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Function V (function + v)

Distribution by Scientific Domains

Mathematics and Statistics	33%

Selected Abstracts

COALITIONS AMONG INTELLIGENT AGENTS: A TRACTABLE CASE

COMPUTATIONAL INTELLIGENCE, Issue 1 2006
M. V. Belmonte
Coalition formation is an important mechanism for cooperation in multiagent systems. In this paper we address the problem of coalition formation among self-interested agents in superadditive task-oriented domains. We assume that each agent has some "structure," i.e., that it can be described by the values taken by a set of m nonnegative attributes that represent the resources w each agent is endowed with. By defining the coalitional value as a function V of w, we prove a sufficient condition for the existence of a stable payment configuration,in the sense of the core,in terms of certain properties of V. We apply these ideas to a simple case that can be described by a linear program and show that it is possible to compute for it,in polynomial time,an optimal task allocation and a stable payment configuration. [source]

HS08 CONGENITAL HAND: THE DEFORMITY-DEFICIENCY INDEX

ANZ JOURNAL OF SURGERY, Issue 2007
L. C. Teoh
Congenital hand is a complex and vast subject therefore classification is very necessary for the purpose of teaching, communication and guide treatment. The first comprehensive and yet user friendly classification was proposed by Swanson et al. in 1976. This classification based on etiopathogenic is popularly known as the ,IFSSH 7 groups classification'. (I) Failure of formation: transverse or longitudinal (II) Failure of differentiation (III) Polydactyly (IV) Overgrowth (V) Undergrowth (VI) Amniotic band syndrome (VII) Generalized skeletal syndromes. However this classification was found not able to satisfactorily classify 20,30% of cases. Other classifications based on genetic defects, teratogenic sequence and syndromics were being introduced previously and continue to be used parallel with the IFSSH classification. Furthermore the classification continue to be besieged by multiple morphological types of deformity in a same hand. Ogino introduced the JSSH expanded classification to address some of the deficiencies of the IFSSH classification. For a beginner in treating congenital hand, it is indeed daunting, as the variations in morphology, the degree of severity and functional deficit even in the same diagnosis can be very different. It is usual to find further sub classifications. For the purpose of guiding treatment, I propose the concept of deformity/ deficiency index. Group I) The imbalance/ small in size II) Extra digits III) Mal positioned/ Mal-aligned IV) Poor/ No function V) Total absent. The residual functional decreases from group I to V. And similarly the reconstruction becomes complex and difficult. [source]

Large deviations for a catalytic Fleming-Viot branching system

COMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 7 2007
Ilie Grigorescu
We consider a jump-diffusion process describing a system of diffusing particles that upon contact with an obstacle (catalyst) die and are replaced by an independent offspring with position chosen according to a weighted average of the remaining particles. The obstacle is a bounded nonnegative function V(x) and the birth/death mechanism is similar to the Fleming-Viot critical branching. Since the mass is conserved, we prove a hydrodynamic limit for the empirical measure, identified as the solution to a generalized semilinear (reaction-diffusion) equation, with nonlinearity given by a quadratic operator. A large-deviation principle from the deterministic hydrodynamic limit is provided. The upper bound is given in any dimension, and the lower bound is proven for d = 1 and V bounded away from 0. An explicit formula for the rate function is provided via an Orlicz-type space. © 2006 Wiley Periodicals, Inc. [source]

Multidimensional density estimation and phase-space structure of dark matter haloes

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
Sanjib Sharma
ABSTRACT We present a method to numerically estimate the densities of a discretely sampled data based on a binary space partitioning tree. We start with a root node containing all the particles and then recursively divide each node into two nodes each containing roughly equal number of particles, until each of the nodes contains only one particle. The volume of such a leaf node provides an estimate of the local density and its shape provides an estimate of the variance. We implement an entropy-based node splitting criterion that results in a significant improvement in the estimation of densities compared to earlier work. The method is completely metric free and can be applied to arbitrary number of dimensions. We use this method to determine the appropriate metric at each point in space and then use kernel-based methods for calculating the density. The kernel-smoothed estimates were found to be more accurate and have lower dispersion. We apply this method to determine the phase-space densities of dark matter haloes obtained from cosmological N -body simulations. We find that contrary to earlier studies, the volume distribution function v(f) of phase-space density f does not have a constant slope but rather a small hump at high phase-space densities. We demonstrate that a model in which a halo is made up by a superposition of Hernquist spheres is not capable in explaining the shape of v(f) versus f relation, whereas a model which takes into account the contribution of the main halo separately roughly reproduces the behaviour as seen in simulations. The use of the presented method is not limited to calculation of phase-space densities, but can be used as a general purpose data-mining tool and due to its speed and accuracy it is ideally suited for analysis of large multidimensional data sets. [source]

On the usage and measurement of landscape connectivity

OIKOS, Issue 1 2000
Lutz Tischendorf
This paper examines the usage and measurement of "landscape connectivity" in 33 recent studies. Connectivity is defined as the degree to which a landscape facilitates or impedes movement of organisms among resource patches. However, connectivity is actually used in a variety of ways in the literature. This has led to confusion and lack of clarity related to (1) function vs structure, (2) patch isolation vs landscape connectivity and, (3) corridors vs connectivity. We suggest the term connectivity should be reserved for its original purpose. We highlight nine studies; these include modeling studies that actually measured connectivity in accordance with the definition, and empirical studies that measured key components of connectivity. We found that measurements of connectivity provide results that can be interpreted as recommending habitat fragmentation to enhance landscape connectivity. We discuss reasons for this misleading conclusion, and suggest a new way of quantifying connectivity, which avoids this problem. We also recommend a method for reducing sampling intensity in landscape-scale empirical studies of connectivity. [source]

Traces of Sobolev functions with one square integrable directional derivative

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 2 2006
M. Gregoratti
Abstract We consider the Sobolev spaces of square integrable functions v, from ,n or from one of its hyperquadrants Q, into a complex separable Hilbert space, with square integrable sum of derivatives ,,,,v. In these spaces we define closed trace operators on the boundaries ,Q and on the hyperplanes {r,, = z}, z , ,\{0}, which turn out to be possibly unbounded with respect to the usual L2 -norm for the image. Therefore, we also introduce bigger trace spaces with weaker norms which allow to get bounded trace operators, and, even if these traces are not L2, we prove an integration by parts formula on each hyperquadrant Q. Then we discuss surjectivity of our trace operators and we establish the relation between the regularity properties of a function on ,n and the regularity properties of its restrictions to the hyperquadrants Q. Copyright © 2005 John Wiley & Sons, Ltd. [source]