Multiple Imputation for Missing Network Data

In this thesis we developed, implemented, and evaluated multiple imputation algorithms for missing network data. The algorithms are able to handle cross-sectional, longitudinal,and multiplex network structures, as well as nodal attributes (coevolving behaviors). They were implemented for the two most important statistical network model families in the social sciences, that is, Exponential Random Graph Models and Stochastic Actor-oriented Models

New Deal Public Works in the Florida Panhandle, 1933-1940

The 1930s represented a time of profound change in the South as it did across the nation. An examination of New Deal agencies and their public works in the Florida Panhandle highlights the dynamic character of federal projects and their impact upon human and natural landscapes. Federal aid in the form of public works projects in the sixteen western panhandle counties created a visibly-new world for residents. 1 The construction of roads and towns in previously-raw coastal timberlands led to a transformation of place and the emergence of not only new commercial and recreational spaces, but the development of a military-industrial complex that remains in place today

Turing conditions for pattern forming systems on evolving manifolds

The study of pattern-forming instabilities in reaction-diffusion systems on growing or otherwise time-dependent domains arises in a variety of settings, including applications in developmental biology, spatial ecology, and experimental chemistry. Analyzing such instabilities is complicated, as there is a strong dependence of any spatially homogeneous base states on time, and the resulting structure of the linearized perturbations used to determine the onset of instability is inherently non-autonomous. We obtain general conditions for the onset and structure of diffusion driven instabilities in reaction-diffusion systems on domains which evolve in time, in terms of the time-evolution of the Laplace-Beltrami spectrum for the domain and functions which specify the domain evolution. Our results give sufficient conditions for diffusive instabilities phrased in terms of differential inequalities which are both versatile and straightforward to implement, despite the generality of the studied problem. These conditions generalize a large number of results known in the literature, such as the algebraic inequalities commonly used as a sufficient criterion for the Turing instability on static domains, and approximate asymptotic results valid for specific types of growth, or specific domains. We demonstrate our general Turing conditions on a variety of domains with different evolution laws, and in particular show how insight can be gained even when the domain changes rapidly in time, or when the homogeneous state is oscillatory, such as in the case of Turing-Hopf instabilities. Extensions to higher-order spatial systems are also included as a way of demonstrating the generality of the approach

Amplitude death criteria for coupled complex Ginzburg-Landau systems

Amplitude death, which occurs in a system when one or more macroscopic wavefunctions collapse to zero, has been observed in mutually coupled solid-state lasers, analog circuits, and thermoacoustic oscillators, to name a few applications. While studies have considered amplitude death on oscillator systems and in externally forced complex Ginzburg-Landau systems, a route to amplitude death has not been studied in autonomous continuum systems. We derive simple analytic conditions for the onset of amplitude death of one macroscopic wavefunction in a system of two coupled complex Ginzburg-Landau equations with general nonlinear self- and cross-interaction terms. Our results give a more general theoretical underpinning for recent amplitude death results reported in the literature, and suggest an approach for tuning parameters in such systems so that they either permit or prohibit amplitude death of a wavefunction (depending on the application). Numerical simulation of the coupled complex Ginzburg-Landau equations, for examples including cubic, cubic-quintic, and saturable nonlinearities, is used to illustrate the analytical results.Comment: 7 pages, 4 figure

Skylab Facilities and Operations

The purpose of this paper is to outline the essential objectives and elements of the Skylab Program and to describe the impact of the Program on the Kennedy Space Center. The operational test flows and the required facility modifications to support Skylab checkout and launch requirements will be highlighted

An Environmental History of the New Deal in Mississippi and Florida

Keywords: New Deal, Environmental History, United States South, Mississippi, Florida, Gulf Coast, TVA, Franklin Delano Roosevelt, landscape, lumber industry, CCC, WPA, state parks. The 1930s represented a time of distinct and encompassing change in the United States South. In assessing the impact of New Deal agencies and public works, this dissertation examines three distinct southern areas-northeast Mississippi, the Mississippi Gulf Coast, and the Florida Panhandle-highlighting the dynamic and fluid character of federal projects and their impact on landscapes human and natural. In the hilly Tennessee River valley of northeast Mississippi, the federally-funded incorporation of the Tennessee Valley Authority led to an immediate transformation of landscape and the opening of novel possibilities within a newly-anointed “region” for the area\u27s residents. Public works projects on the Mississippi Gulf Coast likewise reoriented the perspective of place by improving transportation networks and reinvigorating locally (and by the 1930s, globally) significant industries like lumber and seafood products. Federal aid in the fifteen western Florida Panhandle counties created a visibly new world for residents, as well. The construction of new roads and towns out of previously raw coastal timberlands led to a transformation of place and the emergence of not only new commercial and recreational spaces, but the development of a military-industrial complex that remains in place today. In addition to canvassing secondary historical works, primary sources utilized for this project include a wide range of regional newspapers and journals from Mississippi and Florida, federal and state agency reports, promotional material and publications, paper collections of New Deal officials, as well as oral histories and quantitative use of census data. Utilizing these previously neglected sources to demonstrate the malleability of post-Depression public works, this dissertation provides a nuanced historical understanding of the New Deal in the South

Bifurcations and dynamics emergent from lattice and continuum models of bioactive porous media

We study dynamics emergent from a two-dimensional reaction--diffusion process modelled via a finite lattice dynamical system, as well as an analogous PDE system, involving spatially nonlocal interactions. These models govern the evolution of cells in a bioactive porous medium, with evolution of the local cell density depending on a coupled quasi--static fluid flow problem. We demonstrate differences emergent from the choice of a discrete lattice or a continuum for the spatial domain of such a process. We find long--time oscillations and steady states in cell density in both lattice and continuum models, but that the continuum model only exhibits solutions with vertical symmetry, independent of initial data, whereas the finite lattice admits asymmetric oscillations and steady states arising from symmetry-breaking bifurcations. We conjecture that it is the structure of the finite lattice which allows for more complicated asymmetric dynamics. Our analysis suggests that the origin of both types of oscillations is a nonlocal reaction-diffusion mechanism mediated by quasi-static fluid flow.Comment: 30 pages, 21 figure