Data Exchange (ETDEWEB)

    P, Loldrup Fosboel

    2007-10-15

    CO{sub 2} corrosion is a general problem in the industry and it is expensive. The focus of this study is an oil gas production related problem. CO{sub 2} corrosion is observed in offshore natural gas transportation pipelines. A general overview of the problem is presented in chapter 1. The chemical system consists mainly of CO{sub 2}-Na{sub 2}CO{sub 3}-NaHCO{sub 3}-MEG-H{sub 2}O. Sodium is injected in the pipelines as NaOH in order to pH-stabilize the pipeline to avoid corrosion and MEG is injected in order to prevent gas hydrates. There are a great number of models available in the literature which may predict CO{sub 2} corrosion. These models are not very accurate and assume ideality in the main part of the equation. This thesis deals with aspect of improving the models to account for the non-ideality. A general overview and extension of the theory behind electrochemical corrosion is presented in chapter 2 to 4. The theory deals with the basic thermodynamics of electrolytes in chapter 2, the extension and general description of electrolyte mass transport in chapter 3, and the electrochemical kinetics of corrosion in chapter 4. A literature overview of CO{sub 2} corrosion is shown in chapter 5 and possible extensions of the models are discussed. A list of literature cites is given in chapter 6. The literature review in chapter 5 shows how FeCO{sub 3} plays a main part in the protection of steel. Especially the solubility of FeCO{sub 3} is an important factor. Chapter 7 discusses and validates the thermodynamic properties of FeCO{sub 3}. The study shows that there is a discrepancy in the properties of FeCO{sub 3}. Sets of consistent thermodynamic properties of FeCO{sub 3} are given. A mixed solvent electrolyte model is regressed in chapter 8 for the CO{sub 2}-Na{sub 2}CO{sub 3}-NaHCO{sub 3}-MEG-H{sub 2}O system. Parameters of the extended UNIQUAC model is fitted to literature data of VLE, SLE, heat excess and validated against heat capacity data. The model is also

  19. Rarefied gas flow simulations using high-order gas-kinetic unified algorithms for Boltzmann model equations

    Science.gov (United States)

    Li, Zhi-Hui; Peng, Ao-Ping; Zhang, Han-Xin; Yang, Jaw-Yen

    2015-04-01

    This article reviews rarefied gas flow computations based on nonlinear model Boltzmann equations using deterministic high-order gas-kinetic unified algorithms (GKUA) in phase space. The nonlinear Boltzmann model equations considered include the BGK model, the Shakhov model, the Ellipsoidal Statistical model and the Morse model. Several high-order gas-kinetic unified algorithms, which combine the discrete velocity ordinate method in velocity space and the compact high-order finite-difference schemes in physical space, are developed. The parallel strategies implemented with the accompanying algorithms are of equal importance. Accurate computations of rarefied gas flow problems using various kinetic models over wide ranges of Mach numbers 1.2-20 and Knudsen numbers 0.0001-5 are reported. The effects of different high resolution schemes on the flow resolution under the same discrete velocity ordinate method are studied. A conservative discrete velocity ordinate method to ensure the kinetic compatibility condition is also implemented. The present algorithms are tested for the one-dimensional unsteady shock-tube problems with various Knudsen numbers, the steady normal shock wave structures for different Mach numbers, the two-dimensional flows past a circular cylinder and a NACA 0012 airfoil to verify the present methodology and to simulate gas transport phenomena covering various flow regimes. Illustrations of large scale parallel computations of three-dimensional hypersonic rarefied flows over the reusable sphere-cone satellite and the re-entry spacecraft using almost the largest computer systems available in China are also reported. The present computed results are compared with the theoretical prediction from gas dynamics, related DSMC results, slip N-S solutions and experimental data, and good agreement can be found. The numerical experience indicates that although the direct model Boltzmann equation solver in phase space can be computationally expensive

  20. Advanced Gas Hydrate Reservoir Modeling Using Rock Physics

    Energy Technology Data Exchange (ETDEWEB)

    McConnell, Daniel

    2017-12-30

    Prospecting for high saturation gas hydrate deposits can be greatly aided with improved approaches to seismic interpretation and especially if sets of seismic attributes can be shown as diagnostic or direct hydrocarbon indicators for high saturation gas hydrates in sands that would be of most interest for gas hydrate production.

    A large 3D seismic data set in the deep water Eastern Gulf of Mexico was screened for gas hydrates using a set of techniques and seismic signatures that were developed and proven in the Central deepwater Gulf of Mexico in the DOE Gulf of Mexico Joint Industry Project JIP Leg II in 2009 and recently confirmed with coring in 2017.

    A large gas hydrate deposit is interpreted in the data where gas has migrated from one of the few deep seated faults plumbing the Jurassic hydrocarbon source into the gas hydrate stability zone. The gas hydrate deposit lies within a flat-lying within Pliocene Mississippi Fan channel that was deposited outboard in a deep abyssal environment. The uniform architecture of the channel aided the evaluation of a set of seismic attributes that relate to attenuation and thin-bed energy that could be diagnostic of gas hydrates. Frequency attributes derived from spectral decomposition also proved to be direct hydrocarbon indicators by pseudo-thickness that could be only be reconciled by substituting gas hydrate in the pore space. The study emphasizes that gas hydrate exploration and reservoir characterization benefits from a seismic thin bed approach.

  1. Version 2.0 of the European Gas Model. Changes and their impact on the German gas sector; Das europaeische Gas Target Model 2.0. Aenderungen und Auswirkungen auf den deutschen Gassektor

    Energy Technology Data Exchange (ETDEWEB)

    Balmert, David; Petrov, Konstantin [DNV GL, Bonn (Germany)

    2015-06-15

    In January 2015 ACER, the European Agency for the Cooperation of Energy Regulators, presented an updated version of its target model for the inner-European natural gas market, also referred to as version 2.0 of the Gas Target Model. During 2014 the existing model, originally developed by the Council of European Energy Regulators (CEER) and launched in 2011, had been analysed, revised and updated in preparation of the new version. While it has few surprises to offer, the new Gas Target Model contains specifies and goes into greater detail on many elements of the original model. Some of the new content is highly relevant to the German gas sector, not least the deliberations on the current key issues, which are security of supply and the ability of the gas markets to function.

  2. Experimental and modelling study of reverse flow catalytic converters for natural gas/diesel dual fuel engine pollution control

    Energy Technology Data Exchange (ETDEWEB)

    Liu, B.

    2000-07-01

    There is renewed interest in the development of natural gas vehicles in response to the challenge to reduce urban air pollution and consumption of petroleum. The natural gas/diesel dual fuel engine is one way to apply natural gas to the conventional diesel engine. Dual fuel engines operating on natural gas and diesel emit less nitrogen oxides, and less carbon soot to the air compared to conventional diesel engines. The problem is that at light loads, fuel efficiency is reduced and emissions of hydrocarbons and carbon monoxide are increased. This thesis focused on control methods for emissions of hydrocarbons and carbon monoxide in the dual fuel engine at light loads. This was done by developing a reverse flow catalytic converter to complement dual fuel engine exhaust characteristics. Experimental measurements and numerical simulations of reverse flow catalytic converters were conducted. Reverse flow creates a high reactor temperature even when the engine is run at low exhaust temperature levels at light loads. The increase in reactor temperature from reverse flow could be 2 or 3 times higher than the adiabatic temperature increase, which is based on the reactor inlet temperature and concentration. This temperature makes it possible for greater than 90 per cent of the hydrocarbon and carbon monoxide to be converted with a palladium based catalyst. Reverse flow appears to be better than conventional unidirectional flow to deal with natural gas/diesel dual fuel engine pollution at light loads. Reverse flow could also maintain reactor temperature at over 800 K and hydrocarbon conversion at about 80 per cent during testing. The newly presented model simulates reactor performance with reasonable accuracy. Both carbon monoxide and methane oxidation over the palladium catalyst in excess oxygen and water were described using first order kinetics.

  3. Excessive crying in infants

    Directory of Open Access Journals (Sweden)

    Ricardo Halpern

    2016-05-01

    Conclusion: Excessive crying in the early months is a prevalent symptom; the pediatrician's attention is necessary to understand and adequately manage the problem and offer support to exhausted parents. The prescription of drugs of questionable action and with potential side effects is not a recommended treatment, except in extreme situations. The effectiveness of dietary treatments and use of probiotics still require confirmation. There is incomplete evidence regarding alternative treatments such as manipulation techniques, acupuncture, and use of the herbal supplements and behavioral interventions.

  4. The Fermi-LAT gamma-ray excess at the Galactic Center in the singlet-doublet fermion dark matter model

    Energy Technology Data Exchange (ETDEWEB)

    Horiuchi, Shunsaku; Macias, Oscar [Center for Neutrino Physics, Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Restrepo, Diego; Rivera, Andrés; Zapata, Oscar [Instituto de Física, Universidad de Antioquia, Calle 70 No. 52-21, Medellín (Colombia); Silverwood, Hamish, E-mail: horiuchi@vt.edu, E-mail: oscar.macias@vt.edu, E-mail: restrepo@udea.edu.co, E-mail: afelipe.rivera@udea.edu.co, E-mail: oalberto.zapata@udea.edu.co, E-mail: h.g.m.silverwood@uva.nl [GRAPPA, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands)

    2016-03-01

    The singlet-doublet fermion dark matter model (SDFDM) provides a good DM candidate as well as the possibility of generating neutrino masses radiatively. The search and identification of DM requires the combined effort of both indirect and direct DM detection experiments in addition to the LHC. Remarkably, an excess of GeV gamma rays from the Galactic Center (GCE) has been measured with the Fermi Large Area Telescope (LAT) which appears to be robust with respect to changes in the diffuse galactic background modeling. Although several astrophysical explanations have been proposed, DM remains a simple and well motivated alternative. In this work, we examine the sensitivities of dark matter searches in the SDFDM scenario using Fermi-LAT, CTA, IceCube/DeepCore, LUX, PICO and LHC with an emphasis on exploring the regions of the parameter space that can account for the GCE. We find that DM particles present in this model with masses close to ∼ 99 GeV and ∼ (173–190) GeV annihilating predominantly into the W{sup +}W{sup −} channel and t t-bar channel respectively, provide an acceptable fit to the GCE while being consistent with different current experimental bounds. We also find that much of the obtained parameter space can be ruled out by future direct search experiments like LZ and XENON-1T, in case of null results by these detectors. Interestingly, we show that the most recent data by LUX is starting to probe the best fit region in the SDFDM model.

  5. A sequential Monte Carlo model of the combined GB gas and electricity network

    International Nuclear Information System (INIS)

    Chaudry, Modassar; Wu, Jianzhong; Jenkins, Nick

    2013-01-01

    A Monte Carlo model of the combined GB gas and electricity network was developed to determine the reliability of the energy infrastructure. The model integrates the gas and electricity network into a single sequential Monte Carlo simulation. The model minimises the combined costs of the gas and electricity network, these include gas supplies, gas storage operation and electricity generation. The Monte Carlo model calculates reliability indices such as loss of load probability and expected energy unserved for the combined gas and electricity network. The intention of this tool is to facilitate reliability analysis of integrated energy systems. Applications of this tool are demonstrated through a case study that quantifies the impact on the reliability of the GB gas and electricity network given uncertainties such as wind variability, gas supply availability and outages to energy infrastructure assets. Analysis is performed over a typical midwinter week on a hypothesised GB gas and electricity network in 2020 that meets European renewable energy targets. The efficacy of doubling GB gas storage capacity on the reliability of the energy system is assessed. The results highlight the value of greater gas storage facilities in enhancing the reliability of the GB energy system given various energy uncertainties. -- Highlights: •A Monte Carlo model of the combined GB gas and electricity network was developed. •Reliability indices are calculated for the combined GB gas and electricity system. •The efficacy of doubling GB gas storage capacity on reliability of the energy system is assessed. •Integrated reliability indices could be used to assess the impact of investment in energy assets

  6. A Computation Fluid Dynamic Model for Gas Lift Process Simulation in a Vertical Oil Well

    Directory of Open Access Journals (Sweden)

    Kadivar Arash

    2017-03-01

    Full Text Available Continuous gas-lift in a typical oil well was simulated using computational fluid dynamic (CFD technique. A multi fluid model based on the momentum transfer between liquid and gas bubbles was employed to simulate two-phase flow in a vertical pipe. The accuracy of the model was investigated through comparison of numerical predictions with experimental data. The model then was used to study the dynamic behaviour of the two-phase flow around injection point in details. The predictions by the model were compared with other empirical correlations, as well. To obtain an optimum condition of gas-lift, the influence of the effective parameters including the quantity of injected gas, tubing diameter and bubble size distribution were investigated. The results revealed that increasing tubing diameter, the injected gas rate and decreasing bubble diameter improve gas-lift performance.

  7. A model of gas cavity breakup behind a blockage in fast breeder reactor subassembly geometry

    International Nuclear Information System (INIS)

    Fukuzawa, Y.

    1980-05-01

    A semi-empirical model has been developed to describe the transient behaviour of a gas cavity due to breakup behind a blockage in Liquid Metal Fast Breeder Reactor subassembly geometry. The main mechanisms assumed for gas cavity breakup in the present model are as follows: The gas cavity is broken up by the pressure fluctuation at the interface due to turbulence in the liquid. The centrifugal force on the liquid opposes breakup. The model is able to describe experimental results on the transient behaviour of a gas cavity due to breakup after the termination of gas injection. On the basis of the present model the residence time of a gas cavity behind a blockage in sodium is predicted and the dependence of the residence time on blockage size is discussed. (orig.) [de

  8. A new mechanistic and engineering fission gas release model for a uranium dioxide fuel

    International Nuclear Information System (INIS)

    Lee, Chan Bock; Yang, Yong Sik; Kim, Dae Ho; Kim, Sun Ki; Bang, Je Geun

    2008-01-01

    A mechanistic and engineering fission gas release model (MEGA) for uranium dioxide (UO 2 ) fuel was developed. It was based upon the diffusional release of fission gases from inside the grain to the grain boundary and the release of fission gases from the grain boundary to the external surface by the interconnection of the fission gas bubbles in the grain boundary. The capability of the MEGA model was validated by a comparison with the fission gas release data base and the sensitivity analyses of the parameters. It was found that the MEGA model correctly predicts the fission gas release in the broad range of fuel burnups up to 98 MWd/kgU. Especially, the enhancement of fission gas release in a high-burnup fuel, and the reduction of fission gas release at a high burnup by increasing the UO 2 grain size were found to be correctly predicted by the MEGA model without using any artificial factor. (author)

  9. Modeling Coma Gas Jets in Comet Hale-Bopp

    Science.gov (United States)

    Lederer, S. M.; Campins, H.

    2001-01-01

    We present an analysis of OH, CN, and C2 jets observed in Comet Hale-Bopp. The relative contributions from and composition of the coma gas sources, and the parameters describing the active areas responsible for the gas jets will be discussed. Additional information is contained in the original extended abstract.

  10. Defect trap model of gas behaviour in UO2 fuel during irradiation

    International Nuclear Information System (INIS)

    Szuta, A.

