30,859 research outputs found
Generalized enthalpy model of a high pressure shift freezing process
High-pressure freezing processes are a novel emerging technology in food processing, offering significant improvements to the quality of frozen foods. To be able to simulate plateau times and thermal history under different conditions, in this work we present a generalized enthalpy model of the high-pressure shift freezing process. The model includes the effects of pressure on conservation of enthalpy and incorporates the freezing point depression of non-dilute food samples. In addition the significant heat transfer effects of convection in the pressurizing medium are accounted for by solving the two-dimensional Navier-Stokes equations. We run the model for several numerical tests where the food sample is agar gel, and find good agreement with experimental data from the literature
Discrete Dynamical Systems: A Brief Survey
Dynamical system is a mathematical formalization for any fixed rule that is described in time dependent fashion. The time can be measured by either of the number systems - integers, real numbers, complex numbers. A discrete dynamical system is a dynamical system whose state evolves over a state space in discrete time steps according to a fixed rule. This brief survey paper is concerned with the part of the work done by José Sousa Ramos [2] and some of his research students. We present the general theory of discrete dynamical systems and present results from applications to geometry, graph theory and synchronization
Brittle fracture of polymer transient networks
We study the fracture of reversible double transient networks, constituted of
water suspensions of entangled surfactant wormlike micelles reversibly linked
by various amounts of telechelic polymers. We provide a state diagram that
delineates the regime of fracture without necking of the filament from the
regime where no fracture or break-up has been observed. We show that filaments
fracture when stretched at a rate larger than the inverse of the slowest
relaxation time of the networks. We quantitatively demonstrate that dissipation
processes are not relevant in our experimental conditions and that, depending
on the density of nodes in the networks, fracture occurs in the linear
viscoelastic regime or in a non-linear regime. In addition, analysis of the
crack opening profiles indicates deviations from a parabolic shape close to the
crack tip for weakly connected networks. We demonstrate a direct correlation
between the amplitude of the deviation from the parabolic shape and the amount
of non linear viscoelasticity
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