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Discrete Space (discrete + space)

Distribution by Scientific Domains
Mathematics and Statistics40%

Selected Abstracts

Modelling the basin-scale demography of Calanus finmarchicus in the north-east Atlantic

FISHERIES OCEANOGRAPHY, Issue 5 2005
DOUGLAS C. SPEIRS
Abstract In this paper, we report on a coupled physical,biological model describing the spatio-temporal distribution of Calanus finmarchicus over an area of the North Atlantic and Norwegian Sea from 56°N, 30°W to 72°N, 20°E. The model, which explicitly represents all the life-history stages, is implemented in a highly efficient discrete space,time format which permits wide-ranging dynamic exploration and parameter optimization. The underlying hydrodynamic driving functions come from the Hamburg Shelf-Ocean Model (HAMSOM). The spatio-temporal distribution of resources powering development and reproduction is inferred from SeaWiFS sea-surface colour observations. We confront the model with distributional data inferred from continuous plankton recorder observations, overwintering distribution data from a variety of EU, UK national and Canadian programmes which were collated as part of the Trans-Atlantic Study of Calanus (TASC) programme, and high-frequency stage-resolved point time-series obtained as part of the TASC programme. We test two competing hypotheses concerning the control of awakening from diapause and conclude that only a mechanism with characteristics similar to photoperiodic control can explain the test data. [source]

An enhanced-physics-based scheme for the NS-, turbulence model

NUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 6 2010
William W. Miles
Abstract We study a new enhanced-physics-based numerical scheme for the NS-alpha turbulence model that conserves both energy and helicity. Although most turbulence models (in the continuous case) conserve only energy, NS-alpha is one of only a very few that also conserve helicity. This is one reason why it is becoming accepted as the most physically accurate turbulence model. However, no numerical scheme for NS-alpha, until now, conserved both energy and helicity, and thus the advantage gained in physical accuracy by modeling with NS-alpha could be lost in a computation. This report presents a finite element numerical scheme, and gives a rigorous analysis of its conservation properties, stability, solution existence, and convergence. A key feature of the analysis is the identification of the discrete energy and energy dissipation norms, and proofs that these norms are equivalent (provided a careful choice of filtering radius) in the discrete space to the usual energy and energy dissipation norms. Numerical experiments are given to demonstrate the effectiveness of the scheme over usual (helicity-ignoring) schemes. A generalization of this scheme to a family of high-order NS-alpha-deconvolution models, which combine the attractive physical properties of NS-alpha with the high accuracy gained by combining ,-filtering with van Cittert approximate deconvolution. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010 [source]

Bayesian Detection of Clusters and Discontinuities in Disease Maps

BIOMETRICS, Issue 1 2000
Leonhard Knorr-Held
Summary. An interesting epidemiological problem is the analysis of geographical variation in rates of disease incidence or mortality. One goal of such an analysis is to detect clusters of elevated (or lowered) risk in order to identify unknown risk factors regarding the disease. We propose a nonparametric Bayesian approach for the detection of such clusters based on Green's (1995, Biometrika82, 711,732) reversible jump MCMC methodology. The prior model assumes that geographical regions can be combined in clusters with constant relative risk within a cluster. The number of clusters, the location of the clusters, and the risk within each cluster is unknown. This specification can be seen as a change-point problem of variable dimension in irregular, discrete space. We illustrate our method through an analysis of oral cavity cancer mortality rates in Germany and compare the results with those obtained by the commonly used Bayesian disease mapping method of Besag, York, and Mollié (1991, Annals of the Institute of Statistical Mathematics, 43, 1,59). [source]

Location, Location, Location: Gender and the Archaeology of Urban Settlement

JOURNAL OF ARCHITECTURAL EDUCATION, Issue 3 2002
Sharon Haar
The word community describes both organizations of individuals with a shared identity and discrete spaces shared by these individuals. The elision of the two definitions,one social, the other spatial, contains a contested condition. Typically conceived as separate and gendered spheres, domesticity and urbanity have been crucial to the changing physical definition of modern space. The destruction of the Hull House Social Settlement and the building of an urban campus, the University of Illinois at Chicago, is a case study in the nature of the often gendered and continuing contest over the public space of the city. [source]

I,Time, Topology and Physical Geometry

ARISTOTELIAN SOCIETY SUPPLEMENTARY VOLUME, Issue 1 2010
Tim Maudlin
The standard mathematical account of the sub-metrical geometry of a space employs topology, whose foundational concept is the open set. This proves to be an unhappy choice for discrete spaces, and offers no insight into the physical origin of geometrical structure. I outline an alternative, the Theory of Linear Structures, whose foundational concept is the line. Application to Relativistic space-time reveals that the whole geometry of space-time derives from temporal structure. In this sense, instead of spatializing time, Relativity temporalizes space. [source]