    2003-01-01

    Fission gas behaviour is one of the central concern in the fuel design, performance and hypothetical accident analysis. The report 'Defect trap model of gas behaviour in UO 2 fuel during irradiation' is the worldwide literature review of problems studied, experimental results and solutions proposed in related topics. Some of them were described in details in the report chapters. They are: anomalies in the experimental results; fission gas retention in the UO 2 fuel; microstructure of the UO 2 fuel after irradiation; fission gas release models; defect trap model of fission gas behaviour; fission gas release from UO 2 single crystal during low temperature irradiation in terms of a defect trap model; analysis of dynamic release of fission gases from single crystal UO 2 during low temperature irradiation in terms of defect trap model; behaviour of fission gas products in single crystal UO 2 during intermediate temperature irradiation in terms of a defect trap model; modification of re-crystallization temperature of UO 2 in function of burnup and its impact on fission gas release; apparent diffusion coefficient; formation of nanostructures in UO 2 fuel at high burnup; applications of the defect trap model to the gas leaking fuel elements number assessment in the nuclear power station (VVER-PWR)

  11. ACTIVATION PARAMETERS AND EXCESS THERMODYANAMIC ...

    African Journals Online (AJOL)

    Applying these data, viscosity-B-coefficients, activation parameters (Δμ10≠) and (Δμ20≠) and excess thermodynamic functions, viz., excess molar volume (VE), excess viscosity, ηE and excess molar free energy of activation of flow, (GE) were calculated. The value of interaction parameter, d, of Grunberg and Nissan ...

  12. Simulation and Modeling of Flow in a Gas Compressor

    Directory of Open Access Journals (Sweden)

    Anna Avramenko

    2015-01-01

    Full Text Available The presented research demonstrates the results of a series of numerical simulations of gas flow through a single-stage centrifugal compressor with a vaneless diffuser. Numerical results were validated with experiments consisting of eight regimes with different mass flow rates. The steady-state and unsteady simulations were done in ANSYS FLUENT 13.0 and NUMECA FINE/TURBO 8.9.1 for one-period geometry due to periodicity of the problem. First-order discretization is insufficient due to strong dissipation effects. Results obtained with second-order discretization agree with the experiments for the steady-state case in the region of high mass flow rates. In the area of low mass flow rates, nonstationary effects significantly influence the flow leading stationary model to poor prediction. Therefore, the unsteady simulations were performed in the region of low mass flow rates. Results of calculation were compared with experimental data. The numerical simulation method in this paper can be used to predict compressor performance.

  13. The practical use of resistance modelling to interpret the gas separation properties of hollow fiber membranes

    International Nuclear Information System (INIS)

    Ahmad Fauzi Ismail; Shilton, S.J.

    2000-01-01

    A simple resistance modelling methodology is presented for gas transport through asymmetric polymeric membranes. The methodology allows fine structural properties such as active layer thickness and surface porosity, to be determined from experimental gas permeation data. This paper, which could be regarded as a practical guide, shows that resistance modeling, if accompanied by realistic working assumptions, need not be difficult and can provide a valuable insight into the relationships between the membrane fabrication conditions and performance of gas separation membranes. (Author)

  14. A mathematical framework for modelling and evaluating natural gas pipeline networks under hydrogen injection

    Energy Technology Data Exchange (ETDEWEB)

    Tabkhi, F.; Azzaro-Pantel, C.; Pibouleau, L.; Domenech, S. [Laboratoire de Genie Chimique, UMR5503 CNRS/INP/UPS, 5 rue Paulin Talabot F-BP1301, 31106 Toulouse Cedex 1 (France)

    2008-11-15

    This article presents the framework of a mathematical formulation for modelling and evaluating natural gas pipeline networks under hydrogen injection. The model development is based on gas transport through pipelines and compressors which compensate for the pressure drops by implying mainly the mass and energy balances on the basic elements of the network. The model was initially implemented for natural gas transport and the principle of extension for hydrogen-natural gas mixtures is presented. The objective is the treatment of the classical fuel minimizing problem in compressor stations. The optimization procedure has been formulated by means of a nonlinear technique within the General Algebraic Modelling System (GAMS) environment. This work deals with the adaptation of the current transmission networks of natural gas to the transport of hydrogen-natural gas mixtures. More precisely, the quantitative amount of hydrogen that can be added to natural gas can be determined. The studied pipeline network, initially proposed in [1] is revisited here for the case of hydrogen-natural gas mixtures. Typical quantitative results are presented, showing that the addition of hydrogen to natural gas decreases significantly the transmitted power: the maximum fraction of hydrogen that can be added to natural gas is around 6 mass% for this example. (author)

  15. Escalation scenarios initiated by gas explosions on offshore installations. Probabilistic cause and consequence modelling

    Energy Technology Data Exchange (ETDEWEB)

    Eknes, Monika Loeland

    1996-12-31

    This Dr. ing. thesis deals with escalation scenarios initiated by gas explosions on offshore installations. Gas explosions is one of the major hazards to such installations. The objectives were to estimate the probability of ignition and frequency of gas explosions for gas leaks on top sides of offshore installations, and to estimate the response and resistance of components that could result in escalation if they failed. Main fields considered cover risk analysis methodology, gas explosions, simplified escalation models, evaluation of structural consequences, case studies, and guidelines. 107 refs., 33 figs., 33 tabs.

  16. Cognitive-motivational model of obesity. Motivational mechanisms and cognitive biases underlying the processing of food-related images by people with excess body weight.

    Science.gov (United States)

    Pawłowska, Monika; Kalka, Dorota

    2015-01-01

    Obesity is a constantly escalating problem in all age groups. In the face of ubiquitous images of food, colourful advertisements of high-calorie meals and beverages, it is necessary to examine the role of the memory and attention mechanism in the processing of these stimuli. Knowledge regarding this subject will surely significantly contribute to the improvement of prevention and management of obesity programs designed to prevent secondary psychological difficulties, including depression. This paper presents cognitive-motivational model of obesity, according to which the description of mechanisms of eating disorders occurrence should include not only motivational factors but also the cognitive ones. The paper shows theoretical perspectives on the problem of obesity irrespective of its origin, as well as the latest empirical reports in this field. The presented survey demonstrates the lack of explicit research findings related to the processing of high and low-calorie food images by persons with excess weight. It seems that the knowledge of the basic mechanisms involved in the processing of these stimuli and the exploration of this phenomenon will allow to improve programs whose objective is to prevent obesity.

  17. 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

  18. Comparison Of Four Landfill Gas Models Using Data From Four Danish Landfills

    DEFF Research Database (Denmark)

    Mønster, Jacob G.; Mou, Zishen; Kjeldsen, Peter

    2011-01-01

    Data about type and quantity of waste disposed in four Danish landfills was collected and used on four different landfill gas generation models. This was done to compare the output data in order to evaluate the performance of the four landfill gas models when used on Danish waste types...

  19. Modelling gas migration in compacted bentonite: gambit club phase 3. Final report

    International Nuclear Information System (INIS)

    Hoch, A.R.; Cliffe, K.A.; Swift, B.T.; Rodwell, W.R.

    2004-04-01

    This report describes the third phase of a programme of work to develop a computational model of gas migration through highly compacted water-saturated bentonite. One difficulty with this endeavour is the definitive determination of the mechanism of the gas migration from the available experimental data. The report contains a brief review of the experimental data and their interpretation. The model development work reported involves the investigation of two ways of enhancing a model proposed in the previous phase of the programme. This model was based on the concept that gas migration pathways were created by consolidating the clay fabric by application of gas pressure to create porosity through which the gas could flow. The two developments of this model that are separately explored in this work are: (a) The incorporation of a proper treatment of the stress-strain behaviour of the clay in (b) response to gas migration. The previous model had only considered stress effects through simple volume changes to the clay fabric. The inclusion of a dual-porosity feature into the model in an attempt to address the role that the clay fabric might play in gas migration through the clay, in particular the role that pre-existing interstack voids might have in gas migration. The consideration of hysteresis effects was also included in this study. As in previous GAMBIT Club work, the models are tested against the results of laboratory experiments. (orig.)

  20. An optimization model for natural gas supply portfolios of a power generation company

    International Nuclear Information System (INIS)

    Jirutitijaroen, Panida; Kim, Sujin; Kittithreerapronchai, Oran; Prina, José

    2013-01-01

    Highlights: ► An optimization model for daily operation of a natural gas-fired generation company is proposed. ► The model considers uncertainties in electricity price and natural gas price. ► The model is formulated to capture the hedging decisions by the company. ► The solution yields quantities of natural gas, generating schedule and purchasing quantities of electricity. ► Higher profit can be achieved by adapting inventory and production to the actual spot prices of natural gas and electricity. - Abstract: This paper considers a deregulated electricity market environment where a natural gas-fired generation company can engage in different types of contracts to manage its natural gas supply as well as trade on the electricity market. If the contracts are properly designed, they can protect the company from fluctuations in electricity price and demand, at some cost to the company’s expected profit. This reduction in profit can be mitigated by trading on the natural gas and electricity spot markets, but this trading activity may also sometimes result in losses. A stochastic programming model is formulated to capture the hedging decisions made by the company, as well as the interactions between the natural gas and electricity markets. The benefits offered by this approach for profit maximization in a variety of business scenarios, such as the case where the company can hold some amount of gas in storage are studied and presented. It is found that the stochastic model enables the company to optimize the electricity generation schedule and the natural gas consumption, including spot price transactions and gas storage management. Several managerial insights into the natural gas market, natural gas storage, and distribution profit are given

  1. Gas generation in deep radioactive waste repositories: a review of processes, controls and models

    International Nuclear Information System (INIS)

    Jones, M.A.

    1990-10-01

    Gas generation within radioactive waste repositories may produce two general problems: 1) breaching of engineered and natural barriers due to high gas pressures; 2) enhanced radiological risk due to reduced groundwater travel times and/or greater aqueous or gaseous activities reaching the biosphere. As a result of these concerns, HMIP must be aware of the current status of relevant research, together with any associated deficiencies. This report addresses the current status of published research on near-field gas generation from worldwide sources and documents the important gas generating processes, the factors controlling them and models available to simulate them. In the absence of suitable models, outline technical specifications for corrosion and microbial degradation gas generation models are defined and the deficiencies in the current understanding of gas generation are highlighted; a conceptual research programme to correct these deficiencies is presented. (author)

  2. Multiscale development of a fission gas thermal conductivity model: Coupling atomic, meso and continuum level simulations

    International Nuclear Information System (INIS)

    Tonks, Michael R.; Millett, Paul C.; Nerikar, Pankaj; Du, Shiyu; Andersson, David; Stanek, Christopher R.; Gaston, Derek; Andrs, David; Williamson, Richard

    2013-01-01

    Fission gas production and evolution significantly impact the fuel performance, causing swelling, a reduction in the thermal conductivity and fission gas release. However, typical empirical models of fuel properties treat each of these effects separately and uncoupled. Here, we couple a fission gas release model to a model of the impact of fission gas on the fuel thermal conductivity. To quantify the specific impact of grain boundary (GB) bubbles on the thermal conductivity, we use atomistic and mesoscale simulations. Atomistic molecular dynamic simulations were employed to determine the GB thermal resistance. These values were then used in mesoscale heat conduction simulations to develop a mechanistic expression for the effective GB thermal resistance of a GB containing gas bubbles, as a function of the percentage of the GB covered by fission gas. The coupled fission gas release and thermal conductivity model was implemented in Idaho National Laboratory’s BISON fuel performance code to model the behavior of a 10-pellet LWR fuel rodlet, showing how the fission gas impacts the UO 2 thermal conductivity. Furthermore, additional BISON simulations were conducted to demonstrate the impact of average grain size on both the fuel thermal conductivity and the fission gas release

  3. Demand for seasonal gas storage in northwest Europe until 2030. Simulation results with a dynamic model

    International Nuclear Information System (INIS)

    De Joode, J.; Oezdemir, Oe.

    2010-01-01

    The fact that depletion of indigenous gas production increases gas import dependency is widely known and accepted. However, there is considerable less attention for the implications of indigenous resource depletion for the provision of seasonal flexibility. The traditionally largest source of seasonal flexibility in Europe is indigenous gas production, mainly based in the Netherlands and the United Kingdom. With the depletion of indigenous sources the market increasingly needs to rely on other sources for seasonal flexibility, such as gas storage facilities. We investigate the future need for gas storage as a source for seasonal flexibility provision using a dynamic gas market model (GASTALE) in which different potential sources for seasonal flexibility - gas production, imports via pipeline, LNG imports and storage facilities - compete with each other in a market-based environment. The inclusion of seasonal flexibility properties in a gas market model allows a more complex analysis of seasonal flexibility issues than previously documented in literature. This is demonstrated in an analysis of the future demand for gas storage in northwestern Europe until 2030. Our results indicate that there is substantial need for additional gas storage facilities and thus supports current project proposals for new investment in gas storage facilities. (author)

  4. Conductivity modeling of gas sensors based on copper ...

    African Journals Online (AJOL)

    The main objective of this work is to study the electronic conductivity of copper ... applications, such as gas sensors [11 - 13], catalysts [14], solar cells [15], .... solid systems and adopted to examine the mechanism of the adsorption process [38].

  5. New Fokker-Planck derivation of heavy gas models for neutron thermalization

    International Nuclear Information System (INIS)

    Larsen, E.W.; Williams, M.M.R.

    1990-01-01

    This paper is concerned with the derivation of new generalized heavy gas models for the infinite medium neutron energy spectrum equation. Our approach is general and can be used to derive improved Fokker-Planck approximations for other types of kinetic equations. In this paper we obtain two distinct heavy gas models, together with estimates for the corresponding errors. The models are shown in a special case to reduce to modified heavy gas models proposed earlier by Corngold (1962). The error estimates show that both of the new models should be more accurate than Corngold's modified heavy gas model, and that the first of the two new models should generally be more accurate than the second. (author)

  6. Fast and accurate calculation of dilute quantum gas using Uehling–Uhlenbeck model equation

    Energy Technology Data Exchange (ETDEWEB)

    Yano, Ryosuke, E-mail: ryosuke.yano@tokiorisk.co.jp

    2017-02-01

    The Uehling–Uhlenbeck (U–U) model equation is studied for the fast and accurate calculation of a dilute quantum gas. In particular, the direct simulation Monte Carlo (DSMC) method is used to solve the U–U model equation. DSMC analysis based on the U–U model equation is expected to enable the thermalization to be accurately obtained using a small number of sample particles and the dilute quantum gas dynamics to be calculated in a practical time. Finally, the applicability of DSMC analysis based on the U–U model equation to the fast and accurate calculation of a dilute quantum gas is confirmed by calculating the viscosity coefficient of a Bose gas on the basis of the Green–Kubo expression and the shock layer of a dilute Bose gas around a cylinder.

  7. Modeling of Hydrate Formation Mode in Raw Natural Gas Air Coolers

    Science.gov (United States)

    Scherbinin, S. V.; Prakhova, M. Yu; Krasnov, A. N.; Khoroshavina, E. A.

    2018-05-01

    Air cooling units (ACU) are used at all the gas fields for cooling natural gas after compressing. When using ACUs on raw (wet) gas in a low temperature condition, there is a danger of hydrate plug formation in the heat exchanging tubes of the ACU. To predict possible hydrate formation, a mathematical model of the air cooler thermal behavior used in the control system shall adequately calculate not only gas temperature at the cooler's outlet, but also a dew point value, a temperature at which condensation, as well as the gas hydrate formation point, onsets. This paper proposes a mathematical model allowing one to determine the pressure in the air cooler which makes hydrate formation for a given gas composition possible.

