155 research outputs found

    On selection criteria for problems with moving inhomogeneities

    Get PDF
    We study mechanical problems with multiple solutions and introduce a thermodynamic framework to formulate two different selection criteria in terms of macroscopic energy productions and fluxes. Studying simple examples for lattice motion we then compare the implications for both resting and moving inhomogeneities.Comment: revised version contains new introduction, numerical simulations of Riemann problems, and a more detailed discussion of the causality principle; 18 pages, several figure

    On weak convergence of locally periodic functions

    Full text link
    We prove a generalization of the fact that periodic functions converge weakly to the mean value as the oscillation increases. Some convergence questions connected to locally periodic nonlinear boundary value problems are also considered.Comment: arxiv version is already officia

    Homogenized dynamics of stochastic partial differential equations with dynamical boundary conditions

    Full text link
    A microscopic heterogeneous system under random influence is considered. The randomness enters the system at physical boundary of small scale obstacles as well as at the interior of the physical medium. This system is modeled by a stochastic partial differential equation defined on a domain perforated with small holes (obstacles or heterogeneities), together with random dynamical boundary conditions on the boundaries of these small holes. A homogenized macroscopic model for this microscopic heterogeneous stochastic system is derived. This homogenized effective model is a new stochastic partial differential equation defined on a unified domain without small holes, with static boundary condition only. In fact, the random dynamical boundary conditions are homogenized out, but the impact of random forces on the small holes' boundaries is quantified as an extra stochastic term in the homogenized stochastic partial differential equation. Moreover, the validity of the homogenized model is justified by showing that the solutions of the microscopic model converge to those of the effective macroscopic model in probability distribution, as the size of small holes diminishes to zero.Comment: Communications in Mathematical Physics, to appear, 200

    Periodic Homogenization and Material Symmetry in Linear Elasticity

    Get PDF
    Here homogenization theory is used to establish a connection between the symmetries of a periodic elastic structure associated with the microscopic properties of an elastic material and the material symmetries of the effective, macroscopic elasticity tensor. Previous results of this type exist but here more general symmetries on the microscale are considered. Using an explicit example, we show that it is possible for a material to be fully anisotropic on the microscale and yet the symmetry group on the macroscale can contain elements other than plus or minus the identity. Another example demon- strates that not all material symmetries of the macroscopic elastic tensor are generated by symmetries of the periodic elastic structure.Comment: 18 pages, 5 figure

    Межвидовая любовь помимо устава: служебные собаки Ленинградского фронта и их вожатые-саперы

    Get PDF
    A pedigree of a purebred German Shepherd born during the Leningrad blockade was accidentally discovered amidst office waste - and now lies safely stored in a state archive. Our study of the interspecies relationships forged between humans and service dogs in the hardship of blockade and war begins with this document. The story of the several hundred large dogs that survived the Leningrad blockade has long remained untold: the dogs' survival seemed unethical in relation to the memory of people who died of starvation. These pedigreed dogs were collected from the civilian population in the fall of 1941 and survived the first and second blockade winters in a military engineering unit where they and their handlers were trained to detect hidden explosives. Our article opens a new history of these mine-dog units that quickly became famous on the Leningrad front. It is known that the soviet theory of dog training was based on the "scientifically-objective theory of reflexes." We show the practical side of this method: the use of service dogs for military aims rested, we argue, on the personal affectionate bonds formed between dog and handler. While formally remaining a military technology, mine-detection dogs acted as humans' trusted partners and independent historical actors. We show how the centralized Stalinist system, without invading intimate personal realms of interspecies affection, nevertheless planned for and encouraged such affectionate ties in militarized state institutions, where most everything was subordinated to ideological influence: most everything, except the innate species-specific behavior of the dogs themselves

    Development of a method for introducing 1-aminophosphonate fragment in a siloxane matrix

    Get PDF
    © 2016 Taylor & Francis Group, LLC.A versatile synthetic method for the preparation of 1-aminophosphonate derivatives of methylsiloxane oligomers was developed. The introduction of trimethylsilyl amino protecting groups promotes hydrosilylation. The proposed modeling technique allows entering 1-aminophosphonate fragment into the siloxane skeleton of the matrix structure, as well as into the hydrolytically unstable alkoxy-functionalized organosilicon compounds

    Synthesis of methyl(1-aminophosphonate)siloxane oligomers

    Get PDF
    © 2016, Springer Science+Business Media New York.A synthesis of 1-aminophosphonate derivative of methylsiloxane oligomer was developed. A methodology of the introduction of 1-aminophosphonate fragment not only into the stable siloxane structures, but also into hydrolytically unstable alkoxyfunctional organosilicon compounds was suggested
    corecore