• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 187
  • 42
  • 36
  • 23
  • 20
  • 18
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 4
  • 3
  • 2
  • Tagged with
  • 381
  • 156
  • 77
  • 51
  • 46
  • 46
  • 43
  • 40
  • 40
  • 39
  • 39
  • 36
  • 33
  • 33
  • 31
  • 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.
101

Satisficing solutions for multiobjective stochastic linear programming problems

Adeyefa, Segun Adeyemi 06 1900 (has links)
Multiobjective Stochastic Linear Programming is a relevant topic. As a matter of fact, many real life problems ranging from portfolio selection to water resource management may be cast into this framework. There are severe limitations in objectivity in this field due to the simultaneous presence of randomness and conflicting goals. In such a turbulent environment, the mainstay of rational choice does not hold and it is virtually impossible to provide a truly scientific foundation for an optimal decision. In this thesis, we resort to the bounded rationality and chance-constrained principles to define satisficing solutions for Multiobjective Stochastic Linear Programming problems. These solutions are then characterized for the cases of normal, exponential, chi-squared and gamma distributions. Ways for singling out such solutions are discussed and numerical examples provided for the sake of illustration. Extension to the case of fuzzy random coefficients is also carried out. / Decision Sciences
102

Tópicos em condições de otimalidade para otimização não linear / Topics in optimality conditions for nonlinear optimization

Flor, Jose Alberto Ramos 28 January 2016 (has links)
Esta tese é um estudo acerca da análise de convergência de vários métodos numéricos de primeira e de segunda ordem para resolver problemas de programação matemática e as condições de otimalidade associadas. Nossas principais ferramentas são as condições sequenciais de otimalidade. As condições sequenciais de otimalidade oferecem um quadro teórico para a análise de convergência para várias famílias de métodos de primeira ordem sob condições de qualificações fracas. Nesta tese, apresentamos, para cada condição sequencial de otimalidade, a condição de qualificação mínima associada e mostramos as relações com outras condições de qualificação conhecidas. Este fato tem implicações práticas, uma vez que enfraquece as hipóteses requeridas para a convergência de vários métodos numéricos cujos critérios de paradas estão associados às condições sequenciais de otimalidade. Ainda mais, esse tipo de resultado não pode ser melhorado usando outras condições de qualificações. Nós estendemos a noção de condições sequenciais de otimalidade de primeira ordem, para incorporar informações de segunda ordem. Apresentamos, segundo nosso conhecimento, a primeira condição sequencial de otimalidade de segunda ordem, adequada para a análise de convergência de vários métodos numéricos com convergência a pontos estacionários de segunda ordem, como por exemplo métodos baseados no Lagrangeano aumentado, regiões de confiança e SQP regularizado. Associada com a nova condição sequencial de segunda ordem, temos uma nova condição de qualificação, mais fraca que as outras condições de qualificações utilizadas para a análise de convergência para métodos numéricos de segunda ordem. Nós situamos essa nova condição de qualificação com respeito a outras condições de qualificação usadas em análise de convergência. Finalmente apresentamos outra razão pela qual a condição fraca necessária de segunda ordem é a condição de segunda ordem adequada quando lidarmos com a convergência de algoritmos práticos / This thesis deals with the convergence analysis for several rst-and-second-order numerical methods used to solve mathematical programming problems. Our main tools are the sequential optimality conditions. First-order sequential optimality conditions oer a framework to the study of the convergence analysis of several families of rst-order methods, under weak constraint qualications. In this thesis, we will introduce, for each sequential optimality condition the minimal constraint qualications associated with it and we will show their relationships with other constraint qualications. This fact has a practical aspect, since, we improve the convergence analysis of practical methods with stopping criteria associated with sequential optimality conditions. This results can not be improved by using another weak constraint qualications. We will extend the notion of rst-order sequential optimality conditions to incorporate secondorder information. We will introduce, to the best of our knowledge, the rst second-order sequential optimality condition, suitable to the study of the convergence analysis of several second-order methods including methods based on the augmented lagrangian, trust-region and regularized SQP. Associated with the second-order sequential optimality condition, we have a new constraint qualication weaker than all constraint qualications used for the convergence analysis of second-order methods. We show the relationships of this new constraint qualications with other constraint qualications used for algorithmic purposes. We will also present a new reason why the weak secondorder necessary condition is the natural second-order condition when we are dealing with practical numerical methods
103

Tópicos em condições de otimalidade para otimização não linear / Topics in optimality conditions for nonlinear optimization