  8. Integrated field modelling[Oil and gas fields

    Energy Technology Data Exchange (ETDEWEB)

    Nazarian, Bamshad

    2002-07-01

    This research project studies the feasibility of developing and applying an integrated field simulator to simulate the production performance of an entire oil or gas field. It integrates the performance of the reservoir, the wells, the chokes, the gathering system, the surface processing facilities and whenever applicable, gas and water injection systems. The approach adopted for developing the integrated simulator is to couple existing commercial reservoir and process simulators using available linking technologies. The simulators are dynamically linked and customised into a single hybrid application that benefits from the concept of open software architecture. The integrated field simulator is linked to an optimisation routine developed based on the genetic algorithm search strategies. This enables optimisation of the system at field level, from the reservoir to the process. Modelling the wells and the gathering network is achieved by customising the process simulator. This study demonstrated that the integrated simulation improves current capabilities to simulate the performance of the entire field and optimise its design. This is achieved by evaluating design options including spread and layout of the wells and gathering system, processing alternatives, reservoir development schemes and production strategies. Effectiveness of the integrated simulator is demonstrated and tested through several field-level case studies that discuss and investigate technical problems relevant to offshore field development. The case studies cover topics such as process optimisation, optimum tie-in of satellite wells into existing process facilities, optimal well location and field layout assessment of a high pressure high temperature deepwater oil field. Case study results confirm the viability of the total field simulator by demonstrating that the field performance simulation and optimal design were obtained in an automated process with treasonable computation time. No significant

  9. Excessive crying in infants

    Directory of Open Access Journals (Sweden)

    Ricardo Halpern

    2016-05-01

    Full Text Available Objective: Review the literature on excessive crying in young infants, also known as infantile colic, and its effects on family dynamics, its pathophysiology, and new treatment interventions. Data source: The literature review was carried out in the Medline, PsycINFO, LILACS, SciELO, and Cochrane Library databases, using the terms “excessive crying,” and “infantile colic,” as well technical books and technical reports on child development, selecting the most relevant articles on the subject, with emphasis on recent literature published in the last five years. Summary of the findings: Excessive crying is a common symptom in the first 3 months of life and leads to approximately 20% of pediatric consultations. Different prevalence rates of excessive crying have been reported, ranging from 14% to approximately 30% in infants up to 3 months of age. There is evidence linking excessive crying early in life with adaptive problems in the preschool period, as well as with early weaning, maternal anxiety and depression, attention deficit hyperactivity disorder, and other behavioral problems. Several pathophysiological mechanisms can explain these symptoms, such as circadian rhythm alterations, central nervous system immaturity, and alterations in the intestinal microbiota. Several treatment alternatives have been described, including behavioral measures, manipulation techniques, use of medication, and acupuncture, with controversial results and effectiveness. Conclusion: Excessive crying in the early months is a prevalent symptom; the pediatrician's attention is necessary to understand and adequately manage the problem and offer support to exhausted parents. The prescription of drugs of questionable action and with potential side effects is not a recommended treatment, except in extreme situations. The effectiveness of dietary treatments and use of probiotics still require confirmation. There is incomplete evidence regarding alternative treatments

  10. Validation of spectral gas radiation models under oxyfuel conditions. Part A: Gas cell experiments

    DEFF Research Database (Denmark)

    Becher, Valentin; Clausen, Sønnik; Fateev, Alexander

    2011-01-01

    from different databases, two statistical-narrow-band models and the exponential wide band model. The two statistical-narrow-band models EM2C and RADCAL showed a good agreement with a maximal band transmissivity deviation of 3%. The exponential-wide-band model showed a deviation of 6%. The new line......-by-line database HITEMP2010 had the lowest band transmissivity deviation of 2.2% and was recommended as a reference model for the validation of simplified CFD models....

  11. Resistive transition for two-dimensional superconductors: Comparison between experiments and Coulomb-gas-model predictions

    International Nuclear Information System (INIS)

    Minnhagen, P.

    1983-01-01

    The Coulomb-gas model of vortex fluctuations leads to scaling relations for the resistive transition which can be directly tested by experiments. By analyzing published resistance data, it is shown that there is experimental evidence for the Coulomb-gas scaling relation in the absence of a perpendicular magnetic field. It is also shown that there exists some suggestive support for the Coulomb-gas predictions in the presence of a magnetic field

  12. Modeling of microbial gas generation: application to the eastern Mediterranean “Biogenic Play”

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, M.; Dubille, M.; Montadert, L.

    2016-07-01

    Biogenic gas is becoming increasingly important as an exploration target in the petroleum industry because it occurs in geologically predictable circumstances and in large quantities at shallow depths as free gas or gas hydrates. As accumulations of biogenic gas result in a subtle synchronization between early generation and early trapping, we integrated a macroscopic model of microbial gas generation within a 3D basin and petroleum system forward simulator. The macroscopic model is based on a microscopic model, which consists in a 1D sedimentary column that accounts for sedimentation, compaction, Darcy flow and Diffusion flow. The organic carbon is the only non-soluble element considered in this version of the model. The dissolved elements are O2, SO4 2-, H2, CH3COOH, and CH4. Methane is dissolved in water or present as a free phase if its concentration exceeds its solubility at given pressure and temperature. In this microscopic model, the transformation of substrate into biomass is described through a set of logistic equations coupled with the transport equations (advection and diffusion). Based on the microscopic considerations we developed the macroscopic model of low maturity/biogenic gas generation in which hydrocarbons are generated through first order kinetic reactions at low maturity. This macroscopic model is adapted to petroleum system modeling at basin scale with TemisFlow®, which aims to understand and predict hydrocarbon generation, migration, and accumulation. It is composed of: i) A source rock criteria which allow defining the biogenic gas source rocks potential and ii) A kinetic model of methane generation. The previous model has been successfully applied on different basins such as the Carupano Basin from the offshore Venezuela, the Magdalena Delta (offshore Colombia) and the offshore Vietnam where direct observations of low-maturity gas were available. Furthermore, it has been applied in the offshore Lebanon in order to check the viability of

  13. Three mechanisms model of shale gas in real state transport through a single nanopore

    Science.gov (United States)

    Li, Dongdong; Zhang, Yanyu; Sun, Xiaofei; Li, Peng; Zhao, Fengkai

    2018-02-01

    At present, the apparent permeability models of shale gas consider only the viscous flow and Knudsen diffusion of free gas, but do not take into account the influence of surface diffusion. Moreover, it is assumed that shale gas is in ideal state. In this paper, shale gas is assumed in real state, a new apparent permeability model for shale gas transport through a single nanopore is developed that captures many important migration mechanisms, such as viscous flow and Knudsen diffusion of free gas, surface diffusion of adsorbed gas. According to experimental data, the accuracy of apparent permeability model was verified. What’s more, the effects of pressure and pore radius on apparent permeability, and the effects on the permeability fraction of viscous flow, Knudsen diffusion and surface diffusion were analysed, separately. Finally, the results indicate that the error of the developed model in this paper was 3.02%, which is less than the existing models. Pressure and pore radius seriously affect the apparent permeability of shale gas. When the pore radius is small or pressure is low, the surface diffusion cannot be ignored. When the pressure and the pore radius is big, the viscous flow occupies the main position.

  14. Abundance, Excess, Waste

    Directory of Open Access Journals (Sweden)

    Rox De Luca

    2016-02-01

    Her recent work focuses on the concepts of abundance, excess and waste. These concerns translate directly into vibrant and colourful garlands that she constructs from discarded plastics collected on Bondi Beach where she lives. The process of collecting is fastidious, as is the process of sorting and grading the plastics by colour and size. This initial gathering and sorting process is followed by threading the components onto strings of wire. When completed, these assemblages stand in stark contrast to the ease of disposability associated with the materials that arrive on the shoreline as evidence of our collective human neglect and destruction of the environment around us. The contrast is heightened by the fact that the constructed garlands embody the paradoxical beauty of our plastic waste byproducts, while also evoking the ways by which those byproducts similarly accumulate in randomly assorted patterns across the oceans and beaches of the planet.

  15. Topiramate Induced Excessive Sialorrhea

    Directory of Open Access Journals (Sweden)

    Ersel Dag

    2015-11-01

    Full Text Available It is well-known that drugs such as clozapine and lithium can cause sialorrhea. On the other hand, topiramate has not been reported to induce sialorrhea. We report a case of a patient aged 26 who was given antiepileptic and antipsychotic drugs due to severe mental retardation and intractable epilepsy and developed excessive sialorrhea complaint after the addition of topiramate for the control of seizures. His complaints continued for 1,5 years and ended after giving up topiramate. We presented this case since it was a rare sialorrhea case induced by topiramate. Clinicians should be aware of the possibility of sialorrhea development which causes serious hygiene and social problems when they want to give topiramate to the patients using multiple drugs.

  16. Modelling of landfill gas adsorption with bottom ash for utilization of renewable energy

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Chen

    2011-10-06

    Energy crisis, environment pollution and climate change are the serious challenges to people worldwide. In the 21st century, human being is trend to research new technology of renewable energy, so as to slow down global warming and develop society in an environmentally sustainable method. Landfill gas, produced by biodegradable municipal solid waste in landfill, is a renewable energy source. In this work, landfill gas utilization for energy generation is introduced. Landfill gas is able to produce hydrogen by steam reforming reactions. There is a steam reformer equipment in the fuel cells system. A sewage plant of Cologne in Germany has run the Phosphoric Acid Fuel Cells power station with biogas for more than 50,000 hours successfully. Landfill gas thus may be used as fuel for electricity generation via fuel cells system. For the purpose of explaining the possibility of landfill gas utilization via fuel cells, the thermodynamics of landfill gas steam reforming are discussed by simulations. In practice, the methane-riched gas can be obtained by landfill gas purification and upgrading. This work investigate a new method for upgrading-landfill gas adsorption with bottom ash experimentally. Bottom ash is a by-product of municipal solid waste incineration, some of its physical and chemical properties are analysed in this work. The landfill gas adsorption experimental data show bottom ash can be used as a potential adsorbent for landfill gas adsorption to remove CO{sub 2}. In addition, the alkalinity of bottom ash eluate can be reduced in these adsorption processes. Therefore, the interactions between landfill gas and bottom ash can be explained by series reactions accordingly. Furthermore, a conceptual model involving landfill gas adsorption with bottom ash is developed. In this thesis, the parameters of landfill gas adsorption equilibrium equations can be obtained by fitting experimental data. On the other hand, these functions can be deduced with theoretical approach

  17. Simulation of Water Level Fluctuations in a Hydraulic System Using a Coupled Liquid-Gas Model

    Directory of Open Access Journals (Sweden)

    Chao Wang

    2015-08-01

    Full Text Available A model for simulating vertical water level fluctuations with coupled liquid and gas phases is presented. The Preissmann implicit scheme is used to linearize the governing equations for one-dimensional transient flow for both liquid and gas phases, and the linear system is solved using the chasing method. Some classical cases for single liquid and gas phase transients in pipelines and networks are studied to verify that the proposed methods are accurate and reliable. The implicit scheme is extended using a dynamic mesh to simulate the water level fluctuations in a U-tube and an open surge tank without consideration of the gas phase. Methods of coupling liquid and gas phases are presented and used for studying the transient process and interaction between the phases, for gas phase limited in a chamber and gas phase transported in a pipeline. In particular, two other simplified models, one neglecting the effect of the gas phase on the liquid phase and the other one coupling the liquid and gas phases asynchronously, are proposed. The numerical results indicate that the asynchronous model performs better, and are finally applied to a hydropower station with surge tanks and air shafts to simulate the water level fluctuations and air speed.

  18. Universal model for water costs of gas exchange by animals and plants.

    Science.gov (United States)

    Woods, H Arthur; Smith, Jennifer N

    2010-05-04

    For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface temperature of the respiratory system near the outside of the organism, the gas consumed (oxygen or carbon dioxide), the steepness of the gradients for gas and vapor, and the transport mode (convective or diffusive). Model predictions were largely confirmed by data on 202 species in five taxa--insects, birds, bird eggs, mammals, and plants--spanning nine orders of magnitude in rate of gas exchange. Discrepancies between model predictions and data seemed to arise from biologically interesting violations of model assumptions, which emphasizes how poorly we understand gas exchange in some taxa. The universal model provides a unified conceptual framework for analyzing exchange-associated water losses across taxa with radically different metabolic and exchange systems.

  19. A model describing intra-granular fission gas behaviour in oxide fuel for advanced engineering tools

    Science.gov (United States)

    Pizzocri, D.; Pastore, G.; Barani, T.; Magni, A.; Luzzi, L.; Van Uffelen, P.; Pitts, S. A.; Alfonsi, A.; Hales, J. D.

    2018-04-01

    The description of intra-granular fission gas behaviour is a fundamental part of any model for the prediction of fission gas release and swelling in nuclear fuel. In this work we present a model describing the evolution of intra-granular fission gas bubbles in terms of bubble number density and average size, coupled to gas release to grain boundaries. The model considers the fundamental processes of single gas atom diffusion, gas bubble nucleation, re-solution and gas atom trapping at bubbles. The model is derived from a detailed cluster dynamics formulation, yet it consists of only three differential equations in its final form; hence, it can be efficiently applied in engineering fuel performance codes while retaining a physical basis. We discuss improvements relative to previous single-size models for intra-granular bubble evolution. We validate the model against experimental data, both in terms of bubble number density and average bubble radius. Lastly, we perform an uncertainty and sensitivity analysis by propagating the uncertainties in the parameters to model results.

  20. Reduced Order Modeling of Combustion Instability in a Gas Turbine Model Combustor

    Science.gov (United States)

    Arnold-Medabalimi, Nicholas; Huang, Cheng; Duraisamy, Karthik

    2017-11-01

    Hydrocarbon fuel based propulsion systems are expected to remain relevant in aerospace vehicles for the foreseeable future. Design of these devices is complicated by combustion instabilities. The capability to model and predict these effects at reduced computational cost is a requirement for both design and control of these devices. This work focuses on computational studies on a dual swirl model gas turbine combustor in the context of reduced order model development. Full fidelity simulations are performed utilizing URANS and Hybrid RANS-LES with finite rate chemistry. Following this, data decomposition techniques are used to extract a reduced basis representation of the unsteady flow field. These bases are first used to identify sensor locations to guide experimental interrogations and controller feedback. Following this, initial results on developing a control-oriented reduced order model (ROM) will be presented. The capability of the ROM will be further assessed based on different operating conditions and geometric configurations.

  1. Hybrid ATDL-gamma distribution model for predicting area source acid gas concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Jakeman, A J; Taylor, J A

    1985-01-01

    An air quality model is developed to predict the distribution of concentrations of acid gas in an urban airshed. The model is hybrid in character, combining reliable features of a deterministic ATDL-based model with statistical distributional approaches. The gamma distribution was identified from a range of distributional models as the best model. The paper shows that the assumptions of a previous hybrid model may be relaxed and presents a methodology for characterizing the uncertainty associated with model predictions. Results are demonstrated for the 98-percentile predictions of 24-h average data over annual periods at six monitoring sites. This percentile relates to the World Health Organization goal for acid gas concentrations.

