6,298 research outputs found

    Degradation Modeling of Polyurea Pavement Markings

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    Polyurea is a long life pavement marking material used for assets requiring long periods of uninterrupted accessibility. Knowing the performance characteristics of such markings is critical to asset management planning focused on maximizing marking material life-cycles. This paper presents the performance characteristics of polyurea pavement markings in North Carolina using linear regression models. The models generated by this research provide pavement marking managers with tools to better allocate limited manpower and resources in order to optimize budgets while meeting newly proposed pavement marking retroreflectivity levels of service as proposed by the Federal Highway Administration. This research constructed performance models for polyurea based on the independent variables of time, initial retroreflectivity, and lateral line location. Using the models generated by this research, the pavement marking manager can predict the level of service and remaining life of a given pavement marking. A key finding of this paper is that polyurea pavement marking degradation is significantly impacted by the type of glass bead inserted into the marking

    Updated geometry description for the LHCb Trigger Tracker

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    The XML based detector description for the Trigger Tracker (TT) station has been updated. A more realistic version has been implemented in which volumes for frames, readout cables, balconies, jackets, cooling plates and elements have been added in addition to a detailed description of the detector modules. In this note an overview of the updated description is presented

    Dynamics of Conformal Maps for a Class of Non-Laplacian Growth Phenomena

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    Time-dependent conformal maps are used to model a class of growth phenomena limited by coupled non-Laplacian transport processes, such as nonlinear diffusion, advection, and electro-migration. Both continuous and stochastic dynamics are described by generalizing conformal-mapping techniques for viscous fingering and diffusion-limited aggregation, respectively. A general notion of time in stochastic growth is also introduced. The theory is applied to simulations of advection-diffusion-limited aggregation in a background potential flow. A universal crossover in morphology is observed from diffusion-limited to advection-limited fractal patterns with an associated crossover in the growth rate, controlled by a time-dependent effective Peclet number. Remarkably, the fractal dimension is not affected by advection, in spite of dramatic increases in anisotropy and growth rate, due to the persistence of diffusion limitation at small scales.Comment: 4 pages, 2 figures (six color plates

    The non-local Lotka–Volterra system with a top hat kernel — Part 1:dynamics and steady states with small diffusivity

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    We study the dynamics of the nonlocal Lotka-Volterra system u t = Duuxx + u (1 − ϕ * u − αv), v t = Dvvxx + v (1 − ϕ * v − βu), where a star denotes the spatial convolution and the kernel ϕ is a top hat function. We initially focus on the case of small, equal diffusivities (D = Du = Dv ≪ 1) together with weak interspecies interaction (α, β ≪ 1), and specifically α, β ≪ D. This can then be extended to consider small, but unequal, diffusivities and weak interactions, with now α, β ≪ Du, Dv ≪ 1. Finally we are able to develop the theory for the situation when the diffusivities remain small, but the interactions become stronger.. In each case, we find that u and v independently develop into periodic spatial patterns that consist of separated humps on an O(1) timescale, and that these patterns become quasi-steady on a timescale proportional to the inverse diffusivity. These then interact on a longer timescale proportional to the inverse interaction scale, and approach a meta-stable state. Finally, a stable steady state is achieved on a much longer timescale, which is exponentially large relative to the preceding timescales. We are able to quantify this interaction process by determining a planar dynamical system that governs the temporal evolution of the separation between the two periodic arrays of humps on these sequentially algebraically and then exponentially long timescales. We find that, once the humps no longer overlap, the subsequent dynamics lead to a symmetric disposition of the humps, occurring on the exponentially-long timescale. Numerical solutions of the full evolution problem cannot access the behaviour on this final extreme timescale, but it can be fully explored through the dynamical system

    The evolution problem for the 1D nonlocal Fisher-KPP equation with a top hat kernel. Part 2. The Cauchy problem on a finite interval

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    In the second part of this series of papers, we address the same Cauchy problem that was considered in part 1, namely the nonlocal Fisher-KPP equation in one spatial dimension, ut=Duxx+u(1ϕu), u_t = D u_{xx} + u(1-\phi*u), where ϕu\phi*u is a spatial convolution with the top hat kernel, ϕ(y)H(14y2)\phi(y) \equiv H\left(\frac{1}{4}-y^2\right), except that now the spatial domain is the finite interval [0,a][0,a] rather than the whole real line. Consequently boundary conditions are required at the interval end-points, and we address the situations when these boundary conditions are of either Dirichlet or Neumann type. This model forms a natural extension to the classical Fisher-KPP model, with the introduction of the simplest possible nonlocal effect into the saturation term. Nonlocal reaction-diffusion models arise naturally in a variety of (frequently biological or ecological) contexts, and as such it is of fundamental interest to examine its properties in detail, and to compare and contrast these with the well known properties of the classical Fisher-KPP model
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