Results 221 to 230 of about 418,792 (249)

A Note on Null Models: Justifying the Methodology

Ecology, 2002
The use of random, or null, models to determine whether species co-occurrences differ from chance expectations is an established technique in community ecology. Several methods have been used to draw conclusions regarding species co-occurrence patterns. We compared a sequential method derived previously with a recently proposed new method.
Bryan Manly, James G. Sanderson
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Influence of the Null-Model on Motif Detection

Proceedings of the 2015 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining 2015, 2015
This paper focuses on the suitability of three different null-models to motif analysis that all get as an input a desired degree sequence. A graph theoretic null-model is defined as a set of graphs together with a probability function. Here we discuss the configuration model, as the simplest model; a variant of the configuration model where multi-edges
Wolfgang E. Schlauch, Katharina A. Zweig, Graph Theory, Network Analysis   +3 more
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Faddeev null-plane model of the nucleon

Physical Review C, 1995
The nucleon is formulated as a relativistic system of three constituent quarks interacting via a zero-range two-body force in the null plane. The covariance of the null-plane Faddeev-like equation under kinematical front-form boosts is discussed. The nucleon wave function is obtained from the numerical solution of the Faddeev equation in the null plane.
, de Araújo WR, , de Melo JP, , Frederico   +2 more
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THE SCHWINGER MODEL ON THE NULL-PLANE

International Journal of Modern Physics E, 2007
We study the Schwinger Model on the null-plane using the Dirac method for constrained systems. The fermion field is analyzed using the natural null-plane projections coming from the γ-algebra and it is shown that the fermionic sector of the Schwinger Model has only second class constraints.
Casana, R., Pimentel, B. M., Zambrano, G. E. R.   +2 more
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P Values for Composite Null Models

Journal of the American Statistical Association, 2000
Abstract The problem of investigating compatibility of an assumed model with the data is investigated in the situation when the assumed model has unknown parameters. The most frequently used measures of compatibility are p values, based on statistics T for which large values are deemed to indicate incompatibility of the data and the model.
M. J. Bayarri, James O. Berger
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Null or minimal models

1994
Abstract The problem with models in phylogenetic inference is one of regress or circularity. Sound models demand either some knowledge of phylogeny, or assumptions about it. If knowledge is claimed, how was that knowledge gained? If assumptions are held to be merely provisional or approximate, how will they be tested by phylogenies that ...
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Null Models in Cluster Validation

1996
A brief overview is given of the problem of validation in classification studies. Attention is concentrated on the specification of appropriate null models for data, with respect to which one may assess some cluster structure that has been obtained as the output of a clustering algorithm.
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Null Models in Ecology.

Ecology, 1997
Kimberly A. With, Nicholas J. Gotelli, Gary R. Graves   +2 more
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A Null Model for Null Models in Biogeography

2014
ROBERT K. COLWELL, DAVID W. WINKLER
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20. A Null Model for Null Models in Biogeography

1984
Robert K. Colwell, David W. Winkler
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