  2. Experimental study and ERAS modeling of the excess molar enthalpy of (acetonitrile + 1-heptanol or 1-octanol) mixtures at (298.15, 313.15, and 323.15) K and atmospheric pressure

    International Nuclear Information System (INIS)

    Figueiredo Checoni, Ricardo; D'Agostini, Luciane; Zaghini Francesconi, Artur

    2008-01-01

    As a continuation of our studies on excess functions of binary systems, experimental data of excess molar enthalpy (H m E ) of (acetonitrile + 1-heptanol or 1-octanol) mixtures have been determined as a function of composition at (298.15, 313.15, and 323.15) K at atmospheric pressure using a modified 1455 PARR mixture calorimeter. The H m E is positive for both systems over the whole composition range. The applicability of the ERAS-Model to correlate H m E of the mixtures studied was tested. The agreement between experimental and calculated values is satisfactory

  3. Computational Modeling of Microstructural-Evolution in AISI 1005 Steel During Gas Metal Arc Butt Welding

    Science.gov (United States)

    2013-05-01

    H.K.D.H. Bhadeshia, A Model for the Microstruc- ture of Some Advanced Bainitic Steels , Mater. Trans., 1991, 32, p 689–696 19. G.J. Davies and J.G. Garland...REPORT Computational Modeling of Microstructural-Evolution in AISI 1005 Steel During Gas Metal Arc Butt Welding 14. ABSTRACT 16. SECURITY...Computational Modeling of Microstructural-Evolution in AISI 1005 Steel During Gas Metal Arc Butt Welding Report Title ABSTRACT A fully coupled (two-way

  4. Modelling Age- and Density-Related Gas Exchange of Picea abies Canopies in the Fichtelgebirge, Germany

    OpenAIRE

    Falge, Eva; Tennhunen, John D.; Ryel, Ronald J.; Alsheimer, Martina; Köstner, Barbara

    2000-01-01

    International audience; Differences in canopy exchange of water and carbon dioxide that occur due to changes in tree structure and density in montane Norway spruce stands of Central Germany were analyzed with a three dimensional microclimate and gas exchange model STANDFLUX. The model was used to calculate forest radiation absorption, the net photosynthesis and transpiration of single trees, and gas exchange of tree canopies. Model parameterizations were derived for six stands of Picea abies ...

  5. Future evolution of the liberalised European gas market: Simulation results with a dynamic model

    International Nuclear Information System (INIS)

    Lise, Wietze; Hobbs, Benjamin F.

    2008-01-01

    Strategic behaviour by gas producers is likely to affect future gas prices and investments in the European Union (EU). To analyse this issue, a computational game theoretic model is presented that is based on a recursive-dynamic formulation. This model addresses interactions among demand, supply, pipeline and liquefied natural gas (LNG) transport, storage and investments in the natural gas market over the period 2005-2030. Three market scenarios are formulated to study the impact of producer market power. In addition, tradeoffs among investments in pipelines, LNG liquefaction and regasification facilities, and storage are explored. The model runs indicate that LNG can effectively compete with pipelines in the near future. Further, significant decreases in Cournot prices between 2005 and 2010 indicate that near-term investments in EU gas transport capacity are likely to diminish market power by making markets more accessible. (author)

  6. Future evolution of the liberalised European gas market: Simulation results with a dynamic model

    Energy Technology Data Exchange (ETDEWEB)

    Lise, Wietze [IBS Research and Consultancy, Aga Han, Agahamami Cadessi 1/6, Cihangir, 34433 Beyoglu, Istanbul (Turkey); Energy Markets and International Environmental Policy group, ECN Policy Studies, Energy Research Centre of the Netherlands, Amsterdam (Netherlands); Hobbs, Benjamin F. [Department of Geography and Environmental Engineering, The Johns Hopkins University, Ames Hall 313, 3400 North Charles Street, Baltimore, MD 21218 (United States)

    2008-07-15

    Strategic behaviour by gas producers is likely to affect future gas prices and investments in the European Union (EU). To analyse this issue, a computational game theoretic model is presented that is based on a recursive-dynamic formulation. This model addresses interactions among demand, supply, pipeline and liquefied natural gas (LNG) transport, storage and investments in the natural gas market over the period 2005-2030. Three market scenarios are formulated to study the impact of producer market power. In addition, tradeoffs among investments in pipelines, LNG liquefaction and regasification facilities, and storage are explored. The model runs indicate that LNG can effectively compete with pipelines in the near future. Further, significant decreases in Cournot prices between 2005 and 2010 indicate that near-term investments in EU gas transport capacity are likely to diminish market power by making markets more accessible. (author)

  7. Excess molar volume, viscosity, and refractive index study for the ternary mixture {2-methyl-2-butanol (1) + tetrahydrofuran (2) + propylamine (3)} at different temperatures. Application of the ERAS-model and Peng-Robinson-Stryjek-Vera equation of state

    International Nuclear Information System (INIS)

    Fattahi, M.; Iloukhani, H.

    2010-01-01

    Densities, viscosities, and refractive indices of the ternary mixture consist of {2-methyl-2-butanol (1) + tetrahydrofuran (THF) (2) + propylamine (3)} at a temperature of 298.15 K and related binary mixtures were measured at temperatures of (288.15, 298.15, and 308.15) K at ambient pressure. Data were used to calculate the excess molar volumes and the deviations of the viscosity and refractive index. The Redlich-Kister and the Cibulka equations were used for correlating binary and ternary properties, respectively. The ERAS-model has been applied for describing the binary and ternary excess molar volumes and also Peng-Robinson-Stryjek-Vera (PRSV) equation of state (EOS) has been used to predict the binary and ternary excess molar volumes and viscosities.

  8. Modelling the association between in vitro gas production and ...

    African Journals Online (AJOL)

    In vitro gas production of four different browse plants (Azadirachta indica, Terminalia catappa, Mangifera indica and Vernonia amygdalina) was investigated under different extractions. The relationship between the forage composition parameters (dry matter, organic matter, crude protein, acid detergent fibre, neutral ...

  9. Multiscale modelling of single crystal superalloys for gas turbine blades

    NARCIS (Netherlands)

    Tinga, T.

    2009-01-01

    Gas turbines are extensively used for power generation and for the propulsion of aircraft and vessels. Their most severely loaded parts, the turbine rotor blades, are manufactured from single crystal nickel-base superalloys. The superior high temperature behaviour of these materials is attributed to

  10. A simple model of gas flow in a porous powder compact

    Energy Technology Data Exchange (ETDEWEB)

    Shugard, Andrew D. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Robinson, David B. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2014-04-01

    This report describes a simple model for ideal gas flow from a vessel through a bed of porous material into another vessel. It assumes constant temperature and uniform porosity. Transport is treated as a combination of viscous and molecular flow, with no inertial contribution (low Reynolds number). This model can be used to fit data to obtain permeability values, determine flow rates, understand the relative contributions of viscous and molecular flow, and verify volume calibrations. It draws upon the Dusty Gas Model and other detailed studies of gas flow through porous media.

  11. Simulasi Tumbukan Partikel Gas Ideal Dengan Model Cellular Automata Dua Dimensi

    OpenAIRE

    Abdul Basid, Annisa Mujriati

    2010-01-01

    Telah dilakukan simulasi tumbukan partikel gas ideal dengan menggunakan  model cellular automata dua dimensi untuk memvisualisasikan tumbukan partikel gas ideal. Tumbukan partikel  disimulasikan  dengan  menggunakan  model  cellular  automata  dua  dimensi.  Di  dalam cellular automata, pergerakan partikel diatur dengan suatu aturan  yaitu aturan delapan tetangga yang merupakan aturan acak. Hasil program simulasi tumbukan partikel gas ideal dengan model cellular automata dua dimensi  mengguna...

  12. A Dynamic Model of the Combined Electricity and Natural Gas Markets

    DEFF Research Database (Denmark)

    Jenkins, Sandra; Annaswamy, Anuradha M.; Hansen, Jacob

    2015-01-01

    With the shale gas revolution, coal retirements, environmental regulations, and increasing renewable energy resources, the interdependency of natural gas and electricity has grown significantly. Interdependency challenges, such as mismatched market schedules and disparate market operations, require...... quantitative modeling in order to garner insights into the effectiveness of various solutions. In this paper, a quantitative model with a dynamic market mechanism is proposed to evaluate the effects of the fuel uncertainty of natural gas-fired power plants on Social Welfare. The results of the model show...

  13. Preliminary findings of the Viking gas exchange experiment and a model for Martian surface chemistry

    International Nuclear Information System (INIS)

    Oyama, V.I.; Berdahl, B.J.; Carle, G.C.

    1977-01-01

    It is stated that O 2 and CO 2 were evolved from humidified Martian soil in the gas exchange experiment on Viking Lander 1. Small changes in N 2 gas were also recorded. A model of the morphology and a hypothesis of the mechanistics of the Martian surface are proposed. (author)

  14. Interacting polytropic gas model of phantom dark energy in non-flat universe

    International Nuclear Information System (INIS)

    Karami, K.; Ghaffari, S.; Fehri, J.

    2009-01-01

    By introducing the polytropic gas model of interacting dark energy, we obtain the equation of state for the polytropic gas energy density in a non-flat universe. We show that for an even polytropic index by choosing K>Ba (3)/(n) , one can obtain ω Λ eff <-1, which corresponds to a universe dominated by phantom dark energy. (orig.)

  15. Governing through visions : Evaluating the performativity of the European gas target models

    NARCIS (Netherlands)

    Dignum, M.; Correlje, A.F.; Groenleer, Martijn; Scholten, D.J.

    2017-01-01

    In 2010 an initiative was launched to realize a competitive single EU market for natural gas through the use of a future vision. This Gas Target Model (GTM) aimed to provide direction for concrete market development through regulatory structures as well as an overarching scope of what a

  16. Geochemical modelling of hydrogen gas migration in an unsaturated bentonite buffer

    NARCIS (Netherlands)

    Sedighi, M.; Thomas, H.R.; Al Masum, S.; Vardon, P.J.; Nicholson, D.; Chen, Q.

    2014-01-01

    This paper presents an investigation of the transport and fate of hydrogen gas through compacted bentonite buffer. Various geochemical reactions that may occur in the multiphase and multicomponent system of the unsaturated bentonite buffer are considered. A reactive gas transport model, developed

  17. Probabilistic modelling of security of supply in gas networks and evaluation of new infrastructure

    International Nuclear Information System (INIS)

    Praks, Pavel; Kopustinskas, Vytis; Masera, Marcelo

    2015-01-01

    The paper presents a probabilistic model to study security of supply in a gas network. The model is based on Monte-Carlo simulations with graph theory, and is implemented in the software tool ProGasNet. The software allows studying gas networks in various aspects including identification of weakest links and nodes, vulnerability analysis, bottleneck analysis, evaluation of new infrastructure etc. In this paper ProGasNet is applied to a benchmark network based on a real EU gas transmission network of several countries with the purpose of evaluating the security of supply effects of new infrastructure, either under construction, recently completed or under planning. The probabilistic model enables quantitative evaluations by comparing the reliability of gas supply in each consuming node of the network. - Highlights: • A Monte-Carlo algorithm for stochastic flow networks is presented. • Network elements can fail according to a given probabilistic model. • Priority supply pattern of gas transmission networks is assumed. • A real-world EU gas transmission network is presented and analyzed. • A risk ratio is used for security of supply quantification of a new infrastructure.

  18. Relationship between in situ degradation kinetics and in vitro gas production fermentation using different mathematical models

    NARCIS (Netherlands)

    Rodrigues, M.A.M.; Cone, J.W.; Ferreira, L.M.M.; Blok, M.C.; Guedes, C.

    2009-01-01

    In vitro and in situ studies were conducted to evaluate the influence of different mathematical models, used to fit gas production profiles of 15 feedstuffs, on estimates of nylon bag organic matter (OM) degradation kinetics. The gas production data were fitted to Exponential, Logistic, Gompertz and

  19. Development of a New Drag Coefficient Model for Oil and Gas ...

    African Journals Online (AJOL)

    Development of a New Drag Coefficient Model for Oil and Gas Multiphase Fluid Systems. ... PROMOTING ACCESS TO AFRICAN RESEARCH ... suspensions of solid particles are frequently encountered in many industrial processes including oil & gas production. ... EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT

  20. MATHEMATIC MODELING IN ANALYSIS OF BIO-GAS PURIFICATION FROM CARBON DIOXIDE

    Directory of Open Access Journals (Sweden)

    Y. A. Losiouk

    2009-01-01

    Full Text Available The paper considers a possibility to involve bio-gas generated at testing grounds of hard domestic garbage in power supply system in the Republic of Belarus. An example of optimization using mathematical modeling of plant operation which is used for bio-gas enrichment is given in the paper. 

  1. LANDFILL GAS EMISSIONS MODEL (LANDGEM) VERSION 3.02 USER'S GUIDE

    Science.gov (United States)

    The Landfill Gas Emissions Model (LandGEM) is an automated estimation tool with a Microsoft Excel interface that can be used to estimate emission rates for total landfill gas, methane, carbon dioxide, nonmethane organic compounds, and individual air pollutants from municipal soli...

  2. A comparison between EGR and lean-burn strategies employed in a natural gas SI engine using a two-zone combustion model

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, Amr; Bari, Saiful [Sustainable Energy Centre, School of Advanced Manufacturing and Mechanical Engineering, Univ. of South Australia, Mawson Lakes SA 5095 (Australia)

    2009-12-15

    Exhaust gas recirculation (EGR) strategy has been recently employed in natural gas SI engines as an alternative to lean burn technique in order to satisfy the increasingly stringent emission standards. However, the effect of EGR on some of engine performance parameters compared to lean burn is not yet quite certain. In the current study, the effect of both EGR and lean burn on natural gas SI engine performance was compared at similar operating conditions. This was achieved numerically by developing a computer simulation of the four-stroke spark-ignition natural gas engine. A two-zone combustion model was developed to simulate the in-cylinder conditions during combustion. A kinetic model based on the extended Zeldovich mechanism was also developed in order to predict NO emission. The combustion model was validated using experimental data and a good agreement between the results was found. It was demonstrated that adding EGR to the stoichiometric inlet charge at constant inlet pressure of 130 kPa decreased power more rapidly than excess air; however, the power loss was recovered by increasing the inlet pressure from 130 kPa at zero dilution to 150 kPa at 20% EGR dilution. The engine fuel consumption increased by 10% when 20% EGR dilution was added at inlet pressure of 150 kPa compared to using 20% air dilution at 130 kPa. However, it was found that EGR dilution strategy is capable of producing extremely lower NO emission than lean burn technique. NO emission was reduced by about 70% when the inlet charge was diluted at a rate of 20% using EGR instead of excess air. (author)

  3. A comparison between EGR and lean-burn strategies employed in a natural gas SI engine using a two-zone combustion model

    International Nuclear Information System (INIS)

    Ibrahim, Amr; Bari, Saiful

    2009-01-01

    Exhaust gas recirculation (EGR) strategy has been recently employed in natural gas SI engines as an alternative to lean burn technique in order to satisfy the increasingly stringent emission standards. However, the effect of EGR on some of engine performance parameters compared to lean burn is not yet quite certain. In the current study, the effect of both EGR and lean burn on natural gas SI engine performance was compared at similar operating conditions. This was achieved numerically by developing a computer simulation of the four-stroke spark-ignition natural gas engine. A two-zone combustion model was developed to simulate the in-cylinder conditions during combustion. A kinetic model based on the extended Zeldovich mechanism was also developed in order to predict NO emission. The combustion model was validated using experimental data and a good agreement between the results was found. It was demonstrated that adding EGR to the stoichiometric inlet charge at constant inlet pressure of 130 kPa decreased power more rapidly than excess air; however, the power loss was recovered by increasing the inlet pressure from 130 kPa at zero dilution to 150 kPa at 20% EGR dilution. The engine fuel consumption increased by 10% when 20% EGR dilution was added at inlet pressure of 150 kPa compared to using 20% air dilution at 130 kPa. However, it was found that EGR dilution strategy is capable of producing extremely lower NO emission than lean burn technique. NO emission was reduced by about 70% when the inlet charge was diluted at a rate of 20% using EGR instead of excess air.

