We present an algorithm for graph based saliency computation that utilizes the underlying dense subgraphs in finding visually salient regions in an image. To compute the salient regions, the model first obtains a saliency map using random walks on a Markov chain. Next, k-dense subgraphs are detected to further enhance the salient regions in the image. Dense subgraphs convey more information abo...

This paper concerns the problem of computing the densest k-vertex subgraph of a given graph, namely, the subgraph with the most edges, or with the highest edges-to-vertices ratio. A sequence of approximation algorithms is developed for the problem! with each step yielding a better ratio at the cost of a more complicated solution. The approximation ratio of our final algorithm is O(n0,3””5). We ...

We investigated habitat selection using singleand mixed-scale modeling at 2 spatial scales, stand and home range, by the only known population of American martens (Martes americana) remaining in the historical range of the Humboldt subspecies (M. a. humboldtensis) in California, USA. During 2000 and 2001, we sampled a 12 3 14 grid with 2-km spacing, using 2 sooted track plates at each grid poin...

We simulate the effects of an intrinsically dense boundary layer at the base of the mantle on the thermal structure of D and the dynamics of the lower mantle. Using a finite element model of thermo-chemical convection in 2-D with a Rayleigh number of 10, we investigate the dynamic consequences of varying the density and of increasing thermal diffusivity in the basal layer to simulate enrichment...

[Received on 25 August 2005] For two-dimensional boundary integral equations of the first kind with logarithm kernels, the use of the conventional boundary element methods gives linear algebraic systems with dense matrix. In a recent work [J. Comput. Math., 22 (2004), pp. 287-298], it is demonstrated that the dense matrix can be replaced by a sparse one if appropriate graded meshes are used in ...

A quantitative analysis of myocardial mechanics is fundamental to understanding cardiac function, diagnosis of heart disease, and assessment of therapeutic intervention. Displacement encoding with stimulated-echo (DENSE) magnetic resonance imaging (MRI) technique was developed to track the three-dimensional (3D) displacement vector of discrete material grid points in the myocardial tissue. Desp...

We develop parametrization and alignment techniques for shapes of spherical surfaces in 3D space with the goals of quantifying shape similarities and dissimilarities and modeling shape variations observed within a class of objects. The parametrization techniques are refinements of methods due to Praun and Hoppe and yield parametric mesh representations of spherical surfaces. The main new elemen...

Aiming at the simulation of dense granular flows, we propose and test a numerical method based on successive convex complementarity problems. This approach originates from a multibody description of the granular flow: all the particles are simulated as rigid bodies with arbitrary shapes and frictional contacts. Unlike the discrete element method (DEM), the proposed approach does not require sma...

In this article we introduce a fast iterative solver for sparse matrices arising from the finite element discretization of elliptic PDEs. The solver uses a fast direct multi-frontal solver as a preconditioner to a simple fixed point iterative scheme. This approach combines the advantages of direct and iterative schemes to arrive at a fast, robust and accurate solver. We will show that this solv...

The flow characteristics of a gravity-driven dense granular flow in a granular bed with a contracted drainage orifice are studied by using discrete element method and quantitative analysis. Three values of discharging rates, ranging from fast to slow dense flows, are investigated. Time variations and derivatives of mean forces and velocities, as well as their respective correlations, are analyz...