Jose Alberto Ramos Flor 28 January 2016 (has links)
Esta tese é um estudo acerca da análise de convergência de vários métodos numéricos de primeira e de segunda ordem para resolver problemas de programação matemática e as condições de otimalidade associadas. Nossas principais ferramentas são as condições sequenciais de otimalidade. As condições sequenciais de otimalidade oferecem um quadro teórico para a análise de convergência para várias famílias de métodos de primeira ordem sob condições de qualificações fracas. Nesta tese, apresentamos, para cada condição sequencial de otimalidade, a condição de qualificação mínima associada e mostramos as relações com outras condições de qualificação conhecidas. Este fato tem implicações práticas, uma vez que enfraquece as hipóteses requeridas para a convergência de vários métodos numéricos cujos critérios de paradas estão associados às condições sequenciais de otimalidade. Ainda mais, esse tipo de resultado não pode ser melhorado usando outras condições de qualificações. Nós estendemos a noção de condições sequenciais de otimalidade de primeira ordem, para incorporar informações de segunda ordem. Apresentamos, segundo nosso conhecimento, a primeira condição sequencial de otimalidade de segunda ordem, adequada para a análise de convergência de vários métodos numéricos com convergência a pontos estacionários de segunda ordem, como por exemplo métodos baseados no Lagrangeano aumentado, regiões de confiança e SQP regularizado. Associada com a nova condição sequencial de segunda ordem, temos uma nova condição de qualificação, mais fraca que as outras condições de qualificações utilizadas para a análise de convergência para métodos numéricos de segunda ordem. Nós situamos essa nova condição de qualificação com respeito a outras condições de qualificação usadas em análise de convergência. Finalmente apresentamos outra razão pela qual a condição fraca necessária de segunda ordem é a condição de segunda ordem adequada quando lidarmos com a convergência de algoritmos práticos / This thesis deals with the convergence analysis for several rst-and-second-order numerical methods used to solve mathematical programming problems. Our main tools are the sequential optimality conditions. First-order sequential optimality conditions oer a framework to the study of the convergence analysis of several families of rst-order methods, under weak constraint qualications. In this thesis, we will introduce, for each sequential optimality condition the minimal constraint qualications associated with it and we will show their relationships with other constraint qualications. This fact has a practical aspect, since, we improve the convergence analysis of practical methods with stopping criteria associated with sequential optimality conditions. This results can not be improved by using another weak constraint qualications. We will extend the notion of rst-order sequential optimality conditions to incorporate secondorder information. We will introduce, to the best of our knowledge, the rst second-order sequential optimality condition, suitable to the study of the convergence analysis of several second-order methods including methods based on the augmented lagrangian, trust-region and regularized SQP. Associated with the second-order sequential optimality condition, we have a new constraint qualication weaker than all constraint qualications used for the convergence analysis of second-order methods. We show the relationships of this new constraint qualications with other constraint qualications used for algorithmic purposes. We will also present a new reason why the weak secondorder necessary condition is the natural second-order condition when we are dealing with practical numerical methods
104

Nominální sufixální derivace v předklasické francouzštině / The nominal suffixal derivation in pre-classical French

Štichauer, Jaroslav January 2012 (has links)
The present PhD thesis deals with nominal suffixal derivation in pre-classical French (about 1550-1610). Based both on traditional data collection and on available digital corpuses, especially Frantext, it first strives to define basic concepts such as language standard, problems of periodization, productivity, lexicalization, paradigmatization, panchronic validity of word-formation rules etc. On selected derivational patterns, it also tests the operationality of Optimality theory (OT) and other mechanisms (i.a. paradigmatization) in diachronic perspective. In several follow-up chapters, it then analyzes, from a diachronic point of view, a number of suffixes (-age, -aison, -ance, - ment, etc.).
105

A-最適試驗處理與對照處理比較之Diallel Crosses實驗 / Families of A-Optimal Diallel Crosses for Test versus Control Comparisons

徐永豐, Hsu, Yung-Feng Unknown Date (has links)
Diallel cross experiments for comparing p test lines with a control in the set up of block designs and completely randomized designs are investigated. Complete diallel crosses including all p(p+1)/2 distinct crosses are considered. Families of A-optimal and efficient type S0 block designs for p=2,3, and for p>=4, k=2 are obtained, and the construction methods are given. For p>=k>=3, and p>=4, a sufficient condition for type S0 block designs with the control line appearing tb times, where t>=1 is an integer, to be A-optimal is obtained, and families of A-optimal type S0 block designs are provided. The A-optimality of type S designs under the model of completely randomized designs when 2<=p<=6 is also tudied, and some examples are given.
106

