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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.
241

Structural Disjoining Potential of Grain Boundary Premelting in Aluminum-Magnesium via Monte Carlo Simulations

Power, Tara C. January 2013 (has links)
<p>Premelting is the formation of a thin, thermodynamically stable, liquid-like film at an interface for temperatures below the equilibrium melting temperature. Using a Monte Carlo technique, the underlying short range structural forces for premelting at the grain boundary can be directly calculated. This technique is applied to a (i) Σ9 ⟨115⟩ 120<sup>o</sup> twist boundary and a (ii) Σ9 ⟨011⟩ {411} symmetric tilt boundary in an embedded atom model of Aluminum-Magnesium alloy. Both grain boundaries exhibit disordered structures near the melting point that depend on the concentration of Magnesium. The behavior is described quantitatively with sharp interface thermodynamics, involving an interfacial free energy that depends on width of the grain boundary, referred to as the disjoining potential. The disjoining potential calculated for boundary (i) displays a decreasing exponential dependence on width of the grain boundary, while the disjoining potential of (ii) features a weak attractive minimum. This work is discussed in relation to a previous study using pure Nickel, results of which can be useful to the theoretical study of thermodynamic forces underlying grain boundary premelting in an alloy.</p> / Master of Science (MSc)
242

Model-Free Variable Selection For Two Groups of Variables

Alothman, Ahmad January 2018 (has links)
In this dissertation we introduce two variable selection procedures for multivariate responses. Our procedures are based on sufficient dimension reduction concepts and are model-free. In the first procedure we consider the dual marginal coordinate hypotheses, where the role of the predictor and the response is not important. Motivated by canonical correlation analysis (CCA), we propose a CCA-based test for the dual marginal coordinate hypotheses, and devise a joint backward selection algorithm for dual model-free variable selection. The second procedure is based on ordinary least squares (OLS). We derive and study the asymptotic properties of the OLS-based test under the normality assumption of the predictors as well as an asymmetry assumption. When these assumptions are violated, the asymptotic test with elliptical trimming and clustering is still valid with desirable numerical performances. A backward selection algorithm for the predictor is also provided for the OLS-based test. The performances of the proposed tests and the variable selection procedures are evaluated through synthetic examples and a real data analysis. / Statistics
243

LTL over EL Axioms

Borgwardt, Stefan, Thost, Veronika 20 June 2022 (has links)
Aus der Einleitung: Description Logics (DLs) [BCM+07] are popular knowledge representation formalisms, mainly because they are the basis of the standardized OWL 2 Direct Semantics, their expressiveness can be tailored to the application at hand, and many optimized reasoning systems are available.
244

Conjunctive Query Answering in Rough EL

Peñaloza, Rafael, Thost, Veronika, Turhan, Anni-Yasmin 20 June 2022 (has links)
Rough Description Logics have recently been studied as a means for representing and reasoning with imprecise knowledge. Real-world applications need to exploit reasoning over such knowledge in an efficient way. We describe how the combined approach to query answering can be extended to the rough setting. In particular, we extend both the canonical model and the rewriting procedure such that rough queries over rough EL ontologies can be answered by considering this information alone.
245

Generalized eigenvalue problem and systems of differential equations: Application to half-space problems for discrete velocity models

Esinoye, Hannah Abosede January 2024 (has links)
In this thesis, we study the relationship between the generalized eigenvalue problem (GEP) $Ax=\lambda Bx$, and systems of differential equations. We examine both the Jordan canonical form and Kronecker's canonical form (KCF). The first part of this work provides an introduction to the fundamentals of generalized eigenvalue problems and methods for solving this problem. We discuss the QZ algorithm, which can be used to determine the generalized eigenvalues and also how it can be implemented on MATLAB with the built in function 'eig'.  One essential facet of this work is the exploration of symmetric matrix pencils, which arise when A and B are both symmetric matrices. Furthermore we discuss discrete velocity models (DVMs) focusing specifically on a 12-velocity model on the plane. The results obtained are then applied to half-space problems for discrete velocity models, with a focus on planar stationary systems.
246

Expanding the Genetic Code of Mammalian Cells to Probe and Manipulate Protein Function:

Osgood, Arianna January 2024 (has links)
Thesis advisor: Abhishek Chatterjee / The study of protein structure and function has advanced significantly with the development of genetic code expansion (GCE) technology for the incorporation of noncanonical amino acids (ncAAs), revolutionizing synthetic biology by enabling the introduction of novel functionalities into proteins. Within eukaryotic systems, these advancements have paved the way for deeper investigations into complex protein functions critical to human biology and have spurred the development of innovative biotherapeutic solutions.The work described within this dissertation has aimed to further advance various applications of mammalian GCE. This includes the construction of next-generation homogenous antibody-drug conjugates (ADCs) both using a genetically encoded photocaged cysteine and with a dual incorporation system for the construction of a dual-drug conjugate. Multiple new platforms were developed for the incorporation of two or even three ncAAs within a single protein, utilizing a novel aaRS/tRNA pair and evolved hyper-efficient tRNAs. GCE-enabled precise protein modification was also utilized to spectroscopically study the conformational dynamics of dimeric EGFR. Additionally, platforms were established for the precise installation of post-translational modification (PTM) mimics within mammalian proteins, allowing for their programmed activation. Finally, an innovative strategy for the study of protein-protein interactions using genetically encoded photocrosslinkers was developed. Collectively, these efforts have contributed to the development of novel tools for studying protein function in mammalian cells and advancing the creation of new biotherapeutics through GCE technology. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
247

