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Sample records for homogeneous conditions etude

  1. Thermodynamic study on the complexation of Trivalent actinide and lanthanide cation by N-donor ligands in homogeneous conditions; Etude thermodynamique de la complexation des ions actinide (III) et lanthanide (III) par des ligands polyazotes en milieu homogene

    Energy Technology Data Exchange (ETDEWEB)

    Miguirditchian, M

    2004-07-01

    Polydentate N-donor ligands, alone or combined with a synergic acid, may selectively extract minor actinides(III) from lanthanide(III) ions, allowing to develop separation processes of long-live radioelements. The aim of the researches carried out during this thesis was to better understand the chemical mechanisms of the complexation of f-elements by Adptz, a tridentate N-donor ligand, in homogeneous conditions. A thermodynamic approach was retained in order to estimate, from an energetic point of view, the influence of the different contributions to the reaction, and to acquire a complete set of thermodynamic data on this reaction. First, the influence of the nature of the cation on the thermodynamics was considered. The stability constants of the 1/1 complexes were systematically determined by UV-visible spectrophotometry for every lanthanide ion (except promethium) and for yttrium in a mixed solvent methanol/water in volume proportions 75/25%. The thermodynamic parameters ({delta}H{sup 0} {delta}{sup S}) of complexation were estimated by the van't Hoff method and by micro-calorimetry. The trends of the variations across the lanthanide series are compared with similar studies. The same methods were applied to the study of three actinide(III) cations: plutonium, americium and curium. The comparison of these values with those obtained for the lanthanides highlights the increase of stability of these complexes by a factor of 20 in favor of the actinide cations. This gap is explained by a more exothermic reaction and is associated, in the data interpretation, to a higher covalency of the actinide(III)-nitrogen bond. Then, the influence of the change of solvent composition on the thermodynamic of complexation was studied. The thermodynamic parameters of the complexation of europium(III) by Adptz were determined for several fractions of methanol. The stability of the complex formed increases with the percentage of methanol in the mixed solvent, owing to an

  2. Etude de l'equation de Navier-Stokes stochastique non homogene

    African Journals Online (AJOL)

    Prp;,u + Prp(uV)u-Pr~u Prpf (4). Cette equation jointe a la condition (S) peut se substituer au systeme d'equations ((1 )-(2)). u~0e~. ~. Si la force exterieure est soumise a une perturbation stochastique, alors on considere l'equation stochastique suivante: Prpdu.+ (Prp(uV)u-Prv.Au)dt=Prpfdt. +PrpdG. Dans notte 6tude, cette ...

  3. Homogenized boundary conditions and resonance effects in Faraday cages

    OpenAIRE

    Hewett, DP; Hewitt, IJ

    2016-01-01

    We present a mathematical study of two-dimensional electrostatic and electromagnetic shielding by a cage of conducting wires (the so-called `Faraday cage e ect'). Taking the limit as the number of wires in the cage tends to in nity we use the asymptotic method of multiple scales to derive continuum models for the shielding, involving homogenized boundary conditions on an e ective cage boundary. We show how the resulting models depend on key cage parameters such as the...

  4. Homogenized boundary conditions and resonance effects in Faraday cages

    Science.gov (United States)

    Hewitt, I. J.

    2016-01-01

    We present a mathematical study of two-dimensional electrostatic and electromagnetic shielding by a cage of conducting wires (the so-called ‘Faraday cage effect’). Taking the limit as the number of wires in the cage tends to infinity, we use the asymptotic method of multiple scales to derive continuum models for the shielding, involving homogenized boundary conditions on an effective cage boundary. We show how the resulting models depend on key cage parameters such as the size and shape of the wires, and, in the electromagnetic case, on the frequency and polarization of the incident field. In the electromagnetic case, there are resonance effects, whereby at frequencies close to the natural frequencies of the equivalent solid shell, the presence of the cage actually amplifies the incident field, rather than shielding it. By appropriately modifying the continuum model, we calculate the modified resonant frequencies, and their associated peak amplitudes. We discuss applications to radiation containment in microwave ovens and acoustic scattering by perforated shells. PMID:27279775

  5. Homogenized boundary conditions and resonance effects in Faraday cages

    Science.gov (United States)

    Hewett, D. P.; Hewitt, I. J.

    2016-05-01

    We present a mathematical study of two-dimensional electrostatic and electromagnetic shielding by a cage of conducting wires (the so-called `Faraday cage effect'). Taking the limit as the number of wires in the cage tends to infinity, we use the asymptotic method of multiple scales to derive continuum models for the shielding, involving homogenized boundary conditions on an effective cage boundary. We show how the resulting models depend on key cage parameters such as the size and shape of the wires, and, in the electromagnetic case, on the frequency and polarization of the incident field. In the electromagnetic case, there are resonance effects, whereby at frequencies close to the natural frequencies of the equivalent solid shell, the presence of the cage actually amplifies the incident field, rather than shielding it. By appropriately modifying the continuum model, we calculate the modified resonant frequencies, and their associated peak amplitudes. We discuss applications to radiation containment in microwave ovens and acoustic scattering by perforated shells.

  6. Study of the fluctuations in neutrons density in a homogeneous plutonium pile; Etude de la fluctuation de la population de neutrons sur une pile homogene au plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Clouet d' Orval, C; Deilgat, E; Labbe, J; Molbert, M; Tachon, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1962-07-01

    The variations in neutron density in the centre of a reactor core are subjected to a statistical fluctuation phenomenon. Because of the correlations existing between the neutrons, their distribution does not follow Poisson's law. It diverges from it by a quantity depending on various parameter such as the lifetime and the effective fraction of the slowed-down neutrons. Experiments have been carried out designed to demonstrate this divergence and also, more particularly, the correlation between unaffected and slowed-down neutrons; these have been carried out with the help of the reactor 'Proserpine', a critical homogeneous plutonium assembly. (author) [French] L'evolution de la population neutronique au sein d'un milieu multiplicateur est soumise a un phenomene de fluctuations statistiques. En raison des correlations qui existent entre les neutrons, leur distribution ne suit pas une loi de Poisson. Elle s'en ecarte d'une quantite qui depend de divers parametres tels que le temps de vie, la proportion effective des neutrons retardes. Des experiences, destinees a mettre en evidence cet ecart, et plus particulierement les correlations entre neutrons prompts et neutrons retardes, ont ete realisees a l'aide de la pile 'Proserpine', experience critique homogene au plutonium. (auteur)

  7. Neutron thermalization in absorbing infinite homogeneous media: theoretical methods; Methodes theoriques pour l'etude de la thermalisation des neutrons dans les milieux absorbants infinis et homogenes

    Energy Technology Data Exchange (ETDEWEB)

    Cadilhac, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-11-15

    After a general survey of the theory of neutron thermalization in homogeneous media, one introduces, through a proper formulation, a simplified model generalizing both the Horowitz model (generalized heavy free gas approximation) and the proton gas model. When this model is used, the calculation of spectra is reduced to the solution of linear second order differential equations. Since it depends on two arbitrary functions, the model gives a good approximation of any usual moderator for reactor physics purposes. The choice of these functions is discussed from a theoretical point of view; a method based on the consideration of the first two moments of the scattering law is investigated. Finally, the possibility of discriminating models by using experimental informations is considered. (author) [French] Apres un passage en revue de generalites sur la thermalisation des neutrons dans les milieux homogenes, on developpe un formalisme permettant de definir et d'etudier un modele simplifie de thermaliseur. Ce modele generalise l'approximation proposee par J. HOROWITZ (''gaz lourd generalise'') et comporte comme cas particulier le modele ''hydrogene gazeux monoatomique''. Il ramene le calcul des spectres a la resolution d'equations differentielles lineaires du second ordre. Il fait intervenir deux fonctions arbitraires, ce qui lui permet de representer les thermaliseurs usuels de facon satisfaisante pour les besoins de la physique des reacteurs. L'ajustement theorique de ces fonctions est discute; on etudie une methode basee sur la consideration des deux premiers moments de la loi de diffusion. On envisage enfin la possibilite de discriminer les modeles d'apres des renseignements d'origine experimentale. (auteur)

  8. Etude theorique et experimentale des evaporateurs de dioxyde de carbone operant dans des conditions de givrage

    Science.gov (United States)

    Bendaoud, Adlane Larbi

    Les evaporateurs de refrigeration sont surtout du type tube a ailettes, appeles serpentins, et fonctionnent dans l'une des conditions suivantes: seche, humide ou avec formation de givre. Il a ete demontre que la formation du givre sur la paroi exterieure de l'echangeur engendre une surconsommation energetique a cause des operations de degivrage puisque 15 a 20% seulement de la chaleur produite sert au degivrage tandis que le reste est dissipee dans l'environnement [1]. Avec l'avenement des nouveaux refrigerants, moins nocifs envers l'environnement, l'industrie du froid se trouve penalisee du fait que peu ou pas de composantes mecaniques (compresseur, pompe, echangeur...etc.) adaptees sont disponibles [3]. Il s'agit pour la communaute des frigoristes de combler ce retard technologique en redeveloppant ces composantes mecaniques afin qu'elles soient adaptees aux nouveaux refrigerants. Dans cette optique, et afin de mieux comprendre le comportement thermique des evaporateurs au CO2 fonctionnant dans des conditions seches, qu'un groupe de chercheurs du CanmetENERGIE avaient lance, en 2000, un programme de R & D. Dans le cadre de programme un outil de simulation des evaporateurs au CO2 a ete developpe et un banc d'essai contenant une boucle secondaire de refrigeration utilisant le CO2 comme refrigerant a ete construit. Comme continuite de ce travail de recherche, en 2006 ce meme groupe de recherche a lance un nouveau projet qui consiste a faire une etude theorique et experimentale des evaporateurs au CO2 operants dans des conditions de givrage. Et, c'est exactement dans le cadre de ce projet que se positionne ce travail de these. Ce travail de recherche a ete entrepris pour mieux comprendre le comportement thermique et hydrodynamique des serpentins fonctionnant dans des conditions de givrage, l'effet des circuits de refrigerant ainsi que celui des parametres geometriques et d'operation. Pour cela, un travail theorique supporte par une etude experimentale a ete effectue

  9. Experimental determination of the boundary condition for diffuse photons in a homogeneous turbid medium

    International Nuclear Information System (INIS)

    Everitt, David L.; Zhu, Tuo; Zhu, H.-M.; Zhu, X. D.

    2000-01-01

    We present a simple experimental method that permits an empirical determination of the effective boundary condition and the extrapolated end point for the diffuse photon density in a homogeneous turbid medium. (c) 2000 Optical Society of America

  10. Study of the cyclotron operating conditions; Etude des conditions de fonctionnement du cyclotron

    Energy Technology Data Exchange (ETDEWEB)

    Debraine, P; Bariaud, A; Goldschmidt-Clermont, Y

    1948-12-01

    This work is a detailed study of the operating conditions of the cyclotron. It analyzes the behaviour of the particles from their first accelerations to their arrival on an external target. Calculations were performed using relativistic formulations in order to make the results usable without any energy level restriction. The obtained results supply some numerical elements for a cyclotron pre-determination and allow a satisfactory visualization of the real phenomena taking place during the accelerations. The shape of the phase change during the successive accelerations has been obtained for a given magnetic field configuration with respect to the operating frequency, to the magnetic field value in the center, and to the accelerating voltage between the dees. Taking into account the limitations due to the accelerating and focussing conditions, the usable phase interval has been determined with respect to the characteristic operating parameters. The study of this phase interval with respect to the accelerating voltage, on the one hand, and with respect to the frequency or to the center magnetic field, on the other hand, has permitted to find again two facts experimentally observed: voltage threshold and dissymmetry of the response curve. The study of radial and axial oscillations has shown the existence of precession phenomena and indicates a maximum limit for the magnetic field variation in order to avoid the disturbances due to oscillations coupling. The study of the ion beam envelope inside the chamber with respect to the initial phases has permitted to determine the optimum shape of the dees and the height of the deflecting channel. Moreover, the influence of various parameters on the ion beam efficiency can be shown using an ideal source. The study of the passing conditions inside the deflecting channel has shown the influence of the separation sheet, has given the dimensions to foresee for the deflecting channel, and has indicated the way to follow to obtain

  11. Rigorous homogenization of a Stokes-Nernst-Planck-Poisson problem for various boundary conditions

    NARCIS (Netherlands)

    Ray, N.; Muntean, A.; Knabner, P.

    2011-01-01

    We perform the periodic homogenization (i. e. e ¿ 0) of the non-stationary Stokes-Nernst-Planck-Poisson system using two-scale convergence, where e is a suitable scale parameter. The objective is to investigate the influence of different boundary conditions and variable choices of scaling in e of

  12. Comparative study of heterogeneous and homogeneous LMFBR cores in some accident conditions

    International Nuclear Information System (INIS)

    Renard, A.; Evrard, G.

    1978-01-01

    An heterogeneous design and a homogeneous one of a LMFBR core with the same power and similar dimensions are compared from the safety point-of-view. The comparison is performed for several accident conditions, such as Loss-of-Flow and Transient Overpower, with the same failure criteria and model assumptions for both cores. Qualitative trends are deduced from the behaviour of the core designs in the investigated transient conditions. (author)

  13. Study of microinstabilities due to an anisotropic velocity distribution function of the particles of a homogeneous plasma; Etude des microinstabilities liees a l'anisotropie de la fonction de distribution des vitesses des particules d'un plasma homogene

    Energy Technology Data Exchange (ETDEWEB)

    Hennion, F [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1966-06-01

    A study is made of instabilities in a plasma with an ion velocity distribution function of the form: f{sub oi} = 1 / (2*{pi}*{alpha}{sub p}e{sub i}*{alpha}{sub p}a{sub i}) * {lambda}({nu}{sub p}e - {alpha}{sub p}e{sub i}) * e{sup -}(v{sub pa2}/{alpha}{sub pai2}). The plasma is assumed to have finite dimensions limited by infinitely conductive boundary surfaces. A theoretical and numerical analysis of marginal stability locates the regions of stability as a function of several parameters; i.e. plasma length, ion anisotropy ({tau}) and electron temperature (T{sub e}). A limiting plasma length is found, below which the plasma is stable regardless of its density. For the parameters of the injection experiment M.M.I.I. at Fontenay-aux-roses it is found that the type of instabilities studied here should not occur. (author) [French] L'etude est faite en choisissant une fonction de distribution des ions de la forme f{sub oi} = 1 / (2*{pi}*{alpha}{sub p}e{sub i}*{alpha}{sub p}a{sub i}) * {lambda}({nu}{sub p}e - {alpha}{sub p}e{sub i}) * e{sup -}(v{sub pa2}/{alpha}{sub pai2}) et en supposant une conductivite infinie sur les limites du plasma de dimensions finies. L'etude theorique et numerique de la stabilite marginale determine les domaines de stabilite qui sont etudies en fonction de plusieurs parametres: longueur du plasma, anisotropie des ions ({tau}), temperature electronique (T{sub e}). Il apparait une longueur limite du plasma au-dessous de laquelle le plasma est stable, independemment de la densite. L'application faite avec les valeurs des parametres de l'experience d'injection M.M.I.I, a Fontenay-aux-Roses permet de conclure a la non existence dans cet appareil du type d'instabilite etudie ici. (auteur)

  14. Homogenization of the evolution Stokes equation in a perforated domain with a stochastic Fourier boundary condition

    KAUST Repository

    Bessaih, Hakima

    2015-04-01

    The evolution Stokes equation in a domain containing periodically distributed obstacles subject to Fourier boundary condition on the boundaries is considered. We assume that the dynamic is driven by a stochastic perturbation on the interior of the domain and another stochastic perturbation on the boundaries of the obstacles. We represent the solid obstacles by holes in the fluid domain. The macroscopic (homogenized) equation is derived as another stochastic partial differential equation, defined in the whole non perforated domain. Here, the initial stochastic perturbation on the boundary becomes part of the homogenized equation as another stochastic force. We use the twoscale convergence method after extending the solution with 0 in the holes to pass to the limit. By Itô stochastic calculus, we get uniform estimates on the solution in appropriate spaces. In order to pass to the limit on the boundary integrals, we rewrite them in terms of integrals in the whole domain. In particular, for the stochastic integral on the boundary, we combine the previous idea of rewriting it on the whole domain with the assumption that the Brownian motion is of trace class. Due to the particular boundary condition dealt with, we get that the solution of the stochastic homogenized equation is not divergence free. However, it is coupled with the cell problem that has a divergence free solution. This paper represents an extension of the results of Duan and Wang (Comm. Math. Phys. 275:1508-1527, 2007), where a reaction diffusion equation with a dynamical boundary condition with a noise source term on both the interior of the domain and on the boundary was studied, and through a tightness argument and a pointwise two scale convergence method the homogenized equation was derived. © American Institute of Mathematical Sciences.

  15. Starch nanoparticles resulting from combination of dry heating under mildly acidic conditions and homogenization.

    Science.gov (United States)

    Kim, Jong Hun; Kim, Jiyeon; Park, Eun Young; Kim, Jong-Yea

    2017-07-15

    To modify starch granular structure, normal maize starch was subjected to dry heating with various amounts of 1.0M HCl (1.2, 1.4 or 1.6mL) and different treatment times (2, 4 or 8h). For all reaction conditions, at least 80% of the starch substance was recovered, and amylose and amylopectin B1 chains were preferentially cleaved. As acidic condition and/or treatment time increased, the treated granules were readily fragmented by homogenization. The treatment appeared to alter short-range crystalline structure (FT-IR), but long-range crystalline structure (XRD) remained intact. Homogenization for 60min fragmented the treated starch granules (subjected to reaction condition of 1.4mL/4h, 1.6mL/2h, and 1.6mL/4h) into nanoparticles consisting of individual platelet-like and spherical particles with diameters less than 100nm. However, the fragmentation caused obvious damage in the long-range crystalline structure of starch nanoparticles, while the short-range chain associations remained relatively intact. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Homogenization of Winkler-Steklov spectral conditions in three-dimensional linear elasticity

    Science.gov (United States)

    Gómez, D.; Nazarov, S. A.; Pérez, M. E.

    2018-04-01

    We consider a homogenization Winkler-Steklov spectral problem that consists of the elasticity equations for a three-dimensional homogeneous anisotropic elastic body which has a plane part of the surface subject to alternating boundary conditions on small regions periodically placed along the plane. These conditions are of the Dirichlet type and of the Winkler-Steklov type, the latter containing the spectral parameter. The rest of the boundary of the body is fixed, and the period and size of the regions, where the spectral parameter arises, are of order ɛ . For fixed ɛ , the problem has a discrete spectrum, and we address the asymptotic behavior of the eigenvalues {β _k^ɛ }_{k=1}^{∞} as ɛ → 0. We show that β _k^ɛ =O(ɛ ^{-1}) for each fixed k, and we observe a common limit point for all the rescaled eigenvalues ɛ β _k^ɛ while we make it evident that, although the periodicity of the structure only affects the boundary conditions, a band-gap structure of the spectrum is inherited asymptotically. Also, we provide the asymptotic behavior for certain "groups" of eigenmodes.

  17. Upgrading the lubricity of bio-oil via homogeneous catalytic esterification under vacuum distillation conditions

    International Nuclear Information System (INIS)

    Xu, Yufu; Zheng, Xiaojing; Peng, Yubin; Li, Bao; Hu, Xianguo; Yin, Yanguo

    2015-01-01

    In order to accelerate the application of bio-oil in the internal combustion engines, homogeneous catalytic esterification technology under vacuum distillation conditions was used to upgrade the crude bio-oil. The lubricities of the crude bio-oil (BO) and refined bio-oil with homogeneous catalytic esterification (RBO hce ) or refined bio-oil without catalyst but with distillation operation (RBO wc ) were evaluated by a high frequency reciprocating test rig according to the ASTM D 6079 standard. The basic physiochemical properties and components of the bio-oils were analyzed. The surface morphology, contents and chemical valence of active elements on the worn surfaces were investigated by scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy, respectively. The results show that RBO hce has better lubricities than those of BO, but RBO wc has worse lubricities than those of BO. The tribological mechanisms of the bio-oils are attributed to the combined actions of lubricating films and factors that will break the film. Compared with BO, plenty of phenols in RBO wc results in corrosion of the substrate and destroys the integrity of the lubricating films, which is responsible for its corrosive wear. However, more esters and alkanes in RBO hce contribute to forming a complete boundary lubricating film on the rubbed surfaces which result in its excellent antifriction and antiwear properties. - Highlights: • Refined bio-oil was prepared through homogeneous catalytic esterification technology. • Properties of the bio-oils before and after refining were assessed by HFRR. • Refined bio-oil showed better lubricities than crude bio-oil. • More esters and alkanes in refined bio-oil contributed to forming superior boundary lubrication

  18. Gravity-driven, dry granular flows over a loose bed in stationary and homogeneous conditions

    Science.gov (United States)

    Meninno, Sabrina; Armanini, Aronne; Larcher, Michele

    2018-02-01

    Flows involving solid particulates have been widely studied in recent years, but their dynamics are still a complex issue to model because they strongly depend on the interaction with the boundary conditions. We report on laboratory investigations regarding homogeneous and steady flows of identical particles over a loose bed in a rectangular channel. Accurate measurements were carried out through imaging techniques to estimate profiles of the mean velocity, solid concentration, and granular temperature for a large set of flow rates and widths. Vertical and transversal structures observed in the flow change as interparticle interactions become more collisional, and they depend on the bottom over which the flow develops. The lateral confinement has a remarkable effect on the flow, especially for narrow channels compared with the grain size, and a hydraulic analogy is able to show how the walls influence the mechanisms of friction and energy dissipation.

  19. Effects of sulfur dioxide and nitric oxide on mercury oxidation and reduction under homogeneous conditions

    Energy Technology Data Exchange (ETDEWEB)

    Yongxin Zhao; Michael D. Mann; Edwin S. Olson; John H. Pavlish; Grant E. Dunham [University of North Dakota, Grand Forks, ND (United States). Department of Chemical Engineering

    2006-05-15

    This paper is particularly related to elemental mercury (Hg{sup 0}) oxidation and divalent mercury (Hg{sup 2+} reduction under simulated flue gas conditions in the presence of nitric oxide (NO) and sulfur dioxide (SO{sub 2}). As a powerful oxidant and chlorinating reagent, Cl{sub 2} has the potential for Hg oxidation. However, the detailed mechanism for the interactions, especially among chlorine (Cl)-containing species, SO{sub 2}, NO, as well as H{sub 2}O, remains ambiguous. Research described in this paper therefore focused on the impacts of SO{sub 2} and NO on Hg{sup 0} oxidation and Hg{sup 2+} reduction with the intent of unraveling unrecognized interactions among Cl species, SO{sub 2}, and NO most importantly in the presence of H{sub 2}O. The experimental results demonstrated that SO{sub 2} and NO had pronounced inhibitory effects on Hg{sup 0} oxidation at high temperatures when H{sub 2}O was also present in the gas blend. Such a demonstration was further confirmed by the reduction of Hg{sup 2+} back into its elemental form. Data revealed that SO{sub 2} and NO were capable of promoting homogeneous reduction of Hg{sup 2+} to Hg{sup 0} with H{sub 2}O being present. However, the above inhibition or promotion disappeared under homogeneous conditions when H{sub 2}O was removed from the gas blend. 23 refs., 8 figs.

  20. Water oxidation catalysis with nonheme iron complexes under acidic and basic conditions: homogeneous or heterogeneous?

    Science.gov (United States)

    Hong, Dachao; Mandal, Sukanta; Yamada, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Llobet, Antoni; Fukuzumi, Shunichi

    2013-08-19

    Thermal water oxidation by cerium(IV) ammonium nitrate (CAN) was catalyzed by nonheme iron complexes, such as Fe(BQEN)(OTf)2 (1) and Fe(BQCN)(OTf)2 (2) (BQEN = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine, BQCN = N,N'-dimethyl-N,N'-bis(8-quinolyl)cyclohexanediamine, OTf = CF3SO3(-)) in a nonbuffered aqueous solution; turnover numbers of 80 ± 10 and 20 ± 5 were obtained in the O2 evolution reaction by 1 and 2, respectively. The ligand dissociation of the iron complexes was observed under acidic conditions, and the dissociated ligands were oxidized by CAN to yield CO2. We also observed that 1 was converted to an iron(IV)-oxo complex during the water oxidation in competition with the ligand oxidation. In addition, oxygen exchange between the iron(IV)-oxo complex and H2(18)O was found to occur at a much faster rate than the oxygen evolution. These results indicate that the iron complexes act as the true homogeneous catalyst for water oxidation by CAN at low pHs. In contrast, light-driven water oxidation using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and S2O8(2-) as a sacrificial electron acceptor was catalyzed by iron hydroxide nanoparticles derived from the iron complexes under basic conditions as the result of the ligand dissociation. In a buffer solution (initial pH 9.0) formation of the iron hydroxide nanoparticles with a size of around 100 nm at the end of the reaction was monitored by dynamic light scattering (DLS) in situ and characterized by X-ray photoelectron spectra (XPS) and transmission electron microscope (TEM) measurements. We thus conclude that the water oxidation by CAN was catalyzed by short-lived homogeneous iron complexes under acidic conditions, whereas iron hydroxide nanoparticles derived from iron complexes act as a heterogeneous catalyst in the light-driven water oxidation reaction under basic conditions.

  1. Unified treatment of microscopic boundary conditions and efficient algorithms for estimating tangent operators of the homogenized behavior in the computational homogenization method

    Science.gov (United States)

    Nguyen, Van-Dung; Wu, Ling; Noels, Ludovic

    2017-03-01

    This work provides a unified treatment of arbitrary kinds of microscopic boundary conditions usually considered in the multi-scale computational homogenization method for nonlinear multi-physics problems. An efficient procedure is developed to enforce the multi-point linear constraints arising from the microscopic boundary condition either by the direct constraint elimination or by the Lagrange multiplier elimination methods. The macroscopic tangent operators are computed in an efficient way from a multiple right hand sides linear system whose left hand side matrix is the stiffness matrix of the microscopic linearized system at the converged solution. The number of vectors at the right hand side is equal to the number of the macroscopic kinematic variables used to formulate the microscopic boundary condition. As the resolution of the microscopic linearized system often follows a direct factorization procedure, the computation of the macroscopic tangent operators is then performed using this factorized matrix at a reduced computational time.

  2. Homogeneity and heterogeneity in amylase production by Bacillus subtilis under different growth conditions.

    Science.gov (United States)

    Ploss, Tina N; Reilman, Ewoud; Monteferrante, Carmine G; Denham, Emma L; Piersma, Sjouke; Lingner, Anja; Vehmaanperä, Jari; Lorenz, Patrick; van Dijl, Jan Maarten

    2016-03-29

    Bacillus subtilis is an important cell factory for the biotechnological industry due to its ability to secrete commercially relevant proteins in large amounts directly into the growth medium. However, hyper-secretion of proteins, such as α-amylases, leads to induction of the secretion stress-responsive CssR-CssS regulatory system, resulting in up-regulation of the HtrA and HtrB proteases. These proteases degrade misfolded proteins secreted via the Sec pathway, resulting in a loss of product. The aim of this study was to investigate the secretion stress response in B. subtilis 168 cells overproducing the industrially relevant α-amylase AmyM from Geobacillus stearothermophilus, which was expressed from the strong promoter P(amyQ)-M. Here we show that activity of the htrB promoter as induced by overproduction of AmyM was "noisy", which is indicative for heterogeneous activation of the secretion stress pathway. Plasmids were constructed to allow real-time analysis of P(amyQ)-M promoter activity and AmyM production by, respectively, transcriptional and out-of-frame translationally coupled fusions with gfpmut3. Our results show the emergence of distinct sub-populations of high- and low-level AmyM-producing cells, reflecting heterogeneity in the activity of P(amyQ)-M. This most likely explains the heterogeneous secretion stress response. Importantly, more homogenous cell populations with regard to P(amyQ)-M activity were observed for the B. subtilis mutant strain 168degUhy32, and the wild-type strain 168 under optimized growth conditions. Expression heterogeneity of secretory proteins in B. subtilis can be suppressed by degU mutation and optimized growth conditions. Further, the out-of-frame translational fusion of a gene for a secreted target protein and gfp represents a versatile tool for real-time monitoring of protein production and opens novel avenues for Bacillus production strain improvement.

  3. Homogenization of the stochastic Navier–Stokes equation with a stochastic slip boundary condition

    KAUST Repository

    Bessaih, Hakima

    2015-11-02

    The two-dimensional Navier–Stokes equation in a perforated domain with a dynamical slip boundary condition is considered. We assume that the dynamic is driven by a stochastic perturbation on the interior of the domain and another stochastic perturbation on the boundaries of the holes. We consider a scaling (ᵋ for the viscosity and 1 for the density) that will lead to a time-dependent limit problem. However, the noncritical scaling (ᵋ, β > 1) is considered in front of the nonlinear term. The homogenized system in the limit is obtained as a Darcy’s law with memory with two permeabilities and an extra term that is due to the stochastic perturbation on the boundary of the holes. The nonhomogeneity on the boundary contains a stochastic part that yields in the limit an additional term in the Darcy’s law. We use the two-scale convergence method after extending the solution with 0 inside the holes to pass to the limit. By Itô stochastic calculus, we get uniform estimates on the solution in appropriate spaces. Due to the stochastic integral, the pressure that appears in the variational formulation does not have enough regularity in time. This fact made us rely only on the variational formulation for the passage to the limit on the solution. We obtain a variational formulation for the limit that is solution of a Stokes system with two pressures. This two-scale limit gives rise to three cell problems, two of them give the permeabilities while the third one gives an extra term in the Darcy’s law due to the stochastic perturbation on the boundary of the holes.

  4. Research Article: Effects of long-term simulated Martian conditions on a freeze-dried and homogenized bacterial permafrost community

    DEFF Research Database (Denmark)

    Hansen, Aviaja Anna; Jensen, Lars Liengård; Kristoffersen, Tommy

    2009-01-01

    Indigenous bacteria and biomolecules (DNA and proteins) in a freeze-dried and homogenized Arctic permafrost were exposed to simulated martian conditions that correspond to about 80 days on the surface of Mars with respect to the accumulated UV dose. The simulation conditions included UV radiation......, freeze-thaw cycles, the atmospheric gas composition, and pressure. The homogenized permafrost cores were subjected to repeated cycles of UV radiation for 3 h followed by 27 h without irradiation. The effects of the simulation conditions on the concentrations of biomolecules; numbers of viable, dead......, and cultured bacteria; as well as the community structure were determined. Simulated martian conditions resulted in a significant reduction of the concentrations of DNA and amino acids in the uppermost 1.5 mm of the soil core. The total number of bacterial cells was reduced in the upper 9 mm of the soil core...

  5. Outcome of homogeneous and heterogeneous reactions in Darcy-Forchheimer flow with nonlinear thermal radiation and convective condition

    Science.gov (United States)

    Hayat, T.; Shah, Faisal; Alsaedi, A.; Hussain, Zakir

    The present analysis aims to report the consequences of nonlinear radiation, convective condition and heterogeneous-homogeneous reactions in Darcy-Forchheimer flow over a non-linear stretching sheet with variable thickness. Non-uniform magnetic field and nonuniform heat generation/absorption are accounted. The governing boundary layer partial differential equations are converted into a system of nonlinear ordinary differential equations. The computations are organized and the effects of physical variables such as thickness parameter, power index, Hartman number, inertia and porous parameters, radiation parameter, Biot number, Prandtl number, ratio parameter, heat generation parameter and homogeneous-heterogeneous reaction parameter are investigated. The variations of skin friction coefficient and Nusselt number for different interesting variables are plotted and discussed. It is noticed that Biot number and heat generation variable lead to enhance the temperature distribution. The solutal boundary layer thickness decreases for larger homogeneous variable while reverse trend is seen for heterogeneous reaction.

  6. Production of starch nanoparticles using normal maize starch via heat-moisture treatment under mildly acidic conditions and homogenization.

    Science.gov (United States)

    Park, Eun Young; Kim, Min-Jung; Cho, MyoungLae; Lee, Ju Hun; Kim, Jong-Yea

    2016-10-20

    Normal maize starch was subjected to heat-moisture treatment (HMT) under mildly acidic conditions (0.000, 0.050, or 0.075M H2SO4) for various treatment times (3, 5, or 8h) followed by homogenization up to 60min to prepare nanoparticles. The combination of HMT (0.075M, for 8h) and homogenization (60min) produced nanoparticles with diameters of less than 50nm at a yield higher than 80%. X-ray diffractometry and size-exclusion chromatography revealed that HMT under mildly acidic conditions selectively hydrolyzed the starch chains (especially amylose and/or long chains of amylopectin) in the amorphous region of the granules without significant damage to the crystalline structure, however, modification of the molecular structure in the amorphous region increased fragility of the granules during homogenization. Homogenization for 60min caused obvious damage in the long-range crystalline structure of the HMT starch (0.15N, for 8h), while the short-range chain associations (FT-IR) remained intact. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Outcome of homogeneous and heterogeneous reactions in Darcy-Forchheimer flow with nonlinear thermal radiation and convective condition

    Directory of Open Access Journals (Sweden)

    T. Hayat

    Full Text Available The present analysis aims to report the consequences of nonlinear radiation, convective condition and heterogeneous-homogeneous reactions in Darcy-Forchheimer flow over a non-linear stretching sheet with variable thickness. Non-uniform magnetic field and nonuniform heat generation/absorption are accounted. The governing boundary layer partial differential equations are converted into a system of nonlinear ordinary differential equations. The computations are organized and the effects of physical variables such as thickness parameter, power index, Hartman number, inertia and porous parameters, radiation parameter, Biot number, Prandtl number, ratio parameter, heat generation parameter and homogeneous-heterogeneous reaction parameter are investigated. The variations of skin friction coefficient and Nusselt number for different interesting variables are plotted and discussed. It is noticed that Biot number and heat generation variable lead to enhance the temperature distribution. The solutal boundary layer thickness decreases for larger homogeneous variable while reverse trend is seen for heterogeneous reaction. Keywords: Variable sheet thickness, Darcy-Forchheimer flow, Homogeneous-heterogeneous reactions, Power-law surface velocity, Convective condition, Heat generation/absorption, Nonlinear radiation

  8. Folds and Etudes

    Science.gov (United States)

    Bean, Robert

    2007-01-01

    In this article, the author talks about "Folds" and "Etudes" which are images derived from anonymous typing exercises that he found in a used copy of "Touch Typing Made Simple". "Etudes" refers to the musical tradition of studies for a solo instrument, which is a typewriter. Typing exercises are repetitive attempts to type words and phrases…

  9. Multiple-pass high-pressure homogenization of milk for the development of pasteurization-like processing conditions.

    Science.gov (United States)

    Ruiz-Espinosa, H; Amador-Espejo, G G; Barcenas-Pozos, M E; Angulo-Guerrero, J O; Garcia, H S; Welti-Chanes, J

    2013-02-01

    Multiple-pass ultrahigh pressure homogenization (UHPH) was used for reducing microbial population of both indigenous spoilage microflora in whole raw milk and a baroresistant pathogen (Staphylococcus aureus) inoculated in whole sterile milk to define pasteurization-like processing conditions. Response surface methodology was followed and multiple response optimization of UHPH operating pressure (OP) (100, 175, 250 MPa) and number of passes (N) (1-5) was conducted through overlaid contour plot analysis. Increasing OP and N had a significant effect (P pasteurization. Multiple-pass UHPH optimized conditions might help in producing safe milk without the detrimental effects associated with thermal pasteurization. © 2012 The Society for Applied Microbiology.

  10. Instrumental performance of an etude after three methods of practice.

    Science.gov (United States)

    Vanden Ark, S

    1997-12-01

    For 80 fifth-grade students three practice conditions (mental, mental with physical simulation, and physical with singing) produced significant mean differences in instrumental performance of an etude. No significant differences were found for traditional, physical practice.

  11. Deviation from equilibrium conditions in molecular dynamic simulations of homogeneous nucleation.

    Science.gov (United States)

    Halonen, Roope; Zapadinsky, Evgeni; Vehkamäki, Hanna

    2018-04-28

    We present a comparison between Monte Carlo (MC) results for homogeneous vapour-liquid nucleation of Lennard-Jones clusters and previously published values from molecular dynamics (MD) simulations. Both the MC and MD methods sample real cluster configuration distributions. In the MD simulations, the extent of the temperature fluctuation is usually controlled with an artificial thermostat rather than with more realistic carrier gas. In this study, not only a primarily velocity scaling thermostat is considered, but also Nosé-Hoover, Berendsen, and stochastic Langevin thermostat methods are covered. The nucleation rates based on a kinetic scheme and the canonical MC calculation serve as a point of reference since they by definition describe an equilibrated system. The studied temperature range is from T = 0.3 to 0.65 ϵ/k. The kinetic scheme reproduces well the isothermal nucleation rates obtained by Wedekind et al. [J. Chem. Phys. 127, 064501 (2007)] using MD simulations with carrier gas. The nucleation rates obtained by artificially thermostatted MD simulations are consistently lower than the reference nucleation rates based on MC calculations. The discrepancy increases up to several orders of magnitude when the density of the nucleating vapour decreases. At low temperatures, the difference to the MC-based reference nucleation rates in some cases exceeds the maximal nonisothermal effect predicted by classical theory of Feder et al. [Adv. Phys. 15, 111 (1966)].

  12. Homogenization of the evolution Stokes equation in a perforated domain with a stochastic Fourier boundary condition

    KAUST Repository

    Bessaih, Hakima; Efendiev, Yalchin; Maris, Florin

    2015-01-01

    The evolution Stokes equation in a domain containing periodically distributed obstacles subject to Fourier boundary condition on the boundaries is considered. We assume that the dynamic is driven by a stochastic perturbation on the interior

  13. Homogenization of a thermal problem with the fourier conditions in the thin plates of a heat exchanger

    International Nuclear Information System (INIS)

    Rahmattulla, A.A.; Taghite, M.B.

    1996-01-01

    In this paper was studied a thermal problem with the fourier boundary conditions on the edges of the holes in a periodically perforated plate of a heat exchanger. This problem contains several reduced parameters which can be very small (the period ε of the distribution of the holes, the reduced thickness e of the plate and the three Biot numbers relative to the different parts of the boundary). The homogenization technique was used to estimate the field of temperatures attainable in the upper plate, depending on the relative order of magnitude of the smell parameters. (authors). 9 refs

  14. Conditional dissipation of scalars in homogeneous turbulence: Closure for MMC modelling

    Science.gov (United States)

    Wandel, Andrew P.

    2013-08-01

    While the mean and unconditional variance are to be predicted well by any reasonable turbulent combustion model, these are generally not sufficient for the accurate modelling of complex phenomena such as extinction/reignition. An additional criterion has been recently introduced: accurate modelling of the dissipation timescales associated with fluctuations of scalars about their conditional mean (conditional dissipation timescales). Analysis of Direct Numerical Simulation (DNS) results for a passive scalar shows that the conditional dissipation timescale is of the order of the integral timescale and smaller than the unconditional dissipation timescale. A model is proposed: the conditional dissipation timescale is proportional to the integral timescale. This model is used in Multiple Mapping Conditioning (MMC) modelling for a passive scalar case and a reactive scalar case, comparing to DNS results for both. The results show that this model improves the accuracy of MMC predictions so as to match the DNS results more closely using a relatively-coarse spatial resolution compared to other turbulent combustion models.

  15. Effects of Long-Term Simulated Martian Conditions on a Freeze-Dried and Homogenized Bacterial Permafrost Community

    Science.gov (United States)

    Hansen, Aviaja A.; Jenson, Lars L.; Kristoffersen, Tommy; Mikkelsen, Karina; Merrison, Jonathan; Finster, Kai W.; Lomstein, Bente Aa.

    2009-03-01

    Indigenous bacteria and biomolecules (DNA and proteins) in a freeze-dried and homogenized Arctic permafrost were exposed to simulated martian conditions that correspond to about 80 days on the surface of Mars with respect to the accumulated UV dose. The simulation conditions included UV radiation, freeze-thaw cycles, the atmospheric gas composition, and pressure. The homogenized permafrost cores were subjected to repeated cycles of UV radiation for 3 h followed by 27 h without irradiation. The effects of the simulation conditions on the concentrations of biomolecules; numbers of viable, dead, and cultured bacteria; as well as the community structure were determined. Simulated martian conditions resulted in a significant reduction of the concentrations of DNA and amino acids in the uppermost 1.5 mm of the soil core. The total number of bacterial cells was reduced in the upper 9 mm of the soil core, while the number of viable cells was reduced in the upper 15 mm. The number of cultured aerobic bacteria was reduced in the upper 6 mm of the soil core, whereas the community structure of cultured anaerobic bacteria was relatively unaffected by the exposure conditions. As explanations for the observed changes, we propose three causes that might have been working on the biological material either individually or synergistically: (i) UV radiation, (ii) UV-generated reactive oxygen species, and (iii) freeze-thaw cycles. Currently, the production and action of reactive gases is only hypothetical and will be a central subject in future investigations. Overall, we conclude that in a stable environment (no wind-/pressure-induced mixing) biological material is efficiently shielded by a 2 cm thick layer of dust, while it is relatively rapidly destroyed in the surface layer, and that biomolecules like proteins and polynucleotides are more resistant to destruction than living biota.

  16. Criticality studies; Etudes de criticite

    Energy Technology Data Exchange (ETDEWEB)

    Breton, D; Lecorche, P; Clouet d' Orval, Ch [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    Criticality studies made at the Commissariat a l'Energie atomique deal on the one hand with experiments on plutonium and uranium solutions, on the other hand with theoretical work on the development and use of computation, methods for the resolution of problems concerning the nuclear safety of chemical and metallurgical plants. I - Since 1958 the experimental studies have dealt with homogeneous media constituted by a fissile salt dissolved in light water. Developed using the reactor Proserpine, the experiments have been carried on at Saclay on the Alecto assemblies where solutions of plutonium or of 90 p.100 - enriched uranium can be made critical. The results already obtained relate to critical masses of cylindrical tanks of diameters from 20 to 50 cm. reflected in several ways (water, concrete, etc. . ) at concentrations up to 100 g/liter. Physical measurements (spectra, reactor noises) and interaction measurements complete the results. Other experiments relating to plutonium solutions were begun in 1963, at the Valduc Center. They deal with the study of critical masses of annular vessels of external diameter 50 cm and internal diameter varying from 10 to 30 cm. These vessels can be water reflected internally, externally, or both. Two of these vessels have been studied in interaction for various geometries. Slabs of various thicknesses were also studied. II - The studies thus undertaken allowed the development of methods of computation which have been tested on several experiments. Particular use has been made of the possibilities of calculations based on transport theory and on Monte Carlo methods. All these theoretical studies are applied to the design and control of industrial plants from the point of view of safety. (authors) [French] Les etudes de criticite effectuees au CEA comportent d'une part des experiences sur des solutions de plutonium et d'uranium enrichi, d'autre part des travaux theoriques portant sur la mise au point et l'exploitation de methodes

  17. Homogeneous nucleation rates of nitric acid dihydrate (NAD at simulated stratospheric conditions – Part II: Modelling

    Directory of Open Access Journals (Sweden)

    O. Möhler

    2006-01-01

    Full Text Available Activation energies ΔGact for the nucleation of nitric acid dihydrate (NAD in supercooled binary HNO3/H2O solution droplets were calculated from volume-based nucleation rate measurements using the AIDA (Aerosol, Interactions, and Dynamics in the Atmosphere aerosol chamber of Forschungszentrum Karlsruhe. The experimental conditions covered temperatures T between 192 and 197 K, NAD saturation ratios SNAD between 7 and 10, and nitric acid molar fractions of the nucleating sub-micron sized droplets between 0.26 and 0.28. Based on classical nucleation theory, a new parameterisation for ΔGact=A×(T ln SNAD−2+B is fitted to the experimental data with A=2.5×106 kcal K2 mol−1 and B=11.2−0.1(T−192 kcal mol−1. A and B were chosen to also achieve good agreement with literature data of ΔGact. The parameter A implies, for the temperature and composition range of our analysis, a mean interface tension σsl=51 cal mol−1 cm−2 between the growing NAD germ and the supercooled solution. A slight temperature dependence of the diffusion activation energy is represented by the parameter B. Investigations with a detailed microphysical process model showed that literature formulations of volume-based (Salcedo et al., 2001 and surface-based (Tabazadeh et al., 2002 nucleation rates significantly overestimate NAD formation rates when applied to the conditions of our experiments.

  18. Nonlinear Kirchhoff-Carrier wave equation in a unit membrane with mixed homogeneous boundary conditions

    Directory of Open Access Journals (Sweden)

    Nguyen Thanh Long

    2005-12-01

    Full Text Available In this paper we consider the nonlinear wave equation problem $$displaylines{ u_{tt}-Big(|u|_0^2,|u_{r}|_0^2ig(u_{rr}+frac{1}{r}u_{r} =f(r,t,u,u_{r},quad 0less than r less than 1,; 0 less than t less than T, ig|lim_{ro 0^+}sqrt{r}u_{r}(r,tig| less than infty, u_{r}(1,t+hu(1,t=0, u(r,0=widetilde{u}_0(r, u_{t}(r,0=widetilde{u}_1(r. }$$ To this problem, we associate a linear recursive scheme for which the existence of a local and unique weak solution is proved, in weighted Sobolev using standard compactness arguments. In the latter part, we give sufficient conditions for quadratic convergence to the solution of the original problem, for an autonomous right-hand side independent on $u_{r}$ and a coefficient function $B$ of the form $B=B(|u|_0^2=b_0+|u|_0^2$ with $b_0$ greater than 0.

  19. A study of the aptitude of soils under natural conditions to retain radiostrontium; Etude de la vocation des sols en place a la retention du radiostrontium

    Energy Technology Data Exchange (ETDEWEB)

    Bovard, P; Grauby, A [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1960-07-01

    Independently of the theoretical study of the propagation of radioactivity in the soil as a result of submersions or of radioactive rain, the authors have studied directly and practically how this radioactivity can vary in the actual soil. To this end a simple, rapid method has been perfected; it makes it possible to maintain for each soil sample the natural parameters (structure, humidity, etc.) without introducing boundary effects. In the laboratory, after charging the soil samples, part of the study of the propagation of radioactivity is done by autoradiography; finally, as a practical application, the study of an atomic site illustrates the methods described. (author) [French] Independamment de l'etude theorique de la propagation de la radioactivite dans le sol a la suite de submersions ou de pluies radioactives, les auteurs ont etudie directement et pratiquement comment pourrait evoluer cette radioactivite dans les sols en place. Pour cela, une methode simple et rapide a ete mise au point; elle permet de conserver pour chaque echantillon de sol, les parametres naturels (structure, humidite, etc...), sans introduire d'effets de paroi. En laboratoire, apres mise en charge des massifs preleves, une partie de l'etude de la propagation des radioelements est realisee par autoradiographie; enfin, une application pratique, l'etude d'un site atomique, illustre l'expose. (auteur)

  20. A study of the aptitude of soils under natural conditions to retain radiostrontium; Etude de la vocation des sols en place a la retention du radiostrontium

    Energy Technology Data Exchange (ETDEWEB)

    Bovard, P.; Grauby, A. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1960-07-01

    Independently of the theoretical study of the propagation of radioactivity in the soil as a result of submersions or of radioactive rain, the authors have studied directly and practically how this radioactivity can vary in the actual soil. To this end a simple, rapid method has been perfected; it makes it possible to maintain for each soil sample the natural parameters (structure, humidity, etc.) without introducing boundary effects. In the laboratory, after charging the soil samples, part of the study of the propagation of radioactivity is done by autoradiography; finally, as a practical application, the study of an atomic site illustrates the methods described. (author) [French] Independamment de l'etude theorique de la propagation de la radioactivite dans le sol a la suite de submersions ou de pluies radioactives, les auteurs ont etudie directement et pratiquement comment pourrait evoluer cette radioactivite dans les sols en place. Pour cela, une methode simple et rapide a ete mise au point; elle permet de conserver pour chaque echantillon de sol, les parametres naturels (structure, humidite, etc...), sans introduire d'effets de paroi. En laboratoire, apres mise en charge des massifs preleves, une partie de l'etude de la propagation des radioelements est realisee par autoradiographie; enfin, une application pratique, l'etude d'un site atomique, illustre l'expose. (auteur)

  1. Effect of fat content and homogenization under conventional or ultra-high-pressure conditions on interactions between proteins in rennet curds.

    Science.gov (United States)

    Zamora, A; Trujillo, A J; Armaforte, E; Waldron, D S; Kelly, A L

    2012-09-01

    The objective of this study was to investigate the influence of conventional and ultra-high-pressure homogenization on interactions between proteins within drained rennet curds. The effect of fat content of milk (0.0, 1.8, or 3.6%) and homogenization treatment on dissociation of proteins by different chemical agents was thus studied. Increasing the fat content of raw milk increased levels of unbound whey proteins and calcium-bonded caseins in curds; in contrast, hydrophobic interactions and hydrogen bonds were inhibited. Both homogenization treatments triggered the incorporation of unbound whey proteins in the curd, and of caseins through ionic bonds involving calcium salts. Conventional homogenization-pasteurization enhanced interactions between caseins through hydrogen bonds and hydrophobic interactions. In contrast, ultra-high-pressure homogenization impaired hydrogen bonding, led to the incorporation of both whey proteins and caseins through hydrophobic interactions and increased the amount of unbound caseins. Thus, both homogenization treatments provoked changes in the protein interactions within rennet curds; however, the nature of the changes depended on the homogenization conditions. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  2. Determination of protein carbonyls in plasma, cell extracts, tissue homogenates, isolated proteins: Focus on sample preparation and derivatization conditions.

    Science.gov (United States)

    Weber, Daniela; Davies, Michael J; Grune, Tilman

    2015-08-01

    Protein oxidation is involved in regulatory physiological events as well as in damage to tissues and is thought to play a key role in the pathophysiology of diseases and in the aging process. Protein-bound carbonyls represent a marker of global protein oxidation, as they are generated by multiple different reactive oxygen species in blood, tissues and cells. Sample preparation and stabilization are key steps in the accurate quantification of oxidation-related products and examination of physiological/pathological processes. This review therefore focuses on the sample preparation processes used in the most relevant methods to detect protein carbonyls after derivatization with 2,4-dinitrophenylhydrazine with an emphasis on measurement in plasma, cells, organ homogenates, isolated proteins and organelles. Sample preparation, derivatization conditions and protein handling are presented for the spectrophotometric and HPLC method as well as for immunoblotting and ELISA. An extensive overview covering these methods in previously published articles is given for researchers who plan to measure protein carbonyls in different samples. © 2015 Published by Elsevier Ltd.

  3. More homogeneous wind conditions under strong climate change decrease the potential for inter-state balancing of electricity in Europe

    Science.gov (United States)

    Wohland, Jan; Reyers, Mark; Weber, Juliane; Witthaut, Dirk

    2017-11-01

    Limiting anthropogenic climate change requires the fast decarbonization of the electricity system. Renewable electricity generation is determined by the weather and is hence subject to climate change. We simulate the operation of a coarse-scale fully renewable European electricity system based on downscaled high-resolution climate data from EURO-CORDEX. Following a high-emission pathway (RCP8.5), we find a robust but modest increase (up to 7 %) of backup energy in Europe through the end of the 21st century. The absolute increase in the backup energy is almost independent of potential grid expansion, leading to the paradoxical effect that relative impacts of climate change increase in a highly interconnected European system. The increase is rooted in more homogeneous wind conditions over Europe resulting in intensified simultaneous generation shortfalls. Individual country contributions to European generation shortfall increase by up to 9 TWh yr-1, reflecting an increase of up to 4 %. Our results are strengthened by comparison with a large CMIP5 ensemble using an approach based on circulation weather types.

  4. Efficacy of various pasteurization time-temperature conditions in combination with homogenization on inactivation of Mycobacterium avium subsp. paratuberculosis in milk.

    Science.gov (United States)

    Grant, Irene R; Williams, Alan G; Rowe, Michael T; Muir, D Donald

    2005-06-01

    The effect of various pasteurization time-temperature conditions with and without homogenization on the viability of Mycobacterium avium subsp. paratuberculosis was investigated using a pilot-scale commercial high-temperature, short-time (HTST) pasteurizer and raw milk spiked with 10(1) to 10(5) M. avium subsp. paratuberculosis cells/ml. Viable M. avium subsp. paratuberculosis was cultured from 27 (3.3%) of 816 pasteurized milk samples overall, 5 on Herrold's egg yolk medium and 22 by BACTEC culture. Therefore, in 96.7% of samples, M. avium subsp. paratuberculosis had been completely inactivated by HTST pasteurization, alone or in combination with homogenization. Heat treatments incorporating homogenization at 2,500 lb/in2, applied upstream (as a separate process) or in hold (at the start of a holding section), resulted in significantly fewer culture-positive samples than pasteurization treatments without homogenization (P HTST pasteurization with or without homogenization was estimated to be 4.0 to 5.2 log10. The impact of homogenization on clump size distribution in M. avium subsp. paratuberculosis broth suspensions was subsequently assessed using a Mastersizer X spectrometer. These experiments demonstrated that large clumps of M. avium subsp. paratuberculosis cells were reduced to single-cell or "miniclump" status by homogenization at 2,500 lb/in2. Consequently, when HTST pasteurization was being applied to homogenized milk, the M. avium subsp. paratuberculosis cells would have been present as predominantly declumped cells, which may possibly explain the greater inactivation achieved by the combination of pasteurization and homogenization.

  5. Efficacy of Various Pasteurization Time-Temperature Conditions in Combination with Homogenization on Inactivation of Mycobacterium avium subsp. paratuberculosis in Milk

    Science.gov (United States)

    Grant, Irene R.; Williams, Alan G.; Rowe, Michael T.; Muir, D. Donald

    2005-01-01

    The effect of various pasteurization time-temperature conditions with and without homogenization on the viability of Mycobacterium avium subsp. paratuberculosis was investigated using a pilot-scale commercial high-temperature, short-time (HTST) pasteurizer and raw milk spiked with 101 to 105 M. avium subsp. paratuberculosis cells/ml. Viable M. avium subsp. paratuberculosis was cultured from 27 (3.3%) of 816 pasteurized milk samples overall, 5 on Herrold's egg yolk medium and 22 by BACTEC culture. Therefore, in 96.7% of samples, M. avium subsp. paratuberculosis had been completely inactivated by HTST pasteurization, alone or in combination with homogenization. Heat treatments incorporating homogenization at 2,500 lb/in2, applied upstream (as a separate process) or in hold (at the start of a holding section), resulted in significantly fewer culture-positive samples than pasteurization treatments without homogenization (P pasteurization with or without homogenization was estimated to be 4.0 to 5.2 log10. The impact of homogenization on clump size distribution in M. avium subsp. paratuberculosis broth suspensions was subsequently assessed using a Mastersizer X spectrometer. These experiments demonstrated that large clumps of M. avium subsp. paratuberculosis cells were reduced to single-cell or “miniclump” status by homogenization at 2,500 lb/in2. Consequently, when HTST pasteurization was being applied to homogenized milk, the M. avium subsp. paratuberculosis cells would have been present as predominantly declumped cells, which may possibly explain the greater inactivation achieved by the combination of pasteurization and homogenization. PMID:15932977

  6. Time-dependent rheoforging of A6061 aluminum alloy on a mechanical servo press and the effects of forming conditions on homogeneity of rheoforged samples

    Directory of Open Access Journals (Sweden)

    Meng Yi

    2015-01-01

    Full Text Available The solid and liquid phases in semisolid metal slurry exhibited different forming behaviours during deformation result in products with inhomogeneous quality. A6061 aluminum alloy was forged in the semisolid state on a mechanical servo press with the capability of multistage compression. To improve the homogeneity of rheoforged samples a time-dependent rheoforging strategy was designed. The distributions of the microstructure and mechanical properties the samples manufactured under various experimental conditions were investigated. The A6061 samples forged in the temperature range from 625 to 628 ∘C with a short holding time of 4 s and the upper die preheated to 300 ∘C exhibited a homogeneous microstructure and mechanical properties. The homogeneity of rheoforged samples resulted from the controllable free motion capability of the mechanical servo press and the adjustable fluidity and viscosity of the semisolid slurry.

  7. Study of the paraffinic crudes in deep offshore conditions; Etude du comportement des bruts paraffiniques dans les conditions de l'offshore profond

    Energy Technology Data Exchange (ETDEWEB)

    Delmas, K.

    2001-09-01

    The increase production in deep offshore conditions leads to extracting the crudes in harsher conditions. Pressures are higher (up to 400) and thus the amounts of dissolved gases are more important. The Wax Appearance Temperature (WAT) and the amount of solid deposit with the temperature are well calculated by the thermodynamic model Cryspar, developed at IFP for stock tank crude oils. This work shows that the hypotheses made for the Cryspar model, are not valid for fluids with dissolved gases. The model has been improved using following items: - Experimental data of volume variation at the melting point, in sapphire cell, allow to take into account the Poynting term, neglected before. This work allows to give back the right direction of variation for the WAT as a function of pressure. We proved by calorimetric measurements on n-paraffin synthetic mixtures, the existence of an excess melting enthalpy, not taken into account by the model. We calculate it using several models taken from the literature. Unfortunately, this work slightly decreases the difference between the experimental amount of wax and the calculated amount. The third point, concerns the binary interaction coefficients used to set out the non-ideality of the solid phase. Some coefficients have been calculated allowing a better restitution of the phase composition at equilibrium. In addition, to improving the model, some high pressure WAT data (up to 300 bar) with dissolved gases have been collected. They provide an independent set on which the model predictions have been validated. (author)

  8. Comparative analysis of storage conditions and homogenization methods for tick and flea species for identification by MALDI-TOF MS.

    Science.gov (United States)

    Nebbak, A; El Hamzaoui, B; Berenger, J-M; Bitam, I; Raoult, D; Almeras, L; Parola, P

    2017-12-01

    Ticks and fleas are vectors for numerous human and animal pathogens. Controlling them, which is important in combating such diseases, requires accurate identification, to distinguish between vector and non-vector species. Recently, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was applied to the rapid identification of arthropods. The growth of this promising tool, however, requires guidelines to be established. To this end, standardization protocols were applied to species of Rhipicephalus sanguineus (Ixodida: Ixodidae) Latreille and Ctenocephalides felis felis (Siphonaptera: Pulicidae) Bouché, including the automation of sample homogenization using two homogenizer devices, and varied sample preservation modes for a period of 1-6 months. The MS spectra were then compared with those obtained from manual pestle grinding, the standard homogenization method. Both automated methods generated intense, reproducible MS spectra from fresh specimens. Frozen storage methods appeared to represent the best preservation mode, for up to 6 months, while storage in ethanol is also possible, with some caveats for tick specimens. Carnoy's buffer, however, was shown to be less compatible with MS analysis for the purpose of identifying ticks or fleas. These standard protocols for MALDI-TOF MS arthropod identification should be complemented by additional MS spectrum quality controls, to generalize their use in monitoring arthropods of medical interest. © 2017 The Royal Entomological Society.

  9. Reflector homogenization

    International Nuclear Information System (INIS)

    Sanchez, R.; Ragusa, J.; Santandrea, S.

    2004-01-01

    The problem of the determination of a homogeneous reflector that preserves a set of prescribed albedo is considered. Duality is used for a direct estimation of the derivatives needed in the iterative calculation of the optimal homogeneous cross sections. The calculation is based on the preservation of collapsed multigroup albedo obtained from detailed reference calculations and depends on the low-order operator used for core calculations. In this work we analyze diffusion and transport as low-order operators and argue that the P 0 transfers are the best choice for the unknown cross sections to be adjusted. Numerical results illustrate the new approach for SP N core calculations. (Author)

  10. Classical entropy generation analysis in cooled homogenous and functionally graded material slabs with variation of internal heat generation with temperature, and convective–radiative boundary conditions

    International Nuclear Information System (INIS)

    Torabi, Mohsen; Zhang, Kaili

    2014-01-01

    This article investigates the classical entropy generation in cooled slabs. Two types of materials are assumed for the slab: homogeneous material and FGM (functionally graded material). For the homogeneous material, the thermal conductivity is assumed to be a linear function of temperature, while for the FGM slab the thermal conductivity is modeled to vary in accordance with the rule of mixtures. The boundary conditions are assumed to be convective and radiative concurrently, and the internal heat generation of the slab is a linear function of temperature. Using the DTM (differential transformation method) and resultant temperature fields from the DTM, the local and total entropy generation rates within slabs are derived. The effects of physically applicable parameters such as the thermal conductivity parameter for the homogenous slab, β, the thermal conductivity parameter for the FGM slab, γ, gradient index, j, internal heat generation parameter, Q, Biot number at the right side, Nc 2 , conduction–radiation parameter, Nr 2 , dimensionless convection sink temperature, δ, and dimensionless radiation sink temperature, η, on the local and total entropy generation rates are illustrated and explained. The results demonstrate that considering temperature- or coordinate-dependent thermal conductivity and radiation heat transfer at both sides of the slab have great effects on the entropy generation. - Highlights: • The paper investigates entropy generation in a slab due to heat generation and convective–radiative boundary conditions. • Both homogeneous material and FGM (functionally graded material) were considered. • The calculations are carried out using the differential transformation method which is a well-tested analytical technique

  11. Influence of boundary conditions on the response of multilayered plates with cohesive interfaces and delaminations using a homogenized approach

    Directory of Open Access Journals (Sweden)

    R. Massabò

    2014-07-01

    Full Text Available Stress and displacement fields in multilayered composites with interfacial imperfections, such as imperfect bonding of the layers or delaminations, or where the plies are separated by thin interlayers allowing relative motion, have large variations in the thickness, with characteristic zigzag patterns and jumps at the layer interfaces. These effects are well captured by a model recently formulated by the author for multilayered plates with imperfect interfaces and affine interfacial traction laws (Massabò & Campi, Meccanica, 2014, in press; Compos Struct, 2014, 116, 311-324. The model defines a homogenized displacement field, which satisfies interfacial continuity, and uses a variational technique to derive equilibrium equations depending on only six generalized displacement functions, for any arbitrary numbers of layers and interfaces. The model accurately predicts stresses and displacements in simply supported, highly anisotropic, thick plates with continuous, sliding interfaces. In this paper the model is applied to wide plates with clamped edges and some inconsistencies, which have been noted in the literature for models based on similar approaches and have limited their utilization, are explained. A generalized transverse shear force is introduced as the gross stress resultant which is directly related to the bending moment in the equilibrium equations of multilayered structures with imperfect interfaces and substitutes for the shear force of single-layer theory. An application to a delaminated wide plate highlights the potential and limitations of the proposed model for the solution of fracture mechanics problems.

