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Journal articles on the topic 'Particules coalescentes'
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1
Gnedin, Alexander, Alexander Iksanov, and Alexander Marynych. "On Λ-Coalescents with Dust Component." Journal of Applied Probability 48, no. 04 (December 2011): 1133–51. http://dx.doi.org/10.1017/s0021900200008664.
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We consider the Λ-coalescent processes with a positive frequency of singleton clusters. The class in focus covers, for instance, the beta(a,b)-coalescents witha> 1. We show that some large-sample properties of these processes can be derived by coupling the coalescent with an increasing Lévy process (subordinator), and by exploiting parallels with the theory of regenerative composition structures. In particular, we discuss the limit distributions of the absorption time and the number of collisions.
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Gnedin, Alexander, Alexander Iksanov, and Alexander Marynych. "On Λ-Coalescents with Dust Component." Journal of Applied Probability 48, no. 4 (December 2011): 1133–51. http://dx.doi.org/10.1239/jap/1324046023.
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We consider the Λ-coalescent processes with a positive frequency of singleton clusters. The class in focus covers, for instance, the beta(a, b)-coalescents with a > 1. We show that some large-sample properties of these processes can be derived by coupling the coalescent with an increasing Lévy process (subordinator), and by exploiting parallels with the theory of regenerative composition structures. In particular, we discuss the limit distributions of the absorption time and the number of collisions.
3
Dhersin, Jean-Stéphane, and Linglong Yuan. "On the total length of external branches for beta-coalescents." Advances in Applied Probability 47, no. 03 (September 2015): 693–714. http://dx.doi.org/10.1017/s0001867800048795.
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In this paper we consider the beta(2 − α, α)-coalescents with 1 < α < 2 and study the moments of external branches, in particular, the total external branch lengthof an initial sample ofnindividuals. For this class of coalescents, it has been proved thatnα-1T(n)→DT, whereT(n)is the length of an external branch chosen at random andTis a known nonnegative random variable. For beta(2 − α, α)-coalescents with 1 < α < 2, we obtain limn→+∞n3α-5𝔼(Lext(n)−n2-α𝔼T)2= ((α − 1)Γ(α + 1))2Γ(4 − α) / ((3 − α)Γ(4 − 2α)).
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Dhersin, Jean-Stéphane, and Linglong Yuan. "On the total length of external branches for beta-coalescents." Advances in Applied Probability 47, no. 3 (September 2015): 693–714. http://dx.doi.org/10.1239/aap/1444308878.
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In this paper we consider the beta(2 − α, α)-coalescents with 1 < α < 2 and study the moments of external branches, in particular, the total external branch length of an initial sample of n individuals. For this class of coalescents, it has been proved that nα-1T(n) →DT, where T(n) is the length of an external branch chosen at random and T is a known nonnegative random variable. For beta(2 − α, α)-coalescents with 1 < α < 2, we obtain limn→+∞n3α-5 𝔼(Lext(n) − n2-α𝔼T)2 = ((α − 1)Γ(α + 1))2Γ(4 − α) / ((3 − α)Γ(4 − 2α)).
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Kamp, Johannes, Jörn Villwock, and Matthias Kraume. "Drop coalescence in technical liquid/liquid applications: a review on experimental techniques and modeling approaches." Reviews in Chemical Engineering 33, no. 1 (January 1, 2017): 1–47. http://dx.doi.org/10.1515/revce-2015-0071.
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AbstractThe coalescence phenomenon of drops in liquid/liquid systems is reviewed with particular focus on its technical relevance and application. Due to the complexity of coalescence, a comprehensive survey of the coalescence process and the numerous influencing factors is given. Subsequently, available experimental techniques with different levels of detail are summarized and compared. These techniques can be divided in simple settling tests for qualitative coalescence behavior investigations and gravity settler design, single-drop coalescence studies at flat interfaces as well as between droplets, and detailed film drainage analysis. To model the coalescence rate in liquid/liquid systems on a technical scale, the generic population balance framework is introduced. Additionally, different coalescence modeling approaches are reviewed with ascending level of detail from empirical correlations to comprehensive film drainage models and detailed computational fluid and particle dynamics.
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Clark, J. M. C., and V. Katsouros. "Stably coalescent stochastic froths." Advances in Applied Probability 31, no. 01 (March 1999): 199–219. http://dx.doi.org/10.1017/s0001867800009022.
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A model of a stochastic froth is introduced in which the rate of random coalescence of a pair of bubbles depends on an inverse power law of their sizes. The main question of interest is whether froths with a large number of bubbles can grow in a stable fashion; that is, whether under some time-varying change of scale the distributions of rescaled bubble sizes become approximately stationary. It is shown by way of a law of large numbers for the froths that the question can be re-interpreted in terms of a measure flow solving a nonlinear Boltzmann equation that represents an idealized deterministic froth. Froths turn out to be stable in the sense that there are scalings in which the rescaled measure flow is tight and, for a particular case, stable in the stronger sense that the rescaled flow converges to an equilibrium measure. Precise estimates are also given for the degree of tightness of the rescaled measure flows.
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Clark, J. M. C., and V. Katsouros. "Stably coalescent stochastic froths." Advances in Applied Probability 31, no. 1 (March 1999): 199–219. http://dx.doi.org/10.1239/aap/1029954273.
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A model of a stochastic froth is introduced in which the rate of random coalescence of a pair of bubbles depends on an inverse power law of their sizes. The main question of interest is whether froths with a large number of bubbles can grow in a stable fashion; that is, whether under some time-varying change of scale the distributions of rescaled bubble sizes become approximately stationary. It is shown by way of a law of large numbers for the froths that the question can be re-interpreted in terms of a measure flow solving a nonlinear Boltzmann equation that represents an idealized deterministic froth. Froths turn out to be stable in the sense that there are scalings in which the rescaled measure flow is tight and, for a particular case, stable in the stronger sense that the rescaled flow converges to an equilibrium measure. Precise estimates are also given for the degree of tightness of the rescaled measure flows.
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Castledine, Meaghan, Pawel Sierocinski, Daniel Padfield, and Angus Buckling. "Community coalescence: an eco-evolutionary perspective." Philosophical Transactions of the Royal Society B: Biological Sciences 375, no. 1798 (March 23, 2020): 20190252. http://dx.doi.org/10.1098/rstb.2019.0252.
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Community coalescence, the mixing of different communities, is widespread throughout microbial ecology. Coalescence can result in approximately equal contributions from the founding communities or dominance of one community over another. These different outcomes have ramifications for community structure and function in natural communities, and the use of microbial communities in biotechnology and medicine. However, we have little understanding of when a particular outcome might be expected. Here, we integrate existing theory and data to speculate on how a crucial characteristic of microbial communities—the type of species interaction that dominates the community—might affect the outcome of microbial community coalescence. Given the often comparable timescales of microbial ecology and microevolution, we explicitly consider ecological and evolutionary dynamics, and their interplay, in determining coalescence outcomes. This article is part of the theme issue ‘Conceptual challenges in microbial community ecology’.
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Dąbkowski, Dawid, Paweł Tabaszewski, and Paweł Górecki. "Minimizing the deep coalescence cost." Journal of Bioinformatics and Computational Biology 16, no. 05 (October 2018): 1840021. http://dx.doi.org/10.1142/s0219720018400218.
