GPU Accelerated Discontinuous Galerkin Methods for Shallow Water Equations

We discuss the development, verification, and performance of a GPU accelerated discontinuous Galerkin method for the solutions of two dimensional nonlinear shallow water equations. The shallow water equations are hyperbolic partial differential equations and are widely used in the simulation of tsunami wave propagations. Our algorithms are tailored to take advantage of the single instruction multiple data (SIMD) architecture of graphic processing units. The time integration is accelerated by local time stepping based on a multi-rate Adams-Bashforth scheme. A total variational bounded limiter is adopted for nonlinear stability of the numerical scheme. This limiter is coupled with a mass and momentum conserving positivity preserving limiter for the special treatment of a dry or partially wet element in the triangulation. Accuracy, robustness and performance are demonstrated with the aid of test cases. We compare the performance of the kernels expressed in a portable threading language OCCA, when cross compiled with OpenCL, CUDA, and OpenMP at runtime.Comment: 26 pages, 51 figure

Centrality measures for graphons: Accounting for uncertainty in networks

As relational datasets modeled as graphs keep increasing in size and their data-acquisition is permeated by uncertainty, graph-based analysis techniques can become computationally and conceptually challenging. In particular, node centrality measures rely on the assumption that the graph is perfectly known -- a premise not necessarily fulfilled for large, uncertain networks. Accordingly, centrality measures may fail to faithfully extract the importance of nodes in the presence of uncertainty. To mitigate these problems, we suggest a statistical approach based on graphon theory: we introduce formal definitions of centrality measures for graphons and establish their connections to classical graph centrality measures. A key advantage of this approach is that centrality measures defined at the modeling level of graphons are inherently robust to stochastic variations of specific graph realizations. Using the theory of linear integral operators, we define degree, eigenvector, Katz and PageRank centrality functions for graphons and establish concentration inequalities demonstrating that graphon centrality functions arise naturally as limits of their counterparts defined on sequences of graphs of increasing size. The same concentration inequalities also provide high-probability bounds between the graphon centrality functions and the centrality measures on any sampled graph, thereby establishing a measure of uncertainty of the measured centrality score. The same concentration inequalities also provide high-probability bounds between the graphon centrality functions and the centrality measures on any sampled graph, thereby establishing a measure of uncertainty of the measured centrality score.Comment: Authors ordered alphabetically, all authors contributed equally. 21 pages, 7 figure

An initial evaluation of a biohygrothermal model for the purpose of assessing the risk mould growth in UK dwellings

Moulds are organisms that may be found in both the indoor and outdoor environment. Moulds play an important rolebreaking down and digesting organic material, but, if they are significantly present in the indoor environment they mayaffect the health of the occupants. A relative humidity of 80% at wall surfaces is frequently stated as the decisivecriterion for mould growth and methods used to assess the risk of mould growth are often based on steady stateconditions. However, considering the dynamic conditions typically found in the indoor environment, a betterunderstanding of the conditions required for mould to grow would seem desirable. This paper presents initialexploratory work to evaluate and assess ‘WUFI-bio’ - ‘biohygrothermal’ software that predicts the likelihood of mould growth under transient conditions. Model predictions are compared with large monitored data set from 1,388 UKdwellings before and after insulation and new heating systems are installed (‘Warm Front’), the suitability of thissoftware as a tool to predict mould growth will ultimately be assessed. This paper presents some initial, exploratorywork

Conducta socioespacial frente a un ambiente nuevo de Pseudotropheus tropheops Regan, 1921 (Teleostei, Cichlidae)

Sociospatial behaviour of Pseudotropheus tropheopsReagan, 1921 ina new environment (Teleostei, Cichlidae).- The relationships between agonistic behaviour and spatial variables within a group of six captive inmature Pseudotropheus tropheops is studied. Data on frequency of Eghts and spatial positions are anaiysed during three periods of time within the 24 hours foiiowing modification of the medium. Three phases of social behaviour are established: 1) exploration, performed by the group in schooling; 2) development of Dominance Hierarchy, characterised by a stable and medium sized activity area; 3) dispersa], which includes a regular, territory-like, pattern of spatial distribution. Severai details of these phases are discussed.Peer reviewe

Experimental Study of the Role of Atomic Interactions on Quantum Transport

We report an experimental study of quantum transport for atoms confined in a periodic potential and compare between thermal and BEC initial conditions. We observe ballistic transport for all values of well depth and initial conditions, and the measured expansion velocity for thermal atoms is in excellent agreement with a single-particle model. For weak wells, the expansion of the BEC is also in excellent agreement with single-particle theory, using an effective temperature. We observe a crossover to a new regime for the BEC case as the well depth is increased, indicating the importance of interactions on quantum transport.Comment: 4 pages, 3 figure

Conducta socioespacial frente a un ambiente nuevo de Pseudotropheus tropheops Regan, 1921 (Teleostei, Cichlidae)

Sociospatial behaviour of Pseudotropheus tropheopsReagan, 1921 ina new environment (Teleostei, Cichlidae).- The relationships between agonistic behaviour and spatial variables within a group of six captive inmature Pseudotropheus tropheops is studied. Data on frequency of Eghts and spatial positions are anaiysed during three periods of time within the 24 hours foiiowing modification of the medium. Three phases of social behaviour are established: 1) exploration, performed by the group in schooling; 2) development of Dominance Hierarchy, characterised by a stable and medium sized activity area; 3) dispersa], which includes a regular, territory-like, pattern of spatial distribution. Severai details of these phases are discussed.Peer reviewe