2,804 research outputs found

    Inhomogeneous multiscale dynamics in harmonic lattices

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    We use projection operators to address the coarse-grained multiscale problem in harmonic systems. Stochastic equations of motion for the coarse-grained variables with an inhomogeneous level of coarse graining in both time and space are presented. In contrast to previous approaches that typically start with thermodynamic averages the key element of our approach is the use of a projection matrix chosen both for its physical appeal in analogy to mechanical stability theory and for its algebraic properties. We show that thermodynamic equilibrium can be recovered and obtain the fluctuation dissipation theorema posteriori. All system-specific information can be computed from a series of feasible molecular dynamics simulations. We recover previous results in the literature and show how this approach can be used to extend the quasicontinuum approach and comment on implications for dissipative particle dynamics type of methods. Contrary to what is assumed in the latter models the stochastic process of all coarse-grained variables is not necessarily Markovian even though the variables are slow. Our approach is applicable to any system in which the coarse-grained regions are linear. As an example we apply it to the dynamics of a single mesoscopic particle in the infinite one-dimensional harmonic chain.EU growth project SENTIMATS under Contract No. G5RD-CT-200

    Formal derivation of dissipative particle dynamics from first principles

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    We show that the Markovian approximation assumed in current particle-based coarse-grained techniques, like dissipative particle dynamics, is unreliable in situations in which sound plays an important role. As an example we solve analytically and numerically the dynamics of coarse-grained harmonic systems by using first principle methods, showing the presence of long-lived memory kernels. This effect raises questions about the connection of these approaches at their current form to molecular dynamics.The European Union and the EPSR

    Piazza Di Ulivo: ARCE Patio Redesign

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    Piazza de Ulivo was Phase 1 of a multi-quarter initiative to redesign and bring life to a patio space adjacent to Engineering West (Building 21) in Spring of 2020. Located within the central courtyard of Engineering West (Hasslein Garden), the patio space previously contained a senior project pergola that collapsed and has been removed. The remaining elements from this previous structure were an inverted moment frame consisting of five concrete columns and beams joining them. Additionally, a wooden bench with concrete pedestals remained under the shade of the existing olive tree. Desire within the Architectural Engineering (ARCE) department for the patio to not remain unused inspired a redesign to address issues with flooding and olive debris, while increasing usability and comfort within the space

    An XML format for benchmarks in High School Timetabling

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    The High School Timetabling Problem is amongst the most widely used timetabling problems. This problem has varying structures in different high schools even within the same country or educational system. Due to lack of standard benchmarks and data formats this problem has been studied less than other timetabling problems in the literature. In this paper we describe the High School Timetabling Problem in several countries in order to find a common set of constraints and objectives. Our main goal is to provide exchangeable benchmarks for this problem. To achieve this we propose a standard data format suitable for different countries and educational systems, defined by an XML schema. The schema and datasets are available online

    Fluoride Removal From Water Using a 3D Printed Calcium Carbonate Filter

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    Groundwater containing high concentrations of fluoride is the most common source of drinking water in rural areas in parts of east Africa, India, and China. The elevated levels of fluoride cause skeletal and dental fluorosis, which is the weakening and decay of bone structures due to the leeching of calcium from the body as calcium and fluoride bond by the process of adsorption. Over 150 million people are suffering from some form of fluorosis due to the consumption of groundwater. Calcium carbonate has been demonstrated to influence fluoride removal in several forms. To make fluoride removal a cost-effective and user-friendly process, a study has been done to test the efficacy of a 3D printed water filter using E.P Smartfil Filament, composed of 30% calcium carbonate and 70% PLA. The influence of varying conditions concerning the removal of fluoride from water, such as the design of the filter, time spent in contact with the filter, and initial concentration of fluoride have been investigated. The maximum amount of fluoride the filters have removed thus far from any water sample is 0.048 milligrams of fluoride per gram of calcium carbonate in each filter
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