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Metagenomic studies identify the species present in an environmental sample usually by using procedures that match molecular sequences, e.g. genes, with the species taxonomy. Here, we first formulate the problem of gene-species matching in the parsimony framework using binary phylogenetic gene and species trees under the deep coalescence cost and the assumption that each gene is paired uniquely with one species. In particular, we solve the problem in the cases when one of the trees is a caterpillar. Next, we propose a dynamic programming algorithm, which solves the problem exactly, however, its time and space complexity is exponential. Next, we generalize the problem to include non-binary trees and show the solution for caterpillar trees. We then propose time and space-efficient heuristic algorithms for solving the gene-species matching problem for any input trees. Finally, we present the results of computational experiments on simulated and empirical datasets consisting of binary tree pairs.
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Reffas, S. A., M. Elmeguenni, and M. Benguediab. "Analysis of Void Growth and Coalescence in Porous Polymer Materials. Coalescence in Polymer Materials." Engineering, Technology & Applied Science Research 3, no. 3 (June 3, 2013): 452–60. http://dx.doi.org/10.48084/etasr.330.
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The use of polymeric materials in engineering applications is growing more and more all over the world. This issue requests new methodologies of analysis in order to assess the material’s capability to withstand complex loads. The use of polyacetal in engineering applications has increased rapidly in the last decade. In order to evaluate the behavior, the damage and coalescence of this type of polymer, a numerical method based on damage which occurs following several stages (nucleation of cavities, their growth and coalescence in more advanced stages of deformation) is proposed in this work. A particular attention is given on the stress-strain and the volumetric strain evolution under different triaxiality and for three initial void shapes. Its application to polyacetal allows approving this approach for technical polymers. Finally, this method allow us to compare the obtained results of basic calculations at different triaxiality and to discuss their possible influence on the initial size and the geometrical shape of the porosity on the material failure.
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Sprittles, James E., and Yulii D. Shikhmurzaev. "A parametric study of the coalescence of liquid drops in a viscous gas." Journal of Fluid Mechanics 753 (July 22, 2014): 279–306. http://dx.doi.org/10.1017/jfm.2014.362.
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AbstractThe coalescence of two liquid drops surrounded by a viscous gas is considered in the framework of the conventional model. The problem is solved numerically with particular attention paid to resolving the very initial stage of the process which only recently has become accessible both experimentally and computationally. A systematic study of the parameter space of practical interest allows the influence of the governing parameters in the system to be identified and the role of viscous gas to be determined. In particular, it is shown that the viscosity of the gas suppresses the formation of toroidal bubbles predicted in some cases by early computations where the gas’ dynamics was neglected. Focusing computations on the very initial stages of coalescence and considering the large parameter space allows us to examine the accuracy and limits of applicability of various ‘scaling laws’ proposed for different ‘regimes’ and, in doing so, reveal certain inconsistencies in recent works. A comparison with experimental data shows that the conventional model is able to reproduce many qualitative features of the initial stages of coalescence, such as a collapse of calculations onto a ‘master curve’ but, quantitatively, overpredicts the observed speed of coalescence and there are no free parameters to improve the fit. Finally, a phase diagram of parameter space, differing from previously published ones, is used to illustrate the key findings.
12
Gnedin, Alexander, Alex Iksanov, and Martin Möhle. "On Asymptotics of Exchangeable Coalescents with Multiple Collisions." Journal of Applied Probability 45, no. 04 (December 2008): 1186–95. http://dx.doi.org/10.1017/s0021900200005064.
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We study the number of collisions,Xn, of an exchangeable coalescent with multiple collisions (Λ-coalescent) which starts withnparticles and is driven by rates determined by a finite characteristic measure η(dx) =x−2Λ(dx). Via a coupling technique, we derive limiting laws ofXn, using previous results on regenerative compositions derived from stick-breaking partitions of the unit interval. The possible limiting laws ofXninclude normal, stable with index 1 ≤ α < 2, and Mittag-Leffler distributions. The results apply, in particular, to the case when η is a beta(a− 2,b) distribution with parametersa> 2 andb> 0. The approach taken allows us to derive asymptotics of three other functionals of the coalescent: the absorption time, the length of an external branch chosen at random from thenexternal branches, and the number of collision events that occur before the randomly selected external branch coalesces with one of its neighbours.
13
Gnedin, Alexander, Alex Iksanov, and Martin Möhle. "On Asymptotics of Exchangeable Coalescents with Multiple Collisions." Journal of Applied Probability 45, no. 4 (December 2008): 1186–95. http://dx.doi.org/10.1239/jap/1231340242.
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We study the number of collisions, Xn, of an exchangeable coalescent with multiple collisions (Λ-coalescent) which starts with n particles and is driven by rates determined by a finite characteristic measure η(dx) = x−2Λ(dx). Via a coupling technique, we derive limiting laws of Xn, using previous results on regenerative compositions derived from stick-breaking partitions of the unit interval. The possible limiting laws of Xn include normal, stable with index 1 ≤ α < 2, and Mittag-Leffler distributions. The results apply, in particular, to the case when η is a beta(a − 2, b) distribution with parameters a > 2 and b > 0. The approach taken allows us to derive asymptotics of three other functionals of the coalescent: the absorption time, the length of an external branch chosen at random from the n external branches, and the number of collision events that occur before the randomly selected external branch coalesces with one of its neighbours.
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Gilden, David, and T. Tajima. "Magnetic Field Reconnection in Differentially Rotating Accretion Disks." Symposium - International Astronomical Union 107 (1985): 477–82. http://dx.doi.org/10.1017/s0074180900075975.
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Differentially rotating accretion disks threaded by a uniform magnetic field have been numerically simulated. Fast reconnection followed by coalescence allows the magnetic field to drive small amplitude radial oscillations in the disk. These oscillations may be observable as the viscous stresses cause the disk to brighten and fade as the disk expands and contracts. Episodes of reconnection may also be observable as hot spots produced locally at the sites of coalescence. Cataclysmic variables, and in particular dwarf novae, provide a natural interpretation for these calculations.
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Wong, Louis Ngai Yuen. "A Review of Field Occurrence of Crack Types and Crack Coalescence in Rocks." Applied Mechanics and Materials 405-408 (September 2013): 191–202. http://dx.doi.org/10.4028/www.scientific.net/amm.405-408.191.
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This paper briefly reviews the literature on the general crack formation mechanisms and the typical occurrence of crack coalescence in natural rocks, but with no particular reference to specific locations or geologic settings. The field occurrences of tensile wing cracks, horsetail cracks, anticracks and shear cracks, as well as their coalescence are described. In contrast to the tensile wing cracks which develop in the tensile quadrant, anticracks develop from the pre-existing discontinuities in the compressive quadrant. The discussion will be illustrated with plenty of field examples, supplemented by a review of commonly used terminologies.
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Kawai, Stephen H. "Mobiles, Molecules and the Coalescence of Processes." Leonardo 46, no. 1 (February 2013): 30–35. http://dx.doi.org/10.1162/leon_a_00481.