  12. Reflector homogenization

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, R.; Ragusa, J.; Santandrea, S. [Commissariat a l' Energie Atomique, Direction de l' Energie Nucleaire, Service d' Etudes de Reacteurs et de Modelisation Avancee, CEA de Saclay, DM2S/SERMA 91 191 Gif-sur-Yvette cedex (France)]. e-mail: richard.sanchez@cea.fr

    2004-07-01

    The problem of the determination of a homogeneous reflector that preserves a set of prescribed albedo is considered. Duality is used for a direct estimation of the derivatives needed in the iterative calculation of the optimal homogeneous cross sections. The calculation is based on the preservation of collapsed multigroup albedo obtained from detailed reference calculations and depends on the low-order operator used for core calculations. In this work we analyze diffusion and transport as low-order operators and argue that the P{sub 0} transfers are the best choice for the unknown cross sections to be adjusted. Numerical results illustrate the new approach for SP{sub N} core calculations. (Author)

  13. Photocatalysis of the homogeneous water-gas shift reaction under ambient conditions by cationic iridium (III) complexes

    Energy Technology Data Exchange (ETDEWEB)

    Ziessel, R [Ecole Europeenne des Hautes Etudes des Industries Chimiques, 67 - Strasbourg (France)

    1991-07-01

    We describe here our results and mechanistic analysis of the first highly efficient light-assisted WGSR, which takes place under extremely mild conditions (room temperature, ambient pressure, neutral pH, visible light) and is catalyzed by novel Ir{sup III} pentamethylcyclopentadienyl complexes containing novel 4,4'-substituted bipyridine ligands. (orig./EF).

  14. Effect of Boundary Conditions on the Axial Compression Buckling of Homogeneous Orthotropic Composite Cylinders in the Long Column Range

    Science.gov (United States)

    Mikulas, Martin M., Jr.; Nemeth, Michael P.; Oremont, Leonard; Jegley, Dawn C.

    2011-01-01

    Buckling loads for long isotropic and laminated cylinders are calculated based on Euler, Fluegge and Donnell's equations. Results from these methods are presented using simple parameters useful for fundamental design work. Buckling loads for two types of simply supported boundary conditions are calculated using finite element methods for comparison to select cases of the closed form solution. Results indicate that relying on Donnell theory can result in an over-prediction of buckling loads by as much as 40% in isotropic materials.

  15. On the Importance of Processing Conditions for the Nutritional Characteristics of Homogenized Composite Meals Intended for Infants.

    Science.gov (United States)

    Östman, Elin; Forslund, Anna; Tareke, Eden; Björck, Inger

    2016-06-03

    The nutritional quality of infant food is an important consideration in the effort to prevent a further increase in the rate of childhood obesity. We hypothesized that the canning of composite infant meals would lead to elevated contents of carboxymethyl-lysine (CML) and favor high glycemic and insulinemic responses compared with milder heat treatment conditions. We have compared composite infant pasta Bolognese meals that were either conventionally canned (CANPBol), or prepared by microwave cooking (MWPBol). A meal where the pasta and Bolognese sauce were separate during microwave cooking (MWP_CANBol) was also included. The infant meals were tested at breakfast in healthy adults using white wheat bread (WWB) as reference. A standardized lunch meal was served at 240 min and blood was collected from fasting to 360 min after breakfast. The 2-h glucose response (iAUC) was lower following the test meals than with WWB. The insulin response was lower after the MWP_CANBol (-47%, p = 0.0000) but markedly higher after CANPBol (+40%, p = 0.0019), compared with WWB. A combined measure of the glucose and insulin responses (ISIcomposite) revealed that MWP_CANBol resulted in 94% better insulin sensitivity than CANPBol. Additionally, the separate processing of the meal components in MWP_CANBol resulted in 39% lower CML levels than the CANPBol. It was therefore concluded that intake of commercially canned composite infant meals leads to reduced postprandial insulin sensitivity and increased exposure to oxidative stress promoting agents.

  16. On the Importance of Processing Conditions for the Nutritional Characteristics of Homogenized Composite Meals Intended for Infants

    Directory of Open Access Journals (Sweden)

    Elin Östman

    2016-06-01

    Full Text Available The nutritional quality of infant food is an important consideration in the effort to prevent a further increase in the rate of childhood obesity. We hypothesized that the canning of composite infant meals would lead to elevated contents of carboxymethyl-lysine (CML and favor high glycemic and insulinemic responses compared with milder heat treatment conditions. We have compared composite infant pasta Bolognese meals that were either conventionally canned (CANPBol, or prepared by microwave cooking (MWPBol. A meal where the pasta and Bolognese sauce were separate during microwave cooking (MWP_CANBol was also included. The infant meals were tested at breakfast in healthy adults using white wheat bread (WWB as reference. A standardized lunch meal was served at 240 min and blood was collected from fasting to 360 min after breakfast. The 2-h glucose response (iAUC was lower following the test meals than with WWB. The insulin response was lower after the MWP_CANBol (−47%, p = 0.0000 but markedly higher after CANPBol (+40%, p = 0.0019, compared with WWB. A combined measure of the glucose and insulin responses (ISIcomposite revealed that MWP_CANBol resulted in 94% better insulin sensitivity than CANPBol. Additionally, the separate processing of the meal components in MWP_CANBol resulted in 39% lower CML levels than the CANPBol. It was therefore concluded that intake of commercially canned composite infant meals leads to reduced postprandial insulin sensitivity and increased exposure to oxidative stress promoting agents.

  17. Homogenous UV/periodate process in treatment of p-nitrophenol aqueous solutions under mild operating conditions.

    Science.gov (United States)

    Saien, Javad; Fallah Vahed Bazkiaei, Marzieh

    2018-07-01

    Aqueous solutions of p-nitrophenol (PNP) were treated with UV-activated potassium periodate (UV/KPI) in an efficient photo-reactor. Either periodate or UV alone had little effect; however, their combination led to a significant degradation and mineralization. The response surface methodology was employed for design of experiments and optimization. The optimum conditions for treatment of 30 mg/L of the substrate were determined as [KPI] = 386.3 mg/L, pH = 6.2 and T = 34.6°C, under which 79.5% degradation was achieved after 60 min. Use of 25 and 40 kHz ultrasound waves caused the degradation to enhance to 88.3% and 92.3%, respectively. The intermediates were identified by gas chromatography-mass spectroscopy analysis, leading to propose the reaction pathway. The presence of water conventional bicarbonate, chloride, sulfate and nitrate anions caused unfavorable effects in efficiency. Meanwhile, the kinetic study showed that PNP degradation follows a pseudo-first-order reaction and the activation energy was determined. The irradiation energy consumption required for one order of magnitude degradation was estimated as 11.18 kWh/m 3 . Accordingly, comparison with the previously reported processes showed the superiority of PNP treatment with the employed process.

  18. Benchmarking monthly homogenization algorithms

    Science.gov (United States)

    Venema, V. K. C.; Mestre, O.; Aguilar, E.; Auer, I.; Guijarro, J. A.; Domonkos, P.; Vertacnik, G.; Szentimrey, T.; Stepanek, P.; Zahradnicek, P.; Viarre, J.; Müller-Westermeier, G.; Lakatos, M.; Williams, C. N.; Menne, M.; Lindau, R.; Rasol, D.; Rustemeier, E.; Kolokythas, K.; Marinova, T.; Andresen, L.; Acquaotta, F.; Fratianni, S.; Cheval, S.; Klancar, M.; Brunetti, M.; Gruber, C.; Prohom Duran, M.; Likso, T.; Esteban, P.; Brandsma, T.

    2011-08-01

    The COST (European Cooperation in Science and Technology) Action ES0601: Advances in homogenization methods of climate series: an integrated approach (HOME) has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies and because they represent two important types of statistics (additive and multiplicative). The algorithms were validated against a realistic benchmark dataset. The benchmark contains real inhomogeneous data as well as simulated data with inserted inhomogeneities. Random break-type inhomogeneities were added to the simulated datasets modeled as a Poisson process with normally distributed breakpoint sizes. To approximate real world conditions, breaks were introduced that occur simultaneously in multiple station series within a simulated network of station data. The simulated time series also contained outliers, missing data periods and local station trends. Further, a stochastic nonlinear global (network-wide) trend was added. Participants provided 25 separate homogenized contributions as part of the blind study as well as 22 additional solutions submitted after the details of the imposed inhomogeneities were revealed. These homogenized datasets were assessed by a number of performance metrics including (i) the centered root mean square error relative to the true homogeneous value at various averaging scales, (ii) the error in linear trend estimates and (iii) traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Contingency scores by themselves are not very informative. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve precipitation data

  19. A procedure for estimating the electron temperature and the departure of the LTE condition in a time-dependent, spatially homogeneous, optically thin plasma

    Energy Technology Data Exchange (ETDEWEB)

    Bredice, F. [Centro de Investigaciones Opticas, La Plata (Argentina); Borges, F.O., E-mail: borges@if.uff.br [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Fisica. Lab. de Plasma e Espectroscopia; Di Rocco, H.O. [Instituto de Fisica Arroyo Seco (IFAS), Universidad Nacional del Centro, Tandil (Argentina); Mercado, R.S. [Grupo de Espectroscopia Optica de Emision y Laser (GEOEL), Universidad del Atlantico, Barranquilla (Colombia); Villagran-Muniz, M. [Laboratorio de Fotofisica, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico (Mexico); Palleschi, V. [Applied Laser Spectroscopy Laboratory, ICCOM-CNR, Pisa (Italy)

    2013-08-15

    We present a method to estimate the temperature of transient plasmas and their degree of departure from local thermodynamic equilibrium conditions. Our method is based on application of the Saha–Boltzmann equations on the temporal variation of the intensity of the spectral lines of the plasma, under the assumption that the plasmas at the different times when the spectra were obtained are in local thermodynamic equilibrium. The method requires no knowledge of the spectral efficiency of the spectrometer/detector, transition probabilities of the considered lines, or degeneracies of the upper and lower levels. Provided that the conditions of optically thin, homogeneous plasma in local thermodynamic equilibrium are satisfied, the accuracy of the procedure is limited only by the precision with which the line intensities and densities can be determined at two different temperatures. The procedure generates an equation describing the temporal evolution of the electron number density of transient plasmas under local thermodynamic equilibrium conditions. The method is applied to the analysis of two laser-induced breakdown spectra of cadmium at different temperatures. (author)

  20. A procedure for estimating the electron temperature and the departure of the LTE condition in a time-dependent, spatially homogeneous, optically thin plasma

    International Nuclear Information System (INIS)

    Bredice, F.; Borges, F.O.; Mercado, R.S.; Villagran-Muniz, M.; Palleschi, V.

    2013-01-01

    We present a method to estimate the temperature of transient plasmas and their degree of departure from local thermodynamic equilibrium conditions. Our method is based on application of the Saha–Boltzmann equations on the temporal variation of the intensity of the spectral lines of the plasma, under the assumption that the plasmas at the different times when the spectra were obtained are in local thermodynamic equilibrium. The method requires no knowledge of the spectral efficiency of the spectrometer/detector, transition probabilities of the considered lines, or degeneracies of the upper and lower levels. Provided that the conditions of optically thin, homogeneous plasma in local thermodynamic equilibrium are satisfied, the accuracy of the procedure is limited only by the precision with which the line intensities and densities can be determined at two different temperatures. The procedure generates an equation describing the temporal evolution of the electron number density of transient plasmas under local thermodynamic equilibrium conditions. The method is applied to the analysis of two laser-induced breakdown spectra of cadmium at different temperatures. (author)

  1. Study of formation and stability conditions of gas hydrates in drilling fluids; Etude des conditions de formation et de stabilite des hydrates de gaz dans les fluides de forage

    Energy Technology Data Exchange (ETDEWEB)

    Kharrat, M.

    2004-10-15

    Drilling fluids are complex media, in which solid particles are in suspension in a water-in-oil emulsion. The formation of gas hydrates in these fluids during off shore drilling operations has been suspected to be the cause of serious accidents. The purpose of this thesis is the study of the formation conditions as well as the stability of gas hydrates in complex fluids containing water-in-oil emulsions. The technique of high-pressure differential scanning calorimetry was used to characterise the conditions of hydrates formation and dissociation. Special attention has first been given to the validation of thermodynamic measurements in homogeneous solutions, in the pressure range 4 to 12 Mpa; the results were found to be in good agreement with literature data, as well as with modelling results. The method was then applied to water-in-oil emulsion, used as a model for real drilling fluids. It was proven that thermodynamics of hydrate stability are not significantly influenced by the state of dispersion of the water phase. On the other hand, the kinetics of formation and the amount of hydrates formed are highly increased by the dispersion. Applying the technique to real drilling fluids confirmed the results obtained in emulsions. Results interpretation allowed giving a representation of the process of hydrate formation in emulsion. Empirical modelling was developed to compute the stability limits of methane hydrate in the presence of various inhibitors, at pressures ranging from ambient to 70 MPa. Isobaric phase diagrams were constructed, that allow predicting the inhibiting efficiency of sodium chloride and calcium chloride at constant pressure, from 0,25 to 70 MPa. (author)

  2. Strontium and caesium transport in unsaturated soil from Chernobyl Pilot Site under steady flow conditions; Transfert de radioelements en zone non saturee. Etude experimentale et modelisation appliquees au Site Pilote de Tchernobyl

    Energy Technology Data Exchange (ETDEWEB)

    Szenknect, St

    2003-10-15

    This work is devoted to the quantification and the identification of the predominant processes involved in strontium and caesium transport in unsaturated soil from Chernobyl Pilot Site under steady flow conditions. The transport and fate of radionuclides in the subsurface is affected by various physical and chemical processes including advective and diffusive transport as well as chemical and biological transformations. Laboratory experiments and the use of a multiple tracer approach allow to isolate the contributions of each elementary process and to control the physico-chemical conditions in the system. To be more representative of the field conditions, we decided to perform column miscible displacement experiments. We perform batch and flow-through reactor experiments to characterize the radionuclides sorption mechanisms. Miscible displacement experiments within homogeneous columns and modeling allow to characterize the hydrodynamic properties of the soil and to describe the radionuclides behaviour under dynamic conditions at different water contents. We show that the water content of porous media affect the transport behaviour of inert and strongly sorbing radionuclides. Our results demonstrate that a parametrized transport model that was calibrated under completely saturated conditions was not able to describe the advective-dispersive transport of reactive solutes under unsaturated steady state conditions. Under our experimental conditions, there is no effect of a decrease of the mean water content on the sorption model parameters, but the transport parameters are modified. We established for the studied soil the relation between hydrodynamic dispersion and water content and the relation between pore water velocity and water content. (author)

  3. Homogenization conditions affect the oxidative stability of fish oil enriched milk emulsions: Oxidation linked to changes in protein composition at the oil-water interface

    DEFF Research Database (Denmark)

    Sørensen, Ann-Dorit Moltke; Baron, Caroline; Bruni Let, Mette

    2007-01-01

    Fish oil was incorporated into milk under different homogenization temperatures (50 and 72 °C) and pressures (5, 15, and 22.5 MPa). Subsequently, the oxidative stability of the milk and changes in the protein composition of the milk fat globule membrane (MFGM) were examined. Results showed...

  4. HOMOGENEOUS NUCLEAR POWER REACTOR

    Science.gov (United States)

    King, L.D.P.

    1959-09-01

    A homogeneous nuclear power reactor utilizing forced circulation of the liquid fuel is described. The reactor does not require fuel handling outside of the reactor vessel during any normal operation including complete shutdown to room temperature, the reactor being selfregulating under extreme operating conditions and controlled by the thermal expansion of the liquid fuel. The liquid fuel utilized is a uranium, phosphoric acid, and water solution which requires no gus exhaust system or independent gas recombining system, thereby eliminating the handling of radioiytic gas.

  5. Necessary conditions for the homogeneous formation of a volume avalanche discharge with specific applications to rare gas-halide excimer laser discharges

    International Nuclear Information System (INIS)

    Levatter, J.I.

    1979-01-01

    Self-sustained/avalanche discharges are an efficient method of rare gas-halide excimer laser excitation in small systems. However, with the exceptions of the work reported here, experiments attempting to increase the laser energy output by scaling up the discharge volume and/or pulse duration have not been successful. The major problem encountered in scaling experiments has been the formation of arc channels in the discharge volume. The presence of arcing can totally disrupt proper laser operation. This problem stems from a general lack of understanding of high pressure avalanche discharge phenomena. Therefore, clarifying the basic discharge formation process and establishing a set of criteria under which a homogeneous avalanche discharge can be obtained is of central importance in defining the scaling limits of avalanche discharge lasers. The work presented here reviews the phenomena involved in high E/n (electric field to gas number density ratio) breakdown and its relationship to the formation of spatially homogeneous discharges. This relationship was first explored by A.J. Palmer in 1974. The basic requirement of his model was that the preionization density be large enough to cause an appreciable overlap of the primary electron avalanches and hence smooth out the ensuing space-charge fields to the extent that individual streamer formation would be prevented. This is the same basic model used in the more detailed discharge formation analysis developed here except that the effects of a time varying electric field caused by a finite voltage rise time and the effects due to the various electrochemical properties of the gas mixture are property taken into consideration

  6. Contribution to the study of several chemical hazards in the Centre d'Etudes Nucleaires of Fontenay-aux-Roses; Contribution a l'etude de quelques nuisances chimiques au centre d'etudes nucleaires de Fontenay-aux-Roses

    Energy Technology Data Exchange (ETDEWEB)

    Megemont, C; Grau, C [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1968-10-01

    From the checking of 2750 index cards of hazards, the study relates the distribution of the chemical hazards in the Centre d'Etudes Nucleaires of Fontenay-aux-Roses. Those concerning the greatest number of agents in the Centre are classified according to the categories corresponding to the different conditions of working. Thus, the most important are put forward. Then, the authors rapidly make a review of hazards which may have some special interest because they appear more specific of the nuclear energy or because they are the most frequently noted on the index cards of hazards. The case of the tributylphosphate is studied more precisely. (authors) [French] A partir de l'examen de 2750 fiches de nuisances, l'etude porte sur la repartition des nuisances chimiques au Centre d'Etudes Nucleaires de Fontenay-aux-Roses. Celles qui concernent le plus grand nombre d'agents du Centre sont classees selon les categories correspondant aux differentes conditions de travail. Les plus importantes d'entre elles sont ainsi mises en evidence. | Les auteurs passent ensuite en revue, rapidement, les nuisances qui peuvent presenter un interet particulier soit parce qu'elles semblent plus specifiques de l'Energie Nucleaire, soit parce qu'on les rencontre le plus frequemment sur les fiches de nuisances. Le cas du tributylphosphate est envisage de facon plus detaillee. (auteurs)

  7. Numerical study of inflow conditions on a turbulent isothermal or heated plane jet; Etude numerique des conditions d'emission sur un ecoulement de type jet plan turbulent isotherme ou chauffe

    Energy Technology Data Exchange (ETDEWEB)

    Mhiri, H.; Habli, S.; El Golli, S. [Ecole Nationale d' Ingenieurs de Monastir (Tunisia); Le Palec, G.; Bournot, Ph. [Institut de Mecanique de Marseille (France)

    1999-11-01

    We intend to solve equations governing turbulent plane-vertical isotherm and non isotherm jets by taking into account inflow conditions at the exit of the nozzle. The analysis is focused on the influence of these conditions on this type of flow. Two cases are considered (uniform and parabolic velocity and temperature profiles). A finite difference scheme is developed to solve the governing equations. This numeric model allows us to show that the region of fully developed regime begins much nearer the nozzle for the turbulent case than for the laminar flow case. Indeed, the turbulence increases the mixing between the incoming gas from the nozzle and the ambient fluid, and consequently the size of the potential core zone decreases. The results are compared to other works introducing mathematical variables based on the energy conservation for the case of the mixed convection and the momentum conservation for the forced convection, which allows the validation of our results. (authors)

  8. Study of colloidal particles behaviour in the PWR primary circuit conditions; Etude du comportement des particules colloidales dans les conditions physicochimiques du circuit primaire des reacteurs a eau sous pression

    Energy Technology Data Exchange (ETDEWEB)

    Barale, M

    2006-12-15

    EDF wants to understand, model and limit primary circuit contamination of Pressurized Water Reactors by colloidal particles resulting from corrosion. The electrostatic behaviour of representative oxide particles (cobalt ferrite, nickel ferrite and magnetite) has been studied in primary circuit conditions with the influence of boric acid and lithium hydroxide. The isoelectric point (IEP) and the point of zero charge (PZC) of particles, measured between 5 C and 320 C, exhibit a minimum towards 200 C. The thermodynamic constants of the protonation equilibrium of surface sites were calculated. When boric acid is added, zeta potential and IEP decrease because of borate ions sorption. On the contrary, there is not effect of lithium ions. The modelling of these results under conditions representative of primary circuit shows that these oxides exhibit a negative surface charge, explaining their sorption and adhesion behaviour. (author)

  9. Etude aerodynamique d'un jet turbulent impactant une paroi concave

    Science.gov (United States)

    LeBlanc, Benoit

    Etant donne la demande croissante de temperatures elevees dans des chambres de combustion de systemes de propulsions en aerospatiale (turbomoteurs, moteur a reaction, etc.), l'interet dans le refroidissement par jets impactant s'est vu croitre. Le refroidissement des aubes de turbine permet une augmentation de temperature de combustion, ce qui se traduit en une augmentation de l'efficacite de combustion et donc une meilleure economie de carburant. Le transfert de chaleur dans les au bages est influence par les aspects aerodynamiques du refroidissement a jet, particulierement dans le cas d'ecoulements turbulents. Un manque de comprehension de l'aerodynamique a l'interieur de ces espaces confinees peut mener a des changements de transfert thermique qui sont inattendus, ce qui augmente le risque de fluage. Il est donc d'interet pour l'industrie aerospatiale et l'academie de poursuivre la recherche dans l'aerodynamique des jets turbulents impactant les parois courbes. Les jets impactant les surfaces courbes ont deja fait l'objet de nombreuses etudes. Par contre des conditions oscillatoires observees en laboratoire se sont averees difficiles a reproduire en numerique, puisque les structures d'ecoulements impactants des parois concaves sont fortement dependantes de la turbulence et des effets instationnaires. Une etude experimentale fut realisee a l'institut PPRIME a l'Universite de Poitiers afin d'observer le phenomene d'oscillation dans le jet. Une serie d'essais ont verifie les conditions d'ecoulement laminaires et turbulentes, toutefois le cout des essais experimentaux a seulement permis d'avoir un apercu du phenomene global. Une deuxieme serie d'essais fut realisee numeriquement a l'Universite de Moncton avec l'outil OpenFOAM pour des conditions d'ecoulement laminaire et bidimensionnel. Cette etude a donc comme but de poursuivre l'enquete de l'aerodynamique oscillatoire des jets impactant des parois courbes, mais pour un regime d'ecoulement transitoire, turbulent

  10. Mechanical Homogenization Increases Bacterial Homogeneity in Sputum

    Science.gov (United States)

    Stokell, Joshua R.; Khan, Ammad

    2014-01-01

    Sputum obtained from patients with cystic fibrosis (CF) is highly viscous and often heterogeneous in bacterial distribution. Adding dithiothreitol (DTT) is the standard method for liquefaction prior to processing sputum for molecular detection assays. To determine if DTT treatment homogenizes the bacterial distribution within sputum, we measured the difference in mean total bacterial abundance and abundance of Burkholderia multivorans between aliquots of DTT-treated sputum samples with and without a mechanical homogenization (MH) step using a high-speed dispersing element. Additionally, we measured the effect of MH on bacterial abundance. We found a significant difference between the mean bacterial abundances in aliquots that were subjected to only DTT treatment and those of the aliquots which included an MH step (all bacteria, P = 0.04; B. multivorans, P = 0.05). There was no significant effect of MH on bacterial abundance in sputum. Although our results are from a single CF patient, they indicate that mechanical homogenization increases the homogeneity of bacteria in sputum. PMID:24759710

  11. Functionality and homogeneity.

    NARCIS (Netherlands)

    2011-01-01

    Functionality and homogeneity are two of the five Sustainable Safety principles. The functionality principle aims for roads to have but one exclusive function and distinguishes between traffic function (flow) and access function (residence). The homogeneity principle aims at differences in mass,

  12. Homogenization of Mammalian Cells.

    Science.gov (United States)

    de Araújo, Mariana E G; Lamberti, Giorgia; Huber, Lukas A

    2015-11-02

    Homogenization is the name given to the methodological steps necessary for releasing organelles and other cellular constituents as a free suspension of intact individual components. Most homogenization procedures used for mammalian cells (e.g., cavitation pump and Dounce homogenizer) rely on mechanical force to break the plasma membrane and may be supplemented with osmotic or temperature alterations to facilitate membrane disruption. In this protocol, we describe a syringe-based homogenization method that does not require specialized equipment, is easy to handle, and gives reproducible results. The method may be adapted for cells that require hypotonic shock before homogenization. We routinely use it as part of our workflow to isolate endocytic organelles from mammalian cells. © 2015 Cold Spring Harbor Laboratory Press.

  13. ETUDE - European Trade Union Distance Education.

    Science.gov (United States)

    Creanor, Linda; Walker, Steve

    2000-01-01

    Describes transnational distance learning activities among European trade union educators carried out as part of the European Trade Union Distance Education (ETUDE) project, supported by the European Commission. Highlights include the context of international trade union distance education; tutor training course; tutors' experiences; and…

  14. The SPH homogeneization method

    International Nuclear Information System (INIS)

    Kavenoky, Alain

    1978-01-01

    The homogeneization of a uniform lattice is a rather well understood topic while difficult problems arise if the lattice becomes irregular. The SPH homogeneization method is an attempt to generate homogeneized cross sections for an irregular lattice. Section 1 summarizes the treatment of an isolated cylindrical cell with an entering surface current (in one velocity theory); Section 2 is devoted to the extension of the SPH method to assembly problems. Finally Section 3 presents the generalisation to general multigroup problems. Numerical results are obtained for a PXR rod bundle assembly in Section 4

  15. Homogeneity of Inorganic Glasses

    DEFF Research Database (Denmark)

    Jensen, Martin; Zhang, L.; Keding, Ralf

    2011-01-01

    Homogeneity of glasses is a key factor determining their physical and chemical properties and overall quality. However, quantification of the homogeneity of a variety of glasses is still a challenge for glass scientists and technologists. Here, we show a simple approach by which the homogeneity...... of different glass products can be quantified and ranked. This approach is based on determination of both the optical intensity and dimension of the striations in glasses. These two characteristic values areobtained using the image processing method established recently. The logarithmic ratio between...

  16. Hydrogen Production by Homogeneous Catalysis: Alcohol Acceptorless Dehydrogenation

    DEFF Research Database (Denmark)

    Nielsen, Martin

    2015-01-01

    in hydrogen production from biomass using homogeneous catalysis. Homogeneous catalysis has the advance of generally performing transformations at much milder conditions than traditional heterogeneous catalysis, and hence it constitutes a promising tool for future applications for a sustainable energy sector...

  17. Enhancement of anaerobic sludge digestion by high-pressure homogenization.

    Science.gov (United States)

    Zhang, Sheng; Zhang, Panyue; Zhang, Guangming; Fan, Jie; Zhang, Yuxuan

    2012-08-01

    To improve anaerobic sludge digestion efficiency, the effects of high-pressure homogenization (HPH) conditions on the anaerobic sludge digestion were investigated. The VS and TCOD were significantly removed with the anaerobic digestion, and the VS removal and TCOD removal increased with increasing the homogenization pressure and homogenization cycle number; correspondingly, the accumulative biogas production also increased with increasing the homogenization pressure and homogenization cycle number. The optimal homogenization pressure was 50 MPa for one homogenization cycle and 40 MPa for two homogenization cycles. The SCOD of the sludge supernatant significantly increased with increasing the homogenization pressure and homogenization cycle number due to the sludge disintegration. The relationship between the biogas production and the sludge disintegration showed that the accumulative biogas and methane production were mainly enhanced by the sludge disintegration, which accelerated the anaerobic digestion process and improved the methane content in the biogas. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Observational homogeneity of the Universe

    International Nuclear Information System (INIS)

    Bonnor, W.B.; Ellis, G.F.R.

    1986-01-01

    A new approach to observational homogeneity is presented. The observation that stars and galaxies in distant regions appear similar to those nearby may be taken to imply that matter has had a similar thermodynamic history in widely separated parts of the Universe (the Postulate of Uniform Thermal Histories, or PUTH). The supposition is now made that similar thermodynamic histories imply similar dynamical histories. Then the distant apparent similarity is evidence for spatial homogeneity of the Universe. General Relativity is used to test this idea, taking a perfect fluid model and implementing PUTH by the condition that the density and entropy per baryon shall be the same function of the proper time along all galaxy world-lines. (author)

  19. Homogenization approach in engineering

    International Nuclear Information System (INIS)

    Babuska, I.

    1975-10-01

    Homogenization is an approach which studies the macrobehavior of a medium by its microproperties. Problems with a microstructure play an essential role in such fields as mechanics, chemistry, physics, and reactor engineering. Attention is concentrated on a simple specific model problem to illustrate results and problems typical of the homogenization approach. Only the diffusion problem is treated here, but some statements are made about the elasticity of composite materials. The differential equation is solved for linear cases with and without boundaries and for the nonlinear case. 3 figures, 1 table

  20. Dynamics of homogeneous nucleation

    DEFF Research Database (Denmark)

    Toxværd, Søren

    2015-01-01

    The classical nucleation theory for homogeneous nucleation is formulated as a theory for a density fluctuation in a supersaturated gas at a given temperature. But molecular dynamics simulations reveal that it is small cold clusters which initiates the nucleation. The temperature in the nucleating...

  1. Homogeneous bilateral block shifts

    Indian Academy of Sciences (India)

    Douglas class were classified in [3]; they are unilateral block shifts of arbitrary block size (i.e. dim H(n) can be anything). However, no examples of irreducible homogeneous bilateral block shifts of block size larger than 1 were known until now.

  2. Homogeneity and Entropy

    Science.gov (United States)

    Tignanelli, H. L.; Vazquez, R. A.; Mostaccio, C.; Gordillo, S.; Plastino, A.

    1990-11-01

    RESUMEN. Presentamos una metodologia de analisis de la homogeneidad a partir de la Teoria de la Informaci6n, aplicable a muestras de datos observacionales. ABSTRACT:Standard concepts that underlie Information Theory are employed in order design a methodology that enables one to analyze the homogeneity of a given data sample. Key : DATA ANALYSIS

  3. Homogeneous Poisson structures

    International Nuclear Information System (INIS)

    Shafei Deh Abad, A.; Malek, F.

    1993-09-01

    We provide an algebraic definition for Schouten product and give a decomposition for any homogenenous Poisson structure in any n-dimensional vector space. A large class of n-homogeneous Poisson structures in R k is also characterized. (author). 4 refs

  4. Homogeneous group, research, institution

    Directory of Open Access Journals (Sweden)

    Francesca Natascia Vasta

    2014-09-01

    Full Text Available The work outlines the complex connection among empiric research, therapeutic programs and host institution. It is considered the current research state in Italy. Italian research field is analyzed and critic data are outlined: lack of results regarding both the therapeutic processes and the effectiveness of eating disorders group analytic treatment. The work investigates on an eating disorders homogeneous group, led into an eating disorder outpatient service. First we present the methodological steps the research is based on including the strong connection among theory and clinical tools. Secondly clinical tools are described and the results commented. Finally, our results suggest the necessity of validating some more specifical hypothesis: verifying the relationship between clinical improvement (sense of exclusion and painful emotions reduction and specific group therapeutic processes; verifying the relationship between depressive feelings, relapses and transition trough a more differentiated groupal field.Keywords: Homogeneous group; Eating disorders; Institutional field; Therapeutic outcome

  5. Homogeneous turbulence dynamics

    CERN Document Server

    Sagaut, Pierre

    2018-01-01

    This book provides state-of-the-art results and theories in homogeneous turbulence, including anisotropy and compressibility effects with extension to quantum turbulence, magneto-hydodynamic turbulence  and turbulence in non-newtonian fluids. Each chapter is devoted to a given type of interaction (strain, rotation, shear, etc.), and presents and compares experimental data, numerical results, analysis of the Reynolds stress budget equations and advanced multipoint spectral theories. The role of both linear and non-linear mechanisms is emphasized. The link between the statistical properties and the dynamics of coherent structures is also addressed. Despite its restriction to homogeneous turbulence, the book is of interest to all people working in turbulence, since the basic physical mechanisms which are present in all turbulent flows are explained. The reader will find a unified presentation of the results and a clear presentation of existing controversies. Special attention is given to bridge the results obta...

  6. Homogen Mur - et udviklingsprojekt

    DEFF Research Database (Denmark)

    Dahl, Torben; Beim, Anne; Sørensen, Peter

    1997-01-01

    Mølletorvet i Slagelse er det første byggeri i Danmark, hvor ydervæggen er udført af homogene bærende og isolerende teglblokke. Byggeriet viser en række af de muligheder, der både med hensyn til konstruktioner, energiforhold og arkitektur ligger i anvendelsen af homogent blokmurværk.......Mølletorvet i Slagelse er det første byggeri i Danmark, hvor ydervæggen er udført af homogene bærende og isolerende teglblokke. Byggeriet viser en række af de muligheder, der både med hensyn til konstruktioner, energiforhold og arkitektur ligger i anvendelsen af homogent blokmurværk....

  7. Homogenization of resonant chiral metamaterials

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Menzel, C.; Rockstuhl, Carsten

    2010-01-01

    Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as, e.g., propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size...... an analytical criterion for performing the homogenization and a tool to predict the homogenization limit. We show that strong coupling between meta-atoms of chiral metamaterials may prevent their homogenization at all....

  8. Homogeneous M2 duals

    International Nuclear Information System (INIS)

    Figueroa-O’Farrill, José; Ungureanu, Mara

    2016-01-01

    Motivated by the search for new gravity duals to M2 branes with N>4 supersymmetry — equivalently, M-theory backgrounds with Killing superalgebra osp(N|4) for N>4 — we classify (except for a small gap) homogeneous M-theory backgrounds with symmetry Lie algebra so(n)⊕so(3,2) for n=5,6,7. We find that there are no new backgrounds with n=6,7 but we do find a number of new (to us) backgrounds with n=5. All backgrounds are metrically products of the form AdS 4 ×P 7 , with P riemannian and homogeneous under the action of SO(5), or S 4 ×Q 7 with Q lorentzian and homogeneous under the action of SO(3,2). At least one of the new backgrounds is supersymmetric (albeit with only N=2) and we show that it can be constructed from a supersymmetric Freund-Rubin background via a Wick rotation. Two of the new backgrounds have only been approximated numerically.

  9. Homogeneous M2 duals

    Energy Technology Data Exchange (ETDEWEB)

    Figueroa-O’Farrill, José [School of Mathematics and Maxwell Institute for Mathematical Sciences,The University of Edinburgh,James Clerk Maxwell Building, The King’s Buildings, Peter Guthrie Tait Road,Edinburgh EH9 3FD, Scotland (United Kingdom); Ungureanu, Mara [Humboldt-Universität zu Berlin, Institut für Mathematik,Unter den Linden 6, 10099 Berlin (Germany)

    2016-01-25

    Motivated by the search for new gravity duals to M2 branes with N>4 supersymmetry — equivalently, M-theory backgrounds with Killing superalgebra osp(N|4) for N>4 — we classify (except for a small gap) homogeneous M-theory backgrounds with symmetry Lie algebra so(n)⊕so(3,2) for n=5,6,7. We find that there are no new backgrounds with n=6,7 but we do find a number of new (to us) backgrounds with n=5. All backgrounds are metrically products of the form AdS{sub 4}×P{sup 7}, with P riemannian and homogeneous under the action of SO(5), or S{sup 4}×Q{sup 7} with Q lorentzian and homogeneous under the action of SO(3,2). At least one of the new backgrounds is supersymmetric (albeit with only N=2) and we show that it can be constructed from a supersymmetric Freund-Rubin background via a Wick rotation. Two of the new backgrounds have only been approximated numerically.

  10. Benchmarking homogenization algorithms for monthly data

    Directory of Open Access Journals (Sweden)

    V. K. C. Venema

    2012-01-01

    Full Text Available The COST (European Cooperation in Science and Technology Action ES0601: advances in homogenization methods of climate series: an integrated approach (HOME has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies and because they represent two important types of statistics (additive and multiplicative. The algorithms were validated against a realistic benchmark dataset. The benchmark contains real inhomogeneous data as well as simulated data with inserted inhomogeneities. Random independent break-type inhomogeneities with normally distributed breakpoint sizes were added to the simulated datasets. To approximate real world conditions, breaks were introduced that occur simultaneously in multiple station series within a simulated network of station data. The simulated time series also contained outliers, missing data periods and local station trends. Further, a stochastic nonlinear global (network-wide trend was added.

    Participants provided 25 separate homogenized contributions as part of the blind study. After the deadline at which details of the imposed inhomogeneities were revealed, 22 additional solutions were submitted. These homogenized datasets were assessed by a number of performance metrics including (i the centered root mean square error relative to the true homogeneous value at various averaging scales, (ii the error in linear trend estimates and (iii traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Contingency scores by themselves are not very informative. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve

  11. Homogeneous Finsler Spaces

    CERN Document Server

    Deng, Shaoqiang

    2012-01-01

    "Homogeneous Finsler Spaces" is the first book to emphasize the relationship between Lie groups and Finsler geometry, and the first to show the validity in using Lie theory for the study of Finsler geometry problems. This book contains a series of new results obtained by the author and collaborators during the last decade. The topic of Finsler geometry has developed rapidly in recent years. One of the main reasons for its surge in development is its use in many scientific fields, such as general relativity, mathematical biology, and phycology (study of algae). This monograph introduc

  12. Homogeneity spoil spectroscopy

    International Nuclear Information System (INIS)

    Hennig, J.; Boesch, C.; Martin, E.; Grutter, R.

    1987-01-01

    One of the problems of in vivo MR spectroscopy of P-31 is spectra localization. Surface coil spectroscopy, which is the method of choice for clinical applications, suffers from the high-intensity signal from subcutaneous muscle tissue, which masks the spectrum of interest from deeper structures. In order to suppress this signal while maintaining the simplicity of surface coil spectroscopy, the authors introduced a small sheet of ferromagnetically dotted plastic between the surface coil and the body. This sheet destroys locally the field homogeneity and therefore all signal from structures around the coil. The very high reproducibility of the simple experimental procedure allows long-term studies important for monitoring tumor therapy

  13. Study of the {sup 14}C benzimidazole distribution in mice after inter-peritoneal injection; Etude de la repartition du benzimidazole {sup 14}C chez la souris apres injection intraperitoneale

    Energy Technology Data Exchange (ETDEWEB)

    Tyortyalian, C [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1965-07-01

    In order to provide further information on the mechanism of benzimidazole radioprotective activity, this work studies the tissual repartition in mice of this compound labelled with carbon 14. Experiments have showed that benzimidazole distribution is fast and homogeneous in all the tissues, but however affinity appears at the level of stomach and gastric content. Elimination is made through the urinary system and is very fast. (author) [French] Dans le cadre de l'etude du mecanisme de l'action radioprotectrice du benzimidazole, ce travail a pour objet l'etude de la repartition tissulaire chez la souris de ce compose marque au carbone 14. L'experimentation a montre que le benzimidazole se repartit tres rapidement et de facon pratiquement homogene dans tous les tissus, avec toutefois une affinite paraissant se manifester au niveau de l'estomac et du contenu gastrique. L'elimination, qui se fait par voie urinaire, est tres rapide. (auteur)

  14. Etude expérimentale et théorique de la structure électronique de l'aluminium en conditions extrêmes par spectroscopie d'absorption X

    OpenAIRE

    Festa , Floriane

    2013-01-01

    Matter in extreme conditions belongs to Warm Dense Matter regime which lays between dense plasma regime and condensed matter. This regime is still not well known, indeed it is very complex to generate such plasma in the laboratory to get experimental data and validate models. The goal of this thesis is to study electronic structure of aluminum in extreme conditions with X-ray absorption spectroscopy. Experimentally aluminum has reached high densities and high temperatures, up to now unexplore...

  15. Homogeneous instantons in bigravity

    International Nuclear Information System (INIS)

    Zhang, Ying-li; Sasaki, Misao; Yeom, Dong-han

    2015-01-01

    We study homogeneous gravitational instantons, conventionally called the Hawking-Moss (HM) instantons, in bigravity theory. The HM instantons describe the amplitude of quantum tunneling from a false vacuum to the true vacuum. Corrections to General Relativity (GR) are found in a closed form. Using the result, we discuss the following two issues: reduction to the de Rham-Gabadadze-Tolley (dRGT) massive gravity and the possibility of preference for a large e-folding number in the context of the Hartle-Hawking (HH) no-boundary proposal. In particular, concerning the dRGT limit, it is found that the tunneling through the so-called self-accelerating branch is exponentially suppressed relative to the normal branch, and the probability becomes zero in the dRGT limit. As far as HM instantons are concerned, this could imply that the reduction from bigravity to the dRGT massive gravity is ill-defined.

  16. The relationship between continuum homogeneity and statistical homogeneity in cosmology

    International Nuclear Information System (INIS)

    Stoeger, W.R.; Ellis, G.F.R.; Hellaby, C.

    1987-01-01

    Although the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe models are based on the concept that the Universe is spatially homogeneous, up to the present time no definition of this concept has been proposed that could in principle be tested by observation. Such a definition is here proposed, based on a simple spatial averaging procedure, which relates observable properties of the Universe to the continuum homogeneity idea that underlies the FLRW models. It turns out that the statistical homogeneity often used to describe the distribution of matter on a large scale does not imply spatial homogeneity according to this definition, and so cannot be simply related to a FLRW Universe model. Values are proposed for the homogeneity parameter and length scale of homogeneity of the Universe. (author)

  17. Experimental study of the mechanisms of CO{sub 2} capture by calcium cycle under circulating fluidized bed conditions; Etude experimentale des mecanismes de capture du CO{sub 2} par cycle calcium en lit fluidise circulant

    Energy Technology Data Exchange (ETDEWEB)

    Hoteit, A

    2006-06-15

    The work undertaken in this Thesis in partnership with department R and D of ALSTOM Power Boilers, CEMEX and the ADEME, relates to the experimental study of various phenomena associated to CO{sub 2} capture under circulating fluidized bed conditions. The size of particles, temperature and the CO{sub 2} concentration have an influence on the limestone calcination reaction. The reaction of carbonation of lime is not total. During successive cycles of calcination/carbonation, the rate of carbonation obtained with hydrated lime is increasingly higher than that obtained with the lime. Under continuously reducing conditions, the decomposition of sulphates present in the bed ashes is not total. This decomposition is total under reduction/oxidation cycles. A modeling of calcination allowed to determine the intrinsic kinetic constants of calcination and carbonation. (author)

  18. Studies of neo-formed phases occurring during spent nuclear fuel dissolution in geological repository: influence of silicate ions; Etude des phases neoformees lors de la dissolution du combustible nucleaire en condition de stockage geologique: influence des ions silicate

    Energy Technology Data Exchange (ETDEWEB)

    Robit-Pointeau, V

    2005-12-15

    Spent nuclear fuel alteration in deep storage conditions may proceed by local oxidising conditions at the fuel / water interface under influence of alpha irradiation. However, due to the strong redox buffer capacity of the near-field materials (especially the canister and the geological media), most of the near-field environment will remain reducing. Due to the relative high concentration in silica in such system, coffinite USiO{sub 4}.n(H{sub 2}O) may be a relevant phase to consider as it has been suggested from the natural analogues observations (Oklo). The aim of this work was to assess the relevance of coffinitisation of the spent fuel phenomena. The results of the experimental work contest the thermodynamic predictions. Instead of coffinite, a new U(IV)-Si phase has been observed in water simulating storage conditions. The thermodynamic data on coffinite validated by OECD are based on the average concentration of dissolved silica present in natural system containing uraninite and quartz. As the silica concentration in natural groundwaters is more probably controlled by minerals like chalcedony or silica gel, the coffinite present with uraninite in such systems, is probably not in equilibrium even in 2-billion years- old geological sites. Based on the results of this study, coffinitisation of the spent nuclear fuel in deep geological disposal is not anticipated to be a dominant short term process. (author)

  19. A non-asymptotic homogenization theory for periodic electromagnetic structures.

    Science.gov (United States)

    Tsukerman, Igor; Markel, Vadim A

    2014-08-08

    Homogenization of electromagnetic periodic composites is treated as a two-scale problem and solved by approximating the fields on both scales with eigenmodes that satisfy Maxwell's equations and boundary conditions as accurately as possible. Built into this homogenization methodology is an error indicator whose value characterizes the accuracy of homogenization. The proposed theory allows one to define not only bulk, but also position-dependent material parameters (e.g. in proximity to a physical boundary) and to quantify the trade-off between the accuracy of homogenization and its range of applicability to various illumination conditions.

  20. In vivo dosimetry study of semi-conductors EPD-20 in total body irradiation technique; Etude de la dosimetrie in vivo par semi-conducteurs EPD-20 dans les conditions de l'irradiation corporelle totale

    Energy Technology Data Exchange (ETDEWEB)

    Besbes, M.; Kochbati, L.; Ben Abdennabi, A.; Abdessaied, S.; Salem, L.; Frikha, H.; Nasr Ben Ammar, C.; Hentati, D.; Gargouri, W.; Messai, T.; Benna, F.; Maalej, M. [Institut Salah-Azaiz, Service de radiotherapie oncologique, Tunis (Tunisia); Mahjoubi, H. [Institut superieur des technologies medicales de Tunis, Dept. de biophysique, Tunis (Tunisia); Farhat, L. [CHU Habib-Bourguiba, Service de radiotherapie oncologique, Sfax (Tunisia)

    2010-01-15

    Purpose: The objective of this work was the study of in vivo dosimetry performed in a series of 54 patients receiving total body irradiation (T.B.I.) at the Salah-Azaiz Institute of Tunis since 2004. In vivo dosimetry measurements were compared to analytically calculated doses from monitor units delivered. Patients and method: The irradiation was conducted by a linear accelerator (Clinac 1800, Varian, Palo Alto, USA) using nominal X-rays energies of 6 MV and 18 MV, depending on the thickness of the patient at the abdomen. The dose was measured by semi-conductors p-type E.P.D.-20. These diodes were calibrated in advance with an ionization chamber 'P.T.W. Farmer' type of 0.6 cm{sup 3} and were placed on the surface of plexiglas phantom in the same T.B.I. conditions. A study of dosimetric characteristics of semi-conductors E.P.D.-20 was carried out as a function of beam direction and temperature. Afterwards, we conducted a comparative analysis of doses measured using these detectors during irradiation to those calculated retrospectively from monitor units delivered to each patient conditioned by T.B.I.. Results: Experience showed that semi-conductors are sensitive to the angle of beam radiation (0-90 degrees) and the temperature (22-40 Celsius degrees). The maximum variation is respectively 5 and 7%, but in our irradiation conditions these correction factors are less than 1%. The analysis of the results of the in vivo dosimetry had shown that the ratio of the average measured doses and analytically calculated doses at the abdomen, mediastinum, right lung and head are 1.005, 1.007, 1.0135 and 1.008 with a standard deviation 'type A' respectively of 3.04, 2.37, 7.09 et 4.15%. Conclusion: In vivo dosimetry by semi-conductors is in perfect agreement with dosimetry by calculation. However, in vivo dosimetry using semiconductors is the only technique that can reflect the dose actually received instantly by the patient during T.B.I. given the many factors

  1. Notes on a homogeneous reactor project; Idees sur un projet de reacteur homogene

    Energy Technology Data Exchange (ETDEWEB)

    Benveniste, J; Bernot, J; Eidelman, D; Grenon, M; Portes, L; Raspaud, G; Tachon, J; Vendryes, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Berthod, L; Cohen de Lara, G; Delachanal, M; Fontanet, P; Halbronn, G [Societe Grenobloise d' Etudes et d' Applications Hydrauliques, 38 (France)

    1958-07-01

    An attempt has been made to develop certain ideas concerning homogeneous reactors. The project under consideration is based on the simultaneous use of a suspension of uranium dispersed in heavy or light water and of boiling in the reactor for heat extraction. However, the studies of suspensions and of boiling are relatively independent and can also be developed for reactors of different types using one or the other. Our aim is a minimum investment in fissile material; for this we propose to extract the steam directly from the core and to make use of a cyclone to accelerate this extraction; a cyclone-type circulation creating a field of increasing tangential velocities of the fluid towards the axis causes the droplets of vapour to accelerate towards the axial vortex in which they are collected; the steam output is then evacuated to the external heat utilisation system, for example an exchanger of the condenser-boiler type. The input speed of water into the reactor being one of the important parameters in the running of the pile, a spiral supply input chamber is used, allowing this speed to be regulated in amount and direction. (author)Fren. [French] Nous nous sommes attaches a developper certaines idees relatives aux piles homogenes. Le projet que nous etudions est base sur l'emploi simultane d'une suspension contenant de l'uranium disperse dans l'eau legere ou lourde et de l'ebullition dans le reacteur pour l'extraction de chaleur. Neanmoins, les etudes de suspensions et d'ebullition sont relativement independantes et peuvent egalement etre developpees pour des reacteurs de type different utilisant l'une ou l'autre. Le but que nous cherchons a atteindre est un investissement minimum en matiere fissile; pour cela, nous proposons d'extraire directement la vapeur dans le coeur et de recourir a un dispositif cyclone pour accelerer cette extraction; une circulation type cyclone creant un champ de vitesses tangentielles du fluide croissantes veraxe a pour effet d

  2. Homogenization of resonant chiral metamaterials

    OpenAIRE

    Andryieuski, Andrei; Menzel, Christoph; Rockstuhl, Carsten; Malureanu, Radu; Lederer, Falk; Lavrinenko, Andrei

    2010-01-01

    Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as e.g. propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size a critical density exists above which increasing coupling between neighboring meta-atoms prevails a reasonable homogenization. On the contrary, a dilution in excess will induce features reminiscent to pho...

  3. Bilipschitz embedding of homogeneous fractals

    OpenAIRE

    Lü, Fan; Lou, Man-Li; Wen, Zhi-Ying; Xi, Li-Feng

    2014-01-01

    In this paper, we introduce a class of fractals named homogeneous sets based on some measure versions of homogeneity, uniform perfectness and doubling. This fractal class includes all Ahlfors-David regular sets, but most of them are irregular in the sense that they may have different Hausdorff dimensions and packing dimensions. Using Moran sets as main tool, we study the dimensions, bilipschitz embedding and quasi-Lipschitz equivalence of homogeneous fractals.

  4. Enrollment of a population-based cohort of newborns at higher risk of developing a chronic condition: the EDEN study. Etude du Developpement des Nouveau-nés Study.

    Science.gov (United States)

    Addor, V; Santos-Eggimann, B; Fawer, C L; Paccaud, F; Calame, A

    1997-04-01

    To describe the methods used at birth to recruit a population-based cohort of newborns of all birthweights at higher risk of having a chronic condition, and to present baseline results. Screening of all newborns at hospital discharge for five non-exclusive criteria: (1) low birthweight (LBW), (2) congenital anomalies or genetic disease, (3) specified conditions associated with a high probability of chronicity, (4) referral to a neonatal intensive care unit (NICU), (5) or defined social problems. Calculation of Hobel risk scores for children satisfying > or = 1 criterion. All 6477 live births delivered in the 19 maternity hospitals of a geographically defined region (Vaud, Switzerland) to resident mothers in 1993-1994. Twelve per cent (n = 760) of newborns met > or = 1 criterion: 6.3% of all newborns had an LBW (criterion 1), 2.4% had a birth defect, 0.9% met criterion (3), 4.4% stayed in an NICU and 1.6% had serious social problems. Hobel prenatal score was high (> or = 10 points) for 41% of children with > or = 1 criterion, the intrapartum score for 87% and the neonatal score for 68%. Most newborns identified by the above simple criteria also had elevated perinatal risks. The validity of the criteria will later be tested against the results of the examinations of children with > or = 1 criterion at 18 months and 4 years of age, but the assessment at birth already shows that normal birthweight (NBW) children, in agreement with previous studies, contribute half the children at high risk perinatally.

  5. Mise au point du rheometre a cisaillement annulaire pour l'etude de rheologie d'un mastic bitumineux avec verre incorpore =

    Science.gov (United States)

    El Mansouri, Souleimane

    Dans le domaine viscoelastique lineaire (VEL, domaine des petites deformations), le comportement thermomecanique du bitume et du mastic bitumineux (melange uniforme de bitume et de fillers) a ete caracterise au Laboratoire des Chaussees et Materiaux Bitumineux (LCMB) de l'Ecole de technologie superieure (ETS) avec l'appui de nos partenaires externes : la Societe des Alcools du Quebec (SAQ) et Eco Entreprises Quebec (EEQ). Les proprietes rheologiques des bitumes et des mastics ont ete mesurees grâce a un nouvel outil d'investigation appele, Rheometre a Cisaillement Annulaire (RCA), sous differentes conditions de chargement. Cet appareil permet non seulement de solliciter des eprouvettes de tailles importantes par rapport a celles utilisees lors des essais classiques, mais aussi d'effectuer des essais en conditions quasi-homogenes, ce qui permet de donner acces a la loi de comportement des materiaux. Les essais sont realises sur une large gamme de temperatures et de frequences (de -15 °C a 45°C et de 0,03Hz a 10 Hz). Cette etude a ete menee principalement pour comparer le comportement d'un bitume avec celui d'un mastic bitumineux dans le domaine des petites deformations. neanmoins, dans une seconde perspective, on s'interesse a l'influence des fillers de verre de post-consommation sur le comportement d'un mastic a faibles niveaux de deformations en comparant l'evolution des modules complexes de cisaillements (G*) d'un mastic avec fillers de verre et un mastic avec fillers conventionnels (calcaire). Enfin, le modele analogique 2S2P1D est utilise pour simuler le comportement viscoelastique lineaire des bitumes et des mastics bitumineux testes lors de la campagne experimentale.

  6. Heat transfer tests conducted on full-scale model, to investigate cooling conditions of EL.3 experimental reactor; Essais de transmission de chaleur sur maquette pour l'etude du refroidissement de la pile EL 3

    Energy Technology Data Exchange (ETDEWEB)

    Raievski, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Butzbach, M; Domenjoud, M [Alsthom, 75 - Paris (France); Bousquet, M [Chantiers de l' Atlantique (France); Braudeau, M; Milliat, M [Electricite de France (EDF), 75 - Paris (France)

    1958-07-01

    For such high heat flux density as is released in the channels of EL3 reactor (2.10{sup 6} kcal/m{sup 2}h on the hottest point) cooling conditions have proved to be satisfactory, that is free from nucleate boiling. The arrangements provided for these tests and the technique used for measurements (of temperature particularly) are specified. Two fields have been investigated: in the former (forced convection without nucleate boiling) a good agreement is found with Colburn's formula. The influence of the ratio L/D is pointed out. The latter field is of forced convection with beginning of nucleate boiling; there the observed raise of the transfer coefficient has been shown occurring with some delay. (author)Fren. [French] A la valeur elevee prevue pour la densite de flux de chaleur (2.10{sup 6} kcal/m{sup 2}h au point le plus chaud) il est verifie que le refroidissement de la pile s'effectue normalement (sans ebullition de paroi). Les essais sont menes sur la maquette grandeur nature d'un canal d'EL3. Les dispositions relatives a la conduite des essais et a la technique des mesures (de temperature en particulier) sont precisees. Deux domaines sont etudies; pour t{sub p} < T{sub sat} (convection forcee sans ebullition de paroi) on constate un bon accord avec la formule de Colburn, avec toutefois l'influence du rapport L/D. Pour t{sub p} < T{sub sat} (debut d'ebullition) l'augmentation prevue du coefficient de transmission presente un certain retard. (auteur)

  7. Homogeneous versus heterogeneous zeolite nucleation

    NARCIS (Netherlands)

    Dokter, W.H.; Garderen, van H.F.; Beelen, T.P.M.; Santen, van R.A.; Bras, W.

    1995-01-01

    Aggregates of fractal dimension were found in the intermediate gel phases that organize prior to nucleation and crystallization (shown right) of silicalite from a homogeneous reaction mixture. Small- and wide-angle X-ray scattering studies prove that for zeolites nucleation may be homogeneous or

  8. Homogeneous crystal nucleation in polymers.

    Science.gov (United States)

    Schick, C; Androsch, R; Schmelzer, J W P

    2017-11-15

    The pathway of crystal nucleation significantly influences the structure and properties of semi-crystalline polymers. Crystal nucleation is normally heterogeneous at low supercooling, and homogeneous at high supercooling, of the polymer melt. Homogeneous nucleation in bulk polymers has been, so far, hardly accessible experimentally, and was even doubted to occur at all. This topical review summarizes experimental findings on homogeneous crystal nucleation in polymers. Recently developed fast scanning calorimetry, with cooling and heating rates up to 10 6 K s -1 , allows for detailed investigations of nucleation near and even below the glass transition temperature, including analysis of nuclei stability. As for other materials, the maximum homogeneous nucleation rate for polymers is located close to the glass transition temperature. In the experiments discussed here, it is shown that polymer nucleation is homogeneous at such temperatures. Homogeneous nucleation in polymers is discussed in the framework of the classical nucleation theory. The majority of our observations are consistent with the theory. The discrepancies may guide further research, particularly experiments to progress theoretical development. Progress in the understanding of homogeneous nucleation is much needed, since most of the modelling approaches dealing with polymer crystallization exclusively consider homogeneous nucleation. This is also the basis for advancing theoretical approaches to the much more complex phenomena governing heterogeneous nucleation.

  9. Homogenization theory in reactor lattices

    International Nuclear Information System (INIS)

    Benoist, P.

    1986-02-01

    The purpose of the theory of homogenization of reactor lattices is to determine, by the mean of transport theory, the constants of a homogeneous medium equivalent to a given lattice, which allows to treat the reactor as a whole by diffusion theory. In this note, the problem is presented by laying emphasis on simplicity, as far as possible [fr

  10. Structural changes in heat resisting high nickel alloys during homogenization

    International Nuclear Information System (INIS)

    Kleshchev, A.S.; Korneeva, N.N.; Yurina, O.M.; Guzej, L.S.

    1981-01-01

    Effect of homogenization on the structure and technological plasticity of the KhN73MBTYu and KhN62BMKTYu alloys during treatment with pressure is investigated taking into account peculiarities if the phase composition. It is shown that homogenization of the KhN73MBTYu and KhN62BMKTYu alloys increases the technological plasticity. Homogenization efficiency is conditioned by the change of the grain boundaries and carbide morphology as well as by homogeneous distribution of the large γ'-phase [ru

  11. Cross section homogenization analysis for a simplified Candu reactor

    International Nuclear Information System (INIS)

    Pounders, Justin; Rahnema, Farzad; Mosher, Scott; Serghiuta, Dumitru; Turinsky, Paul; Sarsour, Hisham

    2008-01-01

    The effect of using zero current (infinite medium) boundary conditions to generate bundle homogenized cross sections for a stylized half-core Candu reactor problem is examined. Homogenized cross section from infinite medium lattice calculations are compared with cross sections homogenized using the exact flux from the reference core environment. The impact of these cross section differences is quantified by generating nodal diffusion theory solutions with both sets of cross sections. It is shown that the infinite medium spatial approximation is not negligible, and that ignoring the impact of the heterogeneous core environment on cross section homogenization leads to increased errors, particularly near control elements and the core periphery. (authors)

  12. Exponential Stability of Switched Positive Homogeneous Systems

    Directory of Open Access Journals (Sweden)

    Dadong Tian

    2017-01-01

    Full Text Available This paper studies the exponential stability of switched positive nonlinear systems defined by cooperative and homogeneous vector fields. In order to capture the decay rate of such systems, we first consider the subsystems. A sufficient condition for exponential stability of subsystems with time-varying delays is derived. In particular, for the corresponding delay-free systems, we prove that this sufficient condition is also necessary. Then, we present a sufficient condition of exponential stability under minimum dwell time switching for the switched positive nonlinear systems. Some results in the previous literature are extended. Finally, a numerical example is given to demonstrate the effectiveness of the obtained results.

  13. Homogenization of High-Contrast Brinkman Flows

    KAUST Repository

    Brown, Donald L.

    2015-04-16

    Modeling porous flow in complex media is a challenging problem. Not only is the problem inherently multiscale but, due to high contrast in permeability values, flow velocities may differ greatly throughout the medium. To avoid complicated interface conditions, the Brinkman model is often used for such flows [O. Iliev, R. Lazarov, and J. Willems, Multiscale Model. Simul., 9 (2011), pp. 1350--1372]. Instead of permeability variations and contrast being contained in the geometric media structure, this information is contained in a highly varying and high-contrast coefficient. In this work, we present two main contributions. First, we develop a novel homogenization procedure for the high-contrast Brinkman equations by constructing correctors and carefully estimating the residuals. Understanding the relationship between scales and contrast values is critical to obtaining useful estimates. Therefore, standard convergence-based homogenization techniques [G. A. Chechkin, A. L. Piatniski, and A. S. Shamev, Homogenization: Methods and Applications, Transl. Math. Monogr. 234, American Mathematical Society, Providence, RI, 2007, G. Allaire, SIAM J. Math. Anal., 23 (1992), pp. 1482--1518], although a powerful tool, are not applicable here. Our second point is that the Brinkman equations, in certain scaling regimes, are invariant under homogenization. Unlike in the case of Stokes-to-Darcy homogenization [D. Brown, P. Popov, and Y. Efendiev, GEM Int. J. Geomath., 2 (2011), pp. 281--305, E. Marusic-Paloka and A. Mikelic, Boll. Un. Mat. Ital. A (7), 10 (1996), pp. 661--671], the results presented here under certain velocity regimes yield a Brinkman-to-Brinkman upscaling that allows using a single software platform to compute on both microscales and macroscales. In this paper, we discuss the homogenized Brinkman equations. We derive auxiliary cell problems to build correctors and calculate effective coefficients for certain velocity regimes. Due to the boundary effects, we construct

  14. Homogeneous Spaces and Equivariant Embeddings

    CERN Document Server

    Timashev, DA

    2011-01-01

    Homogeneous spaces of linear algebraic groups lie at the crossroads of algebraic geometry, theory of algebraic groups, classical projective and enumerative geometry, harmonic analysis, and representation theory. By standard reasons of algebraic geometry, in order to solve various problems on a homogeneous space it is natural and helpful to compactify it keeping track of the group action, i.e. to consider equivariant completions or, more generally, open embeddings of a given homogeneous space. Such equivariant embeddings are the subject of this book. We focus on classification of equivariant em

  15. A generalized model for homogenized reflectors

    International Nuclear Information System (INIS)

    Pogosbekyan, Leonid; Kim, Yeong Il; Kim, Young Jin; Joo, Hyung Kook

    1996-01-01

    A new concept of equivalent homogenization is proposed. The concept employs new set of homogenized parameters: homogenized cross sections (XS) and interface matrix (IM), which relates partial currents at the cell interfaces. The idea of interface matrix generalizes the idea of discontinuity factors (DFs), proposed and developed by K. Koebke and K. Smith. The method of K. Smith can be simulated within framework of new method, while the new method approximates hetero-geneous cell better in case of the steep flux gradients at the cell interfaces. The attractive shapes of new concept are:improved accuracy, simplicity of incorporation in the existing codes, equal numerical expenses in comparison to the K. Smith's approach. The new concept is useful for: (a) explicit reflector/baffle simulation; (b)control blades simulation; (c) mixed UO 2 /MOX core simulation. The offered model has been incorporated in the finite difference code and in the nodal code PANBOX. The numerical results show good accuracy of core calculations and insensitivity of homogenized parameters with respect to in-core conditions

  16. PENULISAN ETUDE-ETUDE MUSIK TALEMPONG UNGGAN (Sebuah Usaha Pembelajaran Musik Tradisi Berbasis Literatur

    Directory of Open Access Journals (Sweden)

    Asri MK

    2014-12-01

    Full Text Available “Talempong unggan”, a traditional music from Minangkabau community particularly in Unggan, Sumpur Kudus, Sijunjung Regency, West Sumatera Indonesia is classified into genre of “talempong duduak” (rea. Due to its special musical concept and the playing technics, this traditional music is selected as a practising course in the Karawitan Department of Indonesian Institute of Art (ISI Padang Panjang since 1993 till now. In a system of class learning with many students, Talempong Unggan definitely needs supporting methods and learning technics suitable for the course where the students can reach their maximum skills. All the melody of “talempong unggan” that has been made as a material of practice is transcribed to the system of numeric notation and rhythm motive of “gendang” and “aguang” which is written into signs and special notation. All of qualitative data is formulated into finding methods, technics and etude of learning ensamble of Talempong Unggan the traditional music that learned in Karawitan Department of ISI Padang Panjang. Key words: Talempong Unggan, Methods, Technics, Etude

  17. Qualitative analysis of homogeneous universes

    International Nuclear Information System (INIS)

    Novello, M.; Araujo, R.A.

