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Design-Dependent Loads In Topology Optimization, Blaise Bourdin, Antonin Chambolle Dec 2003

Design-Dependent Loads In Topology Optimization, Blaise Bourdin, Antonin Chambolle

Faculty Publications

We present, analyze, and implement a new method for the design of the stiffest structure subject to a pressure load or a given field of internal forces. Our structure is represented as a subset S of a reference domain, and the complement of S is made of two other "phases", the "vold" and a fictitious "liquid" that exerts a pressure force on its interface with the solid structure. The problem we consider is to minimize the compliance of the structure S, which is the total work of the pressure and internal forces at the equilibrium displacement. In order to prevent …

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Decoherence At Zero Temperature, G. W. Ford, R. F. O'Connell Dec 2003

Decoherence At Zero Temperature, G. W. Ford, R. F. O'Connell

Faculty Publications

Most discussions of decoherence in the literature consider the high temperature regime but it is also known that, in the presence of dissipation, decoherence can occur even at zero temperature. Whereas most previous investigations all assumed initial decoupling of the quantum system and bath, we consider that the system and environment are entangled at all times. Here, we discuss decoherence for a free particle in an initial Schrödinger cat state. Memory effects are incorporated by use of the single relaxation time model.

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Methods For Estimating Long-Distance Dispersal, Ran Nathan, Gad Perry, James T. Cronin, Allan E. Strand, Michael L. Cain Nov 2003

Methods For Estimating Long-Distance Dispersal, Ran Nathan, Gad Perry, James T. Cronin, Allan E. Strand, Michael L. Cain

Faculty Publications

Long-distance dispersal (LDD) includes events in which propagules arrive, but do not necessarily establish, at a site far removed from their origin. Although important in a variety of ecological contexts, the system-specific nature of LDD makes "far removed" difficult to quantify, partly, but not exclusively, because of inherent uncertainty typically involved with the highly stochastic LDD processes. We critically review the main methods employed in studies of dispersal, in order to facilitate the evaluation of their pertinence to specific aspects of LDD research. Using a novel classification framework, we identify six main methodological groups: biogeographical; Eulerian and Lagrangian movement/redistributional; short-term …

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Heralded Two-Photon Entanglement From Probabilistic Quantum Logic Operations On Multiple Parametric Down-Conversion Sources, Todd B. Pittman, Michelle M. Donegan, Michael J. Fitch, Bryan C. Jacobs, James D. Franson, Pieter Kok, Hwang Lee, Jonathan P. Dowling Nov 2003

Heralded Two-Photon Entanglement From Probabilistic Quantum Logic Operations On Multiple Parametric Down-Conversion Sources, Todd B. Pittman, Michelle M. Donegan, Michael J. Fitch, Bryan C. Jacobs, James D. Franson, Pieter Kok, Hwang Lee, Jonathan P. Dowling

Faculty Publications

An ideal controlled-NOT gate followed by projective measurements can be used to identify specific Bell states of its two input qubits. When the input qubits are each members of independent Bell states, these projective measurements can be used to swap the post-selected entanglement onto the remaining two qubits. Here we apply this strategy to produce heralded two-photon polarization entanglement using Bell states that originate from independent parametric down-conversion sources, and a particular probabilistic controlled-NOT gate that is constructed from linear optical elements. The resulting implementation is closely related to an earlier proposal by Sliwa and Banaszek, and can be intuitively …

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On The Minor-Minimal 3-Connected Matroids Having A Fixed Minor, Manoel Lemos, James Oxley Nov 2003

On The Minor-Minimal 3-Connected Matroids Having A Fixed Minor, Manoel Lemos, James Oxley

Faculty Publications

Let N be a minor of a 3-connected matroid M such that no proper 3-connected minor of M has N as a minor. This paper proves a bound on E(M)-E(N) that is sharp when N is connected. © 2003 Elsevier Ltd. All rights reserved.