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The author provides an account of his development and experiences as both a visual (mobile) artist and a chemist. He describes the surprising similarities between the planning of the construction of a mobile and the execution of retrosynthetic analysis used to chemically create a particular molecule. The fusion of these two independently initiated mental processes into a common creative act can be referred to as a coalescence of processes. The present article discusses the consequences of this merging for both artistic and scientific practices, as well as its relevance to the artscience concept of idea translation.
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Chand, A. K. B., and G. P. Kapoor. "Spline coalescence hidden variable fractal interpolation functions." Journal of Applied Mathematics 2006 (2006): 1–17. http://dx.doi.org/10.1155/jam/2006/36829.
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This paper generalizes the classical spline using a new construction of spline coalescence hidden variable fractal interpolation function (CHFIF). The derivative of a spline CHFIF is a typical fractal function that is self-affine or non-self-affine depending on the parameters of a nondiagonal iterated function system. Our construction generalizes the construction of Barnsley and Harrington (1989), when the construction is not restricted to a particular type of boundary conditions. Spline CHFIFs are likely to be potentially useful in approximation theory due to effects of the hidden variables and these effects are demonstrated through suitable examples in the present work.
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Alfonso, L., G. B. Raga, and D. Baumgardner. "The validity of the kinetic collection equation revisited." Atmospheric Chemistry and Physics 8, no. 4 (February 25, 2008): 969–82. http://dx.doi.org/10.5194/acp-8-969-2008.
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Abstract. The kinetic collection equation (KCE) describes the evolution of the average droplet spectrum due to successive events of collision and coalescence. Fluctuations and non-zero correlations present in the stochastic coalescence process would imply that the size distributions may not be correctly modeled by the KCE. In this study we expand the known analytical studies of the coalescence equation with some numerical tools such as Monte Carlo simulations of the coalescence process. The validity time of the KCE was estimated by calculating the maximum of the ratio of the standard deviation for the largest droplet mass over all the realizations to the averaged value. A good correspondence between the analytical and the numerical approaches was found for all the kernels. The expected values from analytical solutions of the KCE, were compared with true expected values of the stochastic collection equation (SCE) estimated with Gillespie's Monte Carlo algorithm and analytical solutions of the SCE, after and before the breakdown time. The possible implications for cloud physics are discussed, in particular the possibility of application of these results to kernels modified by turbulence and electrical processes.
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Alfonso, L., G. B. Raga, and D. Baumgardner. "The validity of the kinetic collection equation revisited." Atmospheric Chemistry and Physics Discussions 7, no. 5 (September 20, 2007): 13733–71. http://dx.doi.org/10.5194/acpd-7-13733-2007.
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Abstract. The kinetic collection equation (KCE) describes the evolution of the average droplet spectrum due to successive events of collision and coalescence. Fluctuations and non-zero correlations present in the stochastic coalescence process would imply that the size distributions may not be correctly modelled by the KCE. In this study we expand the known analytical studies of the coalescence equation with some numerical tools such as Monte Carlo simulations of the coalescence process. The validity time of the KCE was estimated by calculating the maximum of the ratio of the standard deviation for the largest droplet mass over all the realizations to the averaged value. A good correspondence between the analytical and the numerical approaches was found for all the kernels studied. The expected values from analytical solutions of the KCE, were compared with true expected values of the stochastic collection equation (SCE) estimated with Gillespie's Monte Carlo algorithm and analytical solutions of the SCE, after and before the breakdown time. The possible implications for cloud physics are discussed, in particular the possibility of application of these results to kernels modified by turbulence and electrical processes.
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Sprittles, James E., and Yulii D. Shikhmurzaev. "The coalescence of liquid drops in a viscous fluid: interface formation model." Journal of Fluid Mechanics 751 (June 24, 2014): 480–99. http://dx.doi.org/10.1017/jfm.2014.313.
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AbstractThe interface formation model is applied to describe the initial stages of the coalescence of two liquid drops in the presence of a viscous ambient fluid whose dynamics is fully accounted for. Our focus is on understanding (a) how this model’s predictions differ from those of the conventionally used one, (b) what influence the ambient fluid has on the evolution of the shape of the coalescing drops and (c) the coupling of the intrinsic dynamics of coalescence and that of the ambient fluid. The key feature of the interface formation model in its application to the coalescence phenomenon is that it removes the singularity inherent in the conventional model at the onset of coalescence and describes the part of the free surface ‘trapped’ between the coalescing volumes as they are pressed against each other as a rapidly disappearing ‘internal interface’. Considering the simplest possible formulation of this model, we find experimentally verifiable differences with the predictions of the conventional model showing, in particular, the effect of drop size on the coalescence process. According to the new model, for small drops a non-monotonic time dependence of the bridge expansion speed is a feature that could be looked for in further experimental studies. Finally, the results of both models are compared to recently available experimental data on the evolution of the liquid bridge connecting coalescing drops, and the interface formation model is seen to give a better agreement with the data.
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Plumari, Salvatore, Vincenzo Minissale, Santosh K. Das, Francesco Scardina, and Vincenzo Greco. "Strange and heavy hadrons production from coalescence plus fragmentation in AA collisions at RHIC and LHC." EPJ Web of Conferences 171 (2018): 13005. http://dx.doi.org/10.1051/epjconf/201817113005.
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In a coalescence plus fragmentation approach we study the pT spectra of charmed hadrons D0, Ds up to about 10 GeV and the Λ+c /D0 ratio from RHIC to LHC energies. In this study we have included the contribution from decays of heavy hadron resonances and also that due to fragmentation of heavy quarks that are left in the system after coalescence. The pT dependence of the heavy baryon/meson ratios is found to be sensitive to the heavy quark mass. In particular we found that the Λc/D0 is much flatter than the one for light baryon/meson ratio like p/π and Λ/K.
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Lemańczyk, Mariusz, Pierre Liardet, and Jean-Paul Thouvenot. "Coalescence of circle extensions of measure-preserving transformations." Ergodic Theory and Dynamical Systems 12, no. 4 (December 1992): 769–89. http://dx.doi.org/10.1017/s0143385700007094.
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AbstractWe prove that for each ergodic automorphism T:(X, ℬ, μ)→(X, ℬ, μ) for which we can find an element S∈C(T) such that the corresponding Z2-action (S, T) on (X, ℬ, μ) is free, there exists a circle valued cocycle φ such that the group extension Tφ is ergodic but is not coalescent. In particular, the existence of such a cocycle is proved for all ergodic rigid automorphisms. As a corollary, in the class of ergodic transformations of [0,1) × [0,1) given byfor each irrational α we find φ such that Tφ is not coalescent. In some special cases the group law of the centralizer is given.
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Farzanah, Khatera H. H., Mira O. M. Hassan, Rauda A. S. Al Muhairi, Claus Rebholz, Ibrahim E. Gunduz, and Charalabos C. Doumanidis. "Mechanics Science-Enabled Nanoheater Multi-Layer Materials Manufactured by Ball Milling." MRS Advances 2, no. 16 (2017): 897–904. http://dx.doi.org/10.1557/adv.2017.71.
