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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Convergence and Boundedness of Probability-One Homotopies for Model Order Reduction

Wang, Yuan 18 September 1997 (has links)
The optimal model reduction problem, whether formulated in the H² or H<sup>∞</sup> norm frameworks, is an inherently nonconvex problem and thus provides a nontrivial computational challenge. This study systematically examines the requirements of probability-one homotopy methods to guarantee global convergence. Homotopy algorithms for nonlinear systems of equations construct a continuous family of systems, and solve the given system by tracking the continuous curve of solutions to the family. The main emphasis is on guaranteeing transversality for several homotopy maps based upon the pseudogramian formulation of the optimal projection equations and variations based upon canonical forms. These results are essential to the probability-one homotopy approach by guaranteeing good numerical properties in the computational implementation of the homotopy algorithms. / Ph. D.
2

First and Second Language Use of Case, Aspect, and Tense in Finnish and English

Kelley, Torin 12 August 2021 (has links)
Important to understanding bilingualism and second language (L2) learning are L2 morphological processing and acquisition of tense and aspect. This study used narrative elicitation to examine the expression of boundedness and definiteness in Finnish and English by first language (L1) Finnish speakers who speak English as an L2 and L1 English speakers who speak Finnish as an L2. In Finnish, boundedness and definiteness were largely portrayed by using partitive and accusative cases, though tense and aspect conjugation also played a role. In English, boundedness was largely conveyed through tense and aspect conjugation and definiteness through article usage. Both L1 speaker groups appeared to demonstrate first language transfer as well as form following meaning in acquisition, meaning that a given form will be acquired first in contexts where the meaning of the form is inherent. There was also evidence pointing to avoidance by L2 speakers. Notably, varying interpretations of what the images used portrayed also seemed to play a role in some of the differences in responses across groups. The narrative elicitation methodology was useful in producing meaningful and easily comparable results.
3

Variability and Stability of a Dragonfly Assemblage

Crowley, P. H., Johnson, D. M. 01 May 1992 (has links)
Using 12 years of monthly sweep-net data from 9-12 permanent sampling stations, we evaluated the variability and stability of the dragonfly assemblage in Bays Mountain Lake (northeastern Tennessee, USA). To do this, we adopted the view that a stable assemblage (i.e. one capable of recovering quickly from disturbances) should have low variability (i.e. high persistence of taxa, relatively constant densities, and high rank concordance), except with disturbances more intense and frequent than those in this system. Moreover, a stable assemblage should contain populations that exhibit density dependence and should tend to remain within a restricted range of densities (boundedness), shifting toward a narrow density interval between generations (attraction). To test some specific predictions derived from these views, we analyzed 12-year sequences of larval population sizes just before the onset of emergence for the 13 dominant dragonfly taxa in the lake. Most but not all of the 13 dominant taxa persisted during the 12-year period. Variabilities of taxon densities, measured as standard deviations across generations of log-transformed population sizes, were representative of the broad range for other invertebrates but somewhat higher than those of terrestrial vertebrates. There were fewer than three significant abundance trends over the 12-year period, and rank concordance between generations was high (W=0.716). Density dependence was detected among some of the dragonfly density sequences by five different methods. Using techniques presented in the companion paper, we found strong indications of both boundedness and attraction in the whole assemblage. We conclude tentatively that an assemblage consisting of at least 11 of the 13 dominant dragonfly taxa at Bays Mountain Lake has low-to-moderate variability and is stable, but that the complete 29-species assemblage is probably not stable at the scale of this single lake. We emphasize the need for coupling such long-term descriptive analyses with studies of responses to experimental disturbances.
4

Semántica léxica y estructuración aspectual/eventiva: telicidad, perfectividad y delimitación en el análisis de las cópulas españolas

Mangialavori Rasia, Ma. Eugenia 25 September 2017 (has links)
La alternancia ser/estar ha inspirado numerosos estudios y, consecuentemente, una significativa variedad de conceptos técnicos. Ante este panorama, proponemos avanzar hacia un refinamiento de los parámetros aspectuales empleados, con énfasis en los niveles lingüísticos en los que se originan y en la diferenciación entre semántica léxica/construccional. A partir de diagnósticos específicos, proponemos: primero, que ser y estar se alejan de la noción estándar de cópula y verbo estativo y son cuanto menos ambiguas respecto al tipo eventivo de las construcciones que articulan; segundo, que propiedades asignadas en la literatura no responden a lacópula, sino a la construcción; tercero, que la delimitación [boundedness] capta más eficientemente las situación de ser/estar, como propiedad semántica diferente y lógicamente distinguible de la perfectividad y telicidad. / Spanish copulas have inspired a vast amount of studies involving a significant number of technical concepts in their description. Against this background, we concentrate on the need to refine the technical parameters used, focusing on the linguistic domains where they are encoded and on the distinction between lexical and constructional semantics. Building on specific tests, we propose that ser and estar: (i) depart from both the standard notion of copula (semantically trivial verb) and of stative verb (lacking temporal structure) and are at least ambiguous as for the eventive type of construction they render; (ii) that many properties observed in the literature do not actually ensue from to the copula per se, but rather from the construction they head; (iii) and that the parameter boundedness best captures their situation, as long as it is conceived as a different semantic property, logically distinguishable from perfectivity telicity.
5

Euclidean N-space

Horner, Donald R. 08 1900 (has links)
This study of the Euclidean N-space looks at some definitions and their characteristics, some comparisons, boundedness and compactness, and transformations and mappings.
6

