1,009 research outputs found
Kinetics of Particles Adsorption Processes Driven by Diffusion
The kinetics of the deposition of colloidal particles onto a solid surface is
analytically studied. We take into account both the diffusion of particles from
the bulk as well as the geometrical aspects of the layer of adsorbed particles.
We derive the first kinetic equation for the coverage of the surface (a
generalized Langmuir equation) whose predictions are in agreement with recent
simulation results where diffusion of particles from the bulk is explicitly
considered.Comment: 4 page
A computational framework for polyconvex large strain elasticity for geometrically exact beam theory
In this paper, a new computational framework is presented for the analysis of nonlinear beam finite elements subjected to large strains. Specifically, the methodology recently introduced in Bonet et al. (Comput Methods Appl Mech Eng 283:1061–1094, 2015) in the context of three dimensional polyconvex elasticity is extended to the geometrically exact beam model of Simo (Comput Methods Appl Mech Eng 49:55–70, 1985), the starting point of so many other finite element beam type formulations. This new variational framework can be viewed as a continuum degenerate formulation which, moreover, is enhanced by three key novelties. First, in order to facilitate the implementation of the sophisticated polyconvex constitutive laws particularly associated with beams undergoing large strains, a novel tensor cross product algebra by Bonet et al. (Comput Methods Appl Mech Eng 283:1061–1094, 2015) is adopted, leading to an elegant and physically meaningful representation of an otherwise complex computational framework. Second, the paper shows how the novel algebra facilitates the re-expression of any invariant of the deformation gradient, its cofactor and its determinant in terms of the classical beam strain measures. The latter being very useful whenever a classical beam implementation is preferred. This is particularised for the case of a Mooney–Rivlin model although the technique can be straightforwardly generalised to other more complex isotropic and anisotropic polyconvex models. Third, the connection between the two most accepted restrictions for the definition of constitutive models in three dimensional elasticity and beams is shown, bridging the gap between the continuum and its degenerate beam description. This is carried out via a novel insightful representation of the tangent operator
Dissipative Particle Dynamics with Energy Conservation
The stochastic differential equations for a model of dissipative particle
dynamics with both total energy and total momentum conservation in the
particle-particle interactions are presented. The corresponding Fokker-Planck
equation for the evolution of the probability distribution for the system is
deduced together with the corresponding fluctuation-dissipation theorems
ensuring that the ab initio chosen equilibrium probability distribution for the
relevant variables is a stationary solution. When energy conservation is
included, the system can sustain temperature gradients and heat flow can be
modeled.Comment: 7 pages, submitted to Europhys. Let
Dynamics of the Volterra-type integral and differentiation operators on generalized Fock spaces
[EN] Various dynamical properties of the differentiation and Volterra-type integral operators on generalized Fock spaces are studied. We show that the differentiation operator is always supercyclic on these spaces. We further characterize when it is hypercyclic, power bounded and uniformly mean ergodic. We prove that the operator satisfies the Ritt's resolvent condition if and only if it is power bounded and uniformly mean ergodic. Some similar results are obtained for the Volterra-type and Hardy integral operators.J. Bonet was partially supported by the research projects MTM2016-76647-P and GV Prometeo 2017/102 (Spain). M. Worku is supported by ISP project, Addis Ababa University, Ethiopia.Bonet Solves, JA.; Mengestie, T.; Worku, M. (2019). Dynamics of the Volterra-type integral and differentiation operators on generalized Fock spaces. Results in Mathematics. 74(4):1-15. https://doi.org/10.1007/s00025-019-1123-7S115744Abanin, A.V., Tien, P.T.: Differentiation and integration operators on weighted Banach spaces of holomorphic functions. Math. Nachr. 