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ABSTRACTThis article reports investigation of the effects of high-rate stochastic micro-mechanics on the produced particulate size distribution during ball milling of reactive bimetallic foils (nanoheaters), by experimental and computational modeling. In particular, Ni-Al foils are ball-milled at various load charges, revolution rates and process durations, and the resulting particulate geometries are characterized by micrograph statistical analysis. Numerical simulation of the evolving particulate structure is based on coalescence and fragmentation of flexible monometallic ellipsoidal primitives, impacted by milling balls and vial walls with kinetic theory-based kinematics. Particulates are constrained by discrete compliant and continuum media and undergo conceptual ideal elastic transformations modeled by strain energy methods, and recast into inelastic frictional and plasticity-driven welding and fracture events. Finally the theoretical model predictions of particulate size distribution are validated against laboratory microscopy observations.
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Walker, Christoph. "Asymptotic behaviour of liquid–liquid dispersions." Proceedings of the Royal Society of Edinburgh: Section A Mathematics 134, no. 4 (August 2004): 753–72. http://dx.doi.org/10.1017/s0308210500003462.
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Based on earlier results on existence, we study the asymptotic behaviour of solutions to the coalescence-breakage equations, including the volume-scattering phenomenon and high-energy collisions. The solutions are shown to converge towards one particular equilibrium, provided the kernels satisfy a kind of reversibility. We also derive stability of these equilibria in a suitable topology.
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BARANGER, C. "MODELLING OF OSCILLATIONS, BREAKUP AND COLLISIONS FOR DROPLETS: THE ESTABLISHMENT OF KERNELS FOR THE T.A.B. MODEL." Mathematical Models and Methods in Applied Sciences 14, no. 05 (May 2004): 775–94. http://dx.doi.org/10.1142/s0218202504003441.
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In this work, we consider a spray consisting of droplets surrounded by a gas. The droplets are described by a kinetic equation and the gas verifies an equation of fluid dynamics such as Navier–Stokes. We write down the kernels corresponding to complex phenomena such as oscillations, breakup and collisions/coalescences. We use for that the T.A.B. model of oscillations introduced in particular in the KIVA code of combustion of Los Alamos, and the collision model introduced by Villedieu. We briefly explain the numerical method for solving such equations, and present results.
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Ruffino, Francesco, Maria Censabella, Giovanni Piccitto, and Maria Grimaldi. "Morphology Evolution of Nanoscale-Thick Au/Pd Bimetallic Films on Silicon Carbide Substrate." Micromachines 11, no. 4 (April 14, 2020): 410. http://dx.doi.org/10.3390/mi11040410.
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Bimetallic Au/Pd nanoscale-thick films were sputter-deposited at room temperature on a silicon carbide (SiC) surface, and the surface-morphology evolution of the films versus thickness was studied with scanning electron microscopy. This study allowed to elucidate the Au/Pd growth mechanism by identifying characteristic growth regimes, and to quantify the characteristic parameters of the growth process. In particular, we observed that the Au/Pd film initially grew as three-dimensional clusters; then, increasing Au/Pd film thickness, film morphology evolved from isolated clusters to partially coalesced wormlike structures, followed by percolation morphology, and, finally, into a continuous rough film. The application of the interrupted coalescence model allowed us to evaluate a critical mean cluster diameter for partial coalescence, and the application of Vincent’s model allowed us to quantify the critical Au/Pd coverage for percolation transition.
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ŁUKASZEWICZ, BEATA. "Reduction in syllable onsets in the acquisition of Polish: deletion, coalescence, metathesis and gemination." Journal of Child Language 34, no. 1 (January 25, 2007): 53–82. http://dx.doi.org/10.1017/s0305000906007707.
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This paper focuses on four strategies of onset reduction employed by a single child (4;0–4;4) acquiring Polish: deletion, coalescence, metathesis, and gemination. Deletion and coalescence occur in word-initial onsets while metathesis and gemination are restricted to word-medial position. The data, which constitute an intriguing ‘conspiracy’ case (Kisseberth, 1970), are analysed within OPTIMALITY THEORY (henceforth, OT; Prince & Smolensky, 1993/2004; McCarthy & Prince, 1995) in which all surface-true ‘processes’ are motivated through the interaction of ranked and violable constraints. The OT account makes it possible to envisage the four strategies as different surface responses to the undominated *COMPLEXOnset which militates against onset clusters. The choice of a particular strategy as well as its restriction to a particular word position is not random but follows from the interplay between *COMPLEXOnset, sonority-based syllable structure constraints (Margin Hierarchy, CONTACT LAW), context-sensitive markedness constraints (CODA CONDITION, *Nasal–Fricative) and faithfulness constraints. The present study confirms previous sonority-based findings, supplies further evidence for universal sonority mechanisms from word-medial clusters, and points to the coexistence of child-specific and abstract adult-based phonological strategies in the child’s system.
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Chao, Xiuli, Michael Pinedo, and Dequan Shaw. "Networks of queues with batch services and customer coalescence." Journal of Applied Probability 33, no. 3 (September 1996): 858–69. http://dx.doi.org/10.2307/3215364.
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Consider a queueing network with batch services at each node. The service time of a batch is exponential and the batch size at each node is arbitrarily distributed. At a service completion the entire batch coalesces into a single unit, and it either leaves the system or goes to another node according to given routing probabilities. When the batch sizes are identical to one, the network reduces to a classical Jackson network. Our main result is that this network possesses a product form solution with a special type of traffic equations which depend on the batch size distribution at each node. The product form solution satisfies a particular type of partial balance equation. The result is further generalized to the non-ergodic case. For this case the bottleneck nodes and the maximal subnetwork that achieves steady state are determined. The existence of a unique solution is shown and stability conditions are established. Our results can be used, for example, in the analysis of production systems with assembly and subassembly processes.
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Chao, Xiuli, Michael Pinedo, and Dequan Shaw. "Networks of queues with batch services and customer coalescence." Journal of Applied Probability 33, no. 03 (September 1996): 858–69. http://dx.doi.org/10.1017/s0021900200100269.
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Consider a queueing network with batch services at each node. The service time of a batch is exponential and the batch size at each node is arbitrarily distributed. At a service completion the entire batch coalesces into a single unit, and it either leaves the system or goes to another node according to given routing probabilities. When the batch sizes are identical to one, the network reduces to a classical Jackson network. Our main result is that this network possesses a product form solution with a special type of traffic equations which depend on the batch size distribution at each node. The product form solution satisfies a particular type of partial balance equation. The result is further generalized to the non-ergodic case. For this case the bottleneck nodes and the maximal subnetwork that achieves steady state are determined. The existence of a unique solution is shown and stability conditions are established. Our results can be used, for example, in the analysis of production systems with assembly and subassembly processes.
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Stadler, Tanja, Timothy G. Vaughan, Alex Gavryushkin, Stephane Guindon, Denise Kühnert, Gabriel E. Leventhal, and Alexei J. Drummond. "How well can the exponential-growth coalescent approximate constant-rate birth–death population dynamics?" Proceedings of the Royal Society B: Biological Sciences 282, no. 1806 (May 7, 2015): 20150420. http://dx.doi.org/10.1098/rspb.2015.0420.