Waveform Description Language (WDL) for Software Radios

Prill, Robert, Comba, Andrew 10 1900 (has links)
International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / Waveform Description Language (WDL) was invented to ease the process of porting legacy and/ or new radio waveforms to Programmable / Software Radios. WDL has two primary requirements; 1st it is to provide a rigorous executable behavioural description of waveform signal structures that is unambiguous and yet independent of any particular end item software radio architecture. The 2nd requirement is that the behavioural specification provides a path to automatic code generation for GP’s, DSP’s, and FPFG’s and that the Generated code be tested against the behavioural model.
248

PCA and CVA biplots : a study of their underlying theory and quality measures

Brand, Hilmarie 03 1900 (has links)
Thesis (MComm)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The main topics of study in this thesis are the Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA) biplots, with the primary focus falling on the quality measures associated with these biplots. A detailed study of different routes along which PCA and CVA can be derived precedes the study of the PCA biplot and CVA biplot respectively. Different perspectives on PCA and CVA highlight different aspects of the theory that underlie PCA and CVA biplots respectively and so contribute to a more solid understanding of these biplots and their interpretation. PCA is studied via the routes followed by Pearson (1901) and Hotelling (1933). CVA is studied from the perspectives of Linear Discriminant Analysis, Canonical Correlation Analysis as well as a two-step approach introduced in Gower et al. (2011). The close relationship between CVA and Multivariate Analysis of Variance (MANOVA) also receives some attention. An explanation of the construction of the PCA biplot is provided subsequent to the study of PCA. Thereafter follows an in depth investigation of quality measures of the PCA biplot as well as the relationships between these quality measures. Specific attention is given to the effect of standardisation on the PCA biplot and its quality measures. Following the study of CVA is an explanation of the construction of the weighted CVA biplot as well as two different unweighted CVA biplots based on the two-step approach to CVA. Specific attention is given to the effect of accounting for group sizes in the construction of the CVA biplot on the representation of the group structure underlying a data set. It was found that larger groups tend to be better separated from other groups in the weighted CVA biplot than in the corresponding unweighted CVA biplots. Similarly it was found that smaller groups tend to be separated to a greater extent from other groups in the unweighted CVA biplots than in the corresponding weighted CVA biplot. A detailed investigation of previously defined quality measures of the CVA biplot follows the study of the CVA biplot. It was found that the accuracy with which the group centroids of larger groups are approximated in the weighted CVA biplot is usually higher than that in the corresponding unweighted CVA biplots. Three new quality measures that assess that accuracy of the Pythagorean distances in the CVA biplot are also defined. These quality measures assess the accuracy of the Pythagorean distances between the group centroids, the Pythagorean distances between the individual samples and the Pythagorean distances between the individual samples and group centroids in the CVA biplot respectively. / AFRIKAANSE OPSOMMING: Die hoofonderwerpe van studie in hierdie tesis is die Hoofkomponent Analise (HKA) bistipping asook die Kanoniese Veranderlike Analise (KVA) bistipping met die primêre fokus op die kwaliteitsmaatstawwe wat daarmee geassosieer word. ’n Gedetailleerde studie van verskillende roetes waarlangs HKA en KVA afgelei kan word, gaan die studie van die HKA en KVA bistippings respektiewelik vooraf. Verskillende perspektiewe op HKA en KVA belig verskillende aspekte van die teorie wat onderliggend is tot die HKA en KVA bistippings respektiewelik en dra sodoende by tot ’n meer breedvoerige begrip van hierdie bistippings en hulle interpretasies. HKA word bestudeer volgens die roetes wat gevolg is deur Pearson (1901) en Hotelling (1933). KVA word bestudeer vanuit die perspektiewe van Linieêre Diskriminantanalise, Kanoniese Korrelasie-analise sowel as ’n twee-stap-benadering soos voorgestel in Gower et al. (2011). Die noue verwantskap tussen KVA en Meerveranderlike Analise van Variansie (MANOVA) kry ook aandag. ’n Verduideliking van die konstruksie van die HKA bistipping word voorsien na afloop van die studie van HKA. Daarna volg ’n indiepte-ondersoek van die HKA bistipping kwaliteitsmaatstawwe sowel as die onderlinge verhoudings tussen hierdie kwaliteitsmaatstawe. Spesifieke aandag word gegee aan die effek van die standaardisasie op die HKA bistipping en sy kwaliteitsmaatstawe. Opvolgend op die studie van KVA is ’n verduideliking van die konstruksie van die geweegde KVA bistipping sowel as twee veskillende ongeweegde KVA bistippings gebaseer op die twee-stap-benadering tot KVA. Spesifieke aandag word gegee aan die effek wat die inagneming van die groepsgroottes in die konstruksie van die KVA bistipping op die voorstelling van die groepstruktuur onderliggend aan ’n datastel het. Daar is gevind dat groter groepe beter geskei is van ander groepe in die geweegde KVA bistipping as in die oorstemmende ongeweegde KVA bistipping. Soortgelyk daaraan is gevind dat kleiner groepe tot ’n groter mate geskei is van ander groepe in die ongeweegde KVA bistipping as in die oorstemmende geweegde KVA bistipping. ’n Gedetailleerde ondersoek van voorheen gedefinieerde kwaliteitsmaatstawe van die KVA bistipping volg op die studie van die KVA bistipping. Daar is gevind dat die akkuraatheid waarmee die groepsgemiddeldes van groter groepe benader word in die geweegde KVA bistipping, gewoonlik hoër is as in die ooreenstemmende ongeweegde KVA bistippings. Drie nuwe kwaliteitsmaatstawe wat die akkuraatheid van die Pythagoras-afstande in die KVA bistipping meet, word gedefinieer. Hierdie kwaliteitsmaatstawe beskryf onderskeidelik die akkuraatheid van die voorstelling van die Pythagoras-afstande tussen die groepsgemiddeldes, die Pythagoras-afstande tussen die individuele observasies en die Pythagoras-afstande tussen die individuele observasies en groepsgemiddeldes in die KVA bistipping.
249