Cooperative Construction

Wang, Zhongkui 10 September 2009 (has links)
No description available.
7

Boundedness properties of bilinear pseudodifferential operators

Herbert, Jodi January 1900 (has links)
Doctor of Philosophy / Department of Mathematics / Virginia Naibo / Investigations of pseudodifferential operators are useful in a variety of applications. These include finding solutions or estimates of solutions to certain partial differential equations, studying boundedness properties of commutators and paraproducts, and obtaining fractional Leibniz rules. A pseudodifferential operator is given through integration involving the Fourier transform of the arguments and a function called a symbol. Pseudodifferential operators were first studied in the linear case and results were obtained to advance both the theory and applicability of these operators. More recently, significant progress has been made in the study of bilinear, and more generally multilinear, pseudodifferential operators. Of special interest are boundedness properties of bilinear pseudodifferential operators which have been examined in a variety of function spaces. Since determining factors in the boundedness of these operators are connected to properties of the corresponding symbols, significant effort has been directed at categorizing the symbols according to size and decay conditions as well as at establishing the associated symbolic calculus. One such category, the bilinear Hörmander classes, plays a vital role in results concerning the boundedness of bilinear pseudodifferential operators in the setting of Lebesgue spaces in particular. The new results in this work focus on the study of bilinear pseudodifferential operators with symbols in weighted Besov spaces of product type. Unlike the Hörmander classes, symbols in these Besov spaces are not required to possess in finitely many derivatives satisfying size or decay conditions. Even without this much smoothness, boundedness properties on Lebesgue spaces are obtained for bilinear operators with symbols in certain Besov spaces. Important tools in the proofs of these new results include the demonstration of appropriate estimates and the development of a symbolic calculus for some of the Besov spaces along with duality arguments. In addition to the new boundedness results and as a byproduct of studying operators with symbols in Besov spaces, it is possible to quantify the smoothness of the symbols, in terms of the conditions that define the Hörmander classes, that is sufficient for boundedness of the operators in the context of Lebesgue spaces.
8

Keep V-ing : Aspectuality and event structure

Glad, Hanna January 2016 (has links)
The principal aim of this thesis is to provide a comprehensive account of the meaning of keep V-ing constructions, see (1a) and (1b). (1) a. Mary kept winning (again and again). (1) b. John kept running (for another ten minutes). On the basis of a systematic study of combinations of keep with predicates of different aktionsarts, it is shown that keep can give rise to two different readings which share the overall meaning of ‘continued activity’. It is argued that the two readings of keep V-ing arise from different aspectual properties of the predicate in the complement clause. Under the first reading, labelled the continuative-iterative reading, (1a), the event in the complement clause is telic, and the interpretation is an iterative reading. Under the second reading, labelled the continuative reading, (1b), the event in the complement clause is atelic, and the interpretation is a reading of nonstop continuation. It is argued that keep combines with activity predicates in the relevant construction type, that is, with dynamic, durative and atelic events, and that keep has the ability to induce aspect shift when combining with predicates that are not inherent activities. Thus, in (1a), a punctual and telic winning event is iterated, creating a series which in itself is durative and atelic. In (1b), the running event is already durative and atelic. By comparing keep V-ing with the progressive construction be V-ing, (2), and with two other continuative constructions, continue V-ing, (3), and V on, (4), it is shown that keep readily shifts a telic predicate into an atelic reading by taking scope over the entire event, (1a), but cannot take scope over an internal part of a telic event. Both be V-ing, (2), and continue V-ing, (3), are able to take scope over an internal part of a telic event. (2) John was building the house. (3) John continued building the house. (4) John ran on. In addition, unlike continue V-ing and V on, keep V-ing does not necessarily denote continuation of an event which has already been initiated.
9

Global Dynamics Of The Local And Nonlocal Patlak-keller-segel Chemotaxis Systems

January 2014 (has links)
acase@tulane.edu
10

Computationally Aware Control of Cyber-Physical Systems: A Hybrid Model Predictive Control Approach

Zhang, Kun January 2015 (has links)
Cyber-Physical Systems (CPS) are systems of collaborating computational elements controlling physical entities via communication. Such systems involve control processes of physical entities and computational processes. The control complexities originated from the physical dynamics and systematic constraints are difficult for traditional control approaches (e.g., PID control) to handle without an exponential increase in design/test etc. costs. Model predictive control (MPC) predicts and produces optimized control inputs based on its predictive model according to a cost function under given constraints. This control scheme has some attractive features for CPSs: it handles constraints systematically, and generates behavior prediction with respective control inputs simultaneously. However, MPC approaches are computationally intensive, and the computation burden generally grows as a predictive model more closely approximates a nonlinear plant (in order to achieve more accurate behavior). The computational burden of predictive methods can be addressed through model reduction at the cost of higher divergence between prediction and actual behavior. This work introduces a metric called uncontrollable divergence, and proposes a mechanism using the metric to select the model to use in the predictive controller (assuming that a set of predictive models are available). The metric reveals the divergence between predicted and true states caused by return time and model mismatch. More precisely, a map of uncontrollable divergence plotted over the state space gives the criterion to judge where a specific model can outperform others. With this metric and the mechanism, this work designs a controller that switches at runtime among a set of predictive controllers in which respective models are deployed. The resulting controller is a hybrid predictive controller. In addition to design and runtime tools, this work also studies stability conditions for hybrid model predictive controllers in two approaches. One is average dwell time based, and it does not rely on the offline computation that studies the system properties. The other one uses a reference Lyapunov function instead of multiple Lyapunov functions derived from multiple predictive controllers. This approach implicitly depends on the offline numerical solutions of certain systematic properties. The term "boundedness" is preferable in this context since it accepts numerical error and approximations. Two examples, vertical takeoff and landing aerial vehicle control and ground vehicle control, are used to demonstrate the approach of hybrid MPC.

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