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One of the central objectives in the field of phylodynamics is the quantification of population dynamic processes using genetic sequence data or in some cases phenotypic data. Phylodynamics has been successfully applied to many different processes, such as the spread of infectious diseases, within-host evolution of a pathogen, macroevolution and even language evolution. Phylodynamic analysis requires a probability distribution on phylogenetic trees spanned by the genetic data. Because such a probability distribution is not available for many common stochastic population dynamic processes, coalescent-based approximations assuming deterministic population size changes are widely employed. Key to many population dynamic models, in particular epidemiological models, is a period of exponential population growth during the initial phase. Here, we show that the coalescent does not well approximate stochastic exponential population growth, which is typically modelled by a birth–death process. We demonstrate that introducing demographic stochasticity into the population size function of the coalescent improves the approximation for values of R 0 close to 1, but substantial differences remain for large R 0 . In addition, the computational advantage of using an approximation over exact models vanishes when introducing such demographic stochasticity. These results highlight that we need to increase efforts to develop phylodynamic tools that correctly account for the stochasticity of population dynamic models for inference.
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Xue, Yan, Lian-Ping Wang, and Wojciech W. Grabowski. "Growth of Cloud Droplets by Turbulent Collision–Coalescence." Journal of the Atmospheric Sciences 65, no. 2 (February 1, 2008): 331–56. http://dx.doi.org/10.1175/2007jas2406.1.
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Abstract An open question in cloud physics is how rain forms in warm cumulus as rapidly as it is sometimes observed. In particular, the growth of cloud droplets across the size gap from 10 to 50 μm in radius has not been fully explained. In this paper, the authors investigate the growth of cloud droplets by collision–coalescence, taking into account both the gravitational mechanism and several enhancements of the collision–coalescence rate due to air turbulence. The kinetic collection equation (KCE) is solved with an accurate bin integral method and a newly developed parameterization of turbulent collection kernel derived from direct numerical simulation of droplet-laden turbulent flows. Three other formulations of the turbulent collection kernel are also considered so as to assess the dependence of the rain initiation time on the nature of the collection kernel. The results are compared to the base case using the Hall hydrodynamical–gravitational collection kernel. Under liquid water content and eddy dissipation rate values typical of small cumulus clouds, it is found that air turbulence has a significant impact on the collection kernel and thus on the time required to form drizzle drops. With the most realistic turbulent kernel, the air turbulence can shorten the time for the formation of drizzle drops by about 40% relative to the base case, applying measures based on either the radar reflectivity or the mass-weighted drop size. A methodology is also developed to unambiguously identify the three phases of droplet growth, namely, the autoconversion phase, the accretion phase, and the larger hydrometeor self-collection phase. The important observation is that even a moderate enhancement of collection kernel by turbulence can have a significant impact on the autoconversion phase of the growth.
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ANDRISHKO, Oleh. "COALESCENCES IN THE BOOK OF IVAN IOV “PERIODIC SYSTEM OF WORDS”." Culture of the Word, no. 92 (2020): 123–33. http://dx.doi.org/10.37919/0201-419x-2020.92.10.
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The article deals with the features of word-coalescences in the book of Ivan Iov «Periodic system of words», which is considered to be the most prominent in the author’s work. Ivan Iov belonged to the leading Ukrainian avant-garde poets to the 20th-21th centuries, leaving a significant trace both in syllabic tonic poetry and in experimental poetry (palindromes, graphic poems, acrostic, brachicolons, logogriphs, collage etc.). Ivan Iov was born in 1948 in the village of Kamianka, in the Apostolove District of the Dnipro region in a large family. He graduated from Kamianets-Podilskyi National Ivan Ohiienko University and then worked as a teacher and journalist. In 1997, he published his most famous and significant collection, «The Periodic system of words», where he continued the traditions of Ivan Velychkovskyi and which became the subject of our research. Particular attention deserves to occasionalisms by the author. In the research book you can identify several groups of coalescences-words, created lexico-syntactical method, on the basis of sued and subordinate phrases, residual phrases (most often prepositions). Also a feature of the creation of neologisms in Ivan Iov is the use of the names and surnames of famous people – friends of the poet, for example, Valerii Basyrov – the editor of this book; Hryhorii Huseinov – writer, laureate of the Taras Shevchenko National Prize; Mykola Zhulynskyi – Director of the Taras Shevchenko Institute of Literature of NAS of Ukraine. In the «Periodic system of words», the coalescences-palindromes (both commonly used and occasional) are also widely represented, which is a decisive feature of the creative manner of Ivan Iov compared with other avant-garde poets. The top of word-formation skill can be considered the poem that gave the collection its name; in it Ivan Iov showed the inexhaustible possibilities of word formation, which in combination with the original author’s style gave us a wonderful example of experimental literature.
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Pattemore, Gary A., John F. Rigby, and Geoffrey Playford. "The Mesozoic megafossil genus Linguifolium Arber 1917." Acta Palaeobotanica 55, no. 2 (December 1, 2015): 123–47. http://dx.doi.org/10.1515/acpa-2015-0009.
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Abstract The plant megafossil genus Linguifolium Arber 1917 is chiefly known from the Middle and Upper Triassic of Gondwana. The range of Linguifolium extended beyond Gondwana by the Late Triassic, persisting there through the earliest Jurassic (Hettangian). The parent plants probably grew in a well-watered, canopied environment. Diagnoses of the genus and four of its species - Linguifolium tenison-woodsii (Shirley 1898) Retallack 1980, L. waitakiense Bell in Bell et al. 1956, L. parvum Holmes & Anderson in Holmes et al. 2010, and L. steinmannii (Solms-Laubach 1899) Arber 1917 - are emended with particular reference to venation and leaf morphology; consequently, the stratigraphic ranges of the species have been more precisely defined. Coalescent venation has previously been reported in some species of Linguifolium and is identified in new material described herein. Although the vast majority of specimens assigned to the genus are from the Upper Triassic, none shows coalescent venation. This character is entirely restricted to the Middle Triassic, in particular to two species: L. waitakiense and L. parvum. Linguifolium tenison-woodsii is restricted to the Carnian-lowermost Norian of Australia and South Africa and is recorded here for the first time from the Tarong Basin (upper Carnian), Queensland. Confusion regarding assignment of specimens to this species from the Middle Jurassic of Queensland is resolved.
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Pandey, Puran, Mao Sui, Sundar Kunwar, Ming-Yu Li, Quanzhen Zhang, and Jihoon Lee. "Determination of growth regimes of Pt nanostructures on GaN (0001) based on the control of Pt thickness and annealing time: Morphological evolution of Pt nanostructures from the nanoparticles, nanoclusters to porous network." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 233, no. 5 (June 19, 2017): 913–23. http://dx.doi.org/10.1177/1464420717715878.
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Pt nanostructures are applicable in various applications such as sensors, solar cells, light emitting devices and catalysis and only slight changes in their configuration, density and size can induce significant changes in their properties and thus the functionality in the related applications. In this paper, the systematical evolution of Pt nanostructures such as nanoparticles, nanoclusters and porous network on GaN (0001) is demonstrated by the systematic thermal annealing of Pt thin films based on the combinational effects such as thermal dewetting, Volmer-Weber growth model and coalescence growth. In particular, small dome-shaped self-assembled Pt nanoparticles with relatively smaller deposition amount (<2 nm) and wiggly Pt nanoclusters between 3 and 5 nm are formed based on the Volmer-Weber growth model and the partial coalescence of Pt nanoparticles, respectively. Between 10 and 30 nm, the growth of Pt nanoclusters is observed and eventually with the increased Pt thickness range between 40 and 100 nm, nanoclusters gradually develop into the porous Pt network by connecting neighboring structures owing to the enhanced coalescence growth. Meanwhile, along with the annealing time variation between 0 and 3600 s, the rate of dewetting is increased and as a result, the evolution of densely packed to separated nanoclusters is formed. In addition, the optical properties of corresponding Pt nanostructures demonstrate that the photoluminescence and Raman intensity are reduced along with the evolution of the surface coverage of Pt nanostructures, whereas the average reflectance is significantly enhanced accordingly at the same time.