    1980-01-01

    The qualitative behaviour of cosmological models is investigated in two cases: Homogeneous and isotropic Universes containing viscous fluids in a stokesian non-linear regime; Rotating expanding universes in a state which matter is off thermal equilibrium. (Author) [pt

  18. A second stage homogenization method

    International Nuclear Information System (INIS)

    Makai, M.

    1981-01-01

    A second homogenization is needed before the diffusion calculation of the core of large reactors. Such a second stage homogenization is outlined here. Our starting point is the Floquet theorem for it states that the diffusion equation for a periodic core always has a particular solution of the form esup(j)sup(B)sup(x) u (x). It is pointed out that the perturbation series expansion of function u can be derived by solving eigenvalue problems and the eigenvalues serve to define homogenized cross sections. With the help of these eigenvalues a homogenized diffusion equation can be derived the solution of which is cos Bx, the macroflux. It is shown that the flux can be expressed as a series of buckling. The leading term in this series is the well known Wigner-Seitz formula. Finally three examples are given: periodic absorption, a cell with an absorber pin in the cell centre, and a cell of three regions. (orig.)

  19. Homogenization methods for heterogeneous assemblies

    International Nuclear Information System (INIS)

    Wagner, M.R.

    1980-01-01

    The third session of the IAEA Technical Committee Meeting is concerned with the problem of homogenization of heterogeneous assemblies. Six papers will be presented on the theory of homogenization and on practical procedures for deriving homogenized group cross sections and diffusion coefficients. That the problem of finding so-called ''equivalent'' diffusion theory parameters for the use in global reactor calculations is of great practical importance. In spite of this, it is fair to say that the present state of the theory of second homogenization is far from being satisfactory. In fact, there is not even a uniquely accepted approach to the problem of deriving equivalent group diffusion parameters. Common agreement exists only about the fact that the conventional flux-weighting technique provides only a first approximation, which might lead to acceptable results in certain cases, but certainly does not guarantee the basic requirement of conservation of reaction rates

  20. Spinor structures on homogeneous spaces

    International Nuclear Information System (INIS)

    Lyakhovskii, V.D.; Mudrov, A.I.

    1993-01-01

    For multidimensional models of the interaction of elementary particles, the problem of constructing and classifying spinor fields on homogeneous spaces is exceptionally important. An algebraic criterion for the existence of spinor structures on homogeneous spaces used in multidimensional models is developed. A method of explicit construction of spinor structures is proposed, and its effectiveness is demonstrated in examples. The results are of particular importance for harmonic decomposition of spinor fields

  1. A personal view on homogenization

    International Nuclear Information System (INIS)

    Tartar, L.

    1987-02-01

    The evolution of some ideas is first described. Under the name homogenization are collected all the mathematical results who help understanding the relations between the microstructure of a material and its macroscopic properties. Homogenization results are given through a critically detailed bibliography. The mathematical models given are systems of partial differential equations, supposed to describe some properties at a scale ε and we want to understand what will happen to the solutions if ε tends to 0

  2. Sewage sludge solubilization by high-pressure homogenization.

    Science.gov (United States)

    Zhang, Yuxuan; Zhang, Panyue; Guo, Jianbin; Ma, Weifang; Fang, Wei; Ma, Boqiang; Xu, Xiangzhe

    2013-01-01

    The behavior of sludge solubilization using high-pressure homogenization (HPH) treatment was examined by investigating the sludge solid reduction and organics solubilization. The sludge volatile suspended solids (VSS) decreased from 10.58 to 6.67 g/L for the sludge sample with a total solids content (TS) of 1.49% after HPH treatment at a homogenization pressure of 80 MPa with four homogenization cycles; total suspended solids (TSS) correspondingly decreased from 14.26 to 9.91 g/L. About 86.15% of the TSS reduction was attributed to the VSS reduction. The increase of homogenization pressure from 20 to 80 MPa or homogenization cycle number from 1 to 4 was favorable to the sludge organics solubilization, and the protein and polysaccharide solubilization linearly increased with the soluble chemical oxygen demand (SCOD) solubilization. More proteins were solubilized than polysaccharides. The linear relationship between SCOD solubilization and VSS reduction had no significant change under different homogenization pressures, homogenization cycles and sludge solid contents. The SCOD of 1.65 g/L was solubilized for the VSS reduction of 1.00 g/L for the three experimental sludge samples with a TS of 1.00, 1.49 and 2.48% under all HPH operating conditions. The energy efficiency results showed that the HPH treatment at a homogenization pressure of 30 MPa with a single homogenization cycle for the sludge sample with a TS of 2.48% was the most energy efficient.

  3. A new concept of equivalent homogenization method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Jin; Pogoskekyan, Leonid; Kim, Young Il; Ju, Hyung Kook; Chang, Moon Hee [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1996-07-01

    A new concept of equivalent homogenization is proposed. The concept employs new set of homogenized parameters: homogenized cross sections (XS) and interface matrix (IM), which relates partial currents at the cell interfaces. The idea of interface matrix generalizes the idea of discontinuity factors (DFs), proposed and developed by K. Koebke and K. Smith. The offered concept covers both those of K. Koebke and K. Smith; both of them can be simulated within framework of new concept. Also, the offered concept covers Siemens KWU approach for baffle/reflector simulation, where the equivalent homogenized reflector XS are derived from the conservation of response matrix at the interface in 1D simi-infinite slab geometry. The IM and XS of new concept satisfy the same assumption about response matrix conservation in 1D semi-infinite slab geometry. It is expected that the new concept provides more accurate approximation of heterogeneous cell, especially in case of the steep flux gradients at the cell interfaces. The attractive shapes of new concept are: improved accuracy, simplicity of incorporation in the existing codes, equal numerical expenses in comparison to the K. Smith`s approach. The new concept is useful for: (a) explicit reflector/baffle simulation; (b) control blades simulation; (c) mixed UO{sub 2}/MOX core simulation. The offered model has been incorporated in the finite difference code and in the nodal code PANDOX. The numerical results show good accuracy of core calculations and insensitivity of homogenized parameters with respect to in-core conditions. 9 figs., 7 refs. (Author).

  4. Comparison of the various conditionings to base of whole-body irradiation, in malignant pediatric haematology: retrospective study of 702 patients from the register of the French Society of marrow transplant and cellular therapy; Comparaison des differents conditionnements a base d'irradiation corporelle totale, en hematologie pediatrique maligne: etude retrospective de 702 patients a partir du registre de la Societe francaise de greffe de moelle et therapie cellulaire

    Energy Technology Data Exchange (ETDEWEB)

    Maurin, C

    2006-10-15

    The aim of this work is to list the different conditioning used these last twenty years, in pediatrics for malignant hemopathy, then to evaluate the efficiency and the toxicity of these different conditioning by calculating and comparing the T.R.M. ( treatment related mortality), the D.F.S. (disease free survival) and the global survival. This work suggests a behavior liking homogeneous and adapted. In this study none of the 2 conditionings (T.A.M. or T.B.i.-E.D.X.) seems superior than we consider all the population of the malignant pediatric hemopathy or the only L.A.L.. The T.A.M. is more toxic but limits relapses. The global survival is similar. The adoption of homogeneous practices at the French level even European is a desirable objective. (N.C.)

  5. Homogenization of neutronic diffusion models

    International Nuclear Information System (INIS)

    Capdebosq, Y.

    1999-09-01

    In order to study and simulate nuclear reactor cores, one needs to access the neutron distribution in the core. In practice, the description of this density of neutrons is given by a system of diffusion equations, coupled by non differential exchange terms. The strong heterogeneity of the medium constitutes a major obstacle to the numerical computation of this models at reasonable cost. Homogenization appears as compulsory. Heuristic methods have been developed since the origin by nuclear physicists, under a periodicity assumption on the coefficients. They consist in doing a fine computation one a single periodicity cell, to solve the system on the whole domain with homogeneous coefficients, and to reconstruct the neutron density by multiplying the solutions of the two computations. The objectives of this work are to provide mathematically rigorous basis to this factorization method, to obtain the exact formulas of the homogenized coefficients, and to start on geometries where two periodical medium are placed side by side. The first result of this thesis concerns eigenvalue problem models which are used to characterize the state of criticality of the reactor, under a symmetry assumption on the coefficients. The convergence of the homogenization process is proved, and formulas of the homogenized coefficients are given. We then show that without symmetry assumptions, a drift phenomenon appears. It is characterized by the mean of a real Bloch wave method, which gives the homogenized limit in the general case. These results for the critical problem are then adapted to the evolution model. Finally, the homogenization of the critical problem in the case of two side by side periodic medium is studied on a one dimensional on equation model. (authors)

  6. 7 CFR 58.920 - Homogenization.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Homogenization. 58.920 Section 58.920 Agriculture... Procedures § 58.920 Homogenization. Where applicable concentrated products shall be homogenized for the... homogenization and the pressure at which homogenization is accomplished will be that which accomplishes the most...

  7. Testing homogeneity in Weibull-regression models.

    Science.gov (United States)

    Bolfarine, Heleno; Valença, Dione M

    2005-10-01

    In survival studies with families or geographical units it may be of interest testing whether such groups are homogeneous for given explanatory variables. In this paper we consider score type tests for group homogeneity based on a mixing model in which the group effect is modelled as a random variable. As opposed to hazard-based frailty models, this model presents survival times that conditioned on the random effect, has an accelerated failure time representation. The test statistics requires only estimation of the conventional regression model without the random effect and does not require specifying the distribution of the random effect. The tests are derived for a Weibull regression model and in the uncensored situation, a closed form is obtained for the test statistic. A simulation study is used for comparing the power of the tests. The proposed tests are applied to real data sets with censored data.

  8. Genetic Homogenization of Composite Materials

    Directory of Open Access Journals (Sweden)

    P. Tobola

    2009-04-01

    Full Text Available The paper is focused on numerical studies of electromagnetic properties of composite materials used for the construction of small airplanes. Discussions concentrate on the genetic homogenization of composite layers and composite layers with a slot. The homogenization is aimed to reduce CPU-time demands of EMC computational models of electrically large airplanes. First, a methodology of creating a 3-dimensional numerical model of a composite material in CST Microwave Studio is proposed focusing on a sufficient accuracy of the model. Second, a proper implementation of a genetic optimization in Matlab is discussed. Third, an association of the optimization script and a simplified 2-dimensional model of the homogeneous equivalent model in Comsol Multiphysics is proposed considering EMC issues. Results of computations are experimentally verified.

  9. Implementing Formative Assessment in Engineering Education: The Use of the Online Assessment System Etude

    Science.gov (United States)

    Dopper, Sofia M.; Sjoer, Ellen

    2004-01-01

    This article describes the possibilities offered by the online assessment system Etude to achieve the benefits of formative assessment. In order to find out the way this works in practice, we carried out an experiment with the use of Etude for formative assessment in the course on collaborative report writing. Results show that online formative…

  10. Spontaneous compactification to homogeneous spaces

    International Nuclear Information System (INIS)

    Mourao, J.M.

    1988-01-01

    The spontaneous compactification of extra dimensions to compact homogeneous spaces is studied. The methods developed within the framework of coset space dimensional reduction scheme and the most general form of invariant metrics are used to find solutions of spontaneous compactification equations

  11. Plasma electrolytic oxidation of A1050 aluminium alloy in homogeneous silicate-alkaline electrolytes with edta{sup 4−} complexes of Fe, Co, Ni, Cu, La and Ba under alternating polarization conditions

    Energy Technology Data Exchange (ETDEWEB)

    Rogov, A.B., E-mail: alex-lab@bk.ru [Nikolaev Institute of Inorganic Chemistry, 3, Acad. Lavrentiev Ave., Novosibirsk, 630090 (Russian Federation); Scientific and Technical Centre “Pokrytie-A” (OOO), 15, Dzerzhinskogo Ave., Novosibirsk, 630015 (Russian Federation)

    2015-11-01

    This work is devoted to the synthesis of coatings containing a number of transition elements by plasma electrolytic oxidation (PEO) on aluminium A1050 alloy. The paper discusses PEO coatings obtained in silicate-alkaline electrolytes containing complexes of Fe, Co, Ni, Cu, La and Ba with ethylenediaminetetraacetic anion edta{sup 4−}. It is also focused on the chemical basis of the electrolyte components choice and their role in the process of PEO. Possible mechanism of coating formation process is also discussed. Alternating current mode (symmetrical sinusoidal current pulses, initial average current density - 100 mA cm{sup −2}) was used to produce the coatings. The PEO process was characterized by behaviours of the anodic and cathodic peak voltage curves. Coating surfaces and cross sections are studied by optical dark field microscopy and scanning electron microscopy, X-ray and energy dispersive analysis. - Highlights: • Alkaline homogeneous electrolyte with transition metal-edta{sup 4-} complexes. • Coatings contain Fe, Co, Ni, Cu, La, Ba elements in alumina-silica matrix. • Alternating symmetric sinusoidal current of 100 mA cm{sup −2} was applied. • Borax buffer solution and silicate passivating agent were used.

  12. Contribution to the study of the stability of water-cooled reactors; Contribution a l'etude de la stabilite des reacteurs refroidis par de l'eau

    Energy Technology Data Exchange (ETDEWEB)

    Coudert, C [Commissariat a l' Energie Atomique, Cadarache (France). Centre d' Etudes Nucleaires

    1969-06-01

    This work is devoted to the study of the stability of reactors cooled by water subjected only to natural convection. It is made up of two parts, a theoretical study and experimental work, each of these parts being devoted to a consideration of linear and non-linear conditions: - calculation of the transfer function of the reactor using neutronic and hydrodynamic linear equations with the determination of the instability threshold; - demonstration of the existence of the limiting oscillation cycle in the case of a linear feedback using MALKIN'S method; - measurement and interpretation of the reactor's transfer functions and of the hydrodynamic transfer functions; and - analysis of the noise due to boiling. (author) [French] Dans ce travail on etudie la stabilite des piles refroidies par de l'eau circulant en convection naturelle. Cette etude se divise en deux parties: un travail theorique et un travail experimental, chacune de ces parties comportant une etude lineaire et une etude non-lineaire: - calcul de la fonction de transfert du reacteur a partir des equations lineaires de la neutronique et de l'hydrodynamique avec determination du seuil d'instabilite; - demonstration de l'existence du cycle limite des oscillations dans le cas d'une retroaction lineaire en utilisant la methode de MALKIN; - mesure et interpretation de la fonction de transfert du reacteur et des fonctions de transfert hydrodynamiques; et - analyse du bruit d'ebullition. (auteur)

  13. Electro-magnetostatic homogenization of bianisotropic metamaterials

    OpenAIRE

    Fietz, Chris

    2012-01-01

    We apply the method of asymptotic homogenization to metamaterials with microscopically bianisotropic inclusions to calculate a full set of constitutive parameters in the long wavelength limit. Two different implementations of electromagnetic asymptotic homogenization are presented. We test the homogenization procedure on two different metamaterial examples. Finally, the analytical solution for long wavelength homogenization of a one dimensional metamaterial with microscopically bi-isotropic i...

  14. Contribution to the study of diffusion in poly-phase system; Contribution a l'etude de la diffusion en systeme polyphase

    Energy Technology Data Exchange (ETDEWEB)

    Adda, Y; Philibert, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires; Institut de Recherches de la Siderurgie Francaise (IRSID), 78 - Saint-Germain-en-Laye (France)

    1959-07-01

    After chemical diffusion between two metals, at temperatures where, according to the equilibrium diagram, several phases exist, parallel bands corresponding to these various phases can be seen in a section which is perpendicular to the diffusion front. It is known that in this case there are discontinuities in the concentration-penetration curve, corresponding to the interfaces. The concentrations at the point where the discontinuities occur give the limits of solubility in each of the present phases. During our experiments on the system uranium-zirconium, we verified that these concentrations do not vary with the diffusion time and therefore that the conditions of thermodynamical equilibrium are obeyed. It follows that an interesting method is available for determining the equilibrium diagram for the solid state. We have applied this method to the U-Zr system. Kinetic studies of poly-phase diffusion are as yet relatively scarce as a result of difficulty of experimentation. Various methods based on purely micro-graphical studies (measurement of the thickness of intermediate phases) are also proposed for evaluating the coefficient of diffusion. Our experimental results show that the hypotheses on which these methods are based are rarely valid. We have established concentration-penetration curves for the systems U-Zr (between 590 deg. C and 950 deg. C) and U-Mo (between 800 deg. C and 1050 deg. C). These curves have very often a very accentuated curvature, thus indicating variations in the diffusion coefficient, which cannot be expressed by simple relationships. Finally, we have observed certain anomalies in the neighbourhood of the interfaces between adjacent phases. Further we have studied the Kirkendall effect in poly-phase system by marking the plane of welding with tungsten wires, and compared these results to those from a previous study in the homogeneous phase. We have found that the presence of phase boundaries accentuates this effect. The interpretation of

  15. Contribution to the study of diffusion in poly-phase system; Contribution a l'etude de la diffusion en systeme polyphase

    Energy Technology Data Exchange (ETDEWEB)

    Adda, Y.; Philibert, J. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires; Institut de Recherches de la Siderurgie Francaise (IRSID), 78 - Saint-Germain-en-Laye (France)

    1959-07-01

    After chemical diffusion between two metals, at temperatures where, according to the equilibrium diagram, several phases exist, parallel bands corresponding to these various phases can be seen in a section which is perpendicular to the diffusion front. It is known that in this case there are discontinuities in the concentration-penetration curve, corresponding to the interfaces. The concentrations at the point where the discontinuities occur give the limits of solubility in each of the present phases. During our experiments on the system uranium-zirconium, we verified that these concentrations do not vary with the diffusion time and therefore that the conditions of thermodynamical equilibrium are obeyed. It follows that an interesting method is available for determining the equilibrium diagram for the solid state. We have applied this method to the U-Zr system. Kinetic studies of poly-phase diffusion are as yet relatively scarce as a result of difficulty of experimentation. Various methods based on purely micro-graphical studies (measurement of the thickness of intermediate phases) are also proposed for evaluating the coefficient of diffusion. Our experimental results show that the hypotheses on which these methods are based are rarely valid. We have established concentration-penetration curves for the systems U-Zr (between 590 deg. C and 950 deg. C) and U-Mo (between 800 deg. C and 1050 deg. C). These curves have very often a very accentuated curvature, thus indicating variations in the diffusion coefficient, which cannot be expressed by simple relationships. Finally, we have observed certain anomalies in the neighbourhood of the interfaces between adjacent phases. Further we have studied the Kirkendall effect in poly-phase system by marking the plane of welding with tungsten wires, and compared these results to those from a previous study in the homogeneous phase. We have found that the presence of phase boundaries accentuates this effect. The interpretation of

  16. Homogenization models for thin rigid structured surfaces and films.

    Science.gov (United States)

    Marigo, Jean-Jacques; Maurel, Agnès

    2016-07-01

    A homogenization method for thin microstructured surfaces and films is presented. In both cases, sound hard materials are considered, associated with Neumann boundary conditions and the wave equation in the time domain is examined. For a structured surface, a boundary condition is obtained on an equivalent flat wall, which links the acoustic velocity to its normal and tangential derivatives (of the Myers type). For a structured film, jump conditions are obtained for the acoustic pressure and the normal velocity across an equivalent interface (of the Ventcels type). This interface homogenization is based on a matched asymptotic expansion technique, and differs slightly from the classical homogenization, which is known to fail for small structuration thicknesses. In order to get insight into what causes this failure, a two-step homogenization is proposed, mixing classical homogenization and matched asymptotic expansion. Results of the two homogenizations are analyzed in light of the associated elementary problems, which correspond to problems of fluid mechanics, namely, potential flows around rigid obstacles.

  17. 98 Etude Comparative du Systeme Phonematique et Tonal des ...

    African Journals Online (AJOL)

    98. Etude Comparative du Systeme Phonematique et Tonal des. Deux Parlers: Le Yoruba du Nigeria et L'itsa Parle en. Republique du Benin. Ajani Akinwumi Lateef et Ayuba G. Ajibabi http://dx.doi./org/10.4314/ujah.v18i3.5. Résume. En ce début de l'époque ou la mondialisation et la coexistence des peuples dans le ...

  18. Conclusions about homogeneity and devitrification

    International Nuclear Information System (INIS)

    Larche, F.

    1997-01-01

    A lot of experimental data concerning homogeneity and devitrification of R7T7 glass have been published. It appears that: - the crystallization process is very limited, - the interfaces due to bubbles and the container wall favor crystallization locally but the ratio of crystallized volume remains always below a few per cents, and - crystallization has no damaging long-term effects as far as leaching tests can be trusted. (A.C.)

  19. Is charity a homogeneous good?

    OpenAIRE

    Backus, Peter

    2010-01-01

    In this paper I estimate income and price elasticities of donations to six different charitable causes to test the assumption that charity is a homogeneous good. In the US, charitable donations can be deducted from taxable income. This has long been recognized as producing a price, or taxprice, of giving equal to one minus the marginal tax rate faced by the donor. A substantial portion of the economic literature on giving has focused on estimating price and income elasticities of giving as th...

  20. Note on integrability of certain homogeneous Hamiltonian systems

    Energy Technology Data Exchange (ETDEWEB)

    Szumiński, Wojciech [Institute of Physics, University of Zielona Góra, Licealna 9, PL-65-407, Zielona Góra (Poland); Maciejewski, Andrzej J. [Institute of Astronomy, University of Zielona Góra, Licealna 9, PL-65-407, Zielona Góra (Poland); Przybylska, Maria, E-mail: M.Przybylska@if.uz.zgora.pl [Institute of Physics, University of Zielona Góra, Licealna 9, PL-65-407, Zielona Góra (Poland)

    2015-12-04

    In this paper we investigate a class of natural Hamiltonian systems with two degrees of freedom. The kinetic energy depends on coordinates but the system is homogeneous. Thanks to this property it admits, in a general case, a particular solution. Using this solution we derive necessary conditions for the integrability of such systems investigating differential Galois group of variational equations. - Highlights: • Necessary integrability conditions for some 2D homogeneous Hamilton systems are given. • Conditions are obtained analysing differential Galois group of variational equations. • New integrable and superintegrable systems are identified.

  1. Nuclear study of Melusine; Etude nucleaire de Melusine

    Energy Technology Data Exchange (ETDEWEB)

    Cherot, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    In this report are reviewed - with respect to starting of experiments - the main nuclear characteristics of a 20 per cent enriched uranium lattice, with light water as moderator and reflector. The reactor is to operate at 1 MW. 1) Study of various critical masses. 2) Control. Effectiveness of cadmium. Control rods and of a stainless steel regulating rod. 3) Study of the effect on reactivity of disturbances in the core center. 4) Study of xenon and samarium poisoning. 5) Temperature factor. 6) Heat exchanges in a fuel element. (author) [French] On etudie, dans ce rapport, les principales proprietes nucleaires d'un reseau a uranium enrichi (20 pour cent), dont le moderateur et le reflecteur sont l'eau legere en vue des experiences de demarrage. Ce reacteur devra fonctionner a 1 MW. 1) Etude de diverses masses critiques. 2) Controle. Efficacite des barres de controle en cadmium et d'une barre de reglage en acier inoxydable. 3) Etude de l'effet sur la reactivite de perturbation au centre du coeur. 4) Etude de l'empoisonnement xenon et samarium. 5) Coefficient de temperature. 6) Echanges thermiques dans un element. (auteur)

  2. Peripheral nerve magnetic stimulation: influence of tissue non-homogeneity

    Directory of Open Access Journals (Sweden)

    Papazov Sava P

    2003-12-01

    Full Text Available Abstract Background Peripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc. Time-varying magnetic field stimulation of the median and ulnar nerves in the carpal region is studied, with special consideration of the influence of non-homogeneities. Methods A detailed three-dimensional finite element model (FEM of the anatomy of the wrist region was built to assess the induced currents distribution by external magnetic stimulation. The electromagnetic field distribution in the non-homogeneous domain was defined as an internal Dirichlet problem using the finite element method. The boundary conditions were obtained by analysis of the vector potential field excited by external current-driven coils. Results The results include evaluation and graphical representation of the induced current field distribution at various stimulation coil positions. Comparative study for the real non-homogeneous structure with anisotropic conductivities of the tissues and a mock homogeneous media is also presented. The possibility of achieving selective stimulation of either of the two nerves is assessed. Conclusion The model developed could be useful in theoretical prediction of the current distribution in the nerves during diagnostic stimulation and therapeutic procedures involving electromagnetic excitation. The errors in applying homogeneous domain modeling rather than real non-homogeneous biological structures are demonstrated. The practical implications of the applied approach are valid for any arbitrary weakly conductive medium.

  3. At-tank Low-Activity Feed Homogeneity Analysis Verification

    International Nuclear Information System (INIS)

    DOUGLAS, J.G.

    2000-01-01

    This report evaluates the merit of selecting sodium, aluminum, and cesium-137 as analytes to indicate homogeneity of soluble species in low-activity waste (LAW) feed and recommends possible analytes and physical properties that could serve as rapid screening indicators for LAW feed homogeneity. The three analytes are adequate as screening indicators of soluble species homogeneity for tank waste when a mixing pump is used to thoroughly mix the waste in the waste feed staging tank and when all dissolved species are present at concentrations well below their solubility limits. If either of these conditions is violated, then the three indicators may not be sufficiently chemically representative of other waste constituents to reliably indicate homogeneity in the feed supernatant. Additional homogeneity indicators that should be considered are anions such as fluoride, sulfate, and phosphate, total organic carbon/total inorganic carbon, and total alpha to estimate the transuranic species. Physical property measurements such as gamma profiling, conductivity, specific gravity, and total suspended solids are recommended as possible at-tank methods for indicating homogeneity. Indicators of LAW feed homogeneity are needed to reduce the U.S. Department of Energy, Office of River Protection (ORP) Program's contractual risk by assuring that the waste feed is within the contractual composition and can be supplied to the waste treatment plant within the schedule requirements

  4. Homogeneity Study of UO2 Pellet Density for Quality Control

    International Nuclear Information System (INIS)

    Moon, Je Seon; Park, Chang Je; Kang, Kwon Ho; Moon, Heung Soo; Song, Kee Chan

    2005-01-01

    A homogeneity study has been performed with various densities of UO 2 pellets as the work of a quality control. The densities of the UO 2 pellets are distributed randomly due to several factors such as the milling conditions and sintering environments, etc. After sintering, total fourteen bottles were chosen for UO 2 density and each bottle had three samples. With these bottles, the between-bottle and within-bottle homogeneity were investigated via the analysis of the variance (ANOVA). From the results of ANOVA, the calculated F-value is used to determine whether the distribution is accepted or rejected from the view of a homogeneity under a certain confidence level. All the homogeneity checks followed the International Standard Guide 35

  5. Garde a l'enfance: Etude sur la remuneration et les conditions de travail dans le domaine de la garde a l'enfance au Canada. Rapport final (Caring for a Living: A Study on Wages and Working Conditions in Canadian Child Care. Final Report).

    Science.gov (United States)

    Canadian Child Care Federation, Ottawa (Ontario).

    Between November 1990 and August 1992, a study examined wages and working conditions of child care staff in both licensed group centers and family day care homes in Canada. Three instruments were developed for the study, a short telephone interview for center directors, a follow-up director's questionnaire, and a staff questionnaire. The study…

  6. Physical applications of homogeneous balls

    CERN Document Server

    Scarr, Tzvi

    2005-01-01

    One of the mathematical challenges of modern physics lies in the development of new tools to efficiently describe different branches of physics within one mathematical framework. This text introduces precisely such a broad mathematical model, one that gives a clear geometric expression of the symmetry of physical laws and is entirely determined by that symmetry. The first three chapters discuss the occurrence of bounded symmetric domains (BSDs) or homogeneous balls and their algebraic structure in physics. The book further provides a discussion of how to obtain a triple algebraic structure ass

  7. Heterotic strings on homogeneous spaces

    International Nuclear Information System (INIS)

    Israel, D.; Kounnas, C.; Orlando, D.; Petropoulos, P.M.

    2005-01-01

    We construct heterotic string backgrounds corresponding to families of homogeneous spaces as exact conformal field theories. They contain left cosets of compact groups by their maximal tori supported by NS-NS 2-forms and gauge field fluxes. We give the general formalism and modular-invariant partition functions, then we consider some examples such as SU(2)/U(1)∝S 2 (already described in a previous paper) and the SU(3)/U(1) 2 flag space. As an application we construct new supersymmetric string vacua with magnetic fluxes and a linear dilaton. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  8. Contribution to the study of influence of hydrodynamic conditions on the combustion of a preliminary mixture in a enclosed medium; Contribution a l`etude de l`influence des conditions hydrodynamiques sur la combustion d`un melange prealable dans un milieu confine

    Energy Technology Data Exchange (ETDEWEB)

    Henry, J.D.

    1996-02-01

    This thesis is a study on the internal combustion of a pistons engine. the first chapter is devoted to the description of the experimental device and measurement means. The combustion chamber is described with its adaptation to new experimental conditions. The second chapter concerns the diagnosis means to interpret the hydrodynamic conditions by the cross checking of displays with the measures of flow speed by laser velocimetry. The third chapter gives the result of analysis on the process of the birth of a turbulent flow in a whirl movement. The study of the electric spark and the initial phase of the combustion, in media with or without movement, is in the last chapter. (N.C.)

  9. Homogenization scheme for acoustic metamaterials

    KAUST Repository

    Yang, Min

    2014-02-26

    We present a homogenization scheme for acoustic metamaterials that is based on reproducing the lowest orders of scattering amplitudes from a finite volume of metamaterials. This approach is noted to differ significantly from that of coherent potential approximation, which is based on adjusting the effective-medium parameters to minimize scatterings in the long-wavelength limit. With the aid of metamaterials’ eigenstates, the effective parameters, such as mass density and elastic modulus can be obtained by matching the surface responses of a metamaterial\\'s structural unit cell with a piece of homogenized material. From the Green\\'s theorem applied to the exterior domain problem, matching the surface responses is noted to be the same as reproducing the scattering amplitudes. We verify our scheme by applying it to three different examples: a layered lattice, a two-dimensional hexagonal lattice, and a decorated-membrane system. It is shown that the predicted characteristics and wave fields agree almost exactly with numerical simulations and experiments and the scheme\\'s validity is constrained by the number of dominant surface multipoles instead of the usual long-wavelength assumption. In particular, the validity extends to the full band in one dimension and to regimes near the boundaries of the Brillouin zone in two dimensions.

  10. ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.

    Energy Technology Data Exchange (ETDEWEB)

    BULLOCK,R.M.; BENDER,B.R.

    2000-12-01

    The use of isotope labels has had a fundamentally important role in the determination of mechanisms of homogeneously catalyzed reactions. Mechanistic data is valuable since it can assist in the design and rational improvement of homogeneous catalysts. There are several ways to use isotopes in mechanistic chemistry. Isotopes can be introduced into controlled experiments and followed where they go or don't go; in this way, Libby, Calvin, Taube and others used isotopes to elucidate mechanistic pathways for very different, yet important chemistries. Another important isotope method is the study of kinetic isotope effects (KIEs) and equilibrium isotope effect (EIEs). Here the mere observation of where a label winds up is no longer enough - what matters is how much slower (or faster) a labeled molecule reacts than the unlabeled material. The most careti studies essentially involve the measurement of isotope fractionation between a reference ground state and the transition state. Thus kinetic isotope effects provide unique data unavailable from other methods, since information about the transition state of a reaction is obtained. Because getting an experimental glimpse of transition states is really tantamount to understanding catalysis, kinetic isotope effects are very powerful.

  11. Topology of actions and homogeneous spaces

    International Nuclear Information System (INIS)

    Kozlov, Konstantin L

    2013-01-01

    Topologization of a group of homeomorphisms and its action provide additional possibilities for studying the topological space, the group of homeomorphisms, and their interconnections. The subject of the paper is the use of the property of d-openness of an action (introduced by Ancel under the name of weak micro-transitivity) in the study of spaces with various forms of homogeneity. It is proved that a d-open action of a Čech-complete group is open. A characterization of Polish SLH spaces using d-openness is given, and it is established that any separable metrizable SLH space has an SLH completion that is a Polish space. Furthermore, the completion is realized in coordination with the completion of the acting group with respect to the two-sided uniformity. A sufficient condition is given for extension of a d-open action to the completion of the space with respect to the maximal equiuniformity with preservation of d-openness. A result of van Mill is generalized, namely, it is proved that any homogeneous CDH metrizable compactum is the only G-compactification of the space of rational numbers for the action of some Polish group. Bibliography: 39 titles.

  12. TWO FERROMAGNETIC SPHERES IN HOMOGENEOUS MAGNETIC FIELD

    Directory of Open Access Journals (Sweden)

    Yury A. Krasnitsky

    2018-01-01

    Full Text Available The problem of two spherical conductors is studied quite in detail with bispherical coordinates usage and has numerous appendices in an electrostatics. The boundary-value problem about two ferromagnetic spheres enclosed on homogeneous and infinite environment in which the lack of spheres exists like homogeneous magnetic field is considered. The solution of Laplace's equation in the bispherical system of coordinates allows us to find the potential and field distribution in all spaces, including area between spheres. The boundary conditions in potential continuity and in ordinary density constituent of spheres surfaces induction flux are used. It is supposed that spheres are identical, and magnetic permeability of their material is expressed in  >> 0. The problem about falling of electromagnetic plane wave on the system of two spheres, which possesses electrically small sizes, can be considered as quasistationary. The scalar potentials received as a result of Laplace's equation solution are represented by the series containing Legendre polynomials. The concept of two spheres system effective permeability is introduced. It is equal to the advantage in magnitude of magnetic induction flux vector through a certain system’s section arising due to its magnetic properties. Necessary ratios for the effective permeability referred to the central system’s section are obtained. Particularly, the results can be used during the analysis of ferroxcube core clearance, which influences on the magnetic antenna properties. 

  13. Cosmic Ray Hit Detection with Homogenous Structures

    Science.gov (United States)

    Smirnov, O. M.

    Cosmic ray (CR) hits can affect a significant number of pixels both on long-exposure ground-based CCD observations and on the Space Telescope frames. Thus, methods of identifying the damaged pixels are an important part of the data preprocessing for practically any application. The paper presents an implementation of a CR hit detection algorithm based on a homogenous structure (also called cellular automata ), a concept originating in artificial intelligence and dicrete mathematics. Each pixel of the image is represented by a small automaton, which interacts with its neighbors and assumes a distinct state if it ``decides'' that a CR hit is present. On test data, the algorithm has shown a high detection rate (~0.7 ) and a low false alarm rate (frame. A homogenous structure is extremely trainable, which can be very important for processing large batches of data obtained under similar conditions. Training and optimizing issues are discussed, as well as possible other applications of this concept to image processing.

  14. Photo-electret effects in homogenous semiconductors

    International Nuclear Information System (INIS)

    Nabiev, G.A.

    2004-01-01

    In the given work is shown the opportunity and created the theory of photo-electret condition in semiconductors with Dember mechanism of photo-voltage generation. Photo-electret of such type can be created, instead of traditional and without an external field as a result of only one illumination. Polar factor, in this case, is the distinction of electrons and holes mobility. Considered the multilayered structure with homogeneous photoactive micro areas shared by the layers, which are interfering to alignment of carriers concentration. We consider, that the homogeneous photoactive areas contain deep levels of stick. Because of addition of elementary photo voltage in separate micro photo cells it is formed the abnormal-large photo voltage (APV-effect). Let's notice, that Dember photo-voltage in a separate micro photo-cell ≤kT/q. From the received expressions, in practically important, special case, when quasi- balance between valent zone and stick levels established in much more smaller time, than free hole lifetime, and we received, that photo-voltage is relaxing. Comparing of the received expressions with the laws of photo voltage attenuation in p-n- junction structures shows their identity; the difference is only in absolute meanings of photo voltage. During the illumination in the semiconductor are created the superfluous concentration of charge carriers and part from them stays at deep levels. At de-energizing light there is a gradual generation of carriers located at these levels

  15. Improving homogeneity by dynamic speed limit systems.

    NARCIS (Netherlands)

    Nes, N. van Brandenberg, S. & Twisk, D.A.M.

    2010-01-01

    Homogeneity of driving speeds is an important variable in determining road safety; more homogeneous driving speeds increase road safety. This study investigates the effect of introducing dynamic speed limit systems on homogeneity of driving speeds. A total of 46 subjects twice drove a route along 12

  16. 7 CFR 58.636 - Homogenization.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Homogenization. 58.636 Section 58.636 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.636 Homogenization. Homogenization of the pasteurized mix shall be accomplished to...

  17. The homogeneous geometries of real hyperbolic space

    DEFF Research Database (Denmark)

    Castrillón López, Marco; Gadea, Pedro Martínez; Swann, Andrew Francis

    We describe the holonomy algebras of all canonical connections of homogeneous structures on real hyperbolic spaces in all dimensions. The structural results obtained then lead to a determination of the types, in the sense of Tricerri and Vanhecke, of the corresponding homogeneous tensors. We use...... our analysis to show that the moduli space of homogeneous structures on real hyperbolic space has two connected components....

  18. Orthogonality Measurement for Homogenous Projects-Bases

    Science.gov (United States)

    Ivan, Ion; Sandu, Andrei; Popa, Marius

    2009-01-01

    The homogenous projects-base concept is defined. Next, the necessary steps to create a homogenous projects-base are presented. A metric system is built, which then will be used for analyzing projects. The indicators which are meaningful for analyzing a homogenous projects-base are selected. The given hypothesis is experimentally verified. The…

  19. The evaporative vector: Homogeneous systems

    International Nuclear Information System (INIS)

    Klots, C.E.

    1987-05-01

    Molecular beams of van der Waals molecules are the subject of much current research. Among the methods used to form these beams, three-sputtering, laser ablation, and the sonic nozzle expansion of neat gases - yield what are now recognized to be ''warm clusters.'' They contain enough internal energy to undergo a number of first-order processes, in particular that of evaporation. Because of this evaporation and its attendant cooling, the properties of such clusters are time-dependent. The states of matter which can be arrived at via an evaporative vector on a typical laboratory time-scale are discussed. Topics include the (1) temperatures, (2) metastability, (3) phase transitions, (4) kinetic energies of fragmentation, and (5) the expression of magical properties, all for evaporating homogeneous clusters

  20. Study of the action of a phosphonate additive on steel scale deposit and corrosion in the hydrodynamic conditions of a channel flow cell; Etude de l'action d'un additif phosphone sur l'entartrage et sur la corrosion de l'acier dans les conditions hydrodynamiques d'une cellule a canal

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, C.

    2000-10-17

    In cooling systems, an improved control of scale deposit and corrosion processes is a major challenge and an realistic evaluation tool for water treatments is of the utmost economic importance. In this study, a channel flow cell was used to allow in-situ electrochemical measurements in well defined electrolyte tube flowing conditions. An expression of the mass transfer towards the electrode was established where the diffusion-limited current is a function of Re{sup 1/3} in the laminar regime and was verified experimentally using the redox couples Fe[CN]{sub 6}{sup 4-}/ Fe[CN]{sub 6}{sup 3-} and O{sub 2}/OH{sup -}. This hydrodynamically controlled experimental device was developed to investigate scale deposit processes and to evaluate scale inhibitor efficiency using a electrochemical quartz crystal microbalance. Experiments were performed on three different waters, at various flow rates and temperatures. The efficiency of a well known phosphonate (HEDP) was tested at different concentrations and an optimum concentration could be established (0.7 mg dm{sup -3}). The effect of additive injection during the scale formation as well as the influence of flow rate on the inhibiting efficiency were evaluated. The anti-scale additive was shown to be more effective in the turbulent regime. HEDP has shown a strong effect on inhibiting crystal growth and that affected the morphology of CaCO{sub 3} crystals. The HEDP effect on protecting carbon steel against corrosion was also studied in mineral water containing Ca{sup 2+} ions. It was found that anti-corrosion effect of HEDP is enhanced by the presence of calcium in solution and that is due to the formation of an HEDP-Ca{sup 2+} complex, which adsorbs onto the metallic surface and protects it from dissolution. (author)

  1. Notes on a class of homogeneous space-times

    International Nuclear Information System (INIS)

    Calvao, M.O.; Reboucas, M.J.; Teixeira, A.F.F.; Silva Junior, W.M.

    1987-01-01

    The breakdown of causality in homogeneous Goedel-type space-time manifolds is examined. An extension of Reboucas-Tiomno (RT) study is made. The existence of noncausal curves is also investigated under two different conditions on the energy-momentum tensor. An integral representation of the infinitesimal generators of isometries is obtained extending previous works on the RT geometry. (Author) [pt

  2. A characterization of Markovian homogeneous multicomponent Gaussian fields

    International Nuclear Information System (INIS)

    Ekhaguere, G.O.S.

    1980-01-01

    Necessary and sufficient conditions are given for a certain class of homogeneous multicomponent Gaussian generalized stochastic fields to possess a Markov property equivalent to Nelson's. The class of Markov fields so characterized has a as a cubclass the class of Markov fields which lead by Nelson's Reconstruction Theorem to some covariant (free) quantum fields. (orig.)

  3. Impact Assessment Study on the Living Conditions of Women and Children, Haïti Etude de l’impact d'une catastrophe sur les conditions de vie des femmes et des enfants, Haïtï Evaluación del impacto en las condiciones de vida de mujeres y niños, Haití

    Directory of Open Access Journals (Sweden)

    Gregory Bulit

    2012-06-01

    Full Text Available In response to the earthquake that hit Haiti on 12 January 2010, Solidarités International (SI provided urgent basic services of Water, Sanitation and Hygiene in over 52 Internally Displaced Peoples (IDP Sites, and played a vital role in preventing the spread of the cholera outbreak in October of that same year and improving medical care for people affected by the epidemic and to reduce risks of further propagation. Solidarités International’s engagement has been further expanded to other programs, including assistance for the return of displaced communities to their original neighborhoods. The daily living conditions and responsibilities of women subject many of them and their children to risks during various phases of a disaster. Women and children are most at risk and suffer the greatest in disaster situations. The present article discusses the impacts of the disaster on women and children, and the impact of SI’s programs. It also aims to identify some of the response gaps and mistakes attributed to SI and other humanitarian actors due to the lack of gender sensitive approach.Suite au séisme qui a frappé Haiti le 12 janvier 2010, Solidarités International (SI a mis en place des services d'urgence de base en matière d'eau, d'assainissement et d'hygiène dans plus de 52 sites de déplacés. L’association d’aide humanitaire a également joué un rôle primordial dans la prévention du choléra en octobre 2010 et dans l’amélioration des soins médicaux prodigués aux personnes touchées par l’épidémie, réduisant les risques de propagation de la maladie. Solidarités International a aussi lancé de nombreuses autres initiatives, notamment l’aide au retour des populations déplacées dans leurs quartiers d’origine. Les conditions de vie quotidiennes et les responsabilités des femmes exposent bon nombre d’entre elles et leurs enfants à divers risques au cours des différentes phases d’une catastrophe, les femmes et

  4. Theoretical studies of homogeneous catalysts mimicking nitrogenase.

    Science.gov (United States)

    Sgrignani, Jacopo; Franco, Duvan; Magistrato, Alessandra

    2011-01-10

    The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen 'fixation' via an iron molybdenum cofactor (FeMo-co) under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N₂ to various degrees. However, to date Mo(N₂)(HIPTN)₃N with (HIPTN)₃N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N₂. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.

  5. Theoretical Studies of Homogeneous Catalysts Mimicking Nitrogenase

    Directory of Open Access Journals (Sweden)

    Alessandra Magistrato

    2011-01-01

    Full Text Available The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen ‘fixation’ via an iron molybdenum cofactor (FeMo-co under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N2 to various degrees. However, to date Mo(N2(HIPTN3N with (HIPTN3N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N2. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.

  6. Use of hydraulic and aerial mock up to study atmospheric pollution; L'utilisation des maquettes aeriennes et hydrauliques pour l'etude de la pollution atmospherique

    Energy Technology Data Exchange (ETDEWEB)

    Facy, L; Perrin De Brichambaut, C; Doury, A; Le Quinio, R

    1962-07-01

    Fundamental studies on turbulent atmospheric diffusion of finely divided particles, cannot remain on a purely theoretical basis. Further experimental studies must be considered. - In full scale, from accidental and induced releases. - On a reduced scale, in aerodynamic wind tunnels or hydraulic water tunnels. A first set of studies on reduced scale models has been worked out according to a contract between French 'Meteorologie Nationale' and French 'Commissariat a l'Energie Atomique' and with the Collaboration of Saint-Cyr 'Institut Aerotechnique'. Essentially two kinds of results have been obtained: - The mathematical model of SUTTON for the turbulent diffusion in the atmosphere, deduced from the SUTTON theory, generally used by us, has been correctly verified, qualitatively and quantitatively whenever experiments were consistent with the theory conditions. - The quantitative assays of photographic and cinematographic visualization have given precise details on the phenomena inaccessible to calculations, due to the influence of obstacles and release conditions. - Generally, it can be asserted, that the atmospheric pollution studies are worked out by mock up experimentations and that, in some cases these experiments never can be replaced by mathematically pure models. (authors) [French] Les etudes fondamentales portant sur la diffusion turbulente dans l'atmosphere de quantites de matieres finement divisees, ne peuvent se maintenir sur un plan exclusivement theorique. C'est pourquoi des etudes experimentales complementaires doivent etre obligatoirement envisagees: - en vraie grandeur, a partir d'emissions accidentelles ou provoquees; - sur modeles reduits, en soufflerie aerodynamique ou en veine hydraulique. En ce qui concerne les modeles reduits, une premiere serie d'etudes a pu etre menee a bien, dans le cadre d'un contrat passe entre la Meteorologie Nationale et le Commissariat a l'Energie Atomique, et avec la collaboration de l'Institut Aerotechnique de Saint

  7. Study of the dynamic behaviour of the reactor Rapsodie; Etude du comportement dynamique de la pile rapsodie

    Energy Technology Data Exchange (ETDEWEB)

    Abdon, R; Chaigne, M [Commissariat a l' Energie Atomique, Cadarache (France). Centre d' Etudes Nucleaires

    1964-07-01

    . The investigation of the control, carried out on analog computer, served to determine the different possible means of starting and changing the conditions of the reactor as well as its automatic control. The calculations were examined in the totality by the construction of a training simulator composed of a board similar to the control board of the reactor, all of whose commands (reactivity and flows) work on an analogue computer which resolves in the real time the dynamic equations of the reactor and which reproduces simultaneously all the parameters representing the state of the installation (power, period, temperatures, etc. ) in the case of various incidents as well as under normal conditions of functioning. (authors) [French] On sait que le developpement des reacteurs surgenerateurs a neutrons rapides pose des problemes nouveaux d'une part dans les domaines mecanique et thermique et d'autre part en ce qui concerne leur comportement dynamique et leur surete. La pile RAPSODIE a ete l'objet de tres nombreuses etudes dynamiques effectuees sur machines analogiques et digitales, pour deux versions du combustible (metal et oxyde). Apres elaboration des modeles mathematiques representatifs de l'ensemble de l'installation (bloc pile et circuit de refroidissement) tant du point de vue neutronique que du point de vue thermodynamique, on a mis au point les schemas analogiques et les codes digitaux utilisables pour mener a bien les simulations d'incidents, de conduite et de stabilite du reacteur. On s'est attache, par rapport aux methodes habituelles a obtenir une precision plus grande, par un decoupage en zones plus fines, par l'emploi de formulations plus representatives du systeme reel, voire solubles analytiquement. Les etudes d'incidents ont ete effectuees par voie analogique pour l'ensemble de l'installation et par voie digitale pour l'etude du bloc pile seul ou de l'installation fonctionnant avec un seul circuit thermique. Un programme complementaire special - qui, a

  8. Reciprocity theory of homogeneous reactions

    Science.gov (United States)

    Agbormbai, Adolf A.

    1990-03-01

    The reciprocity formalism is applied to the homogeneous gaseous reactions in which the structure of the participating molecules changes upon collision with one another, resulting in a change in the composition of the gas. The approach is applied to various classes of dissociation, recombination, rearrangement, ionizing, and photochemical reactions. It is shown that for the principle of reciprocity to be satisfied it is necessary that all chemical reactions exist in complementary pairs which consist of the forward and backward reactions. The backward reaction may be described by either the reverse or inverse process. The forward and backward processes must satisfy the same reciprocity equation. Because the number of dynamical variables is usually unbalanced on both sides of a chemical equation, it is necessary that this balance be established by including as many of the dynamical variables as needed before the reciprocity equation can be formulated. Statistical transformation models of the reactions are formulated. The models are classified under the titles free exchange, restricted exchange and simplified restricted exchange. The special equations for the forward and backward processes are obtained. The models are consistent with the H theorem and Le Chatelier's principle. The models are also formulated in the context of the direct simulation Monte Carlo method.

  9. Moral Beliefs and Cognitive Homogeneity

    Directory of Open Access Journals (Sweden)

    Nevia Dolcini

    2018-04-01

    Full Text Available The Emotional Perception Model of moral judgment intends to account for experientialism about morality and moral reasoning. In explaining how moral beliefs are formed and applied in practical reasoning, the model attempts to overcome the mismatch between reason and action/desire: morality isn’t about reason for actions, yet moral beliefs, if caused by desires, may play a motivational role in (moral agency. The account allows for two kinds of moral beliefs: genuine moral beliefs, which enjoy a relation to desire, and motivationally inert moral beliefs acquired in ways other than experience. Such etiology-based dichotomy of concepts, I will argue, leads to the undesirable view of cognition as a non-homogeneous phenomenon. Moreover, the distinction between moral beliefs and moral beliefs would entail a further dichotomy encompassing the domain of moral agency: one and the same action might possibly be either genuine moral, or not moral, if acted by individuals lacking the capacity for moral feelings, such as psychopaths.

  10. Homogeneous modes of cosmological instantons

    Energy Technology Data Exchange (ETDEWEB)

    Gratton, Steven; Turok, Neil

    2001-06-15

    We discuss the O(4) invariant perturbation modes of cosmological instantons. These modes are spatially homogeneous in Lorentzian spacetime and thus not relevant to density perturbations. But their properties are important in establishing the meaning of the Euclidean path integral. If negative modes are present, the Euclidean path integral is not well defined, but may nevertheless be useful in an approximate description of the decay of an unstable state. When gravitational dynamics is included, counting negative modes requires a careful treatment of the conformal factor problem. We demonstrate that for an appropriate choice of coordinate on phase space, the second order Euclidean action is bounded below for normalized perturbations and has a finite number of negative modes. We prove that there is a negative mode for many gravitational instantons of the Hawking-Moss or Coleman{endash}De Luccia type, and discuss the associated spectral flow. We also investigate Hawking-Turok constrained instantons, which occur in a generic inflationary model. Implementing the regularization and constraint proposed by Kirklin, Turok and Wiseman, we find that those instantons leading to substantial inflation do not possess negative modes. Using an alternate regularization and constraint motivated by reduction from five dimensions, we find a negative mode is present. These investigations shed new light on the suitability of Euclidean quantum gravity as a potential description of our universe.

  11. Homogeneous modes of cosmological instantons

    International Nuclear Information System (INIS)

    Gratton, Steven; Turok, Neil

    2001-01-01

    We discuss the O(4) invariant perturbation modes of cosmological instantons. These modes are spatially homogeneous in Lorentzian spacetime and thus not relevant to density perturbations. But their properties are important in establishing the meaning of the Euclidean path integral. If negative modes are present, the Euclidean path integral is not well defined, but may nevertheless be useful in an approximate description of the decay of an unstable state. When gravitational dynamics is included, counting negative modes requires a careful treatment of the conformal factor problem. We demonstrate that for an appropriate choice of coordinate on phase space, the second order Euclidean action is bounded below for normalized perturbations and has a finite number of negative modes. We prove that there is a negative mode for many gravitational instantons of the Hawking-Moss or ColemanendashDe Luccia type, and discuss the associated spectral flow. We also investigate Hawking-Turok constrained instantons, which occur in a generic inflationary model. Implementing the regularization and constraint proposed by Kirklin, Turok and Wiseman, we find that those instantons leading to substantial inflation do not possess negative modes. Using an alternate regularization and constraint motivated by reduction from five dimensions, we find a negative mode is present. These investigations shed new light on the suitability of Euclidean quantum gravity as a potential description of our universe

  12. Bounds for nonlinear composites via iterated homogenization

    Science.gov (United States)

    Ponte Castañeda, P.

    2012-09-01

    Improved estimates of the Hashin-Shtrikman-Willis type are generated for the class of nonlinear composites consisting of two well-ordered, isotropic phases distributed randomly with prescribed two-point correlations, as determined by the H-measure of the microstructure. For this purpose, a novel strategy for generating bounds has been developed utilizing iterated homogenization. The general idea is to make use of bounds that may be available for composite materials in the limit when the concentration of one of the phases (say phase 1) is small. It then follows from the theory of iterated homogenization that it is possible, under certain conditions, to obtain bounds for more general values of the concentration, by gradually adding small amounts of phase 1 in incremental fashion, and sequentially using the available dilute-concentration estimate, up to the final (finite) value of the concentration (of phase 1). Such an approach can also be useful when available bounds are expected to be tighter for certain ranges of the phase volume fractions. This is the case, for example, for the "linear comparison" bounds for porous viscoplastic materials, which are known to be comparatively tighter for large values of the porosity. In this case, the new bounds obtained by the above-mentioned "iterated" procedure can be shown to be much improved relative to the earlier "linear comparison" bounds, especially at low values of the porosity and high triaxialities. Consistent with the way in which they have been derived, the new estimates are, strictly, bounds only for the class of multi-scale, nonlinear composites consisting of two well-ordered, isotropic phases that are distributed with prescribed H-measure at each stage in the incremental process. However, given the facts that the H-measure of the sequential microstructures is conserved (so that the final microstructures can be shown to have the same H-measure), and that H-measures are insensitive to length scales, it is conjectured

  13. Central Andean temperature and precipitation measurements and its homogenization

    Science.gov (United States)

    Hunziker, Stefan; Gubler, Stefanie

    2015-04-01

    Observation of climatological parameters and the homogenization of these time series have a well-established history in western countries. This is not the case for many other countries, such as Bolivia and Peru. In Bolivia and Peru, the organization of measurements, quality of measurement equipment, equipment maintenance, training of staff and data management are fundamentally different compared to the western standard. The data needs special attention, because many problems are not detected by standard quality control procedures. Information about the weather stations, best achieved by station visits, is very beneficial. If the cause of the problem is known, some of the data may be corrected. In this study, cases of typical problems and measurement errors will be demonstrated. Much of research on homogenization techniques (up to subdaily scale) has been completed in recent years. However, data sets of the quality of western station networks have been used, and little is known about the performance of homogenization methods on data sets from countries such as Bolivia and Peru. HOMER (HOMogenizaton softwarE in R) is one of the most recent and widely used homogenization softwares. Its performance is tested on Peruvian-like data that has been sourced from Swiss stations (similar station density and metadata availability). The Swiss station network is a suitable test bed, because climate gradients are strong and the terrain is complex, as is also found in the Central Andes. On the other hand, the Swiss station network is dense, and long time series and extensive metadata are available. By subsampling the station network and omitting the metadata, the conditions of a Peruvian test region are mimicked. Results are compared to a dataset homogenized by THOMAS (Tool for Homogenization of Monthly Data Series), the homogenization tool used by MeteoSwiss.

  14. Pyroxene Homogenization and the Isotopic Systematics of Eucrites

    Science.gov (United States)

    Nyquist, L. E.; Bogard, D. D.

    1996-01-01

    The original Mg-Fe zoning of eucritic pyroxenes has in nearly all cases been partly homogenized, an observation that has been combined with other petrographic and compositional criteria to establish a scale of thermal "metamorphism" for eucrites. To evaluate hypotheses explaining development of conditions on the HED parent body (Vesta?) leading to pyroxene homogenization against their chronological implications, it is necessary to know whether pyroxene metamorphism was recorded in the isotopic systems. However, identifying the effects of the thermal metamorphism with specific effects in the isotopic systems has been difficult, due in part to a lack of correlated isotopic and mineralogical studies of the same eucrites. Furthermore, isotopic studies often place high demands on analytical capabilities, resulting in slow growth of the isotopic database. Additionally, some isotopic systems would not respond in a direct and sensitive way to pyroxene homogenization. Nevertheless, sufficient data exist to generalize some observations, and to identify directions of potentially fruitful investigations.

  15. Homogenization technique for strongly heterogeneous zones in research reactors

    International Nuclear Information System (INIS)

    Lee, J.T.; Lee, B.H.; Cho, N.Z.; Oh, S.K.

    1991-01-01

    This paper reports on an iterative homogenization method using transport theory in a one-dimensional cylindrical cell model developed to improve the homogenized cross sections fro strongly heterogeneous zones in research reactors. The flux-weighting homogenized cross sections are modified by a correction factor, the cell flux ratio under an albedo boundary condition. The albedo at the cell boundary is iteratively determined to reflect the geometry effects of the material properties of the adjacent cells. This method has been tested with a simplified core model of the Korea Multipurpose Research Reactor. The results demonstrate that the reaction rates of an off-center control shroud cell, the multiplication factor, and the power distribution of the reactor core are close to those of the fine-mesh heterogeneous transport model

  16. AQUEOUS HOMOGENEOUS REACTORTECHNICAL PANEL REPORT

    Energy Technology Data Exchange (ETDEWEB)

    Diamond, D.J.; Bajorek, S.; Bakel, A.; Flanagan, G.; Mubayi, V.; Skarda, R.; Staudenmeier, J.; Taiwo, T.; Tonoike, K.; Tripp, C.; Wei, T.; Yarsky, P.

    2010-12-03

    Considerable interest has been expressed for developing a stable U.S. production capacity for medical isotopes and particularly for molybdenum- 99 (99Mo). This is motivated by recent re-ductions in production and supply worldwide. Consistent with U.S. nonproliferation objectives, any new production capability should not use highly enriched uranium fuel or targets. Conse-quently, Aqueous Homogeneous Reactors (AHRs) are under consideration for potential 99Mo production using low-enriched uranium. Although the Nuclear Regulatory Commission (NRC) has guidance to facilitate the licensing process for non-power reactors, that guidance is focused on reactors with fixed, solid fuel and hence, not applicable to an AHR. A panel was convened to study the technical issues associated with normal operation and potential transients and accidents of an AHR that might be designed for isotope production. The panel has produced the requisite AHR licensing guidance for three chapters that exist now for non-power reactor licensing: Reac-tor Description, Reactor Coolant Systems, and Accident Analysis. The guidance is in two parts for each chapter: 1) standard format and content a licensee would use and 2) the standard review plan the NRC staff would use. This guidance takes into account the unique features of an AHR such as the fuel being in solution; the fission product barriers being the vessel and attached systems; the production and release of radiolytic and fission product gases and their impact on operations and their control by a gas management system; and the movement of fuel into and out of the reactor vessel.

  17. Homogeneity and thermodynamic identities in geometrothermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Quevedo, Hernando [Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares (Mexico); Universita di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); ICRANet, Rome (Italy); Quevedo, Maria N. [Universidad Militar Nueva Granada, Departamento de Matematicas, Facultad de Ciencias Basicas, Bogota (Colombia); Sanchez, Alberto [CIIDET, Departamento de Posgrado, Queretaro (Mexico)

    2017-03-15

    We propose a classification of thermodynamic systems in terms of the homogeneity properties of their fundamental equations. Ordinary systems correspond to homogeneous functions and non-ordinary systems are given by generalized homogeneous functions. This affects the explicit form of the Gibbs-Duhem relation and Euler's identity. We show that these generalized relations can be implemented in the formalism of black hole geometrothermodynamics in order to completely fix the arbitrariness present in Legendre invariant metrics. (orig.)

  18. A literature review on biotic homogenization

    OpenAIRE

    Guangmei Wang; Jingcheng Yang; Chuangdao Jiang; Hongtao Zhao; Zhidong Zhang

    2009-01-01

    Biotic homogenization is the process whereby the genetic, taxonomic and functional similarity of two or more biotas increases over time. As a new research agenda for conservation biogeography, biotic homogenization has become a rapidly emerging topic of interest in ecology and evolution over the past decade. However, research on this topic is rare in China. Herein, we introduce the development of the concept of biotic homogenization, and then discuss methods to quantify its three components (...