Expanding Archaeological Approaches to Ground Stone: Modeling Manufacturing Costs, Analyzing Absorbed Organic Residues, and Exploring Social Dimensions of Milling Tools

Buonasera, Tammy Yvonne January 2012 (has links)
Although ground stone artifacts comprise a substantial portion of the archaeological record, their use as an important source of information about the past has remained underdeveloped. This is especially true for milling tools (mortars, pestles, grinding slabs and handstones) used by hunter-gatherers. Three studies that apply novel techniques and approaches to prehistoric milling technology are presented here. Together they demonstrate that substantial opportunities exist for new avenues of inquiry in the study of these artifacts. The first combines a simple optimization model from behavioral ecology with experimental data to weigh manufacturing costs against gains in grinding efficiency for mobile hunter-gatherers. Results run counter to widespread assumptions that mobile hunter-gatherers should not spend time shaping grinding surfaces on milling tools. Next, gas chromatography-mass spectrometry (GC-MS) is used to analyze lipid preservation in modified rock features in dry caves at Gila Cliff Dwellings National Monument, New Mexico. A high concentration of lipids, derived from processing a seed resource, was recovered from a grinding surface in these caves. The lipid content in this surface is comparable to amounts recovered from select pottery sherds that have been used for radiocarbon dating. The third study uses synchronic and diachronic variability in morphology, use-wear, and symbolic content to analyze ground stone milling tools from mortuary contexts in the San Francisco Bay Area of California. Archaeological and ethnographic evidence supports the inferred association of certain mortars with feasting and ritual activities. Differences in the representation of some of these forms in male and female graves may reflect changes in the roles of women and men in community ritual and politics.
107

Gradience in grammar : experimental and computational aspects of degrees of grammaticality

Keller, Frank January 2001 (has links)
This thesis deals with gradience in grammar, i.e., with the fact that some linguistic structures are not fully acceptable or unacceptable, but receive gradient linguistic judgments. The importance of gradient data for linguistic theory has been recognized at least since Chomsky's Logical Structure of Linguistic Theory. However, systematic empirical studies of gradience are largely absent, and none of the major theoretical frameworks is designed to account for gradient data. The present thesis addresses both questions. In the experimental part of the thesis (Chapters 3-5), we present a set of magnitude estimation experiments investigating gradience in grammar. The experiments deal with unaccusativity/unergativity, extraction, binding, word order, and gapping. They cover all major modules of syntactic theory, and draw on data from three languages (English, German, and Greek). In the theoretical part of thesis (Chapters 6 and 7), we use these experimental results to motivate a model of gradience in grammar. This model is a variant of Optimality Theory, and explains gradience in terms of the competition of ranked, violable linguistic constraints. The experimental studies in this thesis deliver two main results. First, they demonstrate that an experimental investigation of gradient phenomena can advance linguistic theory by uncovering acceptability distinctions that have gone unnoticed in the theoretical literature. An experimental approach can also settle data disputes that result from the informal data collection techniques typically employed in theoretical linguistics, which are not well-suited to investigate the behavior of gradient linguistic data. Second, we identify a set of general properties of gradient data that seem to be valid for a wide range of syntactic phenomena and across languages. (a) Linguistic constraints are ranked, in the sense that some constraint violations lead to a greater degree of unacceptability than others. (b) Constraint violations are cumulative, i.e., the degree of unacceptability of a structure increases with the number of constraints it violates. (c) Two constraint types can be distinguished experimentally: soft constraints lead to mild unacceptability when violated, while hard constraint violations trigger serious unacceptability. (d) The hard/soft distinction can be diagnosed by testing for effects from the linguistic context; context effects only occur for soft constraints; hard constraints are immune to contextual variation. (e) The soft/hard distinction is crosslinguistically stable. In the theoretical part of the thesis, we develop a model of gradient grammaticality that borrows central concepts from Optimality Theory, a competition-based grammatical framework. We propose an extension, Linear Optimality Theory, motivated by our experimental results on constraint ranking and the cumulativity of violations. The core assumption of our model is that the relative grammaticality of a structure is determined by the weighted sum of the violations it incurs. We show that the parameters of the model (the constraint weights), can be estimated using the least square method, a standard model fitting algorithm. Furthermore, we prove that standard Optimality Theory is a special case of Linear Optimality Theory. To test the validity of Linear Optimality Theory, we use it to model data from the experimental part of the thesis, including data on extraction, gapping, and word order. For all data sets, a high model fit is obtained and it is demonstrated that the model's predictions generalize to unseen data. On a theoretical level, our modeling results show that certain properties of gradient data (the hard/soft distinction, context effects, and crosslinguistic effects) do not have to be stipulated, but follow from core assumptions of Linear Optimality Theory.
108