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HUILLET, THIERRY, and MARTIN MÖHLE. "Asymptotics of Symmetric Compound Poisson Population Models." Combinatorics, Probability and Computing 24, no. 1 (September 8, 2014): 216–53. http://dx.doi.org/10.1017/s0963548314000431.
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Compound Poisson population models are particular conditional branching process models. A formula for the transition probabilities of the backward process for general compound Poisson models is verified. Symmetric compound Poisson models are defined in terms of a parameter θ ∈ (0, ∞) and a power series φ with positive radius r of convergence. It is shown that the asymptotic behaviour of symmetric compound Poisson models is mainly determined by the characteristic value θrφ′(r−). If θrφ′(r−)≥1, then the model is in the domain of attraction of the Kingman coalescent. If θrφ′(r−) < 1, then under mild regularity conditions a condensation phenomenon occurs which forces the model to be in the domain of attraction of a discrete-time Dirac coalescent. The proofs are partly based on the analytic saddle point method. They draw heavily from local limit theorems and from results of S. Janson on simply generated trees, conditioned Galton-Watson trees, random allocations and condensation. Several examples of compound Poisson models are provided and analysed.
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Gwak, Bogeun. "Coalescence of Kerr Black Holes—Binary Systems from GW150914 to GW170814." Entropy 21, no. 10 (October 20, 2019): 1017. http://dx.doi.org/10.3390/e21101017.
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We investigate the energy of the gravitational wave from a binary black hole merger by the coalescence of two Kerr black holes with an orbital angular momentum. The coalescence is constructed to be consistent with particle absorption in the limit in which the primary black hole is sufficiently large compared with the secondary black hole. In this limit, we analytically obtain an effective gravitational spin–orbit interaction dependent on the alignments of the angular momenta. Then, binary systems with various parameters including equal masses are numerically analyzed. According to the numerical analysis, the energy of the gravitational wave still depends on the effective interactions, as expected from the analytical form. In particular, we ensure that the final black hole obtains a large portion of its spin angular momentum from the orbital angular momentum of the initial binary black hole. To estimate the angular momentum released by the gravitational wave in the actual binary black hole, we apply our results to observations at the Laser Interferometer Gravitational-Wave Observatory: GW150914, GW151226, GW170104, GW170608 and GW170814.
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Vystavel, T., S. A. Koch, G. Palasantzas, and J. Th M. De Hosson. "In situ Transmission Electron Microscopy Studies on Structural Dynamics of Transition Metal Nanoclusters." Journal of Materials Research 20, no. 7 (July 1, 2005): 1785–91. http://dx.doi.org/10.1557/jmr.2005.0222.
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The structural stability of transition metal nanoclusters has been scrutinized with in situ transmission electron microscopy as a function of temperature. In particular iron, cobalt, niobium, and molybdenum clusters with diameters around 5 nm have been investigated. During exposure to air, a thin oxide shell with a thickness of 2 nm is formed around the iron and cobalt clusters, which is thermally unstable under moderate high vacuum annealing above 200 °C. Interestingly, niobium clusters oxidize only internally at higher temperatures without the formation of an oxide shell. They are unaffected under electron beam irradiation, whereas iron and cobalt undergo severe structural changes. Further, no cluster coalescence of niobium takes place, even during annealing up to 800 °C, whereas iron and cobalt clusters coalesce after decomposition of the oxide, as long as the clusters are in close contact. In contrast to niobium, molybdenum clusters do not oxidize upon annealing; they are stable under electron beam irradiation and coalesce at temperatures higher than 800 °C. In all cases, the coalescence process indicates a strong influence of the local environment of the cluster.
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Zhang, Fan. "Decline of the Current Quadrupole Moment during the Merger Phase of Binary Black Hole Coalescence." Universe 6, no. 1 (December 25, 2019): 3. http://dx.doi.org/10.3390/universe6010003.
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Utilizing the tools of tendex and vortex, we study the highly dynamic plunge and merger phases of several π -symmetric binary black hole coalescences. In particular, we observe a decline of the strength of the current quadrupole moment compared to that of the mass quadrupole moment during the merger phase, contrary to a naive estimate according to the dependence of these moments on the separation between the black holes. We further show that this decline of the current quadrupole moment is achieved through the remnants of the two individual spins becoming nearly aligned or anti-aligned with the total angular momentum. We also speculate on the ability to achieve a consistency between the electric and magnetic parity quasinormal modes.
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Ponga, M., Ignasio Romero, M. Ortiz, and M. P. Ariza. "Finite Temperature Nanovoids Evolution in FCC Metals Using Quasicontinuum Method." Key Engineering Materials 488-489 (September 2011): 387–90. http://dx.doi.org/10.4028/www.scientific.net/kem.488-489.387.
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Tensile failure of metals often occurs through void nucleation, growth and coalescence. This work is concerned with the study of plastic nanovoid cavitation in face-centeredcubic (FCC) crystals at finite temperature. In particular, the Quasicontinuum (QC) method,suitably extended to finite temperatures, is taken as the basis for the analysis. We specificallyfocus on nanovoids in copper single crystals deforming in uniaxial and triaxial tension. Thecomplex structure of dislocations around the nanovoid and the evolution of stress, deformationand temperature of the sample is described in the present work.
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Banagiri, Sharan, Michael W. Coughlin, James Clark, Paul D. Lasky, M. A. Bizouard, Colm Talbot, Eric Thrane, and Vuk Mandic. "Constraining the gravitational-wave afterglow from a binary neutron star coalescence." Monthly Notices of the Royal Astronomical Society 492, no. 4 (January 22, 2020): 4945–51. http://dx.doi.org/10.1093/mnras/staa181.
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ABSTRACT Binary neutron star mergers are rich laboratories for physics, accessible with ground-based interferometric gravitational-wave detectors such as the Advanced LIGO and Advanced Virgo. If a neutron star remnant survives the merger, it can emit gravitational waves that might be detectable with the current or next generation detectors. The physics of the long-lived post-merger phase is not well understood and makes modelling difficult. In particular the phase of the gravitational-wave signal is not well modelled. In this paper, we explore methods for using long duration post-merger gravitational-wave signals to constrain the parameters and the properties of the remnant. We develop a phase-agnostic likelihood model that uses only the spectral content for parameter estimation and demonstrate the calculation of a Bayesian upper limit in the absence of a signal. With the millisecond magnetar model, we show that for an event like GW170817, the ellipticity of a long-lived remnant can be constrained to less than about 0.5 in the parameter space used.
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Spellman, Garth M., and John Klicka. "Testing hypotheses of Pleistocene population history using coalescent simulations: phylogeography of the pygmy nuthatch ( Sitta pygmaea )." Proceedings of the Royal Society B: Biological Sciences 273, no. 1605 (September 26, 2006): 3057–63. http://dx.doi.org/10.1098/rspb.2006.3682.