  4. Forecasting the natural gas demand in China using a self-adapting intelligent grey model

    International Nuclear Information System (INIS)

    Zeng, Bo; Li, Chuan

    2016-01-01

    Reasonably forecasting demands of natural gas in China is of significance as it could aid Chinese government in formulating energy policies and adjusting industrial structures. To this end, a self-adapting intelligent grey prediction model is proposed in this paper. Compared with conventional grey models which have the inherent drawbacks of fixed structure and poor adaptability, the proposed new model can automatically optimize model parameters according to the real data characteristics of modeling sequence. In this study, the proposed new model, discrete grey model, even difference grey model and classical grey model were employed, respectively, to simulate China's natural gas demands during 2002–2010 and forecast demands during 2011–2014. The results show the new model has the best simulative and predictive precision. Finally, the new model is used to forecast China's natural gas demand during 2015–2020. The forecast shows the demand will grow rapidly over the next six years. Therefore, in order to maintain the balance between the supplies and the demands for the natural gas in the future, Chinese government needs to take some measures, such as importing huge amounts of natural gas from abroad, increasing the domestic yield, using more alternative energy, and reducing the industrial reliance on natural gas. - Highlights: • A self-adapting intelligent grey prediction model (SIGM) is proposed in this paper. • The SIGM has the advantage of working with exponential functions and linear functions. • The SIGM solves the drawbacks of fixed structure and poor adaptability of grey models. • The demand of natural gas in China is successfully forecasted using the SIGM model. • The study findings can help Chinese government reasonably formulate energy policies.

  5. Fission gas release at high burn-up: beyond the standard diffusion model

    International Nuclear Information System (INIS)

    Landskron, H.; Sontheimer, F.; Billaux, M.R.

    2002-01-01

    At high burn-up standard diffusion models describing the release of fission gases from nuclear fuel must be extended to describe the experimental loss of xenon observed in the fuel matrix of the rim zone. Marked improvements of the prediction of integral fission gas release of fuel rods as well as of radial fission gas profiles in fuel pellets are achieved by using a saturation concept to describe fission gas behaviour not only in the pellet rim but also as an additional fission gas path in the whole pellet. (author)

  6. Fission gas behaviour modelling in plate fuel during a power transient

    International Nuclear Information System (INIS)

    Portier, S.

    2003-01-01

    This thesis is dedicated to the identification and modelization of the phenomena which are at the origin of the release of the fission gas formed in UO 2 plate fuels during the irradiation in a power transient. In the first experimental part, samples of plate fuels, irradiated at 36 GWj/tU, have been annealed to temperatures from 1100 C to 1500 C in a device that enabled the measurement of gas release in real time. At 1300 C, post-annealing observations demonstrated a link between the measured gas releases to a rapid formation of labyrinths at the grain surface. These labyrinths, which were formed by intergranular bubble interconnection, create release paths for the gas atoms which reach the grain surface. At this stage, the available experimental results (annealing and observations) were interpreted considering that it is the spreading of the gas atoms from the grains to the grain boundaries that is at the origin of the observed releases. This interpretation generates the hypothesis that a) at the end of the basic irradiation, the gas is at the atomic state and b) during the annealing, the spreading is reduced by the intragranular bubbles of the gas atoms. The last part of the work is dedicated to the modelization of the main phenomena at the origin of the gas release. The model developed, based on the model of the gas behaviour in MARGARET PWR, highlighted the great influence of the irradiation conditions on the gas distribution at the end of the irradiation and also its influence on the fission gas release during the power transient. (author) [fr

  7. V819 TAU: A RARE WEAK-LINED T TAURI STAR WITH A WEAK INFRARED EXCESS

    International Nuclear Information System (INIS)

    Furlan, E.; Forrest, W. J.; Manoj, P.; Kim, K. H.; Watson, Dan M.; Sargent, B. A.

    2009-01-01

    We use Spitzer data to infer that the small infrared excess of V819 Tau, a weak-lined T Tauri star in Taurus, is real and not attributable to a 'companion' 10'' to the south. We do not confirm the mid-infrared excess in HBC 427 and V410 X-ray 3, which are also non-accreting T Tauri stars in the same region; instead, for the former object, the excess arises from a red companion 9'' to the east. A single-temperature blackbody fit to the continuum excess of V819 Tau implies a dust temperature of 143 K; however, a better fit is achieved when the weak 10 and 20 μm silicate emission features are also included. We infer a disk of sub-μm silicate grains between about 1 AU and several 100 AU with a constant surface density distribution. The mid-infrared excess of V819 Tau can be successfully modeled with dust composed mostly of small amorphous olivine grains at a temperature of 85 K, and most of the excess emission is optically thin. The disk could still be primordial, but gas-poor and therefore short-lived, or already at the debris disk stage, which would make it one of the youngest debris disk systems known.

  8. Modelling of far-field gas migration from a deep radioactive waste repository

    International Nuclear Information System (INIS)

    Rodwell, W.R.; Nash, P.J.

    1992-01-01

    In assessing the post-closure safety of a deep radioactive waste repository, it is necessary to show that gas generated within the repository can migrate away, through the far-field geology, without affecting repository safety. This paper discusses the contribution of various mechanisms to gas migration through the far field; for example, diffusion of dissolved gas versus gas-phase movement, and bubble flow versus formation of a connected gas stream. It outlines different approaches to modelling gas movement from a repository, with simple semi-analytical models furnishing physical insights into the factors controlling gas migration in the absence of directly applicable experimental data, and more comprehensive numerical computations allowing the exploration of more detailed behaviour when appropriate data is obtained. If gas can induce groundwater movement, this could accelerate the transport of water-borne contaminants. Processes by which this could occur are noted, and the current status of work on possible effects of gas migration on groundwater movement in fractured hard rocks is indicated. 14 refs., 4 figs

  9. Relating landfill gas emissions to atmospheric pressure using numerical modeling and state-space analysis

    DEFF Research Database (Denmark)

    Poulsen, T.G.; Christophersen, Mette; Moldrup, P.

    2003-01-01

    were applied: (I) State-space analysis was used to identify relations between gas flux and short-term (hourly) variations in atmospheric pressure. (II) A numerical gas transport model was fitted to the data and used to quantify short-term impacts of variations in atmospheric pressure, volumetric soil......-water content, soil gas permeability, soil gas diffusion coefficients, and biological CH4 degradation rate upon landfill gas concentration and fluxes in the soil. Fluxes and concentrations were found to be most sensitive to variations in volumetric soil water content, atmospheric pressure variations and gas...... permeability whereas variations in CH4 oxidation rate and molecular coefficients had less influence. Fluxes appeared to be most sensitive to atmospheric pressure at intermediate distances from the landfill edge. Also overall CH4 fluxes out of the soil over longer periods (years) were largest during periods...

  10. New models needed to manage gas supply, APPrO conference hears

    International Nuclear Information System (INIS)

    Anon.

    2005-01-01

    Details of a 1 day conference designed to create more efficient interactions between the gas supply and electricity systems in Ontario and new models for gas supply and the electricity system were presented. Market efficiency, generators' perspectives on critical gas issues, an overview of the North American gas and an outline of issues concerning Ontario were discussed. A natural gas industry forecast and issues concerning marketers and producers were presented. The terms on which gas is bought and sold were discussed. Regulatory tools, cost allocation and issues relating to unbundling were also presented. Infrastructure needs were reviewed, as well as basic market structures. It was suggested that appropriate commercial service options need to be developed and approved, including cross-utility services

  11. Modelling gas migration in compacted bentonite. A report produced for the GAMBIT club

    International Nuclear Information System (INIS)

    Nash, P.J.; Swift, B.T.; Goodfield, M.; Rodwell, W.R.

    1998-08-01

    This report describes the first phase of a programme of work that has as its overall objective the development of a computational model that can simulate the results of experiments on gas migration through highly compacted bentonite, and will provide the basis of a model suitable to assess the effects of bentonite barriers on the build-up of pressure and the escape of hydrogen gas from disposal canisters in a radioactive waste repository. In this first phase of the project, the possible mechanisms and controlling features of gas migration through compacted bentonite have been reviewed, and a preliminary computational model of the process has been implemented and evaluated. In the model it is assumed that gas invasion of the clay occurs by induced microfissuring, and that the permeability of the pathways thus created depends on the gas pressure (or the effective stress). Experimental data on gas migration in compacted bentonite that was collected under well controlled conditions by Horseman and Harrington was used in a preliminary evaluation of the new model. The model was able to reproduce qualitatively all the features seen in the subset of the experimental data used in the evaluation, and to provide quantitative agreement to substantial sections of the results of test sequences, but quantitative agreement between simulation and experimental results over a whole test sequence was not obtained. As part of the model evaluation, the dependence of the results obtained on key model parameters is reported. Outline plans for a further phase of work are suggested. (orig.)

  12. Modelling gas migration in compacted bentonite. A report produced for the GAMBIT club

    Energy Technology Data Exchange (ETDEWEB)

    Nash, P.J.; Swift, B.T.; Goodfield, M.; Rodwell, W.R. [AEA Technology plc, Dorchester (United Kingdom)

    1998-08-01

    This report describes the first phase of a programme of work that has as its overall objective the development of a computational model that can simulate the results of experiments on gas migration through highly compacted bentonite, and will provide the basis of a model suitable to assess the effects of bentonite barriers on the build-up of pressure and the escape of hydrogen gas from disposal canisters in a radioactive waste repository. In this first phase of the project, the possible mechanisms and controlling features of gas migration through compacted bentonite have been reviewed, and a preliminary computational model of the process has been implemented and evaluated. In the model it is assumed that gas invasion of the clay occurs by induced microfissuring, and that the permeability of the pathways thus created depends on the gas pressure (or the effective stress). Experimental data on gas migration in compacted bentonite that was collected under well controlled conditions by Horseman and Harrington was used in a preliminary evaluation of the new model. The model was able to reproduce qualitatively all the features seen in the subset of the experimental data used in the evaluation, and to provide quantitative agreement to substantial sections of the results of test sequences, but quantitative agreement between simulation and experimental results over a whole test sequence was not obtained. As part of the model evaluation, the dependence of the results obtained on key model parameters is reported. Outline plans for a further phase of work are suggested. (orig.) 32 refs.

  13. Dynamic modeling of fixed-bed adsorption of flue gas using a variable mass transfer model

    International Nuclear Information System (INIS)

    Park, Jehun; Lee, Jae W.

    2016-01-01

    This study introduces a dynamic mass transfer model for the fixed-bed adsorption of a flue gas. The derivation of the variable mass transfer coefficient is based on pore diffusion theory and it is a function of effective porosity, temperature, and pressure as well as the adsorbate composition. Adsorption experiments were done at four different pressures (1.8, 5, 10 and 20 bars) and three different temperatures (30, 50 and 70 .deg. C) with zeolite 13X as the adsorbent. To explain the equilibrium adsorption capacity, the Langmuir-Freundlich isotherm model was adopted, and the parameters of the isotherm equation were fitted to the experimental data for a wide range of pressures and temperatures. Then, dynamic simulations were performed using the system equations for material and energy balance with the equilibrium adsorption isotherm data. The optimal mass transfer and heat transfer coefficients were determined after iterative calculations. As a result, the dynamic variable mass transfer model can estimate the adsorption rate for a wide range of concentrations and precisely simulate the fixed-bed adsorption process of a flue gas mixture of carbon dioxide and nitrogen.

  14. A system dynamic model for production and consumption policy in Iran oil and gas sector

    International Nuclear Information System (INIS)

    Kiani, Behdad; Ali Pourfakhraei, Mohammad

    2010-01-01

    A system dynamic model is presented, which considers the feedback between supply and demand and oil revenue of the existing system in Iran considering different sectors of the economy. Also the export of the oil surplus and the injection of the gas surplus into the oil reservoirs are seen in the model by establishing a balance between supply and demand. In this model the counter-effects and existing system feedbacks between supply and demand and oil revenue can be seen considering different sectors of the economy. As a result, the effects of oil and gas policies in different scenarios for different sectors of Iran's economy together with the counter-effects of energy consumption and oil revenue are examined. Three scenarios, which show the worst, base and ideal cases, are considered to find future trends of major variables such as seasonal gas consumption in power plants, seasonal injected gas in oil reservoirs, economic growth in the industrial sector, oil consumption in the transportation sector, industrial gas consumption and exported gas. For example, it is shown that the exported gas will reach between 500 and 620 million cubic-meter per day in different scenarios and export revenues can reach up to $500 billion by 2025. - Research Highlights: →A system dynamic model analyzing the feedback between supply, demand and oil revenue is built. →The export of the oil surplus and the injection of the gas surplus into oil reservoirs are modeled. →Effects of oil and gas policies in different scenarios are examined for Iran's economy. →Counter-effects of energy consumption and oil revenue are examined. →Exported gas will reach between 500 and 620 million cubic-meter per day in different scenarios. →Export revenues can reach up to $500 billion by 2025.