  19. Hybrid diffusion–transport spatial homogenization method

    International Nuclear Information System (INIS)

    Kooreman, Gabriel; Rahnema, Farzad

    2014-01-01

    Highlights: • A new hybrid diffusion–transport homogenization method. • An extension of the consistent spatial homogenization (CSH) transport method. • Auxiliary cross section makes homogenized diffusion consistent with heterogeneous diffusion. • An on-the-fly re-homogenization in transport. • The method is faster than fine-mesh transport by 6–8 times. - Abstract: A new hybrid diffusion–transport homogenization method has been developed by extending the consistent spatial homogenization (CSH) transport method to include diffusion theory. As in the CSH method, an “auxiliary cross section” term is introduced into the source term, making the resulting homogenized diffusion equation consistent with its heterogeneous counterpart. The method then utilizes an on-the-fly re-homogenization in transport theory at the assembly level in order to correct for core environment effects on the homogenized cross sections and the auxiliary cross section. The method has been derived in general geometry and tested in a 1-D boiling water reactor (BWR) core benchmark problem for both controlled and uncontrolled configurations. The method has been shown to converge to the reference solution with less than 1.7% average flux error in less than one third the computational time as the CSH method – 6 to 8 times faster than fine-mesh transport

  20. Infinite dimensional spherical analysis and harmonic analysis for groups acting on homogeneous trees

    DEFF Research Database (Denmark)

    Axelgaard, Emil

    In this thesis, we study groups of automorphisms for homogeneous trees of countable degree by using an inductive limit approach. The main focus is the thourough discussion of two Olshanski spherical pairs consisting of automorphism groups for a homogeneous tree and a homogeneous rooted tree, resp...... finite. Finally, we discuss conditionally positive definite functions on the groups and use the generalized Bochner-Godement theorem for Olshanski spherical pairs to prove Levy-Khinchine formulas for both of the considered pairs....

  1. Homogenization Pressure and Temperature Affect Protein Partitioning and Oxidative Stability of Emulsions

    DEFF Research Database (Denmark)

    Horn, Anna Frisenfeldt; Barouh, Nathalie; Nielsen, Nina Skall

    2013-01-01

    The oxidative stability of 10 % fish oil-in-water emulsions was investigated for emulsions prepared under different homogenization conditions. Homogenization was conducted at two different pressures (5 or 22.5 MPa), and at two different temperatures (22 and 72 °C). Milk proteins were used...... prior to homogenization did not have any clear effect on lipid oxidation in either of the two types of emulsions....

  2. Aerodynamic and thermal studies of cans of gas cooled fuel elements; Etudes aerodynamiques et thermiques de gaines d'elements combustibles refroidis par gaz

    Energy Technology Data Exchange (ETDEWEB)

    Gelin, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Milliat, J P [Electricite de France (EDF), 75 - Paris (France)

    1964-07-01

    Research on clusters was undertaken at the CEA in 1959, while studies on herring-bone cans were developed at the EDF Laboratory at Chatou and the CEA laboratory at Saclay at the end of 1959. In 1962, a general study on corrugations was begun at the Saclay Laboratory with a view to improving the clusters, and continued later in both laboratories relative to the internal cooling of annular fuel elements. As these studies progressed, trial facilities were extended while experimental methods have improved constantly. At the present time, both laboratories, working in complete collaboration, have powerful means at their disposal. Work on the clusters has been concerned chiefly with pressure losses due to the assembly parts, and with the temperature variations around the elements of the cluster. In this way, we have been able to determine satisfactorily the hot points of the can, the deformations of the rods and the conditions of stability of these deformations. In the case of the herring-bone cans, studies have been directed to the evolution of performances as a function of the geometric parameters on the one hand, and to the special aerodynamic and thermal features caused by the fins and by interruptions of cartridge on the other hand. These studies have led to a very thorough knowledge of the cartridges chosen for the reactors EDF 2 and EDF 3, and now open up very hopeful prospects for future reactors, particularly those fitted with annular elements; among the alternatives suitable for the inner surface of the annular element can, corrugations and longitudinal fins have been fairly extensively tested over a wide range of Reynolds number. (authors) [French] Les etudes de grappes ont ete entreprises au C.E.A. en 1959, tandis que les etudes de gaines a chevrons se sont developpees au Laboratoire de Chatou de l'EDF et au Laboratoire de Saclay du C.E.A. a la fin de l'annee 1959. En 1962, une etude generale sur les corrugations a ete commencee au Laboratoire de Saclay pour

  3. Self-consolidating concrete homogeneity

    Directory of Open Access Journals (Sweden)

    Jarque, J. C.

    2007-08-01

    Full Text Available Concrete instability may lead to the non-uniform distribution of its properties. The homogeneity of self-consolidating concrete in vertically cast members was therefore explored in this study, analyzing both resistance to segregation and pore structure uniformity. To this end, two series of concretes were prepared, self-consolidating and traditional vibrated materials, with different w/c ratios and types of cement. The results showed that selfconsolidating concretes exhibit high resistance to segregation, albeit slightly lower than found in the traditional mixtures. The pore structure in the former, however, tended to be slightly more uniform, probably as a result of less intense bleeding. Such concretes are also characterized by greater bulk density, lower porosity and smaller mean pore size, which translates into a higher resistance to pressurized water. For pore diameters of over about 0.5 μm, however, the pore size distribution was found to be similar to the distribution in traditional concretes, with similar absorption rates.En este trabajo se estudia la homogeneidad de los hormigones autocompactantes en piezas hormigonadas verticalmente, determinando su resistencia a la segregación y la uniformidad de su estructura porosa, dado que la pérdida de estabilidad de una mezcla puede conducir a una distribución no uniforme de sus propiedades. Para ello se han fabricado dos tipos de hormigones, uno autocompactante y otro tradicional vibrado, con diferentes relaciones a/c y distintos tipos de cemento. Los resultados ponen de manifiesto que los hormigones autocompactantes presentan una buena resistencia a la segregación, aunque algo menor que la registrada en los hormigones tradicionales. A pesar de ello, su estructura porosa tiende a ser ligeramente más uniforme, debido probablemente a un menor sangrado. Asimismo, presentan una mayor densidad aparente, una menor porosidad y un menor tamaño medio de poro, lo que les confiere mejores

  4. Development of a slow mono-kinetic electron source; Etude et realisation d'une source d'electrons lents monocinetiques

    Energy Technology Data Exchange (ETDEWEB)

    Ballu, Y [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1968-06-01

    A comparative study of already existing slow mono-kinetic electron guns shows that those using a 127 degrees electrostatic selector can be improved still further to arrive at the performances obtained with spherical 180 degrees selectors for example. For this reason we have examined the 127 degrees selector theoretically in more detail; it appears that it should be possible to obtain a resolving power better than 30 mV for a current of about 10{sup -10} A, on condition that certain improvements be made to the instrument as normally designed, in particular concerning the entrance and exit slides. As a result, the usual suppressors for the scattered electrons are no longer necessary. The development of this apparatus has been carried out with particular care: the dimensional characteristics are fixed to an accuracy of a few microns, although the instrument can be baked out at 300 C. The experimental results are in excellent agreement with the theoretical predictions: for a current of 10{sup -10} A, the measured resolving power is 24 {+-} 4 mV. The easy detection of the He{sup -} resonance line at 19.3 eV has confirmed the advantages of this apparatus for the study of atomic collisions. (author) [French] L'etude comparative des canons a electrons lents monocinetiques realises jusqu'a present montre que ceux qui utilisent un selecteur electrostatique a 127 degres peuvent etre encore perfectionnes en vue de parvenir aux performances obtenues avec les selecteurs spheriques a 180 degres par exemple. D'ou notre etude theorique approfondie du selecteur a 127 degres qui nous a conduit a esperer une resolution meilleure que 30 mV pour un courant de l'ordre de 10{sup -10} A a condition d'apporter certaines ameliorations a la conception usuelle de cet instrument notamment au niveau des fentes d'entree et de sortie. Par voie de consequence les suppresseurs habituels d'electrons parasites deviennent inutiles. L'etude et la mise au point de l'appareil ont fait l'objet de soins

  5. Multilevel Monte Carlo Approaches for Numerical Homogenization

    KAUST Repository

    Efendiev, Yalchin R.; Kronsbein, Cornelia; Legoll, Fré dé ric

    2015-01-01

    it comes to homogenized solutions, different levels of coarse-grid meshes are used to solve the homogenized equation. We show that, by carefully selecting the number of realizations at each level, we can achieve a speed-up in the computations in comparison

  6. Benchmarking homogenization algorithms for monthly data

    Science.gov (United States)

    Venema, V. K. C.; Mestre, O.; Aguilar, E.; Auer, I.; Guijarro, J. A.; Domonkos, P.; Vertacnik, G.; Szentimrey, T.; Stepanek, P.; Zahradnicek, P.; Viarre, J.; Müller-Westermeier, G.; Lakatos, M.; Williams, C. N.; Menne, M. J.; Lindau, R.; Rasol, D.; Rustemeier, E.; Kolokythas, K.; Marinova, T.; Andresen, L.; Acquaotta, F.; Fratiannil, S.; Cheval, S.; Klancar, M.; Brunetti, M.; Gruber, C.; Prohom Duran, M.; Likso, T.; Esteban, P.; Brandsma, T.; Willett, K.

    2013-09-01

    The COST (European Cooperation in Science and Technology) Action ES0601: Advances in homogenization methods of climate series: an integrated approach (HOME) has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies. The algorithms were validated against a realistic benchmark dataset. Participants provided 25 separate homogenized contributions as part of the blind study as well as 22 additional solutions submitted after the details of the imposed inhomogeneities were revealed. These homogenized datasets were assessed by a number of performance metrics including i) the centered root mean square error relative to the true homogeneous values at various averaging scales, ii) the error in linear trend estimates and iii) traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve precipitation data. Moreover, state-of-the-art relative homogenization algorithms developed to work with an inhomogeneous reference are shown to perform best. The study showed that currently automatic algorithms can perform as well as manual ones.

  7. Investigations into homogenization of electromagnetic metamaterials

    DEFF Research Database (Denmark)

    Clausen, Niels Christian Jerichau

    This dissertation encompasses homogenization methods, with a special interest into their applications to metamaterial homogenization. The first method studied is the Floquet-Bloch method, that is based on the assumption of a material being infinite periodic. Its field can then be expanded in term...

  8. Homogeneity of Prototypical Attributes in Soccer Teams

    Directory of Open Access Journals (Sweden)

    Christian Zepp

    2015-09-01

    Full Text Available Research indicates that the homogeneous perception of prototypical attributes influences several intragroup processes. The aim of the present study was to describe the homogeneous perception of the prototype and to identify specific prototypical subcategories, which are perceived as homogeneous within sport teams. The sample consists of N = 20 soccer teams with a total of N = 278 athletes (age M = 23.5 years, SD = 5.0 years. The results reveal that subcategories describing the cohesiveness of the team and motivational attributes are mentioned homogeneously within sport teams. In addition, gender, identification, team size, and the championship ranking significantly correlate with the homogeneous perception of prototypical attributes. The results are discussed on the basis of theoretical and practical implications.

  9. Multilevel Monte Carlo Approaches for Numerical Homogenization

    KAUST Repository

    Efendiev, Yalchin R.

    2015-10-01

    In this article, we study the application of multilevel Monte Carlo (MLMC) approaches to numerical random homogenization. Our objective is to compute the expectation of some functionals of the homogenized coefficients, or of the homogenized solutions. This is accomplished within MLMC by considering different sizes of representative volumes (RVEs). Many inexpensive computations with the smallest RVE size are combined with fewer expensive computations performed on larger RVEs. Likewise, when it comes to homogenized solutions, different levels of coarse-grid meshes are used to solve the homogenized equation. We show that, by carefully selecting the number of realizations at each level, we can achieve a speed-up in the computations in comparison to a standard Monte Carlo method. Numerical results are presented for both one-dimensional and two-dimensional test-cases that illustrate the efficiency of the approach.

  10. Numerical computing of elastic homogenized coefficients for periodic fibrous tissue

    Directory of Open Access Journals (Sweden)

    Roman S.

    2009-06-01

    Full Text Available The homogenization theory in linear elasticity is applied to a periodic array of cylindrical inclusions in rectangular pattern extending to infinity in the inclusions axial direction, such that the deformation of tissue along this last direction is negligible. In the plane of deformation, the homogenization scheme is based on the average strain energy whereas in the third direction it is based on the average normal stress along this direction. Namely, these average quantities have to be the same on a Repeating Unit Cell (RUC of heterogeneous and homogenized media when using a special form of boundary conditions forming by a periodic part and an affine part of displacement. It exists an infinity of RUCs generating the considered array. The computing procedure is tested with different choices of RUC to control that the results of the homogenization process are independent of the kind of RUC we employ. Then, the dependence of the homogenized coefficients on the microstructure can be studied. For instance, a special anisotropy and the role of the inclusion volume are investigated. In the second part of this work, mechanical traction tests are simulated. We consider two kinds of loading, applying a density of force or imposing a displacement. We test five samples of periodic array containing one, four, sixteen, sixty-four and one hundred of RUCs. The evolution of mean stresses, strains and energy with the numbers of inclusions is studied. Evolutions depend on the kind of loading, but not their limits, which could be predicted by simulating traction test of the homogenized medium.

  11. Soy Protein Isolate-Phosphatidylcholine Nanoemulsions Prepared Using High-Pressure Homogenization.

    Science.gov (United States)

    Li, Yang; Wu, Chang-Ling; Liu, Jun; Zhu, Ying; Zhang, Xiao-Yuan; Jiang, Lian-Zhou; Qi, Bao-Kun; Zhang, Xiao-Nan; Wang, Zhong-Jiang; Teng, Fei

    2018-05-07

    The nanoemulsions of soy protein isolate-phosphatidylcholine (SPI-PC) with different emulsion conditions were studied. Homogenization pressure and homogenization cycle times were varied, along with SPI and PC concentration. Evaluations included turbidity, particle size, ζ-potential, particle distribution index, and turbiscan stability index (TSI). The nanoemulsions had the best stability when SPI was at 1.5%, PC was at 0.22%, the homogenization pressure was 100 MPa and homogenization was performed 4 times. The average particle size of the SPI-PC nanoemulsions was 217 nm, the TSI was 3.02 and the emulsification yield was 93.4% of nanoemulsions.

  12. The influence of non-homogenous dielectric material in the waveguide propagation modes

    Directory of Open Access Journals (Sweden)

    Ion VONCILA

    2006-12-01

    Full Text Available The aim of this paper is to indicate the equations of electromagnetic wave in homogenous and non-homogenous dielectric material, estabilising the bundary conditions and solves by FEM the equations of the electromagnetic wave in the rectangular cavity. By numeric simulation of the waveguide in the cavity there have been studied the modifications of both the ways of propagation and the field’s distribution. The non-homogenous mediums afectes the field’s amplitude, obtaining a non-homogenous distribution. Poyting vector of the wave’s transmision, indicates the energetic flux’s concentration in the air besides the dielectric material.

  13. Generalized quantum theory of recollapsing homogeneous cosmologies

    International Nuclear Information System (INIS)

    Craig, David; Hartle, James B.

    2004-01-01

    A sum-over-histories generalized quantum theory is developed for homogeneous minisuperspace type A Bianchi cosmological models, focusing on the particular example of the classically recollapsing Bianchi type-IX universe. The decoherence functional for such universes is exhibited. We show how the probabilities of decoherent sets of alternative, coarse-grained histories of these model universes can be calculated. We consider in particular the probabilities for classical evolution defined by a suitable coarse graining. For a restricted class of initial conditions and coarse grainings we exhibit the approximate decoherence of alternative histories in which the universe behaves classically and those in which it does not. For these situations we show that the probability is near unity for the universe to recontract classically if it expands classically. We also determine the relative probabilities of quasiclassical trajectories for initial states of WKB form, recovering for such states a precise form of the familiar heuristic 'J·dΣ' rule of quantum cosmology, as well as a generalization of this rule to generic initial states

  14. The ultrasonic copper and brass decontamination study; Etude de la decontamination du cuivre et des laitons en presence d'ultra-sons

    Energy Technology Data Exchange (ETDEWEB)

    Courtault, J; Kerdelleau, J de; Mestre, E [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    The use of ultra-sounds as a decontamination technic does not bring an absolute solution. As a function of the materials it seemed necessary to find what was the optimum conditions for using the ultra-sounds and to define not only the ultra-sonic factors but also the chemical solutions which bring some appreciable decontamination factors without bringing any too important corrosion processus. This report gives the results of this study applied to copper and brass. This study allowed to select some effective treatment baths on the two types of contamination: plutonium and fission products. (authors) [French] L'emploi des ultra-sons comme technique de decontamination n'amene pas une solution absolue. Il est apparu necessaire de rechercher en fonction de la nature du materiau a decontaminer quelles etaient les conditions optimales d'utilisation des ultra-sons et de definir alors non seulement les facteurs ultrasoniques mais encore les solutions chimiques qui apportent des facteurs de decontamination appreciables sans amener des phenomenes de corrosion trop importants. Ce rapport donne les resultats de cette etude appliquee au cuivre et aux laitons. Cette etude a permis de selectionner des bains de traitement efficaces dans les deux cas de contamination: plutonium et produits de fission. (auteurs)

  15. Treatment of effluent at the Saclay Centre d'Etudes Nucleaires (1960); Le traitement des effluents du Centre d'Etudes Nucleaires de Saclay (1960)

    Energy Technology Data Exchange (ETDEWEB)

    Wormser, G [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1960-07-01

    The Centre d'Etudes Nucleaires at Saclay possesses several installations from which liquid radioactive effluent is rejected, and it has thus been found necessary to construct a station for the purification of radioactive liquids and to settle various chemical, analytical and technological problems. This report describes, in the following order: - the disposal possibilities at the Centre d'Etudes Nucleaires, Saclay, - the effluents produced at the centre, - the set-up for collecting effluent, - treatment of the effluent, - results of these treatments. (author) [French] La presence, au Centre d'Etudes Nucleaires de Saclay, de plusieurs installations susceptibles de rejeter des effluents liquides radioactifs a necessite la construction d'une station d'epuration d'eaux radioactives et la mise au point de differents problemes chimiques, analytiques et technologiques. Dans ce rapport, nous exposerons successivement: - les possibilites de rejet du Centre d'Etudes Nucleaires de Saclay, - les effluents du centre, - le dispositif de collecte des effluents, - le traitement de ces effluents, - les resultats de ces traitements. (auteur)

  16. String pair production in non homogeneous backgrounds

    Energy Technology Data Exchange (ETDEWEB)

    Bolognesi, S. [Department of Physics “E. Fermi” University of Pisa, and INFN - Sezione di Pisa,Largo Pontecorvo, 3, Ed. C, 56127 Pisa (Italy); Rabinovici, E. [Racah Institute of Physics, The Hebrew University of Jerusalem,91904 Jerusalem (Israel); Tallarita, G. [Departamento de Ciencias, Facultad de Artes Liberales,Universidad Adolfo Ibáñez, Santiago 7941169 (Chile)

    2016-04-28

    We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is less suppressed than the rate of particle pair production. We discuss in some detail how the critical field is affected by the non-homogeneity, for both time and space dependent electric field backgrouds. We also comment on what could be an interesting new prediction for the small field limit. The third case we consider is pair production in holographic confining backgrounds with homogeneous and non-homogeneous fields.

  17. String pair production in non homogeneous backgrounds

    International Nuclear Information System (INIS)

    Bolognesi, S.; Rabinovici, E.; Tallarita, G.

    2016-01-01

    We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is less suppressed than the rate of particle pair production. We discuss in some detail how the critical field is affected by the non-homogeneity, for both time and space dependent electric field backgrouds. We also comment on what could be an interesting new prediction for the small field limit. The third case we consider is pair production in holographic confining backgrounds with homogeneous and non-homogeneous fields.

  18. Etudes sur le Portugal au Temps de l'Humanisme

    Directory of Open Access Journals (Sweden)

    J. Cruz Costa

    1953-06-01

    Full Text Available BATAILLON (Marcel. — Etudes sur le Portugal au Temps de l'Humanisme.  Acta Universitatis Conimbrigencis, 1952, 309 pp. (Primeiro Parágrafo do Artigo O Prof. Marcel Bataillon, erudito dos mais inteligentes da França atual, autor de uma obra que é hoje impr:scindível para quem pretenda estudar o humanismo renascentista na Espanha ou em Portugal, diríamos melhor, talvez: para quem pretenda estudar o Humanismo e a Renascença, — acaba de publicar, na coleção Acta Universitatis Conimbrigencis, êste volume no qual reune alguns trabalhos da mais alta importância para o conhecimento de muitos aspectos da vida espiritual portuguêsa do século XVI.

  19. Induction, bounding, weak combinatorial principles, and the homogeneous model theorem

    CERN Document Server

    Hirschfeldt, Denis R; Shore, Richard A

    2017-01-01

    Goncharov and Peretyat'kin independently gave necessary and sufficient conditions for when a set of types of a complete theory T is the type spectrum of some homogeneous model of T. Their result can be stated as a principle of second order arithmetic, which is called the Homogeneous Model Theorem (HMT), and analyzed from the points of view of computability theory and reverse mathematics. Previous computability theoretic results by Lange suggested a close connection between HMT and the Atomic Model Theorem (AMT), which states that every complete atomic theory has an atomic model. The authors show that HMT and AMT are indeed equivalent in the sense of reverse mathematics, as well as in a strong computability theoretic sense and do the same for an analogous result of Peretyat'kin giving necessary and sufficient conditions for when a set of types is the type spectrum of some model.

  20. Homogeneous nucleation, growth and recrystallization of discharge products on electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kappus, W.

    1983-11-01

    The early stage of discharge of electrodes with an electrodissolution/precipitation mechanism is investigated. A theory is proposed for quasi-classical homogeneous nucleation and the subsequent growth. Based on this theory the radii distribution function was calculated for the diffusion-controlled growth of crystallites. Recrystallization was included. The nucleation overpotential was calculated as a function of time for discharges under various conditions.

  1. ETUDE DE LA DISTRIBUTION DES CATIONS ECHANGEABLES

    African Journals Online (AJOL)

    SEI Joseph

    C'est donc dans le cadre de la modélisation du climat régional que ... Les cartes ont été réalisées grâce au logiciel de cartographie Ferret version 6.0 élaboré par le ... reanalyse météorologique utilisées comme conditions initiales au modèle.

  2. ETUDE DE LA DISTRIBUTION DES CATIONS ECHANGEABLES

    African Journals Online (AJOL)

    SEI Joseph

    Sa valorisation passe par l'étude de sa biologie en milieu naturel, puis en conditions contrôlées. Les variations saisonnières de la croissance et de la capacité reproductive de l'algue rouge Hypnea musciformis ont été suivies durant deux années dans deux localités différentes au niveau de la côte atlantique marocaine.

  3. Homogenization of Stokes and Navier-Stokes equations

    International Nuclear Information System (INIS)

    Allaire, G.

    1990-04-01

    This thesis is devoted to homogenization of Stokes and Navier-Stokes equations with a Dirichlet boundary condition in a domain containing many tiny obstacles. Tipycally those obstacles are distributed at the modes of a periodic lattice with same small period in each axe's direction, and their size is always asymptotically smaller than the lattice's step. With the help of the energy method, and thanks to a suitable pressure's extension, we prove the convergence of the homogenization process when the lattice's step tends to zero (and thus the number of obstacles tends to infinity). For a so-called critical size of the obstacles, the homogenized problem turns out to be a Brinkman's law (i.e. Stokes or Navier-Stokes equation plus a linear zero-order term for the velocity in the momentum equation). For obstacles which have a size smaller than the critical one, the limit problem reduces to the initial Stokes or Navier-Stokes equations, while for larger sizes the homogenized problem a Darcy's law. Furthermore, those results have been extended to the case of obstacles included in a hyperplane, and we establish a simple model of fluid flows through grids, which is based on a special form of Brinkman's law [fr

  4. Poisson-Jacobi reduction of homogeneous tensors

    International Nuclear Information System (INIS)

    Grabowski, J; Iglesias, D; Marrero, J C; Padron, E; Urbanski, P

    2004-01-01

    The notion of homogeneous tensors is discussed. We show that there is a one-to-one correspondence between multivector fields on a manifold M, homogeneous with respect to a vector field Δ on M, and first-order polydifferential operators on a closed submanifold N of codimension 1 such that Δ is transversal to N. This correspondence relates the Schouten-Nijenhuis bracket of multivector fields on M to the Schouten-Jacobi bracket of first-order polydifferential operators on N and generalizes the Poissonization of Jacobi manifolds. Actually, it can be viewed as a super-Poissonization. This procedure of passing from a homogeneous multivector field to a first-order polydifferential operator can also be understood as a sort of reduction; in the standard case-a half of a Poisson reduction. A dual version of the above correspondence yields in particular the correspondence between Δ-homogeneous symplectic structures on M and contact structures on N

  5. Computational Method for Atomistic-Continuum Homogenization

    National Research Council Canada - National Science Library

    Chung, Peter

    2002-01-01

    The homogenization method is used as a framework for developing a multiscale system of equations involving atoms at zero temperature at the small scale and continuum mechanics at the very large scale...

  6. Homogenization and Control of Lattice Structures

    National Research Council Canada - National Science Library

    Blankenship, G. L

    1985-01-01

    ...., trusses may be modeled by beam equations). Using a technique from the mathematics of asymptotic analysis called "homogenization," the author shows how such approximations may be derived in a systematic way that avoids errors made using...

  7. Homogenization of High-Contrast Brinkman Flows

    KAUST Repository

    Brown, Donald L.; Efendiev, Yalchin R.; Li, Guanglian; Savatorova, Viktoria

    2015-01-01

    , Homogenization: Methods and Applications, Transl. Math. Monogr. 234, American Mathematical Society, Providence, RI, 2007, G. Allaire, SIAM J. Math. Anal., 23 (1992), pp. 1482--1518], although a powerful tool, are not applicable here. Our second point

  8. Homogenized thermal conduction model for particulate foods

    OpenAIRE

    Chinesta , Francisco; Torres , Rafael; Ramón , Antonio; Rodrigo , Mari Carmen; Rodrigo , Miguel

    2002-01-01

    International audience; This paper deals with the definition of an equivalent thermal conductivity for particulate foods. An homogenized thermal model is used to asses the effect of particulate spatial distribution and differences in thermal conductivities. We prove that the spatial average of the conductivity can be used in an homogenized heat transfer model if the conductivity differences among the food components are not very large, usually the highest conductivity ratio between the foods ...

  9. Layout optimization using the homogenization method

    Science.gov (United States)

    Suzuki, Katsuyuki; Kikuchi, Noboru

    1993-01-01

    A generalized layout problem involving sizing, shape, and topology optimization is solved by using the homogenization method for three-dimensional linearly elastic shell structures in order to seek a possibility of establishment of an integrated design system of automotive car bodies, as an extension of the previous work by Bendsoe and Kikuchi. A formulation of a three-dimensional homogenized shell, a solution algorithm, and several examples of computing the optimum layout are presented in this first part of the two articles.

  10. Diffusion piecewise homogenization via flux discontinuity ratios

    International Nuclear Information System (INIS)

    Sanchez, Richard; Dante, Giorgio; Zmijarevic, Igor

    2013-01-01

    We analyze piecewise homogenization with flux-weighted cross sections and preservation of averaged currents at the boundary of the homogenized domain. Introduction of a set of flux discontinuity ratios (FDR) that preserve reference interface currents leads to preservation of averaged region reaction rates and fluxes. We consider the class of numerical discretizations with one degree of freedom per volume and per surface and prove that when the homogenization and computing meshes are equal there is a unique solution for the FDRs which exactly preserve interface currents. For diffusion sub-meshing we introduce a Jacobian-Free Newton-Krylov method and for all cases considered obtain an 'exact' numerical solution (eight digits for the interface currents). The homogenization is completed by extending the familiar full assembly homogenization via flux discontinuity factors to the sides of regions laying on the boundary of the piecewise homogenized domain. Finally, for the familiar nodal discretization we numerically find that the FDRs obtained with no sub-mesh (nearly at no cost) can be effectively used for whole-core diffusion calculations with sub-mesh. This is not the case, however, for cell-centered finite differences. (authors)

  11. ETUDE DE LA DISTRIBUTION DES CATIONS ECHANGEABLES

    African Journals Online (AJOL)

    SEI Joseph

    nombre de ramification à 1 cm de l'apex) montre, une hétérogénéité de la population, ce qui confirmerait la forte ... Salinas [8] a mis au point une méthode de réensemencement basée sur l'initiation, en conditions ... sesquipedale, l'étude de son cycle de reproduction et la compréhension de la biologie de l'espèce dans son ...

  12. Fourier transform and mean quadratic variation of Bernoulli convolution on homogeneous Cantor set

    Energy Technology Data Exchange (ETDEWEB)

    Yu Zuguo E-mail: yuzg@hotmail.comz.yu

    2004-07-01

    For the Bernoulli convolution on homogeneous Cantor set, under some condition, it is proved that the mean quadratic variation and the average of Fourier transform of this measure are bounded above and below.

  13. A Perron-Frobenius Theorem for Positive Quasipolynomial Matrices Associated with Homogeneous Difference Equations

    Directory of Open Access Journals (Sweden)

    Bui The Anh

    2007-01-01

    Full Text Available We extend the classical Perron-Frobenius theorem for positive quasipolynomial matrices associated with homogeneous difference equations. Finally, the result obtained is applied to derive necessary and sufficient conditions for the stability of positive system.

  14. Homogenized description and retrieval method of nonlinear metasurfaces

    Science.gov (United States)

    Liu, Xiaojun; Larouche, Stéphane; Smith, David R.

    2018-03-01

    A patterned, plasmonic metasurface can strongly scatter incident light, functioning as an extremely low-profile lens, filter, reflector or other optical device. When the metasurface is patterned uniformly, its linear optical properties can be expressed using effective surface electric and magnetic polarizabilities obtained through a homogenization procedure. The homogenized description of a nonlinear metasurface, however, presents challenges both because of the inherent anisotropy of the medium as well as the much larger set of potential wave interactions available, making it challenging to assign effective nonlinear parameters to the otherwise inhomogeneous layer of metamaterial elements. Here we show that a homogenization procedure can be developed to describe nonlinear metasurfaces, which derive their nonlinear response from the enhanced local fields arising within the structured plasmonic elements. With the proposed homogenization procedure, we are able to assign effective nonlinear surface polarization densities to a nonlinear metasurface, and link these densities to the effective nonlinear surface susceptibilities and averaged macroscopic pumping fields across the metasurface. These effective nonlinear surface polarization densities are further linked to macroscopic nonlinear fields through the generalized sheet transition conditions (GSTCs). By inverting the GSTCs, the effective nonlinear surface susceptibilities of the metasurfaces can be solved for, leading to a generalized retrieval method for nonlinear metasurfaces. The application of the homogenization procedure and the GSTCs are demonstrated by retrieving the nonlinear susceptibilities of a SiO2 nonlinear slab. As an example, we investigate a nonlinear metasurface which presents nonlinear magnetoelectric coupling in near infrared regime. The method is expected to apply to any patterned metasurface whose thickness is much smaller than the wavelengths of operation, with inclusions of arbitrary geometry

  15. Nonlinear vibration of a traveling belt with non-homogeneous boundaries

    Science.gov (United States)

    Ding, Hu; Lim, C. W.; Chen, Li-Qun

    2018-06-01

    Free and forced nonlinear vibrations of a traveling belt with non-homogeneous boundary conditions are studied. The axially moving materials in operation are always externally excited and produce strong vibrations. The moving materials with the homogeneous boundary condition are usually considered. In this paper, the non-homogeneous boundaries are introduced by the support wheels. Equilibrium deformation of the belt is produced by the non-homogeneous boundaries. In order to solve the equilibrium deformation, the differential and integral quadrature methods (DIQMs) are utilized to develop an iterative scheme. The influence of the equilibrium deformation on free and forced nonlinear vibrations of the belt is explored. The DIQMs are applied to solve the natural frequencies and forced resonance responses of transverse vibration around the equilibrium deformation. The Galerkin truncation method (GTM) is utilized to confirm the DIQMs' results. The numerical results demonstrate that the non-homogeneous boundary conditions cause the transverse vibration to deviate from the straight equilibrium, increase the natural frequencies, and lead to coexistence of square nonlinear terms and cubic nonlinear terms. Moreover, the influence of non-homogeneous boundaries can be exacerbated by the axial speed. Therefore, non-homogeneous boundary conditions of axially moving materials especially should be taken into account.

  16. Ceria powders by homogeneous precipitation technique

    International Nuclear Information System (INIS)

    Ramanathan, S.; Roy, S.K.

    2003-01-01

    Formation of precursors for ceria by two homogeneous precipitation reactions - (cerium chloride + urea at 95 degC - called reaction A and cerium chloride + hexamethylenetetramine at 85 degC - called reaction B) - has been studied. The variation of size of the colloidal particles formed and the zeta potential of the suspensions with progress of reactions exhibited similar trends for both the precipitation processes. Particle size increased from 100 to 300 nm with increasing temperature and extent of reaction. The zeta potential was found to decrease with increasing extent of precipitation in the pH range of 5 to 7. Filtration and drying led to agglomeration of the fine particles in case of the precursor from reaction B. The as-formed precursors were crystalline - a basic carbonate in case of reaction A and hydrous oxide in case of reaction B. It was found that nano-crystalline ceria powders (average crystallite size -10 nm) formed above 400 degC from both these precursors. The agglomerate size (D50) of the precursors and ceria powders formed after calcination at 600 degC varied from 0.7 to 3 μm. Increasing calcination temperature up to 800 degC, increased the crystallite size (50 nm). The zeta potential variation with pH and concentration of an anionic dispersant (Calgon) for the ceria powders formed was studied to determine the ideal conditions for suspension stability. It was found to be maximum (i.e., the suspensions stable) in the pH range of 3 to 4 or Calgon concentration of 0.01 to 0.1 weight percent. (author)

  17. Study of the catalytic activity of mixed non-stoichiometric uranium-thorium oxides in carbon monoxide oxidation; Etude de l'activite catalytique des oxydes mixtes d'uranium et de thorium non stoechiometriques dans l'oxydation du monoxyde de carbone

    Energy Technology Data Exchange (ETDEWEB)

    Brau, G [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1969-06-01

    The aim of this work has been to study the catalytic properties of non-stoichiometric uranium-thorium oxides having the general formula U{sub x}Th{sub 1-x}O{sub 2+y}, for the oxidation of carbon monoxide. The preparation of pure, homogeneous, isotropic solids having good structural stability and a surface area as high as possible calls for a strict control of the conditions of preparation of these oxides right from the preparation of 'mother salts': the mixed oxalates U{sub x}Th{sub 1-x}(C{sub 2}O{sub 4}){sub 2}, 2H{sub 2}O. A study has been made of their physico-chemical properties (overall and surface chemical constitution, texture, structure, electrical conductivity), as well as of their adsorption properties with respect to gaseous species occurring in the catalytic reaction. This analysis has made it possible to put forward a reaction mechanism based on successive oxidations and reductions of the active surface by the reactants. A study of the reactions kinetics has confirmed the existence of this oxidation-reduction mechanism which only occurs for oxides having a uranium content of above 0.0014. The carbon dioxide produced by the reaction acts as an inhibitor by blocking the sites on which carbon monoxide can be adsorbed. These non-stoichiometric mixed oxides are a particularly clear example of catalysis by oxygen exchange between the solid and the gas phase. (author) [French] Ce travail a pour but l'etude des proprietes catalytiques des oxydes mixtes d'uranium et de thorium non stoechiometriques de formule generale U{sub x}Th{sub 1-x}O{sub 2+y} dans l'oxydation du monoxyde de carbone. L'obtention de solides purs, homogenes, isotropes, de bonne stabilite structurale et d'aire specifique aussi elevee que possible, exige de controler rigoureusement les conditions de preparation de ces oxydes des l'elaboration de leurs 'ascendants': les oxalates mixtes U{sub x}Th{sub 1-x}(C{sub 2}O{sub 4}){sub 2}, 2H{sub 2}O. Leurs proprietes physico-chimiques (composition

  18. Homogenization of variational inequalities and equations defined by pseudomonotone operators

    International Nuclear Information System (INIS)

    Sandrakov, G V

    2008-01-01

    Results on the convergence of sequences of solutions of non-linear equations and variational inequalities for obstacle problems are proved. The variational inequalities and equations are defined by a non-linear, pseudomonotone operator of the second order with periodic, rapidly oscillating coefficients and by sequences of functions characterizing the obstacles and the boundary conditions. Two-scale and macroscale (homogenized) limiting problems for such variational inequalities and equations are obtained. Results on the relationship between solutions of these limiting problems are established and sufficient conditions for the uniqueness of solutions are presented. Bibliography: 25 titles

  19. Integrability of Hamiltonian systems with homogeneous potentials of degree zero

    Energy Technology Data Exchange (ETDEWEB)

    Casale, Guy, E-mail: guy.casale@univ-rennes1.f [IRMAR UMR 6625, Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France); Duval, Guillaume, E-mail: dduuvvaall@wanadoo.f [1 Chemin du Chateau, 76 430 Les Trois Pierres (France); Maciejewski, Andrzej J., E-mail: maciejka@astro.ia.uz.zgora.p [Institute of Astronomy, University of Zielona Gora, Licealna 9, PL-65-417 Zielona Gora (Poland); Przybylska, Maria, E-mail: Maria.Przybylska@astri.uni.torun.p [Torun Centre for Astronomy, N. Copernicus University, Gagarina 11, PL-87-100 Torun (Poland)

    2010-01-04

    We derive necessary conditions for integrability in the Liouville sense of classical Hamiltonian systems with homogeneous potentials of degree zero. We obtain these conditions through an analysis of the differential Galois group of variational equations along a particular solution generated by a non-zero solution d element of C{sup n} of nonlinear equation gradV(d)=d. We prove that when the system is integrable the Hessian matrix V{sup ''}(d) has only integer eigenvalues and is diagonalizable.

  20. Homogeneous anisotropic solutions of topologically massive gravity with a cosmological constant and their homogeneous deformations

    International Nuclear Information System (INIS)

    Moutsopoulos, George

    2013-01-01

    We solve the equations of topologically massive gravity (TMG) with a potentially non-vanishing cosmological constant for homogeneous metrics without isotropy. We only reproduce known solutions. We also discuss their homogeneous deformations, possibly with isotropy. We show that de Sitter space and hyperbolic space cannot be infinitesimally homogeneously deformed in TMG. We clarify some of their Segre–Petrov types and discuss the warped de Sitter spacetime. (paper)

  1. Homogeneous anisotropic solutions of topologically massive gravity with a cosmological constant and their homogeneous deformations

    Science.gov (United States)

    Moutsopoulos, George

    2013-06-01

    We solve the equations of topologically massive gravity (TMG) with a potentially non-vanishing cosmological constant for homogeneous metrics without isotropy. We only reproduce known solutions. We also discuss their homogeneous deformations, possibly with isotropy. We show that de Sitter space and hyperbolic space cannot be infinitesimally homogeneously deformed in TMG. We clarify some of their Segre-Petrov types and discuss the warped de Sitter spacetime.

  2. Broken ergodicity in two-dimensional homogeneous magnetohydrodynamic turbulence

    International Nuclear Information System (INIS)

    Shebalin, John V.

    2010-01-01

    Two-dimensional (2D) homogeneous magnetohydrodynamic (MHD) turbulence has many of the same qualitative features as three-dimensional (3D) homogeneous MHD turbulence. These features include several ideal (i.e., nondissipative) invariants along with the phenomenon of broken ergodicity (defined as nonergodic behavior over a very long time). Broken ergodicity appears when certain modes act like random variables with mean values that are large compared to their standard deviations, indicating a coherent structure or dynamo. Recently, the origin of broken ergodicity in 3D MHD turbulence that is manifest in the lowest wavenumbers was found. Here, we study the origin of broken ergodicity in 2D MHD turbulence. It will be seen that broken ergodicity in ideal 2D MHD turbulence can be manifest in the lowest wavenumbers of a finite numerical model for certain initial conditions or in the highest wavenumbers for another set of initial conditions. The origins of broken ergodicity in an ideal 2D homogeneous MHD turbulence are found through an eigenanalysis of the covariance matrices of the probability density function and by an examination of the associated entropy functional. When the values of ideal invariants are kept fixed and grid size increases, it will be shown that the energy in a few large modes remains constant, while the energy in any other mode is inversely proportional to grid size. Also, as grid size increases, we find that broken ergodicity becomes manifest at more and more wavenumbers.

  3. Desertification, salinization, and biotic homogenization in a dryland river ecosystem.

    Science.gov (United States)

    Miyazono, Seiji; Patiño, Reynaldo; Taylor, Christopher M

    2015-04-01

    This study determined long-term changes in fish assemblages, river discharge, salinity, and local precipitation, and examined hydrological drivers of biotic homogenization in a dryland river ecosystem, the Trans-Pecos region of the Rio Grande/Rio Bravo del Norte (USA/Mexico). Historical (1977-1989) and current (2010-2011) fish assemblages were analyzed by rarefaction analysis (species richness), nonmetric multidimensional scaling (composition/variability), multiresponse permutation procedures (composition), and paired t-test (variability). Trends in hydrological conditions (1970s-2010s) were examined by Kendall tau and quantile regression, and associations between streamflow and specific conductance (salinity) by generalized linear models. Since the 1970s, species richness and variability of fish assemblages decreased in the Rio Grande below the confluence with the Rio Conchos (Mexico), a major tributary, but not above it. There was increased representation of lower-flow/higher-salinity tolerant species, thus making fish communities below the confluence taxonomically and functionally more homogeneous to those above it. Unlike findings elsewhere, this biotic homogenization was due primarily to changes in the relative abundances of native species. While Rio Conchos discharge was>2-fold higher than Rio Grande discharge above their confluence, Rio Conchos discharge decreased during the study period causing Rio Grande discharge below the confluence to also decrease. Rio Conchos salinity is lower than Rio Grande salinity above their confluence and, as Rio Conchos discharge decreased, it caused Rio Grande salinity below the confluence to increase (reduced dilution). Trends in discharge did not correspond to trends in precipitation except at extreme-high (90th quantile) levels. In conclusion, decreasing discharge from the Rio Conchos has led to decreasing flow and increasing salinity in the Rio Grande below the confluence. This spatially uneven desertification and

  4. Desertification, salinization, and biotic homogenization in a dryland river ecosystem

    Science.gov (United States)

    Miyazono, S.; Patino, Reynaldo; Taylor, C.M.

    2015-01-01

    This study determined long-term changes in fish assemblages, river discharge, salinity, and local precipitation, and examined hydrological drivers of biotic homogenization in a dryland river ecosystem, the Trans-Pecos region of the Rio Grande/Rio Bravo del Norte (USA/Mexico). Historical (1977-1989) and current (2010-2011) fish assemblages were analyzed by rarefaction analysis (species richness), nonmetric multidimensional scaling (composition/variability), multiresponse permutation procedures (composition), and paired t-test (variability). Trends in hydrological conditions (1970s-2010s) were examined by Kendall tau and quantile regression, and associations between streamfiow and specific conductance (salinity) by generalized linear models. Since the 1970s, species richness and variability of fish assemblages decreased in the Rio Grande below the confluence with the Rio Conchos (Mexico), a major tributary, but not above it. There was increased representation of lower-flow/higher-salinity tolerant species, thus making fish communities below the confluence taxonomically and functionally more homogeneous to those above it. Unlike findings elsewhere, this biotic homogenization was due primarily to changes in the relative abundances of native species. While Rio Conchos discharge was > 2-fold higher than Rio Grande discharge above their confluence, Rio Conchos discharge decreased during the study period causing Rio Grande discharge below the confluence to also decrease. Rio Conchos salinity is lower than Rio Grande salinity above their confluence and, as Rio Conchos discharge decreased, it caused Rio Grande salinity below the confluence to increase (reduced dilution). Trends in discharge did not correspond to trends in precipitation except at extreme-high (90th quantile) levels. In conclusion, decreasing discharge from the Rio Conchos has led to decreasing flow and increasing salinity in the Rio Grande below the confluence. This spatially uneven desertification and

  5. Rapid biotic homogenization of marine fish assemblages

    Science.gov (United States)

    Magurran, Anne E.; Dornelas, Maria; Moyes, Faye; Gotelli, Nicholas J.; McGill, Brian

    2015-01-01

    The role human activities play in reshaping biodiversity is increasingly apparent in terrestrial ecosystems. However, the responses of entire marine assemblages are not well-understood, in part, because few monitoring programs incorporate both spatial and temporal replication. Here, we analyse an exceptionally comprehensive 29-year time series of North Atlantic groundfish assemblages monitored over 5° latitude to the west of Scotland. These fish assemblages show no systematic change in species richness through time, but steady change in species composition, leading to an increase in spatial homogenization: the species identity of colder northern localities increasingly resembles that of warmer southern localities. This biotic homogenization mirrors the spatial pattern of unevenly rising ocean temperatures over the same time period suggesting that climate change is primarily responsible for the spatial homogenization we observe. In this and other ecosystems, apparent constancy in species richness may mask major changes in species composition driven by anthropogenic change. PMID:26400102

  6. Two-Dimensional Homogeneous Fermi Gases

    Science.gov (United States)

    Hueck, Klaus; Luick, Niclas; Sobirey, Lennart; Siegl, Jonas; Lompe, Thomas; Moritz, Henning

    2018-02-01

    We report on the experimental realization of homogeneous two-dimensional (2D) Fermi gases trapped in a box potential. In contrast to harmonically trapped gases, these homogeneous 2D systems are ideally suited to probe local as well as nonlocal properties of strongly interacting many-body systems. As a first benchmark experiment, we use a local probe to measure the density of a noninteracting 2D Fermi gas as a function of the chemical potential and find excellent agreement with the corresponding equation of state. We then perform matter wave focusing to extract the momentum distribution of the system and directly observe Pauli blocking in a near unity occupation of momentum states. Finally, we measure the momentum distribution of an interacting homogeneous 2D gas in the crossover between attractively interacting fermions and bosonic dimers.

  7. SuPer-Homogenization (SPH) Corrected Cross Section Generation for High Temperature Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Ramazan Sonat [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hummel, Andrew John [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hiruta, Hikaru [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2017-03-01

    The deterministic full core simulators require homogenized group constants covering the operating and transient conditions over the entire lifetime. Traditionally, the homogenized group constants are generated using lattice physics code over an assembly or block in the case of prismatic high temperature reactors (HTR). For the case of strong absorbers that causes strong local depressions on the flux profile require special techniques during homogenization over a large volume. Fuel blocks with burnable poisons or control rod blocks are example of such cases. Over past several decades, there have been a tremendous number of studies performed for improving the accuracy of full-core calculations through the homogenization procedure. However, those studies were mostly performed for light water reactor (LWR) analyses, thus, may not be directly applicable to advanced thermal reactors such as HTRs. This report presents the application of SuPer-Homogenization correction method to a hypothetical HTR core.

  8. Fabrication and characterization of uranium-6--niobium alloy plate with improved homogeneity

    International Nuclear Information System (INIS)

    Snyder, W.B.

    1978-01-01

    Chemical inhomogeneities produced during arc melting of uranium--6 weight percent niobium alloy normally persist during fabrication of the ingot to a finished product. An investigation was directed toward producing a more homogeneous product (approx. 13.0-mm plate) by a combination of mechanical working and homogenization. Ingots were cast, forged to various reductions, homogenized under different conditions, and finally rolled to 13.0-mm-thick plate. It was concluded that increased forging reductions prior to homogenization resulted in a more homogeneous plate. Comparison of calculated and experimentally measured niobium concentration profiles indicated that the activation energy for the diffusion of niobium in uranium--niobium alloys may be lower than previously observed

  9. Internal homogenization: effective permittivity of a coated sphere.

    Science.gov (United States)

    Chettiar, Uday K; Engheta, Nader

    2012-10-08

    The concept of internal homogenization is introduced as a complementary approach to the conventional homogenization schemes, which could be termed as external homogenization. The theory for the internal homogenization of the permittivity of subwavelength coated spheres is presented. The effective permittivity derived from the internal homogenization of coreshells is discussed for plasmonic and dielectric constituent materials. The effective model provided by the homogenization is a useful design tool in constructing coated particles with desired resonant properties.

  10. Statistical methods for assessment of blend homogeneity

    DEFF Research Database (Denmark)

    Madsen, Camilla

    2002-01-01

    In this thesis the use of various statistical methods to address some of the problems related to assessment of the homogeneity of powder blends in tablet production is discussed. It is not straight forward to assess the homogeneity of a powder blend. The reason is partly that in bulk materials......, it is shown how to set up parametric acceptance criteria for the batch that gives a high confidence that future samples with a probability larger than a specified value will pass the USP threeclass criteria. Properties and robustness of proposed changes to the USP test for content uniformity are investigated...

  11. Flows and chemical reactions in homogeneous mixtures

    CERN Document Server

    Prud'homme, Roger

    2013-01-01

    Flows with chemical reactions can occur in various fields such as combustion, process engineering, aeronautics, the atmospheric environment and aquatics. The examples of application chosen in this book mainly concern homogeneous reactive mixtures that can occur in propellers within the fields of process engineering and combustion: - propagation of sound and monodimensional flows in nozzles, which may include disequilibria of the internal modes of the energy of molecules; - ideal chemical reactors, stabilization of their steady operation points in the homogeneous case of a perfect mixture and c

  12. Etude de la qualité physico-chimique et biologique des eaux du ...

    African Journals Online (AJOL)

    Etude de la qualité physico-chimique et biologique des eaux du fleuve Niger à Niamey. ... le récepteur principal des rejets d'eaux usées de la ville de Niamey, capital du ... La description de ces taxons montre une variation de la structure des ...

  13. English Department Reforms at the Hautes Etudes Commerciales: Entering the Nineties.

    Science.gov (United States)

    Shanahan, Daniel

    1993-01-01

    Discusses the reforms made in the fall of 1990 in the English department at the Ecole Hautes Etudes Commerciales (Paris, France), which were based on the basis of a combination of literature-culture and second- and foreign-language acquisition pedagogical biases. (four references) (VWL)

  14. Contribution a l'etude des plantes alimentaires mineures dans la ...

    African Journals Online (AJOL)

    Contribution a l'etude des plantes alimentaires mineures dans la prefecture de Dankpen (Togo). AB Kebenzikato, S Akpavi, K Batawila, K Wala, M Dourma, K Kossi-Titrikou, KS Amouzou, I Butare, H Dantsey-Barry, K Akpagana ...

  15. 152 Etude de cas sur l'impact des amendements organiques vis-à ...

    African Journals Online (AJOL)

    john mukalay

    Etude de cas sur l'impact des amendements organiques vis-à-vis de la salinité en culture de bananier. Michel Mazinga KWEY1, Séverin Kalala BANZE2 et John Banza MUKALAY2*. 1Laboratoire des cultures in vitro, Département de phytotechnie, Faculté des sciences agronomiques,. Université de Lubumbashi, BP 1825, ...

  16. 186 Etude théorique du transport électronique par la simulation ...

    African Journals Online (AJOL)

    youness

    Choukria SAYAH et al. 186. Etude théorique du ... For that we carried out the microscopic simulations, based on the Monte. Carlo method. ... intervalles, piezoelectric as well as the interactions of alloy and on ionized impurities. ..... SAYA et al. 198. [5] - R. W. Hockney, J. W. Eastwood, "Computer simulation using particles",.

  17. Etude comparative de la flore aux abords des cours d'eau dans les ...

    African Journals Online (AJOL)

    Etude comparative de la flore aux abords des cours d'eau dans les zones hypo et hyper endémiques d'ulcère de Buruli en Côte d'Ivoire. C. Cisse Boni, E. Ehouman, D. Soro, M.W. Kone, A. Bakayoko, F. Dembele, K. Bauthire, M Dosso ...

  18. Homogenization versus homogenization-free method to measure muscle glycogen fractions.

    Science.gov (United States)

    Mojibi, N; Rasouli, M

    2016-12-01

    The glycogen is extracted from animal tissues with or without homogenization using cold perchloric acid. Three methods were compared for determination of glycogen in rat muscle at different physiological states. Two groups of five rats were kept at rest or 45 minutes muscular activity. The glycogen fractions were extracted and measured by using three methods. The data of homogenization method shows that total glycogen decreased following 45 min physical activity and the change occurred entirely in acid soluble glycogen (ASG), while AIG did not change significantly. Similar results were obtained by using "total-glycogen-fractionation methods". The findings of "homogenization-free method" indicate that the acid insoluble fraction (AIG) was the main portion of muscle glycogen and the majority of changes occurred in AIG fraction. The results of "homogenization method" are identical with "total glycogen fractionation", but differ with "homogenization-free" protocol. The ASG fraction is the major portion of muscle glycogen and is more metabolically active form.

  19. Effect of high-pressure homogenization on different matrices of food supplements.

    Science.gov (United States)

    Martínez-Sánchez, Ascensión; Tarazona-Díaz, Martha Patricia; García-González, Antonio; Gómez, Perla A; Aguayo, Encarna

    2016-12-01

    There is a growing demand for food supplements containing high amounts of vitamins, phenolic compounds and mineral content that provide health benefits. Those functional compounds have different solubility properties, and the maintenance of their compounds and the guarantee of their homogenic properties need the application of novel technologies. The quality of different drinkable functional foods after thermal processing (0.1 MPa) or high-pressure homogenization under two different conditions (80 MPa, 33 ℃ and 120 MPa, 43 ℃) was studied. Physicochemical characteristics and sensory qualities were evaluated throughout the six months of accelerated storage at 40 ℃ and 75% relative humidity (RH). Aroma and color were better maintained in high-pressure homogenization-treated samples than the thermally treated ones, which contributed significantly to extending their shelf life. The small particle size obtained after high-pressure homogenization treatments caused differences in turbidity and viscosity with respect to heat-treated samples. The use of high-pressure homogenization, more specifically, 120 MPa, provided active ingredient homogeneity to ensure uniform content in functional food supplements. Although the effect of high-pressure homogenization can be affected by the food matrix, high-pressure homogenization can be implemented as an alternative to conventional heat treatments in a commercial setting within the functional food supplement or pharmaceutical industry. © The Author(s) 2016.

  20. Effects of homogenization treatment on recrystallization behavior of 7150 aluminum sheet during post-rolling annealing

    International Nuclear Information System (INIS)

    Guo, Zhanying; Zhao, Gang; Chen, X.-Grant

    2016-01-01

    The effects of two homogenization treatments applied to the direct chill (DC) cast billet on the recrystallization behavior in 7150 aluminum alloy during post-rolling annealing have been investigated using the electron backscatter diffraction (EBSD) technique. Following hot and cold rolling to the sheet, measured orientation maps, the recrystallization fraction and grain size, the misorientation angle and the subgrain size were used to characterize the recovery and recrystallization processes at different annealing temperatures. The results were compared between the conventional one-step homogenization and the new two-step homogenization, with the first step being pretreated at 250 °C. Al_3Zr dispersoids with higher densities and smaller sizes were obtained after the two-step homogenization, which strongly retarded subgrain/grain boundary mobility and inhibited recrystallization. Compared with the conventional one-step homogenized samples, a significantly lower recrystallized fraction and a smaller recrystallized grain size were obtained under all annealing conditions after cold rolling in the two-step homogenized samples. - Highlights: • Effects of two homogenization treatments on recrystallization in 7150 Al sheets • Quantitative study on the recrystallization evolution during post-rolling annealing • Al_3Zr dispersoids with higher densities and smaller sizes after two-step treatment • Higher recrystallization resistance of 7150 sheets with two-step homogenization

  1. Alecto 2 - interaction studies; Alecto 2 - etudes d'interaction

    Energy Technology Data Exchange (ETDEWEB)

    Brunet, J P; Clouet d' Orval, Ch; Mougniot, J C; Penet, F [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    Weak interactions were experimentally studies with the tank of the critical assembly Alecto II and one, two or three bottles containing solutions of various concentrations. In particular, was studied the validity of certain classical assumptions, shielding effects, screening and semi-reflexion effects, importance of thermal coupling. The method of the 'k{sub eff}, solid angle' is shown to apply to such a system. The determination by divergence and pulsed neutron technique of the reactivity related to a millimeter of solution level affords the obtention of critical heights in terms of reactivity. (authors) [French] Une etude experimentale d'interactions faibles a ete faite entre la cuve de l'experience critique ALECTO II et une, deux ou trois bouteilles contenant des concentrations variees. On etudie, en particulier, la validite de certaines hypotheses classiques, effets d'ombre, d'ecrans, de semi-reflexion, importance du couplage thermique. On montre d'autre part que la methode du 'K{sub eff}, angle solide' peut s'appliquer a un tel systeme. La determination par divergence et neutrons pulses de la reactivite liee au millimetre de solution permet de traduire les hauteurs critiques obtenues, en terme de reactivite. (auteurs)

  2. Baby fission chambers; Etude de chambres a fission miniatures

    Energy Technology Data Exchange (ETDEWEB)

    Guery, U; Tachon, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    The present report is intended, on the one band, as a study of the main types of fission chambers produced to date, and on the other, to deal more generally with this type of detector. Originally, it was with a view to the charting of neutron scatter in 'Proserpine' that the authors undertook the study of these chambers. During the course of the task, it was considered worth tbe trouble of developing its scope to include a more general application: neutron scatter measurement of various energy neutrons within a reduced volume with slight local disturbance. (author) [French] Le present rapport se propose, d'une part, d'exposer les principales realisations de chambres a fission, d'autre part de faire une mise au point a caractere plus general sur ces detecteurs. Au depart, c'est surtout en vue des mesures de densite neutronique dans 'Proserpine' que les auteurs ont etudie ces chambres; au cours de la mise au point, il a paru interessant de developper leur etude pour des applications plus generales: mesures de densites de neutrons de differentes energies dans un element de volume tres reduit et avec faible perturbation locale. (auteur)

  3. SEPA (Service d'etudes, de Procedes et Analyses)

    International Nuclear Information System (INIS)

    2017-01-01

    The SEPA (Service d'etudes, de Procedes et Analyses), is an engineering department specializing in the analysis and processing of uranium ore. It comes from a long tradition of mining in France that began sixty-five years ago with the French Atomic Energy Commission (CEA) and that has been carried on by COGEMA and then Areva. SEPA brings a combination of experience and excellence to its activities thanks to its multidisciplinary staff (mineralogists, chemists, mechanical engineers, instrumentation specialists...), who come from diverse cultural backgrounds. Today, the SEPA draws on its wealth of know-how and expertise to devise and develop new methods for processing and valorizing ores everywhere in the world. Its mission is to: - Develop and conduct laboratory tests on methods for processing uranium and other valuable elements such as molybdenum, vanadium, rare earths, niobium, tantalum and thorium; - Analyze ores obtained during prospecting at locations all over the world; -Serve as an advisor in the commissioning of Areva industrial units and ore processing plants; -Perform environmental analyses during the full period of mining operations; -Conduct audits and provide advice on processes and analysis methods; -Carry out research and development in all aspects of minerals treatment (including the filing of patents). The SEPA combines experience, skills and a global approach to technologies used in ore processing. Its role is to continually improve the processes for extracting, processing and valorizing ores while protecting the environment

  4. Baby fission chambers; Etude de chambres a fission miniatures

    Energy Technology Data Exchange (ETDEWEB)

    Guery, U.; Tachon, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1957-07-01

    The present report is intended, on the one band, as a study of the main types of fission chambers produced to date, and on the other, to deal more generally with this type of detector. Originally, it was with a view to the charting of neutron scatter in 'Proserpine' that the authors undertook the study of these chambers. During the course of the task, it was considered worth tbe trouble of developing its scope to include a more general application: neutron scatter measurement of various energy neutrons within a reduced volume with slight local disturbance. (author) [French] Le present rapport se propose, d'une part, d'exposer les principales realisations de chambres a fission, d'autre part de faire une mise au point a caractere plus general sur ces detecteurs. Au depart, c'est surtout en vue des mesures de densite neutronique dans 'Proserpine' que les auteurs ont etudie ces chambres; au cours de la mise au point, il a paru interessant de developper leur etude pour des applications plus generales: mesures de densites de neutrons de differentes energies dans un element de volume tres reduit et avec faible perturbation locale. (auteur)

  5. The homogeneous marginal utility of income assumption

    NARCIS (Netherlands)

    Demuynck, T.

    2015-01-01

    We develop a test to verify if every agent from a population of heterogeneous consumers has the same marginal utility of income function. This homogeneous marginal utility of income assumption is often (implicitly) used in applied demand studies because it has nice aggregation properties and

  6. Synthesis of silica nanosphere from homogeneous and ...

    Indian Academy of Sciences (India)

    WINTEC

    avoid it, reaction in heterogeneous system using CTABr was carried out. Nanosized silica sphere with ... Homogeneous system contains a mixture of ethanol, water, aqueous ammonia and ... heated to 823 K (rate, 1 K/min) in air and kept at this.

  7. Gravitational Metric Tensor Exterior to Rotating Homogeneous ...

    African Journals Online (AJOL)

    The covariant and contravariant metric tensors exterior to a homogeneous spherical body rotating uniformly about a common φ axis with constant angular velocity ω is constructed. The constructed metric tensors in this gravitational field have seven non-zero distinct components.The Lagrangian for this gravitational field is ...

  8. Homogeneous nucleation of water in synthetic air

    NARCIS (Netherlands)

    Fransen, M.A.L.J.; Sachteleben, E.; Hruby, J.; Smeulders, D.M.J.; DeMott, P.J.; O'Dowd, C.D.

    2013-01-01

    Homogeneous nucleation rates for water vapor in synthetic air are measured by means of a Pulse-Expansion Wave Tube (PEWT). A comparison of the experimental nucleation rates with the Classical Nucleation Theory (CNT) shows that a more elaborated model is necessary to describe supercooled water

  9. Homogeneity in Social Groups of Iraqis

    NARCIS (Netherlands)

    Gresham, J.; Saleh, F.; Majid, S.

    With appreciation to the Royal Institute for Inter-Faith Studies for initiating the Second World Congress for Middle Eastern Studies, this paper summarizes findings on homogeneity in community-level social groups derived from inter-ethnic research conducted during 2005 among Iraqi Arabs and Kurds

  10. Abelian gauge theories on homogeneous spaces

    International Nuclear Information System (INIS)

    Vassilevich, D.V.

    1992-07-01

    An algebraic technique of separation of gauge modes in Abelian gauge theories on homogeneous spaces is proposed. An effective potential for the Maxwell-Chern-Simons theory on S 3 is calculated. A generalization of the Chern-Simons action is suggested and analysed with the example of SU(3)/U(1) x U(1). (author). 11 refs

  11. Benchmarking homogenization algorithms for monthly data

    Czech Academy of Sciences Publication Activity Database

    Venema, V. K. C.; Mestre, O.; Aquilar, E.; Auer, I.; Guijarro, J. A.; Domonkos, P.; Vertačník, G.; Szentimrey, T.; Štěpánek, Petr; Zahradníček, Pavel; Viarre, J.; Mueller-Westermeier, G.; Lakatos, M.; Williams, C. N.; Menne, M. J.; Lindau, R.; Rasol, D.; Rustemeier, E.; Kolokythas, K.; Marinova, T.; Andresen, L.; Acquaotta, F.; Fratianni, S.; Cheval, S.; Klancar, M.; Brunetti, M.; Gruber, C.; Duran, M. P.; Likso, T.; Esteban, P.; Brandsma, T.