Distributed Computational Methods for Energy Management in Smart Grids

Mohammadi, Javad 01 September 2016 (has links)
It is expected that the grid of the future differs from the current system by the increased integration of distributed generation, distributed storage, demand response, power electronics, and communications and sensing technologies. The consequence is that the physical structure of the system becomes significantly more distributed. The existing centralized control structure is not suitable any more to operate such a highly distributed system. This thesis is dedicated to providing a promising solution to a class of energy management problems in power systems with a high penetration of distributed resources. This class includes optimal dispatch problems such as optimal power flow, security constrained optimal dispatch, optimal power flow control and coordinated plug-in electric vehicles charging. Our fully distributed algorithm not only handles the computational complexity of the problem, but also provides a more practical solution for these problems in the emerging smart grid environment. This distributed framework is based on iteratively solving in a distributed fashion the first order optimality conditions associated with the optimization formulations. A multi-agent viewpoint of the power system is adopted, in which at each iteration, every network agent updates a few local variables through simple computations, and exchanges information with neighboring agents. Our proposed distributed solution is based on the consensus+innovations framework, in which the consensus term enforces agreement among agents while the innovations updates ensure that local constraints are satisfied.
109

Towards a computer model of the historical phonology and morphology of Latin

Roberts, Philip J. January 2012 (has links)
Research projects in Optimality Theory tend to take a synchronic view of a particular generalisation, and set their standards for rigour in typological terms (see for example Suzuki 1998 on dissimilation, Crosswhite 2001 on vowel reduction). The goal of this thesis is to use Stratal OT to take a diachronic view of multiple generalisations within the morpho-phonology of one language, namely Latin, with the principal empirical aim of producing an analysis that is demonstrably true to all the attested facts of the generalisations in question. To that end, I have written PyOT, a computer program implementing the OT calculus and a theory of phonological representations, which I use in this work to model the histories of Lachmann’s Law, rhotacism and the phonologically conditioned allomorphy of the -alis/aris- suffix as active generalisations within the phonological component of the grammar. Appendix A gives the results of the computer model applied to a dataset consisting of 185 attested Latin forms, which suffice to illustrate the exact conditions of the generalisations in question. I show that producing a complete analysis of the three generalisations I have chosen to model entails analysis of other generalisations that interact with them, including the treatment of the Indo-European voiced aspirates in Latin (which interacts with rhotacism), and reduplication in forming perfect stems (which interacts with Lachmann’s Law). Constraint rankings sufficient to model these interactions, and consistent with the general conditions of the interacting generalisations have been included in the model. The intention is for this work to illustrate both the utility of formal phonological theory in advancing hypotheses within historical-comparative linguistics, and the potential of PyOT as a tool for producing Optimality-Theoretic models of (eventually) a language’s entire phonology.
110

Regularities in the Augmentation of Fractional Factorial Designs

Kessel, Lisa 03 May 2013 (has links)
Two-level factorial experiments are widely used in experimental design because they are simple to construct and interpret while also being efficient. However, full factorial designs for many factors can quickly become inefficient, time consuming, or expensive and therefore fractional factorial designs are sometimes preferable since they provide information on effects of interest and can be performed in fewer experimental runs. The disadvantage of using these designs is that when using fewer experimental runs, information about effects of interest is sometimes lost. Although there are methods for selecting fractional designs so that the number of runs is minimized while the amount of information provided is maximized, sometimes the design must be augmented with a follow-up experiment to resolve ambiguities. Using a fractional factorial design augmented with an optimal follow-up design allows for many factors to be studied using only a small number of additional experimental runs, compared to the full factorial design, without a loss in the amount of information that can be gained about the effects of interest. This thesis looks at discovering regularities in the number of follow-up runs that are needed to estimate all aliased effects in the model of interest for 4-, 5-, 6-, and 7-factor resolution III and IV fractional factorial experiments. From this research it was determined that for all of the resolution IV designs, four or fewer (typically three) augmented runs would estimate all of the aliased effects in the model of interest. In comparison, all of the resolution III designs required seven or eight follow-up runs to estimate all of the aliased effects of interest. It was determined that D-optimal follow-up experiments were significantly better with respect to run size economy versus fold-over and semi-foldover designs for (i) resolution IV designs and (ii) designs with larger run sizes.

Page generated in 0.0667 seconds