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Rules And Fuzzy Rules In Text: Concept, Extraction And Usage, D. H. Kraft, M. J. Martín-Bautista, J. Chen, D. Sánchez Nov 2003

Rules And Fuzzy Rules In Text: Concept, Extraction And Usage, D. H. Kraft, M. J. Martín-Bautista, J. Chen, D. Sánchez

Faculty Publications

Several concepts and techniques have been imported from other disciplines such as Machine Learning and Artificial Intelligence to the field of textual data. In this paper, we focus on the concept of rule and the management of uncertainty in text applications. The different structures considered for the construction of the rules, the extraction of the knowledge base and the applications and usage of these rules are detailed. We include a review of the most relevant works of the different types of rules based on their representation and their application to most of the common tasks of Information Retrieval such as …

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Laplace And Segal-Bargmann Transforms On Hermitian Symmetric Spaces And Orthogonal Polynomials, Mark Davidson, Gestur Ólafsson, Genkai Zhang Oct 2003

Laplace And Segal-Bargmann Transforms On Hermitian Symmetric Spaces And Orthogonal Polynomials, Mark Davidson, Gestur Ólafsson, Genkai Zhang

Faculty Publications

Let D = G/K be a complex bounded symmetric domain of tube type in a complex Jordan algebra V and let Dℝ = J ∩ D ⊂ D be its real form in a formally real Euclidean Jordan algebra J ⊂ V; Dℝ = H/L is a bounded realization of the symmetric cone in J. We consider representations of H that are gotten by the generalized Segal-Bargmann transform from a unitary G-space of holomorphic functions on D to an L2-space on DR. We prove that in the unbounded realization the inverse of the unitary part of the restriction map is …

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Action Based Approach To The Dynamics Of Extended Bodies In General Relativity, Jeeva Anandan, Naresh Dadhich, Parampreet Singh Oct 2003

Action Based Approach To The Dynamics Of Extended Bodies In General Relativity, Jeeva Anandan, Naresh Dadhich, Parampreet Singh

Faculty Publications

We present, for the first time, an action principle that gives the equations of motion of an extended body possessing multipole moments in an external gravitational field, in the weak field limit. From the action, the experimentally observable quantum phase shifts in the wavefunction of an extended object due to the coupling of its multipole moments with the gravitational field are obtained. Also, since the theory may be quantized using the action, the present approach is useful in the interface between general relativity and quantum mechanics.

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The Effect Of Density-Dependent Catastrophes On Population Persistence Time, Chris Wilcox, Bret Elderd Oct 2003

The Effect Of Density-Dependent Catastrophes On Population Persistence Time, Chris Wilcox, Bret Elderd

Faculty Publications

1. There has been increasing recognition that catastrophes are an important factor in modelling threatened populations. However, density dependence has generally been omitted from models of threatened populations on the assumption that this omission yields conservative predictions. We explore the significance of including density-dependent catastrophes in models of threatened populations. 2. Using an analytical model, we show that density-dependent catastrophes have a significant effect on population persistence, decreasing mean persistence time at large population sizes and causing a relative increase at intermediate sizes. 3. We illustrate our results with empirical data from a disease outbreak in crabeater seals Lobodon carcinophagus …

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On Series-Parallel Extensions Of Uniform Matroids, Brahim Chaourar, James Oxley Oct 2003

On Series-Parallel Extensions Of Uniform Matroids, Brahim Chaourar, James Oxley

Faculty Publications

This paper gives an excluded-minor characterization of the class of matroids that are series-parallel extensions of uniform matroids. © 2003 Elsevier Ltd. All rights reserved.

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The Nonexistence Of Regularization Operators, Ricardo Estrada Oct 2003

The Nonexistence Of Regularization Operators, Ricardo Estrada

Faculty Publications

We show that there are no continuous regularization procedures for the extension of distributions. We also show that there are no continuous projection operators from the spaces of distributions onto subspaces of distributions with support on a given closed set. © 2003 Elsevier Inc. All rights reserved.

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Quantum Noise In Gravitational-Wave Interferometers: Overview And Recent Developments, Thomas Corbitt, Nergis Mavalvala Sep 2003

Quantum Noise In Gravitational-Wave Interferometers: Overview And Recent Developments, Thomas Corbitt, Nergis Mavalvala

Faculty Publications

We present an overview of quantum noise in gravitational wave interferometers. Gravitational wave detectors are extensively modified variants of a Michelson interferometer and the quantum noise couplings are strongly influenced by the interferometer configuration. We describe recent developments in the treatment of quantum noise in the complex interferometer configurations of present-day and future gravitational-wave detectors. In addition, we explore prospects for the use of squeezed light in future interferometers, including consideration of the effects of losses, and the choice of optimal readout schemes.