  15. The economics of natural gas infrastructure investments. Theory and model-based analysis for Europe

    Energy Technology Data Exchange (ETDEWEB)

    Lochner, Stefan

    2012-07-01

    Changing supply structures, security of supply threats and efforts to eliminate bottlenecks and increase competition in the European gas market potentially warrant infrastructure investments. However, which investments are actually efficient is unclear. From a theoretical perspective, concepts from other sectors regarding the estimation of congestion cost and efficient investment can be applied - with some extensions - to natural gas markets. Investigations in a simple analytical framework, thereby, show that congestion does not necessarily imply that investment is efficient, and that there are multiple interdependencies between investments in different infrastructure elements (pipeline grid, gas storage, import terminals for liquefied natural gas (LNG)) which need to be considered in an applied analysis. Such interdependencies strengthen the case for a model-based analysis. An optimization model minimizing costs can illustrate the first-best solution with respect to investments in natural gas infrastructure; gas market characteristics such as temperature-dependent stochasticity of demand or the lumpiness of investments can be included. Scenario analyses help to show the effects of changing the underlying model presumption. Hence, results are projections subject to data and model assumption - and not forecasts. However, as they depict the optimal, cost-minimizing outcome, results provide a guideline to policymakers and regulators regarding the desirable market outcome. A stochastic mixed-integer dispatch and investment model for the European natural gas infrastructure is developed as an optimization model taking the theoretical inter-dependencies into account. It is based on an extensive infrastructure database including long-distance transmission pipelines, LNG terminals and gas storage sites with a high level of spatial granularity. It is parameterized with assumptions on supply and demand developments as well as empirically derived infrastructure extension costs

  16. Uncertainty and sensitivity analysis of fission gas behavior in engineering-scale fuel modeling

    Energy Technology Data Exchange (ETDEWEB)

    Pastore, Giovanni, E-mail: Giovanni.Pastore@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Swiler, L.P., E-mail: LPSwile@sandia.gov [Optimization and Uncertainty Quantification, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-1318 (United States); Hales, J.D., E-mail: Jason.Hales@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Novascone, S.R., E-mail: Stephen.Novascone@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Perez, D.M., E-mail: Danielle.Perez@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Spencer, B.W., E-mail: Benjamin.Spencer@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States); Luzzi, L., E-mail: Lelio.Luzzi@polimi.it [Politecnico di Milano, Department of Energy, Nuclear Engineering Division, via La Masa 34, I-20156 Milano (Italy); Van Uffelen, P., E-mail: Paul.Van-Uffelen@ec.europa.eu [European Commission, Joint Research Centre, Institute for Transuranium Elements, Hermann-von-Helmholtz-Platz 1, D-76344 Karlsruhe (Germany); Williamson, R.L., E-mail: Richard.Williamson@inl.gov [Fuel Modeling and Simulation, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-3840 (United States)

    2015-01-15

    The role of uncertainties in fission gas behavior calculations as part of engineering-scale nuclear fuel modeling is investigated using the BISON fuel performance code with a recently implemented physics-based model for fission gas release and swelling. Through the integration of BISON with the DAKOTA software, a sensitivity analysis of the results to selected model parameters is carried out based on UO{sub 2} single-pellet simulations covering different power regimes. The parameters are varied within ranges representative of the relative uncertainties and consistent with the information in the open literature. The study leads to an initial quantitative assessment of the uncertainty in fission gas behavior predictions with the parameter characterization presently available. Also, the relative importance of the single parameters is evaluated. Moreover, a sensitivity analysis is carried out based on simulations of a fuel rod irradiation experiment, pointing out a significant impact of the considered uncertainties on the calculated fission gas release and cladding diametral strain. The results of the study indicate that the commonly accepted deviation between calculated and measured fission gas release by a factor of 2 approximately corresponds to the inherent modeling uncertainty at high fission gas release. Nevertheless, significantly higher deviations may be expected for values around 10% and lower. Implications are discussed in terms of directions of research for the improved modeling of fission gas behavior for engineering purposes.

  17. Improving the performances of gas turbines operated on natural gas in combined cycle power plants with application of mathematical models

    International Nuclear Information System (INIS)

    Dimkovski, Sasho

    2014-01-01

    The greater energy demand by today society sets a number of new challenges in the energy sector. The climate extremes impose new modes of operation of the power plants, with high flexibility in production. Combined cycle co generative power plants are the latest trend in the energy sector. Their high prevalence is due to the great efficiency and the good environmental characteristics. The main work horse in these cogeneration plants is the gas turbine, which power production and efficiency strongly depends on the external climate conditions. In warmer periods when there is increased demand for electricity, the power production from the gas turbines significantly declines. Because of the high electricity demand from the grid and reduced power production from the gas turbines at the same time, the need for application of appropriate technology for preserving the performances and power of the gas turbines arises. This master thesis explores different methods to improve the power in gas turbines by cooling the air on the compressor inlet, analyzing their applicability and effectiveness in order to choose the optimal method for power augmentation for the climatic conditions in the city Skopje. The master thesis gives detailed analysis of the weather in Skopje and the time frame in which the chosen method is applicable. At the end in the master thesis, the economic feasibility of the given method for power augmentation is clearly calculated, using a model of a power plant and calculating the resulting amount of gained energy, the amount of the initial investment, the cost for maintenance and operation of the equipment. By these calculations the period for initial return of investment is obtained. As an added benefit the positive environmental impacts of the applied technology for inlet air cooling is analyzed. (author)

  18. Validation of mechanistic models for gas precipitation in solids during postirradiation annealing experiments

    Science.gov (United States)

    Rest, J.

    1989-12-01

    A number of different phenomenological models for gas precipitation in solids during postirradiation annealing experiments have been proposed. Validation of such mechanistic models for gas release and swelling is complicated by the use of data containing large systematic errors, and phenomena characterized by synergistic effects as well as uncertainties in materials properties. Statistical regression analysis is recommended for the selection of a reasonably well characterized data base for gas release from irradiated fuel under transient heating conditions. It is demonstrated that an appropriate data selection method is required in order to realistically examine the impact of differing descriptions of the phenomena, and uncertainties in selected materials properties, on the validation results. The results of the analysis show that the kinetics of gas precipitation in solids depend on bubble overpressurization effects and need to be accounted for during the heatup phase of isothermal heating experiments. It is shown that if only the total gas release values (as opposed to time-dependent data) were available, differentiation between different gas precipitation models would be ambiguous. The observed sustained increase in the fractional release curve at relatively high temperatures after the total precipitation of intragranular gas in fission gas bubbles is ascribed to the effects of a grain-growth/grain-boundary sweeping mechanism.

  19. Validation of mechanistic models for gas precipitation in solids during postirradiation annealing experiments

    International Nuclear Information System (INIS)

    Rest, J.

    1989-01-01

    A number of different phenomenological models for gas precipitation in solids during postirradiation annealing experiments have been proposed. Validation of such mechanistic models for gas release and swelling is complicated by the use of data containing large systematic errors, and phenomena characterized by synergistic effects as well as uncertainties in materials properties. Statistical regression analysis is recommended for the selection of a reasonably well characterized data base for gas release from irradiated fuel under transient heating conditions. It is demonstrated that an appropriate data selection method is required in order to realistically examine the impact of differing descriptions of the phenomena, and uncertainties in selected materials properties, on the validation results. The results of the analysis show that the kinetics of gas precipitation in solid depend on bubble overpressurization effects and need to be accounted for during the heatup phase of isothermal heating experiments. It is shown that if only the total gas release values (as opposed to time-dependent data) were available, differentiation between different gas precipitation models would be ambiguous. The observed sustained increase in the fractional release curve at relatively high temperatures after the total precipitation of intragranular gas in fission gas bubbles is ascribed to the effects of a grain-growth/grain-boundary sweeping mechanism. (orig.)

  20. Laser-Irradiated Gas Puff Target Plasma Modeling

    Czech Academy of Sciences Publication Activity Database

    Vrba, Pavel; Vrbová, M.

    2014-01-01

    Roč. 42, č. 10 (2014), s. 2600-2601 ISSN 0093-3813 R&D Projects: GA ČR GAP102/12/2043 Grant - others:GA MŠk(CZ) CZ.1.07/2.3.00/20.0092 Institutional support: RVO:61389021 Keywords : Gas puff laser plasma * water window radiation source * RHMD code Z* Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.101, year: 2014 http://ieeexplore.ieee.org

  1. Modeling of gas demand using degree-day concept: case study for Ankara

    International Nuclear Information System (INIS)

    Gumrah, F.; Katircioglu, D.; Aykan, Y.; Okumus, S.; Kilincer, N.

    2001-01-01

    The demand for natural gas is rapidly increasing in Turkey, as it is in the rest of the world. However, natural gas reserves and production are rather limited in Turkey.The bulk of the Turkish gas demand is met by imports. Russia currently accounts for 69% of Turkey's gas supplies. Physical shortages might occur; supplies for industrial production and household consumption could temporarily run short. Also, fluctuations in consumption might occur due to climatic reasons or peak daily industrial energy demand. Underground gas storage is a necessity in order to regulate these seasonal, daily, and hourly fluctuations. In order to effectively design and utilize underground gas storage, it is necessary to identify the market requirements. In this study, Ankara was chosen as a pilot region due to its strategical importance of being the capital city of Turkey, and a wide range of marketing surveys for the last seven years was performed. All of the factors influencing the gas consumption and the relationships between these factors were analyzed. How does gas demand behave in extremely cold weather? How does the industrial part of the city act in the consumption behavior? What are the plans of the Municipality of Ankara, responsible for the execution of the natural gas distribution project in Ankara? A model was developed based on degree-day (DD) concept, including the annual number of customers, average DDs, and the usage per customer. A history matching study was performed to verify the results of the model with the measured consumption data for the last seven years. Comparisons showed that the calculated consumption by DD model and measured daily consumption were in good agreement. Finally, by using the developed approach, the gas demand was forecasted for Ankara up to 2005. The results of this study can be used to design underground gas storage facility near Ankara. (author)

  2. Security of supply and retail competition in the European gas market. Some model-based insights

    International Nuclear Information System (INIS)

    Abada, Ibrahim; Massol, Olivier

    2011-04-01

    In this paper, we analyze the impact of uncertain disruptions in gas supply upon gas retailer contracting behavior and consequent price and welfare implications in a gas market characterized by long-term gas contracts using a static Cournot model. In order to most realistically describe the economical situation, our representation divides the market into two stages: the upstream market that links, by means of long-term contracts, producers in exporting countries (Russia, Algeria, etc.) to local retailers who bring gas to the consuming countries to satisfy local demands in the downstream market. Disruption costs are modeled using short-run demand functions. First we mathematically develop a general model and write the associated KKT conditions, then we propose some case studies, under iso-elasticity assumptions, for the long-short-run inverse-demand curves in order to predict qualitatively and quantitatively the impacts of supply disruptions on Western European gas trade. In the second part, we study in detail the German gas market of the 1980's to explain the supply choices of the German retailer, and we derive interesting conclusions and insights concerning the amounts and prices of natural gas brought to the market. The last part of the paper is dedicated to a study of the Bulgarian gas market, which is greatly dependent on the Russian gas supplies and hence very sensitive to interruption risks. Some interesting conclusions are derived concerning the necessity to economically regulate the market, by means of gas amounts control, if the disruption probability is high enough. (authors)

  3. Numerical modeling and optimization of the Iguassu gas centrifuge

    Science.gov (United States)

    Bogovalov, S. V.; Borman, V. D.; Borisevich, V. D.; Tronin, V. N.; Tronin, I. V.

    2017-07-01

    The full procedure of the numerical calculation of the optimized parameters of the Iguassu gas centrifuge (GC) is under discussion. The procedure consists of a few steps. On the first step the problem of a hydrodynamical flow of the gas in the rotating rotor of the GC is solved numerically. On the second step the problem of diffusion of the binary mixture of isotopes is solved. The separation power of the gas centrifuge is calculated after that. On the last step the time consuming procedure of optimization of the GC is performed providing us the maximum of the separation power. The optimization is based on the BOBYQA method exploring the results of numerical simulations of the hydrodynamics and diffusion of the mixture of isotopes. Fast convergence of calculations is achieved due to exploring of a direct solver at the solution of the hydrodynamical and diffusion parts of the problem. Optimized separative power and optimal internal parameters of the Iguassu GC with 1 m rotor were calculated using the developed approach. Optimization procedure converges in 45 iterations taking 811 minutes.

  4. Hybrid continuum–molecular modelling of multiscale internal gas flows

    International Nuclear Information System (INIS)

    Patronis, Alexander; Lockerby, Duncan A.; Borg, Matthew K.; Reese, Jason M.

    2013-01-01

    We develop and apply an efficient multiscale method for simulating a large class of low-speed internal rarefied gas flows. The method is an extension of the hybrid atomistic–continuum approach proposed by Borg et al. (2013) [28] for the simulation of micro/nano flows of high-aspect ratio. The major new extensions are: (1) incorporation of fluid compressibility; (2) implementation using the direct simulation Monte Carlo (DSMC) method for dilute rarefied gas flows, and (3) application to a broader range of geometries, including periodic, non-periodic, pressure-driven, gravity-driven and shear-driven internal flows. The multiscale method is applied to micro-scale gas flows through a periodic converging–diverging channel (driven by an external acceleration) and a non-periodic channel with a bend (driven by a pressure difference), as well as the flow between two eccentric cylinders (with the inner rotating relative to the outer). In all these cases there exists a wide variation of Knudsen number within the geometries, as well as substantial compressibility despite the Mach number being very low. For validation purposes, our multiscale simulation results are compared to those obtained from full-scale DSMC simulations: very close agreement is obtained in all cases for all flow variables considered. Our multiscale simulation is an order of magnitude more computationally efficient than the full-scale DSMC for the first and second test cases, and two orders of magnitude more efficient for the third case

  5. Modeling of Aerobrake Ballute Stagnation Point Temperature and Heat Transfer to Inflation Gas

    Science.gov (United States)

    Bahrami, Parviz A.

    2012-01-01

    A trailing Ballute drag device concept for spacecraft aerocapture is considered. A thermal model for calculation of the Ballute membrane temperature and the inflation gas temperature is developed. An algorithm capturing the most salient features of the concept is implemented. In conjunction with the thermal model, trajectory calculations for two candidate missions, Titan Explorer and Neptune Orbiter missions, are used to estimate the stagnation point temperature and the inflation gas temperature. Radiation from both sides of the membrane at the stagnation point and conduction to the inflating gas is included. The results showed that the radiation from the membrane and to a much lesser extent conduction to the inflating gas, are likely to be the controlling heat transfer mechanisms and that the increase in gas temperature due to aerodynamic heating is of secondary importance.

  6. Risk modelling of shale gas development scenarios in the Central Karoo

    CSIR Research Space (South Africa)

    Schreiner, GO

    2018-06-01

    Full Text Available The scientific assessment of shale gas development was compiled by over 200 authors and peer reviewers from around the world. Novel assessment methods were used based on the concepts of risk, scenarios and predictive landscape modelling. Three...

  7. development of a new drag coefficient model for oil and gas

    African Journals Online (AJOL)

    eobe

    approximation of experimental data for e. R , from .... dynamic conditions in order to evaluate the drag and ... based on the experimental data for multiphase, water- oil-gas flow see ... Figure 6: Comparison of measured and model prediction.

  8. A Physics-Based Starting Model for Gas Turbine Engines, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this proposal is to demonstrate the feasibility of producing an integrated starting model for gas turbine engines using a new physics-based...

  9. Pizza or Pancake? Formation Models of Gas Escape Biosignatures in Terrestrial and Martian Sediments

    Science.gov (United States)

    Bonaccorsi, R.; Fairen, A. G.; Baker, L.; McKay, C. P.; Willson, D.

    2016-05-01

    Fine-grained sedimentary hollowed structures were imaged in Gale Crater, but no biomarkers identified to support biology. Our observation-based (gas escape) terrestrial model could inform on possible martian paleoenvironments at time of formation.

  10. Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs

    Science.gov (United States)

    We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned toward conditions usually encountered in the Marce...

  11. Turbulent combustion modeling using Flamelet-Generated Manifolds for Gas Turbine applications in OpenFOAM

    NARCIS (Netherlands)

    Fancello, A.; Panek, L.; Lammel, O.; Krebs, W.; Bastiaans, R.J.M.; de Goey, L.P.H.

    2014-01-01

    The continuous interest in reducing pollutions and developing both an efficient and clean combustion system require large attention in the design requirements, especially when related to industrial gas turbine application. Although in recent years the advancements in modelling have increased

  12. Market chances for innovative natural gas applications. The determination of market potential by means of a phase model

    International Nuclear Information System (INIS)

    Hoelen, Q.E.J.J.M.; Klootwijk, M.