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In this paper, we use mitochondrial NADH dehydrogenase subunit 2 sequences to test Pleistocene refugial hypotheses for the pygmy nuthatch ( Sitta pygmaea ). Pygmy nuthatches are a common resident of long-needle pine forests in western North America and demonstrate a particular affinity with ponderosa pine ( Pinus ponderosa ). Palaeoecological and genetic data indicate that ponderosa pine was isolated in two Pleistocene refugia corresponding to areas in the southern Sierra Nevada in the west and southern Arizona and New Mexico in the east. We use coalescent simulations to test the hypothesis that pygmy nuthatches tracked the Pleistocene history of their preferred habitat and persisted in two refugia during the periods of glacial maxima. Coalescent simulation of population history does not support the hypothesis of two Pleistocene refugia for the pygmy nuthatch. Instead, our data are consistent with a single refuge model. Nucleotide diversity is greatest in the western populations of southern and coastal California. We suggest that the pygmy nuthatch expanded from a far western glacial refuge into its current distribution since the most recent glacial maximum.
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Tian, Ye, Ning Ren, Zhihua Zhao, Fengshun Wu, and Suresh Sitaraman. "Ag3Sn Compounds Coarsening Behaviors in Micro-Joints." Materials 11, no. 12 (December 10, 2018): 2509. http://dx.doi.org/10.3390/ma11122509.
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As solder joints are being scaled down, intermetallic compounds (IMCs) are playing an increasingly critical role in the reliability of solder joints, and thereby an in-depth understanding of IMCs microstructure evolutions in micro-joints is of great significance. This study focused on coarsening behaviors of Ag3Sn compounds in Sn-3.0Ag-0.5Cu (SAC305) micro-joints of flip chip assemblies using thermal shock (TS) tests. The results showed that the Ag3Sn compounds grew and rapidly coarsened into larger ones as TS cycles increased. Compared with such coarsening behaviors during thermal aging, TS exhibited a significantly accelerating influence. This predominant contribution is quantitatively determined to be induced by strain-enhanced aging. Moreover, based on observations for Ag3Sn microstructure evolutions during TS cycling, one particular finding showed that there are two types of coarsening modes (i.e., Ostwald ripening and Necking coalescence) co-existing in the Ag3Sn coarsening process. The corresponding evolutions mechanism was elucidated in a combination of simulative analysis and experimental validation. Furthermore, a kinetic model of the Ag3Sn coarsening was established incorporating static aging and strain-enhanced aging constant, the growth exponent (n) was calculated to be 1.70, and the predominant coarsening mode was confirmed to be the necking coalescence.
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Ramnarayanan, Sai P., and Pamela L. Tuma. "MAL, but not MAL2, expression promotes the formation of cholesterol-dependent membrane domains that recruit apical proteins." Biochemical Journal 439, no. 3 (October 13, 2011): 497–504. http://dx.doi.org/10.1042/bj20110803.
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Our recent studies have been aimed at understanding the mechanisms regulating apical protein sorting in polarized epithelial cells. In particular, we have been investigating how lipid rafts serve to sort apical proteins in the biosynthetic pathway. The recent findings that lipid domains are too small or transient to host apically destined cargo have led to newer versions of the hypothesis that invoke proteins required for lipid domain coalescence and stabilization. MAL (myelin and lymphocyte protein) and its highly conserved family member, MAL2, have emerged as possible regulators of this process in the direct and indirect apical trafficking pathways respectively. To test this possibility, we took a biochemical approach. We determined that MAL, but not MAL2, self-associates, forms higher-order cholesterol-dependent complexes with apical proteins and promotes the formation of detergent-resistant membranes that recruit apical proteins. Such biochemical properties are consistent with a role for MAL in raft coalescence and stabilization. These findings also support a model whereby hydrophobic mismatch between the long membrane-spanning helices of MAL and the short-acyl-chain phospholipids in the Golgi drive formation of lipid domains rich in raft components that are characterized by a thicker hydrophobic core to alleviate mismatch.
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Pannell, John R., and Brian Charlesworth. "Effects of metapopulation processes on measures of genetic diversity." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, no. 1404 (December 29, 2000): 1851–64. http://dx.doi.org/10.1098/rstb.2000.0740.
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Many species persist as a metapopulation under a balance between the local extinction of subpopulations or demes and their recolonization through dispersal from occupied patches. Here we review the growing body of literature dealing with the genetic consequences of such population turnover. We focus our attention principally on theoretical studies of a classical metapopulation with a ‘finite–island’ model of population structure, rather than on ‘continent–island’ models or ‘source–sink’ models. In particular, we concern ourselves with the subset of geographically subdivided population models in which it is assumed that all demes are liable to extinction from time to time and that all demes receive immigrants. Early studies of the genetic effects of population turnover focused on population differentiation, such as measured by F ST . A key advantage of F ST over absolute measures of diversity is its relative independence of the mutation process, so that different genes in the same species may be compared. Another advantage is that F ST will usually equilibrate more quickly following perturbations than will absolute levels of diversity. However, because F ST is a ratio of between–population differentiation to total diversity, the genetic effects of metapopulation processes may be difficult to interpret in terms of F ST on its own, so that the analysis of absolute measures of diversity in addition is likely to be informative. While population turnover may either increase or decrease F ST , depending on the mode of colonization, recurrent extinction and recolonization is expected always to reduce levels of both within–population and specieswide diversity (π S and π T , respectively). One corollary of this is that π S cannot be used as an unbiased estimate of the scaled mutation rate, θ, as it can, with some assumptions about the migration process, in species whose demes do not fluctuate in size. The reduction of π in response to population turnover reflects shortened mean coalescent times, although the distribution of coalescence times under extinction–colonization equilibrium is not yet known. Finally, we review current understanding of the effect of metapopulation dynamics on the effective population size.
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Arrowsmith, Peter, and Steven K. Hughes. "Entrainment and Transport of Laser Ablated Plumes for Subsequent Elemental Analysis." Applied Spectroscopy 42, no. 7 (September 1988): 1231–39. http://dx.doi.org/10.1366/0003702884430100.
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Several cell designs have been systematically evaluated for gas flow entrainment and transport of laser ablated material to a secondary excitation source for elemental analysis. The best cell is not limited to samples of particular size or shape and is insensitive to sample surface irregularity. An annular gas sheath around the cell results in a transient response sufficiently fast to permit depth and lateral sampling of single samples or rapid throughput of different samples but slow enough to give a steady signal with laser repetition rates ≥10 Hz. Entrainment and transport of ablated particulates have been investigated experimentally and by model calculation for a test material (Mo metal). The equations for predicting diffusive and gravitational loss of particles in a horizontal tube are presented and discussed. The major loss mechanism appears to be gravitational deposition of relatively large particles formed during ablation and possibly by coalescence within the transfer tube. Entrainment of ablated Mo by the cell and mass transport from the cell to the secondary source were determined to be ∼90% and ∼40% efficient, respectively. Shot-to-shot fluctuation in particle size may cause corresponding variation in transport efficiency when the upper end of the ablated particle size distribution exceeds the size limit for particle transport.