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The Cayley-Hamilton And Frobenius Theorems Via The Laplace Transform, William A. Adkins, Mark G. Davidson Sep 2003

The Cayley-Hamilton And Frobenius Theorems Via The Laplace Transform, William A. Adkins, Mark G. Davidson

Faculty Publications

The Cayley-Hamilton theorem on the characteristic polynomial of a matrix A and Frobenius' theorem on minimal polynomial of A are deduced from the familiar Laplace transform formula ℒ(e ) = (sI - A) . This formula is extended to a formal power series ring over an algebraically closed field of characteristic 0, so that the argument applies in the more general setting of matrices over a field of characteristic 0. © 2003 Elsevier Science Inc. All rights reserved. At -1

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Scientific Collaboratories In Higher Education: Exploring Learning Style Preferences And Perceptions Of Technology, Diane H. Sonnenwald, Bin Li Sep 2003

Scientific Collaboratories In Higher Education: Exploring Learning Style Preferences And Perceptions Of Technology, Diane H. Sonnenwald, Bin Li

Faculty Publications

Scientific collaboratories hold the promise of providing students access to specialized scientific instruments, data and experts, enabling learning opportunities perhaps otherwise not available. However, evaluation of scientific collaboratories in higher education has lagged behind their development. We conducted a repeated-measures study that provided data regarding social interaction learning styles and perceptions of a scientific collaboratory system from 40 university science students working face-to-face and remotely. Students with a strong competitive learning style preference or who worked with a student with a strong competitive learning style reported a slightly more positive perception of the relative advantage, compatibility and complexity of the …

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Well Posed Constraint-Preserving Boundary Conditions For The Linearized Einstein Equations, Gioel Calabrese, Jorge Pullin, Oscar Reula, Olivier Sarbach, Manuel Tiglio Sep 2003

Well Posed Constraint-Preserving Boundary Conditions For The Linearized Einstein Equations, Gioel Calabrese, Jorge Pullin, Oscar Reula, Olivier Sarbach, Manuel Tiglio

Faculty Publications

In this paper we address the problem of specifying boundary conditions for Einstein's equations when linearized around Minkowski space using the generalized Einstein-Christoffel symmetric hyperbolic system of evolution equations. The boundary conditions we work out guarantee that the constraints are satisfied provided they are satisfied on the initial slice and ensures a well posed initial-boundary value formulation. We consider the case of a manifold with a non-smooth boundary, as is the usual case of the cubic boxes commonly used in numerical relativity. The techniques discussed should be applicable to more general cases, as linearizations around more complicated backgrounds, and may …

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Riemann And Edalat Integration On Domains, Jimmie D. Lawson, Bin Lu Aug 2003

Riemann And Edalat Integration On Domains, Jimmie D. Lawson, Bin Lu

Faculty Publications

The main result of this paper is that the domain-theoretic approach to the generalized Riemann integral first introduced by Edalat extends to a large class of spaces that can be realized as the set of maximal points of domains. The approach is based on the theory of a Riemann-Stieltjes type integral on a topological space with respect to a finitely additive measure. We develop the theory of this integral for a bounded function f defined on the maximal points of a continuous domain and show that it gives an alternate approach to the Edalat integral. © 2002 Elsevier B.V. All …

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Generalized Q-Deformed Symplectic Sp(4) Algebra For Multi-Shell Applications, K. D. Sviratcheva, A. I. Georgieva, J. P. Draayer Jul 2003

Generalized Q-Deformed Symplectic Sp(4) Algebra For Multi-Shell Applications, K. D. Sviratcheva, A. I. Georgieva, J. P. Draayer

Faculty Publications

A multi-shell generalization of a fermion representation of the q-deformed compact symplectic spq(4) algebra is introduced. An analytic form for the action of two or more generators of the Spq (4) symmetry on the basis states is determined and the result used to derive formulae for the overlap between number-preserving states as well as for matrix elements of a model Hamiltonian. A second-order operator in the generators of Sp q(4) is identified that is diagonal in the basis set and that reduces to the Casimir invariant of the sp(4) algebra in the non-deformed limit of the theory. The results can …

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Global Patterns Of Dissolved N, P And Si In Large Rivers, R. Eugene Turner, Nancy N. Rabalais, D. Justic', Q. Dortch Jul 2003