    2012-01-01

    Roč. 8, č. 1 (2012), s. 89-115 ISSN 1814-9324 Institutional support: RVO:67179843 Keywords : climate data * instrumental time-series * greater alpine region * homogeneity test * variability * inhomogeneities Subject RIV: EH - Ecology, Behaviour Impact factor: 3.556, year: 2012

  12. Extension theorems for homogenization on lattice structures

    Science.gov (United States)

    Miller, Robert E.

    1992-01-01

    When applying homogenization techniques to problems involving lattice structures, it is necessary to extend certain functions defined on a perforated domain to a simply connected domain. This paper provides general extension operators which preserve bounds on derivatives of order l. Only the special case of honeycomb structures is considered.

  13. Homogeneous scintillating LKr/Xe calorimeters

    International Nuclear Information System (INIS)

    Chen, M.; Mullins, M.; Pelly, D.; Shotkin, S.; Sumorok, K.; Akyuz, D.; Chen, E.; Gaudreau, M.P.J.; Bolozdynya, A.; Tchernyshev, V.; Goritchev, P.; Khovansky, V.; Koutchenkov, A.; Kovalenko, A.; Lebedenko, V.; Vinogradov, V.; Gusev, L.; Sheinkman, V.; Krasnokutsky, R.N.; Shuvalov, R.S.; Fedyakin, N.N.; Sushkov, V.; Akopyan, M.; Doke, T.; Kikuchi, J.; Hitachi, A.; Kashiwagi, T.; Masuda, K.; Shibamura, E.; Ishida, N.; Sugimoto, S.

    1993-01-01

    Recent R and D work on full length scintillating homogeneous liquid xenon/krypton (LXe/Kr) cells has established the essential properties for precision EM calorimeters: In-situ calibration using α's, radiation hardness as well as the uniformity required for δE/E≅0.5% for e/γ's above 50 GeV. (orig.)

  14. Traffic planning for non-homogeneous traffic

    Indian Academy of Sciences (India)

    Western traffic planning methodologies mostly address the concerns of homogeneous traffic and therefore often prove inadequate in solving problems involving ... Transportation Research and Injury Prevention Programme, Indian Institute of Technology, Hauz Khas, New Delhi 110 016; Civil and Architectural Engineering ...

  15. Inverse acoustic problem of N homogeneous scatterers

    DEFF Research Database (Denmark)

    Berntsen, Svend

    2002-01-01

    The three-dimensional inverse acoustic medium problem of N homogeneous objects with known geometry and location is considered. It is proven that one scattering experiment is sufficient for the unique determination of the complex wavenumbers of the objects. The mapping from the scattered fields...

  16. Mach's principle in spatially homogeneous spacetimes

    International Nuclear Information System (INIS)

    Tipler, F.J.

    1978-01-01

    On the basis of Mach's Principle it is concluded that the only singularity-free solution to the empty space Einstein equations is flat space. It is shown that the only singularity-free solution to the empty space Einstein equations which is spatially homogeneous and globally hyperbolic is in fact suitably identified Minkowski space. (Auth.)

  17. Water Filtration through Homogeneous Granulated Charge

    Directory of Open Access Journals (Sweden)

    A. M. Krautsou

    2005-01-01

    Full Text Available General relationship for calculation of water filtration through homogeneous granulated charge has been obtained. The obtained relationship has been compared with experimental data. Discrepancies between calculated and experimental values do not exceed 6 % throughout the entire investigated range.

  18. The influence of homogenization on the calculation of the sensitivity volume of a BWR incore detector

    International Nuclear Information System (INIS)

    Haghighat, A.; Kosaly, G.

    1985-01-01

    By performing two-group, X-Y, S 4 transport theory calculations with the albedo boundary condition, the effect of heterogeneities on the BWR incore detector has been investigated. The albedo distribution along the boundary of the control volume is obtained using a two-group, homogenous, X-Y diffusion model. Different degrees of homogenization have been examined. Investigation shows that a cell-homogeneous model, with separated bypass region and inner water gap, is a viable alternative to the heterogeneous approach. This finding contradicts earlier predictions of a need for a heterogeneous model. (author)

  19. The combinational structure of non-homogeneous Markov chains with countable states

    Directory of Open Access Journals (Sweden)

    A. Mukherjea

    1983-01-01

    Full Text Available Let P(s,t denote a non-homogeneous continuous parameter Markov chain with countable state space E and parameter space [a,b], −∞0}. It is shown in this paper that R(s,t is reflexive, transitive, and independent of (s,t, shomogeneity condition holds. It is also shown that the relation R(s,t, unlike in the finite state space case, cannot be expressed even as an infinite (countable product of reflexive transitive relations for certain non-homogeneous chains in the case when E is infinite.

  20. Homogenate extraction of crude polysaccharides from Lentinus edodes and evaluation of the antioxidant activity

    Directory of Open Access Journals (Sweden)

    Leqin KE

    2016-01-01

    Full Text Available Abstract Crude polysaccharides of Lentinus edodes were extracted using homogenate method. Factors affecting the yield of crude polysaccharides were investigated and optimized by response surface methodology. The homogenate extraction method was compared with traditional heating extraction method. The antioxidant activity of crude polysaccharides from Lentinus edodes was evaluated. Results showed that, the optimal conditions of homogenate extraction were as follows: solvent pH, 10; liquid-solid ratio, 30: 1 (mL: g, extraction time, 66 s; number of extraction, 1. Under these conditions, the yield of crude polysaccharides was (13.2 ± 0.9%, which was 29.82% higher than that of traditional heating extraction. Crude polysaccharides of Lentinus edodes had good DPPH scavenging activity. Compared with the traditional heating extraction, the homogenate extraction had notable advantages including good extraction yield, short extraction time and low extraction temperature. It is an efficient way to extract crude polysaccharides from Lentinus edodes.

  1. Feasibility Study of Aseptic Homogenization: Affecting Homogenization Steps on Quality of Sterilized Coconut Milk

    Directory of Open Access Journals (Sweden)

    Phungamngoen Chanthima

    2016-01-01

    Full Text Available Coconut milk is one of the most important protein-rich food sources available today. Separation of an emulsion into an aqueous phase and cream phase is commonly occurred and this leads an unacceptably physical defect of either fresh or processed coconut milk. Since homogenization steps are known to affect the stability of coconut milk. This work was aimed to study the effect of homogenization steps on quality of coconut milk. The samples were subject to high speed homogenization in the range of 5000-15000 rpm under sterilize temperatures at 120-140 °C for 15 min. The result showed that emulsion stability increase with increasing speed of homogenization. The lower fat particles were generated and easy to disperse in continuous phase lead to high stability. On the other hand, the stability of coconut milk decreased, fat globule increased, L value decreased and b value increased when the high sterilization temperature was applied. Homogenization after heating led to higher stability than homogenization before heating due to the reduced particle size of coconut milk after aggregation during sterilization process. The results implied that homogenization after sterilization process might play an important role on the quality of the sterilized coconut milk.

  2. Plane wave interaction with a homogeneous warm plasma sphere

    International Nuclear Information System (INIS)

    Ruppin, R.

    1975-01-01

    A Mie type theory for the scattering and absorption properties of a homogeneous warm plasma sphere is developed. The theory is applied to the calculation of the extinction cross section of plasma spheres, and the effects of Landau damping and collisional damping on the spectra are discussed. The dependence of the main resonance and of the Tonks-Dattner resonances on the physical parameters characterizing the sphere and its surroundings is investigated. The spectrum is shown to be insenitive to the boundary conditions which specify the behaviour of the electrons at the surface of the sphere (author)

  3. Fabrication of homogeneous titania/MWNT composite materials

    International Nuclear Information System (INIS)

    Korbely, Barbara; Nemeth, Zoltan; Reti, Balazs; Seo, Jin Won; Magrez, Arnaud; Forro, Laszlo; Hernadi, Klara

    2011-01-01

    Highlights: → Homogenous titania coverage on MWNT surface in a controllable way. → Various titanium alkoxy precursors are suitable for layer formation. → Acetone and ethanol are the best to promote interaction between MWNT and titania. -- Abstract: MWNT/titania nanocomposites were prepared by an impregnation method and subsequent heat treatment at 400 o C. Precursor compounds such as titanium (IV) propoxide and titanium (IV) ethoxide were used to cover the surface of CNTs under solution conditions. Electron microscopy and X-ray diffraction techniques were carried out to characterize the as-prepared titania layers.

  4. Decomposition of ammonium nitrate in homogeneous and catalytic denitration

    International Nuclear Information System (INIS)

    Anan'ev, A. V.; Tananaev, I. G.; Shilov, V. P.

    2005-01-01

    Ammonium nitrate is one of potentially explosive by-products of spent fuel reprocessing. Decomposition of ammonium nitrate in the HNO 3 -HCOOH system was studied in the presence or absence of Pt/SiO 2 catalyst. It was found that decomposition of ammonium nitrate is due to homogeneous noncatalytic oxidation of ammonium ion with nitrous acid generated in the HNO 3 -HCOOH system during denitration. The platinum catalyst initiates the reaction of HNO 3 with HCOOH to form HNO 2 . The regular trends were revealed and the optimal conditions of decomposition of ammonium nitrate in nitric acid solutions were found [ru

  5. Homogeneous approximation property for continuous shearlet transforms in higher dimensions

    Directory of Open Access Journals (Sweden)

    Yu Su

    2016-07-01

    Full Text Available Abstract This paper is concerned with the generalization of the homogeneous approximation property (HAP for a continuous shearlet transform to higher dimensions. First, we give a pointwise convergence result on the inverse shearlet transform in higher dimensions. Second, we show that every pair of admissible shearlets possess the HAP in the sense of L 2 ( R d $L^{2}(R^{d}$ . Third, we give a sufficient condition for the pointwise HAP to hold, which depends on both shearlets and functions to be reconstructed.

  6. Homogenized Elastic Properties of Graphene for Small Deformations

    Directory of Open Access Journals (Sweden)

    Jurica Sorić

    2013-09-01

    Full Text Available In this paper, we provide the quantification of the linear and non-linear elastic mechanical properties of graphene based upon the judicious combination of molecular mechanics simulation results and homogenization methods. We clarify the influence on computed results by the main model features, such as specimen size, chirality of microstructure, the effect of chosen boundary conditions (imposed displacement versus force and the corresponding plane stress transformation. The proposed approach is capable of explaining the scatter of the results for computed stresses, energy and stiffness and provides the bounds on graphene elastic properties, which are quite important in modeling and simulation of the virtual experiments on graphene-based devices.

  7. Ab initio molecular dynamics in a finite homogeneous electric field.

    Science.gov (United States)

    Umari, P; Pasquarello, Alfredo

    2002-10-07

    We treat homogeneous electric fields within density functional calculations with periodic boundary conditions. A nonlocal energy functional depending on the applied field is used within an ab initio molecular dynamics scheme. The reliability of the method is demonstrated in the case of bulk MgO for the Born effective charges, and the high- and low-frequency dielectric constants. We evaluate the static dielectric constant by performing a damped molecular dynamics in an electric field and avoiding the calculation of the dynamical matrix. Application of this method to vitreous silica shows good agreement with experiment and illustrates its potential for systems of large size.

  8. Exhaust gas recirculation in a homogeneous charge compression ignition engine

    Science.gov (United States)

    Duffy, Kevin P [Metamora, IL; Kieser, Andrew J [Morton, IL; Rodman, Anthony [Chillicothe, IL; Liechty, Michael P [Chillicothe, IL; Hergart, Carl-Anders [Peoria, IL; Hardy, William L [Peoria, IL

    2008-05-27

    A homogeneous charge compression ignition engine operates by injecting liquid fuel directly in a combustion chamber, and mixing the fuel with recirculated exhaust and fresh air through an auto ignition condition of the fuel. The engine includes at least one turbocharger for extracting energy from the engine exhaust and using that energy to boost intake pressure of recirculated exhaust gas and fresh air. Elevated proportions of exhaust gas recirculated to the engine are attained by throttling the fresh air inlet supply. These elevated exhaust gas recirculation rates allow the HCCI engine to be operated at higher speeds and loads rendering the HCCI engine a more viable alternative to a conventional diesel engine.

  9. Mineralogical and geochemical investigation of the Oligocene sedimentary series of Saint-Agoulin; Etude mineralogique et geochimique de la serie sedimentaire oligocene de Saint-Agoulin

    Energy Technology Data Exchange (ETDEWEB)

    Mohadjer, K [Commissariat a l' Energie Atomique, 92 - Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires, direction des productions; Faculte des Sciences de l' Universite de Paris, 75 (France)

    1967-07-05

    The mineralogical investigation is based on determination of the amounts of quartz, clays, feldspars and on grain size analysis. A distinction was established between two lithological groups: the lower group with dominant silica the upper with dominant carbonates. Clays of the two groups are comparable with dominant illite, and accessory kaolinite and montmorillonite. The amounts of the elements Si, Al, Fe, Ca, Mg, Na, K, Ti, Mn, P, Ba, Sr, Rb, Pb, Cu, Ni, Co, V, Be, B, Zr, U, were determined by several analytical methods: chemistry, X ray fluorescence, spectrography and fluorimetry. Correlations between the chemical elements and the mineralogical components were computed and plotted. Lastly the conditions of filling up of the basin are defined, taking into account the Oligocene climatic conditions. (author) [French] L'etude mineralogique est basee sur les dosages du quartz, de la calcite, des argiles, des feldspaths et sur les granulometries. On a distingue 2 familles lithologiques: l'une riche en quartz dans la partie inferieure, l'autre riche en carbonate dans la partie superieure. Les argiles des 2 familles sont comparables: illite predominante, kaolinite et montmorillonite accessoires. Les elements: Si, Al, Fe, Ca, Mg, Na, K, Ti, Mn, P, Ba, Sr, Rb, Pb, Cu, Ni, Co, V, Be, B, Zr, U, ont ete doses par differentes methodes d'analyse: analyse chimique, fluorescence X, spectrographie et fluorimetrie. Une etude de correlation entre les elements chimiques et les constituants mineralogiques a ete realisee. Enfin, les conditions de remplissage du Bassin sont definies, en tenant compte du contexte climatique oligocene. (auteur)

  10. Design of Stirrer Impeller with Variable Operational Speed for a Food Waste Homogenizer

    OpenAIRE

    Idris A. Kayode; Emmanuel O. B. Ogedengbe; Marc A. Rosen

    2016-01-01

    A conceptualized impeller called KIA is designed for impact agitation of food waste in a homogenizer. A comparative analysis of the performance of KIA is made with three conventional impeller types, Rushton, Anchor, and Pitched Blade. Solid–liquid mixing of a moisture-rich food waste is simulated under various operational speeds, in order to compare the dispersions and thermal distributions at homogenous slurry conditions. Using SolidWorks, the design of the impellers employs an Application P...

  11. Elastic waves trapped by a homogeneous anisotropic semicylinder

    Energy Technology Data Exchange (ETDEWEB)

    Nazarov, S A [Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, St.-Petersburg (Russian Federation)

    2013-11-30

    It is established that the problem of elastic oscillations of a homogeneous anisotropic semicylinder (console) with traction-free lateral surface (Neumann boundary condition) has no eigenvalues when the console is clamped at one end (Dirichlet boundary condition). If the end is free, under additional requirements of elastic and geometric symmetry, simple sufficient conditions are found for the existence of an eigenvalue embedded in the continuous spectrum and generating a trapped elastic wave, that is, one which decays at infinity at an exponential rate. The results are obtained by generalizing the methods developed for scalar problems, which however require substantial modification for the vector problem in elasticity theory. Examples are given and open questions are stated. Bibliography: 53 titles.

  12. Homogenized group cross sections by Monte Carlo

    International Nuclear Information System (INIS)

    Van Der Marck, S. C.; Kuijper, J. C.; Oppe, J.

    2006-01-01

    Homogenized group cross sections play a large role in making reactor calculations efficient. Because of this significance, many codes exist that can calculate these cross sections based on certain assumptions. However, the application to the High Flux Reactor (HFR) in Petten, the Netherlands, the limitations of such codes imply that the core calculations would become less accurate when using homogenized group cross sections (HGCS). Therefore we developed a method to calculate HGCS based on a Monte Carlo program, for which we chose MCNP. The implementation involves an addition to MCNP, and a set of small executables to perform suitable averaging after the MCNP run(s) have completed. Here we briefly describe the details of the method, and we report on two tests we performed to show the accuracy of the method and its implementation. By now, this method is routinely used in preparation of the cycle to cycle core calculations for HFR. (authors)

  13. Design of SC solenoid with high homogeneity

    International Nuclear Information System (INIS)

    Yang Xiaoliang; Liu Zhong; Luo Min; Luo Guangyao; Kang Qiang; Tan Jie; Wu Wei

    2014-01-01

    A novel kind of SC (superconducting) solenoid coil is designed to satisfy the homogeneity requirement of the magnetic field. In this paper, we first calculate the current density distribution of the solenoid coil section through the linear programming method. Then a traditional solenoid and a nonrectangular section solenoid are designed to produce a central field up to 7 T with a homogeneity to the greatest extent. After comparison of the two solenoid coils designed in magnet field quality, fabrication cost and other aspects, the new design of the nonrectangular section of a solenoid coil can be realized through improving the techniques of framework fabrication and winding. Finally, the outlook and error analysis of this kind of SC magnet coil are also discussed briefly. (authors)

  14. Core homogenization method for pebble bed reactors

    International Nuclear Information System (INIS)

    Kulik, V.; Sanchez, R.

    2005-01-01

    This work presents a core homogenization scheme for treating a stochastic pebble bed loading in pebble bed reactors. The reactor core is decomposed into macro-domains that contain several pebble types characterized by different degrees of burnup. A stochastic description is introduced to account for pebble-to-pebble and pebble-to-helium interactions within a macro-domain as well as for interactions between macro-domains. Performance of the proposed method is tested for the PROTEUS and ASTRA critical reactor facilities. Numerical simulations accomplished with the APOLLO2 transport lattice code show good agreement with the experimental data for the PROTEUS reactor facility and with the TRIPOLI4 Monte Carlo simulations for the ASTRA reactor configuration. The difference between the proposed method and the traditional volume-averaged homogenization technique is negligible while only one type of fuel pebbles present in the system, but it grows rapidly with the level of pebble heterogeneity. (authors)

  15. Smooth homogeneous structures in operator theory

    CERN Document Server

    Beltita, Daniel

    2005-01-01

    Geometric ideas and techniques play an important role in operator theory and the theory of operator algebras. Smooth Homogeneous Structures in Operator Theory builds the background needed to understand this circle of ideas and reports on recent developments in this fruitful field of research. Requiring only a moderate familiarity with functional analysis and general topology, the author begins with an introduction to infinite dimensional Lie theory with emphasis on the relationship between Lie groups and Lie algebras. A detailed examination of smooth homogeneous spaces follows. This study is illustrated by familiar examples from operator theory and develops methods that allow endowing such spaces with structures of complex manifolds. The final section of the book explores equivariant monotone operators and Kähler structures. It examines certain symmetry properties of abstract reproducing kernels and arrives at a very general version of the construction of restricted Grassmann manifolds from the theory of loo...

  16. Genetic homogeneity of Fascioloides magna in Austria.

    Science.gov (United States)

    Husch, Christian; Sattmann, Helmut; Hörweg, Christoph; Ursprung, Josef; Walochnik, Julia

    2017-08-30

    The large American liver fluke, Fascioloides magna, is an economically relevant parasite of both domestic and wild ungulates. F. magna was repeatedly introduced into Europe, for the first time already in the 19th century. In Austria, a stable population of F. magna has established in the Danube floodplain forests southeast of Vienna. The aim of this study was to determine the genetic diversity of F. magna in Austria. A total of 26 individuals from various regions within the known area of distribution were investigated for their cytochrome oxidase subunit 1 (cox1) and nicotinamide dehydrogenase subunit 1 (nad1) gene haplotypes. Interestingly, all 26 individuals revealed one and the same haplotype, namely concatenated haplotype Ha5. This indicates a homogenous population of F. magna in Austria and may argue for a single introduction. Alternatively, genetic homogeneity might also be explained by a bottleneck effect and/or genetic drift. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Shape optimization in biomimetics by homogenization modelling

    International Nuclear Information System (INIS)

    Hoppe, Ronald H.W.; Petrova, Svetozara I.

    2003-08-01

    Optimal shape design of microstructured materials has recently attracted a great deal of attention in material science. The shape and the topology of the microstructure have a significant impact on the macroscopic properties. The present work is devoted to the shape optimization of new biomorphic microcellular ceramics produced from natural wood by biotemplating. We are interested in finding the best material-and-shape combination in order to achieve the optimal prespecified performance of the composite material. The computation of the effective material properties is carried out using the homogenization method. Adaptive mesh-refinement technique based on the computation of recovered stresses is applied in the microstructure to find the homogenized elasticity coefficients. Numerical results show the reliability of the implemented a posteriori error estimator. (author)

  18. Homogenization of tissues via picosecond-infrared laser (PIRL) ablation: Giving a closer view on the in-vivo composition of protein species as compared to mechanical homogenization.

    Science.gov (United States)

    Kwiatkowski, M; Wurlitzer, M; Krutilin, A; Kiani, P; Nimer, R; Omidi, M; Mannaa, A; Bussmann, T; Bartkowiak, K; Kruber, S; Uschold, S; Steffen, P; Lübberstedt, J; Küpker, N; Petersen, H; Knecht, R; Hansen, N O; Zarrine-Afsar, A; Robertson, W D; Miller, R J D; Schlüter, H

    2016-02-16

    Posttranslational modifications and proteolytic processing regulate almost all physiological processes. Dysregulation can potentially result in pathologic protein species causing diseases. Thus, tissue species proteomes of diseased individuals provide diagnostic information. Since the composition of tissue proteomes can rapidly change during tissue homogenization by the action of enzymes released from their compartments, disease specific protein species patterns can vanish. Recently, we described a novel, ultrafast and soft method for cold vaporization of tissue via desorption by impulsive vibrational excitation (DIVE) using a picosecond-infrared-laser (PIRL). Given that DIVE extraction may provide improved access to the original composition of protein species in tissues, we compared the proteome composition of tissue protein homogenates after DIVE homogenization with conventional homogenizations. A higher number of intact protein species was observed in DIVE homogenates. Due to the ultrafast transfer of proteins from tissues via gas phase into frozen condensates of the aerosols, intact protein species were exposed to a lesser extent to enzymatic degradation reactions compared with conventional protein extraction. In addition, total yield of the number of proteins is higher in DIVE homogenates, because they are very homogenous and contain almost no insoluble particles, allowing direct analysis with subsequent analytical methods without the necessity of centrifugation. Enzymatic protein modifications during tissue homogenization are responsible for changes of the in-vivo protein species composition. Cold vaporization of tissues by PIRL-DIVE is comparable with taking a snapshot at the time of the laser irradiation of the dynamic changes that occur continuously under in-vivo conditions. At that time point all biomolecules are transferred into an aerosol, which is immediately frozen. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  19. Homogenization of variational inequalities for obstacle problems

    International Nuclear Information System (INIS)

    Sandrakov, G V

    2005-01-01

    Results on the convergence of solutions of variational inequalities for obstacle problems are proved. The variational inequalities are defined by a non-linear monotone operator of the second order with periodic rapidly oscillating coefficients and a sequence of functions characterizing the obstacles. Two-scale and macroscale (homogenized) limiting variational inequalities are obtained. Derivation methods for such inequalities are presented. Connections between the limiting variational inequalities and two-scale and macroscale minimization problems are established in the case of potential operators.

  20. Quantum groups and quantum homogeneous spaces

    International Nuclear Information System (INIS)

    Kulish, P.P.

    1994-01-01

    The usefulness of the R-matrix formalism and the reflection equations is demonstrated on examples of the quantum group covariant algebras (quantum homogeneous spaces): quantum Minkowski space-time, quantum sphere and super-sphere. The irreducible representations of some covariant algebras are constructed. The generalization of the reflection equation to super case is given and the existence of the quasiclassical limits is pointed out. (orig.)

  1. Process to produce homogenized reactor fuels

    International Nuclear Information System (INIS)

    Hart, P.E.; Daniel, J.L.; Brite, D.W.

    1980-01-01

    The fuels consist of a mixture of PuO 2 and UO 2 . In order to increase the homogeneity of mechanically mixed fuels the pellets are sintered in a hydrogen atmosphere with a sufficiently low oxygen potential. This results in a reduction of Pu +4 to Pu +3 . By the reduction process water vapor is obtained increasing the pressure within the PuO 2 particles and causing PuO 2 to be pressed into the uranium oxide structure. (DG) [de

  2. Homogeneous scintillating LKr/Xe calorimeters

    Energy Technology Data Exchange (ETDEWEB)

    Chen, M.; Mullins, M.; Pelly, D.; Shotkin, S.; Sumorok, K. (Lab. for Nuclear Science, MIT, Cambridge, MA (United States)); Akyuz, D.; Chen, E.; Gaudreau, M.P.J. (Plasma Fusion Center, MIT, Cambridge, MA (United States)); Bolozdynya, A.; Tchernyshev, V.; Goritchev, P.; Khovansky, V.; Koutchenkov, A.; Kovalenko, A.; Lebedenko, V.; Vinogradov, V.; Gusev, L.; Sheinkman, V. (ITEP, Moscow (Russia)); Krasnokutsky, R.N.; Shuvalov, R.S.; Fedyakin, N.N.; Sushkov, V. (IHEP, Serpukhov (Russia)); Akopyan, M. (Inst. for Nuclear Research, Moscow (Russia)); Doke, T.; Kikuchi, J.; Hitachi, A.; Kashiwagi, T. (Science and Eng. Res. Lab., Waseda Univ., Tokyo (Japan)); Masuda, K.; Shibamura, E. (Saitama Coll. of Health (Japan)); Ishida, N. (Seikei Univ. (Japan)); Sugimoto, S. (INS, Univ. Tokyo (Japan))

    1993-03-20

    Recent R and D work on full length scintillating homogeneous liquid xenon/krypton (LXe/Kr) cells has established the essential properties for precision EM calorimeters: In-situ calibration using [alpha]'s, radiation hardness as well as the uniformity required for [delta]E/E[approx equal]0.5% for e/[gamma]'s above 50 GeV. (orig.).

  3. Fluoroscopic screen which is optically homogeneous

    International Nuclear Information System (INIS)

    1975-01-01

    A high efficiency fluoroscopic screen for X-ray examination consists of an optically homogeneous crystal plate of fluorescent material such as activated cesium iodide, supported on a transparent protective plate, with the edges of the assembly beveled and optically coupled to a light absorbing compound. The product is dressed to the desired thickness and provided with an X-ray-transparent light-opaque cover. (Auth.)

  4. Correlated equilibria in homogenous good Bertrand competition

    DEFF Research Database (Denmark)

    Jann, Ole; Schottmüller, Christoph

    2015-01-01

    We show that there is a unique correlated equilibrium, identical to the unique Nash equilibrium, in the classic Bertrand oligopoly model with homogenous goods and identical marginal costs. This provides a theoretical underpinning for the so-called "Bertrand paradox'' as well as its most general f...... formulation to date. Our proof generalizes to asymmetric marginal costs and arbitrarily many players in the following way: The market price cannot be higher than the second lowest marginal cost in any correlated equilibrium....

  5. Homogeneous Biosensing Based on Magnetic Particle Labels

    KAUST Repository

    Schrittwieser, Stefan

    2016-06-06

    The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation.

  6. Some properties of spatially homogeneous spacetimes

    International Nuclear Information System (INIS)

    Coomer, G.C.

    1979-01-01

    This paper discusses two features of the universe which are influenced in a fundamental way by the spacetime geometry of the universe. The first is the growth of density fluctuations in the early stages of the evolution of the universe. The second is the propagation of electromagnetic radiation in the universe. A spatially homogeneous universe is assumed in both discussions. The gravitational instability theory of galaxy formation is investigated for a viscous fluid and for a charged, conducting fluid with a magnetic field added as a perturbation. It is found that the growth rate of density perturbations in both cases is lower than in the perfect fluid case. Spatially homogeneous but nonisotropic spacetimes are investigated next. Two perfect fluid solutions of Einstein's field equations are found which have spacelike hypersurfaces with Bianchi type II geometry. An expression for the spectrum of the cosmic microwave background radiation in a spatially homogeneous but nonisotropic universe is found. The expression is then used to determine the angular distribution of the intensity of the radiation in the simpler of the two solutions. When accepted values of the matter density and decoupling temperature are inserted into this solution, values for the age of the universe and the time of decoupling are obtained which agree reasonably well with the values of the standard model of the universe

  7. Commensurability effects in holographic homogeneous lattices

    International Nuclear Information System (INIS)

    Andrade, Tomas; Krikun, Alexander

    2016-01-01

    An interesting application of the gauge/gravity duality to condensed matter physics is the description of a lattice via breaking translational invariance on the gravity side. By making use of global symmetries, it is possible to do so without scarifying homogeneity of the pertinent bulk solutions, which we thus term as “homogeneous holographic lattices.' Due to their technical simplicity, these configurations have received a great deal of attention in the last few years and have been shown to correctly describe momentum relaxation and hence (finite) DC conductivities. However, it is not clear whether they are able to capture other lattice effects which are of interest in condensed matter. In this paper we investigate this question focusing our attention on the phenomenon of commensurability, which arises when the lattice scale is tuned to be equal to (an integer multiple of) another momentum scale in the system. We do so by studying the formation of spatially modulated phases in various models of homogeneous holographic lattices. Our results indicate that the onset of the instability is controlled by the near horizon geometry, which for insulating solutions does carry information about the lattice. However, we observe no sharp connection between the characteristic momentum of the broken phase and the lattice pitch, which calls into question the applicability of these models to the physics of commensurability.

  8. Homogeneous Biosensing Based on Magnetic Particle Labels

    Science.gov (United States)

    Schrittwieser, Stefan; Pelaz, Beatriz; Parak, Wolfgang J.; Lentijo-Mozo, Sergio; Soulantica, Katerina; Dieckhoff, Jan; Ludwig, Frank; Guenther, Annegret; Tschöpe, Andreas; Schotter, Joerg

    2016-01-01

    The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation. PMID:27275824

  9. Homogeneous Biosensing Based on Magnetic Particle Labels

    KAUST Repository

    Schrittwieser, Stefan; Pelaz, Beatriz; Parak, Wolfgang; Lentijo Mozo, Sergio; Soulantica, Katerina; Dieckhoff, Jan; Ludwig, Frank; Guenther, Annegret; Tschö pe, Andreas; Schotter, Joerg

    2016-01-01

    The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation.

  10. Testing Homogeneity with the Galaxy Fossil Record

    CERN Document Server

    Hoyle, Ben; Jimenez, Raul; Heavens, Alan; Clarkson, Chris; Maartens, Roy

    2013-01-01

    Observationally confirming spatial homogeneity on sufficiently large cosmological scales is of importance to test one of the underpinning assumptions of cosmology, and is also imperative for correctly interpreting dark energy. A challenging aspect of this is that homogeneity must be probed inside our past lightcone, while observations take place on the lightcone. The history of star formation rates (SFH) in the galaxy fossil record provides a novel way to do this. We calculate the SFH of stacked Luminous Red Galaxy (LRG) spectra obtained from the Sloan Digital Sky Survey. We divide the LRG sample into 12 equal area contiguous sky patches and 10 redshift slices (0.2homogeneity, we calculate the posterior distribution for the excess large-scale variance due to inhomogeneity, and find that the most likely solution is n...

  11. Influence of surface conditions on fatigue strength through the numerical simulation of microstructure; Etude par simulation numerique de la microstructure de l'influence de l'etat de surface sur la resistance a la fatigue d'un acier 304L

    Energy Technology Data Exchange (ETDEWEB)

    Le Pecheur, A.; Clavel, M.; Rey, C.; Bompard, P. [Laboratoire MSSMat, UMR 8579 CNRS, Ecole Centrale Paris (France); Le Pecheur, A.; Curtit, F.; Stephan, J.M. [Departement MMC, EDF RD, Site des Renardieres (France)

    2010-11-15

    A thermal fatigue test (INTHERPOL) was developed by EDF in order to study the initiation of cracks. These tests are carried out on tubular specimens under various thermal loadings and surface finish qualities in order to give an account of these parameters on crack initiation. The main topic of this study is to test the sensitivity of different fatigue criteria to surface conditions using a micro/macro modelling approach. Therefore a 304L polycrystalline aggregate, used for cyclic plasticity based FE modelling, have been considered as a Representative Volume Element located at the surface and subsurface of the test tube. This aggregate has been cyclically strained according to the results issued from FE simulation of INTHERPOL thermal fatigue experiment. Different surface parameters have been numerically simulated: effects of local microstructure and of grains orientation, effects of machining: metallurgical prehardening, residual stress gradient, and surface roughness. Three different fatigue criteria (Manson Coffin, Fatemi Socie and dissipated energy types), previously fitted at a macro-scale for thermal fatigue of 304L, have been computed at a meso scale, in order to show the surface 'hot spots' features and test the sensitivity of these three criteria to different surface conditions. Results show that grain orientation and neighbouring play an important role on the location of hot spots, and also that the positive effect of pre-straining and the negative effect of roughness on fatigue life are not all similarly predicted by these different fatigue criteria. (authors)

  12. Sewage sludge disintegration by combined treatment of alkaline+high pressure homogenization.

    Science.gov (United States)

    Zhang, Yuxuan; Zhang, Panyue; Zhang, Guangming; Ma, Weifang; Wu, Hao; Ma, Boqiang

    2012-11-01

    Alkaline pretreatment combined with high pressure homogenization (HPH) was applied to promote sewage sludge disintegration. For sewage sludge with a total solid content of 1.82%, sludge disintegration degree (DD(COD)) with combined treatment was higher than the sum of DD(COD) with single alkaline and single HPH treatment. NaOH dosage ⩽0.04mol/L, homogenization pressure ⩽60MPa and a single homogenization cycle were the suitable conditions for combined sludge treatment. The combined sludge treatment showed a maximum DD(COD) of 59.26%. By regression analysis, the combined sludge disintegration model was established as 11-DD(COD)=0.713C(0.334)P(0.234)N(0.119), showing that the effect of operating parameters on sludge disintegration followed the order: NaOH dosage>homogenization pressure>number of homogenization cycle. The energy efficiency with combined sludge treatment significantly increased compared with that with single HPH treatment, and the high energy efficiency was achieved at low homogenization pressure with a single homogenization cycle. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Pegase: safety studies - experimental study of burn-out risks in transient operation; Pegase: etude de surete - etude experimentale des risques de burn out en regime transitoire

    Energy Technology Data Exchange (ETDEWEB)

    Vernier, P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1968-07-01

    An experiment out-of-pile experimental set up is proposed simulating the breakage of a pipe supplying the core of the reactor Pegase. The two fast phenomena, depressurization of the vessel and flow reversal, are reproduced. The aluminium heating channel has the same shape as that of the reactor channel but has twice the heat capacity. The starting conditions are V= 4.50 and 6 m/sec., T{sub E} = 50 and 60 degrees C and P{sub E} = 4 bars. The results show that the critical flux PHI{sub C} varies with the flow-rate from 45 to 60 W/cm{sup 2} in the case where there is no power reduction. For fluxes of 90 W/cm{sup 2} the results lead to the conclusion that the hot channel attains a state of burn-out after 0.1 sec. and that its temperature reaches 500 C in 0.8 sec. The hydrodynamic conditions in the channels after the accident involve periodic expulsion (0.2 to 0.5 sec.), characteristic of boiling at low pressure. A study of the steady state flow redistribution through a by-pass has given flux redistribution PHI{sub R} of 190 W/cm{sup 2} for a flow rate of 4.5 m/sec. at 50 and of 175 W/cm{sup 2} at 60 C. These values increase which has to be made between the critical flux PHI{sub C} during the periodic expulsion conditions and the flux redistribution PHI{sub R} during the steady state, has been shown. (author) [French] On propose un schema experimental hors pile d'une rupture du tuyau alimentant le coeur du reacteur PEGASE. On reproduit les phenomenes rapides de depressurisation du caisson et d'inversion du debit dans le coeur. Le canal chauffant en aluminium a la meme geometrie que le canal du reacteur, mais une capacite calorifique double. Les conditions initiales sont V= 4.5 et 6 m/s, T{sub E} = 50 et 60 C et P{sub E} = 4 bars. Les resultats montrent que le flux critique PHI{sub C} evolue avec la vitesse de 45 a 60 60 W/cm{sup 2} dans le cas ou il n'y a pas reduction de puissance. Pour des flux de 90 W/cm{sup 2} l'interpretation des resultats permet de conclure que le

  14. Reactive-inspired ball-milling synthesis of an ODS steel: study of the influence of ball-milling and annealing; Synthese et caracterisation d'un acier ODS prepare par un procede inspiredu broyage reactif: etude de l'influence des conditions de broyage et recuit

    Energy Technology Data Exchange (ETDEWEB)

    Brocq, M.

    2010-10-15

    In the context of the development of new ODS (Oxide Dispersion Strengthened) steels as core materials in future nuclear reactors, we investigated a new process inspired by reactive ball-milling which consists in using YFe{sub 3} andFe{sub 2}O{sub 3} as starting reactants instead of Y{sub 2}O{sub 3} to produce a dispersion of nano-oxides in a steel matrix and the influence of synthesis conditions on the nano-oxide characteristics were studied. For that aim, ODS steels were prepared by ball-milling and then annealed. Multi-scale characterizations were performed after each synthesis step, using notably atom probe tomography and small angle neutron scattering. The process inspired by reactive ball-milling was shown to be efficient for ODS steel synthesis, but it does not modify the nano-oxide characteristics as compared to those of oxides directly incorporated in the matrix by ball-milling. Broadly speaking, the nature of the starting oxygen bearing reactants has no influence on nano-oxide formation. Moreover, we showed that the nucleation of nano-oxides nucleation can start during milling and continues during annealing with a very fast kinetic. The final characteristics of nano-oxides formed in this way can be monitored through ball-milling parameters (intensity, temperature and atmosphere) and annealing parameters (duration and temperature). (author)

  15. Dark energy homogeneity in general relativity: Are we applying it correctly?

    Science.gov (United States)

    Duniya, Didam G. A.

    2016-04-01

    Thus far, there does not appear to be an agreed (or adequate) definition of homogeneous dark energy (DE). This paper seeks to define a valid, adequate homogeneity condition for DE. Firstly, it is shown that as long as w_x ≠ -1, DE must have perturbations. It is then argued, independent of w_x, that a correct definition of homogeneous DE is one whose density perturbation vanishes in comoving gauge: and hence, in the DE rest frame. Using phenomenological DE, the consequence of this approach is then investigated in the observed galaxy power spectrum—with the power spectrum being normalized on small scales, at the present epoch z=0. It is found that for high magnification bias, relativistic corrections in the galaxy power spectrum are able to distinguish the concordance model from both a homogeneous DE and a clustering DE—on super-horizon scales.

  16. Homogenization of some radiative heat transfer models: application to gas-cooled reactor cores

    International Nuclear Information System (INIS)

    El Ganaoui, K.

    2006-09-01

    In the context of homogenization theory we treat some heat transfer problems involving unusual (according to the homogenization) boundary conditions. These problems are defined in a solid periodic perforated domain where two scales (macroscopic and microscopic) are to be taken into account and describe heat transfer by conduction in the solid and by radiation on the wall of each hole. Two kinds of radiation are considered: radiation in an infinite medium (non-linear problem) and radiation in cavity with grey-diffuse walls (non-linear and non-local problem). The derived homogenized models are conduction problems with an effective conductivity which depend on the considered radiation. Thus we introduce a framework (homogenization and validation) based on mathematical justification using the two-scale convergence method and numerical validation by simulations using the computer code CAST3M. This study, performed for gas cooled reactors cores, can be extended to other perforated domains involving the considered heat transfer phenomena. (author)

  17. Cold storage in a two-phases fluid for air-conditioning and/or industrial processes - Feasibility study; Stockage de froid par fluide diphasique pour transport et distribution du froid, pour la climatisation et/ou processus industriels. Etude de faisabilite II - Rapport

    Energy Technology Data Exchange (ETDEWEB)

    Hu, J.; Sari, O.; Brun, F.; Eicher, S.

    2008-07-01

    In the present report, 2 large-scale continuous CO{sub 2} hydrate formation-dissociation conditions were experimentally investigated on a fully functional laboratory demonstrator for industrial applications. The solid fraction of CO{sub 2} hydrate slurry was evaluated by a numerical approach based on a CO{sub 2} mass balance. A first CO{sub 2} hydrate slurry production system with compressor was tested. In this system the CO{sub 2} hydrate slurry formation and dissociation pressure, temperature, density and dynamic viscosity were measured. The consumption of CO{sub 2} hydrate slurry in the consumer installed in the climatic room was successful. The continuous formation and dissociation processes in this loop were not very successful. A second experimental loop for hydrate production without compressor was completed. The new test rig is an industrial prototype approach. The new test rig is simple, easy to be modified and adapted to new devices. The Axima heat exchanger was modified and is being used for hydrate slurry production. Kenics mixing elements and Sulzer SMV gas mixers were tested in the loop. Experimental results showed that the mixing elements and gas mixers can promote hydrate formation. CO{sub 2} hydrate slurry density was measured with a value of 1032 kg/m{sup 3} which corresponds to over 30% solid fraction (150 kJ/kg dissociation enthalpy of water). The power of the pump was tested and it was showed that it is not sufficient to pump CO{sub 2} hydrate slurry when the density is over 1030 kg/m{sup 3}. The specific heat of water and of ice, the enthalpy of ice and of CO{sub 2} hydrates were obtained using a differential scanning calorimetry, Micro DSCVII. It confirmed that CO{sub 2} dissolved in water depresses the freezing point of water. On-line measurements of corrosion rates were performed and reliable results obtained. (author)

  18. Investigation of methods for hydroclimatic data homogenization

    Science.gov (United States)

    Steirou, E.; Koutsoyiannis, D.

    2012-04-01

    We investigate the methods used for the adjustment of inhomogeneities of temperature time series covering the last 100 years. Based on a systematic study of scientific literature, we classify and evaluate the observed inhomogeneities in historical and modern time series, as well as their adjustment methods. It turns out that these methods are mainly statistical, not well justified by experiments and are rarely supported by metadata. In many of the cases studied the proposed corrections are not even statistically significant. From the global database GHCN-Monthly Version 2, we examine all stations containing both raw and adjusted data that satisfy certain criteria of continuity and distribution over the globe. In the United States of America, because of the large number of available stations, stations were chosen after a suitable sampling. In total we analyzed 181 stations globally. For these stations we calculated the differences between the adjusted and non-adjusted linear 100-year trends. It was found that in the two thirds of the cases, the homogenization procedure increased the positive or decreased the negative temperature trends. One of the most common homogenization methods, 'SNHT for single shifts', was applied to synthetic time series with selected statistical characteristics, occasionally with offsets. The method was satisfactory when applied to independent data normally distributed, but not in data with long-term persistence. The above results cast some doubts in the use of homogenization procedures and tend to indicate that the global temperature increase during the last century is between 0.4°C and 0.7°C, where these two values are the estimates derived from raw and adjusted data, respectively.

  19. Two-scale homogenization to determine effective parameters of thin metallic-structured films

    Science.gov (United States)

    Marigo, Jean-Jacques

    2016-01-01

    We present a homogenization method based on matched asymptotic expansion technique to derive effective transmission conditions of thin structured films. The method leads unambiguously to effective parameters of the interface which define jump conditions or boundary conditions at an equivalent zero thickness interface. The homogenized interface model is presented in the context of electromagnetic waves for metallic inclusions associated with Neumann or Dirichlet boundary conditions for transverse electric or transverse magnetic wave polarization. By comparison with full-wave simulations, the model is shown to be valid for thin interfaces up to thicknesses close to the wavelength. We also compare our effective conditions with the two-sided impedance conditions obtained in transmission line theory and to the so-called generalized sheet transition conditions. PMID:27616916

  20. Diffusion piecewise homogenization via flux discontinuity factors

    International Nuclear Information System (INIS)

    Sanchez, Richard; Zmijarevic, Igor

    2011-01-01

    We analyze the calculation of flux discontinuity factors (FDFs) for use with piecewise subdomain assembly homogenization. These coefficients depend on the numerical mesh used to compute the diffusion problem. When the mesh has a single degree of freedom on subdomain interfaces the solution is unique and can be computed independently per subdomain. For all other cases we have implemented an iterative calculation for the FDFs. Our numerical results show that there is no solution to this nonlinear problem but that the iterative algorithm converges towards FDFs values that reproduce subdomains reaction rates with a relatively high precision. In our test we have included both the GET and black-box FDFs. (author)

  1. Tensor harmonic analysis on homogenous space

    International Nuclear Information System (INIS)

    Wrobel, G.

    1997-01-01

    The Hilbert space of tensor functions on a homogenous space with the compact stability group is considered. The functions are decomposed onto a sum of tensor plane waves (defined in the text), components of which are transformed by irreducible representations of the appropriate transformation group. The orthogonality relation and the completeness relation for tensor plane waves are found. The decomposition constitutes a unitary transformation, which allows to obtain the Parseval equality. The Fourier components can be calculated by means of the Fourier transformation, the form of which is given explicitly. (author)

  2. Multifractal spectra in homogeneous shear flow

    Science.gov (United States)

    Deane, A. E.; Keefe, L. R.

    1988-01-01

    Employing numerical simulations of 3-D homogeneous shear flow, the associated multifractal spectra of the energy dissipation, scalar dissipation and vorticity fields were calculated. The results for (128) cubed simulations of this flow, and those obtained in recent experiments that analyzed 1- and 2-D intersections of atmospheric and laboratory flows, are in some agreement. A two-scale Cantor set model of the energy cascade process which describes the experimental results from 1-D intersections quite well, describes the 3-D results only marginally.

  3. Magnetic resonance studies of solid polymers; Etude des polymeres solides par resonance magnetique

    Energy Technology Data Exchange (ETDEWEB)

    Lenk, R [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    This paper is a review of the application of nuclear magnetic resonance (NMR) to solid polymers. In the first, theoretical part, the elements of the theory of NMR, which are necessary for the study of the properties of solid polymers are discussed: the moments method, nuclear relaxation and the distribution of correlation times. In the second part the experimental results are presented. (author) [French] Cette etude est une recherche bibliographique sur l'application de la resonance magnetique nucleaire (RMN) aux polymeres solides. Dans la premiere partie theorique on discute les elements de la theorie de RMN, necessaires pour l'etude des proprietes des polymeres solides: la methode des moments, la relaxation nucleaire et la distribution des temps de correlation. La deuxieme partie presente les resultats des experiences. (auteur)

  4. The study of some thiazinic and indaminic dye syntheses induced by ionising radiation; Etude de quelques syntheses de colorants thianziniques et indaminiques amorcees par les rayonnements ionisants

    Energy Technology Data Exchange (ETDEWEB)

    Balestic, S [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-03-15

    With a view to finding some radiochemical reactions applicable on an industrial scale for evaluating the radioactive waste from nuclear reactors, a systematic study was made of the radiochemical synthesis of thiazinic dyes such as methylene blue and Lauths' violet, on which the first tests were carried out in 1954. The first part of the study concerned the identification and the dosage, during radiolysis, of dyes by means of their absorption spectra after separation from the reaction medium by adsorption chromatography or ion-exchange; other radiolysis products such as ammonium chloride and hydrogen peroxide were also identified. During a later stage by systematically varying the physico-chemical parameters it was possible to determine the most favourable conditions for radio-synthesis; the maximum radiochemical yields obtained had the following values: G (Lauths' violet) 1,65; G (Methylene blue) = 1,75. Furthermore, the study of the influence of variously substituted aminated products on the radiochemical yield showed the possibility of synthesising Bindsehedlers green and Wursters blue by radiochemical methods. Finally the discovery of a fundamental intermediate product, Wursters red, together with the kinetic study of the chemical synthesis of methylene blue made it possible to determine the main stages of the reaction mechanism and to decide which of these stages could be attributed to ionising radiations in the case of the radiochemical synthesis. (author) [French] Dans le but de trouver des reactions radiochimiques susceptibles d'une application industrielle pour valoriser les dechets radioactifs provenant des reacteurs nucleaires, il a ete entrepris une etude systematique de la synthese radiochimique des colorants thiazimiques tels que le Bleu de Methylene et le Violet de Lauth dont les premiers essais ont ete effectues par Loiseleur en 1954. La premiere partie de l'etude a porte sur l'identification et le dosage des colorants formes au cours de la radiolyse

  5. Homogenization of Doppler broadening in spin-noise spectroscopy

    Science.gov (United States)

    Petrov, M. Yu.; Ryzhov, I. I.; Smirnov, D. S.; Belyaev, L. Yu.; Potekhin, R. A.; Glazov, M. M.; Kulyasov, V. N.; Kozlov, G. G.; Aleksandrov, E. B.; Zapasskii, V. S.

    2018-03-01

    The spin-noise spectroscopy, being a nonperturbative linear optics tool, is still reputed to reveal a number of capabilities specific to nonlinear optics techniques. The effect of the Doppler broadening homogenization discovered in this work essentially widens these unique properties of spin-noise spectroscopy. We investigate spin noise of a classical system—cesium atoms vapor with admixture of buffer gas—by measuring the spin-induced Faraday rotation fluctuations in the region of D 2 line. The line, under our experimental conditions, is strongly inhomogeneously broadened due to the Doppler effect. Despite that, optical spectrum of the spin-noise power has the shape typical for the homogeneously broadened line with a dip at the line center. This fact is in stark contrast with the results of previous studies of inhomogeneous quantum dot ensembles and Doppler broadened atomic systems. In addition, the two-color spin-noise measurements have shown, in a highly spectacular way, that fluctuations of the Faraday rotation within the line are either correlated or anticorrelated depending on whether the two wavelengths lie on the same side or on different sides of the resonance. The experimental data are interpreted in the frame of the developed theoretical model which takes into account both kinetics and spin dynamics of Cs atoms. It is shown that the unexpected behavior of the Faraday rotation noise spectra and effective homogenization of the optical transition in the spin-noise measurements are related to smallness of the momentum relaxation time of the atoms as compared with their spin-relaxation time. Our findings demonstrate abilities of spin-noise spectroscopy for studying dynamic properties of inhomogeneously broadened ensembles of randomly moving spins.

  6. Stimulus homogeneity enhances implicit learning: evidence from contextual cueing.

    Science.gov (United States)

    Feldmann-Wüstefeld, Tobias; Schubö, Anna

    2014-04-01

    Visual search for a target object is faster if the target is embedded in a repeatedly presented invariant configuration of distractors ('contextual cueing'). It has also been shown that the homogeneity of a context affects the efficiency of visual search: targets receive prioritized processing when presented in a homogeneous context compared to a heterogeneous context, presumably due to grouping processes at early stages of visual processing. The present study investigated in three Experiments whether context homogeneity also affects contextual cueing. In Experiment 1, context homogeneity varied on three levels of the task-relevant dimension (orientation) and contextual cueing was most pronounced for context configurations with high orientation homogeneity. When context homogeneity varied on three levels of the task-irrelevant dimension (color) and orientation homogeneity was fixed, no modulation of contextual cueing was observed: high orientation homogeneity led to large contextual cueing effects (Experiment 2) and low orientation homogeneity led to low contextual cueing effects (Experiment 3), irrespective of color homogeneity. Enhanced contextual cueing for homogeneous context configurations suggest that grouping processes do not only affect visual search but also implicit learning. We conclude that memory representation of context configurations are more easily acquired when context configurations can be processed as larger, grouped perceptual units. However, this form of implicit perceptual learning is only improved by stimulus homogeneity when stimulus homogeneity facilitates grouping processes on a dimension that is currently relevant in the task. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Contribution to the study of recoil species produced by potassium ferrocyanide neutron irradiation; Contribution a l'etude de la reactivite des especes de recul dans le ferrocyanure de potassium irradie aux neutrons thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Meriadec Vernier de Byans, B. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-04-01

    The chemical species produced by potassium ferrocyanide neutron irradiation were separated and identified. The study of their behaviour upon thermal annealing has allowed to establish a scheme of reaction as well as a kinetic treatment of the data. Activation energies are determined in different conditions and the effects of radiation dose, oxygen and water of crystallisation upon the activation energies were studied. Preliminary E.S.R. data and its relevance to the decomposition process is also discussed. (authors) [French] On a separe et identifie les differentes especes chimiques produites par irradiation neutronique de ferrocyanure de potassium. L'etude de leur comportement au cours du recuit thermique a permis l'application de differentes cinetiques et l'etablissement d'un schema de reaction. On a deterrmine la valeur des energies d'activation dans differentes conditions de recuit ainsi que l'influence de la dose de radiations, de l'oxygene et de l'eau de cristallisation sur ces energies. Une serie de mesures de resonance paramagnetique electronique a complete cette etude. (auteurs)

  8. Contribution to the study of gas and liquid transfers inside damaged concrete walls under thermo-hydric stress: application to confinement buildings in test and accidental conditions; Contribution a l'etude des transferts gazeux et liquide au sein des parois en beton endommagees sous sollicitation thermo-hydrique: application au cas des enceintes de confinement en conditions d'epreuve et accidentelle

    Energy Technology Data Exchange (ETDEWEB)

    Laghcha, A

    2006-07-15

    The aim of this work is the study of fluid transfers induced by two types of stresses (test of tightness and LOCA-type accident), inside a concrete wall integrating the inhomogeneities and singularities susceptible to be present inside the confinement building of a nuclear reactor. After the study of several types of concretes, based on the permeabilities and types of gas flows involved, the experimental phase has permitted to test at scale 1 (1.3 m thickness) and in test and accidental conditions, a concrete composition which fulfills a representativeness criterion. The modeling part has been carried out using the thermo-hydro-mechanical model of non-saturated porous media, recently embedded inside the Code-Aster of EDF. The synthesis of physical observations and of numerical simulations has permitted to better constrain the different roles of the porous structure, in particular about the transposition between a air flow and a air + steam flow. (J.S.)

  9. Primary healthcare solo practices: homogeneous or heterogeneous?

    Science.gov (United States)

    Pineault, Raynald; Borgès Da Silva, Roxane; Provost, Sylvie; Beaulieu, Marie-Dominique; Boivin, Antoine; Couture, Audrey; Prud'homme, Alexandre

    2014-01-01

    Introduction. Solo practices have generally been viewed as forming a homogeneous group. However, they may differ on many characteristics. The objective of this paper is to identify different forms of solo practice and to determine the extent to which they are associated with patient experience of care. Methods. Two surveys were carried out in two regions of Quebec in 2010: a telephone survey of 9180 respondents from the general population and a postal survey of 606 primary healthcare (PHC) practices. Data from the two surveys were linked through the respondent's usual source of care. A taxonomy of solo practices was constructed (n = 213), using cluster analysis techniques. Bivariate and multilevel analyses were used to determine the relationship of the taxonomy with patient experience of care. Results. Four models were derived from the taxonomy. Practices in the "resourceful networked" model contrast with those of the "resourceless isolated" model to the extent that the experience of care reported by their patients is more favorable. Conclusion. Solo practice is not a homogeneous group. The four models identified have different organizational features and their patients' experience of care also differs. Some models seem to offer a better organizational potential in the context of current reforms.

  10. Irregular Homogeneity Domains in Ternary Intermetallic Systems

    Directory of Open Access Journals (Sweden)

    Jean-Marc Joubert

    2015-12-01

    Full Text Available Ternary intermetallic A–B–C systems sometimes have unexpected behaviors. The present paper examines situations in which there is a tendency to simultaneously form the compounds ABx, ACx and BCx with the same crystal structure. This causes irregular shapes of the phase homogeneity domains and, from a structural point of view, a complete reversal of site occupancies for the B atom when crossing the homogeneity domain. This work reviews previous studies done in the systems Fe–Nb–Zr, Hf–Mo–Re, Hf–Re–W, Mo–Re–Zr, Re–W–Zr, Cr–Mn–Si, Cr–Mo–Re, and Mo–Ni–Re, and involving the topologically close-packed Laves, χ and σ phases. These systems have been studied using ternary isothermal section determination, DFT calculations, site occupancy measurement using joint X-ray, and neutron diffraction Rietveld refinement. Conclusions are drawn concerning this phenomenon. The paper also reports new experimental or calculated data on Co–Cr–Re and Fe–Nb–Zr systems.

  11. WHAMP - waves in homogeneous, anisotropic, multicomponent plasmas

    International Nuclear Information System (INIS)

    Roennmark, K.

    1982-06-01

    In this report, a computer program which solves the dispersion relation of waves in a magnetized plasma is described. The dielectric tensor is derived using the kinetic theory of homogeneous plasmas with Maxwellian velocity distribution. Up to six different plasma components can be included in this version of the program, and each component is specified by its density, temperature, particle mass, anisotropy and drift velocity along the magnetic field. The program is thus applicable to a very wide class of plasmas, and the method should in general be useful whenever a homogeneous magnetized plasma can be approximated by a linear combination of Maxwellian components. The general theory underlying the program is outlined. It is shown that by introducing a Pade approximant for the plasma dispersion function Z, the infinite sums of modified Bessel functions which appear in the dielectric tensor may be reduced to a summable form. The Pade approximant is derived and the accuracy of the approximation is also discussed. The subroutines making up the program are described. (Author)

  12. Physical study of the 'snow flake' version of the reactor EL-3 (1963); Etude physique de la version ''cristal de neige'' de la pile EL-3 (1963)

    Energy Technology Data Exchange (ETDEWEB)

    Abillon, E; Genthon, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1963-07-01

    A systematic study has been made of the different thermodynamic and neutronic aspects of various versions of the 'snow flake' likely to fulfil the aims which were set out (improvement of the reactivity, of the experimental volume, improvement in the working conditions of EL-3). After this systematic study, a choice was made in principle of one version amongst the several available (solutions using 8 or 10 pencils-various methods of heat transfer: corrugation, cartridges which may or may not be filled with helium... etc., variable enrichments... ). The choice is that of a version which can already at the present be considered as feasible, which represents already a notable improvement of the pile and which does not imply the existence of a major problem as far as the possible change-over later to an improved version is concerned. This choice defines a fuel element and a configuration for the core. A detailed recapitulation has been made of all the research being carried out for the possible solutions in this particular case. (authors) [French] On a etudie systematiquement les differents aspects thermodynamiques et neutroniques de diverses versions 'cristal de neige' susceptibles de remplir les buts fixes (amelioration en reactivite, en volume experimental, amelioration des problemes d'exploitation de EL-3). Apres cette etude systematique, on a procede au choix de principe d'une version parmi les differentes solutions possibles (solutions a 8 ou 10 crayons - possibilite de transfert de chaleur divers: corrugations, cartouches remplies He ou non.... etc., enrichissements variables... ). Ce choix est celui d'une version qu'on peut juger viable des aujourd'hui, qui represente deja une amelioration importante de la pile et qui n'implique pas de probleme majeur quant au passage ulterieur et eventuel a une version plus amelioree. Ce choix definit un element combustible, et une configuration de coeur. On a recapitule et detaille sur ce cas particulier de pile les etudes

  13. Reflection principle for classical solutions of the homogeneous real Monge–Ampère equation

    Directory of Open Access Journals (Sweden)

    Mika Koskenoja

    2015-12-01

    Full Text Available We consider reflection principle for classical solutions of the homogeneous real Monge–Ampère equation. We show that both the odd and the even reflected functions satisfy the Monge–Ampère equation if the second-order partial derivatives have continuous limits on the reflection boundary. In addition to sufficient conditions, we give some necessary conditions. Before stating the main results, we present elementary formulas for the reflected functions and study their differentiability properties across the reflection boundary. As an important special case, we finally consider extension of polynomials satisfying the homogeneous Monge–Ampère equation.

  14. Homogeneity of nuclear fuel containing burnable poison; Homogenost jedrskega goriva z gorljivim strupom

    Energy Technology Data Exchange (ETDEWEB)

    Loose, A; Susnik, D; Ilic, R [Institut Jozef Stefan, Ljubljana (Yugoslavia)

    1988-07-01

    In this work the results of the microstructural investigations of the influence of the Gd{sub 2}O{sub 3} contents and the sintering conditions on the formation of the homogeneous (U,Gd)O{sub 2} solid solution, are presented. For this purpose sintering conditions, microstructure and diffusivity in UO{sub 2} -Gd{sub 2}O{sub 3} , were studied. It was found that, with a suitable preparation of powders and longer sintering times in dry hydrogen atmosphere above 1700 deg C, a homogeneous (U,Gd)O{sub 2} solid solution can be obtained. (author)

  15. Singing as a Therapeutic Agent, inThe Etude, 1891-1949.

    Science.gov (United States)

    Hunter

    1999-01-01

    The Etude music magazine, founded by Theodore Presser, was one of a number of popular music magazines published in the years prior to the establishment of the music therapy profession in 1950. During its publication run from 1883 to 1957, over 100 music therapy related articles appeared, including 13 on the health benefits of singing published between 1891 and 1949. Written by authors with diverse backgrounds, such as the famous Battle Creek, Michigan physician John Harvey Kellogg and Boston music critic Louis C. Elson, the articles contained consistent and adamant support regarding the health benefits of singing. The advantages described were both physical and psychological, and were recommended prophylactically for well persons and therapeutically for ill persons. Although the articles varied in perspective, from philosophical to theoretical to pedagogical, there is a consistent holistic medicine theme that appeared almost ahead of its time and no doubt linked to the push for vocal music education in that era. The importance of The Etude in promulgating ideas that helped shape the early practice of music therapy should not be underestimated. For much of its publication run The Etude was the largest music periodical in print, reaching its peak circulation of 250,000 copies per month in 1924.

  16. Radiotracer investigation of cement raw meal homogenizers. Pt. 2

    International Nuclear Information System (INIS)

    Baranyai, L.

    1983-01-01

    Based on radioisotopic tracer technique a method has been worked out to study the homogenization and segregation processes of cement-industrial raw meal homogenizers. On-site measurements were carried out by this method in some Hungarian cement works to determine the optimal homogenization parameters of operating homogenizers. The motion and distribution of different raw meal fractions traced with 198 Au radioisotope was studied in homogenization processes proceeding with different parameters. In the first part of the publication the change of charge homogenity in time was discussed which had been measured as the resultant of mixing and separating processes. In the second part the parameters and types of homogenizers influencing the efficiency of homogenization have been detailed. (orig.) [de

  17. Radiotracer investigation of cement raw meal homogenizers. Pt. 2

    Energy Technology Data Exchange (ETDEWEB)

    Baranyai, L

    1983-12-01

    Based on radioisotopic tracer technique a method has been worked out to study the homogenization and segregation processes of cement-industrial raw meal homogenizers. On-site measurements were carried out by this method in some Hungarian cement works to determine the optimal homogenization parameters of operating homogenizers. The motion and distribution of different raw meal fractions traced with /sup 198/Au radioisotope was studied in homogenization processes proceeding with different parameters. In the first part of the publication the change of charge homogenity in time was discussed which had been measured as the resultant of mixing and separating processes. In the second part the parameters and types of homogenizers influencing the efficiency of homogenization have been detailed.