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Le Borgne, T., M. Dentz, and E. Villermaux. "The lamellar description of mixing in porous media." Journal of Fluid Mechanics 770 (April 10, 2015): 458–98. http://dx.doi.org/10.1017/jfm.2015.117.
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We develop a general framework for modelling mixing in porous media flows, in which the scalar mixture is represented as an ensemble of lamellae evolving through stretching, diffusion and coalescence. Detailed numerical simulations in Darcy scale heterogeneous permeability fields are used to analyse the lamella deformation process, which controls the local concentration gradients and thus the evolution of the concentration mixture through stretching enhanced diffusion. The corresponding Lagrangian deformation process is shown to be well modelled by a Langevin equation with multiplicative noise, which can be coupled with diffusion to predict the temporal evolution of the concentration probability density function (PDF). At late times, lamella interaction is enforced by confinement of the mixture within the dispersion area. This process is shown to be well represented by a random aggregation model, which quantifies the frequency of lamella coalescence and allows us to predict the temporal evolution of the concentration PDF in this regime. The proposed theoretical framework provides an accurate prediction of the concentration PDFs at all investigated times, heterogeneity levels and Péclet numbers. In particular, it relates the temporal behaviour of mixing, as quantified by concentration moments, scalar dissipation rate or spatial increments of concentration, to the degree of structural heterogeneity.
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He, Jingshu, Jiafeng Zheng, Zhengmao Zeng, Yuzhang Che, Min Zheng, and Jianjie Li. "A Comparative Study on the Vertical Structures and Microphysical Properties of Stratiform Precipitation over South China and the Tibetan Plateau." Remote Sensing 13, no. 15 (July 23, 2021): 2897. http://dx.doi.org/10.3390/rs13152897.
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Under different water vapor and dynamic conditions, and the influence of topographies and atmospheric environments, stratiform precipitation over South China and the Tibetan Plateau can produce different features. In this study, stratiform precipitation vertical characteristics, bright-band (BB) microstructures, and the vertical variations of the raindrop size distribution (DSD) over a low-altitude site (Longmen site, 86 m) in South China and a high-altitude site (Nagqu site, 4507 m) on the Tibetan Plateau were comprehensively investigated and compared using measurements from a Ka-band millimeter-wave cloud radar (CR), a K-band microrain radar (MRR), and a Parsivel disdrometer (disdrometer). A reliable BB identification scheme was proposed on the basis of CR variables and used for stratiform precipitation sample selection and further statistics and analysis. Results indicate that melting layers over the Longmen are much higher and slightly thicker than those over the Nagqu due to significant differences in atmospheric conditions. For stratiform precipitation, vertical air motions and radar variables over the two sites show different variation trends from cloud top to the ground. Vertical air motions are very weak in the stratiform precipitation over the Longmen, whereas updrafts are more active over the Nagqu. Above the melting layer, radar equivalent reflectivity factor Ze (mean Doppler velocity VM) gradually increases (decreases) as height decreases over the two sites, but the aggregation rate for ice particles over the Longmen can be faster. In the melting layer, Ze (VM) at the BB bottom/center over the Longmen is larger (smaller) than those over the Nagqu for the reason that melted raindrops in the melting layers over the Longmen are larger than those over the Nagqu. Below the melting layer, profiles of radar variables and DSDs show completely different behaviors over the two sites, which reflects that the collision, coalescence, evaporation, and breakup processes of raindrops are different between the two sites. Over the Longmen, collision and coalescence dominate the precipitation properties; in particular, from 2.0–2.8 km, the breakup process competes with collision–coalescence processes but later is overpowered. In contrast, due to the lower BB heights over the Nagqu, collision and coalescence dominate raindrop properties. Comparisons of raindrop spectra suggest that the concentration of small (medium-to-large) raindrops over the Nagqu is much higher (slightly lower) than that over the Longmen. Therefore, the mass-weighted mean diameter Dm (the generalized intercept parameter Nw) over the Nagqu is smaller (larger) than that over the Longmen.
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Dotti, M., A. Sesana, and R. Decarli. "Massive Black Hole Binaries: Dynamical Evolution and Observational Signatures." Advances in Astronomy 2012 (2012): 1–14. http://dx.doi.org/10.1155/2012/940568.
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The study of the dynamical evolution of massive black hole pairs in mergers is crucial in the context of a hierarchical galaxy formation scenario. The timescales for the formation and the coalescence of black hole binaries are still poorly constrained, resulting in large uncertainties in the expected rate of massive black hole binaries detectable in the electromagnetic and gravitational wave spectra. Here, we review the current theoretical understanding of the black hole pairing in galaxy mergers, with a particular attention to recent developments and open issues. We conclude with a review of the expected observational signatures of massive binaries and of the candidates discussed in literature to date.
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Rozentsvaig, Alexander, and Cheslav Strashinskii. "Modeling of Complex Processes in Turbulent Flow of Unstable Emulsions of Immiscible Liquids." Periodica Polytechnica Chemical Engineering 61, no. 3 (February 21, 2017): 216. http://dx.doi.org/10.3311/ppch.9504.
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Turbulent flows of emulsions are associated with the processes of breakage, coalescence and sedimentation of droplets of dispersed liquid. Mechanisms of these physical phenomena that form the equilibrium composition of the droplets of dispersed phase are predetermined by the structure of turbulence. Spectrum of distribution of the dispersed droplets according to the size determines in turn the nature of the interaction with the continuous medium. Therefore, a hydrodynamic model for unstable emulsion (CFD) is completed by discrete population balance model (DPB). It reflects the state of the dispersed phase of the emulsion required to construct an adequate model for CFD. A joint application requires the coordination of the composition and structure of these models for formalizing of the complex interrelationships of physical phenomena in the continuous medium and the dispersed phase of the emulsion. The key advantages of such specification of the overall structure of the partial models of the CFD consist in that model includes only the mechanisms of breakup, coalescence and sedimentation of the droplets of the dispersed phase, which are really work in the given conditions. Using of a priori theoretical information in the form of mechanisms of basic physical phenomena (MBPP) is proposed, which is necessary for obtaining the desired particular solutions of applied problems on the basis of common CFD and DPB models.
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Barbier, E., and Nik Petrinic. "Multiple Crack Growth and Coalescence in Meshfree Methods with Adistance Function-Based Enriched Kernel." Key Engineering Materials 560 (July 2013): 37–60. http://dx.doi.org/10.4028/www.scientific.net/kem.560.37.
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Distance fields are functions defining the minimum distance between any generic point inspace and the boundaries of an object. This paper shows some important properties of these fields andtheir derivatives. In fact, for polygonal lines, the derivatives of distance fields are discontinuous overthe finite length of the segment, but continuous all around the end-points. An immediate consequenceis their application as intrinsic enrichment of weight functions in meshless methods, for the treatmentof multiple arbitrary cracks. By introducing such explicitly known function for the distance fields,discontinuities can be easily incorporated in the kernel in a simple, multiplicative manner. The result-ing method allows a more straightforward implementation and simulation of the presence of multiplecracks in a meshless framework without using any of the existing algorithms such as visibility, trans-parency and diffraction. Furthermore, one of the main advantages of this approach is the automaticcoalescence of multiple interacting cracks, i.e. no particular enrichment functions are necessary at thejunction points.