    2000-01-01

    Innovative applications of natural gas can increase the sale of natural gas, support energy companies in the development of commercial activities, and contribute to energy efficiency measures. The Dutch natural gas trading company Gasunie supports those developments by investigating the market potential of innovative gas appliances. Use is made of the so-called Phase Model for Market Introduction, developed by Kea Consult

  13. Application of ERAS-model and Prigogine-Flory-Patterson theory to excess molar volumes for ternary mixtures of (2-chlorobutane + butylacetate + isobutanol) at T = 298.15 K

    International Nuclear Information System (INIS)

    Khanlarzadeh, K.; Iloukhani, H.

    2011-01-01

    Highlights: → Density of ternary and three binary mixtures of (2-chlorobutane + butylacetate + isobutanol) determined. → Excess molar volume, partial molar volume and apparent molar volume were calculated. → Excess molar volume was correlated as a function of mole fraction by using the Redlich-Kister and Cibulka equation for all mixtures. → The experimental results have been used to test the applicability of the ERAS-model and PFP theory. - Abstract: Densities of the ternary mixture consisting of {2-chlorobutane (1) + butylacetate (2) + isobutanol (3)} and related binary mixtures were measured over the whole range of composition at T = 298.15 K and ambient pressure. Excess molar volumes V m E for the mixtures were derived and correlated as a function of mole fraction by using the Redlich-Kister and the Cibulka equations for binary and ternary mixtures, respectively. From the experimental data, partial molar volumes, V-bar m,i excess partial molar volumes, V-bar i E partial molar volumes at infinite dilution V-bar m,i 0 and apparent molar volumes V-bar φ,i were also calculated. For all binary mixtures over the entire range of mole fractions V m E data are positive. The experimental results of the constituted binary mixtures have been used to test the applicability of the extended real associated solution (ERAS-model) and Prigogine-Flory-Paterson (PFP) theory.

  14. Modeling and dynamic control simulation of unitary gas engine heat pump

    International Nuclear Information System (INIS)

    Zhao Yang; Haibo Zhao; Zheng Fang

    2007-01-01

    Based on the dynamic model of the gas engine heat pump (GEHP) system, an intelligent control simulation is presented to research the dynamic characteristics of the system in the heating operation. The GEHP system simulation model consists of eight models for its components including a natural gas engine, a compressor, a condenser, an expansion valve, an evaporator, a cylinder jacket heat exchanger, an exhaust gas heat exchanger and an auxiliary heater. The intelligent control model is composed of the prediction controller model and the combined controller model. The Runge-Kutta Fehlberg fourth-fifth order algorithms are used to solve the differential equations. The results show that the model is very effective in analyzing the effects of the control system, and the steady state accuracy of the intelligent control scheme is higher than that of the fuzzy controller

  15. Hydrodynamic and thermal modelling of gas-particle flow in fluidized beds

    International Nuclear Information System (INIS)

    Abdelkawi, O.S; Abdalla, A.M.; Atwan, E.F; Abdelmonem, S.A.; Elshazly, K.M.

    2009-01-01

    In this study a mathematical model has been developed to simulate two dimensional fluidized bed with uniform fluidization. The model consists of two sub models for hydrodynamic and thermal behavior of fluidized bed on which a FORTRAN program entitled (NEWFLUIDIZED) is devolved. The program is used to predict the volume fraction of gas and particle phases, the velocity of the two phases, the gas pressure and the temperature distribution for two phases. Also the program calculates the heat transfer coefficient. Besides the program predicts the fluidized bed stability and determines the optimum input gas velocity for fluidized bed to achieve the best thermal behavior. The hydrodynamic model is verified by comparing its results with the computational fluid dynamic code MFIX . While the thermal model was tested and compared by the available previous experimental correlations.The model results show good agreement with MFIX results and the thermal model of the present work confirms Zenz and Gunn equations

  16. A new model for the accurate calculation of natural gas viscosity

    OpenAIRE

    Xiaohong Yang; Shunxi Zhang; Weiling Zhu

    2017-01-01

    Viscosity of natural gas is a basic and important parameter, of theoretical and practical significance in the domain of natural gas recovery, transmission and processing. In order to obtain the accurate viscosity data efficiently at a low cost, a new model and its corresponding functional relation are derived on the basis of the relationship among viscosity, temperature and density derived from the kinetic theory of gases. After the model parameters were optimized using a lot of experimental ...

  17. A Framework for Modular Modeling of the Diesel Engine Exhaust Gas Cleaning System

    DEFF Research Database (Denmark)

    Åberg, Andreas; Hansen, Thomas Klint; Linde, Kasper

    2015-01-01

    Pollutants from diesel engines have a negative effect on urban air quality. Because of this and new legislation restricting the emission level, it is necessary to develop exhaust gas treatment systems for diesel engines that can reduce the amount of pollutants. A modular model capable of simulating...... model. Four different models in the automotive diesel exhaust gas cleaning system are presented briefly. Based on the presented methodology, it is discussed which changes are needed to the models to create a modular model of the whole catalytic system....

  18. Evaluation of reduced chemical kinetic mechanisms used for modeling mild combustion for natural gas

    Directory of Open Access Journals (Sweden)

    Hamdi Mohamed

    2009-01-01

    Full Text Available A numerical and parametric study was performed to evaluate the potential of reduced chemistry mechanisms to model natural gas chemistry including NOx chemistry under mild combustion mode. Two reduced mechanisms, 5-step and 9-step, were tested against the GRI-Mech3.0 by comparing key species, such as NOx, CO2 and CO, and gas temperature predictions in idealized reactors codes under mild combustion conditions. It is thus concluded that the 9-step mechanism appears to be a promising reduced mechanism that can be used in multi-dimensional codes for modeling mild combustion of natural gas.

  19. Numerical Analysis of Turbulent Combustion in a Model Swirl Gas Turbine Combustor

    Directory of Open Access Journals (Sweden)

    Ali Cemal Benim

    2016-01-01

    Full Text Available Turbulent reacting flows in a generic swirl gas turbine combustor are investigated numerically. Turbulence is modelled by a URANS formulation in combination with the SST turbulence model, as the basic modelling approach. For comparison, URANS is applied also in combination with the RSM turbulence model to one of the investigated cases. For this case, LES is also used for turbulence modelling. For modelling turbulence-chemistry interaction, a laminar flamelet model is used, which is based on the mixture fraction and the reaction progress variable. This model is implemented in the open source CFD code OpenFOAM, which has been used as the basis for the present investigation. For validation purposes, predictions are compared with the measurements for a natural gas flame with external flue gas recirculation. A good agreement with the experimental data is observed. Subsequently, the numerical study is extended to syngas, for comparing its combustion behavior with that of natural gas. Here, the analysis is carried out for cases without external flue gas recirculation. The computational model is observed to provide a fair prediction of the experimental data and predict the increased flashback propensity of syngas.

  20. The development of natural gas supply costs to Europe, the United States and Japan in a globalizing gas market-Model-based analysis until 2030

    International Nuclear Information System (INIS)

    Lochner, Stefan; Bothe, David

    2009-01-01

    Quickly declining natural gas reserves in some parts of the world, increasing demand in today's major gas consuming regions, the emergence of new demand centres and the globalization of natural gas markets caused by the rising importance of liquefied natural gas (LNG) are changing global gas supply structures and will continue to do so over the next decades. Applying a global gas market model, we produce a forecast for global gas supply to 2030 and determine the supplier-specific long-run average costs of gas supplied to three major consuming regions. Results for the three regions are compared and analysed with a focus on costs, supply diversification and the different roles of LNG. We find that while European and Japanese external gas supply will be less diversified in international comparison, gas can be supplied at relatively low costs due to the regions' favourable locations in geographic proximity to large gas producers. The US market's supply structure on the other hand will significantly change from its current situation. The growing dependency on LNG imports from around the world will lead to significantly higher supply costs but will also increase diversification as gas will originate from an increasing number of LNG exporting countries

  1. Application of an entry-exit tariff model to the gas transport system in Spain

    International Nuclear Information System (INIS)

    Alonso, Alejandro; Serrano, Miguel; Olmos, Luis

    2010-01-01

    Under an entry-exit gas tariff system, reservation of capacity is split into entry capacity, to transport gas from the injection points to a virtual balancing point, and exit capacity, to transport gas from the balancing point to the exit points in the system. Entry-exit tariff for gas transport systems have been recommended by the 3rd EU Energy Package, since they are cost reflective, facilitate gas trade and can provide signals for the location of gas injections or off-takes. The advisability of applying an entry-exit tariff system is discussed in this paper. Apart from this, authors propose an entry-exit tariff model and apply it to compute charges for the Spanish gas transport system in 2009. Results produced by the model are presented as coefficients which should multiply the current postal transport tariff. The paper concludes that entry-exit tariffs would be useful location signals which would result in a better use of the gas transport system in Spain. In those cases where demand exceeds available capacity, as it occurs at the congested connection with France, entry-exit tariffs could be supplemented by capacity charges at entry points resulting from auctions. (author)

  2. The generalized model of organization and planning of regional gas supply monitoring

    Directory of Open Access Journals (Sweden)

    Maria V. Shevchenko

    2015-12-01

    Full Text Available At the moment, gas is one of the most promising types of fuel in Ukraine. In this regard, the problems associated with its transportation in the regional system of gas supply are relevant. Now it is not completely solved and needs detailed study the problem of monitoring the regional gas supply system. Aim: The aim of the study is to improve the efficiency of the regional gas supply system at the expense of the organization and planning of gas transport monitoring and, in the future, the synthesis of the monitoring system of regional gas supply. Materials and Methods: The generalized model of organization and planning of monitoring regional gas suppliers were developed to achieve this goal. It allows making decisions on the organization of the monitoring system. In addition, this model makes it possible to plan under conditions of multicriteriality and uncertainty of the source data. Results: The basic criteria and constraints for solving the problem of organizing and planning the monitoring system of regional gas supply are proposed in this work. The corresponding computations were made to confirm the assumptions. The calculations were carried out in context of uncertainty of input data using a set of methods for the analysis of hierarchies, exhaustive search, as well as the methods of decision making in context of uncertainty.

  3. Numerical Modeling of Methane Leakage from a Faulty Natural Gas Well into Fractured Tight Formations.

    Science.gov (United States)

    Moortgat, Joachim; Schwartz, Franklin W; Darrah, Thomas H

    2018-03-01

    Horizontal drilling and hydraulic fracturing have enabled hydrocarbon recovery from unconventional reservoirs, but led to natural gas contamination of shallow groundwaters. We describe and apply numerical models of gas-phase migration associated with leaking natural gas wells. Three leakage scenarios are simulated: (1) high-pressure natural gas pulse released into a fractured aquifer; (2) continuous slow leakage into a tilted fractured formation; and (3) continuous slow leakage into an unfractured aquifer with fluvial channels, to facilitate a generalized evaluation of natural gas transport from faulty natural gas wells. High-pressure pulses of gas leakage into sparsely fractured media are needed to produce the extensive and rapid lateral spreading of free gas previously observed in field studies. Transport in fractures explains how methane can travel vastly different distances and directions laterally away from a leaking well, which leads to variable levels of methane contamination in nearby groundwater wells. Lower rates of methane leakage (≤1 Mcf/day) produce shorter length scales of gas transport than determined by the high-pressure scenario or field studies, unless aquifers have low vertical permeabilities (≤1 millidarcy) and fractures and bedding planes have sufficient tilt (∼10°) to allow a lateral buoyancy component. Similarly, in fractured rock aquifers or where permeability is controlled by channelized fluvial deposits, lateral flow is not sufficiently developed to explain fast-developing gas contamination (0-3 months) or large length scales (∼1 km) documented in field studies. Thus, current efforts to evaluate the frequency, mechanism, and impacts of natural gas leakage from faulty natural gas wells likely underestimate contributions from small-volume, low-pressure leakage events. © 2018, National Ground Water Association.

  4. On The Modeling Of Hybrid Aerostatic - Gas Journal Bearings

    DEFF Research Database (Denmark)

    Morosi, Stefano; Santos, Ilmar

    2010-01-01

    of a compressible fluid film journal bearing. Control forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving this equation, stiffness and damping......Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...

  5. Modelling gas migration in fractured rock. A contribution to the EU's PROGRESS project

    International Nuclear Information System (INIS)

    Humm, J.; Robinson, P.; Clark, K.

    2001-01-01

    To assess the performance of a waste repository, it is necessary to be able to predict the rates of gas generation and to understand and evaluate both the way the gas may disperse from the repository and any effects that might be associated with this dispersal. This document describes the modelling work carried out by QuantiSci on behalf of the UK Environment Agency, in conjunction with the CEC PROGRESS Project (Research into Gas Generation and Migration in Radioactive Waste Repository Systems) which has been carried out as part of the European Commission's IV th framework R and D programme. The project was under the PEGASUS (Projects on the Effects of GAS in Underground Storage facilities) umbrella. A review is provided of alternative conceptual models for the migration of gas through an initially water saturated fracture. A range of front or interface tracking methods for computing gas migration through a fracture is described: direct discretisation, marker particle, volume of fluids and level set methods. Volume of fluids methods are identified as the most appropriate approach for models of this sort. Subsequently, a description is given of the development of a model of gas injection into a single fracture in a portion of Borrowdale Volcanic Granite. The theoretical approach for the model is described in detail and the model compared to experimental results obtained for the real fracture. The experimental results of the CEC PROGRESS Project (obtained using Positron Emission Tomography) do not show particularly good agreement with the model results. However, there are strong indications that this is largely the result of uncertainties in the interpretation of the PET results. The experimental results are acknowledged to be extremely hard to interpret and the apparent negative gas thicknesses observed experimentally confirm this fact. Given the clearly critical dependence of the gas migration pathways on the aperture distribution, any discrepancies of this sort

  6. Experimental studies and model analysis of noble gas fractionation in porous media

    Science.gov (United States)

    Ding, Xin; Kennedy, B. Mack.; Evans, William C.; Stonestrom, David A.

    2016-01-01

    The noble gases, which are chemically inert under normal terrestrial conditions but vary systematically across a wide range of atomic mass and diffusivity, offer a multicomponent approach to investigating gas dynamics in unsaturated soil horizons, including transfer of gas between saturated zones, unsaturated zones, and the atmosphere. To evaluate the degree to which fractionation of noble gases in the presence of an advective–diffusive flux agrees with existing theory, a simple laboratory sand column experiment was conducted. Pure CO2 was injected at the base of the column, providing a series of constant CO2 fluxes through the column. At five fixed sampling depths within the system, samples were collected for CO2 and noble gas analyses, and ambient pressures were measured. Both the advection–diffusion and dusty gas models were used to simulate the behavior of CO2 and noble gases under the experimental conditions, and the simulations were compared with the measured depth-dependent concentration profiles of the gases. Given the relatively high permeability of the sand column (5 ´ 10−11 m2), Knudsen diffusion terms were small, and both the dusty gas model and the advection–diffusion model accurately predicted the concentration profiles of the CO2 and atmospheric noble gases across a range of CO2 flux from ?700 to 10,000 g m−2 d−1. The agreement between predicted and measured gas concentrations demonstrated that, when applied to natural systems, the multi-component capability provided by the noble gases can be exploited to constrain component and total gas fluxes of non-conserved (CO2) and conserved (noble gas) species or attributes of the soil column relevant to gas transport, such as porosity, tortuosity, and gas saturation.