  18. Homogeneous protein analysis by magnetic core-shell nanorod probes

    KAUST Repository

    Schrittwieser, Stefan

    2016-03-29

    Studying protein interactions is of vital importance both to fundamental biology research and to medical applications. Here, we report on the experimental proof of a universally applicable label-free homogeneous platform for rapid protein analysis. It is based on optically detecting changes in the rotational dynamics of magnetically agitated core-shell nanorods upon their specific interaction with proteins. By adjusting the excitation frequency, we are able to optimize the measurement signal for each analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins (soluble domain of the human epidermal growth factor receptor 2 - sHER2) specifically binding to antibodies (trastuzumab) immobilized on the surface of our nanoprobes and demonstrate direct deduction of their respective sizes. Additionally, we examine the dependence of our measurement signal on the concentration of the analyte protein, and deduce a minimally detectable sHER2 concentration of 440 pM. For our homogeneous measurement platform, good dispersion stability of the applied nanoprobes under physiological conditions is of vital importance. To that end, we support our measurement data by theoretical modeling of the total particle-particle interaction energies. The successful implementation of our platform offers scope for applications in biomarker-based diagnostics as well as for answering basic biology questions.

  19. Homogeneous Ir-192 afterloading-flab-irradiation of plane surfaces

    International Nuclear Information System (INIS)

    Bratengeier, K.; Krieger, T.

    2002-01-01

    Homogeneous irradiation of plane targets bt Ir-192 afterloading flabs made by a parallel series of linear applicators can be time-consuming even with modern planning systems. The aim of the present study was to develop an algorithm that supplies homogeneous dose distributions in an arbitrary given plane in parallel to the equipped plane of a flab. The edge and corner positions of the flab are of particular importance. The identity of the dose in the optimisation distance above the flab centre, corners, and middle of the flab edges, leads to a strict relation of the respective dwell weights. Formulas can be derived that allow the calculation of the dwell times. The dimensioning of the flab can be rapidly adapted to new conditions. A comparison with the results of Nucletron PLATO-BPS for applicator-applicator distances and step sizes of 1 cm at optimisation distances of 10, 20, 30, and 40 mm and various flab sizes (3 x 3, 9 x 9, and 15 x 15 cm 2 ) shows the following results: The standard deviation of the proposed algorithm is sometimes slightly higher than the results of the commercial planning system, whereas the underdosage at the flab edges is usually smaller. The effort for planning and preparation of the irradiation, for example using a Nucletron HDR, is below 5 minutes - a considerable reduction of planning time. (orig.) [de

  20. Homogenization techniques for population dynamics in strongly heterogeneous landscapes.

    Science.gov (United States)

    Yurk, Brian P; Cobbold, Christina A

    2018-12-01

    An important problem in spatial ecology is to understand how population-scale patterns emerge from individual-level birth, death, and movement processes. These processes, which depend on local landscape characteristics, vary spatially and may exhibit sharp transitions through behavioural responses to habitat edges, leading to discontinuous population densities. Such systems can be modelled using reaction-diffusion equations with interface conditions that capture local behaviour at patch boundaries. In this work we develop a novel homogenization technique to approximate the large-scale dynamics of the system. We illustrate our approach, which also generalizes to multiple species, with an example of logistic growth within a periodic environment. We find that population persistence and the large-scale population carrying capacity is influenced by patch residence times that depend on patch preference, as well as movement rates in adjacent patches. The forms of the homogenized coefficients yield key theoretical insights into how large-scale dynamics arise from the small-scale features.

  1. Layered Fiberconcrete with Non-Homogeneous Fibers Distribution

    OpenAIRE

    Lūsis, V; Krasņikovs, A

    2013-01-01

    The aim of present research is to create fiberconcrete construction with non-homogeneous fibers distribution in it. Traditionally fibers are homogeneously dispersed in a concrete. At the same time in many situations fiberconcretes with homogeneously dispersed fibers are not optimal (majority of added fibers are not participating in a loads bearing process).

  2. Non-homogeneous dynamic Bayesian networks for continuous data

    NARCIS (Netherlands)

    Grzegorczyk, Marco; Husmeier, Dirk

    Classical dynamic Bayesian networks (DBNs) are based on the homogeneous Markov assumption and cannot deal with non-homogeneous temporal processes. Various approaches to relax the homogeneity assumption have recently been proposed. The present paper presents a combination of a Bayesian network with

  3. Homogenized modeling methodology for 18650 lithium-ion battery module under large deformation

    Science.gov (United States)

    Tang, Liang; Cheng, Pengle

    2017-01-01

    Effective lithium-ion battery module modeling has become a bottleneck for full-size electric vehicle crash safety numerical simulation. Modeling every single cell in detail would be costly. However, computational accuracy could be lost if the module is modeled by using a simple bulk material or rigid body. To solve this critical engineering problem, a general method to establish a computational homogenized model for the cylindrical battery module is proposed. A single battery cell model is developed and validated through radial compression and bending experiments. To analyze the homogenized mechanical properties of the module, a representative unit cell (RUC) is extracted with the periodic boundary condition applied on it. An elastic–plastic constitutive model is established to describe the computational homogenized model for the module. Two typical packing modes, i.e., cubic dense packing and hexagonal packing for the homogenized equivalent battery module (EBM) model, are targeted for validation compression tests, as well as the models with detailed single cell description. Further, the homogenized EBM model is confirmed to agree reasonably well with the detailed battery module (DBM) model for different packing modes with a length scale of up to 15 × 15 cells and 12% deformation where the short circuit takes place. The suggested homogenized model for battery module makes way for battery module and pack safety evaluation for full-size electric vehicle crashworthiness analysis. PMID:28746390

  4. Homogenized modeling methodology for 18650 lithium-ion battery module under large deformation.

    Directory of Open Access Journals (Sweden)

    Liang Tang

    Full Text Available Effective lithium-ion battery module modeling has become a bottleneck for full-size electric vehicle crash safety numerical simulation. Modeling every single cell in detail would be costly. However, computational accuracy could be lost if the module is modeled by using a simple bulk material or rigid body. To solve this critical engineering problem, a general method to establish a computational homogenized model for the cylindrical battery module is proposed. A single battery cell model is developed and validated through radial compression and bending experiments. To analyze the homogenized mechanical properties of the module, a representative unit cell (RUC is extracted with the periodic boundary condition applied on it. An elastic-plastic constitutive model is established to describe the computational homogenized model for the module. Two typical packing modes, i.e., cubic dense packing and hexagonal packing for the homogenized equivalent battery module (EBM model, are targeted for validation compression tests, as well as the models with detailed single cell description. Further, the homogenized EBM model is confirmed to agree reasonably well with the detailed battery module (DBM model for different packing modes with a length scale of up to 15 × 15 cells and 12% deformation where the short circuit takes place. The suggested homogenized model for battery module makes way for battery module and pack safety evaluation for full-size electric vehicle crashworthiness analysis.

  5. Homogenization of the lipid profile values.

    Science.gov (United States)

    Pedro-Botet, Juan; Rodríguez-Padial, Luis; Brotons, Carlos; Esteban-Salán, Margarita; García-Lerín, Aurora; Pintó, Xavier; Lekuona, Iñaki; Ordóñez-Llanos, Jordi

    Analytical reports from the clinical laboratory are essential to guide clinicians about what lipid profile values should be considered altered and, therefore, require intervention. Unfortunately, there is a great heterogeneity in the lipid values reported as "normal, desirable, recommended or referenced" by clinical laboratories. This can difficult clinical decisions and be a barrier to achieve the therapeutic goals for cardiovascular prevention. A recent international recommendation has added a new heterogeneity factor for the interpretation of lipid profile, such as the possibility of measuring it without previous fasting. All this justifies the need to develop a document that adapts the existing knowledge to the clinical practice of our health system. In this regard, professionals from different scientific societies involved in the measurement and use of lipid profile data have developed this document to establish recommendations that facilitate their homogenization. Copyright © 2017. Publicado por Elsevier España, S.L.U.

  6. The structure and homogeneity of Psalm 32

    Directory of Open Access Journals (Sweden)

    J. Henk Potgieter

    2014-11-01

    Full Text Available Psalm 32 is widely regarded as a psalm of thanksgiving with elements of wisdom poetry intermingled into it. The wisdom elements are variously explained as having been present from the beginning, or as having been added to a foundational composition. Such views of the Gattung have had a decisive influence on the interpretation of the psalm. This article argues, on the basis of a structural analysis, that Psalm 32 should be understood as a homogeneous wisdom composition. The parallel and inverse structure of its two stanzas demonstrate that the aim of its author was to encourage the upright to foster an open, intimate relationship with Yahweh in which transgressions are confessed and Yahweh’s benevolent guidance on the way of life is wisely accepted.

  7. Precipitation of plutonium oxalate from homogeneous solutions

    International Nuclear Information System (INIS)

    Rao, V.K.; Pius, I.C.; Subbarao, M.; Chinnusamy, A.; Natarajan, P.R.

    1986-01-01

    A method for the precipitation of plutonium(IV) oxalate from homogeneous solutions using diethyl oxalate is reported. The precipitate obtained is crystalline and easily filterable with yields in the range of 92-98% for precipitations involving a few mg to g quantities of plutonium. Decontamination factors for common impurities such as U(VI), Am(III) and Fe(III) were determined. TGA and chemical analysis of the compound indicate its composition as Pu(Csub(2)Osub(4))sub(2).6Hsub(2)O. Data are obtained on the solubility of the oxalate in nitric acid and in mixtures of nitric acid and oxalic acid of varying concentrations. Green PuOsub(2) obtained by calcination of the oxalate has specifications within the recommended values for trace foreign substances such as chlorine, fluorine, carbon and nitrogen. (author)

  8. Homogenization in thermoelasticity: application to composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Peyroux, R [Lab. de Mecanique et Genie Civil, Univ. Montpellier 2, 34 Montpellier (France); Licht, C [Lab. de Mecanique et Genie Civil, Univ. Montpellier 2, 34 Montpellier (France)

    1993-11-01

    One of the obstacles to the industrial use of metal matrix composite materials is the damage they rapidly undergo when they are subjected to cyclic thermal loadings; local thermal stresses of high level can develop, sometimes nearby or over the elastic limit, due to the mismatch of elastic and thermal coefficients between the fibers and the matrix. For the same reasons, early cracks can appear in composites like ceramic-ceramic. Therefore, we investigate the linear thermoelastic behaviour of heterogeneous materials, taking account of the isentropic coupling term in the heat conduction equation. In the case of periodic materials, recent results, using the homogenization theory, allowed us to describe macroscopic and microscopic behaviours of such materials. This paper is concerned with the numerical simulation of this problem by a finite element method, using a multiscale approach. (orig.).

  9. Modelling of an homogeneous equilibrium mixture model

    International Nuclear Information System (INIS)

    Bernard-Champmartin, A.; Poujade, O.; Mathiaud, J.; Mathiaud, J.; Ghidaglia, J.M.

    2014-01-01

    We present here a model for two phase flows which is simpler than the 6-equations models (with two densities, two velocities, two temperatures) but more accurate than the standard mixture models with 4 equations (with two densities, one velocity and one temperature). We are interested in the case when the two-phases have been interacting long enough for the drag force to be small but still not negligible. The so-called Homogeneous Equilibrium Mixture Model (HEM) that we present is dealing with both mixture and relative quantities, allowing in particular to follow both a mixture velocity and a relative velocity. This relative velocity is not tracked by a conservation law but by a closure law (drift relation), whose expression is related to the drag force terms of the two-phase flow. After the derivation of the model, a stability analysis and numerical experiments are presented. (authors)

  10. Systematic assembly homogenization and local flux reconstruction for nodal method calculations of fast reactor power distributions

    International Nuclear Information System (INIS)

    Dorning, J.J.

    1991-01-01

    A simultaneous pin lattice cell and fuel bundle homogenization theory has been developed for use with nodal diffusion calculations of practical reactors. The theoretical development of the homogenization theory, which is based on multiple-scales asymptotic expansion methods carried out through fourth order in a small parameter, starts from the transport equation and systematically yields: a cell-homogenized bundled diffusion equation with self-consistent expressions for the cell-homogenized cross sections and diffusion tensor elements; and a bundle-homogenized global reactor diffusion equation with self-consistent expressions for the bundle-homogenized cross sections and diffusion tensor elements. The continuity of the angular flux at cell and bundle interfaces also systematically yields jump conditions for the scaler flux or so-called flux discontinuity factors on the cell and bundle interfaces in terms of the two adjacent cell or bundle eigenfunctions. The expressions required for the reconstruction of the angular flux or the 'de-homogenization' theory were obtained as an integral part of the development; hence the leading order transport theory angular flux is easily reconstructed throughout the reactor including the regions in the interior of the fuel bundles or computational nodes and in the interiors of the pin lattice cells. The theoretical development shows that the exact transport theory angular flux is obtained to first order from the whole-reactor nodal diffusion calculations, done using the homogenized nuclear data and discontinuity factors, is a product of three computed quantities: a ''cell shape function''; a ''bundle shape function''; and a ''global shape function''. 10 refs

  11. Homogeneous wave turbulence driven by tidal flows

    Science.gov (United States)

    Favier, B.; Le Reun, T.; Barker, A.; Le Bars, M.

    2017-12-01

    When a moon orbits around a planet, the rotation of the induced tidal bulge drives a homogeneous, periodic, large-scale flow. The combination of such an excitation with the rotating motion of the planet has been shown to drive parametric resonance of a pair of inertial waves in a mechanism called the elliptical instability. Geophysical fluid layers can also be stratified: this is the case for instance of the Earth's oceans and, as suggested by several studies, of the upper part of the Earth's liquid Outer Core. We thus investigate the stability of a rotating and stratified layer undergoing tidal distortion in the limit where either rotation or stratification is dominant. We show that the periodic tidal flow drives a parametric subharmonic resonance of inertial (resp. internal) waves in the rotating (resp. stratified) case. The instability saturates into a wave turbulence pervading the whole fluid layer. In such a state, the instability mechanism conveys the tidal energy from the large scale tidal flow to the resonant modes, which then feed a succession of triadic resonances also generating small spatial scales. In the rotating case, we observe a kinetic energy spectrum with a k-2 slope for which the Coriolis force is dominant at all spatial scales. In the stratified case, where the timescale separation is increased between the tidal excitation and the Brunt-Väisälä frequencies, the temporal spectrum decays with a ω-2 power law up to the cut-off frequency beyond which waves do not exist. This result is reminiscent of the Garrett and Munk spectrum measured in the oceans and theoretically described as a manifestation of internal wave turbulence. In addition to revealing an instability driving homogeneous turbulence in geophysical fluid layers, our approach is also an efficient numerical tool to investigate the possibly universal properties of wave turbulence in a geophysical context.

  12. Conformally compactified homogeneous spaces (Possible Observable Consequences)

    International Nuclear Information System (INIS)

    Budinich, P.

    1995-01-01

    Some arguments based on the possible spontaneous violation of the Cosmological Principles (represented by the observed large-scale structures of galaxies), the Cartan-geometry of simple spinors and on the Fock-formulation of hydrogen-atom wave-equation in momentum-space, are presented in favour of the hypothesis that space-time and momentum-space should be both conformally compactified and represented by the two four-dimensional homogeneous spaces of the conformal group, both isomorphic to (S 3 X S 1 )/Z 2 and correlated by conformal inversion. Within this framework, the possible common origin for the S0(4) symmetry underlying the geometrical structure of the Universe, of Kepler orbits and of the H-atom is discussed. On of the consequences of the proposed hypothesis could be that any quantum field theory should be naturally free from both infrared and ultraviolet divergences. But then physical spaces defined as those where physical phenomena may be best described, could be different from those homogeneous spaces. A simple, exactly soluble, toy model, valid for a two-dimensional space-time is presented where the conjecture conformally compactified space-time and momentum-space are both isomorphic to (S 1 X S 1 )/Z 2 , while the physical spaces are two finite lattice which are dual since Fourier transforms, represented by finite, discrete, sums may be well defined on them. Furthermore, a q-deformed SU q (1,1) may be represented on them if q is a root of unity. (author). 22 refs, 3 figs

  13. Value distribution of meromorphic solutions of homogeneous and non-homogeneous complex linear differential-difference equations

    Directory of Open Access Journals (Sweden)

    Luo Li-Qin

    2016-01-01

    Full Text Available In this paper, we investigate the value distribution of meromorphic solutions of homogeneous and non-homogeneous complex linear differential-difference equations, and obtain the results on the relations between the order of the solutions and the convergence exponents of the zeros, poles, a-points and small function value points of the solutions, which show the relations in the case of non-homogeneous equations are sharper than the ones in the case of homogeneous equations.

  14. Etude de quelques conditions influençant la filtration des vins sur membrane

    Directory of Open Access Journals (Sweden)

    M. Salgues

    1982-12-01

    The filterability test proposed by Gaillard helps to estimate the volume of wine that can be filtered by a winery, to control and optimise the assembly line preparation of wines. Different applications are studied. The water flowrate test allows a better control of clopping and of membrane regeneration. Regeneration technics by soaking in detergent solutions are studied and proposed.

  15. Radiation induced homogeneous precipitation in undersaturated solid-solutions

    International Nuclear Information System (INIS)

    Cauvin, Richard; Martin, Georges.

    1978-01-01

    The stability of various types of solid solutions under irradiation is studied. In this paper, observations made on AlZn solid solutions under 1 MeV electron irradiation are reported. Al-Zn was chosen as a prototype of solid solutions with a simple miscibility gap. It is shown that under appropriate irradiation conditions undersaturated AnZn solid solutions give rise to a homogeneous precipitation of coherent G.P. zones and of incoherent Zn precipitates the atomic volume of which is smaller than that of the matrix. We propose a more general treatment of solute concentration heterogeneities in solid solutions under irradiation and suggest how it might account for the nucleation of the observed phases. The growth of the observed precipitates is studied

  16. A spatially homogeneous and isotropic Einstein-Dirac cosmology

    Science.gov (United States)

    Finster, Felix; Hainzl, Christian

    2011-04-01

    We consider a spatially homogeneous and isotropic cosmological model where Dirac spinors are coupled to classical gravity. For the Dirac spinors we choose a Hartree-Fock ansatz where all one-particle wave functions are coherent and have the same momentum. If the scale function is large, the universe behaves like the classical Friedmann dust solution. If however the scale function is small, quantum effects lead to oscillations of the energy-momentum tensor. It is shown numerically and proven analytically that these quantum oscillations can prevent the formation of a big bang or big crunch singularity. The energy conditions are analyzed. We prove the existence of time-periodic solutions which go through an infinite number of expansion and contraction cycles.

  17. The homogeneous boundary value problem of the thick spherical shell

    International Nuclear Information System (INIS)

    Linder, F.

    1975-01-01

    With the aim to solve boundary value problems in the same manner as it is attained at thin shell theory (Superposition of Membrane solution to solution of boundary values), one has to search solutions of the equations of equilibrium of the three dimensional thick shell which produce tensions at the cut edge and are zero on the whole shell surface inside and outside. This problem was solved with the premissions of the linear theory of Elasticity. The gained solution is exact and contains the symmetric and non-symmetric behaviour and is described in relatively short analytical expressions for the deformations and tensions, after the problem of the coupled system had been solved. The static condition of the two surfaces (zero tension) leads to a homogeneous system of complex equations with the index of the Legendre spherical function as Eigenvalue. One symmetrical case is calculated numerically and is compared with the method of finite elements. This comparison results in good accordance. (Auth.)

  18. Dissolution test for homogeneity of mixed oxide fuel pellets

    International Nuclear Information System (INIS)

    Lerch, R.E.

    1979-08-01

    Experiments were performed to determine the relationship between fuel pellet homogeneity and pellet dissolubility. Although, in general, the amount of pellet residue decreased with increased homogeneity, as measured by the pellet figure of merit, the relationship was not absolute. Thus, all pellets with high figure of merit (excellent homogeneity) do not necessarily dissolve completely and all samples that dissolve completely do not necessarily have excellent homogeneity. It was therefore concluded that pellet dissolubility measurements could not be substituted for figure of merit determinations as a measurement of pellet homogeneity. 8 figures, 3 tables

  19. Assembly homogenization techniques for light water reactor analysis

    International Nuclear Information System (INIS)

    Smith, K.S.

    1986-01-01

    Recent progress in development and application of advanced assembly homogenization methods for light water reactor analysis is reviewed. Practical difficulties arising from conventional flux-weighting approximations are discussed and numerical examples given. The mathematical foundations for homogenization methods are outlined. Two methods, Equivalence Theory and Generalized Equivalence Theory which are theoretically capable of eliminating homogenization error are reviewed. Practical means of obtaining approximate homogenized parameters are presented and numerical examples are used to contrast the two methods. Applications of these techniques to PWR baffle/reflector homogenization and BWR bundle homogenization are discussed. Nodal solutions to realistic reactor problems are compared to fine-mesh PDQ calculations, and the accuracy of the advanced homogenization methods is established. Remaining problem areas are investigated, and directions for future research are suggested. (author)

  20. Homogeneous deuterium exchange using rhenium and platinum chloride catalysts

    International Nuclear Information System (INIS)

    Fawdry, R.M.

    1979-01-01

    Previous studies of homogeneous hydrogen isotope exchange are mostly confined to one catalyst, the tetrachloroplatinite salt. Recent reports have indicated that chloride salts of iridium and rhodium may also be homogeneous exchange catalysts similar to the tetrachloroplatinite, but with much lower activities. Exchange by these homogeneous catalysts is frequently accompanied by metal precipitation with the termination of homogeneous exchange, particularly in the case of alkane exchange. The studies presented in this thesis describe two different approaches to overcome this limitation of homogeneous hydrogen isotope exchange catalysts. The first approach was to improve the stability of an existing homogeneous catalyst and the second was to develop a new homogeneous exchange catalyst which is free of the instability limitation

  1. Design of Stirrer Impeller with Variable Operational Speed for a Food Waste Homogenizer

    Directory of Open Access Journals (Sweden)

    Idris A. Kayode

    2016-05-01

    Full Text Available A conceptualized impeller called KIA is designed for impact agitation of food waste in a homogenizer. A comparative analysis of the performance of KIA is made with three conventional impeller types, Rushton, Anchor, and Pitched Blade. Solid–liquid mixing of a moisture-rich food waste is simulated under various operational speeds, in order to compare the dispersions and thermal distributions at homogenous slurry conditions. Using SolidWorks, the design of the impellers employs an Application Programming Interface (API which acts as the canvas for creating a graphical user interface (GUI for automation of its assembly. A parametric analysis of the homogenizer, at varying operational speeds, enables the estimation of the critical speed of the mixing shaft diameter and the deflection under numerous mixing conditions and impeller configurations. The numerical simulation of the moisture-rich food waste (approximated as a Newtonian carrot–orange soup is performed with ANSYS CFX v.15.0. The velocity and temperature field distribution of the homogenizer for various impeller rotational speeds are analyzed. It is anticipated that the developed model will help in the selection of a suitable impeller for efficient mixing of food waste in the homogenizer.

  2. Production of heavy water in France; Etude sur la production d'eau lourde en France

    Energy Technology Data Exchange (ETDEWEB)

    Lerat, J M; Roth, E [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Lefrancois, B [Houllere du Bassin du Nord et du Pas de Calais (France)

    1964-07-01

    Since 1958, studies relating to heavy water production have covered several processes. Each one has been examined to a greater or lesser degree and attention has finally been concentrated on the isotopic exchanges between hydrogen sulphide and water and between ammonia and synthesis gas, the pilot experiment having shown that hydrogen distillation, although technologically satisfactory, was not competitive. NH{sub 3} synthesis gas exchange process; 1) Research was continued and led to the decision to build a production unit, devoted also to the synthesis of ammonia. The process essentially depends on the source of the synthesis gas; the use of a H{sub 2}O/H{sub 2} exchange, which could make it independent, has in fact been rejected for economic reasons. Amongst the various possible designs for the process, the one temperature system was chosen, in spite of certain technological problems, because of it provides: a high enrichment with a reduced number of contact devices. These have now been perfected after large-scale pilot tests. The original industrial experiment to be set in operation will supply useful information for second generation plants, whether they use the one temperature lay out again or whether they adopt the two temperature system. H{sub 2}S-H{sub 2}O exchange process. The pilot plant, described in 1958, has been used for a systematic study of corrosion. It was possible to proceed to preliminary specifications of plants, with 2 or 3 H{sub 2}S - H{sub 2}O stages exchange for primary enrichment. They final stage beyond a 10 to 20 p.100 D{sub 2}O concentration being carried out by the distillation of water. Various heat exchange systems have been studied in detail and it was concluded that choices, as for instance the one of optimum division of the cascade, were eventually to be made according to the particular economic conditions of creation at the chosen location of the plant. (author) [French] Depuis 1958 les etudes concernant la production d

  3. Stability of vitamin C in frozen raw fruit and vegetable homogenates

    Science.gov (United States)

    Retention of vitamin C in homogenized raw fruits and vegetables stored under laboratory conditions prior to analysis was investigated. Raw collard greens, clementines, and potatoes were chosen, to be representative of food matrices to be sampled in USDA’s National Food and Nutrient Analysis Program...

  4. Diffusive transport of radon in a homogeneous column of dry sand

    NARCIS (Netherlands)

    van der Spoel, W.H.; van der Graaf, E.R.; de Meijer, R.J.

    To validate a model for radon transport in soil, measurements of diffusive radon transport under well-defined and controlled conditions have been made in a homogeneous column of dry sand with an air-filled volume on top. This volume simulates a crawl space. The measurements concern time-dependent

  5. On the infimum of the energy-momentum spectrum of a homogeneous Bose gas

    DEFF Research Database (Denmark)

    Cornean, Horia; Derezinski, J.; Zin, P.

    2009-01-01

    We consider second-quantized homogeneous Bose gas in a large cubic box with periodic boundary conditions at zero temperature. We discuss the energy-momentum spectrum of the Bose gas and its physical significance. We review various rigorous and heuristic results as well as open conjectures about its...

  6. Using Floquet periodicity to easily calculate dispersion curves and wave structures of homogeneous waveguides

    Science.gov (United States)

    Hakoda, Christopher; Rose, Joseph; Shokouhi, Parisa; Lissenden, Clifford

    2018-04-01

    Dispersion curves are essential to any guided-wave-related project. The Semi-Analytical Finite Element (SAFE) method has become the conventional way to compute dispersion curves for homogeneous waveguides. However, only recently has a general SAFE formulation for commercial and open-source software become available, meaning that until now SAFE analyses have been variable and more time consuming than desirable. Likewise, the Floquet boundary conditions enable analysis of waveguides with periodicity and have been an integral part of the development of metamaterials. In fact, we have found the use of Floquet boundary conditions to be an extremely powerful tool for homogeneous waveguides, too. The nuances of using periodic boundary conditions for homogeneous waveguides that do not exhibit periodicity are discussed. Comparisons between this method and SAFE are made for selected homogeneous waveguide applications. The COMSOL Multiphysics software is used for the results shown, but any standard finite element software that can implement Floquet periodicity (user-defined or built-in) should suffice. Finally, we identify a number of complex waveguides for which dispersion curves can be found with relative ease by using the periodicity inherent to the Floquet boundary conditions.

  7. On the infimum of the energy-momentum spectrum of a homogeneous Bose gas

    DEFF Research Database (Denmark)

    Cornean, Horia; Derezinski, J.; Zin, P.

    We consider second quantized homogeneous Bose gas in a large cubic box with periodic boundary conditions, at zero temperature, and in the grand canonical setting (the chemical potential μ is fixed, the number of particles can vary). We investigate upper bounds on the infimum of the energy...

  8. Fibonacci-like Differential Equations with a Polynomial Non-Homogeneous Part

    NARCIS (Netherlands)

    Asveld, P.R.J.

    1989-01-01

    We investigate non-homogeneous linear differential equations of the form $x''(t) + x'(t) - x(t) = p(t)$ where $p(t)$ is either a polynomial or a factorial polynomial in $t$. We express the solution of these differential equations in terms of the coefficients of $p(t)$, in the initial conditions, and

  9. On the decay of homogeneous isotropic turbulence

    Science.gov (United States)

    Skrbek, L.; Stalp, Steven R.

    2000-08-01

    Decaying homogeneous, isotropic turbulence is investigated using a phenomenological model based on the three-dimensional turbulent energy spectra. We generalize the approach first used by Comte-Bellot and Corrsin [J. Fluid Mech. 25, 657 (1966)] and revised by Saffman [J. Fluid Mech. 27, 581 (1967); Phys. Fluids 10, 1349 (1967)]. At small wave numbers we assume the spectral energy is proportional to the wave number to an arbitrary power. The specific case of power 2, which follows from the Saffman invariant, is discussed in detail and is later shown to best describe experimental data. For the spectral energy density in the inertial range we apply both the Kolmogorov -5/3 law, E(k)=Cɛ2/3k-5/3, and the refined Kolmogorov law by taking into account intermittency. We show that intermittency affects the energy decay mainly by shifting the position of the virtual origin rather than altering the power law of the energy decay. Additionally, the spectrum is naturally truncated due to the size of the wind tunnel test section, as eddies larger than the physical size of the system cannot exist. We discuss effects associated with the energy-containing length scale saturating at the size of the test section and predict a change in the power law decay of both energy and vorticity. To incorporate viscous corrections to the model, we truncate the spectrum at an effective Kolmogorov wave number kη=γ(ɛ/v3)1/4, where γ is a dimensionless parameter of order unity. We show that as the turbulence decays, viscous corrections gradually become more important and a simple power law can no longer describe the decay. We discuss the final period of decay within the framework of our model, and show that care must be taken to distinguish between the final period of decay and the change of the character of decay due to the saturation of the energy containing length scale. The model is applied to a number of experiments on decaying turbulence. These include the downstream decay of turbulence in

  10. Homogeneous Thorium Fuel Cycles in Candu Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Hyland, B.; Dyck, G.R.; Edwards, G.W.R.; Magill, M. [Chalk River Laboratories, Atomic Energy of Canada Limited (Canada)

    2009-06-15

    The CANDU{sup R} reactor has an unsurpassed degree of fuel-cycle flexibility, as a consequence of its fuel-channel design, excellent neutron economy, on-power refueling, and simple fuel bundle [1]. These features facilitate the introduction and full exploitation of thorium fuel cycles in Candu reactors in an evolutionary fashion. Because thorium itself does not contain a fissile isotope, neutrons must be provided by adding a fissile material, either within or outside of the thorium-based fuel. Those same Candu features that provide fuel-cycle flexibility also make possible many thorium fuel-cycle options. Various thorium fuel cycles can be categorized by the type and geometry of the added fissile material. The simplest of these fuel cycles are based on homogeneous thorium fuel designs, where the fissile material is mixed uniformly with the fertile thorium. These fuel cycles can be competitive in resource utilization with the best uranium-based fuel cycles, while building up a 'mine' of U-233 in the spent fuel, for possible recycle in thermal reactors. When U-233 is recycled from the spent fuel, thorium-based fuel cycles in Candu reactors can provide substantial improvements in the efficiency of energy production from existing fissile resources. The fissile component driving the initial fuel could be enriched uranium, plutonium, or uranium-233. Many different thorium fuel cycle options have been studied at AECL [2,3]. This paper presents the results of recent homogeneous thorium fuel cycle calculations using plutonium and enriched uranium as driver fuels, with and without U-233 recycle. High and low burnup cases have been investigated for both the once-through and U-233 recycle cases. CANDU{sup R} is a registered trademark of Atomic Energy of Canada Limited (AECL). 1. Boczar, P.G. 'Candu Fuel-Cycle Vision', Presented at IAEA Technical Committee Meeting on 'Fuel Cycle Options for LWRs and HWRs', 1998 April 28 - May 01, also Atomic Energy

  11. Contribution to the study of the uranium-hydrogen system; Contribution a l'etude du systeme uranium-hydrogene

    Energy Technology Data Exchange (ETDEWEB)

    Chevallier, J [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1965-01-01

    Previous work on uranium-hydrogen system is reviewed. The U-H{sub 2}-UH{sub n} equilibrium is then investigated at pressures below one atmosphere, i.e. at temperatures lower than 430 deg. C. The hydride obtained at equilibrium is deficient in hydrogen (UH{sub n<3}), the hydrogen deficit increasing as the temperature rises. Thermodynamic functions for the formation of non-stoichiometric hydride and of one hydrogen vacancy are derived from pressure composition isotherms, in U-H phase diagram is proposed. The hydrogenation of U-UC alloys is also examined at pressures below one atmosphere with regard to the equilibrium: (free U + UC) - H{sub 2}-UH{sub n}. The equilibrium conditions are found different from that observed for pure uranium. (author) [French] Une etude bibliographique du systeme uranium-hydrogene est exposee. L'equilibre U-H{sub 2}-UH{sub n} est ensuite etudie sous des pressions inferieures a une atmosphere, soit aux temperatures inferieures a environ 430 degs. C. L'hydrure obtenu a l'equilibre est deficitaire en hydrogene - UH{sub n<3} - et d'autant plus que la temperature s'eleve. Les grandeurs thermodynamiques relatives a la formation et a la saturation de l'hydrure, ainsi qu'a la formation d'une lacune d'hydrogene sont deduites des pressions d'equilibre. Un modele de diagramme de phases U-H est propose. L'hyduration des alliages U-UC est etudiee egalement sous des pressions inferieures a l'atmosphere, au point de vue de l'equilibre (U libre + UC) - H{sub 2}-UH{sub n}. Les conditions d'equilibre sont trouvees differentes de celles observees sur l'uranium pur. (auteur)

  12. Persymmetric Adaptive Detectors of Subspace Signals in Homogeneous and Partially Homogeneous Clutter

    Directory of Open Access Journals (Sweden)

    Ding Hao

    2015-08-01

    Full Text Available In the field of adaptive radar detection, an effective strategy to improve the detection performance is to exploit the structural information of the covariance matrix, especially in the case of insufficient reference cells. Thus, in this study, the problem of detecting multidimensional subspace signals is discussed by considering the persymmetric structure of the clutter covariance matrix, which implies that the covariance matrix is persymmetric about its cross diagonal. Persymmetric adaptive detectors are derived on the basis of the one-step principle as well as the two-step Generalized Likelihood Ratio Test (GLRT in homogeneous and partially homogeneous clutter. The proposed detectors consider the structural information of the covariance matrix at the design stage. Simulation results suggest performance improvement compared with existing detectors when reference cells are insufficient. Moreover, the detection performance is assessed with respect to the effects of the covariance matrix, signal subspace dimension, and mismatched performance of signal subspace as well as signal fluctuations.

  13. Dynamic contact angle cycling homogenizes heterogeneous surfaces.

    Science.gov (United States)

    Belibel, R; Barbaud, C; Mora, L

    2016-12-01

    In order to reduce restenosis, the necessity to develop the appropriate coating material of metallic stent is a challenge for biomedicine and scientific research over the past decade. Therefore, biodegradable copolymers of poly((R,S)-3,3 dimethylmalic acid) (PDMMLA) were prepared in order to develop a new coating exhibiting different custom groups in its side chain and being able to carry a drug. This material will be in direct contact with cells and blood. It consists of carboxylic acid and hexylic groups used for hydrophilic and hydrophobic character, respectively. The study of this material wettability and dynamic surface properties is of importance due to the influence of the chemistry and the potential motility of these chemical groups on cell adhesion and polymer kinetic hydrolysis. Cassie theory was used for the theoretical correction of contact angles of these chemical heterogeneous surfaces coatings. Dynamic Surface Analysis was used as practical homogenizer of chemical heterogeneous surfaces by cycling during many cycles in water. In this work, we confirmed that, unlike receding contact angle, advancing contact angle is influenced by the difference of only 10% of acidic groups (%A) in side-chain of polymers. It linearly decreases with increasing acidity percentage. Hysteresis (H) is also a sensitive parameter which is discussed in this paper. Finally, we conclude that cycling provides real information, thus avoiding theoretical Cassie correction. H(10)is the most sensible parameter to %A. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Elastic metamaterials and dynamic homogenization: a review

    Directory of Open Access Journals (Sweden)

    Ankit Srivastava

    2015-01-01

    Full Text Available In this paper, we review the recent advances which have taken place in the understanding and applications of acoustic/elastic metamaterials. Metamaterials are artificially created composite materials which exhibit unusual properties that are not found in nature. We begin with presenting arguments from discrete systems which support the case for the existence of unusual material properties such as tensorial and/or negative density. The arguments are then extended to elastic continuums through coherent averaging principles. The resulting coupled and nonlocal homogenized relations, called the Willis relations, are presented as the natural description of inhomogeneous elastodynamics. They are specialized to Bloch waves propagating in periodic composites and we show that the Willis properties display the unusual behavior which is often required in metamaterial applications such as the Veselago lens. We finally present the recent advances in the area of transformation elastodynamics, charting its inspirations from transformation optics, clarifying its particular challenges, and identifying its connection with the constitutive relations of the Willis and the Cosserat types.

  15. Homogenization models for 2-D grid structures

    Science.gov (United States)

    Banks, H. T.; Cioranescu, D.; Rebnord, D. A.

    1992-01-01

    In the past several years, we have pursued efforts related to the development of accurate models for the dynamics of flexible structures made of composite materials. Rather than viewing periodicity and sparseness as obstacles to be overcome, we exploit them to our advantage. We consider a variational problem on a domain that has large, periodically distributed holes. Using homogenization techniques we show that the solution to this problem is in some topology 'close' to the solution of a similar problem that holds on a much simpler domain. We study the behavior of the solution of the variational problem as the holes increase in number, but decrease in size in such a way that the total amount of material remains constant. The result is an equation that is in general more complex, but with a domain that is simply connected rather than perforated. We study the limit of the solution as the amount of material goes to zero. This second limit will, in most cases, retrieve much of the simplicity that was lost in the first limit without sacrificing the simplicity of the domain. Finally, we show that these results can be applied to the case of a vibrating Love-Kirchhoff plate with Kelvin-Voigt damping. We rely heavily on earlier results of (Du), (CS) for the static, undamped Love-Kirchhoff equation. Our efforts here result in a modification of those results to include both time dependence and Kelvin-Voigt damping.

  16. Homogeneous cosmology with aggressively expanding civilizations

    International Nuclear Information System (INIS)

    Jay Olson, S

    2015-01-01

    In the context of a homogeneous Universe, we note that the appearance of aggressively expanding advanced life is geometrically similar to the process of nucleation and bubble growth in a first-order cosmological phase transition. We exploit this similarity to describe the dynamics of life saturating the Universe on a cosmic scale, adapting the phase transition model to incorporate probability distributions of expansion and resource consumption strategies. Through a series of numerical solutions spanning several orders of magnitude in the input assumption parameters, the resulting cosmological model is used to address basic questions related to the intergalactic spreading of life, dealing with issues such as timescales, observability, competition between strategies, and first-mover advantage. Finally, we examine physical effects on the Universe itself, such as reheating and the backreaction on the evolution of the scale factor, if such life is able to control and convert a significant fraction of the available pressureless matter into radiation. We conclude that the existence of life, if certain advanced technologies are practical, could have a significant influence on the future large-scale evolution of the Universe. (paper)

  17. Numerical computation of homogeneous slope stability.

    Science.gov (United States)

    Xiao, Shuangshuang; Li, Kemin; Ding, Xiaohua; Liu, Tong

    2015-01-01

    To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS) to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM) and particle swarm optimization algorithm (PSO) to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759) were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS).

  18. Numerical Computation of Homogeneous Slope Stability

    Directory of Open Access Journals (Sweden)

    Shuangshuang Xiao

    2015-01-01

    Full Text Available To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM and particle swarm optimization algorithm (PSO to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759 were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS.

  19. Thermal neutron diffusion parameters in homogeneous mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Drozdowicz, K.; Krynicka, E. [Institute of Nuclear Physics, Cracow (Poland)

    1995-12-31

    A physical background is presented for a computer program which calculates the thermal neutron diffusion parameters for homogeneous mixtures of any compounds. The macroscopic absorption, scattering and transport cross section of the mixture are defined which are generally function of the incident neutron energy. The energy-averaged neutron parameters are available when these energy dependences and the thermal neutron energy distribution are assumed. Then the averaged diffusion coefficient and the pulsed thermal neutron parameters (the absorption rare and the diffusion constant) are also defined. The absorption cross section is described by the 1/v law and deviations from this behaviour are considered. The scattering cross section can be assumed as being almost constant in the thermal neutron region (which results from the free gas model). Serious deviations are observed for hydrogen atoms bound in molecules and a special study in the paper is devoted to this problem. A certain effective scattering cross section is found in this case on a base of individual exact data for a few hydrogenous media. Approximations assumed for the average cosine of the scattering angle are also discussed. The macroscopic parameters calculated are averaged over the Maxwellian energy distribution for the thermal neutron flux. An information on the input data for the computer program is included. (author). 10 refs, 4 figs, 5 tabs.

  20. Lagrangian statistics in compressible isotropic homogeneous turbulence

    Science.gov (United States)

    Yang, Yantao; Wang, Jianchun; Shi, Yipeng; Chen, Shiyi

    2011-11-01

    In this work we conducted the Direct Numerical Simulation (DNS) of a forced compressible isotropic homogeneous turbulence and investigated the flow statistics from the Lagrangian point of view, namely the statistics is computed following the passive tracers trajectories. The numerical method combined the Eulerian field solver which was developed by Wang et al. (2010, J. Comp. Phys., 229, 5257-5279), and a Lagrangian module for tracking the tracers and recording the data. The Lagrangian probability density functions (p.d.f.'s) have then been calculated for both kinetic and thermodynamic quantities. In order to isolate the shearing part from the compressing part of the flow, we employed the Helmholtz decomposition to decompose the flow field (mainly the velocity field) into the solenoidal and compressive parts. The solenoidal part was compared with the incompressible case, while the compressibility effect showed up in the compressive part. The Lagrangian structure functions and cross-correlation between various quantities will also be discussed. This work was supported in part by the China's Turbulence Program under Grant No.2009CB724101.

  1. Forming homogeneous clusters for differential risk information

    International Nuclear Information System (INIS)

    Maardberg, B.

    1996-01-01

    Latent risk situations are always present in society. General information on these risk situations is supposed to be received differently by different groups of people in the population. In the aftermath of specific accidents different groups presumably have need of specific information about how to act to survive, to avoid injuries, to find more information, to obtain facts about the accidents etc. As targets for information these different groups could be defined in different ways. The conventional way is to divide the population according to demographic variables, such as age, sex, occupation etc. Another way would be to structure the population according to dependent variables measured in different studies. They may concern risk perception, emotional reactions, specific technical knowledge of the accidents, and belief in the information sources. One procedure for forming such groupings of people into homogeneous clusters would be by statistical clustering methods on dependent variables. Examples of such clustering procedures are presented and discussed. Data are from a Norwegian study on the perception of radiation from nuclear accidents and other radiation sources. Speculations are made on different risk information strategies. Elements of a research programme are proposed. (author)

  2. Homogeneous purely buoyancy driven turbulent flow

    Science.gov (United States)

    Arakeri, Jaywant; Cholemari, Murali; Pawar, Shashikant

    2010-11-01

    An unstable density difference across a long vertical tube open at both ends leads to convection that is axially homogeneous with a linear density gradient. We report results from such tube convection experiments, with driving density caused by salt concentration difference or temperature difference. At high enough Rayleigh numbers (Ra) the convection is turbulent with zero mean flow and zero mean Reynolds shear stresses; thus turbulent production is purely by buoyancy. We observe different regimes of turbulent convection. At very high Ra the Nusselt number scales as the square root of the Rayleigh number, giving the so-called "ultimate regime" of convection predicted for Rayleigh-Benard convection in limit of infinite Ra. Turbulent convection at intermediate Ra, the Nusselt number scales as Ra^0.3. In both regimes, the flux and the Taylor scale Reynolds number are more than order of magnitude larger than those obtained in Rayleigh-Benard convection. Absence of a mean flow makes this an ideal flow to study shear free turbulence near a wall.

  3. Thermal neutron diffusion parameters in homogeneous mixtures

    International Nuclear Information System (INIS)

    Drozdowicz, K.; Krynicka, E.

    1995-01-01

    A physical background is presented for a computer program which calculates the thermal neutron diffusion parameters for homogeneous mixtures of any compounds. The macroscopic absorption, scattering and transport cross section of the mixture are defined which are generally function of the incident neutron energy. The energy-averaged neutron parameters are available when these energy dependences and the thermal neutron energy distribution are assumed. Then the averaged diffusion coefficient and the pulsed thermal neutron parameters (the absorption rare and the diffusion constant) are also defined. The absorption cross section is described by the 1/v law and deviations from this behaviour are considered. The scattering cross section can be assumed as being almost constant in the thermal neutron region (which results from the free gas model). Serious deviations are observed for hydrogen atoms bound in molecules and a special study in the paper is devoted to this problem. A certain effective scattering cross section is found in this case on a base of individual exact data for a few hydrogenous media. Approximations assumed for the average cosine of the scattering angle are also discussed. The macroscopic parameters calculated are averaged over the Maxwellian energy distribution for the thermal neutron flux. An information on the input data for the computer program is included. (author). 10 refs, 4 figs, 5 tabs

  4. Radiation statistics in homogeneous isotropic turbulence

    International Nuclear Information System (INIS)

    Da Silva, C B; Coelho, P J; Malico, I

    2009-01-01

    An analysis of turbulence-radiation interaction (TRI) in statistically stationary (forced) homogeneous and isotropic turbulence is presented. A direct numerical simulation code was used to generate instantaneous turbulent scalar fields, and the radiative transfer equation (RTE) was solved to provide statistical data relevant in TRI. The radiation intensity is non-Gaussian and is not spatially correlated with any of the other turbulence or radiation quantities. Its power spectrum exhibits a power-law region with a slope steeper than the classical -5/3 law. The moments of the radiation intensity, Planck-mean and incident-mean absorption coefficients, and emission and absorption TRI correlations are calculated. The influence of the optical thickness of the medium, mean and variance of the temperature and variance of the molar fraction of the absorbing species is studied. Predictions obtained from the time-averaged RTE are also included. It was found that while turbulence yields an increase of the mean blackbody radiation intensity, it causes a decrease of the time-averaged Planck-mean absorption coefficient. The absorption coefficient self-correlation is small in comparison with the temperature self-correlation, and the role of TRI in radiative emission is more important than in radiative absorption. The absorption coefficient-radiation intensity correlation is small, which supports the optically thin fluctuation approximation, and justifies the good predictions often achieved using the time-averaged RTE.

  5. Radiation statistics in homogeneous isotropic turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, C B; Coelho, P J [Mechanical Engineering Department, IDMEC/LAETA, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Malico, I [Physics Department, University of Evora, Rua Romao Ramalho, 59, 7000-671 Evora (Portugal)], E-mail: carlos.silva@ist.utl.pt, E-mail: imbm@uevora.pt, E-mail: pedro.coelho@ist.utl.pt

    2009-09-15

    An analysis of turbulence-radiation interaction (TRI) in statistically stationary (forced) homogeneous and isotropic turbulence is presented. A direct numerical simulation code was used to generate instantaneous turbulent scalar fields, and the radiative transfer equation (RTE) was solved to provide statistical data relevant in TRI. The radiation intensity is non-Gaussian and is not spatially correlated with any of the other turbulence or radiation quantities. Its power spectrum exhibits a power-law region with a slope steeper than the classical -5/3 law. The moments of the radiation intensity, Planck-mean and incident-mean absorption coefficients, and emission and absorption TRI correlations are calculated. The influence of the optical thickness of the medium, mean and variance of the temperature and variance of the molar fraction of the absorbing species is studied. Predictions obtained from the time-averaged RTE are also included. It was found that while turbulence yields an increase of the mean blackbody radiation intensity, it causes a decrease of the time-averaged Planck-mean absorption coefficient. The absorption coefficient self-correlation is small in comparison with the temperature self-correlation, and the role of TRI in radiative emission is more important than in radiative absorption. The absorption coefficient-radiation intensity correlation is small, which supports the optically thin fluctuation approximation, and justifies the good predictions often achieved using the time-averaged RTE.

  6. Homogeneity and microstructure study of Gd2O3-UO2 pellets

    International Nuclear Information System (INIS)

    Pan Ying; Gao Dihua; Guo Yibai; Zhu Shuming

    1994-10-01

    The microstructure of Gd 2 O 3 -UO 2 pellets (0∼10 wt%) prepared in different conditions, the homogeneity distribution of Gd 2 O 3 in the pellets and the lattice parameter of solid solution are studied by metalloscope, WDS, EDAX, SEM-image processing system, XRD and image analyzer. The theoretical density has been calculated. The effect of size and content of Gd 2 O 3 particles, the blend process, the sintering temperature and time, and the sintering atmosphere on the microstructure of Gd 2 O 3 pellets and the homogeneity of Gd 2 O 3 in the pellets are studied. (16 refs., 10 figs., 8 tabs.)

  7. Endoscopy and homogeneous-heterogeneous reactions in MHD radiative peristaltic activity of Ree-Eyring fluid

    Science.gov (United States)

    Hayat, Tasawar; Akram, Javaria; Alsaedi, Ahmed; Zahir, Hina

    2018-03-01

    Endoscopic and homogeneous-heterogeneous reactions in MHD peristalsis of Ree-Eyring fluid are addressed. Mathematical modeling and analysis have been performed by utilizing cylindrical coordinates. Nonlinear thermal radiation is present. Impact of slip boundary conditions on temperature and velocity on outer tube are taken into consideration. Lubrication approach is employed. The nonlinear system is executed numerically for solutions of velocity, temperature and concentration. Graphical results are obtained to predict physical interpretation of various embedded parameters. It is noted that homogeneous and heterogeneous reactions affect the concentration alternatively. Moreover Brinkman number rises the temperature and heat transfer coefficient whereas thermal slip drops temperature and heat transfer rate.

  8. Analysis of a homogenous and heterogeneous stylized half core of a CANDU reactor

    Energy Technology Data Exchange (ETDEWEB)

    EL-Khawlani, Afrah [Physics Department, Sana' a (Yemen); Aziz, Moustafa [Nuclear and radiological regulatory authority, Cairo (Egypt); Ismail, Mahmud Yehia; Ellithi, Ali Yehia [Cairo Univ. (Egypt). Faculty of Science

    2015-03-15

    The MCNPX (Monte Carlo N-Particle Transport Code System) code has been used for modeling and simulation of a half core of CANDU (CANada Deuterium-Uranium) reactor, both homogenous and heterogeneous model for the reactor core are designed. The fuel is burnt in normal operation conditions of CANDU reactors. Natural uranium fuel is used in the model. The multiplication factor for homogeneous and heterogeneous reactor core is calculated and compared during fuel burnup. The concentration of both uranium and plutonium isotopes are analysed in the model. The flux and power distributions through channels are calculated.

  9. High-frequency homogenization for travelling waves in periodic media.

    Science.gov (United States)

    Harutyunyan, Davit; Milton, Graeme W; Craster, Richard V

    2016-07-01

    We consider high-frequency homogenization in periodic media for travelling waves of several different equations: the wave equation for scalar-valued waves such as acoustics; the wave equation for vector-valued waves such as electromagnetism and elasticity; and a system that encompasses the Schrödinger equation. This homogenization applies when the wavelength is of the order of the size of the medium periodicity cell. The travelling wave is assumed to be the sum of two waves: a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω 1 plus a modulated Bloch carrier wave having crystal wavevector [Formula: see text] and frequency ω 2 . We derive effective equations for the modulating functions, and then prove that there is no coupling in the effective equations between the two different waves both in the scalar and the system cases. To be precise, we prove that there is no coupling unless ω 1 = ω 2 and [Formula: see text] where Λ =(λ 1 λ 2 …λ d ) is the periodicity cell of the medium and for any two vectors [Formula: see text] the product a ⊙ b is defined to be the vector ( a 1 b 1 , a 2 b 2 ,…, a d b d ). This last condition forces the carrier waves to be equivalent Bloch waves meaning that the coupling constants in the system of effective equations vanish. We use two-scale analysis and some new weak-convergence type lemmas. The analysis is not at the same level of rigour as that of Allaire and co-workers who use two-scale convergence theory to treat the problem, but has the advantage of simplicity which will allow it to be easily extended to the case where there is degeneracy of the Bloch eigenvalue.

  10. Giant asymmetry of separation and homogenization processes in solid 3He-4He solutions

    International Nuclear Information System (INIS)

    Grigor'ev, V.N.; Majdanov, V.A.; Penzev, A.A.; Polev, A.V.; Rubets, S.P.; Rudavskij, Eh.Ya.; Rybalko, A.S.; Syrnikov, E.V.

    2005-01-01

    The kinetics of the processes of separation and homogenization of solid 3 He- 4 He solutions is compared by using the precision barometry. The experiments were made with the initial specimens of three types: weak 3 He- 4 He and 4 He- 3 He solutions and concentrated 3 He- 4 He ones. It is found that the homogenization rate at the initial stage may be more than 500 times higher that the rate of separation. This is the case for all types of the solutions studied. The appreciable rate of phase separation in the concentrated solutions where, according to the modern concepts, impurity atoms in quantum crystals should be localized, suggests that in such conditions there is a new unknown mechanism of mass-transfer, while the fast homogenization points to a nondiffusion nature of the process

  11. Homogenization analysis of invasion dynamics in heterogeneous landscapes with differential bias and motility.

    Science.gov (United States)

    Yurk, Brian P

    2018-07-01

    Animal movement behaviors vary spatially in response to environmental heterogeneity. An important problem in spatial ecology is to determine how large-scale population growth and dispersal patterns emerge within highly variable landscapes. We apply the method of homogenization to study the large-scale behavior of a reaction-diffusion-advection model of population growth and dispersal. Our model includes small-scale variation in the directed and random components of movement and growth rates, as well as large-scale drift. Using the homogenized model we derive simple approximate formulas for persistence conditions and asymptotic invasion speeds, which are interpreted in terms of residence index. The homogenization results show good agreement with numerical solutions for environments with a high degree of fragmentation, both with and without periodicity at the fast scale. The simplicity of the formulas, and their connection to residence index make them appealing for studying the large-scale effects of a variety of small-scale movement behaviors.

  12. Parameterizing the competition between homogeneous and heterogeneous freezing in cirrus cloud formation – monodisperse ice nuclei

    Directory of Open Access Journals (Sweden)

    D. Barahona

    2009-01-01

    Full Text Available We present a parameterization of cirrus cloud formation that computes the ice crystal number and size distribution under the presence of homogeneous and heterogeneous freezing. The parameterization is very simple to apply and is derived from the analytical solution of the cloud parcel equations, assuming that the ice nuclei population is monodisperse and chemically homogeneous. In addition to the ice distribution, an analytical expression is provided for the limiting ice nuclei number concentration that suppresses ice formation from homogeneous freezing. The parameterization is evaluated against a detailed numerical parcel model, and reproduces numerical simulations over a wide range of conditions with an average error of 6±33%. The parameterization also compares favorably against other formulations that require some form of numerical integration.

  13. A Modified Homogeneous Balance Method and Its Applications

    International Nuclear Information System (INIS)

    Liu Chunping

    2011-01-01

    A modified homogeneous balance method is proposed by improving some key steps in the homogeneous balance method. Bilinear equations of some nonlinear evolution equations are derived by using the modified homogeneous balance method. Generalized Boussinesq equation, KP equation, and mKdV equation are chosen as examples to illustrate our method. This approach is also applicable to a large variety of nonlinear evolution equations. (general)

  14. A numerical homogenization method for heterogeneous, anisotropic elastic media based on multiscale theory

    KAUST Repository

    Gao, Kai

    2015-06-05

    The development of reliable methods for upscaling fine-scale models of elastic media has long been an important topic for rock physics and applied seismology. Several effective medium theories have been developed to provide elastic parameters for materials such as finely layered media or randomly oriented or aligned fractures. In such cases, the analytic solutions for upscaled properties can be used for accurate prediction of wave propagation. However, such theories cannot be applied directly to homogenize elastic media with more complex, arbitrary spatial heterogeneity. Therefore, we have proposed a numerical homogenization algorithm based on multiscale finite-element methods for simulating elastic wave propagation in heterogeneous, anisotropic elastic media. Specifically, our method used multiscale basis functions obtained from a local linear elasticity problem with appropriately defined boundary conditions. Homogenized, effective medium parameters were then computed using these basis functions, and the approach applied a numerical discretization that was similar to the rotated staggered-grid finite-difference scheme. Comparisons of the results from our method and from conventional, analytical approaches for finely layered media showed that the homogenization reliably estimated elastic parameters for this simple geometry. Additional tests examined anisotropic models with arbitrary spatial heterogeneity in which the average size of the heterogeneities ranged from several centimeters to several meters, and the ratio between the dominant wavelength and the average size of the arbitrary heterogeneities ranged from 10 to 100. Comparisons to finite-difference simulations proved that the numerical homogenization was equally accurate for these complex cases.

  15. Economical preparation of extremely homogeneous nuclear accelerator targets

    International Nuclear Information System (INIS)

    Maier, H.J.

    1983-01-01

    Techniques for target preparation with a minimum consumption of isotopic material are described. The rotating substrate method, which generates extremely homogeneous targets, is discussed in some detail

  16. Mechanized syringe homogenization of human and animal tissues.

    Science.gov (United States)

    Kurien, Biji T; Porter, Andrew C; Patel, Nisha C; Kurono, Sadamu; Matsumoto, Hiroyuki; Scofield, R Hal

    2004-06-01

    Tissue homogenization is a prerequisite to any fractionation schedule. A plethora of hands-on methods are available to homogenize tissues. Here we report a mechanized method for homogenizing animal and human tissues rapidly and easily. The Bio-Mixer 1200 (manufactured by Innovative Products, Inc., Oklahoma City, OK) utilizes the back-and-forth movement of two motor-driven disposable syringes, connected to each other through a three-way stopcock, to homogenize animal or human tissue. Using this method, we were able to homogenize human or mouse tissues (brain, liver, heart, and salivary glands) in 5 min. From sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and a matrix-assisted laser desorption/ionization time-of-flight mass spectrometric enzyme assay for prolidase, we have found that the homogenates obtained were as good or even better than that obtained used a manual glass-on-Teflon (DuPont, Wilmington, DE) homogenization protocol (all-glass tube and Teflon pestle). Use of the Bio-Mixer 1200 to homogenize animal or human tissue precludes the need to stay in the cold room as is the case with the other hands-on homogenization methods available, in addition to freeing up time for other experiments.

  17. Etude de l'impact de la variation de la température sur les activités ...

    African Journals Online (AJOL)

    Etude de l'impact de la variation de la température sur les activités microbiennes : application à une population de Listeria monocytogenes CIP 7831, Listeria monocytogenes Scott A CIP 103575 et Escherichia coli ATCC 25922.

  18. Bio-metric study of pig karyotype; Etude biometrique du caryotype du porc

    Energy Technology Data Exchange (ETDEWEB)

    Haag, J; Lacourly, N; Nizza, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    This study has a twofold purpose, the former is to determine the swine karyotype as accurately as possible, the latter is to try and develop a method of automatic classification and to show its possibilities and limits. (authors) [French] Cette etude a un double objet: d'une part, de definir de la facon aussi precise que possible le caryotype du porc et d'autre part, de tenter une methode de classification automatique et d'en montrer les possibilites ainsi que les limites. (auteurs)

  19. The Raychaudhuri equation in homogeneous cosmologies

    International Nuclear Information System (INIS)

    Albareti, F.D.; Cembranos, J.A.R.; Cruz-Dombriz, A. de la; Dobado, A.

    2014-01-01

    In this work we address the issue of studying the conditions required to guarantee the Focusing Theorem for both null and timelike geodesic congruences by using the Raychaudhuri equation. In particular we study the case of Friedmann-Robertson-Walker as well as more general Bianchi Type I spacetimes. The fulfillment of the Focusing Theorem is mandatory in small scales since it accounts for the attractive character of gravity. However, the Focusing Theorem is not satisfied at cosmological scales due to the measured negative deceleration parameter. The study of the conditions needed for congruences convergence is not only relevant at the fundamental level but also to derive the viability conditions to be imposed on extended theories of gravity describing the different expansion regimes of the universe. We illustrate this idea for f(R) gravity theories

  20. Pi overlapping ring systems contained in a homogeneous assay: a novel homogeneous assay for antigens

    Science.gov (United States)

    Kidwell, David A.

    1993-05-01

    A novel immunoassay, Pi overlapping ring systems contained in a homogeneous assay (PORSCHA), is described. This assay relies upon the change in fluorescent spectral properties that pyrene and its derivatives show with varying concentration. Because antibodies and other biomolecules can bind two molecules simultaneously, they can change the local concentration of the molecules that they bind. This concentration change may be detected spectrally as a change in the fluorescence emission wavelength of an appropriately labeled biomolecule. Several tests of PORSCHA have been performed which demonstrate this principle. For example: with streptavidin as the binding biomolecule and a biotin labeled pyrene derivative, the production of the excimer emitting at 470 nm is observed. Without the streptavidin present, only the monomer emitting at 378 and 390 nm is observed. The ratio of monomer to excimer provides the concentration of unlabeled biotin in the sample. Approximately 1 ng/mL of biotin may be detected with this system using a 50 (mu) l sample (2 X 10-16 moles biotin). The principles behind PORSCHA, the results with the streptavidin/biotin system are discussed and extensions of the PORSCHA concept to antibodies as the binding partner and DNA in homogeneous assays are suggested.

  1. On integral representation, relaxation and homogenization for unbounded functionals

    International Nuclear Information System (INIS)

    Carbone, L.; De Arcangelis, R.

    1997-01-01

    A theory of integral representation, relaxation and homogenization for some types of variational functionals taking extended real values and possibly being not finite also on large classes of regular functions is presented. Some applications to gradient constrained relaxation and homogenization problems are given

  2. Non-linear waves in heterogeneous elastic rods via homogenization

    KAUST Repository

    Quezada de Luna, Manuel

    2012-03-01

    We consider the propagation of a planar loop on a heterogeneous elastic rod with a periodic microstructure consisting of two alternating homogeneous regions with different material properties. The analysis is carried out using a second-order homogenization theory based on a multiple scale asymptotic expansion. © 2011 Elsevier Ltd. All rights reserved.

  3. Is it possible to homogenize resonant chiral metamaterials ?

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Menzel, Christoph; Rockstuhl, Carsten

    2010-01-01

    Homogenization of metamaterials is very important as it makes possible description in terms of effective parameters. In this contribution we consider the homogenization of chiral metamaterials. We show that for some metamaterials there is an optimal meta-atom size which depends on the coupling...