時間序列模型建立之各種分析方法之比較與實證研究

徐瑞玲, XU, RUI-LING Unknown Date (has links)
時間數列分析自一九七0年Box-Jenkins 發展出自我迴歸移動平均整合模式(簡稱A RIMA(p,d,q))建立法後,便更普遍地應用於經濟、企管、工程及物理等 相關領域上。但利用Box-Jenkins 的鑑定方法一般只對MA或AR模型有效,而對混 合的ARMA模型則不適用。其後陸續有統計學者提出不同的鑑定方法,但都無法有 效地決定P、d、q階數。 直至一九八四年以後,Tsay和Tiao兩位學者才又提出了一套有效的鑑定法則,利用擴 展的樣本自我相關函數(Extended Sample Autocorrelation Function)或正規分析 (Canonical Analysis)求出的最小正規相關係數(The Smallest Canonical Corr- elation )做為鑑定p、d、q的準則。這兩種方法的優點皆為可直接處理平穩或非 平穩型時間數列,而不用事先決定差分的階數,而且對混合ARIMA模型亦有效。 對於有異常點(Outlier )存在的時間數列,其可能由於某些外在的介入因素所引起 ,而ARIMA模型對資料的配適是不足夠的。因此該如何發現異常點的存在及加入 合理的介入模式亦構成了模型鑑定的問題。本文除對Tsay和Tiao的方法做一說明外, 亦利用其鑑定方法對存在有異常點的時間數列做一分析,並由實證研究探討其對季節 模型的鑑定效果。
250

Use of Geographic Information System and Remote Sensing Technologies to Describe Mosquito Population Dynamics in the Ray Roberts Greenbelt, Denton County, Texas

Bolling, Bethany G. 05 1900 (has links)
A population survey was conducted from April through September 2002 on mosquito species occurring on the Ray Roberts Greenbelt, a riparian corridor used for public recreation on the Elm Fork of the Trinity River, in Denton County, Texas. ArcGIS software was used to set up a stratified random sampling design based on habitat parameters. Multivariate analyses of sampling data and climatic variables were used to describe spatial and temporal patterns of mosquito species. A total of 33 species were collected during this study belonging to the following genera: Aedes, Anopheles, Coquillettidia, Culex, Mansonia, Ochlerotatus, Orthopodomyia, Psorophora, Toxorhynchites, and Uranotaenia. Seasonal distributions of the dominant species revealed population fluctuations. Aedes vexans was the primary species collected in April and May, occurring in low numbers throughout the rest of the sampling period. Psorophora columbiae reached its highest population density in June, with a smaller peak occurring in late July. Present from May through the end of September, Culex erraticus was the most abundant species collected with major peaks in mid-June and the end of July. Abundance of Culex salinarius followed the same general trend as that for Cx. erraticus, but with smaller numbers. The specimens were tested for a variety of arboviruses by the Texas Department of Health. One pool of Cx. erraticus and Cx. salinarius, collected in August 2002, tested positive for West Nile virus. Variables that were important factors for determining dominant species abundance were temperature, wind speed, rain accumulation occurring one-week and two-weeks prior to sampling, number of day since last rain event, dew point, and average canopy coverage.

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