290(8–9), 1144–1162 (2017)Atzmon, A., Brive, B.: Surjectivity and invariant subspaces of differential operators on weighted Bergman spaces of entire functions, Bergman spaces and related topics in complex analysis, Contemp. Math., vol. 404, Amer. Math. Soc., Providence, RI, pp. 27–39 (2006)Bayart, F., Matheron, E.: Dynamics of Linear Operators, Cambridge Tracts in Math, vol. 179. Cambridge Univ. Press, Cambridge (2009)Bermúdez, T., Bonilla, A., Peris, A.: On hypercyclicity and supercyclicity criteria. Bull. Austral. Math. Soc. 70, 45–54 (2004)Beltrán, M.J.: Dynamics of differentiation and integration operators on weighted space of entire functions. Studia Math. 221, 35–60 (2014)Beltrán, M.J., Bonet, J., Fernández, C.: Classical operators on weighted Banach spaces of entire functions. Proc. Am. Math. Soc. 141, 4293–4303 (2013)Bès, J., Peris, A.: Hereditarily hypercyclic operators. J. Funct. Anal. 167, 94–112 (1999)Bonet, J.: Dynamics of the differentiation operator on weighted spaces of entire functions. Math. Z. 26, 649–657 (2009)Bonet, J.: The spectrum of Volterra operators on weighted Banach spaces of entire functions. Q. J. Math. 66, 799–807 (2015)Bonet, J., Bonilla, A.: Chaos of the differentiation operator on weighted Banach spaces of entire functions. Complex Anal. Oper. Theory 7, 33–42 (2013)Bonet, J., Taskinen, J.: A note about Volterra operators on weighted Banach spaces of entire functions. Math. Nachr. 288, 1216–1225 (2015)Constantin, O., Persson, A.-M.: The spectrum of Volterra-type integration operators on generalized Fock spaces. Bull. Lond. Math. Soc. 47, 958–963 (2015)Constantin, O., Peláez, J.-Á.: Integral operators, embedding theorems and a Littlewood–Paley formula on weighted Fock spaces. J. Geom. Anal. 26, 1109–1154 (2016)De La Rosa, M., Read, C.: A hypercyclic operator whose direct sum is not hypercyclic. J. Oper. Theory 61, 369–380 (2009)Dunford, N.: Spectral theory. I. Convergence to projections. Trans. Am. Math. Soc. 54, 185–217 (1943)Grosse-Erdmann, K.G., Peris Manguillot, A.: Linear Chaos. Springer, New York (2011)Harutyunyan, A., Lusky, W.: On the boundedness of the differentiation operator between weighted spaces of holomorphic functions. Studia Math. 184, 233–247 (2008)Krengel, U.: Ergodic Theorems. Walter de Gruyter, Berlin (1985)Lyubich, Yu.: Spectral localization, power boundedness and invariant subspaces under Ritt’s type condition. Studia Mathematica 143(2), 153–167 (1999)Mengestie, T.: A note on the differential operator on generalized Fock spaces. J. Math. Anal. Appl. 458(2), 937–948 (2018)Mengestie, T.: Spectral properties of Volterra-type integral operators on Fock–Sobolev spaces. J. Kor. Math. Soc. 54(6), 1801–1816 (2017)Mengestie, T.: On the spectrum of volterra-type integral operators on Fock–Sobolev spaces. Complex Anal. Oper. Theory 11(6), 1451–1461 (2017)Mengestie, T., Ueki, S.: Integral, differential and multiplication operators on weighted Fock spaces. Complex Anal. Oper. Theory 13, 935–95 (2019)Mengestie, T., Worku, M.: Isolated and essentially isolated Volterra-type integral operators on generalized Fock spaces. Integr. Transf. Spec. Funct. 30, 41–54 (2019)Nagy, B., Zemanek, J.A.: A resolvent condition implying power boundedness. Studia Math. 134, 143–151 (1999)Nevanlinna, O.: Convergence of iterations for linear equations. Lecture Notes in Mathematics. ETH Zürich, Birkhäuser, Basel (1993)Ritt, R.K.: A condition that . Proc. Am. Math. Soc. 4, 898–899 (1953)Ueki, S.: Characterization for Fock-type space via higher order derivatives and its application. Complex Anal. Oper. Theory 8, 1475–1486 (2014)Yosida, K.: Functional Analysis. Springer, Berlin (1978)Yosida, K., Kakutani, S.: Operator-theoretical treatment of Marko’s process and mean ergodic theorem. Ann. Math. 42(1), 188–228 (1941
Temporal dynamics of soil fungal communities after partial and total clear-cutting in a managed Pinus sylvestris stand
Forest management aimed to maximize timber production might impact soil fungi, especially those symbiotically associated to tree roots. In this study, we analyse the temporal dynamics of soil fungi along five sampling years after tree removal in a managed Pinus sylvestris stand in northern Spain, where timber production is combined with regular mushroom harvesting. Two management methods were tested: total and partial clear-cutting leaving retention trees for seedling regeneration. Undisturbed, uncut plots were also included in the experiment as a control treatment. The whole fungal community (phylotypes and ecological guilds) were analysed by high-throughput Illumina MiSeq sequencing of fungal ITS1 amplicons. We hypothesized that (1) ectomycorrhizal fungal communities will decrease after both clear-cutting treatments with a concurrent increase in the abundance of saprotrophs, (2) the abundance and diversity of the ectomycorrhizal guild will be more