  4. Large-scale Homogenization of Bulk Materials in Mammoth Silos

    NARCIS (Netherlands)

    Schott, D.L.

    2004-01-01

    This doctoral thesis concerns the large-scale homogenization of bulk materials in mammoth silos. The objective of this research was to determine the best stacking and reclaiming method for homogenization in mammoth silos. For this purpose a simulation program was developed to estimate the

  5. Homogeneous Buchberger algorithms and Sullivant's computational commutative algebra challenge

    DEFF Research Database (Denmark)

    Lauritzen, Niels

    2005-01-01

    We give a variant of the homogeneous Buchberger algorithm for positively graded lattice ideals. Using this algorithm we solve the Sullivant computational commutative algebra challenge.......We give a variant of the homogeneous Buchberger algorithm for positively graded lattice ideals. Using this algorithm we solve the Sullivant computational commutative algebra challenge....

  6. Square Helmholtz coil with homogeneous field for magnetic measurement of longer HTS tapes

    Energy Technology Data Exchange (ETDEWEB)

    Alamgir, A.K.M. [Applied Superconductivity Research Center, Department of Physics, Building Li Zhai, Room 209, Tsinghua University, Beijing 100084 (China)]. E-mail: alam643@hotmail.com; Fang, J. [Applied Superconductivity Research Center, Department of Physics, Building Li Zhai, Room 209, Tsinghua University, Beijing 100084 (China); Gu, C. [Applied Superconductivity Research Center, Department of Physics, Building Li Zhai, Room 209, Tsinghua University, Beijing 100084 (China); Han, Z. [Applied Superconductivity Research Center, Department of Physics, Building Li Zhai, Room 209, Tsinghua University, Beijing 100084 (China)

    2005-08-01

    Magnetic ac loss measurement of HTS tapes and films at various magnetic field orientations becomes a crucial issue from the view point of measurement precision. In principle, due to tiny loss component and anisotropic properties, longer HTS sample subjected to very good homogeneous field could facilitate the accuracy of this kind of measurement. We investigated field profile of Helmholtz coils with square winding as a magnetizer for HTS tape and films. It is found that square winding exhibits better field-homogeneity than that of conventional circular winding with the similar coil dimensions for ideal condition. Being apart from ideal condition, we investigated field profile of square Helmholtz coil with various combinations of coil parameters and made a conclusion for the best combination based on the field homogeneity and field intensity. The design also provides noise reduction facilities by allowing compact and identical pick up-compensation coil arrangement. In addition, we optimized the final design of Helmholtz coil to compensate the influence of difficulties in square winding on the field distribution. Finally, as small as 0.5% field variation was estimated for 50 mm long sample to be magnetized under a proper combination of fabrication parameters. Investigation of field homogeneity, noise effect and a practical design of square Helmholtz coil as a pick-up coil based magnetizer will be reported.

  7. Effective production of bioenergy from marine Chlorella sp. by high-pressure homogenization

    Directory of Open Access Journals (Sweden)

    Woon Yong Choi

    2016-01-01

    Full Text Available This study investigated the use of a high-pressure homogenization process for the production of high shear stress on Chlorella sp. cells in order to effectively degrade their cell walls. The high-pressure homogenization process was conducted by using various pressure conditions in the range of 68.94–275.78 MPa with different numbers of repeated cycles. The optimal high-pressure homogenization pretreatment conditions were found to be two cycles at a pressure of 206.84 MPa, which provided an extraction yield of 20.35% (w/w total cellular lipids. In addition, based on the confocal microscopic images of Chlorella sp. cells stained by using nile red, the walls of Chlorella sp. cells were disrupted more effectively using this process when compared with the disruption achieved by conventional lipid-extraction processes. By using the by-product of Chlorella sp., 47.3% ethanol was obtained from Saccharomyces cerevisiae cultures. These results showed that the high-pressure homogenization process efficiently hydrolysed this marine resource for subsequent bioethanol production by using only water.

  8. Square Helmholtz coil with homogeneous field for magnetic measurement of longer HTS tapes

    International Nuclear Information System (INIS)

    Alamgir, A.K.M.; Fang, J.; Gu, C.; Han, Z.

    2005-01-01

    Magnetic ac loss measurement of HTS tapes and films at various magnetic field orientations becomes a crucial issue from the view point of measurement precision. In principle, due to tiny loss component and anisotropic properties, longer HTS sample subjected to very good homogeneous field could facilitate the accuracy of this kind of measurement. We investigated field profile of Helmholtz coils with square winding as a magnetizer for HTS tape and films. It is found that square winding exhibits better field-homogeneity than that of conventional circular winding with the similar coil dimensions for ideal condition. Being apart from ideal condition, we investigated field profile of square Helmholtz coil with various combinations of coil parameters and made a conclusion for the best combination based on the field homogeneity and field intensity. The design also provides noise reduction facilities by allowing compact and identical pick up-compensation coil arrangement. In addition, we optimized the final design of Helmholtz coil to compensate the influence of difficulties in square winding on the field distribution. Finally, as small as 0.5% field variation was estimated for 50 mm long sample to be magnetized under a proper combination of fabrication parameters. Investigation of field homogeneity, noise effect and a practical design of square Helmholtz coil as a pick-up coil based magnetizer will be reported

  9. Analysis of the premeability characteristics along rough-walled fractures using a homogenization method

    International Nuclear Information System (INIS)

    Chae, Byung Gon; Choi, Jung Hae; Ichikawa, Yasuaki; Seo, Yong Seok

    2012-01-01

    To compute a permeability coefficient along a rough fracture that takes into account the fracture geometry, this study performed detailed measurements of fracture roughness using a confocal laser scanning microscope, a quantitative analysis of roughness using a spectral analysis, and a homogenization analysis to calculate the permeability coefficient on the microand macro-scale. The homogenization analysis is a type of perturbation theory that characterizes the behavior of microscopically inhomogeneous material with a periodic boundary condition in the microstructure. Therefore, it is possible to analyze accurate permeability characteristics that are represented by the local effect of the fracture geometry. The Cpermeability coefficients that are calculated using the homogenization analysis for each rough fracture model exhibit an irregular distribution and do not follow the relationship of the cubic law. This distribution suggests that the permeability characteristics strongly depend on the geometric conditions of the fractures, such as the roughness and the aperture variation. The homogenization analysis may allow us to produce more accurate results than are possible with the preexisting equations for calculating permeability.

  10. Verification of homogenization in fast critical assembly analyses

    International Nuclear Information System (INIS)

    Chiba, Go

    2006-01-01

    In the present paper, homogenization procedures for fast critical assembly analyses are investigated. Errors caused by homogenizations are evaluated by the exact perturbation theory. In order to obtain reference solutions, three-dimensional plate-wise transport calculations are performed. It is found that the angular neutron flux along plate boundaries has a significant peak in the fission source energy range. To treat this angular dependence accurately, the double-Gaussian Chebyshev angular quadrature set with S 24 is applied. It is shown that the difference between the heterogeneous leakage theory and the homogeneous theory is negligible, and that transport cross sections homogenized with neutron flux significantly underestimate neutron leakage. The error in criticality caused by a homogenization is estimated at about 0.1%Δk/kk' in a small fast critical assembly. In addition, the neutron leakage is overestimated by both leakage theories when sodium plates in fuel lattices are voided. (author)

  11. Cosmic homogeneity: a spectroscopic and model-independent measurement

    Science.gov (United States)

    Gonçalves, R. S.; Carvalho, G. C.; Bengaly, C. A. P., Jr.; Carvalho, J. C.; Bernui, A.; Alcaniz, J. S.; Maartens, R.

    2018-03-01

    Cosmology relies on the Cosmological Principle, i.e. the hypothesis that the Universe is homogeneous and isotropic on large scales. This implies in particular that the counts of galaxies should approach a homogeneous scaling with volume at sufficiently large scales. Testing homogeneity is crucial to obtain a correct interpretation of the physical assumptions underlying the current cosmic acceleration and structure formation of the Universe. In this letter, we use the Baryon Oscillation Spectroscopic Survey to make the first spectroscopic and model-independent measurements of the angular homogeneity scale θh. Applying four statistical estimators, we show that the angular distribution of galaxies in the range 0.46 < z < 0.62 is consistent with homogeneity at large scales, and that θh varies with redshift, indicating a smoother Universe in the past. These results are in agreement with the foundations of the standard cosmological paradigm.

  12. Turbulent Diffusion in Non-Homogeneous Environments

    Science.gov (United States)

    Diez, M.; Redondo, J. M.; Mahjoub, O. B.; Sekula, E.

    2012-04-01

    Many experimental studies have been devoted to the understanding of non-homogeneous turbulent dynamics. Activity in this area intensified when the basic Kolmogorov self-similar theory was extended to two-dimensional or quasi 2D turbulent flows such as those appearing in the environment, that seem to control mixing [1,2]. The statistical description and the dynamics of these geophysical flows depend strongly on the distribution of long lived organized (coherent) structures. These flows show a complex topology, but may be subdivided in terms of strongly elliptical domains (high vorticity regions), strong hyperbolic domains (deformation cells with high energy condensations) and the background turbulent field of moderate elliptic and hyperbolic characteristics. It is of fundamental importance to investigate the different influence of these topological diverse regions. Relevant geometrical information of different areas is also given by the maximum fractal dimension, which is related to the energy spectrum of the flow. Using all the available information it is possible to investigate the spatial variability of the horizontal eddy diffusivity K(x,y). This information would be very important when trying to model numerically the behaviour in time of the oil spills [3,4] There is a strong dependence of horizontal eddy diffusivities with the Wave Reynolds number as well as with the wind stress measured as the friction velocity from wind profiles measured at the coastline. Natural sea surface oily slicks of diverse origin (plankton, algae or natural emissions and seeps of oil) form complicated structures in the sea surface due to the effects of both multiscale turbulence and Langmuir circulation. It is then possible to use the topological and scaling analysis to discriminate the different physical sea surface processes. We can relate higher orden moments of the Lagrangian velocity to effective diffusivity in spite of the need to calibrate the different regions determining the

  13. The formation of scientists and technicians at the 'Centre d'Etudes Nucleaires' at Saclay

    International Nuclear Information System (INIS)

    Debiesse, J.

    1958-01-01

    The considerable needs in research workers and scientists which are asked by the nuclear energy obliged the Commissariat a l'Energie atomique to deal with a particular effort to increase the quantitative and qualitative formation of scientists. Most various ways have been used. 1- A National Institute of Nuclear Sciences and Nuclear Techniques was created, by a joint decree of the Prime Minister and the Minister for National Education (june 18, 1957). This Institute of Higher Teaching (250 students) indulges in the following matters: atomic engineering, quantum mechanics, theory and technic of particle accelerators, special metallurgy, radiobiology, thermic and mechanics of fluids. 2- An associated centre of the 'Conservatoire National des Arts et Metiers' was created (200 students) for technical assistants, drawers, etc. 3- In contribution with both electronic industry and Ministry of Work, the Centre d'Etudes Nucleaires contributes to an accelerated formation of technical assistants into Professional Centres. Conclusion: Training of scientists and research workers is one of the most important activities of the Centre d'Etudes Nucleaires de Saclay. Without losing its technical efficiency, it has supplied and varied means adapted to the various purposes that we shall reach. (author) [fr

  14. Chemical zoning and homogenization of olivines in ordinary chondrites and implications for thermal histories of chondrules

    Science.gov (United States)

    Miyamoto, Masamichi; Mckay, David S.; Mckay, Gordon A.; Duke, Michael B.

    1986-01-01

    The extent and degree of homogenization of chemical zoning of olivines in type 3 ordinary chondrites is studied in order to obtain some constraints on cooling histories of chondrites. Based on Mg-Fe and CaO zoning, olivines in type 3 chondrites are classified into four types. A single chondrule usually contains olivines with the same type of zoning. Microporphyritic olivines show all four zoning types. Barred olivines usually show almost homogenized chemical zoning. The cooling rates or burial depths needed to homogenize the chemical zoning are calculated by solving the diffusion equation, using the zoning profiles as an initial condition. Mg-Fe zoning of olivine may be altered during initial cooling, whereas CaO zoning is hardly changed. Barred olivines may be homogenized during initial cooling because their size is relatively small. To simulated microporphyritic olivine chondrules, cooling from just below the liquidus at moderately high rates is preferable to cooling from above the liquidus at low rates. For postaccumulation metamorphism of type 3 chondrites to keep Mg-Fe zoning unaltered, the maximum metamorphic temperature must be less than about 400 C if cooling rates based on Fe-Ni data are assumed. Calculated cooling rates for both Fa and CaO homogenization are consistent with those by Fe-Ni data for type 4 chondrites. A hot ejecta blanket several tens of meters thick on the surface of a parent body is sufficient to homogenize Mg-Fe zoning if the temperature of the blanket is 600-700 C. Burial depths for petrologic types of ordinary chondrites in a parent body heated by Al-26 are broadly consistent with those previously proposed.

  15. Development of dynamic explicit crystallographic homogenization finite element analysis code to assess sheet metal formability

    International Nuclear Information System (INIS)

    Nakamura, Yasunori; Tam, Nguyen Ngoc; Ohata, Tomiso; Morita, Kiminori; Nakamachi, Eiji

    2004-01-01

    The crystallographic texture evolution induced by plastic deformation in the sheet metal forming process has a great influence on its formability. In the present study, a dynamic explicit finite element (FE) analysis code is newly developed by introducing a crystallographic homogenization method to estimate the polycrystalline sheet metal formability, such as the extreme thinning and 'earing'. This code can predict the plastic deformation induced texture evolution at the micro scale and the plastic anisotropy at the macro scale, simultaneously. This multi-scale analysis can couple the microscopic crystal plasticity inhomogeneous deformation with the macroscopic continuum deformation. In this homogenization process, the stress at the macro scale is defined by the volume average of those of the corresponding microscopic crystal aggregations in satisfying the equation of motion and compatibility condition in the micro scale 'unit cell', where the periodicity of deformation is satisfied. This homogenization algorithm is implemented in the conventional dynamic explicit finite element code by employing the updated Lagrangian formulation and the rate type elastic/viscoplastic constitutive equation.At first, it has been confirmed through a texture evolution analyses in cases of typical deformation modes that Taylor's 'constant strain homogenization algorithm' yields extreme concentration toward the preferred crystal orientations compared with our homogenization one. Second, we study the plastic anisotropy effects on 'earing' in the hemispherical cup deep drawing process of pure ferrite phase sheet metal. By the comparison of analytical results with those of Taylor's assumption, conclusions are drawn that the present newly developed dynamic explicit crystallographic homogenization FEM shows more reasonable prediction of plastic deformation induced texture evolution and plastic anisotropy at the macro scale

  16. Parametric decay instabilities in an infinite, homogeneous, weakly anisotropic plasma

    International Nuclear Information System (INIS)

    Grandal, B.

    1976-01-01

    The parametric decay of a transverse electromagnetic (em) wave with a frequency close to, but larger than, the electron plasma frequency is investigated for an infinite, homogeneous, weakly magnetoactive plasma. A two-component fluid description is employed, and the damping of the linear plasma waves is introduced phenomenologically to include both Landau and collisional damping. The transverse em wave will decay into a longitudinal electron plasma wave and an em ion-acoustic wave. Only the latter wave is assumed to be affected by the weak, constant magnetic field. The threshold expression for growth of electron plasma waves is equal to that of the isotropic plasma when the em ion-acoustic wave's direction of propagation lies inside a wide double cone, whose axis is along the constant magnetic field. When the em ion-acoustic wave propagates outside this double cone, an additional factor, which depends directly upon the magnetic field, appears in the threshold expression. This factor can, under certain conditions, reduce the threshold for growth of electron plasma waves below that of the isotropic plasma

  17. Dynamic control of a homogeneous charge compression ignition engine

    Science.gov (United States)

    Duffy, Kevin P [Metamora, IL; Mehresh, Parag [Peoria, IL; Schuh, David [Peoria, IL; Kieser, Andrew J [Morton, IL; Hergart, Carl-Anders [Peoria, IL; Hardy, William L [Peoria, IL; Rodman, Anthony [Chillicothe, IL; Liechty, Michael P [Chillicothe, IL

    2008-06-03

    A homogenous charge compression ignition engine is operated by compressing a charge mixture of air, exhaust and fuel in a combustion chamber to an autoignition condition of the fuel. The engine may facilitate a transition from a first combination of speed and load to a second combination of speed and load by changing the charge mixture and compression ratio. This may be accomplished in a consecutive engine cycle by adjusting both a fuel injector control signal and a variable valve control signal away from a nominal variable valve control signal. Thereafter in one or more subsequent engine cycles, more sluggish adjustments are made to at least one of a geometric compression ratio control signal and an exhaust gas recirculation control signal to allow the variable valve control signal to be readjusted back toward its nominal variable valve control signal setting. By readjusting the variable valve control signal back toward its nominal setting, the engine will be ready for another transition to a new combination of engine speed and load.

  18. Homogeneous Charge Compression Ignition Combustion: Challenges and Proposed Solutions

    Directory of Open Access Journals (Sweden)

    Mohammad Izadi Najafabadi

    2013-01-01

    Full Text Available Engine and car manufacturers are experiencing the demand concerning fuel efficiency and low emissions from both consumers and governments. Homogeneous charge compression ignition (HCCI is an alternative combustion technology that is cleaner and more efficient than the other types of combustion. Although the thermal efficiency and NOx emission of HCCI engine are greater in comparison with traditional engines, HCCI combustion has several main difficulties such as controlling of ignition timing, limited power output, and weak cold-start capability. In this study a literature review on HCCI engine has been performed and HCCI challenges and proposed solutions have been investigated from the point view of Ignition Timing that is the main problem of this engine. HCCI challenges are investigated by many IC engine researchers during the last decade, but practical solutions have not been presented for a fully HCCI engine. Some of the solutions are slow response time and some of them are technically difficult to implement. So it seems that fully HCCI engine needs more investigation to meet its mass-production and the future research and application should be considered as part of an effort to achieve low-temperature combustion in a wide range of operating conditions in an IC engine.

  19. Information Geometry Formalism for the Spatially Homogeneous Boltzmann Equation

    Directory of Open Access Journals (Sweden)

    Bertrand Lods

    2015-06-01

    Full Text Available Information Geometry generalizes to infinite dimension by modeling the tangent space of the relevant manifold of probability densities with exponential Orlicz spaces. We review here several properties of the exponential manifold on a suitable set Ɛ of mutually absolutely continuous densities. We study in particular the fine properties of the Kullback-Liebler divergence in this context. We also show that this setting is well-suited for the study of the spatially homogeneous Boltzmann equation if Ɛ is a set of positive densities with finite relative entropy with respect to the Maxwell density. More precisely, we analyze the Boltzmann operator in the geometric setting from the point of its Maxwell’s weak form as a composition of elementary operations in the exponential manifold, namely tensor product, conditioning, marginalization and we prove in a geometric way the basic facts, i.e., the H-theorem. We also illustrate the robustness of our method by discussing, besides the Kullback-Leibler divergence, also the property of Hyvärinen divergence. This requires us to generalize our approach to Orlicz–Sobolev spaces to include derivatives.

  20. Characterization of unsaturated hydraulic parameters for homogeneous and heterogeneous soils

    Energy Technology Data Exchange (ETDEWEB)

    Wildenschild, Dorthe

    1997-09-01

    Application of numerical models for predicting future spreading of contaminants into ground water aquifers is dependent on appropriate characterization of the soil hydraulic properties controlling flow and transport in the unsaturated zone. This thesis reviews the current knowledge on two aspects of characterization of unsaturated hydraulic parameters; estimation of the basic hydraulic parameters for homogeneous soils and statistical representation of heterogeneity for spatially variable soils. The retention characteristic is traditionally measured using steady-state procedures, but new ideas based on dynamic techniques have been developed that reduce experimental efforts and that produce retention curves which compare to those measured by traditional techniques. The unsaturated hydraulic conductivity is difficult to establish by steady-state procedures, and extensive research efforts have been focused on alternative methods that are based on inverse estimation. The inverse methods have commonly been associated with problems of numerical instability and ill-posedness of the parameter estimates, but recent investigations have shown that the uniqueness of parameter estimates can be improved by including additional, independent information on, for instance, the retention characteristic. Also, uniqueness may be improved by careful selection of experimental conditions are parametric functions. (au) 234 refs.

  1. Negative-energy waves in a magnetized, homogeneous plasma

    International Nuclear Information System (INIS)

    Correa-Restrepo, D.; Pfirsch, D.

    1991-09-01

    The general expression for the second wave energy of a Vlasov-Maxwell system derived by Morrison and Pfirsch is evaluated here for the case of a magnetized, homogeneous plasma. It is again shown that negative-energy waves (which could become nonlinearly unstable and cause anomalous transport) exist for any deviation from monotonicity and/or any (however small) anisotropy in the equilibrium distribution function of any of the particle species. The partly unexpected and particularly interesting feature of the results is that, contrary to the proof of Morrison and Pfirsch, no restricting condition has to be imposed on the perpendicular wave number k perpendicular to of the perturbation (i.e. large k perpendicular to is not required). Finite-gyroradius effects are therefore not expected to improve the situation. Anisotropy alone would, however, impose a restriction on k z , the parallel wave number, relating it to the gyroradius. As far as distribution functions with v z δf v (0) /δv z > 0 in some region of v-space are concerned, however, this result agrees with a result found by Pfirsch and Morrison within the framework of drift-kinetic theory. (orig.)

  2. Homogenization of a Conductive-Radiative Heat Transfer Problem

    Directory of Open Access Journals (Sweden)

    Habibi Zakaria

    2012-04-01

    Full Text Available This paper focuses on the contribution of the second order corrector in periodic homogenization applied to a conductive-radiative heat transfer problem. Especially, for a heat conduction problem in a periodically perforated domain with a non-local boundary condition modelling the radiative heat transfer, if this model contains an oscillating thermal source and a thermal exchange with the perforations, the second order corrector helps us to model the gradients which appear between the source area and the perforations. Ce papier est consacré à montrer l’influence du correcteur de second ordre en homogénéisation périodique. Dans l’homogénéisation d’un problème de conduction rayonnement dans un domaine périodiquement perforé par plusieurs trous, on peut voir une contribution non négligeable de ce correcteur lors de la présence d’une source thermique oscillante et d’un échange thermique dans les perforations. Ce correcteur nous permet de modéliser les gradients qui apparaissent entre la zone de la source thermique et les perforations.

  3. A novel grain cluster-based homogenization scheme

    International Nuclear Information System (INIS)

    Tjahjanto, D D; Eisenlohr, P; Roters, F

    2010-01-01

    An efficient homogenization scheme, termed the relaxed grain cluster (RGC), for elasto-plastic deformations of polycrystals is presented. The scheme is based on a generalization of the grain cluster concept. A volume element consisting of eight (= 2 × 2 × 2) hexahedral grains is considered. The kinematics of the RGC scheme is formulated within a finite deformation framework, where the relaxation of the local deformation gradient of each individual grain is connected to the overall deformation gradient by the, so-called, interface relaxation vectors. The set of relaxation vectors is determined by the minimization of the constitutive energy (or work) density of the overall cluster. An additional energy density associated with the mismatch at the grain boundaries due to relaxations is incorporated as a penalty term into the energy minimization formulation. Effectively, this penalty term represents the kinematical condition of deformation compatibility at the grain boundaries. Simulations have been performed for a dual-phase grain cluster loaded in uniaxial tension. The results of the simulations are presented and discussed in terms of the effective stress–strain response and the overall deformation anisotropy as functions of the penalty energy parameters. In addition, the prediction of the RGC scheme is compared with predictions using other averaging schemes, as well as to the result of direct finite element (FE) simulation. The comparison indicates that the present RGC scheme is able to approximate FE simulation results of relatively fine discretization at about three orders of magnitude lower computational cost

  4. Homogeneous non-equilibrium two-phase critical flow model

    International Nuclear Information System (INIS)

    Schroeder, J.J.; Vuxuan, N.

    1987-01-01

    An important aspect of nuclear and chemical reactor safety is the ability to predict the maximum or critical mass flow rate from a break or leak in a pipe system. At the beginning of such a blowdown, if the stagnation condition of the fluid is subcooled or slightly saturated thermodynamic non-equilibrium exists in the downstream, e.g. the fluid becomes superheated to a degree determined by the liquid pressure. A simplified non-equilibrium model, explained in this report, is valid for rapidly decreasing pressure along the flow path. It presumes that fluid has to be superheated by an amount governed by physical principles before it starts to flash into steam. The flow is assumed to be homogeneous, i.e. the steam and liquid velocities are equal. An adiabatic flow calculation mode (Fanno lines) is employed to evaluate the critical flow rate for long pipes. The model is found to satisfactorily describe critical flow tests. Good agreement is obtained with the large scale Marviken tests as well as with small scale experiments. (orig.)

  5. Pattern and process of biotic homogenization in the New Pangaea.

    Science.gov (United States)

    Baiser, Benjamin; Olden, Julian D; Record, Sydne; Lockwood, Julie L; McKinney, Michael L

    2012-12-07

    Human activities have reorganized the earth's biota resulting in spatially disparate locales becoming more or less similar in species composition over time through the processes of biotic homogenization and biotic differentiation, respectively. Despite mounting evidence suggesting that this process may be widespread in both aquatic and terrestrial systems, past studies have predominantly focused on single taxonomic groups at a single spatial scale. Furthermore, change in pairwise similarity is itself dependent on two distinct processes, spatial turnover in species composition and changes in gradients of species richness. Most past research has failed to disentangle the effect of these two mechanisms on homogenization patterns. Here, we use recent statistical advances and collate a global database of homogenization studies (20 studies, 50 datasets) to provide the first global investigation of the homogenization process across major faunal and floral groups and elucidate the relative role of changes in species richness and turnover. We found evidence of homogenization (change in similarity ranging from -0.02 to 0.09) across nearly all taxonomic groups, spatial extent and grain sizes. Partitioning of change in pairwise similarity shows that overall change in community similarity is driven by changes in species richness. Our results show that biotic homogenization is truly a global phenomenon and put into question many of the ecological mechanisms invoked in previous studies to explain patterns of homogenization.

  6. Mitoxantrone removal by electrochemical method: A comparison of homogenous and heterogenous catalytic reactions

    Directory of Open Access Journals (Sweden)

    Abbas Jafarizad

    2017-08-01

    Full Text Available Background: Mitoxantrone (MXT is a drug for cancer therapy and a hazardous pharmaceutical to the environment which must be removed from contaminated waste streams. In this work, the removal of MXT by the electro-Fenton process over heterogeneous and homogenous catalysts is reported. Methods: The effects of the operational conditions (reaction medium pH, catalyst concentration and utilized current intensity were studied. The applied electrodes were carbon cloth (CC without any processing (homogenous process, graphene oxide (GO coated carbon cloth (GO/CC (homogenous process and Fe3O4@GO nanocomposite coated carbon cloth (Fe3O4@GO/CC (heterogeneous process. The characteristic properties of the electrodes were determined by atomic force microscopy (AFM, field emission scanning electron microscopy (FE-SEM and cathode polarization. MXT concentrations were determined by using ultraviolet-visible (UV-Vis spectrophotometer. Results: In a homogenous reaction, the high concentration of Fe catalyst (>0.2 mM decreased the MXT degradation rate. The results showed that the Fe3O4@GO/CC electrode included the most contact surface. The optimum operational conditions were pH 3.0 and current intensity of 450 mA which resulted in the highest removal efficiency (96.9% over Fe3O4@GO/CC electrode in the heterogeneous process compared with the other two electrodes in a homogenous process. The kinetics of the MXT degradation was obtained as a pseudo-first order reaction. Conclusion: The results confirmed the high potential of the developed method to purify contaminated wastewaters by MXT.

  7. Parameterizing the competition between homogeneous and heterogeneous freezing in ice cloud formation – polydisperse ice nuclei

    Directory of Open Access Journals (Sweden)

    D. Barahona

    2009-08-01

    Full Text Available This study presents a comprehensive ice cloud formation parameterization that computes the ice crystal number, size distribution, and maximum supersaturation from precursor aerosol and ice nuclei. The parameterization provides an analytical solution of the cloud parcel model equations and accounts for the competition effects between homogeneous and heterogeneous freezing, and, between heterogeneous freezing in different modes. The diversity of heterogeneous nuclei is described through a nucleation spectrum function which is allowed to follow any form (i.e., derived from classical nucleation theory or from observations. The parameterization reproduces the predictions of a detailed numerical parcel model over a wide range of conditions, and several expressions for the nucleation spectrum. The average error in ice crystal number concentration was −2.0±8.5% for conditions of pure heterogeneous freezing, and, 4.7±21% when both homogeneous and heterogeneous freezing were active. The formulation presented is fast and free from requirements of numerical integration.

  8. Homogenous polynomially parameter-dependent H∞ filter designs of discrete-time fuzzy systems.

    Science.gov (United States)

    Zhang, Huaguang; Xie, Xiangpeng; Tong, Shaocheng

    2011-10-01

    This paper proposes a novel H(∞) filtering technique for a class of discrete-time fuzzy systems. First, a novel kind of fuzzy H(∞) filter, which is homogenous polynomially parameter dependent on membership functions with an arbitrary degree, is developed to guarantee the asymptotic stability and a prescribed H(∞) performance of the filtering error system. Second, relaxed conditions for H(∞) performance analysis are proposed by using a new fuzzy Lyapunov function and the Finsler lemma with homogenous polynomial matrix Lagrange multipliers. Then, based on a new kind of slack variable technique, relaxed linear matrix inequality-based H(∞) filtering conditions are proposed. Finally, two numerical examples are provided to illustrate the effectiveness of the proposed approach.

  9. An iterative homogenization technique that preserves assembly core exchanges

    International Nuclear Information System (INIS)

    Mondot, Ph.; Sanchez, R.

    2003-01-01

    A new interactive homogenization procedure for reactor core calculations is proposed that requires iterative transport assembly and diffusion core calculations. At each iteration the transport solution of every assembly type is used to produce homogenized cross sections for the core calculation. The converged solution gives assembly fine multigroup transport fluxes that preserve macro-group assembly exchanges in the core. This homogenization avoids the periodic lattice-leakage model approximation and gives detailed assembly transport fluxes without need of an approximated flux reconstruction. Preliminary results are given for a one-dimensional core model. (authors)

  10. Hydrogen storage materials and method of making by dry homogenation

    Science.gov (United States)

    Jensen, Craig M.; Zidan, Ragaiy A.

    2002-01-01

    Dry homogenized metal hydrides, in particular aluminum hydride compounds, as a material for reversible hydrogen storage is provided. The reversible hydrogen storage material comprises a dry homogenized material having transition metal catalytic sites on a metal aluminum hydride compound, or mixtures of metal aluminum hydride compounds. A method of making such reversible hydrogen storage materials by dry doping is also provided and comprises the steps of dry homogenizing metal hydrides by mechanical mixing, such as be crushing or ball milling a powder, of a metal aluminum hydride with a transition metal catalyst. In another aspect of the invention, a method of powering a vehicle apparatus with the reversible hydrogen storage material is provided.

  11. Homogenization and structural topology optimization theory, practice and software

    CERN Document Server

    Hassani, Behrooz

    1999-01-01

    Structural topology optimization is a fast growing field that is finding numerous applications in automotive, aerospace and mechanical design processes. Homogenization is a mathematical theory with applications in several engineering problems that are governed by partial differential equations with rapidly oscillating coefficients Homogenization and Structural Topology Optimization brings the two concepts together and successfully bridges the previously overlooked gap between the mathematical theory and the practical implementation of the homogenization method. The book is presented in a unique self-teaching style that includes numerous illustrative examples, figures and detailed explanations of concepts. The text is divided into three parts which maintains the book's reader-friendly appeal.

  12. Homogenous reactor, elaborations, not released up to end

    International Nuclear Information System (INIS)

    Takibayev, Zh.S.

    2002-01-01

    exfoliation menace in this case will be more than in the first one. As it is known, suspension will be stable if it contains not more than 25 % of solid matters. This condition can be easily satisfy in the case of application of fine powders from fuel matters (UO 2 or U C). So this variant of creation of liquid nuclear fuel has the right to existence in future elaboration of homogeneous reactors. In the case of Th→ 233 U cycle i.e. breeder reactor on thermal neutrons, the best candidate for their reflective wall is beryllium, while in cycle 238 U→ 239 Pu the most suitable reflector is 238 U itself, which is also reproducer of plutonium fuel. In this case Be is not very suitable as a reflector because it mitigates neutron spectrum at reflection that will be undesirable in fast breeder reactor

  13. Single-particle levitation system for automated study of homogeneous solute nucleation

    OpenAIRE

    Olsen, Adam P.; Flagan, Richard C.; Kornfield, Julia A.

    2006-01-01

    We present an instrument that addresses two critical requirements for quantitative measurements of the homogeneous crystal nucleation rate in supersaturated aqueous solution. First, the need to perform repeated measurements of nucleation incubation times is met by automating experiments to enable programmable cycling of thermodynamic conditions. Second, the need for precise and robust control of the chemical potential in supersaturated aqueous solution is met by implementing a novel technique...

  14. The Effect of Masterbatch Recipes on the Homogenization Properties of Injection Molded Parts

    OpenAIRE

    Zsíros, László; Török, Dániel; Kovács, József Gábor

    2017-01-01

    Appearance is a key factor in most injection molding applications. Unfortunately, there is no widespread method to objectively test visual appearance, such as color inhomogeneity of the parts or other surface defects. We developed an evaluation method to characterize the color inhomogeneity of injection molded parts. First, we examined manufacturing conditions and masterbatch recipes and then the individual effects of the components and their interactions on homogeneity.

  15. The Effect of Masterbatch Recipes on the Homogenization Properties of Injection Molded Parts

    Directory of Open Access Journals (Sweden)

    László Zsíros

    2017-01-01

    Full Text Available Appearance is a key factor in most injection molding applications. Unfortunately, there is no widespread method to objectively test visual appearance, such as color inhomogeneity of the parts or other surface defects. We developed an evaluation method to characterize the color inhomogeneity of injection molded parts. First, we examined manufacturing conditions and masterbatch recipes and then the individual effects of the components and their interactions on homogeneity.

  16. Study methods for the drillings around the underground nuclear explosions in the Sahara. Part 1. study of rock samples; Methodes d'etude des forages realises autour des explosions nucleaires souterraines au Sahara. Premiere partie: etude des echantillons de roche

    Energy Technology Data Exchange (ETDEWEB)

    Derlich, S [Commissariat a l' Energie Atomique, Bruyers-le-Chatel (France). Centre d' Etudes

    1969-07-01

    An examination of the mechanical effects produced on rocks by an underground nuclear explosion calls for the use of particular means of exploration which are described in this report, special attention being paid to the equipment used in connection with the French nuclear tests in the Sahara. The drilling methods used (rotary and turbo-drilling) are adapted to the particular conditions of the sampling programme, to the radioactivity and to the temperature in the region of the explosion. A study of the samples makes it possible to obtain the new characteristics of the rock and to assess the chemical and mechanical transformations which it has undergone. An examination of the core obtained from the drilling, together with a knowledge of the drilling parameters (depth of the probe, sample recovery, etc...), makes it possible to study the extent and the characteristics of the zones which have been damaged to different degrees according to their distance from the zero point: cavity, strongly powdered zone, fractured zone, chimney, zones containing high stresses leading to a particular type of fracture of the cores. The problems connected with the interpretation of the results are also presented. (author) [French] L'examen des effets mecaniques provoques par une explosion nucleaire souterraine sur la roche necessite la mise en oeuvre de moyens d'exploration particuliers dont l'expose fait l'objet de ce rapport, essentiellement pour les moyens utilises autour des essais nucleaires francais au Sahara. Les methodes de forage (rotary et turboforage) sont adaptees aux conditions particulieres dues au programme d'echantillonnage, a la radioactivite et a la temperature regnant a proximite du point de tir. L'etude des echantillons permet la determination des nouveaux caracteres de la roche et de ses transformations chimique et mecanique. L'examen des carottes et l'utilisation des parametres de forage (cotes sondeurs, recuperation des echantillons, etc...) permettent d'etudier l

  17. A new model for reliability optimization of series-parallel systems with non-homogeneous components

    International Nuclear Information System (INIS)

    Feizabadi, Mohammad; Jahromi, Abdolhamid Eshraghniaye

    2017-01-01

    In discussions related to reliability optimization using redundancy allocation, one of the structures that has attracted the attention of many researchers, is series-parallel structure. In models previously presented for reliability optimization of series-parallel systems, there is a restricting assumption based on which all components of a subsystem must be homogeneous. This constraint limits system designers in selecting components and prevents achieving higher levels of reliability. In this paper, a new model is proposed for reliability optimization of series-parallel systems, which makes possible the use of non-homogeneous components in each subsystem. As a result of this flexibility, the process of supplying system components will be easier. To solve the proposed model, since the redundancy allocation problem (RAP) belongs to the NP-hard class of optimization problems, a genetic algorithm (GA) is developed. The computational results of the designed GA are indicative of high performance of the proposed model in increasing system reliability and decreasing costs. - Highlights: • In this paper, a new model is proposed for reliability optimization of series-parallel systems. • In the previous models, there is a restricting assumption based on which all components of a subsystem must be homogeneous. • The presented model provides a possibility for the subsystems’ components to be non- homogeneous in the required conditions. • The computational results demonstrate the high performance of the proposed model in improving reliability and reducing costs.

  18. A new consistent definition of the homogenized diffusion coefficient of a lattice, limitations of the homogenization concept, and discussion of previously defined coefficients

    International Nuclear Information System (INIS)

    Deniz, V.C.

    1978-01-01

    The problem concerned with the correct definition of the homogenized diffusion coefficient of a lattice, and the concurrent problem of whether or not a homogenized diffusion equation can be formally set up, is studied by a space-energy angle dependent treatment for a general lattice cell; using an operator notation which applies to any eigen-problem. It is shown that the diffusion coefficient should represent only leakage effects. A new definition of the diffusion coefficient is given, which combines within itself the individual merits of each of the two definitions of Benoist, and reduces to the 'uncorrected' Benoist coefficient in certain cases. The conditions under which a homogenized diffusion equation can be obtained are discussed. A compatison is made between the approach via a diffusion equation and the approach via the eigen-coefficients of Deniz. Previously defined diffusion coefficients are discussed, and it is shown that the transformed eigen-coefficients proposed by Gelbard and by Larsen are unsuitable as diffusion coefficients, and that the cell-edge normalization of the Bonalumi coefficient is not physically justifiable. (author)

  19. A contribution to the study of radioactive waste dilution in the Rhone involving tests with a rhodamine B tracer; Contribution a l'etude de la dilution des effluents radioactifs dans le Rhone par le rejet experimental de rhodamine B

    Energy Technology Data Exchange (ETDEWEB)

    Rodier, J.; Marichal, M. [Commissariat a l' energie atomique et aux energies alternatives - CEA, Centre de production de plutonium de Marcoule, Service de protection contre les radiations (France)

    1961-07-01

    The process whereby waste from the Marcoule plant mixes with the water in the Rhone was followed in tests with rhodamine as a chemical tracer. Satisfactory dispersion was noted less than 4 km downstream from the waste discharge duct outlet, and the degree of homogeneity was considered to be satisfactory at the bridge of Roquemaure, und perfect at Avignon. This investigation not only revealed a complete absence of any preferential flow paths containing high radioactive waste concentrations, but it also enabled the most representative points to be selected at which to take Rhone water samples during future radioactive waste discharges. Reprint of a paper published in 'La Houille Blanche' N. 5 - Aug 196, p. 636-641 [French] L'emploi de la rhodamine comme traceur chimique a permis de suivre l'evolution du melange des effluents du Centre de Marcoule aux eaux du Rhone. La dispersion est deja satisfaisante a moins de 4 km en aval de la conduite des rejets, et l'homogeneite peut etre consideree comme atteinte au pont de Roquemaure et parfaite a Avignon. Cette etude a montre que les veines preferentielles ou se concentrait l'ecoulement des effluents radioactifs n'existent pas. Elle a permis de preciser en outre les emplacements les plus representatifs des points d'echantillonnage des eaux du Rhone au cours des rejets. Reproduction d'un article publie dans 'La houille blanche' N. 5 - Aug 196, p. 636-641.

  20. Homogeneous Nanodiamonds Are Different in Reality

    Science.gov (United States)

    Wu, Chi-Chin; Gottfried, Jennifer; Pesce-Rodriguez, Rose; Advanced Energetic Materials Team

    Commercial detonation nanodiamonds (ND) have been investigated for many applications. They consist of carbon nanoparticles with diamond cores surrounded by onion-like graphitic shells. Unfortunately, variations in the purity and carbon structure between commercial ND samples due to variations in synthesis and purification conditions is an ongoing issue, since these differences can affect the resulting application-dependent ND behavior. Via characterization with transmission electron microscopy, this work investigates the structural and chemical differences among nominally homologous commercial detonation ND sold by a single vendor under the same item number. Significant discrepancies in the carbon structure and crystallinity between different batches with similar sizes and shapes were identified. The ND containing more non-carbon entities as impurities and oxygen-containing surface functional groups were found to possess thicker graphitic shells surrounding an unstable diamond core which quickly transforms to graphite under electron beam irradiation. However, the structure of ND with higher purities and thin onion shells remain unchanged over extended exposure to electron beams. This study demonstrates the structural and chemical differences between nominally identical commercial detonation ND samples and reveals their influence on the decomposition behavior of the particles.

  1. Bridging heterogeneous and homogeneous catalysis concepts, strategies, and applications

    CERN Document Server

    Li, Can

    2014-01-01

    This unique handbook fills the gap in the market for an up-to-date work that links both homogeneous catalysis applied to organic reactions and catalytic reactions on surfaces of heterogeneous catalysts.

  2. Time travel in the homogeneous Som-Raychaudhuri Universe

    International Nuclear Information System (INIS)

    Paiva, F.M.; Reboucas, M.J.; Teixeira, A.F.F.

    1987-01-01

    Properties of the rotating Som-Raychaudhuri homogeneous space-time are investigated: time-like and null geodesics, causality features, horizons and invariant characterization. An integral representation of its five isometries is also discussed. (author) [pt

  3. [Methods for enzymatic determination of triglycerides in liver homogenates].

    Science.gov (United States)

    Höhn, H; Gartzke, J; Burck, D

    1987-10-01

    An enzymatic method is described for the determination of triacylglycerols in liver homogenate. In contrast to usual methods, higher reliability and selectivity are achieved by omitting the extraction step.

  4. A convenient procedure for magnetic field homogeneity evaluation

    International Nuclear Information System (INIS)

    Teles, J; Garrido, C E; Tannus, A

    2004-01-01

    In many areas of research that utilize magnetic fields in their studies, it is important to obtain fields with a spatial distribution as homogeneous as possible. A procedure usually utilized to evaluate and to optimize field homogeneity is the expansion of the measured field in spherical harmonic components. In addition to the methods proposed in the literature, we present a more convenient procedure for evaluation of field homogeneity inside a spherical volume. The procedure uses the orthogonality property of the spherical harmonics to find the field variance. It is shown that the total field variance is equal to the sum of the individual variances of each field component in the spherical harmonic expansion. Besides the advantages of the linear behaviour of the individual variances, there is the fact that the field variance and standard deviation are the best parameters to achieve global homogeneity field information

  5. Tests for homogeneity for multiple 2 x 2 contingency tables

    International Nuclear Information System (INIS)

    Carr, D.B.

    1986-01-01

    Frequently data are described by 2 x 2 contingency tables. For example, each 2 x 2 table arises from two dichotomous classifications such as control/treated and respond/did not respond. Multiple 2 x 2 tables result from stratifying the observational units on the basis of other characteristics. For example, stratifying by sex produces separate 2 x 2 tables for males and females. From each table a measure of difference between the response rates for the control and the treated groups is computed. The researcher usually wants to know if the response-rate difference is zero for each table. If the tables are homogeneous, the researcher can generalize from a statement concerning an average to a statement concerning each table. If tables are not homogeneous, homogeneous subsets of the tables should be described separately. This paper presents tests for homogeneity and illustrates their use. 11 refs., 6 tabs

  6. Engineered CHO cells for production of diverse, homogeneous glycoproteins

    DEFF Research Database (Denmark)

    Yang, Zhang; Wang, Shengjun; Halim, Adnan

    2015-01-01

    Production of glycoprotein therapeutics in Chinese hamster ovary (CHO) cells is limited by the cells' generic capacity for N-glycosylation, and production of glycoproteins with desirable homogeneous glycoforms remains a challenge. We conducted a comprehensive knockout screen of glycosyltransferas...

  7. Homogenization of aligned “fuzzy fiber” composites

    KAUST Repository

    Chatzigeorgiou, George; Efendiev, Yalchin; Lagoudas, Dimitris C.

    2011-01-01

    The aim of this work is to study composites in which carbon fibers coated with radially aligned carbon nanotubes are embedded in a matrix. The effective properties of these composites are identified using the asymptotic expansion homogenization

  8. Jordan's algebra of a facially homogeneous autopolar cone

    International Nuclear Information System (INIS)

    Bellissard, Jean; Iochum, Bruno

    1979-01-01

    It is shown that a Jordan-Banach algebra with predual may be canonically associated with a facially homogeneous autopolar cone. This construction generalizes the case where a trace vector exists in the cone [fr

  9. Data on the effect of homogenization heat treatments on the cast structure and tensile properties of alloy 718Plus in the presence of grain-boundary elements.

    Science.gov (United States)

    Hosseini, Seyed Ali; Madar, Karim Zangeneh; Abbasi, Seyed Mehdi

    2017-08-01

    The segregation of the elements during solidification and the direct formation of destructive phases such as Laves from the liquid, result in in-homogeneity of the cast structure and degradation of mechanical properties. Homogenization heat treatment is one of the ways to eliminate destructive Laves from the cast structure of superalloys such as 718Plus. The collected data presents the effect of homogenization treatment conditions on the cast structure, hardness, and tensile properties of the alloy 718Plus in the presence of boron and zirconium additives. For this purpose, five alloys with different contents of boron and zirconium were cast by VIM/VAR process and then were homogenized at various conditions. The microstructural investigation by OM and SEM and phase analysis by XRD were done and then hardness and tensile tests were performed on the homogenized alloys.

  10. Homogenization of aligned “fuzzy fiber” composites

    KAUST Repository

    Chatzigeorgiou, George

    2011-09-01

    The aim of this work is to study composites in which carbon fibers coated with radially aligned carbon nanotubes are embedded in a matrix. The effective properties of these composites are identified using the asymptotic expansion homogenization method in two steps. Homogenization is performed in different coordinate systems, the cylindrical and the Cartesian, and a numerical example are presented. © 2011 Elsevier Ltd. All rights reserved.

  11. The Perron-Frobenius theorem for multi-homogeneous mappings

    OpenAIRE

    Gautier, Antoine; Tudisco, Francesco; Hein, Matthias

    2018-01-01

    The Perron-Frobenius theory for nonnegative matrices has been generalized to order-preserving homogeneous mappings on a cone and more recently to nonnegative multilinear forms. We unify both approaches by introducing the concept of order-preserving multi-homogeneous mappings, their associated nonlinear spectral problems and spectral radii. We show several Perron-Frobenius type results for these mappings addressing existence, uniqueness and maximality of nonnegative and positive eigenpairs. We...

  12. Homogeneity in Luxury Fashion Consumption: an Exploration of Arab Women

    OpenAIRE

    Marciniak, R.; Gad Mohsen, Marwa

    2014-01-01

    Consumer perceptions and consumer motivations are complex and whilst it is acknowledged within literature\\ud that heterogeneity exists, homogenous models dominate consumer behaviour research. The primary purpose of this\\ud paper is to explore the extent to which Arab women are a homogeneous group of consumers in regard to perceptions\\ud and motivations to consume luxury fashion goods. In particular, the paper seeks to present a critical review of luxury consumption frameworks. As part of the ...

  13. Matrix-dependent multigrid-homogenization for diffusion problems

    Energy Technology Data Exchange (ETDEWEB)

    Knapek, S. [Institut fuer Informatik tu Muenchen (Germany)

    1996-12-31

    We present a method to approximately determine the effective diffusion coefficient on the coarse scale level of problems with strongly varying or discontinuous diffusion coefficients. It is based on techniques used also in multigrid, like Dendy`s matrix-dependent prolongations and the construction of coarse grid operators by means of the Galerkin approximation. In numerical experiments, we compare our multigrid-homogenization method with homogenization, renormalization and averaging approaches.

  14. Spray structure as generated under homogeneous flash boiling nucleation regime

    International Nuclear Information System (INIS)

    Levy, M.; Levy, Y.; Sher, E.

    2014-01-01

    We show the effect of the initial pressure and temperature on the spatial distribution of droplets size and their velocity profile inside a spray cloud that is generated by a flash boiling mechanism under homogeneous nucleation regime. We used TSI's Phase Doppler Particle Analyzer (PDPA) to characterize the spray. We conclude that the homogeneous nucleation process is strongly affected by the initial liquid temperature while the initial pressure has only a minor effect. The spray shape is not affected by temperature or pressure under homogeneous nucleation regime. We noted that the only visible effect is in the spray opacity. Finally, homogeneous nucleation may be easily achieved by using a simple atomizer construction, and thus is potentially suitable for fuel injection systems in combustors and engines. - Highlights: • We study the characteristics of a spray that is generated by a flash boiling process. • In this study, the flash boiling process occurs under homogeneous nucleation regime. • We used Phase Doppler Particle Analyzer (PDPA) to characterize the spray. • The SMD has been found to be strongly affected by the initial liquid temperature. • Homogeneous nucleation may be easily achieved by using a simple atomizer unit

  15. Applications of a systematic homogenization theory for nodal diffusion methods

    International Nuclear Information System (INIS)

    Zhang, Hong-bin; Dorning, J.J.

    1992-01-01

    The authors recently have developed a self-consistent and systematic lattice cell and fuel bundle homogenization theory based on a multiple spatial scales asymptotic expansion of the transport equation in the ratio of the mean free path to the reactor characteristics dimension for use with nodal diffusion methods. The mathematical development leads naturally to self-consistent analytical expressions for homogenized diffusion coefficients and cross sections and flux discontinuity factors to be used in nodal diffusion calculations. The expressions for the homogenized nuclear parameters that follow from the systematic homogenization theory (SHT) are different from those for the traditional flux and volume-weighted (FVW) parameters. The calculations summarized here show that the systematic homogenization theory developed recently for nodal diffusion methods yields accurate values for k eff and assembly powers even when compared with the results of a fine mesh transport calculation. Thus, it provides a practical alternative to equivalence theory and GET (Ref. 3) and to simplified equivalence theory, which requires auxiliary fine-mesh calculations for assemblies embedded in a typical environment to determine the discontinuity factors and the equivalent diffusion coefficient for a homogenized assembly

  16. Homogenization patterns of the world’s freshwater fish faunas

    Science.gov (United States)

    Villéger, Sébastien; Blanchet, Simon; Beauchard, Olivier; Oberdorff, Thierry; Brosse, Sébastien

    2011-01-01

    The world is currently undergoing an unprecedented decline in biodiversity, which is mainly attributable to human activities. For instance, nonnative species introduction, combined with the extirpation of native species, affects biodiversity patterns, notably by increasing the similarity among species assemblages. This biodiversity change, called taxonomic homogenization, has rarely been assessed at the world scale. Here, we fill this gap by assessing the current homogenization status of one of the most diverse vertebrate groups (i.e., freshwater fishes) at global and regional scales. We demonstrate that current homogenization of the freshwater fish faunas is still low at the world scale (0.5%) but reaches substantial levels (up to 10%) in some highly invaded river basins from the Nearctic and Palearctic realms. In these realms experiencing high changes, nonnative species introductions rather than native species extirpations drive taxonomic homogenization. Our results suggest that the “Homogocene era” is not yet the case for freshwater fish fauna at the worldwide scale. However, the distressingly high level of homogenization noted for some biogeographical realms stresses the need for further understanding of the ecological consequences of homogenization processes. PMID:22025692

  17. Homogenization patterns of the world's freshwater fish faunas.

    Science.gov (United States)

    Villéger, Sébastien; Blanchet, Simon; Beauchard, Olivier; Oberdorff, Thierry; Brosse, Sébastien

    2011-11-01

    The world is currently undergoing an unprecedented decline in biodiversity, which is mainly attributable to human activities. For instance, nonnative species introduction, combined with the extirpation of native species, affects biodiversity patterns, notably by increasing the similarity among species assemblages. This biodiversity change, called taxonomic homogenization, has rarely been assessed at the world scale. Here, we fill this gap by assessing the current homogenization status of one of the most diverse vertebrate groups (i.e., freshwater fishes) at global and regional scales. We demonstrate that current homogenization of the freshwater fish faunas is still low at the world scale (0.5%) but reaches substantial levels (up to 10%) in some highly invaded river basins from the Nearctic and Palearctic realms. In these realms experiencing high changes, nonnative species introductions rather than native species extirpations drive taxonomic homogenization. Our results suggest that the "Homogocene era" is not yet the case for freshwater fish fauna at the worldwide scale. However, the distressingly high level of homogenization noted for some biogeographical realms stresses the need for further understanding of the ecological consequences of homogenization processes.

  18. Study of the aqueous chemical treatment of uranium zirconium fuels; Etude du traitement chimique des combustibles uraniumzirconium par voie seche

    Energy Technology Data Exchange (ETDEWEB)

    Bourgeois, M; Nollet, P [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1964-07-01

    A dry process has been studied for separating the uranium from the zirconium-either for recovering the enriched uranium from fuel element production waste, or with a view to treating this waste after irradiation. In this process the alloy is treated with hydrochloric acid at 400 deg. C in a fluidized corundum bed which causes the zirconium to volatilize as tetrachloride and the uranium to form the trichloride. This latter is then converted to the hexafluoride by attack with fluorure. After the laboratory tests, a first pilot plant with a capacity of 1 kg of alloy was tried out at the Fontenay-aux-Roses Nuclear Research Centre; this made it possible to fix the operational conditions for the process. An industrial scale plant was then built with the collaboration of the from Kuhlmann, and operated until a satisfactory process had been developed for treating the waste. This installation treats 3 kg/h of alloy with a yield for the hydrochloric acid of about 50 per cent and with a uranium loss in the zirconium tetrachloride of about 0.1 per cent. An active pilot plant capable of treating of treating a few kilos of irradiated alloy is now being studied. (authors) [French] On a etudie un procede de voie seche pour effectuer la separation de l'uranium et du zirconium - soit en vue de la recuperation de l'uranium enrichi contenu dans les dechets de fabrication des elements combustibles - soit en vue du traitement de ceux-ci apres irradiation. Ce procede consiste a attaquer l'alliage par l'acide chlorhydrique a 400 deg. C dans un lit fluidise de corindon, ce qui a pour effet de volatiliser le zirconium sous forme de tetrachlorure et de transformer l'uranium en trichlorure. Ce dernier est ensuite converti en hexafluorure par action du fluor. Apres des essais de laboratoire, un premier pilote a l'echelle de 1 kg d'alliage a ete experimente au Centre d'Etudes Nucleaires de Fontenay-aux-Roses et a permis de determiner les conditions operatoires du procede. En collaboration avec

  19. Surface integral formulation of Maxwell's equations for simulation of non-destructive testing by eddy currents. Preliminary study on the implementation of the fast multipole method; Formulation integrale surfacique des equations de Maxwell pour la simulation de controles non destructifs par courant de Foucault. Etude preliminaire a la mise en oeuvre de la methode multipole rapide.

    Energy Technology Data Exchange (ETDEWEB)

    Lim, T.

    2011-04-28

    numeriquement un controle non destructif par courants de Foucault (CND-CF), la reponse du capteur peut etre modelisee via une approche semi-analytique par integrales de volume. Plus rapide que la methode des elements finis, cette approche est cependant limitee a l'etude de pieces planes ou cylindriques (sans prise en compte des effets de bords) du fait de la complexite de l'expression de la dyade de Green pour des configurations plus generales. Or, il existe une forte demande industrielle pour etendre les capacites de la modelisation CF a des configurations complexes (plaques deformees, bords de piece...). Nous avons donc ete amenes a formuler differemment le probleme electromagnetique, en nous fixant comme objectif de conserver une approche semi-analytique. La formulation integrale surfacique (SIE) permet d'exprimer le probleme volumique en un probleme de transmission equivalent a l'interface (2D) entre sous-domaines homogenes. Ce probleme est ramene a la resolution d'un systeme lineaire (par la methode des moments) dont le nombre d'inconnues est reduit du fait du caractere surfacique du maillage. Des lors, ce systeme peut etre resolu par un solveur direct pour de petites configurations. Cela nous a permis de traiter plusieurs seconds membres (ie. differentes positions de capteurs) pour une seule inversion de la matrice d'impedance. Les resultats numeriques obtenus au moyen de cette formulation concernent des plaques avec la prise en compte des effets de bords tels que l'arete et le coin. Ils sont en accord avec des resultats obtenus par la methode des elements finis. Pour des configurations de grandes tailles, nous avons mene une etude preliminaire a l'adaptation d'une methode d'acceleration du produit matrice-vecteur intervenant dans un solveur iteratif (methode multipole rapide, ou FMM) afin de definir les conditions dans lesquelles le calcul FMM fonctionne correctement (precision, convergence...) dans le contexte CND

  20. Miniature free-piston homogeneous charge compression ignition engine-compressor concept - Part II: modeling HCCI combustion in small scales with detailed homogeneous gas phase chemical kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Aichlmayr, H.T.; Kittelson, D.B.; Zachariah, M.R. [The University of Minnesota, Minneapolis (United States). Departments of Mechanical Engineering and Chemistry

    2002-10-01

    Operational maps for crankshaft-equipped miniature homogeneous charge compression ignition engines are established using performance estimation, detailed chemical kinetics, and diffusion models for heat transfer and radical loss. In this study, radical loss was found to be insignificant. In contrast, heat transfer was found to be increasingly significant for 10, 1, and 0.1 W engines, respectively. Also, temperature-pressure trajectories and ignition delay time maps are used to explore relationships between engine operational parameters and HCCI. Lastly, effects of engine operating conditions and design on the indicated fuel conversion efficiency are investigated. (author)

  1. Analytical solutions of time-fractional models for homogeneous Gardner equation and non-homogeneous differential equations

    Directory of Open Access Journals (Sweden)

    Olaniyi Samuel Iyiola

    2014-09-01

    Full Text Available In this paper, we obtain analytical solutions of homogeneous time-fractional Gardner equation and non-homogeneous time-fractional models (including Buck-master equation using q-Homotopy Analysis Method (q-HAM. Our work displays the elegant nature of the application of q-HAM not only to solve homogeneous non-linear fractional differential equations but also to solve the non-homogeneous fractional differential equations. The presence of the auxiliary parameter h helps in an effective way to obtain better approximation comparable to exact solutions. The fraction-factor in this method gives it an edge over other existing analytical methods for non-linear differential equations. Comparisons are made upon the existence of exact solutions to these models. The analysis shows that our analytical solutions converge very rapidly to the exact solutions.

  2. Toward whole-core neutron transport without spatial homogenization

    International Nuclear Information System (INIS)

    Lewis, E. E.

    2009-01-01

    Full text of publication follows: A long-term goal of computational reactor physics is the deterministic analysis of power reactor core neutronics without incurring significant discretization errors in the energy, spatial or angular variables. In principle, given large enough parallel configurations with unlimited CPU time and memory, this goal could be achieved using existing three-dimensional neutron transport codes. In practice, however, solving the Boltzmann equation for neutrons over the six-dimensional phase space is made intractable by the nature of neutron cross-sections and the complexity and size of power reactor cores. Tens of thousands of energy groups would be required for faithful cross section representation. Likewise, the numerous material interfaces present in power reactor lattices require exceedingly fine spatial mesh structures; these ubiquitous interfaces preclude effective implementation of adaptive grid, mesh-less methods and related techniques that have been applied so successfully in other areas of engineering science. These challenges notwithstanding, substantial progress continues in the pursuit for more robust deterministic methods for whole-core neutronics analysis. This paper examines the progress over roughly the last decade, emphasizing the space-angle variables and the quest to eliminate errors attributable to spatial homogenization. As prolog we briefly assess 1990's methods used in light water reactor analysis and review the lessons learned from the C5G7 benchmark exercises which were originated in 1999 to appraise the ability of transport codes to perform core calculations without homogenization. We proceed by examining progress over the last decade much of which falls into three areas. These may be broadly characterized as reduced homogenization, dynamic homogenization and planar-axial synthesis. In the first, homogenization in three-dimensional calculations is reduced from the fuel assembly to the pin-cell level. In the second

  3. Study of the retention of fission products by a few common minerals. Application to the treatment of medium activity effluents (1962); Etude de la retention des produits de fission par quelques mineraux usuels. Application aux traitements d'effluents de moyenne activite specifique (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Auchapt, J M [Commissariat a l' Energie Atomique, Centre de Production de Plutonium, Marcoule (France). Centre d' Etudes Nucleaires

    1962-07-01

    The conditions in which strontium is fixed on calcite (the object of the Geneva report P/395 - USA - 1958) are more closely studied and the work is extended to five fission products present in the effluents, and to 17 common rocks and minerals. Although as it turns out this fixation is not suitable as a method of treating the S.T.E. effluents (i.e. those from the Effluent Treatment plant at Marcoule), the study shows that all the crystals considered are strongly contaminated by simple contact with the effluents. (author) [French] Les conditions de fixation du strontium sur la calcite (objet du rapport de Geneve P/395 - USA - 1958) sont approfondies et l'etude est etendue aux cinq produits de fission presents dans les effluents et a 17 roches et minerais courants. Bien qu'en definitive cette fixation se revele inutilisable comme procede de traitement d'effluents S.T.E. (Station de Traitement des Effluents, Marcoule), l'etude montre que tous les cristaux consideres se contaminent fortement par simple contact avec les effluents. (auteur)

  4. Optimization and characterization of high pressure homogenization produced chemically modified starch nanoparticles.

    Science.gov (United States)

    Ding, Yongbo; Kan, Jianquan

    2017-12-01

    Chemically modified starch (RS4) nanoparticles were synthesized through homogenization and water-in-oil mini-emulsion cross-linking. Homogenization was optimized with regard to z-average diameter by using a three-factor-three-level Box-Behnken design. Homogenization pressure (X 1 ), oil/water ratio (X 2 ), and surfactant (X 3 ) were selected as independent variables, whereas z-average diameter was considered as a dependent variable. The following optimum preparation conditions were obtained to achieve the minimum average size of these nanoparticles: 50 MPa homogenization pressure, 10:1 oil/water ratio, and 2 g surfactant amount, when the predicted z-average diameter was 303.6 nm. The physicochemical properties of these nanoparticles were also determined. Dynamic light scattering experiments revealed that RS4 nanoparticles measuring a PdI of 0.380 and an average size of approximately 300 nm, which was very close to the predicted z-average diameter (303.6 nm). The absolute value of zeta potential of RS4 nanoparticles (39.7 mV) was higher than RS4 (32.4 mV), with strengthened swelling power. X-ray diffraction results revealed that homogenization induced a disruption in crystalline structure of RS4 nanoparticles led to amorphous or low-crystallinity. Results of stability analysis showed that RS4 nanosuspensions (particle size) had good stability at 30 °C over 24 h.