Global Patterns Of Dissolved N, P And Si In Large Rivers, R. Eugene Turner, Nancy N. Rabalais, D. Justic', Q. Dortch

Faculty Publications

The concentration of dissolved inorganic nitrogen (DIN), dissolved nitrate-N, Total-N (TN), dissolved inorganic phosphate (DIP), total phosphorus (TP), dissolved silicate-Si (DSi) and their ratios in the world's largest rivers are examined using a global data base that includes 37% of the earth's watershed area and half its population. These data were compared to water quality in 42 subbasins of the relatively well-monitored Mississippi River basin (MRB) and of 82 small watersheds of the United States. The average total nitrogen concentration varies over three orders of magnitude among both world river watersheds and the MRB, and is primarily dependent on variations …

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Wigner Distribution Function Approach To Dissipative Problems In Quantum Mechanics With Emphasis On Decoherence And Measurement Theory, R. F. O'Connell Jun 2003

Wigner Distribution Function Approach To Dissipative Problems In Quantum Mechanics With Emphasis On Decoherence And Measurement Theory, R. F. O'Connell

Faculty Publications

We first review the usefulness of the Wigner distribution functions (WDFs), associated with Lindblad and pre-master equations, for analysing a host of problems in quantum optics where dissipation plays a major role, an arena where weak coupling and long-time approximations are valid. However, we also show their limitations for the discussion of decoherence, which is generally a short-time phenomenon with decay rates typically much smaller than typical dissipative decay rates. We discuss two approaches to the problem both of which use a quantum Langevin equation as a starting-point: (a) use of a reduced WDF but in the context of an …

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Assessment Of The Local Stress State Through Macroscopic Variables, Robert P. Lipton May 2003

Assessment Of The Local Stress State Through Macroscopic Variables, Robert P. Lipton

Faculty Publications

Macroscopic quantities beyond effective elastic tensors are presented that can be used to assess the local state of stress within a composite in the linear elastic regime. These are presented in a general homogenization context. It is shown that the gradient of the effective elastic property can be used to develop a lower bound on the maximum pointwise equivalent stress in the fine-scale limit. Upper bounds are more sensitive and are correlated with the distribution of states of the equivalent stress in the fine-scale limit. The upper bounds are given in terms of the macrostress modulation function. This function gauges …

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The Utility Of Single Nucleotide Polymorphisms In Inferences Of Population History, Robb T. Brumfield, Peter Beerli, Deborah A. Nickerson, Scott V. Edwards May 2003

The Utility Of Single Nucleotide Polymorphisms In Inferences Of Population History, Robb T. Brumfield, Peter Beerli, Deborah A. Nickerson, Scott V. Edwards

Faculty Publications

Single nucleotide polymorphisms (SNPs) represent the most widespread type of sequence variation in genomes, yet they have only emerged recently as valuable genetic markers for revealing the evolutionary history of populations. Their occurrence throughout the genome also makes them ideal for analyses of speciation and historical demography, especially in light of recent theory suggesting that many unlinked nuclear loci are needed to estimate population genetic parameters with statistical confidence. In spite of having lower variation compared with microsatellites, SNPs should make the comparison of genomic diversities and histories of different species (the core goal of comparative biogeography) more straightforward than …

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Gauss-Manin Connections For Arrangements, I Eigenvalues, Daniel C. Cohen, Peter Orlik May 2003

Gauss-Manin Connections For Arrangements, I Eigenvalues, Daniel C. Cohen, Peter Orlik

Faculty Publications

We construct a formal connection on the Aomoto complex of an arrangement of hyperplanes, and use it to study the Gauss Manin connection for the moduli space of the arrangement in the cohomology of a complex rank one local system. We prove that the eigenvalues of the Gauss Manin connection are integral linear combinations of the weights which define the local system.

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When Does The Class [A→B] Consist Of Continuous Domains?, Jimmie D. Lawson, Luoshan Xu Apr 2003

When Does The Class [A→B] Consist Of Continuous Domains?, Jimmie D. Lawson, Luoshan Xu

Faculty Publications

Given classes of domains (or topological spaces) A and B, when are all function spaces [A→B] again continuous domains? The principle result of this paper is that for A either all compact and core compact spaces or only the single domain consisting of a decreasing sequence with two lower bounds, then the largest B consists of all continuous domains such that ↓x is a sup-semilattice for each x. We also establish an analogue for L-domains. © 2002 Elsevier Science B.V. All rights reserved.