preserved in partially clear-cut than in total clear-cut plots, and (3) the overall fungal diversity will decrease in the cut plots leading to major losses of ectomycorrhizal species. Our results show that soil fungal composition changed across the five years after clear-cutting by decreasing ectomycorrhizal fungi and increasing saprotrophs. However, these changes did not significantly affect fungal diversity and there were taxa-specific responses to tree harvest treatments. Boletus edulis, the most abundant ectomycorrhizal species fruiting in the study area and a valuable local non-forest resource, was negatively affected by either clear-cutting treatments. Soil fungal community composition in partially clear-cut areas was not different from that of total clear-cut areas. Our results indicate a strong effect of tree harvest on the relative abundance of ectomycorrhizal fungi along the first years after clear-cutting. However, levels of fungal diversity were comparable to the undisturbed forest, thus suggesting a potential further recovery of ectomycorrhizal fungi through the colonization of the regenerated seedlings.info:eu-repo/semantics/acceptedVersio
Characterization of horizontal flows around solar pores from high-resolution time series of images
Though there is increasing evidence linking the moat flow and the Evershed
flow along the penumbral filaments, there is not a clear consensus regarding
the existence of a moat flow around umbral cores and pores, and the debate is
still open. Solar pores appear to be a suitable scenario to test the
moat-penumbra relation as evidencing the direct interaction between the umbra
and the convective plasma in the surrounding photosphere, without any
intermediate structure in between. The present work studies solar pores based
on high resolution ground-based and satellite observations. Local correlation
tracking techniques have been applied to different-duration time series to
analyze the horizontal flows around several solar pores. Our results establish
that the flows calculated from different solar pore observations are coherent
among each other and show the determinant and overall influence of exploding
events in the granulation around the pores. We do not find any sign of
moat-like flows surrounding solar pores but a clearly defined region of inflows
surrounding them. The connection between moat flows and flows associated to
penumbral filaments is hereby reinforced by this work.Comment: 10 pages, 10 figures, Accepted for publication in Astronomy and
Astrophysics
Denjoy-Carleman differentiable perturbation of polynomials and unbounded operators
Let for be a -mapping with values unbounded
operators with compact resolvents and common domain of definition which are
self-adjoint or normal. Here stands for C^\om (real analytic), a
quasianalytic or non-quasianalytic Denjoy-Carleman class, , or a
H\"older continuity class C^{0,\al}. The parameter domain is either
or or an infinite dimensional convenient vector
space. We prove and review results on -dependence on of the
eigenvalues and eigenvectors of .Comment: 8 page
On a tensor cross product based formulation of large strain solid mechanics
This paper describes in detail the formulation of large strain solid mechanics based on the tensor cross product, originally presented by R. de Boer, Vektor- und Tensorrechnung für Ingenieure, Springer-Verlag, 1982., page 76, and recently re-introduced by Bonet et al. in J. Bonet, A. J. Gil, R. Ortigosa, A computational framework for polyconvex large strain elasticity, Computer Methods in Applied Mechanics and Engineering 283 (2015) 1061 – 1094., and J. Bonet, A. J. Gil, C. H. Lee, M. Aguirre, R. Ortigosa, A first order hyperbolic framework for large strain computational solid dynamics. Part I: Total Lagrangian isothermal elasticity, Computer Methods in Applied Mechanics and Engineering 283 (2015) 689 – 732. The paper shows how the tensor cross product facilitates the algebra associated with the area and volume maps between reference and final configurations. These maps, together with the fibre map, make up the fundamental kinematic variables in polyconvex elasticity. The algebra proposed leads to novel expressions for the tangent elastic operator which neatly separates material from geometrical dependencies. The paper derives new formulas for the spatial and material stress and their corresponding elasticity tensors. These are applied to the simple case of a Mooney-Rivlin material model. The extension to transversely isotropic material models is also considered
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