  5. String-like cooperative motion in homogeneous melting.

    Science.gov (United States)

    Zhang, Hao; Khalkhali, Mohammad; Liu, Qingxia; Douglas, Jack F

    2013-03-28

    Despite the fundamental nature and practical importance of melting, there is still no generally accepted theory of this ubiquitous phenomenon. Even the earliest simulations of melting of hard discs by Alder and Wainwright indicated the active role of collective atomic motion in melting and here we utilize molecular dynamics simulation to determine whether these correlated motions are similar to those found in recent studies of glass-forming (GF) liquids and other condensed, strongly interacting, particle systems. We indeed find string-like collective atomic motion in our simulations of "superheated" Ni crystals, but other observations indicate significant differences from GF liquids. For example, we observe neither stretched exponential structural relaxation, nor any decoupling phenomenon, while we do find a boson peak, findings that have strong implications for understanding the physical origin of these universal properties of GF liquids. Our simulations also provide a novel view of "homogeneous" melting in which a small concentration of interstitial defects exerts a powerful effect on the crystal stability through their initiation and propagation of collective atomic motion. These relatively rare point defects are found to propagate down the strings like solitons, driving the collective motion. Crystal integrity remains preserved when the permutational atomic motions take the form of ring-like atomic exchanges, but a topological transition occurs at higher temperatures where the rings open to form linear chains similar in geometrical form and length distribution to the strings of GF liquids. The local symmetry breaking effect of the open strings apparently destabilizes the local lattice structure and precipitates crystal melting. The crystal defects are thus not static entities under dynamic conditions, such as elevated temperatures or material loading, but rather are active agents exhibiting a rich nonlinear dynamics that is not addressed in conventional "static

  6. Studies of Immobilized Homogeneous Metal Catalysts on Silica Supports

    Energy Technology Data Exchange (ETDEWEB)

    Stanger, Keith James [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    The tethered, chiral, chelating diphosphine rhodium complex, which catalyzes the enantioselective hydrogenation of methyl-α-acetamidocinnamate (MAC), has the illustrated structure as established by 31P NMR and IR studies. Spectral and catalytic investigations also suggest that the mechanism of action of the tethered complex is the same as that of the untethered complex in solution. The rhodium complexes, [Rh(COD)H]4, [Rh(COD)2]+BF4-, [Rh(COD)Cl]2, and RhCl3• 3H2O, adsorbed on SiO2 are optimally activated for toluene hydrogenation by pretreatment with H2 at 200 C. The same complexes on Pd-SiO2 are equally active without pretreatments. The active species in all cases is rhodium metal. The catalysts were characterized by XPS, TEM, DRIFTS, and mercury poisoning experiments. Rhodium on silica catalyzes the hydrogenation of fluorobenzene to produce predominantly fluorocyclohexane in heptane and 1,2-dichloroethane solvents. In heptane/methanol and heptane/water solvents, hydrodefluorination to benzene and subsequent hydrogenation to cyclohexane occurs exclusively. Benzene inhibits the hydrodefluorination of fluorobenzene. In DCE or heptane solvents, fluorocyclohexane reacts with hydrogen fluoride to form cyclohexene. Reaction conditions can be chosen to selectively yield fluorocyclohexane, cyclohexene, benzene, or cyclohexane. The oxorhenium(V) dithiolate catalyst [-S(CH2)3s-]Re(O)(Me)(PPh3) was modified by linking it to a tether that could be attached to a silica support. Spectroscopic investigation and catalytic oxidation reactivity showed the heterogenized catalyst's structure and reactivity to be similar to its homogeneous analog. However, the immobilized catalyst offered additional advantages of recyclability, extended stability, and increased resistance to deactivation.

  7. Intersections of homogeneous Cantor sets and beta-expansions

    International Nuclear Information System (INIS)

    Kong, Derong; Li, Wenxia; Dekking, F Michel

    2010-01-01

    Let Γ β,N be the N-part homogeneous Cantor set with β in (1/(2N − 1), 1/N). Any string (j l ) l=1 ∞ with j l in {0, ±1, ..., ±(N − 1)} such that t=Σ l=1 ∞ j l β l-1 (1-β)/(N-1) is called a code of t. Let U β,±N be the set of t in [−1, 1] having a unique code, and let S β,±N be the set of t element of U β,±N which makes the intersection Γ β,N intersection (Γ β,N + t) a self-similar set. We characterize the set U β,±N in a geometrical and algebraical way, and give a sufficient and necessary condition for t element of S β,±N . Using techniques from beta-expansions, we show that there is a critical point β c in (1/(2N − 1), 1/N), which is a transcendental number, such that U β,±N has positive Hausdorff dimension if β in (1/(2N − 1), β c ), and contains countably infinite many elements if β in (β c , 1/N). Moreover, there exists a second critical point α c =[N+1-√((N-1)(N+3))]/2 element of (1/(2N-1),β c ) such that S β,±N has positive Hausdorff dimension if β in (1/(2N − 1), α c ), and contains countably infinite many elements if β in [α c , 1/N)

  8. Generalities on the dynamic behaviour of rapid reactors. Preliminary studies on Rapsodie; Generalites sur le comportement dynamique des piles rapides. Etudes preliminaires de rapsodie

    Energy Technology Data Exchange (ETDEWEB)

    Campan, J L; Chaumont, J P; Clauzon, P P; Ghesquiere, G; Leduc, J; Schmitt, A P; Zaleski, C P [Commissariat a l' Energie Atomique, Cadarache (France). Centre d' Etudes Nucleaires

    1963-07-01

    The study of the dynamic behaviour of fast reactors may be divided into three section: 1. Stability studies around equilibrium power only the linear case was examining. S. Transient studies in the case of usual reactor operation (shut down, scram, etc.) with thermal shocks evaluation, for instance. 3. Explosion studies, for the maximum credible accidents. This report presents the status of the studies performed at the 'Physics Research Department' at Cadarache. Methods used are detailed and illustrated with the results obtained on a preliminary metallic core of the Rapsodie Reactor. (authors) [French] Le comportement dynamique des piles rapides, se presente tout naturellement sous trois aspects: 1. Etude de stabilite autour d'un regime d'equilibre (nous nous sommes bornes ici au cas lineaire). 2. Etude de regimes transitoires lors des operations normales de pile (arret, arret d'urgence, etc.) avec evaluation des chocs thermiques par exemple. 3. Etude des regimes transitoires de caractere explosif lors des accidents les plus graves possibles. Ce rapport presente l'etat des etudes a la date du 20 decembre 1961 a la Section d'Etudes de Piles Rapides a CADARACHE. Les methodes employees ont ete detaillees et illustrees a partir des resultats obtenus sur une premiere version 'combustible metallique' de Rapsodie. (auteurs)

  9. Etude cinétique de la dégradation de l'Endosufane en solution ...

    African Journals Online (AJOL)

    Etude cinétique de la dégradation de l'Endosufane en solution. S Traore, K Mamadou, A Dembele, V Yao, Y Bekro, P Mazellier, B Legube, P Houenou. Abstract. Les pesticides sont fréquemment utilisés en Côte d'Ivoire. Leur détection dans les eaux de forage témoigne de leur mauvais usage et d'un grave problème ...

  10. Study of fission product {gamma} spectra in the band 2-500 keV; Etude du spectre {gamma} des produits de fission dans la bande 0-500 keV

    Energy Technology Data Exchange (ETDEWEB)

    Rousseau, A. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    In the study of the {gamma} spectrum of uranium fission products, particular attention has been given in this note to the part of the spectrum ranging between 0 and 500 keV after a given pile operating programme and the evolution of this spectrum with time after a pile shutdown has been followed. The study be related to the fission products which appear in the pile as a whole or on those produced in a uranium sample assumed to have been placed in the pile. The latter case has been envisaged here. The spectrum determination is based partly on theory and partly on experiment. The pile operating conditions are different in the two cases, which widens the range of validity of the spectra traced here. (author) [French] Dans l'etude du spectre {gamma} des produits de fission de l'uranium, on s'est plus particulierement interesse dans la presente note a determiner la partie du spectre qui s'etend entre 0 et 500 keV, au bout d'un fonctionnement donne de pile, et a suivre l'evolution de ce spectre dans le temps apres un arret de pile. L'etude peut porter sur les produits de fission apparus dans toute la pile ou sur ceux apparus dans un echantillon d'uranium suppose place en pile. C'est ce dernier cas que nous avons envisage. La determination du spectre s'appuie sur une partie theorique et sur une partie experimentale. Les fonctionnements de pile choisis sont differents dans les deux cas, ce qui permet d'etendre la gamme de validite des spectres traces ici. (auteur)

  11. Study of fission product {gamma} spectra in the band 2-500 keV; Etude du spectre {gamma} des produits de fission dans la bande 0-500 keV

    Energy Technology Data Exchange (ETDEWEB)

    Rousseau, A [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    In the study of the {gamma} spectrum of uranium fission products, particular attention has been given in this note to the part of the spectrum ranging between 0 and 500 keV after a given pile operating programme and the evolution of this spectrum with time after a pile shutdown has been followed. The study be related to the fission products which appear in the pile as a whole or on those produced in a uranium sample assumed to have been placed in the pile. The latter case has been envisaged here. The spectrum determination is based partly on theory and partly on experiment. The pile operating conditions are different in the two cases, which widens the range of validity of the spectra traced here. (author) [French] Dans l'etude du spectre {gamma} des produits de fission de l'uranium, on s'est plus particulierement interesse dans la presente note a determiner la partie du spectre qui s'etend entre 0 et 500 keV, au bout d'un fonctionnement donne de pile, et a suivre l'evolution de ce spectre dans le temps apres un arret de pile. L'etude peut porter sur les produits de fission apparus dans toute la pile ou sur ceux apparus dans un echantillon d'uranium suppose place en pile. C'est ce dernier cas que nous avons envisage. La determination du spectre s'appuie sur une partie theorique et sur une partie experimentale. Les fonctionnements de pile choisis sont differents dans les deux cas, ce qui permet d'etendre la gamme de validite des spectres traces ici. (auteur)

  12. Le changement comme tradition dans la recherche et la formation a la recherche en biotechnologie et en peripherie Etude de cas en sciences de la sante, sciences naturelles et genie

    Science.gov (United States)

    Bourque, Claude Julie

    Le champ de la recherche scientifique et de la formation a la recherche est traverse depuis quelques dizaines d'annees par plusieurs courants et discours associes au changement, mais peu de travaux empiriques permettent de comprendre ce qui change concretement. C'est la contribution originale de cette these au champ de l'education, plus specifiquement a l'etude sociologique de l'enseignement superieur ou sont concentrees les activites liees a la triade thematique du programme doctoral dans lequel elle a ete produite : recherche, formation et pratique. L'enquete-terrain a ete realisee en 2009 et 2010 aupres de 808 repondants affilies a 60 etablissements au Quebec et a produit un vaste materiau de nature mixte (donnees quantitatives et qualitatives). Un portrait de la nebuleuse biotechnologique qui touche les secteurs des sciences de la sante, des sciences naturelles et du genie a ete realise. Ce domaine concerne des dizaines de disciplines et se revele de nature transdisciplinaire, mais les pratiques n'y sont pas davantage marquees par le changement que celles d'autres domaines connexes. Les dynamiques sociales ont fait l'objet d'analyses comparatives dans quatre contextes: le choix des programmes, des objets et des methodes, le financement, la diffusion et la planification de la carriere. Les resultats indiquent que les echanges entre les agents traditionnellement situes au coeur des activites de recherche dominent ces dynamiques dans tous les contextes etudies. L'etude des representations au fondement des pratiques a revele l'existence de trois ecoles de pensee qui coexistent dans le champ scientifique: academique, pragmatique et economiste. Ces ecoles permettent de categoriser les agents en fonction des zones de fractures qui marquent leurs oppositions tout en identifiant ce qu'ils ont en commun. Les representations et les pratiques liees a la formation temoignent d'un habitus plutot homogene, alors que les contradictions semblent plus souvent ancrees dans des

  13. Study of the tributyl phosphate - 30% dodecane solvent; Etude du solvant phosphate tributylique - 30 % dodecane

    Energy Technology Data Exchange (ETDEWEB)

    Leroy, P [Commissariat a l' Energie Atomique, Fontenay-aux-Roses. Centre d' Etudes Nucleaires, 92 (France)

    1967-07-01

    This study, originating mainly from a literature survey, gives the principal chemical and physical features of the tributyl-phosphate (TBP) agent diluted at 30 volumes per cent in dodecane. The mixture is a very commonly used extractant in nuclear fuel processing. In this paper, the main following points are reported: -) the components (TBP and diluents) -) the TBP-diluents systems (non-loaded), -) the TBP-diluents-water systems, -) TBP-diluents-water-nitric acid systems, and -) industrial solvents. (author) [French] Cette etude, d'origine bibliographique, regroupe les caracteristiques physico-chimiques essentielles du phosphate tributylique (TBP) dilue a 30% en volume dans du dodecane. Ce melange constitue un agent d'extraction tres utilise dans le traitement des combustibles nucleaires. Les principaux points traites sont les suivants: -) les constituants (TBP et diluants), -) les systemes TBP-diluants non charges, -) les systemes TBP-diluants-eau, -) les systemes TBP-diluants-eau-acide nitrique, et -) les solvants industriels. (auteur)

  14. An economic study of the site of Marcoule; Etude economique du site de Marcoule

    Energy Technology Data Exchange (ETDEWEB)

    Duprat, H [Commissariat a l' Energie Atomique, Marcoule (France). Centre d' Etudes Nucleaires

    1964-07-01

    The study of this site of the Marcoule Center shows that its regional economical influence is limited to the buying power distributed among its personnel. This entails distortions between first this supplementary buying power and the overall markets within the possible Marcoule influence zone, and secondly the concentration on Bagnols-sur-Ceze and this town's normal extension possibilities. (author) [French] L'etude du site de Marcoule demontre que son influence economique se limite, pour la region, au pouvoir d'achat distribue a son personnel. Ceci entraine une disproportion d'une part entre ce pouvoir d'achat supplementaire et l'ensemble des marches contenus dans l'aire d'influence possible de Marcoule, d'autre part entre la concentration realisee a Bagnole-sur-Ceze et la capacite d'extension normale de cette agglomeration. (auteur)

  15. Spatial homogenization method based on the inverse problem

    International Nuclear Information System (INIS)

    Tóta, Ádám; Makai, Mihály

    2015-01-01

    Highlights: • We derive a spatial homogenization method in slab and cylindrical geometries. • The fluxes and the currents on the boundary are preserved. • The reaction rates and the integral of the fluxes are preserved. • We present verification computations utilizing two- and four-energy groups. - Abstract: We present a method for deriving homogeneous multi-group cross sections to replace a heterogeneous region’s multi-group cross sections; providing that the fluxes, the currents on the external boundary, the reaction rates and the integral of the fluxes are preserved. We consider one-dimensional geometries: a symmetric slab and a homogeneous cylinder. Assuming that the boundary fluxes are given, two response matrices (RMs) can be defined concerning the current and the flux integral. The first one derives the boundary currents from the boundary fluxes, while the second one derives the flux integrals from the boundary fluxes. Further RMs can be defined that connects reaction rates to the boundary fluxes. Assuming that these matrices are known, we present formulae that reconstruct the multi-group diffusion cross-section matrix, the diffusion coefficients and the reaction cross sections in case of one-dimensional (1D) homogeneous regions. We apply these formulae to 1D heterogeneous regions and thus obtain a homogenization method. This method produces such an equivalent homogeneous material, that the fluxes and the currents on the external boundary, the reaction rates and the integral of the fluxes are preserved for any boundary fluxes. We carry out the exact derivations in 1D slab and cylindrical geometries. Verification computations for the presented homogenization method were performed using two- and four-group material cross sections, both in a slab and in a cylindrical geometry

  16. Land-use intensification causes multitrophic homogenization of grassland communities.

    Science.gov (United States)

    Gossner, Martin M; Lewinsohn, Thomas M; Kahl, Tiemo; Grassein, Fabrice; Boch, Steffen; Prati, Daniel; Birkhofer, Klaus; Renner, Swen C; Sikorski, Johannes; Wubet, Tesfaye; Arndt, Hartmut; Baumgartner, Vanessa; Blaser, Stefan; Blüthgen, Nico; Börschig, Carmen; Buscot, Francois; Diekötter, Tim; Jorge, Leonardo Ré; Jung, Kirsten; Keyel, Alexander C; Klein, Alexandra-Maria; Klemmer, Sandra; Krauss, Jochen; Lange, Markus; Müller, Jörg; Overmann, Jörg; Pašalić, Esther; Penone, Caterina; Perović, David J; Purschke, Oliver; Schall, Peter; Socher, Stephanie A; Sonnemann, Ilja; Tschapka, Marco; Tscharntke, Teja; Türke, Manfred; Venter, Paul Christiaan; Weiner, Christiane N; Werner, Michael; Wolters, Volkmar; Wurst, Susanne; Westphal, Catrin; Fischer, Markus; Weisser, Wolfgang W; Allan, Eric

    2016-12-08

    Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in β-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (α)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing β-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in α-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on β-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in β-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local α-diversity in aboveground groups, whereas the α-diversity increased in belowground groups. Correlations between the β-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity

  17. On filter boundary conditions in topology optimization

    DEFF Research Database (Denmark)

    Clausen, Anders; Andreassen, Erik

    2017-01-01

    Most research papers on topology optimization involve filters for regularization. Typically, boundary effects from the filters are ignored. Despite significant drawbacks the inappropriate homogeneous Neumann boundary conditions are used, probably because they are trivial to implement. In this paper...

  18. Homogeneous Stabilizer by State Feedback for Switched Nonlinear Systems Using Multiple Lyapunov Functions’ Approach

    Directory of Open Access Journals (Sweden)

    Hui Ye

    2017-01-01

    Full Text Available This paper investigates the problem of global stabilization for a class of switched nonlinear systems using multiple Lyapunov functions (MLFs. The restrictions on nonlinearities are neither linear growth condition nor Lipschitz condition with respect to system states. Based on adding a power integrator technique, we design homogeneous state feedback controllers of all subsystems and a switching law to guarantee that the closed-loop system is globally asymptotically stable. Finally, an example is given to illustrate the validity of the proposed control scheme.

  19. Neutronic study of the two french heavy water reactors; Etude neutronique des deux piles francaises a eau lourde

    Energy Technology Data Exchange (ETDEWEB)

    Horowitz, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1955-07-01

    The two french reactors - the reactor of Chatillon, named Zoe, and the reactor of Saclay - P2 - were the object of detailed neutronic studies which the main ideas are exposed in this report. These studies were mostly done by the Department of the Reactor Studies (D.E.P.). We have thus studied the distribution of neutronic fluxes; the factors influencing reactivity; the link between reactivity and divergence with the formula of Nordheim; the mean time life of neutrons; neutron spectra s of P2; the xenon effect; or the effect of the different adjustments of the plates and controls bar. (M.B.) [French] Les deux reacteurs francais - la pile de Chatillon, appelee ZOE, et la pile de Saclay, designee dans la suite par P2 - ont fait l'objet d'etudes neutroniques detaillees dont les principales sont exposees dans ce rapport. Ces etudes ont ete pour la plupart effectuees dans le cadre du Departement des Etudes de Piles (D.E.P.). Nous avons ainsi entre autre etudie la distribution du flux neutronique; les facteurs influencants la reactivite; le lien entre reactivite et divergence par la formule de Nordheim; le temps de vie moyen des neutrons; les spectres de neutrons de P2; l'effet xenon; ou encore l'effet des differents reglages des plaques et barres de controles. (M.B.)

  20. Preparation and Optimization of 10-Hydroxycamptothecin Nanocolloidal Particles Using Antisolvent Method Combined with High Pressure Homogenization

    Directory of Open Access Journals (Sweden)

    Bolin Lian

    2017-01-01

    Full Text Available The aim of this study was to prepare 10-hydroxycamptothecin nanocolloidal particles (HCPTNPs to increase the solubility of drugs, reduce the toxicity, improve the stability of the drug, and so forth. HCPTNPs was prepared by antisolvent precipitation (AP method combined with high pressure homogenization (HPH, followed by lyophilization. The main parameters during antisolvent process including volume ratio of dimethyl sulfoxide (DMSO and H2O and dripping speed were optimized and their effects on mean particle size (MPS and yield of HCPT primary particles were investigated. In the high pressure homogeneous procedure, types of surfactants, amount of surfactants, and homogenization pressure (HP were optimized and their influences on MPS, zeta potential (ZP, and morphology were analyzed. The optimum conditions of HCPTNPs were as follows: 0.2 mg/mL HCPT aqueous suspension, 1% of ASS, 1000 bar of HP, and 20 passes. Finally, the HCPTNPs via lyophilization using glucose as lyoprotectant under optimum conditions had an MPS of 179.6 nm and a ZP of 28.79 ± 1.97 mV. The short-term stability of HCPTNPs indicated that the MPS changed in a small range.

  1. Degradation of S-nitrosocysteine in vascular tissue homogenates: role of divalent ions.

    Science.gov (United States)

    Kostka, P; Xu, B; Skiles, E H

    1999-04-01

    The objective of the study was to inquire about the mechanism(s) involved in the catabolism of S-nitrosothiols by vascular tissue under in vitro conditions. Incubations of S-nitrosocysteine (CYSNO) or S-nitrosoglutathione (GSNO) with homogenates isolated from porcine aortic smooth muscle resulted in only a marginal depletion of S-nitrosothiols from the reaction mixtures, which became statistically significant at relatively high concentrations of homogenate (> or =300 microg of protein/ml). Degradation of CYSNO (but not GSNO) was found to be potentiated several-fold by millimolar concentrations of either Mg2+ or Ca2+ ions. Under such conditions, the degradation of CYSNO was significantly suppressed by the removal of proteins by ultrafiltration (>80% inhibition) and eliminated completely by the alkylation of thiol groups with 1 mM N-ethylmaleimide. The potentiating effect of divalent ions on the degradation of CYSNO was insensitive to 0.1 mM neocuproine (selective chelator of Cu+ ions), although it was enhanced in the presence of 0.1 mM o-phenanthroline (selective chelator of Fe2+ ions). It is concluded that the degradation of CYSNO by tissue homogenate involves the interaction with protein-bound sulfhydryl groups, which is stimulated by Mg2+ or Ca2+ ions. The potentiating effect of o-phenanthroline suggests that the liberation of the nitrosonium moiety in such a process may be accompanied by its transfer to sulfur center(s) by transient formation of dinitrosyl-iron complexes.

  2. Efficacy of Ultrasonic Homogenization in the Separation of Benzene-n-Heptane Mixture by Liquid Membrane

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B.S.; Chung, T.S. [Department of Chemical Engineering, Sung Kyun Kwan University, Seoul (Korea)

    1999-04-01

    In the separation of benzene-n-heptane mixture by liquid membrane, the efficacy of ultrasonic homogenization in emulsification was studied with two anionic surfactants. The two anionic surfactants used were triethanolamine lauryl sulfate and sodium polyoxyethylene(2) lauryl ether sulfate. The two anionic surfactants used were triethanolamine lauryl sulfate and sodium polyoxyethylene(2) lauryl ether stifle. The highest value of the separation factor obtained by ultrasonic homogenization was approximately three times as large as that for triethanolamine lauryl sulfate and one and a half times as large as that for sodium polyoxyethylene(2) lauryl sulfate when the mechanical stirring was used on the same operational conditions. The lowest membrane breakup was observed when the highest value of the separation factor was achieved with sodium polyoxyethylene(2) lauryl sulfate. 14 refs., 7 figs., 1 tab.

  3. Nature of complex time eigenvalues of the one speed transport equation in a homogeneous sphere

    International Nuclear Information System (INIS)

    Dahl, E.B.; Sahni, D.C.

    1990-01-01

    The complex time eigenvalues of the transport equation have been studied for one speed neutrons, scattered isotropically in a homogeneous sphere with vacuum boundary conditions. It is shown that the complex decay constants vary continuously with the radius of the sphere. Our earlier conjecture (Dahl and Sahni (1983-84)) regarding disjoint arcs is thus shown to be true. We also indicate that complex decay constants exist even for large assemblies, though with rapid oscillations in the corresponding eigenvectors. These modes cannot be predicted by the diffusion equation as this behaviour of the eigenvectors contradicts the assumption of 'slowly varying flux' needed to derive the diffusion approximation from the transport equation. For an infinite system, the existence of complex modes is related to the solution of a homogeneous equation. (author)

  4. Enhanced photovoltaic properties of perovskite solar cells by TiO2 homogeneous hybrid structure.

    Science.gov (United States)

    Su, Pengyu; Fu, Wuyou; Yao, Huizhen; Liu, Li; Ding, Dong; Feng, Fei; Feng, Shuang; Xue, Yebin; Liu, Xizhe; Yang, Haibin

    2017-10-01

    In this paper, we fabricated a TiO 2 homogeneous hybrid structure for application in perovskite solar cells (PSCs) under ambient conditions. Under the standard air mass 1.5 global (AM 1.5G) illumination, PSCs based on homogeneous hybrid structure present a maximum power conversion efficiency of 5.39% which is higher than that of pure TiO 2 nanosheets. The enhanced properties can be explained by the better contact of TiO 2 nanosheets/nanoparticles with CH 3 NH 3 PbI 3 and fewer pinholes in electron transport materials. The advent of such unique structure opens up new avenues for the future development of high-efficiency photovoltaic cells.

  5. Homogenization of Large-Scale Movement Models in Ecology

    Science.gov (United States)

    Garlick, M.J.; Powell, J.A.; Hooten, M.B.; McFarlane, L.R.

    2011-01-01

    A difficulty in using diffusion models to predict large scale animal population dispersal is that individuals move differently based on local information (as opposed to gradients) in differing habitat types. This can be accommodated by using ecological diffusion. However, real environments are often spatially complex, limiting application of a direct approach. Homogenization for partial differential equations has long been applied to Fickian diffusion (in which average individual movement is organized along gradients of habitat and population density). We derive a homogenization procedure for ecological diffusion and apply it to a simple model for chronic wasting disease in mule deer. Homogenization allows us to determine the impact of small scale (10-100 m) habitat variability on large scale (10-100 km) movement. The procedure generates asymptotic equations for solutions on the large scale with parameters defined by small-scale variation. The simplicity of this homogenization procedure is striking when compared to the multi-dimensional homogenization procedure for Fickian diffusion,and the method will be equally straightforward for more complex models. ?? 2010 Society for Mathematical Biology.

  6. Automatic Control of the Concrete Mixture Homogeneity in Cycling Mixers

    Science.gov (United States)

    Anatoly Fedorovich, Tikhonov; Drozdov, Anatoly

    2018-03-01

    The article describes the factors affecting the concrete mixture quality related to the moisture content of aggregates, since the effectiveness of the concrete mixture production is largely determined by the availability of quality management tools at all stages of the technological process. It is established that the unaccounted moisture of aggregates adversely affects the concrete mixture homogeneity and, accordingly, the strength of building structures. A new control method and the automatic control system of the concrete mixture homogeneity in the technological process of mixing components have been proposed, since the tasks of providing a concrete mixture are performed by the automatic control system of processing kneading-and-mixing machinery with operational automatic control of homogeneity. Theoretical underpinnings of the control of the mixture homogeneity are presented, which are related to a change in the frequency of vibrodynamic vibrations of the mixer body. The structure of the technical means of the automatic control system for regulating the supply of water is determined depending on the change in the concrete mixture homogeneity during the continuous mixing of components. The following technical means for establishing automatic control have been chosen: vibro-acoustic sensors, remote terminal units, electropneumatic control actuators, etc. To identify the quality indicator of automatic control, the system offers a structure flowchart with transfer functions that determine the ACS operation in transient dynamic mode.

  7. Experimental study of metal gasketed joints for ultra-high vacuums; Etude experimentale de joints metalliques pour ultra-vide

    Energy Technology Data Exchange (ETDEWEB)

    Boulloud, J. P.; Schweitzer, J. [Commissariat a l' energie atomique et aux energies alternatives - CEA, Service de Physique Appliquee, groupe de Vide, Centre d' Etudes Nucleaires de Saclay (France)

    1960-07-01

    Various type of leak-tight metal joints have been studied with their application in assemblies containing total vacuums in mind. Their integrity has been tested with a helium leak detector, and leaks of about 2 x 10{sup -12} cm{sup 3} Atm/s per meter of joint have been measured, simultaneously with the clamping effort applied at the joint and the deformation of the metal gasket. The integrity to clamping effort ratio curve is not retraced in reverse upon relaxation of the clamping effort, but a 'return curve' analogous to a hysteresis cycle explains why certain types of joint retain their integrity at high temperatures. The use of a tracer gas permits discrimination between external permeation of the joint and gas from occlusions between its mating surfaces. The authors have been led to consider that neither the nature nor the purity or surface condition of the joint have any basic influence on its integrity. Clamping effort values in respect of various joints and necessary for total integrity are indicated. Reprint of a paper published in Le vide, no. 82, Jul-Aug 1959 [French] L'etude de differents types de joints metalliques etanches, en vue de leur application a l'ultra-vide, a ete effectuee a l'aide d'un detecteur de fuite a helium. On a mesure simultanement le debit de fuite, l'effort applique sur le joint et sa deformation. On a reussi a mesurer des debits de fuite de l'ordre de 2 x 10{sup -12} cm{sup 3} Atm/s/m de joint pour l'air. La courbe de l'etancheite en fonction de l'effort applique n'est pas reversible et on a pu mettre en evidence un 'cycle d'hysteresis' qui explique que certains joints conservent leur etancheite a haute temperature. La methode de mesure d'etancheite au moyen d'un gaz traceur a amene a faire une distinction entre la permeation et le degazage des gaz occlus dans l'interface des joints et a considerer que ni la nature, ni la purete et ni l'etat de surface du joint n'ont une influence primordiale sur l'etancheite de joint. Des valeurs

  8. Theoretical and Experimental Studies of High-Frequency Plasma Structures; Etudes Theoriques et Experimentales sur les Structures HF a Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Consoli, T. [CEA, Centre d' Etudes Nucleaires de Saclay (France)

    1969-03-15

    currents of more than 20 keV and of about 10 mA/cm{sub 2} were obtained. Ion entrainment for a magnetic field twice that necessary for resonance was also verified. Finally, with the Pleiade I device ({lambda} = 100 cm, P{sub HF} {approx}500 W, CW), the reflection of accelerated plasma jets by a mirror pulse lasting 75 {mu}s was verified. From measurements of the fast neutrals resulting from ion charge exchange (with the residual gas; p {<=} 10{sup -4} mmHg) it was deduced that the density of the ions (directed energy {approx} 1.5 keV) may be increased from 2 x 10{sub 8} cm{sup -3} (direct beam) to 6 x 10{sup 9} cm{sup -3} during the mirror pulse. The accumulated density appears to be limited by the charge exchange, and the increased duration of the mirror pulse to 200 {mu}s with p Less-Than-Or-Equivalent-To 10{sup -4} mmHg (unchanged) hardly improves the accumulation ratio. This agrees with the predictions if one takes into account the fact that the ion lifetime is {approx} 10 {mu}s. (author) [French] Il s'agit des etudes sur les structures HF a la resonance ( {omega}{sub ec} = {omega}{sub HF}) en champ magnetique inhomogene. Les points suivants ont ete developpes theoriquement: description analytique complete (relativiste et non lineaire) du mouvement individuel, compte tenu du fait que le nombre de revolutions des particules dans la zone de resonance est eleve ; etude du champ de charge d' espace autocoherent ( 'self-consistent') en vue d'etablir les conditions pour que l' energie des ions soit de l'ordre de celle gagnee par les electrons dans la zone de resonance; calcul du champ HF autocoherent dans le plasma accelere en vue d' etablir les conditions de fonctionnement optimum de l'accelerateur HF; probleme des pertes aux miroirs. Les resultats experimentaux ont ete obtenus avec divers dispositifs construits en vue de la verification des previsions theoriques.

  9. The effect of an homogeneous magnetic field on the line profiles of hydrogen; Effet d'un champ magnetique uniforme sur les profils des raies de l'hydrogene

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, H; Herman, L [Universite de Paris Sorbonne, Lab. de Recherche Physique, 75 - Paris (France); Drawin, H W [Association Euratom-CEA, Centre d' Etudes Nucleaires de Fontenay-aux-Roses, 92 (France)

    1966-07-01

    The profiles of the hydrogen lines have been calculated taking into account the intermolecular electric field, the electronic collisions, and an external homogeneous magnetic field in which the plasma is imbedded. We considered electron densities N within the range 10{sup 15} {<=} N {<=} 10{sup 18} cm{sup -3} and magnetic field strengths < 1,2 10{sup 5} gauss. These values cover practically most of the experimental conditions in which one is interested in the present state of research. In the present paper we only present the numerical results for the lines Ly-{alpha}, Ly-{beta} and H-{alpha}. For very small magnetic fields our calculated line profiles coincide with the pure Stark profiles recently calculated by GRIEM, KOLB and SHEN (1960). With increasing magnetic fields, important deviations appear. The essential parameters for these deviations are, firstly: the direction of observation with regard to the direction of the magnetic field, and secondly: the ratio between the Zeeman splitting in a magnetic field only and the Stark splitting due to the mean intermolecular electric field. Experimental line profiles have been obtained using a linear discharge tube surrounded by an induction coil, the comparison of tie theoretical profiles with the experimental ones shows a satisfying agreement. The results for the lines originating from higher principal quantum numbers are actually exploited and will be communicated soon. (author) [French] Les profils des raies de l'hydrogene ont ete calcules en tenant compte des collisions electroniques, du champ electrique intermoleculaire et d'un champ magnetique uniforme exterieur. Nous avons considere des concentrations electroniques comprises entre 10{sup 15} cm{sup -3} et 10{sup 18} cm{sup -3} et des champs magnetiques inferieurs ou egaux a 1,2 10{sup 5} gauss. Ces valeurs couvrent pratiquement toutes les conditions experimentales qui ont un interet a l'heure actuelle. Dans le present travail, nous ne donnons que des resultats

  10. Higher-order asymptotic homogenization of periodic materials with low scale separation

    NARCIS (Netherlands)

    Ameen, M.M.; Peerlings, R.H.J.; Geers, M.G.D

    2016-01-01

    In this work, we investigate the limits of classical homogenization theories pertaining to homogenization of periodic linear elastic composite materials at low scale separations and demonstrate the effectiveness of higher-order periodic homogenization in alleviating this limitation. Classical

  11. Interpretation of criticality experiments on homogeneous solutions of plutonium and uranium; Interpretation des experiences de criticite sur des solutions homogenes de plutonium et d'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Ithurralde, M F; Kremser, J; Leclerc, J; Lombard, Ch; Moreau, J; Robin, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    Criticality experiments on solutions of fissionable materials have been carried out in tanks of various geometries (cylinder, isolated annular cylinder, interacting annular cylinders); the reflexion conditions have also been varied (without reflection, semi-reflection and total reflexion by water). The range of the studied concentrations is rather large (18,8 to 104 gms/liter). The interpretation of these experiments has been undertaken in order to resolve the problems of the industrial use of homogeneous plutonium and uranium solutions. Several methods the fields of application of which are different have been used: diffusion method, transport method and Monte-Carlo method. (authors) [French] Des experiences critiques sur des solutions de matieres fissiles ont ete faites dans des cuves de diverses geometries (cylindre, cylindre annulaire isole, cylindre annulaire en interaction), les conditions de reflexion ont ete egalement variees (sans reflexion, semi reflexion et reflexion totale par l'eau). La gamme des concentrations etudiees est assez etendue (18,8 a 104 g/l ). L'interpretation de ces experiences a ete entreprise dans le but de pouvoir resoudre les problemes poses par l'emploi industriel de solutions homogenes de plutonium et d'uranium, plusieurs methodes dont les domaines d'application sont differents ont ete employees: methode de diffusion, methode de transport, methode de Monte-Carlo. (auteurs)

  12. Homogeneous nucleation in 4He: A corresponding-states analysis

    International Nuclear Information System (INIS)

    Sinha, D.N.; Semura, J.S.; Brodie, L.C.

    1982-01-01

    We report homogeneous-nucleation-temperature measurements in liquid 4 He over a bath-temperature range 2.31 4 He, in a region far from the critical point. A simple empirical form is presented for estimating the homogeneous nucleation temperatures for any liquid with a spherically symmetric interatomic potential. The 4 He data are compared with nucleation data for Ar, Kr, Xe, and H; theoretical predictions for 3 He are given in terms of reduced quantities. It is shown that the nucleation data for both quantum and classical liquids obey a quantum law of corresponding states (QCS). On the basis of this QCS analysis, predictions of homogeneous nucleation temperatures are made for hydrogen isotopes such as HD, DT, HT, and T 2

  13. Radiotracer application in determining changes in cement mix homogeneity

    International Nuclear Information System (INIS)

    Breda, M.

    1979-01-01

    A small amount of cement labelled with 24 Na is added to the concrete mix and the relative activity of the mix is measured using a scintillation detector in preset points at different time intervals of the mixing process. The detector picks up information from a volume of 10 to 15 litres. The values characterize the degree of homogeneity of the cement component in the mix. Mathematical statistics methods are used for assessing mixing or the homogeneity changes. The technique is quick and simple and is used to advantage in determining the effect of the duration and method of transport of the cement mix on its homogeneity, and in monitoring the mixing process and determining the minimum mixing time for all types of concrete mix. (M.S.)

  14. Homogeneous-heterogeneous reactions in curved channel with porous medium

    Science.gov (United States)

    Hayat, T.; Ayub, Sadia; Alsaedi, A.

    2018-06-01

    Purpose of the present investigation is to examine the peristaltic flow through porous medium in a curved conduit. Problem is modeled for incompressible electrically conducting Ellis fluid. Influence of porous medium is tackled via modified Darcy's law. The considered model utilizes homogeneous-heterogeneous reactions with equal diffusivities for reactant and autocatalysis. Constitutive equations are formulated in the presence of viscous dissipation. Channel walls are compliant in nature. Governing equations are modeled and simplified under the assumptions of small Reynolds number and large wavelength. Graphical results for velocity, temperature, heat transfer coefficient and homogeneous-heterogeneous reaction parameters are examined for the emerging parameters entering into the problem. Results reveal an activation in both homogenous-heterogenous reaction effect and heat transfer rate with increasing curvature of the channel.

  15. Cryogenic homogenization and sampling of heterogeneous multi-phase feedstock

    Science.gov (United States)

    Doyle, Glenn Michael; Ideker, Virgene Linda; Siegwarth, James David

    2002-01-01

    An apparatus and process for producing a homogeneous analytical sample from a heterogenous feedstock by: providing the mixed feedstock, reducing the temperature of the feedstock to a temperature below a critical temperature, reducing the size of the feedstock components, blending the reduced size feedstock to form a homogeneous mixture; and obtaining a representative sample of the homogeneous mixture. The size reduction and blending steps are performed at temperatures below the critical temperature in order to retain organic compounds in the form of solvents, oils, or liquids that may be adsorbed onto or absorbed into the solid components of the mixture, while also improving the efficiency of the size reduction. Preferably, the critical temperature is less than 77 K (-196.degree. C.). Further, with the process of this invention the representative sample may be maintained below the critical temperature until being analyzed.

  16. Variable valve timing in a homogenous charge compression ignition engine

    Science.gov (United States)

    Lawrence, Keith E.; Faletti, James J.; Funke, Steven J.; Maloney, Ronald P.

    2004-08-03

    The present invention relates generally to the field of homogenous charge compression ignition engines, in which fuel is injected when the cylinder piston is relatively close to the bottom dead center position for its compression stroke. The fuel mixes with air in the cylinder during the compression stroke to create a relatively lean homogeneous mixture that preferably ignites when the piston is relatively close to the top dead center position. However, if the ignition event occurs either earlier or later than desired, lowered performance, engine misfire, or even engine damage, can result. The present invention utilizes internal exhaust gas recirculation and/or compression ratio control to control the timing of ignition events and combustion duration in homogeneous charge compression ignition engines. Thus, at least one electro-hydraulic assist actuator is provided that is capable of mechanically engaging at least one cam actuated intake and/or exhaust valve.

  17. Radiation Resistance and Gain of Homogeneous Ring Quasi-Array

    DEFF Research Database (Denmark)

    Knudsen, H. L.

    1954-01-01

    In a previous paper homogeneous ring quasi-arrays of tangential or radial dipoles were introduced, i.e. systems of dipoles arranged equidistantly along a circle, the dipoles being oriented in tangential or radial directions and carrying currents with the same amplitude, but with a phase that incr......In a previous paper homogeneous ring quasi-arrays of tangential or radial dipoles were introduced, i.e. systems of dipoles arranged equidistantly along a circle, the dipoles being oriented in tangential or radial directions and carrying currents with the same amplitude, but with a phase...... that increases uniformly along the circle. Such quasi-arrays are azimuthally omnidirectional, and the radiated field will be mainly horizontally polarized and concentrated around the plane of the circle. In this paper expressions are obtained for the radiation resistance and the gain of homogeneous ring quasi...

  18. Heterogenization of Homogeneous Catalysts: the Effect of the Support

    Energy Technology Data Exchange (ETDEWEB)

    Earl, W.L.; Ott, K.C.; Hall, K.A.; de Rege, F.M.; Morita, D.K.; Tumas, W.; Brown, G.H.; Broene, R.D.

    1999-06-29

    We have studied the influence of placing a soluble, homogeneous catalyst onto a solid support. We determined that such a 'heterogenized' homogeneous catalyst can have improved activity and selectivity for the asymmetric hydrogenation of enamides to amino acid derivatives. The route of heterogenization of RhDuPhos(COD){sup +} cations occurs via electrostatic interactions with anions that are capable of strong hydrogen bonding to silica surfaces. This is a novel approach to supported catalysis. Supported RhDuPhos(COD){sup +} is a recyclable, non-leaching catalyst in non-polar media. This is one of the few heterogenized catalysts that exhibits improved catalytic performance as compared to its homogeneous analog.

  19. Soluble Molecularly Imprinted Nanorods for Homogeneous Molecular Recognition

    Directory of Open Access Journals (Sweden)

    Rongning Liang

    2018-03-01

    Full Text Available Nowadays, it is still difficult for molecularly imprinted polymers (MIPs to achieve homogeneous recognition since they cannot be easily dissolved in organic or aqueous phase. To address this issue, soluble molecularly imprinted nanorods have been synthesized by using soluble polyaniline doped with a functionalized organic protonic acid as the polymer matrix. By employing 1-naphthoic acid as a model, the proposed imprinted nanorods exhibit an excellent solubility and good homogeneous recognition ability. The imprinting factor for the soluble imprinted nanoroads is 6.8. The equilibrium dissociation constant and the apparent maximum number of the proposed imprinted nanorods are 248.5 μM and 22.1 μmol/g, respectively. We believe that such imprinted nanorods may provide an appealing substitute for natural receptors in homogeneous recognition related fields.

  20. Soluble Molecularly Imprinted Nanorods for Homogeneous Molecular Recognition

    Science.gov (United States)

    Liang, Rongning; Wang, Tiantian; Zhang, Huan; Yao, Ruiqing; Qin, Wei

    2018-03-01

    Nowadays, it is still difficult for molecularly imprinted polymer (MIPs) to achieve homogeneous recognition since they cannot be easily dissolved in organic or aqueous phase. To address this issue, soluble molecularly imprinted nanorods have been synthesized by using soluble polyaniline doped with a functionalized organic protonic acid as the polymer matrix. By employing 1-naphthoic acid as a model, the proposed imprinted nanorods exhibit an excellent solubility and good homogeneous recognition ability. The imprinting factor for the soluble imprinted nanoroads is 6.8. The equilibrium dissociation constant and the apparent maximum number of the proposed imprinted nanorods are 248.5 μM and 22.1 μmol/g, respectively. We believe that such imprinted nanorods may provide an appealing substitute for natural receptors in homogeneous recognition related fields.

  1. Homogeneous versus heterogeneous shielding modeling of spent-fuel casks

    International Nuclear Information System (INIS)

    Carbajo, J.J.; Lindner, C.N.

    1992-01-01

    The design of spent-fuel casks for storage and transport requires modeling the cask for criticality, shielding, thermal, and structural analyses. While some parts of the cask are homogeneous, other regions are heterogeneous with different materials intermixed. For simplicity, some of the heterogeneous regions may be modeled as homogeneous. This paper evaluates the effect of homogenizing some regions of a cask on calculating radiation dose rates outside the cask. The dose rate calculations were performed with the one-dimensional discrete ordinates shielding XSDRNPM code coupled with the XSDOSE code and with the three-dimensional QAD-CGGP code. Dose rates were calculated radially at the midplane of the cask at two locations, cask surface and 2.3 m from the radial surface. The last location corresponds to a point 2 m from the lateral sides of a transport railroad car

  2. Method of the characteristics for calculation of VVER without homogenization

    Energy Technology Data Exchange (ETDEWEB)

    Suslov, I.R.; Komlev, O.G.; Novikova, N.N.; Zemskov, E.A.; Tormyshev, I.V.; Melnikov, K.G.; Sidorov, E.B. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)

    2005-07-01

    The first stage of the development of characteristics code MCCG3D for calculation of the VVER-type reactor without homogenization is presented. The parallel version of the code for MPI was developed and tested on cluster PC with LINUX-OS. Further development of the MCCG3D code for design-level calculations with full-scale space-distributed feedbacks is discussed. For validation of the MCCG3D code we use the critical assembly VENUS-2. The geometrical models with and without homogenization have been used. With both models the MCCG3D results agree well with the experimental power distribution and with results generated by the other codes, but model without homogenization provides better results. The perturbation theory for MCCG3D code is developed and implemented in the module KEFSFGG. The calculations with KEFSFGG are in good agreement with direct calculations. (authors)

  3. Does prescribed burning result in biotic homogenization of coastal heathlands?

    Science.gov (United States)

    Velle, Liv Guri; Nilsen, Liv Sigrid; Norderhaug, Ann; Vandvik, Vigdis

    2014-05-01

    Biotic homogenization due to replacement of native biodiversity by widespread generalist species has been demonstrated in a number of ecosystems and taxonomic groups worldwide, causing growing conservation concern. Human disturbance is a key driver of biotic homogenization, suggesting potential conservation challenges in seminatural ecosystems, where anthropogenic disturbances such as grazing and burning are necessary for maintaining ecological dynamics and functioning. We test whether prescribed burning results in biotic homogenization in the coastal heathlands of north-western Europe, a seminatural landscape where extensive grazing and burning has constituted the traditional land-use practice over the past 6000 years. We compare the beta-diversity before and after fire at three ecological scales: within local vegetation patches, between wet and dry heathland patches within landscapes, and along a 470 km bioclimatic gradient. Within local patches, we found no evidence of homogenization after fire; species richness increased, and the species that entered the burnt Calluna stands were not widespread specialists but native grasses and herbs characteristic of the heathland system. At the landscapes scale, we saw a weak homogenization as wet and dry heathland patches become more compositionally similar after fire. This was because of a decrease in habitat-specific species unique to either wet or dry habitats and postfire colonization by a set of heathland specialists that established in both habitat types. Along the bioclimatic gradient, species that increased after fire generally had more specific environmental requirements and narrower geographical distributions than the prefire flora, resulting in a biotic 'heterogenisation' after fire. Our study demonstrates that human disturbance does not necessarily cause biotic homogenization, but that continuation of traditional land-use practices can instead be crucial for the maintenance of the diversity and ecological

  4. Stochastic model of milk homogenization process using Markov's chain

    Directory of Open Access Journals (Sweden)

    A. A. Khvostov

    2016-01-01

    Full Text Available The process of development of a mathematical model of the process of homogenization of dairy products is considered in the work. The theory of Markov's chains was used in the development of the mathematical model, Markov's chain with discrete states and continuous parameter for which the homogenisation pressure is taken, being the basis for the model structure. Machine realization of the model is implemented in the medium of structural modeling MathWorks Simulink™. Identification of the model parameters was carried out by minimizing the standard deviation calculated from the experimental data for each fraction of dairy products fat phase. As the set of experimental data processing results of the micrographic images of fat globules of whole milk samples distribution which were subjected to homogenization at different pressures were used. Pattern Search method was used as optimization method with the Latin Hypercube search algorithm from Global Optimization Тoolbox library. The accuracy of calculations averaged over all fractions of 0.88% (the relative share of units, the maximum relative error was 3.7% with the homogenization pressure of 30 MPa, which may be due to the very abrupt change in properties from the original milk in the particle size distribution at the beginning of the homogenization process and the lack of experimental data at homogenization pressures of below the specified value. The mathematical model proposed allows to calculate the profile of volume and mass distribution of the fat phase (fat globules in the product, depending on the homogenization pressure and can be used in the laboratory and research of dairy products composition, as well as in the calculation, design and modeling of the process equipment of the dairy industry enterprises.

  5. Measurements of spectral indices in homogeneous multiplying media; Mesures d'indices de spectre dans les milieux multiplicateurs homogenes

    Energy Technology Data Exchange (ETDEWEB)

    Bruna, J G; Brunet, J P; Clouet D' Orval, Ch; Verriere, Ph; Kremser, J; Moret-Bailly, J; Tellier, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    Methods for computation of spectra in light water are developed at Saclay and it is interesting to carry out at the same time experimental studies of simple media such as solutions of fissionable salts which allow quite direct comparisons with computed values. The spectral indices measurements were made with two small fission chambers, one containing deposited plutonium, the other deposited uranium 235. Their response, when neutron spectrum is modified, allows to study the epithermal part of the flux. The media studied with these chambers are fissionable solutions (of plutonium or 90 per cent enriched uranium) which were made critical in bare cylindrical geometry in the Alecto reactor. If the ratio of the chambers is normalized to unity in a Maxwell spectrum, then the noted variation of the ratio of the counts Pu chamber/ U{sup 235} chamber reaches 1,4 in the range of the studied concentrations. (authors) [French] Des calculs de spectres dans l'eau legere sont mis au point a Saclay et il est interessant de mener parallelement des etudes experimentale sur des milieux simples tels que des solutions de sels fissiles, qui permettent des comparaisons tres directes avec les valeurs calculees. On a choisi d'effectuer des mesures d' 'indices de spectres' a l'aide de de deux petites chambres a fission contenant des depots, l'une de plutonium, l'autre d'uranium 235. Leur reponse lorsque le spectre des neutrons est modifie permet d'etudier la partie epithermique du flux. Les milieux etudies a l'aide de ces chambres sont des solutions fissiles (plutonium ou uranium enrichi a 90 pour cent) rendus critiques, en geometrie cylindrique nue, dans le reacteur Alecto. Si le rapport des chambres est normalise a un dans un spectre de Maxwell, la variation constatee du rapport des comptages chambre Pu/ chambre U{sup 235} atteint, dans les gammes de concentrations etudiees, 1,4. (auteurs)

  6. A homogeneous cooling scheme investigation for high power slab laser

    Science.gov (United States)

    He, Jianguo; Lin, Weiran; Fan, Zhongwei; Chen, Yanzhong; Ge, Wenqi; Yu, Jin; Liu, Hao; Mo, Zeqiang; Fan, Lianwen; Jia, Dan

    2017-10-01

    The forced convective heat transfer with the advantages of reliability and durability is widely used in cooling the laser gain medium. However, a flow direction induced temperature gradient always appears. In this paper, a novel cooling configuration based on longitudinal forced convective heat transfer is presented. In comparison with two different types of configurations, it shows a more efficient heat transfer and more homogeneous temperature distribution. The investigation of the flow rate reveals that the higher flow rate the better cooling performance. Furthermore, the simulation results with 20 L/min flow rate shows an adequate temperature level and temperature homogeneity which keeps a lower hydrostatic pressure in the flow path.

  7. Early capillary flux homogenization in response to neural activation.

    Science.gov (United States)

    Lee, Jonghwan; Wu, Weicheng; Boas, David A

    2016-02-01

    This Brief Communication reports early homogenization of capillary network flow during somatosensory activation in the rat cerebral cortex. We used optical coherence tomography and statistical intensity variation analysis for tracing changes in the red blood cell flux over hundreds of capillaries nearly at the same time with 1-s resolution. We observed that while the mean capillary flux exhibited a typical increase during activation, the standard deviation of the capillary flux exhibited an early decrease that happened before the mean flux increase. This network-level data is consistent with the theoretical hypothesis that capillary flow homogenizes during activation to improve oxygen delivery. © The Author(s) 2015.

  8. How to determine composite material properties using numerical homogenization

    DEFF Research Database (Denmark)

    Andreassen, Erik; Andreasen, Casper Schousboe

    2014-01-01

    Numerical homogenization is an efficient way to determine effective macroscopic properties, such as the elasticity tensor, of a periodic composite material. In this paper an educational description of the method is provided based on a short, self-contained Matlab implementation. It is shown how...... the basic code, which computes the effective elasticity tensor of a two material composite, where one material could be void, is easily extended to include more materials. Furthermore, extensions to homogenization of conductivity, thermal expansion, and fluid permeability are described in detail. The unit...

  9. Homogenization of long fiber reinforced composites including fiber bending effects

    DEFF Research Database (Denmark)

    Poulios, Konstantinos; Niordson, Christian Frithiof

    2016-01-01

    This paper presents a homogenization method, which accounts for intrinsic size effects related to the fiber diameter in long fiber reinforced composite materials with two independent constitutive models for the matrix and fiber materials. A new choice of internal kinematic variables allows...... of the reinforcing fibers is captured by higher order strain terms, resulting in an accurate representation of the micro-mechanical behavior of the composite. Numerical examples show that the accuracy of the proposed model is very close to a non-homogenized finite-element model with an explicit discretization...

  10. Preparation of homogeneous isotopic targets with rotating substrate

    International Nuclear Information System (INIS)

    Xu, G.J.; Zhao, Z.G.

    1993-01-01

    Isotopically enriched accelerator targets were prepared using the evaporation-condensation method from a resistance heating crucible. For high collection efficiency and good homogeneity the substrate was rotated at a vertical distance of 1.3 to 2.5 cm from the evaporation source. Measured collection efficiencies were 13 to 51 μg cm -2 mg -1 and homogeneity tests showed values close to the theoretically calculated ones for a point source. Targets, selfsupporting or on backings, could be fabricated with this method for elements and some compounds with evaporation temperatures up to 2300 K. (orig.)

  11. A critical review of homogenization techniques in reactor lattices

    International Nuclear Information System (INIS)

    Benoist, P.

    1983-01-01

    The determination of the shape of the neutron flux in a whole reactor is, at the time being, a much too complex problem to be treated by transport theory. Since the earlier times of reactor theory, the necessity appeared to solve the problem in two steps. First the reactor is divided into zones, each of them forming a regular lattice. In each of these zones, homogenized parameters are determined by transport theory, in order to define an equivalent smeared medium. In a second step, these parameters are introduced in a diffusion theory scheme in order to treat the reactor as a whole. This is the homogenization procedure. 14 refs

  12. Relativistic cosmologies with closed, locally homogeneous space sections

    International Nuclear Information System (INIS)

    Fagundes, H.V.

    1985-01-01

    The homogeneous Bianchi and Kantowski-Sachs metrics of relativistic cosmology are investigated through their correspondence with recent geometrical results of Thurston. These allow a partial classification of the topologies for closed, locally homogeneous spaces according to Thurston's eight geometric types. Besides, which of the Bianchi-Kantowski-Sachs metrics can be imposed on closed space sections of cosmological models are learned. This is seen as a progress toward implementation of a postulate of the closure of space for both classical and quantum gravity. (Author) [pt

  13. Control rod homogenization in heterogeneous sodium-cooled fast reactors

    International Nuclear Information System (INIS)

    Andersson, Mikael

    2016-01-01

    The sodium-cooled fast reactor is one of the candidates for a sustainable nuclear reactor system. In particular, the French ASTRID project employs an axially heterogeneous design, proposed in the so-called CFV (low sodium effect) core, to enhance the inherent safety features of the reactor. This thesis focuses on the accurate modeling of the control rods, through the homogenization method. The control rods in a sodium-cooled fast reactor are used for reactivity compensation during the cycle, power shaping, and to shutdown the reactor. In previous control rod homogenization procedures, only a radial description of the geometry was implemented, hence the axially heterogeneous features of the CFV core could not be taken into account. This thesis investigates the different axial variations the control rod experiences in a CFV core, to determine the impact that these axial environments have on the control rod modeling. The methodology used in this work is based on previous homogenization procedures, the so-called equivalence procedure. The procedure was newly implemented in the PARIS code system in order to be able to use 3D geometries, and thereby be take axial effects into account. The thesis is divided into three parts. The first part investigates the impact of different neutron spectra on the homogeneous control-rod cross sections. The second part investigates the cases where the traditional radial control-rod homogenization procedure is no longer applicable in the CFV core, which was found to be 5-10 cm away from any material interface. In the third part, based on the results from the second part, a 3D model of the control rod is used to calculate homogenized control-rod cross sections. In a full core model, a study is made to investigate the impact these axial effects have on control rod-related core parameters, such as the control rod worth, the capture rates in the control rod, and the power in the adjacent fuel assemblies. All results were compared to a Monte

  14. A critical review of homogenization techniques in reactor lattices

    International Nuclear Information System (INIS)

    Benoist, P.

    1983-01-01

    The determination of the shape of the neutron flux in a whole reactor is, at the time being, a much too complex problem to be treated by transport theory. Since the earlier times of reactor theory, the necessity appeared to solve the problem in two steps. First the reactor is divided into zones, each of them forming a regular lattice. In each of these zones, homogenized parameters are determined by transport theory, in order to define an equivalent smeared medium. In a second step, these parameters are introduced in a diffusion theory scheme in order to treat the reactor as a whole. This is the homogenization procedure

  15. A homogeneous catalogue of quasar candidates found with slitless spectroscopy

    International Nuclear Information System (INIS)

    Beauchemin, M.; Borra, E.F.; Edwards, G.

    1990-01-01

    This paper gives a list of all quasar candidates obtained from an automated computer search performed on 11 grens plates. The description of the main characteristics of the survey is given along with the latest improvements in the selection techniques. Particular attention has been paid to understanding and quantifying selection effects. This allows the construction of homogeneous samples having well-understood characteristics. The noteworthy aspect of our homogenization process is the correction that we apply to our probability classes in order to take into account the signal-to-noise differences; at a given magnitude, among plates of different limiting magnitudes. (author)

  16. Homogeneity tests for variances and mean test under heterogeneity conditions in a single way ANOVA method

    International Nuclear Information System (INIS)

    Morales P, J.R.; Avila P, P.

    1996-01-01

    If we have consider the maximum permissible levels showed for the case of oysters, it results forbidding to collect oysters at the four stations of the El Chijol Channel ( Veracruz, Mexico), as well as along the channel itself, because the metal concentrations studied exceed these limits. In this case the application of Welch tests were not necessary. For the water hyacinth the means of the treatments were unequal in Fe, Cu, Ni, and Zn. This case is more illustrative, for the conclusion has been reached through the application of the Welch tests to treatments with heterogeneous variances. (Author)

  17. Impact of homogenization and protein extraction conditions on the obtained tobacco pollen proteomic patterns

    Czech Academy of Sciences Publication Activity Database

    Fíla, Jan; Čapková, Věra; Feciková, Jana; Honys, David

    2011-01-01

    Roč. 55, č. 3 (2011), s. 499-506 ISSN 0006-3134 R&D Projects: GA MŠk OC08011; GA ČR(CZ) GAP501/11/1462 Institutional research plan: CEZ:AV0Z50380511 Keywords : proteomics * Roche MagNA Lyser Instrument * ARABIDOPSIS-THALIANA Subject RIV: ED - Physiology Impact factor: 1.974, year: 2011

  18. A Comparison of the Developmental Impact of Homogeneous and Heterogeneous Housing Conditions on Freshmen.

    Science.gov (United States)

    Cade, Sharon M.

    1979-01-01

    Examines changes in students' sense of autonomy and in their ability to manage their emotions, as described by Chickering's vectors, in relation to residence hall environments. Results neither support nor refute the all-freshman hall. Participants moved developmentally along the Autonomy Scale. Freshman women increased their scores on the Impulse…

  19. Diurnal Variations of the Flux Imbalance Over Homogeneous and Heterogeneous Landscapes

    Science.gov (United States)

    Zhou, Yanzhao; Li, Dan; Liu, Heping; Li, Xin

    2018-05-01

    It is well known that the sum of the turbulent sensible and latent heat fluxes as measured by the eddy-covariance method is systematically lower than the available energy (i.e., the net radiation minus the ground heat flux). We examine the separate and joint effects of diurnal and spatial variations of surface temperature on this flux imbalance in a dry convective boundary layer using the Weather Research and Forecasting model. Results show that, over homogeneous surfaces, the flux due to turbulent-organized structures is responsible for the imbalance, whereas over heterogeneous surfaces, the flux due to mesoscale or secondary circulations is the main contributor to the imbalance. Over homogeneous surfaces, the flux imbalance in free convective conditions exhibits a clear diurnal cycle, showing that the flux-imbalance magnitude slowly decreases during the morning period and rapidly increases during the afternoon period. However, in shear convective conditions, the flux-imbalance magnitude is much smaller, but slightly increases with time. The flux imbalance over heterogeneous surfaces exhibits a diurnal cycle under both free and shear convective conditions, which is similar to that over homogeneous surfaces in free convective conditions, and is also consistent with the general trend in the global observations. The rapid increase in the flux-imbalance magnitude during the afternoon period is mainly caused by the afternoon decay of the turbulent kinetic energy (TKE). Interestingly, over heterogeneous surfaces, the flux imbalance is linearly related to the TKE and the difference between the potential temperature and surface temperature, ΔT; the larger the TKE and ΔT values, the smaller the flux-imbalance magnitude.

  20. FEMB, 2-D Homogeneous Neutron Diffusion in X-Y Geometry with Keff Calculation, Dyadic Fission Matrix

    International Nuclear Information System (INIS)

    Misfeldt, I.B.

    1987-01-01

    1 - Nature of physical problem solved: The two-dimensional neutron diffusion equation (xy geometry) is solved in the homogeneous form (K eff calculation). The boundary conditions specify each group current as a linear homogeneous function of the group fluxes (gamma matrix concept). For each material, the fission matrix is assumed to be dyadic. 2 - Method of solution: Finite element formulation with Lagrange type elements. Solution technique: SOR with extrapolation. 3 - Restrictions on the complexity of the problem: Maximum order of the Lagrange elements is 6