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The Structure Of A 3-Connected Matroid With A 3-Separating Set Of Essential Elements, James Oxley Apr 2003

The Structure Of A 3-Connected Matroid With A 3-Separating Set Of Essential Elements, James Oxley

Faculty Publications

An element e of a 3-connected matroid M is essential if neither the deletion nor the contraction of e from M is 3-connected. Tutte's 1966 Wheels and Whirls Theorem proves that the only 3-connected matroids in which every element is essential are the wheels and whirls. It was proved by Oxley and Wu that if a 3-connected matroid M has a non-essential element, then it has at least two such elements. Moreover, the set of essential elements of M can be partitioned into classes where two elements are in the same class if M has a fan, a maximal partial …

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Valuation Of Continuous And Intermittent Phragmites Control, R. Eugene Turner, R. S. Warren Apr 2003

Valuation Of Continuous And Intermittent Phragmites Control, R. Eugene Turner, R. S. Warren

Faculty Publications

Quantifying the relative value of Phragmites australis and Spartina alterniflora habitat is important to evaluate the benefits and risks of different attempts to address Phragmites expansion on the U.S. eastern seaboard. Two contrasting approaches commonly used to restore tidal marsh habitats invaded by Phragmites communities involve spraying Phragmites with herbicide only when its coverage of a particular marsh area is near or close to 100%. Alternatively, after the first application, herbicide is annually applied on any surviving patches of Phragmites present in a mosaic of other marsh vegetation. A model is introduced to evaluate the relative habitat value of these …

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Louisiana Agriculture Spring, 2003, Lsu Agcenter Apr 2003

Louisiana Agriculture Spring, 2003, Lsu Agcenter

Louisiana Agriculture

No abstract provided.

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Unitary Representations And Theta Correspondence For Type I Classical Groups, Hongyu He Apr 2003

Unitary Representations And Theta Correspondence For Type I Classical Groups, Hongyu He

Faculty Publications

In this paper, we discuss the positivity of the Hermitian form (,)π introduced by Li in Invent. Math. 27 (1989) 237-255. Let (G1, G2) be a type I dual pair with G1 the smaller group. Let π be an irreducible unitary representation in the semistable range of θ(MG1, MG2) (see Communications in Contemporary Mathematics, Vol. 2, 2000, pp. 255-283). We prove that the invariant Hermitian form (,)π is positive semidefinite under certain restrictions on the size of G2 and a mild growth condition on the matrix coefficients of π. Therefore, if (,)π does not vanish, θ(MG1, MG2) (π) is unitary. …

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Partitioning Into Graphs With Only Small Components, Noga Alon, Guoli Ding, Bogdan Oporowski, Dirk Vertigan Mar 2003

Partitioning Into Graphs With Only Small Components, Noga Alon, Guoli Ding, Bogdan Oporowski, Dirk Vertigan

Faculty Publications

The paper presents several results on edge partitions and vertex partitions of graphs into graphs with bounded size components. We show that every graph of bounded tree-width and bounded maximum degree admits such partitions. We also show that an arbitrary graph of maximum degree four has a vertex partition into two graphs, each of which has components on at most 57 vertices. Some generalizations of the last result are also discussed. © 2002 Elsevier Science (USA). All rights reserved.

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The Betti Numbers Of Some Finite Racks, R. A. Litherland, Sam Nelson Mar 2003

The Betti Numbers Of Some Finite Racks, R. A. Litherland, Sam Nelson

Faculty Publications

We show that the lower bounds for Betti numbers given in (J. Pure Appl. Algebra 157 (2001) 135) are equalities for a class of racks that includes dihedral and Alexander racks. We confirm a conjecture from the same paper by defining a splitting for the short exact sequence of quandle chain complexes. We define isomorphisms between Alexander racks of certain forms, and we also list the second and third homology groups of some dihedral and Alexander quandles. © 2002 Elsevier Science B.V. All rights reserved.

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Review Of The Final Frontier, Michael F. Russo Feb 2003

Review Of The Final Frontier, Michael F. Russo

Faculty Publications

No abstract provided.

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