  7. A hybrid model to predict the onset of gas entrainment with surface tension effects

    International Nuclear Information System (INIS)

    Saleh, W.; Bowden, R.C.; Hassan, I.G.; Kadem, L.

    2008-01-01

    The onset of gas entrainment, in a single downward oriented discharge from a stratified gas-liquid region with was modeled. The assumptions made in the development of the model reduced the problem to that of a potential flow. The discharge was modeled as a point-sink. Through use of the Kelvin-Laplace equation the model included the effects of surface tension. The resulting model required further knowledge of the flow field, specifically the dip radius of curvature prior to the onset of gas entrainment. The dip shape and size was investigated experimentally and correlations were provided to characterize the dip in terms of the discharge Froude number. The experimental correlation was used in conjunction with the theoretical model to predict the critical height. The results showed that by including surface tension effects the predicted critical height showed excellent agreement with experimental data. Surface tension reduces the critical height through the Bond number

  8. Current status of modeling fission gas behaviour in the Karlsruhe code LANGZEIT/KURZZEIT

    International Nuclear Information System (INIS)

    Vaeth, L.

    1980-12-01

    The programme LANGZEIT/KURZZEIT has been recently extended to describe intragranular bubble coalescence and volume equilibration, to model intergranular gas behaviour and transient release from closed porosity. The model is described and the results of some comparisons with transient experiments are discussed. Further necessary refinements of the model are outlined. (orig.) [de

  9. An integrated transient model for simulating the operation of natural gas transport systems

    NARCIS (Netherlands)

    Pambour, Kwabena Addo; Bolado-Lavin, Ricardo; Dijkema, Gerard P. J.

    This paper presents an integrated transient hydraulic model that describes the dynamic behavior of natural gas transport systems (GTS). The model includes sub models of the most important facilities comprising a GTS, such as pipelines, compressor stations, pressure reduction stations, underground

  10. EOS simulation and GRNN modeling of the constant volume depletion behavior of gas condensate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Elsharkawy, A.M.; Foda, S.G. [Kuwait University, Safat (Kuwait). Petroleum Engineering Dept.

    1998-03-01

    Currently, two approaches are being used to predict the changes in retrograde gas condensate composition and estimate the pressure depletion behavior of gas condensate reservoirs. The first approach uses the equation of states whereas the second uses empirical correlations. Equations of states (EOS) are poor predictive tools for complex hydrocarbon systems. The EOS needs adjustment against phase behavior data of reservoir fluid of known composition. The empirical correlation does not involve numerous numerical computations but their accuracy is limited. This study presents two general regression neural network (GRNN) models. The first model, GRNNM1, is developed to predict dew point pressure and gas compressibility at dew point using initial composition of numerous samples while the second model, GRNNM2, is developed to predict the changes in well stream effluent composition at any stages of pressure depletion. GRNNM2 can also be used to determine the initial reservoir fluid composition using dew point pressure, gas compressibility at dew point, and reservoir temperature. These models are based on analysis of 142 sample of laboratory studies of constant volume depletion (CVD) for gas condensate systems forming a total of 1082 depletion stages. The database represents a wide range of gas condensate systems obtained worldwide. The performance of the GRNN models has been compared to simulation results of the equation of state. The study shows that the proposed general regression neural network models are accurate, valid, and reliable. These models can be used to forecast CVD data needed for many reservoir engineering calculations in case laboratory data is unavailable. The GRNN models save computer time involved in EOS calculations. The study also show that once these models are properly trained they can be used to cut expenses of frequent sampling and laborious experimental CVD tests required for gas condensate reservoirs. 55 refs., 13 figs., 6 tabs.

  11. A model of gas flow with friction in a slotted seal

    Directory of Open Access Journals (Sweden)

    Joachimiak Damian

    2016-09-01

    Full Text Available The paper discusses thermodynamic phenomena accompanying the flow of gas in a slotted seal. The analysis of the gas flow has been described based on an irreversible adiabatic transformation. A model based on the equation of total enthalpy balance has been proposed. The iterative process of the model aims at obtaining such a gas temperature distribution that will fulfill the continuity equation. The model allows for dissipation of the kinetic energy into friction heat by making use of the Blasius equation to determine the friction coefficient. Within the works, experimental research has been performed of the gas flow in a slotted seal of slot height 2 mm. Based on the experimental data, the equation of local friction coefficient was modified with a correction parameter. This parameter was described with the function of pressure ratio to obtain a mass flow of the value from the experiment. The reason for taking up of this problem is the absence of high accuracy models for calculating the gas flow in slotted seals. The proposed model allows an accurate determination of the mass flow in a slotted seal based on the geometry and gas initial and final parameters.

  12. A new model for the accurate calculation of natural gas viscosity

    Directory of Open Access Journals (Sweden)

    Xiaohong Yang

    2017-03-01

    Full Text Available Viscosity of natural gas is a basic and important parameter, of theoretical and practical significance in the domain of natural gas recovery, transmission and processing. In order to obtain the accurate viscosity data efficiently at a low cost, a new model and its corresponding functional relation are derived on the basis of the relationship among viscosity, temperature and density derived from the kinetic theory of gases. After the model parameters were optimized using a lot of experimental data, the diagram showing the variation of viscosity along with temperature and density is prepared, showing that: ① the gas viscosity increases with the increase of density as well as the increase of temperature in the low density region; ② the gas viscosity increases with the decrease of temperature in high density region. With this new model, the viscosity of 9 natural gas samples was calculated precisely. The average relative deviation between these calculated values and 1539 experimental data measured at 250–450 K and 0.10–140.0 MPa is less than 1.9%. Compared with the 793 experimental data with a measurement error less than 0.5%, the maximum relative deviation is less than 0.98%. It is concluded that this new model is more advantageous than the previous 8 models in terms of simplicity, accuracy, fast calculation, and direct applicability to the CO2 bearing gas samples.

  13. Dynamic Modeling and Analysis of an Industrial Gas Suspension Absorber for Flue Gas Desulfurization

    DEFF Research Database (Denmark)

    Cignitti, Stefano; Mansouri, Seyed Soheil; Sales-Cruz, Mauricio

    2016-01-01

    parameters were fitted to operational data from a real cement plant. A detailed statistical analysis of the parameter estimation procedure was performed, and the confidence intervals for estimated kinetic parameters were calculated. The model and reaction rate expression prediction ability was tested using...... another plant data set. It was verified that in spite of the simplicity of the model, very good prediction of industrial behavior was obtained. Furthermore, the dynamic analysis of the system was performed by carrying out open-loop and closed-loop simulations to verify plant dynamics. Therefore, a simple...... dynamic model with a reaction rate expression that is simple and efficient to use to predict the dynamics of GSA process was proposed in this work....

  14. Parameter estimation for LLDPE gas-phase reactor models

    Directory of Open Access Journals (Sweden)

    G. A. Neumann

    2007-06-01

    Full Text Available Product development and advanced control applications require models with good predictive capability. However, in some cases it is not possible to obtain good quality phenomenological models due to the lack of data or the presence of important unmeasured effects. The use of empirical models requires less investment in modeling, but implies the need for larger amounts of experimental data to generate models with good predictive capability. In this work, nonlinear phenomenological and empirical models were compared with respect to their capability to predict the melt index and polymer yield of a low-density polyethylene production process consisting of two fluidized bed reactors connected in series. To adjust the phenomenological model, the optimization algorithms based on the flexible polyhedron method of Nelder and Mead showed the best efficiency. To adjust the empirical model, the PLS model was more appropriate for polymer yield, and the melt index needed more nonlinearity like the QPLS models. In the comparison between these two types of models better results were obtained for the empirical models.

  15. A quantitative approach to developing more mechanistic gas exchange models for field grown potato

    DEFF Research Database (Denmark)

    Ahmadi, Seyed Hamid; Andersen, Mathias Neumann; Poulsen, Rolf Thostrup

    2009-01-01

    In this study we introduce new gas exchange models that are developed under natural conditions of field grown potato. The new models could explain about 85% of the stomatal conductance variations, which was much higher than the well-known gas exchange models such as the Ball-Berry model [Ball...... of chemical and hydraulic signalling on stomatal conductance as exp(-β[ABA])exp(-δ|ψ|) in which [ABA] and |ψ| are xylem ABA concentration and absolute value of leaf or stem water potential. In this study we found that stem water potential could be a very reliable indicator of how plant water status affects...

  16. Using physical and numerical models to study possibilities of storing natural gas in horizontal layers

    Energy Technology Data Exchange (ETDEWEB)

    Boucher, M; Marrast, j

    1969-11-01

    The absence of suitable structures in some regions has led Gaz de France to investigate the storage of natural gas in horizontal layers. Research aimed at completing work done in this field by Soviet researchers has been carried out at the Institut Francais du Petrole using physical and numerical models together with computing. This research included an examination of storage stability, of how the effective volume of gas evolved during different cycles, of how the gas bubble migrates under the effect of a slight dip, and of the influence of instabilities. The possibility of storing gas in horizontal or sub-horizontal layers was thus justified from a theoretical viewpoint. When the time comes to make a decision concerning the creation of such a storage area, it is the economic factor that will be preponderant. The effective volume of recoverable gas has turned out to depend to a large extent on the thickness of the layer. (12 refs.)

  17. Droplet model of pyrocarbon deposition from the gas phase. [HTGR

    Energy Technology Data Exchange (ETDEWEB)

    Linke, J; Koizlik, K; Luhleich, H; Nickel, H

    1975-01-15

    Based on extensive earlier work a model has been developed to describe the formation of carbon by pyrolysis of gaseous hydrocarbons. One of the central statements of this model is the assumption of the existence of a quasi liquid carbon phase during deposition process.This model is described and is discussed as are the consequences for the material properties and structural parameters which arise from it. To review the droplet model, statically deposited pyrocarbon is examined by characterization methods suitable to analyze just these structural parameters.The results prove the model conceptions to be realistic.

  18. Androgen excess: Investigations and management.

    Science.gov (United States)

    Lizneva, Daria; Gavrilova-Jordan, Larisa; Walker, Walidah; Azziz, Ricardo

    2016-11-01

    Androgen excess (AE) is a key feature of polycystic ovary syndrome (PCOS) and results in, or contributes to, the clinical phenotype of these patients. Although AE will contribute to the ovulatory and menstrual dysfunction of these patients, the most recognizable sign of AE includes hirsutism, acne, and androgenic alopecia or female pattern hair loss (FPHL). Evaluation includes not only scoring facial and body terminal hair growth using the modified Ferriman-Gallwey method but also recording and possibly scoring acne and alopecia. Moreover, assessment of biochemical hyperandrogenism is necessary, particularly in patients with unclear or absent hirsutism, and will include assessing total and free testosterone (T), and possibly dehydroepiandrosterone sulfate (DHEAS) and androstenedione, although these latter contribute limitedly to the diagnosis. Assessment of T requires use of the highest quality assays available, generally radioimmunoassays with extraction and chromatography or mass spectrometry preceded by liquid or gas chromatography. Management of clinical hyperandrogenism involves primarily either androgen suppression, with a hormonal combination contraceptive, or androgen blockade, as with an androgen receptor blocker or a 5α-reductase inhibitor, or a combination of the two. Medical treatment should be combined with cosmetic treatment including topical eflornithine hydrochloride and short-term (shaving, chemical depilation, plucking, threading, waxing, and bleaching) and long-term (electrolysis, laser therapy, and intense pulse light therapy) cosmetic treatments. Generally, acne responds to therapy relatively rapidly, whereas hirsutism is slower to respond, with improvements observed as early as 3 months, but routinely only after 6 or 8 months of therapy. Finally, FPHL is the slowest to respond to therapy, if it will at all, and it may take 12 to 18 months of therapy for an observable response. Copyright © 2016. Published by Elsevier Ltd.

  19. Beyond phthalates: Gas phase concentrations and modeled gas/particle distribution of modern plasticizers

    Energy Technology Data Exchange (ETDEWEB)

    Schossler, Patricia [Fraunhofer WKI, Department of Material Analysis and Indoor Chemistry, Bienroder Weg 54E, D-38108 Braunschweig (Germany); Institute of Environmental and Sustainable Chemistry, Technische Universitaet Braunschweig, Hagenring 30, D-38106 Braunschweig (Germany); Schripp, Tobias, E-mail: tobias.schripp@wki.fraunhofer.de [Fraunhofer WKI, Department of Material Analysis and Indoor Chemistry, Bienroder Weg 54E, D-38108 Braunschweig (Germany); Salthammer, Tunga [Fraunhofer WKI, Department of Material Analysis and Indoor Chemistry, Bienroder Weg 54E, D-38108 Braunschweig (Germany); Bahadir, Muefit [Institute of Environmental and Sustainable Chemistry, Technische Universitaet Braunschweig, Hagenring 30, D-38106 Braunschweig (Germany)

    2011-09-01

    The ongoing health debate about polymer plasticizers based on the esters of phthalic acid, especially di(2-ethylhexyl) phthalate (DEHP), has caused a trend towards using phthalates of lower volatility such as diisononyl phthalate (DINP) and towards other acid esters, such as adipates, terephthalates, citrates, etc. Probably the most important of these so-called 'alternative' plasticizers is diisononyl cyclohexane-1,2-dicarboxylate (DINCH). In the indoor environment, the continuously growing market share of this compound since its launch in 2002 is inter alia apparent from the increasing concentration of DINCH in settled house dust. From the epidemiological point of view there is considerable interest in identifying how semi-volatile organic compounds (SVOCs) distribute in the indoor environment, especially in air, airborne particles and sedimented house dust. This, however, requires reliable experimental concentration data for the different media and good measurements or estimates of their physical and chemical properties. This paper reports on air concentrations for DINP, DINCH, diisobutyl phthalate (DIBP), diisobutyl adipate (DIBA), diisobutyl succinate (DIBS) and diisobutyl glutarate (DIBG) from emission studies in the Field and Laboratory Emission Cell (FLEC). For DINP and DINCH it took about 50 days to reach the steady-state value: for four months no decay in the concentration could be observed. Moreover, vapor pressures p{sub 0} and octanol-air partitioning coefficients K{sub OA} were obtained for 37 phthalate and non-phthalate plasticizers from two different algorithms: EPI Suite and SPARC. It is shown that calculated gas/particle partition coefficients K{sub p} and fractions can widely differ due to the uncertainty in the predicted p{sub 0} and K{sub OA} values. For most of the investigated compounds reliable experimental vapor pressures are not available. Rough estimates can be obtained from the measured emission rate of the pure compound in a

  20. A methodology to model flow-thermals inside a domestic gas oven

    International Nuclear Information System (INIS)

    Mistry, Hiteshkumar; Ganapathisubbu, S.; Dey, Subhrajit; Bishnoi, Peeush; Castillo, Jose Luis

    2011-01-01

    In this paper, the authors describe development of a CFD based methodology to evaluate performance of a domestic gas oven. This involves modeling three-dimensional, unsteady, forced convective flow field coupled with radiative participating media. Various strategies for capturing transient heat transfer coupled with mixed convection flow field are evaluated considering the trade-off between computational time and accuracy of predictions. A new technique of modeling